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Wireless Solutions TechZone Magazine, March 2011 - Digi-Key

1. Automated 250 175 Electric Gas Water Total 39 52 33 40 Figure 3 North American AMR Penetration Source IMS Meter Report 2007 Edition leverage their existing metering assets to provide customer energy management services verified demand response measurements or view coincidental load across a set of meters for load forecasting purposes While this clearly is not a Smart Metering platform it does facilitate a suite of services consistent with many Smart Grid business cases In addition products are available that convert these AMR devices to industry standard protocols such as the ZigBee Smart Energy Profile This minimizes stranded asset risk by connecting these ERT modules to a wide range of certified Smart Energy devices presenting a smooth migration from the world of AMR to the Smart Grid Figure 4 Consumer engagement with Smart Energy devices The industry will continue to develop and expand the use cases enabled by these new technologies but providing tools that can provide flexible deployments that can future proof the distribution grid are essential in driving early technology adoption These AMR gateways are made possible by leveraging machine to machine management services that connect the utilities applications consumer energy management portal Demand Response platform etc with their customers metering device a key development in making this technology commercially viable Respondin
2. Did You Know Actress Hedy Lamarr and composer George Antheil together patented frequency hopping technology in 1942 that was the basis for modern spread spectrum communication technology used in WiFi and in some cordless and wireless telephones wa TECHZOnNe Microcontrollers and Wireless Connectivity in Smart Appliances Wireless connectivity is enabling smarter appliances that can communicate with other devices throughout the home and over the Internet Choose the right wireless protocol and you re off to a good start The days of the drab household appliance that sits mostly idle in the corner of a kitchen or bathroom have come to an end Today s appliances are sleek functional designs that are innovative and form the centerpieces of most modern day homes One of the technological trends in appliance design that has gained a significant foothold in recent years is the smart appliance These devices sport leading edge technologies including the ability to communicate wirelessly with other devices throughout the home and over the Web Smart appliance manufacturers see tremendous economic Opportunities in directly communicating not only with appliances in the field but also with the users of those appliances Services such as remote diagnostics and firmware upgrades can be made more seamless to the user Consumers also stand to gain economically by removing the cost and obstacle of rewiring their homes thro
3. Many manufacturers have avoided making their products wireless because of uncertainty over the approval and certification process While it is true that RF increases the effort and cost of bringing a product to market it also can add significantly to the function and salability of a completed product Thanks to a growing number of easily applied radio frequency RF devices such as those offered by Linx manufacturers are now able to quickly and reliably add wireless functionality to their products The issue of legal compliance for the finished product is straightforward when approached in logical steps Purpose of this article This article gives a brief overview of the legal issues governing the manufacture and sale of RF products intended for unlicensed operation in the United States under CFR 47 Part 15 In the United States the Federal Communications Commission FCC is responsible for the regulation of all RF devices The FCC requires any device that radiates RF energy to be tested for compliance with FCC rules These rules are contained in the Code of Federal Regulations CFR Title 47 Part 15 is the section of the code that deals with devices that emit RF energy and are to be operated without an individual license While this article will provide you with a basic understanding of the steps involved in certification it is strongly recommended that you obtain a full copy of the code from your local government bookstore the Governme
4. 200 mV DIV 5s DIV l Figure 6 Operation during input source interruption The basic design procedure outlined above is applicable to other types of energy harvesting transducers Power management circuits that interface with piezo elements high voltage AC electromagnetic coil magnet and photovoltaic solar cells are all readily available today In all cases it is necessary to first determine the average load power required to see if autonomous operation is feasible Summary Average load power is the key variable to consider when contemplating the use of energy harvesting techniques to supplement or replace batteries in remote wireless sensor networks The operating environment will always dictate what types of energy harvesting transducers are suitable and average load power will further narrow the choices Power management solutions are now available to bridge the gap between low output power level transducers and ultra low power microcontrollers sensors and RF links With all of the necessary elements in place semi or fully autonomous remote sensor networks have left the theoretical realm and are now poised to enter the mainstream The LTC3108 The Missing Link for Energy Harvesting Linear Technology Corporation Linear Tech s LTC3108 is the missing link in energy harvesting The Step Up DC DC regulator features a 20 mV resonant boost topology and an LTC proprietary compound depletion mode The circuit s
5. e Coupling between the GSM antenna and the GPS antenna reduces the efficiency of both radio systems GSM transmissions may swamp the GPS front end LNA creating harmonics and other problems Wideband noise from the GSM PA may desensitize the GPS receiver The close proximity of other components such as batteries may affect the performance of both radio systems The space available for the GPS antenna may not be suitable for the best signal reception With tracking devices the orientation of the device in use is unknown and so an antenna pattern that is aS omni directional as possible is required There will always be one location for the antenna that is best for omni directional coverage but this position may not be available because of the ID of the device and the layout of all the other components This is less of a problem on larger platforms The solution to these issues lies in careful system design and a good understanding of antennas Coupling between the GSM GPS radios and antennas for example may be minimized by mounting them on opposite sides of a PCB A blocking filter before the GPS LNA and a second one after it can prevent the GSM transmissions affecting the GPS system Figure 1 shows a module on which we have identified the main GPS and GSM components Combining the radio and antenna is particularly useful for the GPS system where the radio and antenna are roughly the same size and can be manufactured as a single r
6. Wl r4ial T ZW111 CA Understanding Antenna Specifications Page 10 SMART HOME M2M Connectivity Page 25 By p ji and Operation FEATURED WIRELESS SOLUTION SUPPLIERS MD SEO CORPORATION Amphenol ANALOG DEVICES antenova a Haves ASSVANN AIMEL EB austriamicrosystems LVvaGO TECHNOLOGIES JANIA BIBULGIN C MAX RF Technology Specialist connectBlue The strongest connection in a wireless world d a Ty Ty M DLP Design ember pea ee Johnson a J EPCOS a ae ree FAIRCHILD SEMICONDUCTOR ELECTRONIC Wy Ng rs freescale semiconauctor HIROSE ELECTRIC CO LTD Cinfineon inter il TECHN Kallman iealion 4 beg pe ila iaa Laird TECHNOLOGIES Inno e Te si ology vativ for a Connected World L TECHNOLOGY L TECHNOLOGIES FALA MAKI IVI INNOVATION DELIVERED Microelectronic Integrated Systems MICREL ation Through Technology AN MICROCHIP Multi eci ystems National Semiconductor J NAVMAN WIRELESS California Eastern Laboratories anasonic Electronic Components 2 Pulse TECHNITROL COMPANY RIM RFMD BREAKTHROUGH SIMPLICITY TAIYO YUDEN i TDK 13 TEXAS INSTRUMENTS TOIREX Tyco Electronics SS a O WURTH ELEKTRONIK TM DighKe uy Magazine WIRELESS SOLUTIONS TZ
7. EE Times Distribution Study August 2009 Offering more than 1 7 million products from more than 440 quality name brand manufacturers Digi Key s commitment to inventory is unparalleled Access to the company s broad product offering is available 24 7 at Digi Key s top rated website www digikey ca Wireless TechZone Q amp A In the rapidly evolving wireless market it seems as if there is something new every day technologies products consumer trends or regulations Time to market demands have never been greater with the design of many of today s new wireless products requiring expertise in more than one discipline You have questions We have answers On target to field more than 260 000 calls this year our technical support Specialists are available 24 7 365 to answer your questions and assist you with your wireless needs If you have a question we invite you to contact our technical staff via telephone live web chat or by emailing your question to techzone digikey com What network topologies are supported by ZigBee There are three different network topologies that are supported by ZigBee namely the star mesh and cluster tree or hybrid networks Each has its own advantages and can be used to advantage in different situations The star network is commonly used having the advantage of simplicity As the name suggests it is formed in a star configuration with outlying nodes communicating with a cent
8. RAL i MH AMH ihih 2 Ra AMI MH ii Mi H RAIN RAI 1M AMH AMH DEL Figure 2 In the 2 4 GHz band Bluetooth low energy technology uses 40 channels instead of the 79 channels used in Classic Bluetooth Three channels which are located exactly between the Wireless LAN channels are used for device discovery and connection setup Bluetooth low energy technology has a very secure AES 128 encryption algorithm and a distributed encryption key procedure x Coexistence eo A ee A ge ile Bluetooth Wireless LAN IEEE 802 15 4 ZigBee Wireless HART and Ta en sags atria AO a many proprietary radios use the unlicensed 2 4 GHz ISM Industrial OY i ga a ra s Scientific Medical band Therefore in order to get a robust and Scan ner reliable communication it is essential for many wireless technologies to make a time consuming and accurate frequency planning However Bluetooth technology has already solved these issues thanks to its built in adaptive frequency hopping feature and high Figure 4 An advertiser periodically sends and will always act as a slave when it tolerance for interference is connecting A scanner is waiting for an advertisement and is always a master when connecting TD Te chZ ne 58 Software structure In Bluetooth low energy technology the state and attributes are key terms All parameters have a condition available that is provided by the server in a protocol attribute for the client All attribu
9. and monitoring and access control where they are sometimes also referred to as Real Time Location Systems Up to now most implementations of long range RFID have used an Ultra High Frequency UHF reader operating in the 915 MHz frequency band combined with passive tags Passive tags which have no autonomous power source generate their energy from the electromagnetic radiation emitted by the reader and communicate with the reader by changing their impedance backscattering As a result passive tags have a limited range Some RFID systems however are required to operate in environments that are challenging to RF transmissions such as in deep mines inside metal shipping containers and inside buildings with walls made of masonry Achieving robust and reliable transmission with passive RFID systems is difficult when the radio signal must travel through obstructions such as rock liquid masonry or metal For such applications system developers must use an active RFID system in which the tag includes its own battery power source This enables the active transmission back to the reader of high power UHF signals which can consistently achieve a longer range than a passive tag can provide Base station Active Tag Battery a LF Downlink pg T A 2 X UHF Uplink Figure 1 A system block diagram of an active tag 48 A fundamental role in active RFID systems Figure 1 is played by a low
10. counterpoise internally Designing with a quarter wave monopole antenna A common pitfall for designers new to the wireless arena is the implementation of the ground plane As stated earlier the ground plane is the other half of the antenna so it is critical to the final performance of the product This means that it is critical to get it right The ground plane is a solid copper fill on one layer of the circuit board that is connected to the negative terminal of the battery This fill not only acts as the antenna s counterpoise but is also the ground connection for all of the components on the board The problems arise when components are added and the traces routed to connect them It is a very rare and simple design that does not need to route a trace on more than one layer Every trace that gets routed on the same layer as the ground plane can have a significant impact on the RF performance It is best to look at the board from the perspective of the antenna connection The goal is to have a low impedance path back to the battery or power connection This is accomplished with wide unobstructed paths If the ground plane is cut up with traces through hole components or vias then it will not be able to do its job as an antenna counterpoise One of the worst things that can happen is for the ground plane to get so cut up that it has to get connected by jumping back and forth between layers through vias A via is associated with inducta
11. ji i aan i E E T TSR g Mair Search J nar aa SS ae oP a Mas imaz etl Digeeelincast Gort pr been Sentai Rede tl ote mi m Teir 7 i lj ne Bil E d F k 2 f j hat d f 1 Ei Bex oes plen af E3 Sap wa m Tow Eales 1 ME Y pe Pa i a a ee a z iat epee e Featured products from leading suppliers oi e Application notes references designs PTMs exclusive editorial e Parametric search tools and more eA Text Paper Contains 10 Post Consumer Fiber Yaw Please Recycle Digh Kay CORPORATION www digikey ca techzones 2011 Digi Key Corporation 701 Brooks Ave South Thief River Falls MN 56701 USA
12. requiroments of Pom 6 0 ap pompis w Figure 1 The Part 15 approval process 12 50 gt 11 250 4 10 000 6 aoe 3 750 Allowable Field Strength pen 3m anad 1 250 M a 60 275 260 305 0 m5 280 35 m 35 410 a25 ig 455 470 418 433 Fundamental Frequency Available Linx Module Frequincins Figure 2 Frequency of operation versus output power capable of producing non compliant output levels This extra power helps designers overcome inefficient antenna styles and allows them to take advantage of the FCC s averaging allowance when modulation techniques such as ASK OOK are employed If the module is matched to an efficient antenna the output power may need to be reduced using the module s level adjust or an external attenuation pad For further details review Linx Application Note 00150 In addition to fundamental output power restrictions the FCC also regulates allowed harmonic levels and occupied bandwidth 53 Since this article is oriented toward users of Linx products little detail is needed on these points as Linx modules are designed to meet these requirements It is important however to note that there are ways in which a user can adversely affect harmonic content including the use of a poorly matched or tuned antenna supply system noise or layout or bypass issues While these considerations of legality may appear formidable they generally are not By
13. sensor to respond to a physical event such as a door opening it ae a operation and transmit a data packet Measurement units Three measurement units are used to develop the sensor battery life calculations uC uA and mAh Per Table 1 radio and sensor events are expressed in either pA or uC depending on whether steady state current was being measured pA or the current associated with an event of a specific time interval was being determined uC The overall lithium battery capacity is expressed in mAh The events measured in coulombs can easily be converted to mAh One coulomb C equals one amp second As A coulomb represents the number of electrons that flow through a circuit at one amp of current each second For example if each data poll is 200 uC and the event happens one time per second the average current is 200 pA Battery technology Security sensors manufactured by iControl are powered by CR2 lithium batteries To accurately calculate the battery life of a device powered by lithium batteries both self discharge and internal resistance must be accounted for The total number of electrons that a www digikey ca wireless 21 battery can move through a circuit is known as its capacity measured in mAh While this capacity is fixed the battery life varies based on the operations the battery powers self discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of
14. 5 Mbps are supported which make it suitable for control and monitoring applications Embedded Wi Fi operates in the universally available 2 4 GHz spectrum This spectrum is an open and unlicensed frequency band and as a consequence is being used by other wireless technologies Another wireless option available to manufacturers is ZigBee While Embedded Wi Fi operates at data rates on the order of Mbps ZigBee has a specified maximum data rate of 250 kbps per the IEEE 802 15 4 radio standard ZigBee positions itself as the low power and low data rate wireless protocol of choice for wireless sensor networks ZigBee enabled smart appliances can be made to operate with extremely low power while utilizing inexpensive microcontrollers such as Microchip s PIC microcontrollers with eXtreme Low Power XLP technology Other ZigBee strengths include its strong data security model interoperability and its expanding adoption across many application segments Similar to Wi Fi ZigBee operates within the 2 4 GHz frequency band utilizing sixteen defined channels giving it flexibility in terms of channel hopping and frequency agility in order to avoid noise and interference As evidenced by its partnerships with both the Wi Fi Alliance and HomePlug Consortium the ZigBee Alliance is continuing to strengthen its interoperability credentials ZigBee along with Wi Fi have gained acceptance as viable networking technologies of choice for the U S based Sm
15. Other key trends driving the adoption of Smart Grid technologies include e More efficient management of power on the grid Power capacity continues to be outpaced by increases in power consumption Building new power sources is extremely expensive and something the utility companies want to postpone for as long as possible The alternative is to better manage the peak power load This can be accomplished through various load shedding and demand response programs for example today consumers receive a rebate or price break if they allow their utility company to control their thermostat during peak usage times Bringing power awareness to consumers through visibility For most people power consumption is a single number that arrives once a month in the mail It is difficult to attempt to be more responsible with one s usage when one has no idea when or how power is being used By providing real time visibility into home and business usage patterns consumers can actively analyze and reduce their consumption Enabling appliances to monitor their usage and support remote management For consumers to have access to energy information it first has to be collected While many power meters now track usage and time of day they can only see aggregate power consumption see Figure 1 As particular appliances are not being tracked a consumer cannot tell if a usage spike is coming from a refrigerator hot tub dryer or A C unit Figure 1 With
16. Where a straight antenna may have a bandwidth of 100 MHz a helical may only have a bandwidth of 10 MHz This becomes more pronounced as the frequency gets lower since the coils typically get closer together to maintain a specific overall length i e _ as z gt i keii _ pemi eii Figure 3 916 MHz L and 315 MHz R Helical Antennas Antenna specifications lf antennas are the least understood RF component then antenna specifications are the least understood of all RF components For instance many designers look for radiated test data without really understanding what they are looking at or how it relates to the performance of their product For this reason let s examine the most common antenna specifications Impedance The impedance of an antenna is the real resistance and imaginary reactance that appears at the terminals of the antenna Because there are inductive and capacitive elements to an antenna this will change with frequency It will also be affected by objects that are nearby such as other antennas the components on a circuit board and even the user of the device An antenna will have two types of resistance associated with it Radiation resistance converts electrical power into radiation Ohmic resistance is loss on the antenna s structure that converts electrical power into heat The radiation resistance should be much higher than the ohmic resistance though
17. also allows the production of reliable Received Signal Strength Indicator RSSI measurements RSSI information can be useful in some applications as it provides an estimate of the distance between the tag and the base station LF Wake up Receiver Figure 4 A three dimensional orthogonal antenna array inside an active tag The architecture described above can reliably meet the required low average current draw however only on the assumption that the UHF transmitter is almost permanently in power down This means that the wake up receiver must be able to reject false wake up calls generated by noise or disturbance Implementing a code or pattern generation capability in the interrogator and a pattern recognition capability in the receiver solves this problem Active tag performance in practice Typically active tags use single coin batteries of around 200 mAh capacity and the minimum expected lifetime is three years This implies an average total current draw of approximately 7 6 pA Assuming that on average half of the current is used by the UHF transmitter the wake up receiver can draw a maximum current of 3 8 pA The main constraint on the range of the system is the sensitivity of the wake up receiver A sophisticated LF wake up receiver should offer sensitivity of at least 100 uV Active tags offer very robust performance even in hostile environments the low frequencies used can penetrate even extremely thick walls Th
18. both are important to the antenna s efficiency Generally the radiation resistance at the terminals of a dipole antenna in free space isolated from anything conductive is 73 ohms A monopole antenna will be half of this or 36 5 ohms The reactance is power that is stored in the near field of the antenna This reactance combined with the real resistance make up the antenna s impedance Both values are affected by objects in the near field and will vary down the antenna s length The specifics of this are beyond the scope of this article but can be found in most antenna literature These values are important because in any system maximum power transfer will occur when the source and load impedances match If they are different called a mismatch then some of the power sent to the antenna will be reflected back into the load or lost as heat This will lower the efficiency of the system lowering range increasing power requirements and shortening battery life Industry convention for RF is an impedance of 50 ohms Most IC manufacturers will have matched their products to 50 ohms or will provide a circuit designed to match their product to a 50 ohm load Likewise antenna manufacturers frequently design and characterized antennas at 50 ohms VSWR The Voltage Standing Wave Ratio VSWR is a measurement of how well an antenna is matched to a source impedance typically 50 ohms It is calculated by measuring the voltage wave that is he
19. broken into two quarter wave lengths called elements The elements are set at 180 degrees from each other and fed from the middle This type of antenna is called a center fed half wave dipole and shortens the antenna length by half ta TechZOne HALF WAVE DIPOLE ANTENNA HERTZ ee Figure 1 A Half Wave Dipole Antenna A method for making the antenna even smaller is to use one of the quarter wave elements of a dipole and allow the ground plane on the product s PCB to serve as a counterpoise in essence creating the other quarter wave element Since most devices have a circuit board anyway using it for half of the antenna can make a lot of sense Generally this half of the antenna will be connected to ground and the transmitter or receiver will reference it accordingly This style is called a quarter wave monopole and is the most common antenna in today s portable devices VERTICAL 2 4 GROUNDED ANTENNA MARCONI Poroce 4 ELEMENT GROUND i PLANE 7 VIRTUAL 34 jA DIPOLE Figure 2 A Quarter Wave Monopole Antenna Another way to reduce the size of the antenna is to coil the element This is where the straight wire is coiled or wrapped around a non conductive substrate to create what is called a helical element This has the advantage of making the overall length shorter but it will also reduce the antenna s bandwidth Like an inductor the tighter the coil and the higher the Q the smaller the bandwidth
20. dedicated ASK protocol software the TDA5051A delivers robust performance even in noisy environments When combined with the NXP Cortex M0 microcontroller LPC1114 the TDA5051A enables a wide range of home control applications NXP supports the TDA5051A with a lighting control demo kit that can easily be configured for other home control applications em TeCchZOne KwiQMAte Series Connectors Emerson s KwiQMAte series designed for higher density packaging situations Emerson Network Power Connectivity Solutions offers the Johnson product line of KwiQMAte connectors that feature a push on style interface Traditional SMA plugs need to be configured with extra space allowance for torque wrench coupling procedures The KwiQMAte connectors are designed for higher density packaging situations with the push pull connector interface allowing for more connectors per application Connector bodies are offered with a tri alloy as a standard finish with gold plated contacts Emerson s KwiQMAte connectors are fully intermateable with existing QMA connectors p aaa aii a a EMERSON Johnson www digikey ca emerson wireless Connect to Digi Key Like Never Before www digikey ca connect You z J Digi Key s Mobile Applications With instant access to www digikey ca you can view more than 500 000 board level components in stock and our online offering of facebook See us on YouTube more than 1 7 m
21. distribution framework These capabilities will need to exist for devices in the substation down the feeders at the metering points and even into the extended grid inside a home or business A second observation is that the value is not defined by the device but rather by the business application utilizing this communication and control capability In other words these capabilities drive benefits whether this is a new asset or an investment that was made five years ago The benefits are almost universally defined by business functions rather than the device itself Once this is recognized it is much easier to evaluate technology gaps that need to be filled These gaps tend not to be specific devices or protocol but rather a machine to machine management platform that can easily connect these devices to the appropriate business applications Making the right decisions at this level will drive accelerated deployments of Smart Grid technologies that can leverage distribution equipment both new and old As stated earlier it is estimated that over 200 billion will be invested globally in the Smart Grid by 2013 but the existing grid assets far exceed this number Is it possible to enhance these solutions to make them more viable in supporting bi directional communications control and generation services Can the utility and rate payers achieve an 38 ma TeCHZONe Figure 2 Value derives from business functions not devices ad
22. frequency LF receiver which wakes up the system and triggers a UHF transmission This article examines recent enhancements in LF receiver design that reduce power consumption while improving receiver performance promising to widen the range of applications in which active RFID systems can be implemented The principal challenge for the designer of active RFID tags is achieving both very long battery life and long range two requirements that at first sight seem to be in conflict with one another At the same time tags must fit a small form factor so achieving long battery life by use of a large battery is not a viable option These constraints explain why the system architecture shown in Figure 1 has evolved The interrogator base station is made up of an LF transmitter and a UHF receiver while the tag consists of an LF wake up receiver and a UHF transmitter The interrogator transmits periodically typically once a second an LF pattern After the transmission the UHF receiver is switched on to check for replies from tags At the tag only the wake up receiver is active in normal operation whenever the tag is within the interrogator s range the receiver wakes up the UHF transmitter uplink on detection of a pattern that it recognizes Only then does the UHF transmitter transmit the information required to unambiguously identify the tag to the interrogator This architecture allows the UHF radio to stay in power down mode almost co
23. has two halves such as with a dipole antenna With a typical tracker antenna arrangement the antenna must be very small as many other components must fit inside the tracker box In effect the PCB is the main radiating component and its lack of length becomes critical What can be done about this problem One solution is to extend the PCB groundplane outside the box as part of any external features such as the strap on a watch based tracker or the collar on a pet tracker Even a loop on the end of the tracker for attaching a cord can make a useful difference to the antenna performance If no external features are available it is worth considering using a balanced dipole like structure having two antenna arms because it may be possible to get them a long way apart by attaching them to the inside of the box at opposite ends This distance can be greater than that between a single antenna and the PCB Constraints and tradeoffs The designer of portable tracking devices is trapped in a space with three types of boundaries One boundary is the laws of physics that limit how effective a small antenna can be there is not much that can be done about this except to make use of good engineering practice and experience Another boundary is cost because trackers must often be inexpensive devices engineering for cost reduction is an established and effective art but it does not increase the designer s options The third restriction is formed by
24. in theory the ground plane of the device can be smaller Flexible circuit antenna FXP14 e Can be mounted to the inner plastic housing of the device e Minimum clearance of 20 mm from metal in all directions e Mount at right angles perpendicular to any main board e Cable should be shorter than 150 mm but not less than 80 mm e Place antenna away from noise activity sources m ay Figure 3 Flexible circuit antenna FXP14 TD TechZ ne PIFA on housing e Dimensions approximately 60 mm x 20 mm x 10 mm e 20 mm clearance to metal e Spring contact can be used for connection Figure 4 PIFA on housing Rigid PCB FR4 Antenna PC 30 e Can be mounted to the inner plastic housing of the device e Minimum clearance of 20 mm from metal in all directions e Mount at right angles perpendicular to any main board e Cable should be shorter than 150 mm but not less than 80 mm e Place antenna away from noise activity sources aoga Figure 5 Rigid PCB FR4 Antenna PC 30 PTCRB For cellular wireless products sold in the USA Canada and other regions it is necessary to apply for PTCRB approval from the CTIA wireless association A designated lab will test your product to establish if it meets the requirements PTCRB itself does not set minimum pass fail standards for TRP TIS but there is a strict RSE standard higher than the traditional FCC test standard So you can actually pass RSE and get P
25. may request a sample of the product to confirm ongoing FCC compliance Consideration for operation within the 260 470 MHz band Introduction This section is designed to give the reader a basic understanding of the legal and technical considerations for operation of RF devices in the 260 470 MHz band within the United States The use of these frequency bands varies considerably worldwide so it should be recognized that this application note is intended for designers utilizing Linx RF modules and planning to operate in the United States When working with RF a clear distinction should always be made between what is technically possible and what is legally acceptable Achieving a solution that meets technical objectives but cannot be legally sold or operated serves little use As such issues of legality should be given high priority Legal considerations In the United States the Federal Communications Commission FCC is responsible for the regulation of all RF devices These regulations are contained in the Code of Federal Regulations CFR Title 47 Title 47 is made up of numerous volumes however all regulations applicable to operation in the 260 470 MHz band are contained in volume 0 19 It is strongly recommended that a copy be obtained and reviewed in its entirety You can get a full copy of the code from your local government bookstore the Government Printing office in Washington or the FCC website What is unlicensed operatio
26. no spinning wheel smart meters can track usage and time of day However they are limited to measuring only aggregate power usage unless appliances support intelligent power tracking and self monitoring 34 ma TeCHZONe e Sharing of energy information throughout the home and beyond When users can track power usage throughout their home they can make wiser choices i e shift time of usage to when lower pricing tiers are in place Two primary hurdles exist how to share information throughout the home and how to get this information out onto the Internet cloud Managing the increasing load as electric vehicles come onto the grid Electric vehicles require a great deal of power and most drivers will plug their cars in when they return home from work The problem is one on the neighborhood level the presence of several vehicles simultaneously charging on the same transformer could create many problems for the utility companies Rather than upgrade equipment charging load can be spread across the evening when usage tends to be lowest Tracking and self monitoring Accurately tracking power usage and patterns requires that energy consumption be measured at the appliance itself Metrology ICs step down appliance current to measure energy consumption and provide this information to the appliance s main processor One of the primary cost drivers of metrology devices is how much accuracy is required For some devices like the smart m
27. polarized multipath channels Even if in this example node 1 changes its position a similar behavior is observed if the environment changes and the two nodes are at a fixed position 24 Network Performance Measurements A measurement illustrating the node to node performance using the packet error rate PER is shown in Figure 10 The result consists of three individual measurements 1 Use ANTO only 2 Use ANT1 only 3 AD algorithm enabled left antenna right antenna auto decision When using Antenna Diversity there are three possible scenarios for two antennas 1 Both antennas behave different One antenna with a good signal quality PER 0 The other does not receive PER gt 1 2 Both antennas provide a good signal quality PER 0 3 Both antennas do not receive PER 1 Figure 10 Antenna Diversity Validation Results The measurement result in Figure 10 shows that for scenarios of type 1 when one antenna is receiving while the other one doesn t the resulting PER is still at an acceptable low level when using the AD algorithm lf both antennas provide a sufficient high signal quality scenario 2 the Antenna Diversity can not improve the link quality further Only if both antennas do not receive anything also Antenna Diversity can t provide better results scenario type 3 Conclusion In environments with distinctive multipath scenarios or varying propagation conditions the applic
28. powered devices like fitness sensors watches health care entertainment and mobile accessories easily implemented creating a seamless data chain from sensors to the Web www digikey ca panasonic wireless www digikey ca wireless 3 Merging Legacy Systems and the Smart Grid It is becoming increasingly clear that the Smart Grid is not defined by NEW devices but rather by the services enabled by adding secure and reliable two way communications to as many points on the distribution grid as possible The Smart Grid is a term that is now recognized by a broad range of people that have never worked at a utility or related business There are stock indices following businesses developing products and services that enhance the grid continual legislation focused on investment and research in energy generation and distribution and an increasing recognition that the way people view and manage their energy usage in the future will be dramatically different from today These factors are driving many analysts to predict more than 200 billion will be invested in new grid technologies between 2008 and 2013 with over 53 billion in the U S alone Source Pike Research These new investments cover a broad range of products and services but virtually all are focused on enabling enhanced monitoring and control across the electrical distribution network This includes capturing more granular information related to power quality consump
29. programs used to implement features The module is 14 pages in length and can be viewed with or without audio in ten minutes RABBIT gt T M otne On Demand www digikey ca ptm 40 gas than in the middle of the day hence my costs environmental and economical are much higher than if I try to shift my driving patterns The same is true for energy consumption If use electricity during the electrical rush hour the cost to the utility is significantly higher yet in most cases they are unable to pass that extra cost on to the consumer The Smart Grid is the first broad reaching initiative enabling utilities to better map costs to price which in turn will strengthen support and adoption of time based rate structures This will greatly increase the need for energy dashboard tools communicating rate and consumption data to consumers and will rapidly expand the number of people actively participating in load shifting programs Once again these challenges do not define a specific networking technology but rather an information and control ecosystem that will utilize many networks both wired and wireless to promote an interactive reliable and efficient energy delivery grid Selecting a software service that allows your applications to operate independent from the communication network will maximize the utility s ability to leverage existing assets while helping to future proof the investments
30. security oages 34 37 7 The 902MHz 928MHz band is highly favorable due to minimal ___ 8 Universal IP modems use the Universal Keep Alive function Some cellular network providers automatically disable devices that have been idle for a certain period of time a practice that might make sense for handsets but is inappropriate for embedded devices This function ensures that the network sees that the modem is still active Conclusion The mobile handset is the world s highest volume OEM market and the cellular chipset business is therefore skewed towards the needs of fewer than 20 global manufacturers By abstracting the IP stack out of the chipset and into a processor under its own control Multi Tech s Universal IP provides a way to address the application needs and product lifecycles of the thousands of embedded OEMs that need devices to access the internet via cellular networks or other media ma TeECHZOne Trivia Try your hand at the TechZone Wireless crossword puzzle Each answer can be found in this issue s articles page numbers are located after each clue Answers are posted on page 66 2 by mounting them on opposite sides of a PCB pages 17 19 energy data can be used to determine what people do in their houses privacy as well as whether or not they are _ restrictions and excellent propagation characteristics oages 50 56 pinout so embedded developers can swap one modem for another with
31. that prevent them from effectively conveying information about all of the devices within a home One approach is to support access to a PC or smart phone which can provide full configuration and Ul functionality over a wireless link Ideally consumers would like to have remote access to energy information requiring that information be passed out to the Internet cloud This approach however requires that information be collected on a back end server Supporting such a server potentially introduces additional complexity and expense to appliance design In addition to be the most useful to consumers energy information for the entire home needs to consolidated onto a single management platform so that consumers don t have to manually track individual devices Consolidating energy savings is also likely to improve consumer responsiveness to energy conservation For example a dryer stating that it saves 5 month may not impress consumers as much as seeing that overall home savings are 40 month ma TecHZOne Some utility and energy monitor companies have chosen to use Google PowerMeter as an alternative to investing in building their own energy management platform Google PowerMeter supports consumers and businesses either directly through their utility company or through a gateway device that can be purchased separately As a standardized platform Google PowerMeter will potentially facilitate a smoother transition to consumer energy awarene
32. the wariness of manufacturers to integrate Smart Grid technology into their appliances is understandable since there is no clear target yet at which to aim Most appliances have an extended lifetime and providing a dead end implementation can damage a brand Regardless of the technology used appliances will need to be able to operate when connectivity is disrupted Ideally appliances will track time on their own and be able to call up the last energy rate profile received They may also be able to forecast demand response events to warn users during potentially expensive time slots These are important considerations as well since it is the appliance manufacturers who will be held responsible for the robustness of energy management systems Consolidation One of the major design considerations for utilities and manufacturers is managing and consolidating the flow of energy information Moving from a single data point per month to several data points per half hour represents a tremendous amount of data to collect and correlate AS more appliances incorporate displays they will be able to provide an accounting of their own consumption However much of the value of energy tracking comes from being able to coordinate all of the appliances in a home or business from a central point While a thermostat smart meter or central energy monitor can serve as the data gateway for connected appliances these devices may have limited display capabilities
33. the internet is always Universal IP not the moving target presented by the module manufacturers Figure 3 Basic architecture of a typical cellular module and architecture of a Multi Tech modem with Universal IP showing the discrete processor hosting the IP stack tm TechZOn e The stack communicates with the user system over a serial interface The operation of the stack is controlled through a set of simple AT commands that will be familiar to anyone who has designed with modems In fact this suggests two meanings to the word universal in Universal IP universal across all modems that run the Universal IP stack but also universally applicable by embedded designers since any microcontroller with a serial interface can issue AT commands and the AT instruction set is at least almost universally recognized by embedded developers The architecture of Universal IP products with their discrete processor also enables Multi Tech to implement an IP stack with features suited to embedded users For instance Multi Tech implements an Auto Connect function in its Universal IP modems should the device drop off the network it will automatically attempt to re connect without human intervention The stack can also be configured to periodically input traffic to a cellular network the 1 4 10 ACROSS 3 Coupling between the GSM and GPS radios and antennas for example may be 5 The ability to track data raises many currently home
34. tight limitations and application restrictions the FCC places on some other bands In this band virtually any analog or digital signal can be sent without restrictions on content or duration Second higher legal output power allows the potential for much longer transmission distances Third the propagation of frequencies in the 900 MHz range is better than at higher frequencies such as 2 4 GHz Therefore lower output power is needed to attain any particular distance reducing transmitter power consumption Fourth is antenna size and compactness A useful byproduct of higher frequency is shorter wavelength This allows a 1 4 wave antenna in the 900 MHz range to typically be less than 3 25 inches in length In fact Linx s Antenna Factor division offers tiny surface mount antennas that are less than 0 65 inches in length allowing for easy concealment in compact portable products Drawbacks to the 902 928 MHz band The first drawback is the band s popularity good in rock and roll bad in RF Products such as cordless phones have migrated to higher frequencies but the growth of wireless and the benefits of the band make it likely to remain crowded Second is the potential for higher level interferers In addition to its allocation for narrow band devices the 902 928 MHz frequency range is also allocated for higher power devices While Linx employs a variety of techniques to minimize the possible impact of such interference it shou
35. to have the best chance at approval it is important to explain the intended function of the product and any special Operating characteristics to test lab personnel If you are using a module that uses a keyed modulation method such as ASK OOK be sure your lab remembers to measure or calculate average power not peak www digikey ca wireless 51 The test lab will require a number of items to complete the filing These items will often include e A letter appointing the test lab as your technical agent for certification The labs will provide a sample letter e The FCC ID Number of the unit The first three digits are the grantee code obtained earlier The last 14 digits are up to the applicant e A sketch of the location of the FCC label on your unit as well as a sketch with dimensions of the label itself e A block diagram of the unit showing all clock oscillators and their frequencies of operation The signal path and frequency should be shown at each block e Full schematic diagram e The user s manual e A brief non technical description of the product and its operation e A product sample for testing and photos Transmitter testing A product containing a Linx transmitter is considered by the FCC to be an intentional radiator because it intentionally emits RF energy into free space Thus it must be tested and certified before it may be marketed Certified transmitters are required to have two labels attached an F
36. way Self monitoring also enables more granular control Rather than supporting only control of weekday or weekend settings to keep programming complexity low smart thermostats see Figure 2 can allow consumers to program more complex schedules or even analyze power usage to determine if someone is currently in the house or building Friday March 12 2010 2 00 pm DUTDOOR 72 12 Kurniity INDOOR ga 69 Lit 45 Humidity Figure 2 Smart thermostats allow intelligent management of heating and air conditioning systems such as allowing utility companies to adjust usage during peak demand periods Designers also need to take into account the fact that some appliances need to be managed with more grace than simply being shut down For example consider a washer that is shut down mid cycle as part of a demand response event Unless the meter can also tell the washer to turn itself back on the clothes will sit in water for hours Preferably the washer could drain before shutting off The washer should also have a bleach indicator so that the washer can decline to shut down to prevent clothes from being destroyed in the hours it takes a consumer to return home Alternatively a person may be cleaning a shirt for an important meeting and needs to be able to override the demand response mechanism These are the sorts of issues manufacturers need to anticipate Connection Part of the philosophy behind tracking power usage in rea
37. we decided to use a TEG TEGs utilize the Seebeck effect to generate a voltage across their output terminals when exposed to a temperature differential see Figure 2 CERAMIC SUBSTRATE 3 P TYPE eee SEMICONDUCTOR e s PELLETS CONDUCTOR N TYPE TABS SEMICONDUCTOR POSITIVE PELLETS Figure 2 Typical TEG 62 100 mV DIV 20 mA DIV 10 ms DIV Figure 3 Typical Current pulse during measure and transmit cycle 100 mV DIV 20 mA DIV 2S DIV ripple during measure and transmit cycles Figure 4 V OUT To further our example let s assume that a 50 mm TEG is selected One side of the TEG will be mounted to the HVAC duct in the ceiling and the other side exposed to room temperature air Since TEGs have a very low thermal resistance it s often challenging to develop a suitable AT across them so the room temperature side will employ a heat sink Our measurements have shown that the HVAC duct surface will average 38 C in the winter heating and 12 C in the summer cooling with an average room temperature ambient of 25 C Through careful measurements we ve determined that the AT across the TEG is 10 C when mounted to the duct with a heat sink From the manufacturer s data sheet we can see that the TEG V with a 10 C dT is 180 mV The TEG Output Resistance R is 2 5 Q The maximum power available to the load occurs when the TEG Ry Power Converter or load R If we assume that our
38. with ZigBee firmware were used for wireless communication to the device sensors and gateway The initial sensor board was designed around a Microchip PIC18F14K22 microcontroller and a VTI temperature pressure sensor both of which are housed in a sealed Bud box with an IP65 rating Solar panels from Parallax and sealed lead acid batteries from B B Battery and Panasonic were also used to develop the Digi Key Weather Center Digi Key Design Support Services team members Steve Dahl Kevin Culkins Shawn Rhen Brandon Tougas and Scott Raeker created the weather station with each person assigned to different parts and stages of development The project began with the design and construction of the structure that would hold the solar panel control box and sensor nodes Once the structure was completed it was determined that sealed lead acid batteries and a charging circuit would be needed for power storage and distribution to the sensor nodes The initial nodes developed for the project were a temperature pressure sensor and a PWM controller enabled with a ZigBee module that relays the information to and from an Ethernet gateway Next python drivers were developed for the gateway which relayed and Digi Kay h managed the data to and from the sensor nodes Finally applications were developed for Android and Blackberry in order to present the data Internet connectivity is quickly becoming more ubiquitous in our everyday l
39. 0 0074 Total Power P 3 3 V 500 uA 3 3 V x 003 3 3 V 03 110 6 mW Average Power P D P 0 0074 x 0 1106 818 uA Pa or average power is the key term that will tell us what types of energy harvesting transducers if any will be suitable for this system Table 2 lists some typical energy transducers and the typical average power they are capable of delivering The column labeled K is a power conversion constant that takes into account the type of power management block that is required to convert the transducer energy to a usable voltage 3 3 V in this case A perfect power converter has a K 1 K will vary with the type of transducer employed Generally speaking K is proportional to the output voltage of the transducer Since very low output voltage transducers like TEGs require an extremely high boost ratio and correspondingly high input currents K tends to be lower than very high output voltage transducers like piezo elements In the previous example we can see that the average power required P is approaching the upper range of piezo transducers of a reasonable size but is within the capabilities of TEGs and photovoltaic PV transducers or solar cells The system environment will usually dictate what type of transducer is selected In our example we cannot depend on an always available light source so PV transducers are not practical We are at the upper end of what is feasible for piezo transducers so
40. 26 e Merging Legacy Systems and the Smart Grid an article on adding secure and reliable two way communications by Dave Mayne from Digi International page 38 We ve expanded our supplier base in recent months to include Dresden Elektronic Atmel based ZigBee 802 15 4 modules and kits Laird Technologies antennas and Taoglas embedded and external M2M antennas Digi Key represents over 100 industry leading manufacturers of wireless products Our expansive range of products will support your entire M2M communications design and production needs Worldwide demand is accelerating in the M2M space with a clear movement toward real time communication and endless applications extending way beyond automotive We believe that the information and insights in this issue of JechZone magazine will support your next generation product ideas and solutions sincerely Maud q Mark Zack Director Semiconductor Digi Key Corporation www digikey ca wireless About Digi Key Corporation As one of the world s fastest growing distributors of electronic components Digi Key Corporation has earned its reputation as an industry leader through its total commitment to service and performance As a full service provider of both prototype design and production quantities of electronic components Digi Key has been ranked 1 for Overall Performance for 18 consecutive years from among the nation s more than 200 distributors
41. C rules These rules are contained in the Code of Federal Regulations CFR Title 47 The first volume of CFR 47 contains parts 0 19 The sections you will be dealing with throughout the approval process are primarily Part 2 and Part 15 Part 2 deals with issues of marking and authorization Part 15 deals with the operational aspects and requirements for devices that emit RF energy and are to be operated without the end user needing a license It is strongly recommended that you obtain a full copy of the code from your local government bookstore the Government Printing office or the FCC website Issues such as frequency selection antenna compliance and output power are covered elsewhere therefore this section moves past those issues to the specific steps involved in the approval process Step one lab selection The FCC requires that final product testing be conducted by a registered testing facility Labs that have indicated they are available to perform Part 15 testing for the public are listed on the Domestic Testing Facilities list The quality and competence of labs varies widely Labs appearing on the list are independent Linx is pleased to make recommendations of test facilities believed to be competent however it is the sole responsibility of applicants to select a test lab capable of measuring their specific device To pay or not to pay Once you have chosen a lab you must decide the extent of the services they will prov
42. CC ID label and a compliance label The FCC ID label identifies the FCC equipment authorization file associated with the transmitter while the compliance label indicates to the consumer that the transmitter may not cause nor is it protected from harmful interference These labels may be combined for convenience Receiver declaration of conformity A receiver is considered an unintentional radiator because while not specifically designed to radiate RF energy RF radiation may occur For this reason the receiver must be tested and authorized by a Declaration of Conformity DoC In this simple process an accredited laboratory tests the product to ensure compliance with FCC standards An FCC filing or submittal is not required unless specifically requested pursuant to Section 2 1076 The test results should be maintained within the applicant s files Conforming products are also required to have a compliance label attached to all items subsequently manufactured or marketed by the responsible party Filing confidentiality Filing for confidentiality is an important and often overlooked issue Unless otherwise requested the entire contents of your filing will become public information You may request confidentiality pursuant to 47 CFR 0 459 which can prevent such proprietary items as schematic diagrams from falling into the hands of competitors When confidentiality is requested please label all items that are to be kept confidential from
43. FCC and no affiliation between Linx and the FCC is meant to be inferred tex TechZOne Bluetooth Low Energy for Wireless Sensors and Actuators There are many wireless protocol options for low power wireless sensor networks but none are better suited to the task than Bluetooth low energy Wireless solutions are used in a variety of demanding industrial applications Technologies such as Wireless LAN Classic Bluetooth IEEE 802 15 4 ZigBee and Wireless HART all provide specific characteristics and are therefore suitable for different applications and specific demands However none of these technologies offer an optimal solution for a wireless connection for sensors and actuators in manufacturing automation In these types of applications the existing technologies are too expensive too slow or consume too much energy The solution lacks a fast robust low energy transmission for wireless sensors and actuators This is where Bluetooth low energy technology comes into play Table 1 A comparison of Bluetooth low energy wireless technology and other wireless technologies used in the manufacturing industry ZigBee IEEE 802 15 4 Not so Good Bluetooth low energy Not so Good Parameter Bluetooth Wireless LAN Data Throughput Moderate Very Good Moderate Moderate 90 300 m Robustness Very Good 50 1000 m Very Good Range 75m mesh 10 300 m Local system density Not so Good Very Good Moderate Ve
44. Inc ications are enabling a whole new range of smart article discusses some of the challenges involved in and the trade offs that are involved when choosing nologies to use in creating them ple Cost Effective oa h to Home Automation cc00 sscccsessccceeseenes manuel T Nana NXP Semiconductors Achieving RF Performance and Approvals ccsssee 7 by Dermot O Shea Taoglas Achieving reliable reception in a handheld wireless device is challenging at best This article explains how to define your performance targets how to design or select an antenna system capable of meeting them and then how to determine whether or not you have Antenna Design for Portable Tracking Devices 0 17 by Simon Kingsley Antenova Low cost portable tracking devices are growing in popularity and will find an ever increasing role in protecting people and property It is not easy to design the radios in these devices but integrated antenna RF modules can overcome most of the challenges AVR2021 AT86RF231 Antenna Diversity 0csssseee 20 contributed by Atmel Corporation Antenna diversity results in better reception especially in the presence of multipath interference without requiring an increase in transmit power or additional pre amplification This article explains how it works and how to implement it Low Frequency Radio in Active RFID Systems 05 48 by Ruggero Le
45. SM capability with CDMA On this model profitability depends on maintaining a stable core platform and re using as much application code as possible across every product variant Now the scenario for implementing a protocol stack described above begins to look flawed The problem arises when a new product variant requires a new protocol stack implementation and this can happen in all three dimensions e Time chipset manufacturers are driven by the short product lifecycles of handset manufacturers not the large market windows that embedded OEMs address Older chipsets are regularly made obsolete and replaced with new chipsets and for each replacement the chipset supplier creates a new IP stack implementation Market segments a low end product extension might require a cost reduction from a high speed connection to a low speed connection Replacing a high specification module with a lower cost alternative might entail implementing a new IP stack Geographies as above different regions of the world run different cellular technologies Replacing a GSM module with a CDMA module might again entail implementing a new cellular module with a new IP stack Each new IP stack will require developers to write new application code to control it Development of this new application code potentially requires the designer to learn a new set of commands each time and to work out how to use a new API Even if the embedded OEM uses the
46. TCRB even with compromised device performance if TRP and TIS are not considered Individual operators may specify their own TRP TIS test standards and even more tests before they will accept your device on their network Taoglas can assist wireless device designers in meeting these approvals first time around Disclaimer RF design is inherently difficult Taoglas provides this article as a reference only and cannot be held responsible for errors or omissions in this information or for the performance of devices that use this above information Users are advised to discuss with a Taoglas representative for a formal solution proposal before proceeding on any design ATmega128RFAtT Wireless MCU Atmel Atmel s Almegal28RFA1 Wireless MCU is the world s first wireless AVR and consists of a unique Atmel microcontroller and RF transceiver The device is designed for industrial and consumer IEEE 802 15 4 ZigBee 6LOWPAN RF4CE and high data rate 2 4 GHz ISM brand applications This product training module reviews the power specifications and data encryption offered with the series covers the data rates and onboard Hardware Accelerator and provides specific application examples The module is 28 pages long and can be viewed with or without audio in twenty minutes AIMEL T gt TM 0 f2 0 Demand www digikey ca ptm Did You Know In addition to the measurement of the radio parameters Electromag
47. TRL register OxOD ANT_DIV according to the value read from register bit ANT_SEL At the earliest IRQ_2 RX_START as an indication of successful PHR reception can be used to set register bits ANT_CTRL refer to Figure 4 1 However for RX_AACK it is recommended to enable IRQ_3 TRX_END only This interrupt is issued if a frame passes the frame filtering and has a valid FCS When reading register bit ANT_SEL e g after IRQ_3 2 the timing requirements of the succeeding operation have to be taken into account 1 Transmitting an acknowledgement frame requires setting of the transmit antenna after occurrence of IRQ_3 within a TurnaroundTime trr ANT_CTRL 12 tsym 2 Transmitting an acknowledgement frame in slotted operation mode requires setting of the transmit antenna after occurrence of IRQ_3 trR ANT_CTRL tsym As an example the application of Antenna Diversity in Extended Operating Mode RX_AACK is shown in Figure 4 In contrast to the example in Figure 3 an acknowledgement frame is automatically transmitted after a TurnaroundTime 3 To define that the same antenna is used for transmission as for reception the register bits ANT_CTRL are to be set within t accordingly TR ANT_CTRL Sew oe AA aoe oe hE a i ion PS ae f CE em Paia a Gees ey Figure 4 Antenna Diversity in Extended Operating Mode In general the AD algorithm and timings are identical fo
48. W111 CA Digi Key Corporation brings you TechZones featuring suppliers Quick Way to Find Digi Key s TechZones products and resources for Lighting Microcontroller Power Sensor e Links located on our homepage and Wireless technologies with more sites to come Resources e Links located in our header under Resources include application notes reference designs white papers links to e Links located in our toolbar product training modules and more e www digikey ca techzones Understanding Antenna Is Minnesota Specifications and Really That Operation Tain contributed by Linx Technologies Cold in Winter The antenna is probably the most Have you ever wondered if winter overlooked part of an RF design The temperatures in Minnesota really dip to field of antenna design and application W negative 30 degrees Fahrenheit Now is complex By understanding a few you can find out by tracking Digi Key s Weather Center without having to experience the bitter cold yourself ground rules it is not necessary to be an antenna designer to design with an antenna es ee ee rs r THE IMBUSTA ae fe oe iY yi i CT SELE LECTION il svoame FOR IMMEDIATE DELIVERY 3 P s i O i i i 1 ay T i i j i E 7 i eh gt 6 a alk TOJ ny w www digikey ca wireless 3 Table of Contents contributed by Em her lf there s one place you dor and automation
49. aded toward the load versus the voltage wave that is reflected back from the load A perfect match will have a VSWR of 1 1 however the higher the first number the worse the match the more inefficient the system Since a perfect match cannot ever be obtained some benchmark for performance needs to be set In the case of antenna VSWR this is usually 2 1 At this point 88 9 percent of the energy sent to the antenna by the transmitter is radiated into free space and 11 1 percent is either reflected back into the source or lost as heat on the structure of the antenna In the other direction 88 9 percent of the energy recovered by the antenna is transferred into the receiver As a side note since the 1 is always implied many data sheets will remove it and just display the first number www digikey ca wireless 11 Bandwidth FI VSWR Match Quality Frequency Figure 4 VSWR Graph VSWR is usually displayed graphically versus frequency as shown in Figure 4 The lowest point on the graph is the antenna s center frequency The VSWR at that point denotes how close the antenna gets to 50 ohms The space between the points where the graph crosses the specified VSWR typically defines the antenna s bandwidth Directivity efficiency and gain True antenna performance can only be determined by measuring the amount of energy that the antenna radiates into free space This is not an easy task given all of the variables associate
50. adio antenna unit optimizing the design is then a matter of good design practice and know how It is also important to have good measurement facilities for both passive and active testing Testing is usually carried out in an anechoic chamber equipped to emulate the signals coming from GPS satellites and from cellular base stations 18 The GSM system Although the 3G network may be used for trackers GSM is usually preferred because of its more universal coverage The DCS and PCS bands are not usually a significant problem for the tracker designer but the two low frequency bands at 850 and 900 MHz are a major problem If you ask the question can an antenna be made indefinitely smaller the answer is no there is a physical limit This limit sometimes called the Chu Harrington limit is related to the smallest volume that will enclose the antenna expressed in wavelengths If a small antenna working at long wavelengths falls below this limit then either bandwidth or efficiency will be lost The ideal length of a mobile phone for low band GSM performance is around 120 mm but reasonable performance can be achieved down to about 80 mm Unfortunately many tracking devices are as little as 40 mm in their largest dimension so the antenna design is a significant challenge Every antenna must have two halves the antenna itself is one part and the PCB usually forms the other The only exception to this is when the antenna itself
51. ame elements but one is mounted in the middle of the plane and one is mounted on the edge with a right angle connector As can be seen from the plots with the antenna mounted in the middle the pattern is uniform With the antenna mounted on the edge of the plane more energy is radiated away from the plane This will result in the system having a better range in one direction than in another This may impact the performance and perceived quality of the final product so it should be considered early in the design phase ifs w Fi a i j u T F ri 1 r k if Ty i 7 A EF oa ao T w Figure 11a A 418 MHz antenna radiation pattern on a 4 x 4 ground plane centered wa TECHZOnNe Figure 11b A 418 MHz antenna radiation pattern on a 4 x 4 ground plane edge mounted All of these examples have shown a quarter wave monopole that is orthogonal to the ground plane It is also very common to have the antenna in the same plane as the ground Once again the ground plane becomes the other element of the antenna system Figure 12 shows a 916 MHz antenna oriented in this manner This orientation is very common in handheld products such as cellular phones The length of the ground plane that points in the Opposite direction from the antenna is critical Ideally it would be a quarter wavelength long but it can be shorter if the sacrifice in performance can be accepted These measurements are good for illustratin
52. anagement strategies are evolving to meet these changing requirements There are three distinct categories of metering systems each with its own unique requirements The most common type is the electricity meter which quantifies the consumption of electrical energy The second most common is a meter that measures consumption of fluids such as water natural gas or fuel oil The third category heat meters or heat cost allocators quantifies the consumption of thermal energy Electricity metering systems comprise two functional areas metrology or measurement and the communications subsystem Metrology requirements vary by region and meter type residential versus industrial Key variables include the number of phases being measured measurement accuracy the requirement for different rates depending on time of use and the level of security required at the communication layer 32 Electricity meters measure the electrical power consumed by a customer the power factor of the load and the time of electricity consumption to support multi rate metering These measurements rely on various sensor technologies that match the number of electrical phases in the system Consumer meters are typically single phase while commercial and industrial customers often use multiphase meters These meters usually derive power from the mains but require an alternate supply such as a battery or super capacitor to maintain a state in disconnect or disru
53. ardware and features such as encryption are available These vendors don t support one standard over another because they sell several of them Depending upon the protocols developers can even migrate between interfaces with minimal changes to system design This allows manufacturers to support different connectivity options based on the cost and complexity the end product can tolerate 36 There is also a good likelihood that all of these technologies will serve in the same home or business to connect the variety of appliances ZigBee appears to have a clear lead from being integrated into many smart meter architectures However there are concerns that there may be appliances which are too far from the meter or another ZigBee node for reliable connectivity PLC in contrast guarantees a connection A likely scenario is to have ZigBee and PLC PHYs in the meter Access to the meter however is proving to be a tremendous challenge for appliances manufacturers This is because of the great variety of implementations used throughout each country Utility companies use different types of meter and require a different set of APIs to connect with them In addition many utility companies have yet to activate and open their communications link for use by appliances thus preventing the meter from being used as the energy gateway While independent energy gateways are available these too support a wide range of protocols From this perspective
54. artGrid Alliance MICROCHIP naitoWatt ALP Technology Figure 2 Microchip s FCC ETSI Certified IEEE 802 15 4 ZigBee Module and an XLP PIC microcontroller Another option available to smart appliance manufacturers is the use of a proprietary wireless protocol such as Microchip s MiWi Development Environment Proprietary protocols offer many advantages including ease in customization for specific target applications shortened development times when compared against open standard protocols less complexity and ease of deployment They also offer many opportunities for both innovation and IP creation There is no need for the specialized certification that is often required by the open standard protocols which can bring a significant cost savings Additionally all of this adds up to a quicker time to market with a potentially lower cost device However the lack 42 of interoperability with other manufacturers products could result in a narrower market segment for the device or require the development of a gateway device to translate to other wireless networks You can check the feature comparison for the three wireless technologies discussed in this article in Table 1 Table 1 Feature comparison among the three major wireless technologies for smart appliances Open Standard Sollee Data Rate all ald Data security Network data security is of primary importance because of the sensitive nature of the information
55. as as shown in Figure 3 Helical antennas are coiled to reduce their size but that also has the effect of narrowing the bandwidth A ground plane that is too small could narrow the bandwidth to a point where it would be difficult to maintain the antenna s performance over production tolerances and in the presence of external influences Regardless of the antenna style chosen the size of the implemented ground plane should be considered in comparison to the antenna manufacturer s reference plane and calculated ideals Whenever possible actual antenna performance should be measured with tools such as a network analyzer and spectrum analyzer since shifts such as those described above can affect the efficiency of the system and significantly impact the product s final range If the antenna is mismatched the transmitter output power could be increased to compensate but at the cost of higher current consumption and shorter battery life For most receivers there is little that can be done to recover the lost sensitivity In some cases a Low Noise Amplifier LNA can be placed after the antenna and before the receiver s front end but that adds to the cost current consumption and size Not only does the size of the ground plane dictate performance but also the location of the antenna upon that ground plane The plots in Figures 11a and 11b show the radiation pattern for two 418 MHz antennas on a 4 x 4 ground plane Both have the s
56. ation of Antenna Diversity ensures a significant higher probability to access a network node Thus connectivity between network nodes is improved Effects that nodes are not accessible since they are in a deep fade are prevented This may happen even in well established network installation if for examples the environmental conditions changes The use of the AT86RF231 Antenna Diversity transmission technique considerably improves the reliability of real world network implementations This is achieved without increasing the link budget of a network connection e g by using a higher transmit power or and additional pre amplification LNA during receive References 1 AT86RF231 Low Power 2 4 GHz Transceiver for ZigBee IEEE 802 15 4 and ISM Applications Datasheet Rev 8111A AVR 04 08 Atmel Corporation 2 AT86RF231 Software Programming Model Rev 1 1 Atmel Corporation 3 IEEE Std 802 15 4 Wireless Medium Access Control MAC and Physical Layer PHY Specifications for Low Rate Wireless Personal Area Networks LRWPANSs tex TechZOne M2M COMMUNICATIONS M2M or Machine to Machine communications is broadly defined as a physical device that has the capability to communicate with a network Often this communication piece is most efficient and cost effective when it s implemented via a wireless radio Choosing the right technology or deciding if a technology meets your application requirements can be a diff
57. ay per violation up to a maximum of 75 000 What if my intended use or application does not seem to have been clearly addressed by the FCC Recognizing that new uses of low power transmitters often generate questions that are not directly addressed in the regulations the FCC generally welcomes inquiries or requests for specific interpretations Occasionally the FCC proposes changes to its regulations generally to address industry concerns and or as new uses of low power transmission equipment appear Any questions can be directed to the FCC at fccinfo fcc gov or 1 888 CALL FCC How close to the products tested are production units required to be In the FCC s own word identical However identical is further defined as identical within the variations that can be expected to arise as a result of quantity production techniques One of the advantages of using Linx modules is the tight production control and testing procedures to which the modules are subjected Similar controls over the rest of your product s production will make compliance with these requirements straightforward Does the receiver need to be certified The receivers must be issued a Declaration of Conformity DoC by an accredited test lab This is far less complicated and expensive than a transmitter certification There is not an actual filing with the FCC Just keep these documents in your company files This document is not endorsed nor approved by the
58. cerns 7 legal 8 socket 11 three 12 average 13 MCUs Down 1 ZigBee 2 technique 4 Google 6 meters 8 Smart 9 clearly 10 mains Digi Key at your service Programming Programmable Oscillators Digi Reel Battery Packs Cable Assembly Services Departments 800 344 4539 sales General Inquiries E mail sales digikey com Phone 218 681 6674 Fax 218 681 3380 Customer Service E mail customer service digikey com Technical Support E mail techs digikey com Design Support Services DSS E mail design digikey com Phone 877 DK DESIGN 877 353 3744 Quote Request E mail quotes digikey com Comments Suggestions E mail webmaster digikey com Web Links Feedback www digikey ca feedback My Digi Key www digikey ca registration TechZones www digikey ca techzones PTM Online 0n Demand www digikey ca ptm New Digi Key www digikey ca new DK Toolbar www digikey ca toolbar BOM Manager www digikey ca bommanager Digi Key Catalogue www digikey ca catalogue Technical Support Web Chat www digikey ca techchat IERO LUN Hi UL LER SOL UTIONS Biia Lees on Hinge z Eet raman Undted Stutes i p te ot ee ne ee i ree m a ew r Beir a Pais Te Sii a Eiki ani fa ef ELL diane ei 5 B atta Li r TEn Tafti E h See the Latest pe mas Pell mirar Fe rig baer Pee Addeduin the A i Chek Ses bette i a i ipis LA miar Diag Baki Farnam Last 30 ays b z aanas aai ehi Act jka irls ree ahi Ha neg
59. chamber The measurements numbers used are outlined below e TRP Total Radiated Power This defines how much power is being radiated from the device and is measured in dBm The higher this number the better the device is able to transmit TIS Total Isotropic Sensitivity This defines how low a signal the device can receive and demodulate The lower this number with a minus figure the better the device can operate in weak signal environments RSE Radiated Spurious Emissions In practice this is the most difficult test for cellular products to pass from Taoglas experience These are radio waves output by the device which are above the power limit set by regulatory authorities to avoid interference When a test confirms a radiated spurious emission over the limit either the device or the antenna must be modified to get it below the limit and thus pass certification Otherwise the device cannot be sold in that country Different operators especially in the USA such as AT amp T Sprint etc have specific numbers for TRP and TIS that the device must reach to be accepted on their networks Other operators do not specifically set any requirements No matter if it is mandatory or not it is our experience that the wireless products with the best TRP and TIS values succeed in the market Passing RSE is mandatory for any operator whom requires PTCRB or type approvals A design that has optimized TRP TIS will usually pass RSE
60. choosing a correct operational frequency and using a pre made RF module a product designer s burden is greatly reduced With proper attention to such basics as good layout clean supply lines and a properly matched antenna RF success can be a nearly painless process Now that your application has hopefully survived the legal considerations outlined above let s consider the actual technical issues of operation in these frequencies Benefits of operation in the 260 470 MHz band First it should be recognized that the unusual restrictions placed on the band by the FCC do more than just make a designer s life miserable The random periodic nature of transmissions resulting from these restrictions helps to keep this set of frequencies clear of sustained interference Other Part 15 bands are potentially crowded with continuous transmissions of voice data video and even microwave ovens Second longer transmission distances are achieved with less power The free space propagation of frequencies in this range is significantly better than at higher frequencies such as 900 MHz or 2 4 GHz Therefore lower output power is needed to attain any particular distance and power consumption is significantly reduced Third is cost effectiveness The components used at these frequencies are lower in cost than those designed for higher frequencies Fourth is international regulatory compatibility If your product will be sold abroad you will want t
61. courage governments to agree on frequencies and output Tag and reader makers are also trying to develop systems that can work at more than one frequency to get around the problem Yay kK MAA Will using Wi Fi and Bluetooth technologies together cause interference Studies by a number of companies indicate that if the separation is more than two meters in most cases there is no perceptible degradation in transmitted data in either device From two meters to about a half meter there is a graceful degradation As the devices are brought into very close proximity the degradation can be quite noticeable Fortunately this scenario only happens when the two systems are in the same device and in those cases Bluetooth hardware and Wi Fi hardware can collaborate to dramatically improve performance Is there a need for a central controller in a Z Wave lighting system No and this is a major value of a mesh network Other lighting control systems that have been on the market for a while have relied on a centralized lighting cabinet All lighting circuits require wires that lead back to this cabinet and all control functions scenes zones intensity are controlled inside this cabinet Operation of the system is determined by use of wall mounted switches dimmer and controllers However everything is hard wired back to one control cabinet Z Wave eliminates the centralized cabinet requirement thus dramatically lowering the co
62. ctrums and multiple wireless protocols including Wi Fi ZigBee RF4CE and MiWi proprietary Design considerations A common pitfall that designers encounter as they develop a wirelessly enabled smart appliance is the failure to future proof their devices For example choosing a wireless technology that cannot be scaled upward to accommodate the demand for the larger networks of the future is a problem One design consideration is that even though these smart appliances are packed with the latest technology their interfaces should be clean intuitive and simple for the user or else these appliances may not gain wide acceptance in the marketplace Often designers fail to take into account both the physical and RF environments in which their smart appliances will reside Therefore factors such as humidity the thickness of walls and the presence of microwaves must be considered when designing the device The styling of an appliance and its functionality should be cohesive such that the former does not degrade the latter Consideration should also be given to the appliances certification particularly for those that employ open standard protocols The product s certification is a key milestone that must be completed before the product can be sold Conclusion In this article the major components that make up a wirelessly enabled smart appliance platform were described These components are the microcontroller the protocol stack a
63. curate sharp filtering of the incoming signals and a variable threshold digital demodulator for optimum recovery of the baseband data signal The data pins are TTL CMOS compatible for direct connection with a microcontroller and the circuit supports operating frequencies from 95 to 148 5 kHz The IC is designed for worldwide use and complies with industry standard regulations It is compliant with US Federal Communication Commission FCC Industry Canada Japan MPT and European CENELEC EN50065 1 regulations for signaling in the 125 to 140 kHz and the 95 to 125 kHz frequency bands The transmission and reception stages are controlled either by an external reference clock from the system s microcontroller for example or by the on chip reference oscillator connected to a crystal This ensures the accuracy of the transmission carrier and the exact trimming of the digital filter thus making the performance independent of application disturbances such as component spread temperature and supply drift The device includes a power output stage that feeds a 120 dBuV RMS signal on a typical 30 Q load To reduce power consumption the IC is disabled by a power down PD input pin In this mode the on chip oscillator remains active and the clock continues to be supplied at the CLK_OUT pin For low power operation in reception mode this pin can be dynamically controlled by the microcontroller wa TECHZOnNeE Table 1 TDA5051A highli
64. d States When working with RF a clear distinction should always be made between what is technically possible and what is legally acceptable Achieving a solution that meets technical objectives but cannot be legally sold or operated serves little use As such issues of legality should be given high priority Legal considerations In the United States the Federal Communications Commission FCC is responsible for the regulation of all RF devices These regulations are contained in the Code of Federal Regulations CFR Title 47 Title 47 is made up of numerous volumes however all regulations applicable to operation in the 902 928 MHz band are contained in volume 0 19 It is strongly recommended that a full copy of the code be obtained from your local government bookstore the Government Printing office or the FCC website What is unlicensed operation Certain bands within the RF spectrum are available for unlicensed operation The term unlicensed is often misunderstood The manufacturer of a product designed for unlicensed operation is not exempt from testing and or certification Indeed both the transmitter and receiver must be tested by a qualified testing laboratory However once the necessary approvals are received the end user can then operate the product without further obligation or licensing The frequencies from 902 928MHz are allocated for a wide variety of unlicensed applications These include unlicense
65. d energy Since our typical load power is less than the available energy any excess energy can be stored for later use on Coorp TEE THERASOELECTAH GENERAT IA 1nk iAy 10 See ae Wam OPTIONAL SYiTCHED OUTPUT POA SENSORS Figure 5 LTC3109 Power Management Circuitry Figures 3 and 4 show the 3 3 V output of the LTC3109 before during and after a measurement transmit cycle The capacitor on V is sized based on the acceptable voltage droop for one measure transmit cycle In our example we ve determined that a voltage droop of 300 mV is acceptable on the 3 3 V output Using the values obtained previously we can calculate the required C a a RI out 7 dV 30 mA 30 ms 500 uA 2 ms 3 mA 5 ms Say 0 3 V 1 74 mF select a nominal 2200 uF capacitor Where _ sum of all the loads on the 3 3 V output load l average output current of the LTC3109 dT duration of the load pulse dV acceptable voltage droop The actual droop in Figure 4 is much less than the 300 mV This is due to a lower current transmit pulse duration for the simple system that was measured and the higher output capacitance Figure 6 shows the 3 3 V output during a temporary interruption of the energy harvesting transducer input In this case the LTC3109 operates from the storage capacitor C There is no limitation on the value of C _ SO it can be sized for whatever system holdup time is desired 2V DIV 20mA DIV
66. d output power Since the output power is allowed to climb as the frequency increases it might appear that selecting the highest frequency would give the best range performance This is not the case however since free space attenuation increases proportional to frequency Thus the regulations equalize the bands propagation characteristics Antenna size and efficiency should also be considered Compact or reduced sized antennas will generally not be as efficient at the lower parts of the band It is always important to note that the RF level radiated into free space is dependent not only on raw output power but also factors such as the type of antenna employed circuit layout and ground plane Most transmitter modules including those manufactured by Linx are www digikey ca wireless Is My Application Legal for Operation Under Part 15 231 A D Banned Transmission Types Linder 15 291 A D You May Not Allowed Transmission Types Under 15 231 A D You May Transmit a conin of crema 0 codes in order to identify a system component ado cony signals during emergencies daia as long as accompaniod by sgal Transmitter Activation Method Is It Legal Under Para E Any Operation ts Adicwed Unger Parag E Proa 1 The oulpul power is reduced 2 Maximum inenemission time 1 sec 4 The mikun period between transmissions is 30 times the iransmssion porod but mayn loss than 10 eronda 4 The Rannonic and bandwidth
67. d products operating under Part 15 as well as Part 18 Industrial Scientific Medical ISM devices What must I do to be unlicensed Part 15 requirements for many bands are somewhat obscure and difficult to interpret Thankfully the regulations of Part 15 for the 902 928 MHz band are very straightforward There are no restrictions on the application content or duration of transmissions only on factors such as power output bandwidth harmonic and spurious emissions While Linx modules are inherently designed to meet these requirements it is important to note that external factors such as layout antenna type and output power can affect both the module s performance and compliance While these issues may appear formidable they are generally not By choosing the correct operational frequency and using a pre made RF module a product designer s burden is greatly reduced Since the approval procedures for transmitters and receivers are quite different let s look at each separately tex TechZOne Receiver procedure The receiver is considered an unintentional radiator and is subject to authorization under the Declaration of Conformity process This is a simple process in which an accredited laboratory tests the product to ensure that the equipment complies with all applicable FCC standards An FCC filing or submittal is not required unless specifically requested pursuant to Section 2 1076 The test results should be maintained wi
68. d with radiated measurements When the radiated power is measured around the antenna a shape emerges called the radiation pattern This is the most direct measurement of an antenna s actual performance 14 Ae Mona Figure 5 An example of Radiation Patterns Antenna radiation patterns can take on many interesting shapes particularly when presented graphically in their real world three dimensional state The adjoining diagram shows shapes typical of the most popular antenna types For a dipole antenna the pattern looks like a doughnut For a monopole antenna on a ground plane cut that doughnut in half along the edge and set it on the plane with 12 the antenna sticking up through the middle The Yagi s directivity can be clearly seen although that term and the value of these types of plots will become even more apparent as directivity efficiency and gain are discussed After the radiated energy surrounding an antenna is measured the data is often turned into a radiation pattern plot This plot graphically presents the way in which the radio frequency energy is distributed or directed by the antenna into free space An antenna radiation pattern plot is an important tool since it allows rapid visual assessment and comparison of antennas The antenna s radiated performance and thus the corresponding plot will be influenced by the test jig or product on which the antenna is mounted This makes the comparison of pl
69. devices Lit compromise your low powe careful design and componer Using Third Party IP Protocol Stacks in M2M Des by Rick Bailey Multi Tech Systems Inc Each new IP stack requires developers to Nr Embedded Design Requirements for Smart Metering SysteMs cccssecssssesses a by Keith Odland Silicon Laboratories Inc Smart meters create unique challenges for RF designers who have to balance the limitations of current energy storage technology with the ever growing power consumption requirements of the complex systems Designing Intelligent Appliances for the Smart Grid cc scsssssssseresssees 34 by Nicholas Cravotta With the development of Smart Grid technology the focus is first and foremost on enabling significant cost savings by intelligently monitoring and managing power consumption As the Smart Grid is deployed however it will also bring with it an infrastructure that will readily support a wide range of automation capabilities Merging Legacy Syste and the Smart Grid 38 by Dave Mayne Digi International The Smart Grid requires smart devices but legacy devices will dominate for years to come It is possible today to add communications over public networks cellul adband etc that deliver consumer Agagement energ yement services with full HAN support Microcontrol l Wireless onnectiv art ApplianCes scsesssesssseene 41 ci diere and Abhinay Venuturumilli Igy
70. dio sleep current e Battery self discharge Periodic events Periodic events occur at various intervals during operation thus their current draw cannot be measured directly as it can be with steady state events Instead the total energy consumed during the event is measured in uC and then converted to average current based on the event frequency The following equation shows this calculation I event average current yA number of events x event energy uC Time There are two types of periodic events e Ember EM35 7 radio transmissions e Ember EM35 7 data polls Sensor and radio parameters Each security sensor has a sensor and a radio both components have different parameters that affect battery life These parameters are calculated in either current consumption or energy consumption the differences will be explained later in this section Table 1 summarizes the radio and sensor parameters determined by Ember and iControl Table 1 Radio and sensor parameters Parameter Steady state current consumed when Steady state the radio is in an idle state operation Radio Parameters Radio sleep current Radio transmissions Energy required to complete a data poll Periodic event operation and transmit a data packet Data poll Steady state current consumed by the sensor when idle Sensor Parameters Sensor stand by Steady state current operation Event energy Amount of energy required by a given Periodic event
71. dium whereby RF energy is transferred from one place to another with minimal loss This is a critical factor because the trace leading to the antenna can effectively contribute to the length of the antenna changing its resonant frequency The width of the microstrip line is based on the desired characteristic impedance of the line the thickness of the PCB and the dielectric constant of the board material When implemented correctly the microstrip line will connect the antenna to the RF stage without affecting the antenna s resonant frequency or the match to the RF stage One other thing that frequently seems to catch designers off guard is that standard connectors such as SMA BNC and MCX are illegal for use as an antenna connection in the United States for devices falling under some sections of CFR Part 15 The FCC does not want the end user to be able to change the antenna from the one that was certified with the product For this reason the antenna will need to use a non standard proprietary or permanent connection Fortunately the FCC considers reverse polarity connectors to be non standard so they are commonly used by OEMs for the antenna Putting it all together The antenna is a critical component to a system s performance and should be considered early in the design process It should be recognized that specifications on an antenna s data sheet will not necessarily reflect its performance in the final product This is a res
72. e battery self discharge This formula is shown below where represents current I total average current uA steady state operation average pA I periodic events average LA The Technical Background section laid the groundwork for all the work devoted to measuring and calculating each of these variables The following sections provide the actual values used in these formulas to determine the battery life for the contact sensors Contact sensor battery life calculations As described above the contact sensor battery life is calculated by dividing the battery capacity by the average current draw While the battery capacity is easily estimated by derating the battery the average current draw is obtained by summing all the steady state and periodic events taking place by the radio and sensor Here is a list of those events e Steady state operation Radio sleep current Battery self discharge e Periodic events Data poll Radio transmission 28 The total average current equation is as follows I total average current steady state operation I periodic events I radio sleep current I battery self discharge I data poll I radio transmission The total number of events per day was estimated to be 100 This value is defined by the application but this variable could be adjusted to accommodate different security scenarios Similarly the data poll rate was set for once every 27 minutes or 53 poll
73. e microcontroller which acts as the brain of the appliance the wireless protocol stack which defines the logical connections amongst devices in a network and the RF transceiver which handles the transmission of packets over the air Today s manufacturers have a wide selection of microcontrollers around which to design their smart appliance platforms One of the major selection criteria is the cost of the microcontroller Additional criteria are the size of its program and data memory its power consumption the availability of peripherals and its processing speed Another important subsystem of the smart appliance platform is the wireless protocol stack Its operation determines how the devices communicate how many devices may be on a single TD TechZone Home Area Network HAN and the maximum data throughput The protocol stack is often the most complex software module in the application firmware The development time of the smart appliance can be greatly reduced if software for the stack is already available Moreover the portability of a vendor s stack across all of its microcontroller families is of primary importance This gives the developer the flexibility to choose the 8 16 or 32 bit microcontroller that is most appropriate for a given platform while maintaining the same protocol stack functionality and features The RF transceiver completes the major components of the smart appliance platform handling the dutie
74. e potential for wireless sensor networks powered exclusively or supplemented by energy harvesting techniques Ultra low power wireless protocols are beginning to achieve widespread industry acceptance and standards are in active development Sensor networks unshackled from the mains or battery power open the possibility for greater reliability lower maintenance costs improved safety and widespread deployment Applications unthinkable only a few years ago are now possible with energy harvesting techniques Newly available power management products can convert the inconvenient intermittent and often miniscule outputs of various energy harvesting transducers Thermo Electric Generators photovoltaics piezos electromagnetics into usable power for modern electronics A new way of specifying analyzing and designing with these power management devices is necessary to fully exploit the capabilities of the respective energy transducer elements and the sensor networks electronics that are ultimately powered by them Wireless sensors are not new making them semi or fully autonomous through the use of energy harvesting techniques requires the proper selection and design of energy transducers and power management devices A typical wireless remote sensor node is shown in Figure 1 To date the missing link in this system has been the power management solution The transducers available to provide power are often very inconvenient to work with pr
75. e tag s UHF transmissions typically cover the required range even at output power as low as 0 dBm The latest approach to implementing LF wake up receivers is exemplified by a device recently introduced by austriamicrosystems the AS3933 LF wake up receiver On the crucial parameters the AS3933 offers typical current draw in three channel listening mode of 1 7 pA and typical wake up sensitivity of 80 Vrms which is more than ten times better than its nearest competitor The wake up interrupt can be triggered by frequency detection only but to guarantee false wake up rejection the device includes an integrated correlator that detects programmable 16 or 32 bit Manchester wake up patterns Frequency tuning is an important technique for improving sensitivity and effective range the AS3933 implements an automatic tuning function using on chip tuning capacitors This reduces bill of materials cost since external high precision tuning capacitors are not required and it also enables simplified antenna checking on the production line Furthermore the on chip antenna tuning capability provides a means for end users to check the connection status between the tag and reader www digikey ca wireless 49 The FCC Road Part 15 from Concept to Approval Once your wireless widget is ready for market how do you get FCC Part 15 approval Knowing the process and starting it from the beginning helps shorten and smooth out the road ahead
76. elf oscillates and the built in synchronous rectification improves energy harvesting yield LS MYR gt PTM Orlie O De e www digikey ca ptm www digikey ca wireless 63 Is Minnesota Really That Cold in Winter Find Out with Digi Key s Weather Center Have you ever wondered if winter temperatures in Minnesota really dip to negative 30 degrees Fahrenheit Now you can find out by tracking Digi Key s Weather Center without having to experience the bitter cold yourself By the way the answer is yes it s that cold Engineers from Digi Key s Design Support Services team began developing the Digi Key Weather Center in a collaborative effort in February 2010 The Digi Key Weather Center was placed on the roof of Digi Key s 600 000 square foot facility in Thief River Falls Minnesota in July 2010 The Digi Key Weather Center was developed to demonstrate connectivity to customers by using products sold and supported by Digi Key Because Digi Key is located in Northern Minnesota where the weather changes dramatically from summer to winter it was determined to be the perfect location to demonstrate data communication with a weather station The primary device used to develop the Digi Key Weather Center was a ConnectPort X4 ZigBee to Ethernet gateway which is equipped with access to iDigi from Digi International one of Digi Key s 440 franchised suppliers Additionally Digi International Series 2 XBee modules programmed
77. ents has been the unleashing of design innovations within the application space of smart appliances We are rapidly approaching the time when it will be commonplace to live in an affordable smart home with its many smart appliances all wirelessly connected as depicted in Figure 1 However these innovations are not without many design challenges This article will discuss some of these challenges and the trade offs that are involved when choosing among the technologies that are used in a smart appliance It begins with the choice of which wireless protocol to use Wireless technology choices In terms of wireless networking protocols the smart appliance manufacturer has a number of viable options to choose from Some of the choices include Embedded Wi Fi ZigBee and proprietary protocols such as Microchip s MiWi Development Environment Wi Fi is the most widely used wireless protocol It is the wireless equivalent of the wired Ethernet protocol that forms the backbone of today s internet Typically Wi Fi operates on high performance computers which can handle data intensive applications Compared to traditional Wi Fi Embedded Wi Fi performs a single or very limited number of functions such as transmitting static images but at relatively lower data rates www digikey ca wireless 41 Embedded Wi Fi offers clear advantages in that any Wi Fi enabled smart appliance is able to readily communicate over the Web Typical data rates of 1
78. equate percentage of projected Smart Grid investment benefits without replacing the current asset There are a growing number of communication companies trying to address these questions in an effort to accelerate deployment of Smart Grid services and service the widely varying business case drivers being presented by utilities large and small Smarter AMR with consumer engagement The industry is closely watching the early adopters of Smart Metering technology with several utilities now announcing deployments exceeding one million units While this progress is impressive there are nearly 150 million meters that are already automated with AMR communication technology Clearly these devices do not provide all of the interval data collection remote disconnect capabilities or other enhanced communication services that are envisioned for the final Smart Grid deployment But it is possible today to add communications over public networks cellular broadband etc that deliver consumer engagement Energy management services with full HAN support These capabilities allow utilities to deliver a broad range of demand side services to their customers leveraging the existing metering investment Digi International for example recently launched a series of ERT gateways enabling the owners of over 40 million ERT meters to communicate over IP networking solutions This allows utilities to millions of units 350 350 Un Automated 300
79. erating data to monitor energy usage The TDA5051A from NXP Semiconductors a highly integrated modem for in home control applications gives developers a simple convenient way to meet consumer demands for low cost energy saving networks for home automation Optimized for Amplitude Shift Keying ASK data transmission and reception over a home power network the TDA5051A can be used in a range of home control applications such as lighting home appliances energy monitors and meters and heating and cooling systems NXP ASK powerline modem TDA5051A The NXP TDA5051A transmits and receives digital signals on standard powerlines or any two wire AC or DC network It is a cost effective solution that transmits at a rate of 600 typ or 1200 max baud operates from a single 5 V DC supply and enables easy connection to standard microcontrollers including NXP s LPC11xx series of low power ARM based microcontrollers The carrier frequency is set by an input reference clock or an on chip oscillator 44 DIGITAL DATA IN r AMPLIFIER TX_OUT MODULATION OSCILLATOR TDASOSIA CLK_OUT DATA_OUT3 GITAL igen DEMOODULATOR Figure 1 TDA5051A block diagram Figure 1 gives a block diagram of the TDA5051A circuit The IC includes a high sensitivity input amplifier with Automatic Gain Control AGC for secure detection of small signals on noisy mains It also has a digital narrowband filter with an 8 bit ADC for ac
80. eric 1 0 server and the fieldbus 1 0 proxy is a generic I O client The 1 0 device is seen as a field bus 1 0 from the view of the fieldbus configuration PC The field bus I O proxy searches the 1 0 device attributes database to find out about which digital and analog in and outputs that are available for the O unit Another interesting application where the very fast and secure connection is needed is the use of Bluetooth Low Energy as a key in order to allow a mobile operator s panel to get access to the automation cell or machine This feature can also be used in combination with the proximity function This function is based on the SSI signal strength indication value and can give a message if the user is within the production cell or not in order to allow interaction or not www digikey ca wireless 59 ret SSS Se SS eS Figure 9 Automation 1 0 and proximity are used to control the operator s access to the manufacturing cell PRODUCTS Added in the Last 90 Days GLICK HERE 60 Bluetooth low energy technology meets all the requirements of a wireless solution for sensors and actuators In short the following are the highlights of Bluetooth low energy technology for sensors and actuators e Cost effective stand alone solutions e Multiple chipset supplier that secure a long term availability of the components e Robustness inherited from Classic Bluetooth the most robust industrial wireless s
81. erline The TDA5051A in the appliance unit receives the data from the powerline and decodes it for the low cost microcontroller which uses the data to perform the function requested by the control unit This in home control network is designed to support a wide variety of commands In addition to simple on off commands it can support incremental commands such as bulb dimming or adjusting window blinds up or down The network can control appliance operation too such as turning on a DVD player and then playing a DVD The set up can also transfer data across the network to monitor energy usage or send notifications such as when a refrigerator has been opened 46 Figure 4 The TDA5051A in a lighting control network demonstration kit Sample application lighting control Figure 4 shows the TDA5051A modem and the LPC1114 microcontroller configured for a lighting control application NXP makes this configuration available in an evaluation demonstration kit The kit consists of a master controller and a slave lighting controller each housed in a separate plastic box The master controller consists of three boards a TDA5051A board an LPC1114 board and a power management demonstration board which provides the 5 V DC and 3 3 V DC power supplies The master controller board has four push button switches to provide dim up and dim down as well as on off and color mixing lighting control with a remote slave controller Similar to
82. eter itself dynamic range impacts accuracy and so a higher resolution ADC is needed For systems that operate within a well defined range a lower resolution ADC may be sufficient One side benefit of self monitoring is the ability to profile appliance operation With enough accuracy an appliance can identify that it is exhibiting degraded behavior and alert the owner that servicing is required to avoid system failure Major Smart Grid players such as Microchip STMicroelectronics and Texas Instruments offer a variety of metrology ICs to support their extensive offerings of Smart Grid components ICs start at 1 for low end applications and can run up to 20 for higher current and precision applications To improve efficiency appliances also need to support demand response events and actively assist consumers in making usage choices based on tiered rates Traditionally the home HVAC system must be adjusted manually to reflect pricing tiers When the thermostat is connected to a smart meter it becomes possible to download real time rate schedules and adjust usage automatically When peak demand is high the thermostat can be adjusted to a higher temperature and even turned off directly by the utility companies Note that appliances such as refrigerators communication devices phones routers computers and especially medical equipment cannot be arbitrarily shut down Only devices that are connected to the Smart Grid can be managed in this
83. f deep fades and to create a reasonable average packet error rate At each track position the packet error rate PER is measured using 200 packets and a frame length of 50 octets Multipath Propagation Characteristics Exemplary a measurement result of a 2 4 GHz multipath scenario in a laboratory environment is shown in Figure 9 One curve represents the received signal power at one single antenna The received signal power is measured at each antenna separately using an ED measurement a H ED Level mj hee aa et Figure 9 Multipath Propagation Fading Effects The received signal power at the two antennas varies up to more than 25 dB at certain measurement points refer to positions 380 mm and 850 mm for instance or up to 35 dB over the measurement distance When assuming a larger distance between the two nodes or a more complicate multipath scenario the average received signal power is significant lower Then one antenna may not receive a sufficient high signal power to correctly receive a frame In this case the other antenna is selected to receive the frame Figure 9 further shows that a distance of about A 2 between the two diversity antennas is required to effectively distinguish between different multipath channels The AT86RF231 Antenna Diversity Radio Extender Board V shape placement of the two antennas offers in addition linear antenna polarization This improves the ability to separate between orthogonally
84. f the AT86RF231 Antenna Diversity capabilities Wireless communication channel models In wireless communication systems different channel models are used to describe A simple model is additive white Gaussian noise AWGN This model assumes a linear addition of wideband noise to the wanted signal with a Figure 1 AT86RF231 Antenna Diversity Radio Extender Board constant spectral density and a Gaussian distribution of the amplitude More realistic wireless channel models also consider the impact of multipath propagation Since a transmitted signal is subject to reflections and refraction on walls surfaces etc the receiving node will see many signals each differing in phase and amplitude All signals superpose at the receiving antenna causing an effect called fading Using more than one antenna allows the evaluation of different multipath scenarios to avoid or reduce the effects of fading or interferences Assuming that these antennas are independent of each the behavior of the air interface other with respect to the signal propagation paths the probability that all of them suffer from fading at the same time is significantly reduced AT86RF231 Antenna Diversity The AT86RF231 Antenna Diversity AD feature supports the control of two antennas to select the most reliable RF signal path A differential control pin pair pin 9 DIG1 and pin 10 DIG2 is used to control an external RF switch selecting one of the tw
85. fault value for ANT_EXT_SW_EN Q Mandatory setting for applications not using AD Antenna 0 ANT_CTRL Note The register values 1 and 2 are mandatory for ANT_DIV_EN 1 and ANT_EXT_SW_EN 1 wa TECHZONE AT86RF231 Antenna Diversity Radio Extender Board Overview An AT86RF231 Radio Extender Board supporting Antenna Diversity AD REB is shown in Figure 1 The interface between the radio transceiver and the microcontroller is similar to the basic application schematic Schematic An excerpt of the AD REB schematic with focus on the RF section is shown in Figure 5 nite Lai ATER ZJ aves wees i 1 sup TA aves 2 es ATAF IJI ey L t TE w DD noo 6 ed rt is i E ono cas E E NM g 2 P E z i E amp 3 F J me H7 T f el al af af a I Figure 5 AT86RF231 AD REB RF Section Schematic Layout Figure 6 AT86RF231 AD REB RF Section Layout Diversity Antenna Considerations and Implementation Details The AT86RF231 AD REB implementation makes use of both space and polarization diversity Polarization diversity is the ability to receive orthogonally polarized waves with independent propagation characteristics Therefore the antennas are placed with a specific distance and angle The distance can be derived for instance from the width of the deep fade regions as shown in Figure 9 j B E ki t Figure 7 Antenna Configuration Examples The placement onto the PCB FR4 subst
86. g concepts but they are only valid for that specific antenna when measured on that specific board Since anything placed on the board is in the near field within one wavelength of the antenna it will have an impact on the radiation pattern Any change in the shape of the board within one wavelength will also have an impact on the pattern While manufacturers patterns can give a general idea of the antenna s performance they often bear no resemblance to the antenna s performance on the final product Polar plots for these types of antennas are expensive to make and do not provide much useful information to the customer This may be why some antenna manufacturers do not list gain specifications or polar plots for monopole antennas However there are many antenna styles for which manufacturers gain and radiation patterns are valid Yagi parabolic corner and horn antennas are all types that do not depend on a ground plane provided by the designer Broadcast antennas for AM FM radio will often use the Earth as a ground plane the transmitting towers at the radio station not the receivers Since the Earth is much larger than one wavelength at these frequencies it acts like an infinite ground plane However none of these styles would be considered for use in a portable product A dipole antenna can also be affected in a similar way by the ground plane depending on its construction Some dipole antennas are in the same form fac
87. g to network and other technology changes On February 18 2008 the Advanced Mobile Phone System AMPS better known as the analog cellular network was no longer required to be supported by the carriers This change forced the industry to figure out new methods of communicating with thousands of metering and distribution devices most deployed at commercial utility customers across North America The industry did not respond with a singular approach to this issue but rather architected innovative solutions that met the needs of their respective business For some utilities this helped accelerate Smart Grid deployments while others worked hard to avoid any meter change outs by identifying technologies that could IP enable dial up modems These decisions were not made based on the best technology but rather based on the business drivers This is true for Smart Grid deployments as well There is not nor will there be a single software or communication solution that works for all utility business functions The reality is that many communication www digikey ca wireless 39 solutions public private wired and wireless all can and will contribute to the overall Smart Grid ecosystem Each technology provides a unique set of performance cost reliability and security goals that differentiate but do not diminish their contribution to the overall system The challenge for the industry is not in identifying the communication sol
88. ghts Features Benefits ASK powerline modem operating at Easy to implement simple to up to 1200 bps modulate demodulate and requires little bandwidth Carrier frequency set by clock from Flexibility in choosing clock source microcontroller or on chip oscillator AGC receiver input Improved noise performance and adjustment of signal level Ensures maximum sensitivity of ADC Easy compliance with EN50065 1 with simple powerline coupling and complies with industry networks standard regulations S016 plastic package Low cost solution with easy assembly Housed in an 016 plastic package the TDA5051A requires just a few external components for full operation To complete a home automation application a low cost mains coupling network a 5 V power supply a microcontroller which can use the same supply and a standard quartz crystal which is used with the on chip clock circuit to set the modem s operating frequency are required For added simplicity the CLK_OUT output signal can be used to clock the microcontroller Used with powerlines worldwide Transmission reception and data formats The TDA5051A has been optimized for performance in applications requiring data communication over any two wire AC or DC network During transmission to provide strict stability with respect to environmental conditions the carrier frequency is generated by dividing the reference clock by 64 using a prescaler divider in the dev
89. gn aids with product selection and development tools and provides assistance with other applicable design issues Additionally members of the DSS team produce application notes webinars and instructional videos The DSS team is available from 8 30 a m 5 00 p m CST via telephone e mail and web conferencing software w digikey ca design i no Ms ee Her oes www digikey ca wireless 19 AVR2021 ATS86RF231 Antenna Diversity Antenna diversity is your best protection against multipath fading Using it can considerably improve the reliability of real world network implementations Antenna Diversity is a transmission method using more than one antenna to receive or transmit signals along different propagation paths to compensate for multipath interferences Due to multipath propagation interference effects between network nodes the receive signal strength may strongly vary even for small changes of the propagation conditions affecting the link quality These fading effects can result in an increased error floor or loss of the connection between devices Applying Antenna Diversity transmission techniques in such scenarios improves the reliability of an RF connection between network nodes This article describes the usage design and layout of the AT86RF231 Antenna Diversity an implementation is shown in Figure 1 The information provided is intended as a helping hand for hardware designers to make use o
90. h design with GPS RF Antenna Module visible highlighted on the right side of picture Device size 45 mm x 38 mm x 17 mm LxWxH www digikey ca wireless 17 The GPS system The GPS system is based on a constellation of satellites currently numbering around 30 Each satellite transmits continuous radio signals containing navigation messages and a GPS receiver calculates its position by careful timing of these signals One of the most important parameters is the Carrier Noise ratio C N which the receiver computes and reports for each satellite The Carrier is the wanted signal from the satellite and the Noise is the unwanted background signals Background thermal noise is always present but there may be noise from the tracker itself and any other electrical devices that are nearby With a good C N low noise a good view of the sky and plenty of satellites visible a stationary GPS tracker can locate itself with a median error of about 2 5 m When the noise level rises this rapidly gets worse so it is important to maximize C N Navigation systems for cars or hand held devices used for hiking are relatively large structures and do not generally include a cellular radio In a small tracking device the GPS receiver and the cellular radio are squeezed into a very small space giving the following problems e Noise from the GSM system the host processor and even the LCD display where fitted may interfere with the reception of GPS signals
91. h low energy technology brings to the scene the possibility to use wireless in very simple and inexpensive devices such as the case when integrating sensors According to the Bluetooth SIG we are looking at potential billions in volumes in the following applications e Phone Accessories gt 10 billion e Smart Energy energy counter and displays 1 billion e Home Automation gt 5 billion e Health Wellness Sports and Fitness gt 10 billion e Assisted Living gt 5 billion e Animal Tagging billion e P2P Intelligent Transport Systems gt 1 billion e Industrial Automation M2M 10 billion These high volumes and the possibility of integration in mobile phones and laptops allow for low cost and long term availability of the radio components The technology concept Possibility for low power consumption Bluetooth low energy technology has been designed from the beginning to use the lowest possible power consumption For instance the Bluetooth low energy unit can be put in sleep mode where it is only used at an event of sending active files to a gateway PC or mobile phone Further the maximum peak power consumption is set to less than 15 mA and the average power consumption is at about 1 pA A foundation for the low energy consumption is the very fast connection set up few ms and the short messages Therefore the energy consumption is reduced to a tenth of a Classic Bluetooth www digikey ca wireless 5 unit In othe
92. have targeted the above figures for device efficiency but if you look closely most mobile phones do adhere to the guidelines below Certain operators negotiate directly with mobile phone companies on lower TRP TIS standards on their device on a case by case basis These options are unlikely to be available to M2M devices A Ground planes lt 65 mm long For a ground plane with a length of less than 65 mm and 40 mm wide the only solution is a complete custom antenna The type of antenna material and design will vary from device to device and the process should begin at the start of the product design process B Ground planes gt 65 mm long i On board Antenna Solutions minimum width needs to be 40 mm PA 25a Ceramic Antenna e Cleared area needs to be all the way across the short side of the board e From module side to antenna it requires 10 mm clearance to metal e Other sides must be completely free of metal a Figure 1 PA 25a Ceramic Antenna Custom Metal PIFA Antenna e Can work directly on ground plane on center edge of PCB minimum height of elements 10 mm length 60 mm and width 25 mm e Clearance to other metal components ideally 20 mm or greater in all directions Figure 2 Custom Metal PIFA Antenna ii Off board Antenna Solutions Ground plane width of the device needs to be greater than 20 mm A proven example is 80 mm x 40 mm of ground plane and 20 mm of clearance from antenna to metal but
93. he selection of a specific antenna is done either by the AD algorithm ANT_DIV_EN 1 or according to register bits ANT_CTRL if the AD algorithm is disabled Do not enable Antenna Diversity RF switch control ANT_EXT_SW_ EN 1 and RX Frame Time Stamping IRQ_2_EXT_EN 1 at the same time As long as register bit ANT_EXT_SW_EN is set the control pins DIG1 DIG2 are activated in all radio transceiver states If the AT86RF231 is not in a receive or transmit state it is recommended to disable register bit ANT_EXT_SW_EN to reduce the power consumption or avoid leakage current of an external RF switch especially during SLEEP state If register bit ANT_EXT_SW_EN 0 output pins DIG1 and DIG2 are pulled down Table 4 Antenna Diversity RF Switch Control Register Bit Value Description Poo Antenna Diversity RF switch control disabled Antenna Diversity RF switch control enabled Notes 1 If ANT_DIV_EN 1 register bit ANT_EXT_SW_EN shall be set to 1 too 2 If ANT_EXT_SW_EN 1 register bit IRQ_2_EXT_EN shall be set to 0 e Bit 1 0 ANT_CTRL These register bits provide a direct static control of an Antenna Diversity switch Setting ANT_DIV_EN 0 Antenna Diversity disabled this register setting defines the transmit or receive antenna ANT_EXT_SW_EN Table 5 Antenna Diversity Static Antenna Selection Register Bit Description Reserved Value EE Antenna 1 DIGI H DIG2 L DIGI L DIG2 H De
94. he switch The double throw switch draws no current until it senses the door or window opening or closing During deep sleep the sensor consumes only 0 65 pA which comes from the power used by the EM357 to perform the periodic data polls The iControl contact sensor components include the following e Ember EM357 ZigBee SoC e Power amplifier and low noise amplifier circuit e Reed switch the simple open close switch mechanism that monitors the state of doors and windows e One CR2 battery rated at 800 mAh Figure 2 shows the iControl contact sensor eC 4 Figure 2 iControl contact sensor Technical background When calculating battery life it is necessary to understand the four factors that drive power consumption e Operating states e Sensor and radio parameters e Various measurement units utilized in the calculations themselves e Battery technology Operating states Every activity that the security sensors perform falls into one of two types of operating states steady state operation or periodic events This section explains each of these operating states and how the average current consumed for each is measured Steady state operation Steady state operation is the normal idle state with minimal current drain while the sensor is sleeping The current draw is consistent and energy use can best be expressed accurately as pA In calculating battery life two different states of operation must be considered e Ra
95. heoretical realm and are now poised to enter the mainstream Copyrights The masthead logo design articles content and format of TechZone is Copyright 2011 Digi Key Corporation All rights are reserved No portion of this publication may be reproduced in part or in whole without express permission in writing from Digi Key Trademarks DIGI KEY the Digi Key logo TECHZONE and the TechZone logo are trademarks of Digi Key Corporation All other trademarks service marks or product names are the property of their respective holders All product names descriptions specifications prices and other information are subject to change without notice While the information contained in this magazine is believed to be accurate Digi Key takes no responsibility for incorrect false or misleading information errors or omissions Your use of the information in this magazine is at your own risk Some portions of the magazine may offer information regarding a particular design or application of a product from a variety of sources such information is intended only as a starting point for further investigation by you as to its suitability and availability for your particular circumstances and should not be relied upon in the absence of your own independent investigation and review Everything in this magazine is provided to you AS IS Digi Key expressly disclaim any express or implied warranty including any warranty of fitness for a particular purpose
96. hoose If your product passes the testing the TCB will generally issue a Grant of Certification within a few days What does testing and certification cost This depends largely on the test lab and how many of their services you choose to utilize Full transmitter and receiver testing can cost around 5 000 transmitter only around 3 500 and the receiver about 1 500 The entire process can now be rapidly completed and many labs can perform other testing at the same time What if my application is denied and don t think the FCC correctly understood my product The FCC sees thousands of applications a year Depending on your presentation an inspector may misinterpret information It is possible If you feel you have fairly complied with the regulations you will want to exercise your rights in accordance with CFR 47 2 923 and petition for reconsideration and review What happens if I change my design Like a case board or antenna For certified equipment generally your transmitter the holder of the grant of certification or the holder s agent can make minor modifications to the circuitry appearance or other design aspects of the transmitter Minor modifications are divided into two categories Class Permissive Changes and Class Il Permissive Changes Major changes are not permitted Minor changes that do not increase the radio frequency emissions from the transmitter do not require the grantee to file any information wi
97. ice High frequency clocking rejects the aliasing components to such an extent that they are filtered by the coupling LC network and do not cause any significant disturbance The data modulation is applied through the DATA_IN pin and smoothly applied by specific digital circuits to the carrier Shaping Harmonic components are limited in this process thus avoiding unacceptable disturbance of the transmission channel according to CISPR16 and EN50065 1 recommendations A 55 dB Total Harmonic Distortion THD is reached when the typical LC coupling network or an equivalent filter is used The DAC and the power stage are set in order to provide a maximum signal level of 122 dBuV RMS at the output The output of the power stage TX_OUT must always be connected to a decoupling capacitor because of a DC level of 0 5V_ at this pin which is present even when the device is not transmitting This pin must also be protected against overvoltage and negative transient signals The DC level of TX_OUT can be used to bias a unipolar transient suppressor Direct connection to the mains is done through an LC network for low cost applications However an HF signal transformer can be used when powerline isolation must be performed In reception mode the input signal received by the modem is applied to a wide range input amplifier with AGC 6 dB to 30 dB This is basically to improve noise performance and adjust the signal level so as to ensure max
98. icle discusses the results of this engineering partnership Ember Corporation is a leader in low power wireless networking solutions based on the ZigBee protocol it has developed industry leading solutions for a variety of low power ZigBee devices in addition to security sensors including gas meters door locks and battery powered thermostats iControl is the leading provider of SMA solutions that enable BSPs to roll out next generation services to their customers In addition to contact sensors iControl s SMA Platform integrates a wide variety of ZigBee sensors including motion sensors smoke alarms glass break detectors CO detectors key fobs wireless keypads garage door openers and more Based on the fact that the average residential security system is used for seven years BSPs typically require that contact sensors have a minimum of three years of battery life for an initial product offering and a roadmap leading to battery life spans of seven to ten years Through collaborative development work Ember and iControl have optimized the sensor and radio operations most critical to battery life and have projected a battery life well over three years These results were achieved through iControl s utilization of Ember s 26 industry leading EM357 ZigBee System on Chip SoC fine tuning of iControl s security sensor network operation and software optimizations in Ember s ZigBee software Looking ahead Ember has
99. icult process This range of articles will provide an overview of available technologies for this purpose and how to overcome some technical roadblocks you may face along the way Whether you are looking for a control solution or being able to monitor a sensor within a device and beyond we hope you find this selection of articles valuable Optimizing Security Sensor Battery Life Security sensors are often plagued by short battery life By combining a low power wireless protocol with a low power processor this doesn t have to be a problem Broadband service providers BSPs such as cable and telecom companies are preparing to roll out residential security services based on the ZigBee wireless specification to augment their current voice video and data services ZigBee enables BSPs to offer a range of additional services such as security energy management lighting control and health care applications which are known collectively as Security Monitoring and Automation SMA services Security sensor battery life represents a key consideration in the practicality cost effectiveness and market acceptance of SMA solutions ranking high on a list of factors that includes wireless communication range interoperability certification ecosystem and in field upgradeability The SMA solution developed by Ember Corporation and iControl Inc specifically addresses extending the battery life of contact sensors This art
100. ide Lab services range from basic testing to full compliance testing and filing Our advice Have the lab do as much as possible Taking time to understand the subtleties of the filing process in the middle of trying to get a product to market is a bad idea Saving a little money doing things yourself can end up costing far more than you save and in some cases might jeopardize your ability to receive approval Step two registering When your product is completed and ready for testing a Federal Registration Number FRN must be obtained This is free and can be obtained online Next request a grantee code from the FCC This can also be done online The grantee code costs 60 and must be paid within thirty days of the application Form 159 is used for this and can be done online or printed and mailed Step three testing As previously mentioned the FCC requires that final product testing be done in a registered test facility Here such items as output power harmonics and spurious emissions will be tested This facility will perform separate measurements on the transmitter and receiver as the transmitter and receiver require different types of authorizations from the FCC The testing will usually take less than two weeks but the actual time will depend on the test lab s backlog and schedule It is a good idea to contact the lab well in advance to make them aware of your project and secure a spot in their testing schedule In order
101. identified a host of other software optimizations that will push iControl s contact sensors well into a battery life span of over ten years Basics of iControl s ZigBee based SMA Platform The award winning SMA Platform developed by iControl pairs its open technology agnostic software infrastructure with the industry s only All In One SMA TouchScreen combining an alarm system communications gateway and home automation platform into one device The components include an SMA TouchScreen console a variety of security sensors and easy integration with third party devices such as thermostats lighting controls and door locks Ember s ZigBee software provides the two way wireless networking infrastructure for the entire system as shown in Figure 1 Customer Applications Reference Applications EmberZNet PRO Stack Enhanced ZigBee PRO O D lt D D p D Ember Silicon Figure 1 Ember ZigBee networking software iControl s security sensors At the heart of each iControl security sensor is the Ember EM357 processor which is based on a 32 bit ARM Cortex M3 processor The EM357 is the industry s leading ZigBee processor in both current consumption and radio frequency RF performance tiga TechZ ne Contact sensors are used for door and window security They are either closed or open a general purpose input output GPIO line on the Ember EM357 is used to sense the state of t
102. illion products Our application is designed to help you source the electronic components you need whether you re at work at home or anywhere in between Become a Fan on Facebook Become a Digi Key fan and stay in touch with us on Facebook Read our latest press releases new and featured product highlights as well as contests and promotions Check out our new and featured products highlights Be among the first to find out when a new PTM Online On Demand product training module is available Catch us on YouTube where you will find excerpts from many of our exclusive PTM Online On Demand product training modules as well as our aptly named Another Geek Moment videos These original videos by Digi Key engineers might be just what you need to inspire your next project Ewitter Follow us on Twitter Follow digikey on Twitter to receive daily tweets about new products and supplies news and website enhancements Join us weekly for your chance to win during Monday Mash and Thursday Twrivia www digikey ca wireless 47 Low Frequency Radio in Active RFID Systems Recent enhancements in low frequency receiver design reduce power consumption while improving receiver performance promising to widen the range of applications in which active RFID systems can be implemented RFID Radio Frequency Identification is a popular technology in applications such as asset tracking and logistics support
103. imize power consumption and maximize battery life Display Low cost low power LCD and LED displays in seven segment alphanumeric or matrix format are common user interfaces Regulatory requirements often stipulate that customers must be able to view the billable quantity directly from the meter synchronization Timing synchronization is critical for the reliable transmission of data to a central hub or other collector system to support functions such as data analysis and accurate billing This is essential for a wireless network that has an unpredictable or asynchronous communication protocol In some applications and markets meters are subject to stringent low power requirements For example the service interval for an underground water meter is 20 years or more For these applications specialized lithium battery chemistries such as lithium thionyl chloride or Li SOCI2 with very low self discharge rates are needed to meet the longevity requirement These battery chemistries can be quite costly compared to mainstream battery types Another key requirement for smart meters is the use of high performance yet low power MCUs Most metering systems require MCUs that consume very little power while offering an array of integrated features such as a real time clock analog to digital converter and communications interface More advanced features such as integrated LCD controllers a cyclic redundancy check block or an encryption engine ca
104. imum sensitivity in the ADC An 8 bit conversion is then performed followed by digital band pass filtering to meet the CISPR16 normalization and to comply with some additional limitations met in current applications After digital demodulation the baseband data signal is made available after pulse shaping The RX_IN signal pin is a high impedance input which has to be protected and DC decoupled for the same reasons as with TX_OUT pin The high sensitivity 82 dBuV of this input requires an efficient 50 Hz rejection filter realized by the LC coupling network which also acts as an anti aliasing filter for the internal digital processing In transmission mode the data input DATA_IN is active LOW this means that a burst is generated on the line TX_OUT pin when the DATA_IN pin is LOW The TX_OUT pin is in a high impedance state as long as the device is not transmitting Successive logic 1s are treated in a Non Return to Zero NRZ mode In reception mode the data output DATA_OUT pin is active LOW this means that the data output is LOW when a burst is received The DATA_OUT pin remains LOW as long as a burst is received Powerline isolation Since the TDA5051A connects to the powerline it needs to be isolated from current spikes and noise Figure 2 shows a schematic of the TDA5051A featuring powerline isolation The IC has unique features for a digital powerline communication system The powerline isolation circuitry and the recei
105. in of 2 15 dB over isotropic or dBi dBd 2 15 dB When comparing gains it is important to note whether the gain is being expressed in dBd or dBi and convert appropriately Gain can be a confusing specification Most engineers are familiar with the term in reference to amplifiers where gain is a measure of how much an amplifier increases the input signal But there is a significant difference between an amplifier s gain and an antenna s gain The amplifier puts energy into the system making it an active device An antenna cannot put energy into the system so itis a passive device Gain is commonly misinterpreted as an increase in output power above unity Of course this is impossible since the radiated power would be greater than the original power introduced to the antenna Directivity and gain are closely related Gain is the directivity of the antenna reduced by the losses on the antenna such as dielectric resistance and VSWR In other words it is the product of directivity and efficiency Gain is the most direct measurement of an antenna s real performance As such it is one of the most important specifications Psa taille Directivity Figure 8 Directivity and Gain A simple way to understand directivity or gain is to think of a focusable light source Assume the light output is constant and focused over a wide area If the light is refocused to a spot it appears brighter because all of the light energy is concen
106. inutes IANA D PTM tine Demand www digikey ca ptm www digikey ca wireless 43 A Simple Cost Effective Approach to Home Automation Homeowners have several energy management technologies to choose from but the simplest most cost effective approach is to use the home s existing wiring to create the control network For most homeowners nothing could be simpler or less expensive than using their home s existing wiring to create a control network There s no need for extensive renovations or new wires for the control network and there s no special hardware or software tools to install For these reasons powerline solutions are emerging as a popular approach for in home energy monitoring and control Once the control system is in place the homeowner gets to enjoy several benefits The system can deliver considerable cost savings in terms of energy bills with precise control of lights fans and home appliances and by allowing appliances on the same network to share data communications Plus with a system that includes automated functions events can be initiated and appliances can be turned on and off automatically without user intervention This lets homeowners take advantage of lower utility pricing during off hours and gives greater control over the home environment when the homeowner isn t there Lights can be programmed to turn on and off at specific times and appliances can be configured to track their own op
107. ions and what they mean Figure 7 Isotropic Radiation Pattern There are three radiated specifications that are of primary interest efficiency directivity and gain Often these terms are talked about in the context of an antenna s transmitted signal It is somewhat easier to visualize these concepts by thinking of radiated power but it should be recognized they apply directly to reception as well Efficiency is a measurement of how much energy put into the antenna actually gets radiated into free space rather than lost as heat on the antenna s structure or reflected back into the source The antenna s impedance and VSWR at the center frequency play a big role in this measurement Directivity measures how much greater an antenna s peak radiated power density is in a particular direction than for a reference radiator with the same source power It is the ratio of the power density in the pattern maximum to the average power density at a uniform distance from the antenna In short it is a comparison of the shape of the radiation pattern of the antenna under test to a reference radiation pattern Most commonly the reference would be the perfect spherical pattern of the isotropic model described earlier The units of this measurement are decibels relative to isotropic or dBi A dipole antenna is also sometimes used as a reference in which case the units be stated in dBd meaning decibels relative to dipole A dipole has a ga
108. issued by the FCC directly but now independent laboratories are allowed to issue certification though the Telecommunication Certification Body TCB program which has streamlined the process Following successful testing a report will be produced showing information about the testing and your device A label displaying your FCC ID number along with FCC prescribed information will need to be placed on your certified product The rules for transmitters operating in the 260 470 MHz band are governed by Part 15 231 In some bands the FCC specifies only fundamental power harmonic levels and allowed bandwidth However in the case of the 260 470 MHz band the FCC also considers factors such as the intended application and transmission duration You will want to review the text of 15 231 in its entirety When reviewing this section it is critical to read paragraphs A D as a unit and recognize that paragraph E only applies if the rules of paragraph A cannot be met Given the rules complexity and application dependent nature they are best illustrated in Figure 1 Functional Requirements Once you are certain your application is allowed in principle you will want to focus on understanding the specific functional requirements that must be met in order for your product to receive certification Determine and comply with allowed output power Figure 2 shows the relationship between the fundamental frequency of operation and the allowe
109. isting Energy Profile pages 38 40 www digikey ca wireless 31 Embedded Design Requirements for Smart Metering Systems Wireless transmitters receivers and transceivers are becoming more common in metering systems Smart meters involve some unique design challenges as this article explains The notion of using technology and intelligent systems to enable the efficient use of energy and other resources has become a familiar 21st century theme The term smart metering jumps from the headlines of both mainstream and technical media every day The general public often associates smart metering with intelligent electricity meters used to enable the Smart Grid In reality smart metering is also used to monitor other forms of energy usage such as natural gas and heat i e thermal energy as well as water a vital resource around the world Metering information from residential commercial and industrial facilities is typically sampled at regular intervals and aggregated by a common metering collector before being sent to the service provider Unlike electricity meters gas water and heat meters are powered by batteries and have service life expectations of up to 20 years This creates unique challenges for metering system designers who have to balance the limitations of current energy storage technology with the ever growing power consumption requirements of these more complex systems New system architectures and power m
110. ition performance for this application Practical Guide to High Speed PCB Layout Analog Devices Inc Analog Devices guide to PCB layout comes with a detailed car a schematic or blueprint of properly designed PCBs and offers advice regarding SAR gaa parasitics ground and power re planes packaging and signal ANALOG routing and shielding DEVICES gt PTM OL Ope www digikey ca ptm Technical and Design Support Services Digi Key offers live technical support 24 7 via telephone e mail and live web chat Digi Key s 130 technicians on Staff are trained by manufacturers to answer product specific questions Additionally these technicians cross reference part numbers assist customers in choosing products research and aid in selecting new product and provide access to in depth product specific information as well as specifications and performance data on new products Digi Key s Design Support Services DSS team of application engineers and technicians provides general information and complimentary project specific assistance DSS provides service to engineers ranging from one time contacts regarding product recommendations to ongoing prototype to production design support DSS strives to guide the customer through the design process while achieving the best solutions and ultimately streamlining the design cycle The DSS team provides support and advice on system desi
111. iver during receive or transmit Balun B1 transforms the single ended port impedance of 50 to the 100 differential RF port impedance at pins RFP RFN Configuration It is recommended to configure Antenna Diversity in one of the transceiver states TRX_OFF PLL_ON or TX_ARET_ON Generally the automated Antenna Diversity is enabled with register bit ANT_DIV_EN register OxOD ANT_DIV set In addition the control of the Antenna Diversity RF switch SW1 must be enabled by register bit ANT_EXT_SW_EN register OxOD ANT_DIV In this case the internal pull down of the control pins DIG1 DIG2 is disabled and they feed the antenna switch signal and its inverse to the differential control inputs of SW1 The voltage level of DIG1 DIG2 is equal to DEVDD To actually receive a frame applying the AD algorithm the AT86RF231 state must be changed to RX_ON or RX_AACK_ON Receive diversity procedure Exemplary the function and behavior of the control signals DIG1 DIG2 during receive is shown in Figure 3 1e Ts y ey FTE iy Figure 3 Antenna Diversity Operating Principle during Receive Assuming a frame with a sufficient signal level is available at antenna ANT1 only the AD algorithm selects this antenna while searching for the SHR 1 During the rest of the frame reception this configuration is fixed The selected antenna can be determined by reading register bi
112. ives We wanted to develop an application that could illustrate functioning logic blocks to our end customers in multiple areas from self sustained solar charging to remote communications with various sensors All of the development is being shared in the public domain to jumpstart ideas or reduce our customers development time Given our remote location having some fun with our extreme weather patterns seemed like a natural said John LeDuc Digi Key s manager of Technical Content amp Design Support Services Components from the semiconductor interconnect passive and electromechanical product areas are used in this project to demonstrate the countless options engineers have when it comes to utilizing the products they have purchased from Digi Key s expansive offering Recently the Digi Key Weather Center was updated with a smart charger built with parts distributed by Digi Key which allows the Design Support Services team to control the charger and the loads that are attached to the weather station The purpose of this project is to continually add to it said Tougas We want to update the Digi Key Weather Center with sensors as technology improves and show our customers a variety of ways to connect components and data over the internet This introduction marks the beginning of a series of articles dedicated to the development of the Digi Key Weather Center Additi
113. k The majority of cellular module sensitivity is around 109 dBM therefore the device can sustain another 10 dB in loss on the antenna and transmission lines cable and still reach the operator requirements e This means in theory again we can budget for 4 dB loss for example in the transmission line could be less or more e t leaves us 6 GB in loss for the antenna e This is equivalent to the antenna average gain of 6 dB which is usually possible for the antenna designer to do However in real life TIS is most affected by noise on the board In many cases this noise will totally overpower the underlying GSM signal This noise must either be removed from the system or the antenna placed far enough away from it not to pick it up Of course either way is very difficult to achieve when the design is complete What can Taoglas do to help Designing an optimized RF device depends on many parameters both electrical and mechanical Fortunately Taoglas can utilize our experienced engineers unparalleled range of antennas and real industry experience to come out with a solid reliable process to enable a customer s product to succeed Antenna type layout and design Below are some simple rules to follow for the mechanical dimensions of a product which can pass the strictest operator TRP TIS requirements am sure you are asking yourself how come used mobile phones that clearly violate these guidelines Firstly they may not
114. l time is to increase consumer awareness of consumption both by amount and by time of day The current billing system provides consumers with a single consumption number once a month making it difficult to identify even simple inefficiencies such as a stereo left on or a parasitic wall charger that uses power even when it isn t charging Real time tracking allows consumers to uncover such energy drains by profiling the use of major power appliances in the home If the total unaccounted for usage i e all of the other appliances and electronics in the house is high this will alert consumers to potential areas for improvement through a change in usage habits To provide remote access and other automation features appliances need to have a link to the home network and out to the Internet Candidates to serve as the home network gateway include the smart meter a separately purchased energy monitor or the thermostat because it is already connected to the largest power consuming appliance in the home The home network requires a connectivity technology that is inexpensive simple to use scalable and power efficient Those most commonly associated with Smart Grid applications include www digikey ca wireless 39 ZigBee ZigBee has positioned itself as the defacto smart meter standard claiming to be present in an overwhelming majority of deployed smart meters Offering its Smart Energy and Home Automation Profiles which define h
115. ld be considered Third is export Allowed uses of the 900 MHz band vary outside the US and a products operation may not be legally allowable in other areas Fortunately nearby frequencies are standardized in the large European market Linx offers a selection of footprint compatible products which accommodate domestic and export requirements with just a change of modules and antennas For additional information you may wish to refer to Linx Application Note 129 Check the regulations for each country to which export is desired in order to assure the product will be legal Summary The 902 928 MHz band is highly favorable due to minimal legal restrictions and excellent propagation characteristics It is an ideal choice for analog or digital links especially those that require reliability over long distances or which might be prohibited in other bands For additional information on FCC regulations you may wish to contact the FCC directly Federal Communications Commission Office of Engineering and Technology 7435 Oakland Mills Road Columbia MD 21046 Phone 301 362 3000 Fax 301 344 2050 E mail labhelp fcc gov You may also wish to visit the Linx Technologies website at www linxtechnologies com where a list of testing facilities and applicable sections of FCC regulations are available for review and download Frequently asked questions How can obtain more information on the approval process You may wish to obtain additio
116. mbers calculated TRP For TRP we have to work backwards from the maximum power allowed from a RF module For most cellular modules this is capped by the FCC at 33 dBm for GSM 850 and 30 dBm for GSM 1900 www digikey ca wireless 7 Let s take a specific example Usually the module will be set at a slightly lower power rating than maximum allowed This would mean at GSM 850 with a power level of 32 dBm this leaves us 10 dB of loss in the device to still pass the 22 dBm target This sounds like plenty of margin but there are a lot of losses in the system As the RF signal passes down a cable or a transmission line on the device board it easily loses 4 dB or more 4 dB loss is more than half the loss of the original power coming from the module e When the signal reaches the antenna and is radiated out into the air it will also inevitably lose more e So 32 dBm 4 dB 28 dBm meaning we need to reduce the loss from the antenna side to 6 dB or less e This 6 dB loss is equivalent to saying the antenna has an average gain of 6 dB e Therefore we need to design an antenna that has better than average gain of 6 dB for the device to reach the TRP performance required TIS For TIS a similar calculation can be done For example knowing that a network operator for GSM 850 has set a signal strength of greater than 99 dBm we can work backwards to what losses are allowed in the device for the device to still operate on the networ
117. mething that is more practical for a portable product The answer is quite a bit Generally if the radius of the counterpoise is longer than one wavelength the performance is close to that of an infinite counterpoise lf the radius is shorter than one wavelength the radiation pattern and input impedance are compromised Significant performance reductions occur when the radius is a quarter wave or less In Figure 10 the graphs show the performance of a 916 MHz antenna that has been tuned to a 4 x 4 ground plane counterpoise Graph A shows the antenna measured on the 4 x 4 ground plane Graph B shows the antenna measured on a 26 5 x 26 5 full wave ground plane Looking at the VSWR graphs it can be seen that a larger ground plane will lower the resonant frequency and widen the bandwidth In this case the wider bandwidth offsets the drop in frequency so that the VSWR at the intended center frequency is still less than 2 0 1 Lii an gaf giiir A Si FAT Vi leip B CENTER PERCH EPIN 800 000 O00MHe Figure 10 A 916 MHz antenna VSWR on A a 4 x 4 ground plane and B a 26 5 x 26 5 ground plane 14 Conversely if the antenna had been tuned to the larger plane then placed on the smaller one the center frequency would have shifted higher and the bandwidth would be smaller This could result in a VSWR that is out of specification This effect would be magnified with helical antenn
118. n Certain bands within the RF spectrum are available for unlicensed operation The term unlicensed is often misunderstood The manufacturer of a product designed for unlicensed operation is not exempt from testing and or certification Indeed both the transmitter and receiver must be tested by a qualified testing laboratory However once this has been done and any necessary approvals received the end user of the product can then operate it without obtaining a license for its use tem TechZOne Receiver procedure The approval procedures for transmitters and receivers are quite different The receiver is considered an unintentional radiator and is subject to authorization under the Declaration of Conformity process This is a simple process in which an accredited laboratory tests the product to ensure that the equipment complies with FCC standards The test results should be maintained within your files but an FCC filing or submittal is not required unless specifically requested pursuant to Section 2 1076 Following successful completion of this process the end product should be labeled as prescribed by the FCC Transmitter procedure The transmitter is an intentional radiator and subject to certification Certification testing should be performed by properly approved laboratory In most cases you do not need to be present for testing and your chosen laboratory will prepare the filing paperwork Certifications were once
119. n reduce the MCU s processing burden enabling it to reside in low power modes for long periods of time and reducing overall system power ARLALCHS PERIPHERALS 10 b ae CE E ssaa O TEAAP Tie vG 24 5 Mec PRECISION INTERMAL OSCMLLAT CH Figure 2 Silicon Labs Si10xx wireless MCU provides a control and connectivity solution that combines an ultra low power MCU core with a sub GHz wireless transceiver Wireless transmitters receivers and transceivers are becoming more common in metering systems Key features include high levels of integration very low power operation fast start up from low power states high receiver sensitivity greater than 118 dBm and high transmit powers without external power amplifiers up to 20 dBm More advanced features include automatic packet handling integrated FIFO and variable frequency and modulation schemes Wireless MCUs see Figure 2 that combine the MCU with a wireless transceiver are also available for smart meter applications These highly integrated single chip devices can help reduce BOM and system cost while providing a low power embedded control solution capable of high performance wireless connectivity Other key technologies for next generation metering systems are wired access products such as modems for line based data communication timing solutions for network synchronization and CMOS based digital isolation products for safety and compliance of electrical me
120. nal literature and application notes from Linx by visiting our website at www linxtechnologies com You may also visit the FCC s website at www fcc gov email them at fccinfo fcc gov or call them at 1 888 CALL FCC Where can obtain a copy of the FCC Rules and Regulations The Rules and Regulations can be found online at http www fcc gov searchtools html rules CFR Title 47 Parts 2 and 15 cover the use of Linx products Excerpts from these parts are contained in this document For a paper copy you should go to the Government Printing Office s website at http bookstore gpo gov and indicate that you need a copy of Title 47 of the Code of Federal Regulations 47CFR If your need is for equipment authorization you will require Volume 1 which contains Parts 0 19 Their telephone number is 866 512 1800 and email is ContactCenter gpo gov You can also contact the Government Printing Office GPO in your local area for a copy of the rules The telephone number for the GPO in your local area can be obtained from your telephone directory or operator listed under the Federal Government www digikey ca wireless D0 wish to locate a test laboratory in my area Is there a list of laboratories in my area The FCC Laboratory makes available such a listing and it is updated monthly This information is online How long will it take to receive an approval The testing will depend on the current backlog of the test facility that you c
121. nce which increases its impedance at high frequency This will result in the ground plane floating somewhere above ground at RF frequencies which will reduce the performance of the antenna and consequently the range of the product When running traces on the ground plane layer try to present the smallest profile to the antenna which is normally the width of the trace This means running traces away from the antenna rather than across the board Figure 14 provides an example This board uses a quarter wave monopole antenna that is mounted in the same orientation as the ground plane The top layer is in red and the bottom layer is in blue Almost all of the bottom layer traces are running away from the antenna up and down rather than across its resonant path left and right The one through hole component SM1 is also running away a ge iE aa fe i t Figure 14 PCB Layout 16 from the antenna Looking at the board from the perspective of the antenna there are very wide paths from the antenna to the battery B1 This will mean a good low impedance ground connection for all of the RF stage which will maximize the RF performance The ground plane also allows for the implementation of a microstrip line between the RF stage and the antenna This term refers to a PCB trace running over a ground plane that is designed to serve as a transmission line between the module and the antenna A transmission line is a me
122. nd the RF transceiver Innovations in each of these subsystems have enabled smart appliance manufacturers to integrate wireless communications capabilities into their products Along with these innovations come design challenges such as choosing the appropriate encryption algorithm and ensuring that the wireless networks in which these devices operate can be scaled upward as demand for the devices grow Both consumers and manufacturers stand to benefit from these new wirelessly enabled smart appliances as entities such as utility companies offer useful cost saving products and services based on these devices The Google PowerMeter and load control services are two such examples with many more such services becoming available every day Component Solutions for Smart Meter Applications AVX Corporation AVX s guide to component solutions for smart meter applications reviews the need to upgrade oe power grids with ea re reece smart metering SES technology It also presents a high level overview of smart meter systems and explains how AVX products can support engineers in this process The guide features figures depicting how AVX component solutions can work for household systems and industrial systems and detailed photographs and descriptions of smart meter interconnect products that allow for communication of data to data center The guide is 21 pages in length and can be viewed with or without audio in approximately ten m
123. netic Compatibility EMC using the EN 301 489 series of standards and Safety per the EN IEC 60950 and EN 61010 standards are also mandatory requirements for most radio devices deployed are the globe www digikey ca wireless Understanding Antenna Specifications and Operation The antenna is one of the most complicated aspects of RF design and specifications on an antenna s data sheet will not necessarily reflect its performance in the final product Understanding how antennas work in the real world will help to dispel much of the mystery The antenna is probably the most overlooked part of an RF design The range performance and legality of an RF link are critically dependent upon the antenna However it is often left until the end of the design and expected to fit into whatever space is left no matter how unfavorable to performance that location may be Many of these designs will have to ultimately accept degraded performance or go through multiple redesigns With so many interdependent variables antenna design becomes as much art as science Engineers delving into RF design for the first time can easily confuse or misinterpret the meaning of antenna specifications and how to apply them For instance the gain of an antenna is very different from the gain of an amplifier The most common misconception may be that the radiation pattern on a monopole antenna s data sheet will be that of the antenna on the final pr
124. nt Printing office or the FCC website What is Unlicensed operation Certain bands within the RF spectrum are available for unlicensed operation The term unlicensed is often misunderstood The manufacturer of a product designed for unlicensed operation is not exempt from testing and or certification Indeed both the transmitter and receiver must be tested by a qualified testing laboratory However once the necessary approvals are received the end user can then operate the product without further obligation or licensing Steps to Part 15 certification Choose the optimum operating frequency Part 15 governs a broad range of the radio spectrum ranging from below 1 MHz to in excess of 32 GHZ It is broken into individual 50 sections that govern the use of specific frequencies and bands For example section 15 249 covers the 902 928 MHz band In this frequency range a user is allowed to transmit any analog or digital signal they desire so long as the stipulations governing allowed output power harmonics and occupied bandwidth are met Other sections are not so accommodating For example in the 260 470 MHz band the FCC considers not only RF factors but also the intended function and application In order to determine which operational frequency is best for your product it is necessary to weigh both technical and legal issues First you will want to have a clear understanding of which frequencies are legall
125. nt footprint and pin out over several generations of integrated circuits to guard against the need to re spin or redesign a wireless product to accommodate an IC that is no longer available RF modules extend the product life cycle of any wireless product New Revolutionary Software Alternatives The time or software resources required to learn network stacks and develop applications is daunting and expensive Panasonic has partnered with several software developers for all of the major network protocols including Bluetooth From fully developed Bluetooth profiles to flexible AT commands Panasonic can deliver an RF module with the firmware needed to make any project a success Wireless Solutions For Less RF modules can reduce the total cost of ownership for product development projects up to 50 000 units per year Designing in an RF module rather than a discrete wireless solution can reduce expensive development test certification and production resource requirements New Bluetooth RF Modules Bluetooth which is based on IEEE 802 15 1 was developed for the purpose of sending larger amounts of data quickly from computers to PDAs to cell phones or other portable handheld devices Key features include high data rate frequency hopping very small form factor and modest power consumption Panasonic offers a new Bluetooth RF module product line that makes connectivity between mobile devices such as cellular phones and small button cell battery
126. ntinuously In terms of power then the LF receiver is the most important element since it is the only element that must always remain active Sensitivity is another key parameter of the LF receiver as the signals in the target applications might be attenuated by distance and physical obstructions For active tags the requirement for battery life is three years minimum from a simple coin battery such as a CR2032 This constraint implies that the tag s current consumption should be limited to little more than the battery leakage current while in receive mode This in turn makes the choice of the operating frequency extremely important To achieve the low power requirement the receiver must operate at lt 300 kHz RFID systems today typically use the 125 kHz or 134 kHz frequencies This then generates the first challenge in the radio implementation at such low frequencies the wavelength is large requiring a correspondingly large antenna Successful designs use loop antennas which only sense magnetic fields H A loop antenna is essentially an wa TECHZONe inductor made up of coils of ferrite rods As Figure 2 shows the LF transmitter in the base station and the LF receiver in the tag together work like a transformer where the inductor at the transmitter is the primary coil and the one at the receiver is the secondary coil Primary Coil Secondary Coil Figure 2 A transmission scheme using magnetic coupling In order t
127. ntrol are committed to working together with the goal of achieving security sensor battery life in excess of ten years in the near future Further inquiries on the practical and technical considerations of deploying a full featured home security system on an SMA Platform are welcome For more information contact either Ember or iControl directly wa TECHZOnNe Using Third Party IP Protocol Stacks in M2M Designs Instead of requiring developers to write new control code for each new IP protocol stack Multi Tech s Universal IP is a single implementation that is applied uniformly across multiple modems that implement every major communications technology When TCP IP functionality is employed in the embedded world it is generally to enable machine to machine M2M communications In many applications such as fleet tracking and remote monitoring the physical medium for the internet connection will be a cellular wireless network but equally some embedded applications might access the internet via Wi Fi or a wired Ethernet link The implementation of an internet based M2M system will typically consist of on one side a chipset baseband and transceiver in which the baseband runs a version of the TCP IP protocol stack and on the other an applications processor or microcontroller which runs software to execute protocol commands via an applications programming interface API Embedded developers are familiar with the pres
128. o antennas During synchronization header SHR search the radio transceiver autonomously switches between the two antennas without the need for microcontroller interaction if the AD algorithm is enabled To ensure highly uncorrelated receive signals on each antenna the antennas should be carefully separated from each other refer to the section Multipath Propogation Characteristics lf enabled and when the AT86RF231 is set into a receive state the automated AD algorithm works as follows On detection of an SHR with a sufficient high signal level on one antenna this antenna is locked for reception of PHR and PSDU In this case no further attempt is made to determine the signal level on the other antenna Otherwise the SHR search is continued on the other antenna and vice versa After the completed reception of a frame indicated by an interrupt IRQ_3 TRX_END the diversity search algorithm is continued until a new SHR header is detected or the receive state is left Application Schematic Figure 2 illustrates the AT86RF231 Application Schematic concentrating on Antenna Diversity ANTO Mm oies AT86RF231 ANT1 Figure 2 AT86RF231 Antenna Diversity Application Schematic 20 ma TeCHZOnNe Two antennas ANTO and ANT1 are connected via an RF switch SW1 to a balun B1 A differential control pin pair DIG1 DIG2 selects one of the two signal paths within SW1 to connect one antenna to the radio transce
129. o increase both the magnetic field generated by the transmitter and the voltage picked up by the receiver both coils are tuned with capacitors in order to resonate at the carrier frequency This resonator can be damped using a parallel resistor to increase the bandwidth of the antenna Effective tuning is one measure that increases the sensitivity of the LF receiver but the use of loop antennas poses another problem Since the antennas sense a magnetic field the orientation between the base station transmitter and the receiver has an important effect Electromagnetic theory dictates that if the two coils show a 90 degree phase shift in space Figure 3 the induced voltage on the secondary coil is in theory zero Figure 3 In magnetically coupled systems the induced voltage is zero when the Rx antenna is phase shifted by 90 degrees In some precisely controlled applications the mutual orientation between the transmitter coil and the receiver will be fixed and predictable here effective communication is assured so long as this fixed position has the reader s antenna and tag s antenna parallel to one another during the reading phase If the mutual orientation is not fixed and predictable the receiver requires a three dimensional antenna array comprised of three antennas orthogonal to each other Figure 4 The combination of carrier frequency tuning and three dimensional antennas described here not only extends the receive range it
130. o plan for international compatibility Band allocation and regulations vary from country to country For additional information you may wish to refer to Linx Application Note 129 Common frequencies within the band and their uses As you review Linx product offerings you will notice three standard frequencies within the 260 470 MHz band These frequencies are 315 418 and 433 92 MHz e 315 MHz is commonly used for gate garage door openers security and keyless entry systems e 418 MHz is a very clean frequency here in the US and also appropriate for operation in Canada e 433 92 MHz is used throughout all of Europe While it is allowable for use here in the US and Canada interference from amateur radio the nearby pager band and active RFID tags may sometimes pose a problem Summary The 260 470 MHz band is ideal for transmitting control command or status signals It should also be given consideration for control signals accompanied by data such as time temperature or pressure 54 Considerations for operation within the 902 928 MHz band Introduction This section is designed to give the reader a basic understanding of the legal and technical considerations for operation of RF devices in the 902 928 MHz band The use of these frequency bands varies considerably worldwide so it should be recognized that this application note is intended for designers utilizing Linx RF modules and planning for operation within the Unite
131. ocessing time T Transmit time T x Measurement Frequency F The average power P is simply the total power P x D the standby power which is generally small enough to be ignored Table 1 Typical Power Requirements for Microcontroller and RF Link re Processing Current Sleep Current RF Link 20 30 mA for 1 10 ms Table 2 Typical Energy Sources and their Power Capabilities Energy Harvesting Source Typical Power Range x Solar indoor outdoor single cell 10 pW 40 mW cm 0 6 0 8 Vibration piezo 4 uW 100 W cm 0 8 0 9 Thermal TEGs 25 uW 10 mW cm 0 3 0 5 www digikey ca wireless 61 For example let s assume we are tasked with designing an autonomous indoor temperature sensor This sensor will be deployed throughout a large office building and coupled with proximity sensors that can detect when a room is occupied and adjust the temperature accordingly Deploying this type of sensor within a large building can reduce the annual heating and cooling costs significantly The sensors require 500 pA at 3 3 V for 2 ms to measure temperature and detect an occupant A low power microcontroller needs to operate on this data for another 5 ms The microcontroller consumes 3 mA at 3 3 V when processing the data Finally the RF link requires 30 mA at 3 3 V for 30 ms to transmit the data The desired measurement frequency is 0 2 Hz one measurement every five seconds D Ta T T F 2 ms 5 ms 30 ms 0 2 Hz
132. oducing a very low voltage low impedance output or a very high voltage high impedance output The various elements in this system can be further broken down into power producers regulators transducer and power management and power users everything else If the energy harvesting average output power capability exceeds the average power required by the remote sensor electronics then you have the possibility for an autonomous system ENERGY SOURCE PIEZO TEG ETC Figure 1 Typical Wireless Sensor System Before any design is initiated it is worthwhile to run a quick feasibility analysis This will quickly determine whether energy harvesting techniques are practical The first step is to decide how often measurements need to be made and transmitted We will call this measurement frequency F Next we can determine how much processing power is required for the sensor signal conditioning data conversion and processing to generate the desired data plus the RF transceiver power and time required to transmit this data Table 1 shows the typical power requirements for a popular microcontroller and RF link system The power requirements can vary from manufacturer to manufacturer and for the particular application There are many choices that can be optimized based on the end application From this we can calculate the system duty cycle and average power The duty cycle D of the system is defined as Measurement time T_ Pr
133. oduct In actuality the radiation pattern for a quarter wave monopole antenna is so critically dependant on the design and layout of the product that manufacturers gain specifications and radiation pattern plots have little use except to ascertain potential antenna performance Since voluminous texts have been written about each of the many antenna styles it is unnecessary to cover them all here This article will focus only on those styles which are commonly used in low power handheld products dipole and monopole whips These styles cover a wide range of available antennas and are among the most common to be implemented incorrectly With that in mind there are several rules of thumb that can be applied to antenna designs These rules are less how to design an antenna and more how to design with an antenna Antenna fundamentals An antenna is a device that converts electric currents into electromagnetic waves and vice versa It can be considered a complex RLC network At some frequencies it will appear as an inductive reactance at others as a capacitive reactance At a specific 10 frequency both of the reactances will be equal in magnitude but opposite in influence and thus cancel each other At this specific frequency the impedance is purely resistive and the antenna is said to be resonant Here is where the physical meets the theoretical Resonance will occur at whole number multiples or fractions of the freq
134. olution with more than 10 years experience e Long range e High local system density e Very fast connection e Low latency e Simple star typology e Low power consumption e Free of charge technical specifications e Test support system through the Bluetooth SIG SORT BY PRICE Digi Key s Sort by Price feature makes it easier for engineers and purchasers around the world to purchase top quality product from Digi Key Sort by Price is based on tier 1 or unit pricing and applies to all parts all of Digi Key s 82 international websites and all Digi Key supported currencies Customers are able to sort by price in ascending or descending order in addition to applying filters for product in stock lead free product and RoHS Compliant product An Advanced Sort option is also available and allows customers to request parts in specific quantities Customers can view pricing of products from Digi Key s vast line card of suppliers at a glance and choose the parts that best fit their particular needs jm TechZGO Energy Harvesting for Wireless Sensor Networks Wireless sensor networks require careful attention to power management if they are to meet their objectives in the field Integrating energy harvesting techniques into your design can go a long way toward addressing the problem The increasing accessibility and performance of power miserly sensors microcontrollers and RF transceivers is raising th
135. on the first attempt Wireless products are regulated in each country by slightly different standards Taoglas in co operation with certified test labs can advise on the exact regulations a product must conform to and provide a test plan In Table 1 are targets to reach for passing most but not all operator TRP TIS approvals Some operators have specific targets for certain products or applications so you need to confirm individually In any case these are the numbers any designer should target for their device Table 1 TRP and TIS performance targets all figures in dBm Aaawiruen Milaximurm Londucted Conducted Power Sensitivity GSM 850 33 22 105 99 GSM 900 33 23 109 100 GSM 1800 30 24 109 101 GSM 1900 30 24 5 109 101 UMTS HSPA HSPA WCOMA 850 23 13 109 97 UMTS HSPA HSPAs WCDMA 1700 23 18 5 109 101 UMTS HSPA HSPA WCDMA 1900 23 18 5 109 101 UMTS HSPA HSPA WCOMA 2100 23 18 5 109 101 If your operator does not have a stated standard or their standard is not mandatory it is advisable to aim for these or higher numbers in order to accomplish the best industry standard Your product can in many cases still function normally below these values there is no industry set cut off for operation It will depend on the actual application environment and your own conditions for what is acceptable in terms of reliability and the outcome of your own product field tests How are these TRP and TIS nu
136. onal articles focusing on the various components in the Digi Key Weather Center and how they were implemented will appear in future issues of the Microcontroller Sensors Lighting and Wireless Solutions TechZone Magazines _ Z ne Once the structure was assembled and powder coated the components were placed onto the structure The first component was the solar panel Parallax 750 00032 ND The structure faces due south the ideal direction to obtain the most solar exposure The solar panel is connected to the main control box using weatherproof connectors Ay TER cEv ERE EEREN ae i ee Smar TETIT F The battery charger board uses a Texas Instruments BQ2031 lead acid fast charge IC Circuitry is based on Tl s DV203182 lead acid charger development board and configured for a 6 cell battery using the two step voltage charging algorithm Fast bulk charge voltage is set for 14 9 V and maintenance float voltage is set for 13 7 V The input power for the charger is provided by the solar panel which outputs approximately 20 V 0 5 A under full sunlight conditions The main control box Bud Industries 377 1139 ND In July 2010 the Digi Key Weather Center was placed which houses the batteries and charge circuit was on the roof of Digi Key s 600 000 square foot facility in mounted next Thief River Falls Minnesota a wi Once the structure was securely anchored to the building In N
137. oncavallo austriamicrosystems Most implementations of long range RFID have used UHF readers operating in the 915 MHz frequency band combined with passive tags This article examines recent enhancements in low frequency receiver design that reduce power consumption while improving performance and expanding the range of applications in which active RFID systems can be implemented The FCC Road Part 15 from Concept to Approval 50 contributed by Linx Technologies The need for FCC approval has put a lot of manufacturers off from making their devices wireless This is unfortunate and unnecessary The issue of legal compliance for the finished product is straightforward when approached in logical steps Bluetooth Low Energy for Wireless Sensors and Actuators ccccsssssssecccccsssssseeeeeeeeees 57 by Rolf Nilsson connectBlue With so many low power wireless protocols to choose from why do we need another Because the existing technologies are too expensive too slow or consume too much energy for wireless sensor applications Energy Harvesting for Wireless Sensor Networks 61 by John Bazinet and James Noon Linear Technology Corporation Energy harvesting techniques can supplement or replace batteries in remote wireless sensor networks though they need to be carefully integrated into your design With all of the necessary elements in place semi or fully autonomous remote sensor networks have left the t
138. onsider the lighting automation industry Controlling every light in a house remotely has been possible for over a decade High end systems offer features every consumer would love to have just not at a price most can afford or are willing to pay X10 technology provided a cost effective approach to lighting automation but its unreliability has left consumers unexcited As a result the home lighting automation market has experienced limited growth With the development of Smart Grid technology the focus is first and foremost on enabling significant cost savings by intelligently monitoring and managing power consumption For a few dollars more appliances will be able to accurately measure power consumption and turn themselves on and off based on power availability and time based pricing tiers As the Smart Grid is deployed however it will also bring with it an infrastructure that will readily support a wide range of automation capabilities The best candidates for intelligent power management are those appliances which consume a lot of power and are fairly discretionary as to when they are used The primary consumer of power within the home and business is typically the HVAC Heating Ventilation A C system followed by appliances with motors and power supplies such as washers and dryers Items like refrigerators and stoves may consume power but are not discretionary in their use so the need for them to be smart is much less pertinent
139. or another without redesigning the board they can also use the same application code to control the modem across all product variants 30 Figure 2 Multi Tech Systems implements the Universal Socket pinout across all SocketModem devices such as this SocketModem iCell intelligent embedded cellular modem Moreover Multi Tech is committed to maintaining a stable Universal IP API over the long term This means for instance that OEMs can remain blind to underlying chipset changes Just like embedded users of cellular modules Multi Tech has to periodically redesign its modems when a chipset goes obsolete but users of Multi Tech modems see no difference because the Universal IP API always stays the same as does the Universal Socket pinout The Universal IP stack implementation depends on the hardware architecture of the modems in a cellular chipset the IP stack is hosted on the baseband which is the proprietary design of the chipset manufacturer When the baseband changes so does the IP stack and users cannot control it In Multi Tech s Universal IP products the protocol stack is hosted on a discrete processor separate from the cellular chipset see Figure 3 Since Multi Tech has total control over the processor and the software it runs it can ensure that its interface to the user s system controller remains stable over time and over a complete range of modems The result is that the interface between the application and
140. or non infringement Digi Key cannot guarantee and does not promise any specific results from use of any information contained in this magazine Any comments may be addressed to techzone digikey com Editorial Comment M2M communication is exploding in all industries and demographics consumers have come to expect little or no service equipment disruptions or spotty connectivity Regulatory changes are driving adoption in many regions and countries including the European Union Brazil and China AB Research estimates that the WWAN M2M Module market will increase over 200 to 114 million units shipped by 2015 M2M designers are challenged by complex design cycles and strict regulatory approvals Given the inherent design challenges and strong end customer demand for wireless solutions the timing is perfect for this issue of TechZone magazine on M2M communications Mark Zack Director Semiconductor In this issue we delve into all facets of M2M communications and how to overcome typical technical roadblocks You will find a great selection of articles that will support your M2M design decisions including e Understanding Antenna Specifications and Operation an interesting article about real world antenna performance contributed by Linx Technologies page 10 e Optimizing Security Sensor Battery Life an article on combining low power wireless protocol with a low power processor contributed by Ember Corporation page
141. ots coming from different manufacturers difficult In addition the plot for a specific design will likely vary from that of a reference design Pattern plots typically consist of a polar coordinate graph though Cartesian coordinate graphs are also used Polar plots are easier to visualize as they show the radiated power 360 degrees around the antenna under test Generally a logarithmic scale is used which allows a range of data to be conveniently shown on the same plot Two plots are created one in the horizontal axis and one in the vertical axis Together these give a picture of the three dimensional shape of the radiation pattern as demonstrated by Figure 6 Figure 6 Polar Plots of an Antenna Radiation Pattern An antenna s radiation pattern and specifications related to it often need a point of comparison or reference Most frequently a theoretical antenna called an isotropic antenna or isotropic radiator is used for this purpose The term iso means the same tropic means direction Thus isotropic describes an antenna which radiates electromagnetic energy the same in all directions The isotropic antenna and its perfect spherical pattern are only theoretical and do not actually exist but the model serves as a TD TechZ ne useful conceptual standard against which real world antennas and their specifications can be compared Now it is time to take a closer look at some of the most important radiated specificat
142. ovember 2010 the Digi Key Weather Center was the charger and battery were added to the control box updated with brackets to hold two more solar panels making it possible to view most of the southern hemisphere to collect as much solar energy as possible This is our version of solar tracking 4 D Digi Key s Weather Center The Digi Key Weather Center was developed to demonstrate connectivity to customers by using products available and supported by Digi Key Placed on the roof of Digi Key s 600 000 square foot facility in Thief River Falls Minnesota in July 2010 you can track the most dramatic of weather changes year round A collaborative effort by members of Digi Key s Design Support Services team find out more detail for yourself online at connectivity digikey com www digikey ca wireless 65 uv sS diil Sne Tech One prenn G Birgjar SECRSCEATRPLLED SO TS Adopt LEDs Save 120 Bi ia 4 Look Inside Today s ra i Is 3 zj rge n a Hei 7 m D H 0 oller Te wi PEP oe 2 aul L i l ci E OigiKoy CORPORATION The industry s broadest product selection available for immediate delivery 1 800 344 4539 Digi Key is an authorized distributor for all supplier partners New products added daily 2011 Digi Key Corporation 701 Brooks Ave South Thief River Falls MN 56701 USA Answers for TechZone Trivia crossword on page 31 Across 3 minimized 5 con
143. ow appliances communicate to the meter and each other see Figure 3 ZigBee simplifies integration into the home network C2 ZigBee Smart Energy Ge 2 Home Area Network y ZigBee Utility Company Programs Electric Gas Water Figure 3 ZigBee s Smart Energy Profile provides an efficient way of connecting appliances within the home through the smart meter and allowing consolidation of energy data by utility companies Wi Fi As a wireless technology Wi Fi has a huge installed based is readily available in most homes as an Internet connection and is familiar to consumers Connecting to a Wi Fi enabled appliance is about as complicated as configuring a wireless printer In some circles however this is thought to be too complicated and a technology is desired that requires no configuration Powerline Communications PLC PLC provides a wired connection for appliances Since it runs over powerlines all major appliances are already connected to the smart meter Proprietary Proprietary wireless connections tend to support automatic configuration and can be less risky to introduce to market However they require more hardware cost more than standard technologies and tend to have limited extensibility From a technology perspective there is no obvious winning technology Many of today s silicon vendors offer a variety of connectivity interfaces off the shelf All of the required software h
144. power management circuit has a R near 2 5 Q then the maximum power available to the power converter input is 180 mV 2 5 Q x 4 3 24 mW Our power converter constant K is 0 4 so the total power available to the remote sensor 3 3 V output is 3 24 mW x 0 4 1 3 mW Since 1 3 mW is comfortably above the previously calculated Pa of 818 uW we can generate enough power to operate A power management circuit to convert the very low output voltage of the TEG to the required 3 3 V is the next challenge A further complication is that the input voltage TEG output can be either positive or negative 180 mV depending on whether the duct surface is hot or cold While it may be possible to develop a discrete circuit to meet this challenge it is often very difficult to achieve a solution that meets the system requirements for manufacturability small size tex TeCHZOne and reliability Further circuit design is extremely sensitive to stray capacitance and the entire circuit needs to be micropower to achieve the rated K factor Fortunately an integrated solution exists today An example circuit using the LTC3109 is shown in Figure 5 The LTC3109 can operate from inputs as low as 30 mV and will produce any of four pre programmed output voltages V ur 2 35 3 3 4 1 or 5 V A switchable V is provided to power the sensors only when necessary The LTC3109 also includes a power manager that is useful for storing and utilizing excess harveste
145. ption of service conditions Gas and water meters Figure 1 are generally battery powered systems that include a microcontroller MCU that interfaces to a metering sensor display and communications block typically a wireless transmitter or transceiver These systems often use positive displacement flow meters to measure the number of times a unit volume of the fluid moves through the meter For viscous fluids volume is measured by a magnet or shaft that rotates Each revolution is converted to an electrical signal and accumulated by the MCU Less viscous fluids such as natural gas might rely on ultrasonic transducers to measure mass flow Regardless of the material that is measured low power consumption is a critical design requirement in these metering systems which typically are not wired to an electricity source Gas Woater Meter Lore Voltoge Detection Circuit Figure 1 Example of a smart gas water meter system based on the Si10xx wireless microcontroller which includes a high performance sub GHz wireless transceiver Thermal energy meters heat meters and heat cost allocators are typically installed in multi tenant buildings that rely on centralized heating systems These meters measure the amount of heat being delivered to a location in a given period of time Like gas water meters thermal energy meters are battery operated systems optimized for the lowest overall system power They also contain an MCU that measure
146. r Basic and Extended Operating Modes Dynamic and static antenna selection Even without using the automated AD algorithm one antenna can be selected permanently This may be useful if the Antenna Diversity selection is performed using another control entity than the PHY www digikey ca wireless 21 To select one antenna permanently the antenna has to be configured using register bits ANT_CTRL This setting defines the antenna for a transmission as well as for reception The AD algorithm shall be disabled register bit ANT_DIV_EN 0 and the control of RF switch shall be enabled register bit ANT_EXT_SW_EN 1 Antenna diversity sensitivity control Due to a different receive algorithm used by the AD algorithm the sensitivity of the receiver has to be adjusted To achieve this it is recommended to set register bits PDT_THRES register Ox0A RX_CTRL to 0x3 lf the AD algorithm control is disabled and one antenna is permanently selected using register bits ANT_CTRL the register bits PDT_THRES shall be reset Register Description Register 0x0A RX_CTRL The RX_CTRL controls the sensitivity of the Antenna Diversity Mode ie Dalla M RX_CTRI Aradin Hatti Vaii E 3 2 aA Reade PUM RAN RUN Fitoi V ai a 1 1 e Bit 7 4 Reserved e Bit 3 0 PDT_THRES These register bits control the sensitivity of the receiver correlation unit If the AD algorithm is enabled the value shall be set to PDT_THRES 3 other
147. r words a small coin cell such as a CR2032 is enough for 5 10 years of operation Cost and backwards compatible In order to be backwards compatible with Classic Bluetooth and to be able to offer an affordable solution for very inexpensive devices the chipset is available in the following two versions Figure 1 l Figure 3 Out of the three advertising channels and the 37 data channels the three e Dual mode Bluetooth low energy technology as well as Classic advertising and nine of the data channels are located between the three Wireless LAN Bluetooth functionality channels in the 2 4 GHz band e Stand alone Bluetooth low energy technology only in order These features also make Bluetooth low energy technology coexist to optimize cost power consumption and size which are smoothly with other wireless technologies in the 2 4 GHz band as particularly useful for small battery powered devices Bluetooth technology does not use frequencies that are occupied by other radios in the neighborhood In addition there is also a possibility to apply the principle of not using designated channels via the so called channel blacklisting Figure 3 Ease of use and integration The technology uses a simple star topology which simplifies the implementation work significantly This topology fits very well with i common used system architecture with a number of smaller devices Figure 1 Bl
148. ral node Mesh or peer to peer networks enable high degrees of reliability They consist of a variety of nodes placed as needed and nodes within range being able to communicate with each other to form a mesh Messages may be routed across the network using the different stations as relays There is usually a choice of routes that can be used and this makes the network very robust If interference is present on one section of a network then another route can be used instead Finally there is what is known as a cluster tree network This is a combination of star and mesh topologies For RFID do all countries use the same low high and ultra high frequencies Most countries have assigned the 125 kHz or 134 kHz area of the radio spectrum for low frequency systems with 13 56 MHz being used around the world for high frequency systems However UHF RFID systems have only been around since the mid 1990s and countries have not agreed on a single area of the UHF spectrum for RFID Europe uses 868 MHz for UHF while the U S uses 915 MHz Until recently Japan did not allow any use of the UHF spectrum for RFID In 2003 they opened up the 950 to 956 MHz band for RFID Many other devices use the UHF spectrum so it will take years for all governments to agree on a single UHF band for RFID Governments also regulate the power of the RFID readers to limit interference with other devices Some groups such as the Global Commerce Initiative are trying to en
149. rate plane offers various possibilities in the configuration of the two antennas as shown in Figure 7 The first and the second example using different polarization planes Here the antennas are placed with an angle of 90 degrees to each other The advantage of the second configuration is a higher symmetry which makes antenna matching and board layout easier The third antenna placement is a symmetric configuration however does not support polarization diversity Additional Notes e The RC components placed between pins DIG9 10 and the RF switch filter possible transient switching noise of the AT86RF231 control pins to avoid coupling into the antenna paths The RC filter consists of R1 C3 R2 C4 e RF switch SW1 is recommended to have low insertion loss typ lt 1 dB and high isolation typ gt 20 dB No DC path should exist in the antenna paths to make switching with single ended positive voltages possible refer to the RF switch datasheet e The antenna paths are grounded coplanar lines with a characteristic impedance of 50 ohms e The SW1 switching time to select one antenna should be below 1 us Table 6 AT86RF231 AD REB RF Section Bill of Material BoM e oe Designator ANTO ANT1 Ci C2 C3 C4 R1 R2 Resistor AT86RF231 802 15 4 2 4 GHz Radio Transceiver refer to WE748421245 SMD BALUN Wurth AS222 92 RF Switch Skyworks Measurement Results Measurement Setup Measurements are provided to demonstra
150. riety of wireless Personal Area Network PAN applications New extended range products and small footprints combined with network firmware flexibility make Panasonic an industry leader in the development of cutting edge RF module technology N Panasonic Electronic Components awareness and as appliance manufacturers continue their trials and testing more shall be added to store floors With the advantages of intelligent energy management so high especially with the promise of increased automation capabilities it shouldn t be long before the details of how to connect appliances are clear EMI Board Level Shields Laird Technologies Laird Technologies EMI board level shields provide the shielding necessary for differing circuits to operate amongst each other all in a basic metal shell that mounts over single or multiple components The devices offer the necessary Shielding while adding only a minimal Laird amount of height and weight to a circuit board _TECHNOLOGIES _ gt Innovative Technology for a Connected World gt PTM Onrktine On D www digikey ca ptm Features Reduced Design Cycle Get your wireless products to market faster by greatly reducing the design to production path RF hardware design development debugging and test board layout quality testing and certifications are all removed by choosing a Panasonic RF module Extended Product Life Cycle RF modules provide a consta
151. ry Good Moderate Not so Good Moderate Roaming Very Good Large scale network Low latency Not so Good Moderate Very Good Very Good Not so Good Good Very Good Moderate Not so Good Very Good Pairing speed Moderate Very Good Power consumption Cost Good Good Not so Good Very Good Very Good Not so Good Good Very Good Bluetooth low energy technology formerly known as Wibree was originally developed for the high volume consumer market Back in June 2007 Nokia and the Bluetooth SIG announced that Wibree would be integrated with Bluetooth In June 2010 Bluetooth Core Specification v4 0 with the hallmark feature of low energy technology was published Bluetooth technology now encompasses low energy Bluetooth v4 0 Classic Bluetooth and high speed Bluetooth 3 0 HS Is Bluetooth low energy technology a new technology The answer to that question is that the technology is new in some aspects but not in others For instance Bluetooth low energy technology is new in having an efficient discovery and connection setup very short packets asymmetrical design for small peripheral devices and a client server architecture But there are also other aspects that are already well established through Classic Bluetooth such as the Bluetooth radio HCI logic and physical transport layers and L2CAP packets Thanks to Bluetooth low energy technology the way we have come to experience wireless is changing Bluetoot
152. s from hundreds of slaves in only four seconds Range Thanks to a modified modulation Bluetooth low energy has an approximately 3 dB better link budget compared to Classic Bluetooth A Bluetooth low energy unit can thereby offer a range of 200 300 meters in line of site without the need of an additional power amplifier Although industrial sensors and actuators often only need a range of only 20 50 meters it is important in the aspects of robustness and reliability to have a large reserve in order to bridge temporary obstacles and interference Application examples Based on Bluetooth low energy properties the technology is very well suited for applications where transferring signal status is important The examples below show how the I Os in industrial automation can be used Figures 6 8 Response p Request i Generic 10 client seneric l0 Server Figure 6 A portable operator control and monitoring unit for example an iPhone can read and write states of the I O server Indication Inputs i Indication Outputs Figure 7 Both units function as generic 1 0 clients and are used as generic servers and indications to reflect the digital and analog states on the other side Browse through the attribute database Conf of triggers Read Requests Write Requests Fieldbus 10 Proxy Configuration tool Indications Read Responses Write Responses Figure 8 The 1 0 unit is a gen
153. s of transmitting the packets over the air The choice of RF transceiver together with the wireless protocol determines the environment in which the smart appliance can operate If a low power application requires wireless communication through obstructions such as walls then a Sub GHz transceiver may be more suitable By contrast higher frequency bands such as 2 4 GHz make for a better choice in applications requiring higher data throughput Traditionally RF transceiver design is a very complex undertaking To help alleviate this complexity manufacturers have designed fully integrated and FCC ETSI certified RF modules such as Microchip s MRF24WBOMA embedded Wi Fi module These modules include the RF transceiver the functional antenna and the supporting RF circuitry Appliance manufacturers may simply include these modules in their designs rather than acquiring the RF expertise to design the transceiver from the bottom up Using modules reduces the time to market risk and development costs There is a strong interdependency between all three components of the platform OEMs such as Microchip have recognized this interdependency and have developed complete platforms that are suitable for smart appliance development For example Microchip s wireless development environment includes support for any combination of its 8 16 or 32 bit microcontrollers with sufficient MIPS and memory RF transceivers both in the 2 4 GHz and Sub GHz spe
154. s per day Table 2 shows each of these events and their corresponding values Number of Average Events Current Table 2 Energy consumed by contact sensor components Steady state Battery self discharge Data poll 1944 uC 53 day 1 19 pA Using the values in the Table 2 I total average current I radio sleep current I battery self discharge I data poll I radio transmission 0 65 uA 3 42 uA 1 19 uA 2 25 uA 7 51 uA To calculate the battery life apply this formula Battery Life H _ Battery Capacity mAh Total Average Current pA _ 600 mAh 7514A 79 893 hours 9 12 years Thus Ember and iControl achieved the initial goal of obtaining more than three years of battery life for the contact sensor based on technology currently available to roll out to consumers Conclusion Ember and iControl have partnered to develop sensors to enhance SMA Platform capabilities and to meet the requirements of broadband service providers The results of this collaboration as demonstrated in this white paper provide sensor battery life spans well suited to the practical maintenance considerations in a typical home security environment Extended battery life is achieved by optimizing all parameters associated with current and energy consumption Ember s product roadmap contains a variety of software optimizations aimed at improving battery life for all battery powered ZigBee devices Moving forward Ember and iCo
155. s the flow and temperature of the heating fluid tx TechZOne and incorporates a display and communications block Heat is billed by the power delivered to the location measured by the heating fluid flow and the input and exit fluid temperatures over a given time period This information appears on a display either integrated into the meter or remotely located and is transmitted over a wireless link to a collector where it is aggregated and communicated to the service provider Metering functions and requirements Each type of meter must provide one or more of the following functions e Quantitative measurement The primary metering function is to accurately measure a quantity of energy or fluids Measurement systems span a range of topologies and components including temperature sensors flow sensors shunt resistors isolation transformers current transformers and time keeping systems Control and calibration These systems are used to compensate for small variations in the measurement system and to handle functions such as tamper resistance and interruption of service Communications Wired or wireless connections can be used to configure the meter s parameters and transfer stored data to a host as well as to update metering firmware or other operational characteristics Power management Low power and system robustness are essential in the event of power loss In battery powered metering systems power management is critical to min
156. same module manufacturer across the whole of a product platform the module manufacturer will not necessarily use the same chipset supplier across all modules In any case ensuring long term consistency across all IP stack implementations is not a priority for the wireless chipset manufacturers which are driven by the demands of the world s top handset manufacturers not by the collective demands of tens of thousands of small to medium sized embedded OEMs www digikey ca wireless 29 Some module manufacturers have developed proprietary TCP IP stacks to replace those supplied by their chipset suppliers and in the long term this might enable them to align the different stacks that support different communications standards such as 2G and 3G under a single API But it is still the case that for the typical embedded OEM rewriting application code to interface to new IP protocol stacks is both difficult and fails to add extra value to the end product It is difficult because of the nature of the typical embedded business Development at these embedded SMBs is carried out by small design teams with expertise in the hardware and software aspects of their core application design functions such as sensor interfacing signal conditioning and processing microcontroller or microprocessor programming application development and user interface design Communications system design and configuration is a peripheral element of the design and ma
157. ss by providing a common and readily available API upon which to base smart energy designs It also eliminates the need for utility or appliance companies to develop their own proprietary management platform The ability to track data raises many concerns energy data can be used to determine what people do in their houses privacy as well as whether or not they are currently home security One of the more sticky issues yet to be resolved is who owns energy consumption data once it has been collected Within the home the meter or energy monitor can use standard security protocols and certificates to protect home network communications Similar mechanisms will need to be in place between the gateway and back end management platform To support security appliances will also need a simple and intuitive way to pair to the energy gateway Pairing can be done through the use of a PIN provided by the gateway which is typed in on the appliance Smart Grid technology is still in its early stages Fortunately the base technologies required to implement intelligent energy management are themselves mature and already proven in the market The challenge for manufacturers lies in determining which technologies to integrate and when to release them Already products are coming to market that support energy Bluetooth Modules Exceed Expectations Panasonic Electronic Components provides powerful highly flexible cost effective RF modules for a wide va
158. stering its complexities is difficult to do when it is not the main focus of the team s work The TCP IP protocol stack implementations designed primarily for mobile handset OEMs are then ill suited to the needs of many embedded SMBs These SMBs would be better served by a stack implementation that allows re use of application code across all product variants and that makes the writing of this application code simple in the first place An architecture developed by embedded modem manufacturer Multi Tech Systems is aimed at delivering this to low and medium volume manufacturers Multi Tech s Universal IP is a single implementation of the IP protocol stack that is applied uniformly across multiple modems which implement every major communications technology from HSPA GPRS and CDMA to Wi Fi and Ethernet Universal IP implements protocols including DNS resolve FTP client Ping POP3 client PPP dial out SMTP client TCP RAW client and server UDP RAW client and server PAP and CHAP authentication as well as various additional communications functions aimed at M2M applications Figure 1 oe a Device Manhar Beep Alize Meem Emulation Bemote Wake up D M M A N D 5 Figure 1 Multi Tech s protocol stack implementation also supports additional functions aimed at M2M applications Each Universal IP modem also adopts the Universal Socket pinout see Figure 2 which means that embedded developers can swap one modem f
159. sts by allowing each device to become an intelligent transceiver sending and receiving command information wirelessly Putting all these individual intelligent devices into a home makes the entire system more reliable efficient and scaleable It also allows the products to be used in retrofit and new home construction with equal results Do you have a question about wireless solutions Digi Key has more than 130 technical support specialists product managers and applications engineers who are eager to answer your questions and assist you with your wireless projects send your questions to techzone digikey com wa TECHZOnNe Achieving RF Performance and Approvals Antenna design may seem to be as much art as science but by following a few simple design rules you can reliably hit your performance and approval targets Before selecting the antenna or antenna design and defining the mechanical specifications for a wireless product the product designer must clearly understand the RF performance targets the product must reach in order to e Achieve good RF performance in the field to ensure market success e Pass all regulatory and operator approvals Performance The Basic concepts TRP TIS and RSE For cellular applications such as GSM or CDMA basic RF performance is measured in terms of the product being able to transmit and receive reliably on a network The scientific way to measure performance is in an anechoic
160. sure to reduce bill of materials cost and design risk on each individual project they work on In the case of wireless internet enabled systems this can drive design teams to adopt an architecture that uses a cellular radio module consisting of a cellular chipset plus power circuitry and associated peripherals and interfaces and to implement the protocol stack supplied by the chipset or module manufacturer Large chipset manufacturers include Qualcomm ST Ericsson Wireless and MediaTek Module manufacturers include Cinterion and Sierra Wireless When examined at the level of an individual project this design approach might appear to make sense but this conflicts with the common business model of small to medium sized businesses SMBs in the embedded world In reality most embedded OEMs succeed by creating platform products on which they build extensions product variants or modified versions of a base product in three dimensions e Over time during the typically long product lifecycles of embedded devices updated variants are periodically developed to adapt to changes in the technical regulatory or user environment e Over market segments successful pioneer products in one market may be modified to suit the needs of adjacent markets A fleet tracking device for instance might evolve a variant for container tracking e Over geographies a European product could be adapted for the U S market by replacing a G
161. t ANT_SEL at the time when interrupt IRQ_2 RX_START is issued 2 Immediately after the successful frame reception indicated by an interrupt IRQ_3 TRX_END the AD algorithm starts searching again 3 This continues as long as the radio transceiver is in RX_ON or RX_AACK_ON state Leaving one of the receive states stops the AD algorithm The register bit ANT_SEL maintains its previous value from the last received frame until a new frame has been detected indicated by IRQ_2 RX_START see 4 That is at the earliest trp ANT SEL trR27 2 tsym for trr27 96 US tsym 16 us If the AT86RF231 is not in a receive state or a transmit state it is recommended to disable register bit ANT_EXT_SW_EN to reduce the power consumption or avoid leakage current of an external RF switch especially during SLEEP state If register bit ANT_EXT_SW_EN 0 output pins DIG1 DIG2 are pulled down Transmit diversity procedure With the AT86RF231 Antenna Diversity feature upon reception of a frame the selected antenna is indicated by register bit ANT_ SEL This register bit maintains its value until a following frame has been detected refer to the previous section In contrast to that the antenna defined by register bits ANT_CTRL register OxOD ANT_DIV is used for transmission If for example the same antenna should be used for transmission as being selected by the AT86RF231 for reception the antenna must be set using register bits ANT_C
162. t improved components can help the designer and so this is the boundary to push at Lessons learned Low cost tracking devices are growing in popularity and will find an ever increasing role in protecting people and property It is not easy to design the radios in these devices but what we have learned so far is e Both GPS and GSM radios and antennas must be designed in from the start of the tracker development to ensure they are located in the best possible positions for efficient radiation and minimum coupling between them e Greater integration is needed between radios and antennas to create compact modules that are easy to build into prototypes e Because of the small size of trackers it is necessary to have a good understanding of those laws of physics applying to small antennas and how they relate to tracker applications e tis important to keep abreast of the latest technology and devices available as well as pressing for ever smaller and more integrated components Antenova s GPS RADIONOVA RF antenna module contains both the antenna and all the RF and signal processing circuits and requires only the addition of some processor power on the motherboard and appropriate application software The module provides a complete RF subsystem for the addition of GPS and location functionality to a portable tracking device and has been demonstrated to be the most versatile and capable solution in terms of both RF and satellite acquis
163. te problems with shrinking the GPS and cellular radio components to the limited space available preventing them from interfering with each other and getting the antennas to transmit or receive signals efficiently GPS signals are circularly polarized and in the past ceramic patch antennas have mainly been used to receive them Patch antennas work well in devices with a fixed horizontal orientation because they have a relatively narrow beam looking upwards at the sky They are efficient if they are large enough and are mounted on a suitably large ground plane However in a mobile device such as a tracker the orientation may vary so patch antennas are much less suitable There is a need for an antenna with a more omni directional pattern so the orientation of the tracker is less important Unfortunately the more omni directional an antenna pattern is the lower the antenna gain and as a result the satellite signals are received with a slightly weaker signal strength resulting in lower location accuracy This however is a necessary requirement and is somewhat compensated by the fact that the tracker can receive signals from a greater number of satellites this in turn can help to recover the location accuracy Antenova has been working on a number of antennas and radio antenna modules that are specially adapted for very small tracking devices and other mobile GPS units Figure 2 Figure 2 Top and bottom view of a GPS wrist watc
164. te the performance improvement of a network node operating in a typical multipath indoor environment when using Antenna Diversity compared to a predefined antenna configuration AD Receiver TR e LEG meni E Meigi plate oneee deni ree OF sagt EE _ _ _ __ ____ _ _ _ _ _ ______________SS_ Tranter Figure 8 Antenna Diversity Measurement Setup www digikey ca wireless 23 Node 1 RX equipped with two antennas see Figure 9 is stepwise moved along a fixed track Node 1 stops at each measurement point It receives a frame and evaluates its energy detection ED level Node 2 TX is situated in a fixed position permanently transmitting frames The transmitter is equipped with only one 2 4 GHz 2 4 whip antenna and therefore does not use transmit Antenna Diversity The measurement setup has no direct line of sight between the two nodes Therefore the propagation scenario is determined by multipath Additionally the scenario of the indoor environment must be kept static during the measurement process To investigate the multipath propagation characteristics see Figure 9 the transmit power is set such that the average receiving power is between 60 to 65 dBm During the PER measurements the transmit power of node 2 is adjusted see Figure 10 to reduce the average received signal power to a value slightly above the sensitivity limit of 101 dBm This is necessary to illustrate the effect o
165. ters As more embedded intelligence is integrated into smart meters we ll see an explosion of innovative applications and additional opportunities to harness the advanced capabilities these intelligent systems will bring to energy and resource consumers everywhere Did You Know There are no standard protocols for meter to meter and meter to infrastructure communications Currently the available communication media includes power line communication e GPRS e 400 Mhz metro area networks e 3G e WiFi More likely however a multi media network will have a mesh of these technologies in it www digikey ca wireless 33 Designing Intelligent Appliances for the Smart Grid The Smart Grid promises to be a game changer but the rules of the new game are still being written The burgeoning Smart Grid infrastructure promises to reduce costs and enable a wide range of innovative consumer industrial and embedded devices The Smart Grid promises to be a game changer across the entire electronics industry including consumer industrial and embedded devices of all types Innovation is driven by value either because a new product reduces the cost of an existing technology or because it offers new features and capabilities that users are willing to pay for While it isn t always predictable whether consumers will be willing to pay a premium for new features the prospect of reduced operating cost is always attractive C
166. tes have a certain characteristic signal value presentation format etc which is described in the client configuration In the Generic Attribute Profile GATT service groups attributes declarations and descriptions are included In the Generic Access Profile connection discoverability connectable and bonding are described In this way a number of basic services and profiles are set up such as for instance timing battery condition automation 1 0 building automation temperatures thermostat humidity lighting On Off Switch Dimmer remote control fitness Step Counter Heart Beat Monitor medical devices glucose meters cars etc General Alfribute Profile Attribute Protoco E rti T mr MSGUFGY MANSEE Figure 5 Overview of the Bluetooth low energy software structure Performance Connection and latency Bluetooth low energy technology only uses three channels to build connections and to discover other devices this not only allows for lower power consumption but also for a faster connection in only a few ms With Bluetooth low energy technology the latency periods are dependent on how often the master sends messages to the slaves and how often it receives data from the slaves The latency period for one slave only is 7 5 ms and then increases slowly for each additional slave For example with a connection interval of four seconds a master can address one slave every five ms and thereby achieve update
167. th the FCC These are called Class Permissive Changes Note if a Class Permissive Change causes your product to look different from the one that was certified it is strongly suggested that photos of the modified transmitter be filed with the FCC Minor changes that increase the radio frequency emissions from the transmitter require the grantee to file complete information about the change along with results of tests showing that the equipment continues to comply with FCC technical standards In this case the modified equipment may not be marketed under the existing grant of certification prior to acknowledgement by the Commission that the change is acceptable These are called Class II Permissive Changes Major changes require that a new grant be obtained by submitting a new application with complete test results Some examples of major changes include changes to the basic frequency determining and stabilizing circuitry changes to the frequency multiplication stages or basic modulator circuit and major changes to the size shape or shielding properties of the case No changes are permitted to certified equipment by anyone other than the grantee or the grantee s designated agent except that changes to the FCC ID without any other changes to the equipment may be performed by anyone 06 The receiver is covered by a Declaration of Conformity DoC which states that the product was tested by the Grantee and found to comply with
168. that may be transmitted between devices Security for both Wi Fi and ZigBee is based on a robust AES 128 algorithm and operates within the framework that is described in the IEEE 802 11 and IEEE 802 15 4 specifications respectively The methodology for establishing and transporting security keys and the authentication of devices are all defined by each of the specifications Smart appliance manufacturers who choose a proprietary wireless protocol have the added challenge of selecting the appropriate security algorithm and services Independent of the encryption algorithm chosen there are two important security related factors that each manufacturer must be aware of The first is whether the encryption algorithm is subject to export control laws Products containing software or hardware algorithms must either restrict their key lengths or obtain specific export authorizations Regardless of whether they are based in hardware or software encryption algorithms have the same restrictions and must adhere to all export control laws Secondly regardless of the robustness of the encryption algorithm data integrity will be severely compromised if the keys are compromised Therefore protection of the keys themselves is of vital importance Device manufacturers should devise an appropriate method of key protection The smart appliance platform Wireless smart appliances are generally built upon a platform that includes three major subsystems th
169. the applicable technical standards The test data should be kept on file by the responsible party as defined in CFR 47 2 209 but nothing is actually filed with the FCC This means that you will just need to have data on your product on file that shows that the modified product still complies with the regulations Nothing needs to be filed with the FCC for changes in products covered by a DoC Where can look up information on equipment if know the FCC ID number The FCC maintains a database that can be searched on the Internet The database contains information on all equipment that was granted through the Equipment Authorization process What happens if one sells or uses non compliant low power transmitters Bad idea The FCC rules are designed to control the marketing of low power transmitters and to a lesser extent their use The act of selling or leasing offering to sell or lease or importing a low power transmitter that has not gone through the appropriate FCC equipment authorization procedure is a violation of the Commission s rules and federal law Violators may be subject to an enforcement action by the Commission s Field Operations Bureau that could result in e Forfeiture of all non compliant equipment e A 100 000 200 000 criminal penalty for an individual or organization e Acriminal fine totaling twice the gross gain obtained from sales of the non compliant equipment e An administrative fine totaling 10 000 d
170. the battery without any connection between the electrodes Self discharge decreases the shelf life of batteries and causes them to have less charge than expected when actually put to use To model self discharge the team added a continuous self discharge current of 3 24 pA Batteries are derated to account for internal resistance that becomes significant during radio operations For example the lithium batteries that iControl uses in its sensors are derated from 800 mAh to 600 mAh to account for internal resistance of the battery Battery operation primer One way to look at energy consumption is to think of the battery as a tank of water the volume of water representing the total capacity of energy available for use Water is emptied through a pipe and faucet attached to the tank flowing at a certain rate which is similar to the current flow of a circuit drawing on the energy of a battery Anything that can be done to reduce or interrupt this flow will extend the time that water remains in the tank or energy remains in the battery Battery life calculations The life of a security sensor battery is calculated by dividing the battery capacity expressed in mAh by the total average current expressed in pA This formula is shown below Battery Life H artery capacity mAh attery Life IH zorgi Average Current uA The total average current is the key factor it is a sum of all the events both steady state and periodic and th
171. the general public CONFIDENTIAL Items that cannot be given confidentiality are 1 photos of a device anyone who purchases a device will know what it looks like 2 test results the public has a right to review a test report showing 52 compliance with the FCC regulations and 3 the user s manual In general the only information that is granted confidentiality is patented trade secret information that if given out could harm a company financially Step four The filing process The FCC greatly streamlined the approval process Certifications were once issued by the FCC directly but independent testing laboratories are now allowed to issue certification though the Telecommunication Certification Body TCB program They can also issue certifications for other countries with which the US has a Mutual Recognition Agreement MRA TCB s must be accredited and comply with Section 2 962 The filing process is usually done by the test lab as a part of their service The lab will compile the test report photographs and other items listed above The TCB will review all application materials and if the device conforms to the requirements they will upload this information to the FCC After the FCC receives the report they will add the product and the ID number to their database and their website and issue a Grant of Certification At this point the device can be legally marketed and sold After certification the FCC or the TCB
172. the master controller the slave controller also consists of three boards a TDA5051A board an LPC1114 board and an LED driver power supply board that controls a remote LED lighting array The slave controller is an addressable lighting controller capable of receiving commands over the powerline from the master control unit The slave controller s command set includes functions such as on off brightness level color mixing and luminary status A high brightness HB LED is used to indicate a slave fault It blinks once a second to indicate normal operation If the controller fails it will not blink An NXP PCA9632 is used for RGB color mixing applications The 4 bit PWMO to PMW3 outputs of the PCA9632 control the four HB LEDs and the 0 to 10 V Boost MOSFET These outputs are compatible with applications relating to methods used by the lighting industry The demonstration kit uses a modular design that makes it easy to support other applications besides lighting Simply replace the application block with circuitry for the target application the TDA5051A and LPC1114 configurations remain the same Other benefits of the kit include software support zero cross detection and redundancy support Summary To meet the growing demand for cost effective in home control networks NXP offers the TDA5051A a highly integrated ASK modem that uses the existing mains network as the communication channel Offering easy power isolation and supported by
173. the same board layout oages 29 31 11 For active tags the requirement for battery life is years minimum from a simple coin battery such as a CR2032 pages 48 49 1 2 a DOWN The use of the AT86RF231 Antenna Diversity transmission ____ A Bluetooth low energy unit can thereby offer a range of 200 300 OOD A N network as the communication channel pages 44 46 Ember s product roadmap contains a variety of software optimizations aimed at improving battery life for all battery powered ___ load power is the deciding factor in deciding if energy harvesting techniques can be used remote wireless sensor networks pages 61 63 13 Another key requirement for smart meters is the use of high performance yet low power pages 32 33 devices pages 26 28 _ considerably improves the reliability of real world network implementations 0ages 20 24 The PowerMeter and load control services are two such examples with many more such services becoming available every day pages 41 43 __ inline of site without the need of an additional power amplifier pages 57 60 Devices are available that convert AMR device data to industry standard protocols like the ZigBee am sure you are asking yourself how come used mobile phones that___ _ violate these guidelines pages 7 9 0 To meet the growing demand for cost effective in home control networks NXP offers the TDA5051A a highly integrated ASK modem that uses the ex
174. the technology available For example if better components were available could the tracker design and performance be improved Let s look at this A typical complete GSM module that might be used in a tracker measures roughly 30 x 30 x 5 mm and the battery is often a similar size These two components take up the majority of space available as the processor and GPS systems are generally smaller Suppose that the whole of the GSM radio could be shrunk to a single chip or a much smaller module Suddenly a lot of space is freed up in the tracker but how best to use it It would not help to make the box smaller as we have seen But perhaps the box could be made longer and thinner especially if a suitable battery could be chosen The tracker now becomes a thick strip that might be hidden in the frame of a valuable painting or concealed in the lining of a luxury designer bag just to give two possible examples Pigion TechZ ne Now imagine that we introduce flexible printed circuit technology together with a curved battery Our strip tracker can be turned into the watch strap instead of being part of the watch or become part of a dog collar or a belt The long format of the device would mean the GSM radio would work well and the device would be easier to hide At present the size and rigid shape of the SIM card and holder would prevent this type of design being realized so a new SIM card format would be needed These considerations show tha
175. thin the applicant s files Following successful completion of this process the end product should be labelled as prescribed by the FCC Transmitter procedure The transmitter is an intentional radiator and subject to certification In most instances users of modules manufactured by Linx will seek certification under part 15 247 for Spread Spectrum modules or under 15 249 for narrowband modules An exception to this is RF modules which have been pre certified by Linx under the modular approval process In instances where certification is required testing will need to be performed by a properly approved laboratory In most cases it is not necessary to be present for testing and the laboratory will prepare the filing paperwork Certifications were once issued by the FCC directly but now independent laboratories are allowed to issue certification though the Telecommunication Certification Body TCB program which has greatly streamlined the process Following successful testing a report will be produced showing information about the testing and the device A label displaying the applicant s FCC ID number along with FCC prescribed information will need to be placed on the certified product Now that a basic overview of legal issues has been covered it is time to consider the technical issues of operation in these frequencies Benefits of operation within the 902 928 MHz band The first benefit of the 902 928 MHz band is freedom from the
176. tion and grid performance by facilitating two way communication and generation capabilities throughout the distribution system It is becoming increasingly clear that the Smart Grid is not defined by NEW devices but by the services enabled by adding secure and reliable two way communications to as many points on the distribution grid as possible Clearly this will require some new equipment but it will also require innovation that minimizes stranded assets for the utility industry Digi International has identified four capabilities Figure 1 that are required to drive the benefit goals of the Smart Grid e Create devices and sensors to capture information and provide control services e Collect communication devices and networks that allow data and control services to happen e Manage a network operating environment for managing all the connected devices e Utilize business applications that turn the data into actionable information and driving benefits A Complete Solution Collect intelligent RF connected Gateways Networks Operations Apphcations Figure 1 Capabilities required for a successful Smart Grid In reviewing these capabilities several interesting observations can be made The first is that these do not define a specific network technology device or sensor They are a capability that must be enabled for all devices new and old that are part of the energy
177. tor as whip antennas but will have a counterpoise as well as the element inside the sleeve Typically the counterpoise will be a metal tube with the antenna element positioned on top A coax cable is attached to the connector and then runs up inside the tube to connect to the tube and element making a center fed dipole antenna In Figure 13 the antenna element is a helical to reduce the overall housing length Figure 12 A 916 MHz antenna radiation pattern in the plane of a 4 x 4 ground plane Figure 13 A whip style center fed dipole antenna www digikey ca wireless 15 A common misconception about antennas with an internal counterpoise is that their characteristics are unaffected by external factors While it is true that an external ground plane is not required for the antenna to operate correctly if you connect one of these antennas to a product that has a ground plane you will see the same shifts as shown in Figure 10 The product s external plane will add to the antenna s internal counterpoise and shift the frequency gain and radiation pattern The performance shift can be minimal but it should be recognized that while a dipole does not require a ground plane it is not immune to external factors Part of the attractiveness of a dipole is that an external ground plane is not required for the antenna to perform well The downside is that dipole antennas are usually larger and more expensive since they have to include the
178. trated into a small area Even though the overall light output has remained constant the concentrated source will produce an increase in lux at the focus point compared to the wide source In the same way an antenna that focuses RF energy into a narrow beam can be said to have higher directivity at the point of focus than an antenna that radiates equally in all directions In other words the higher an antenna s directivity and the narrower the antenna s pattern the better its point performance will be Ku Figure 9 Light Gain www digikey ca wireless 13 Monopole antenna performance The performance of a monopole antenna is critically dependent upon the counterpoise used as the other half of the antenna This counterpoise can be a solid copper fill on a circuit board or a metal enclosure Since the RF stage is referenced to the circuit ground this plane or the enclosure are also connected to ground The size of the ground plane counterpoise as well as its location with reference to the antenna will have a significant impact upon its VSWR and gain Typically antennas are designed on a counterpoise that is one wavelength in radius At one wavelength the counterpoise will act sufficiently like an infinite plane This makes for great specifications but in the real world a cordless phone will not have a one foot radius ground plane for its antenna This begs the question what happens when the ground plane is reduced to so
179. uency of interest These frequencies correspond to a wavelength That wavelength is the required antenna length That length is what must be incorporated into the final product either embedded inside the enclosure or externally attached to the device The frequency of the electromagnetic waves is related to the wavelength by the following equation PE E where f frequency in Hertz Hz wavelength in meters m c speed of light 299 792 458 m s As can be seen by the equation the higher the frequency the shorter the wavelength and the smaller the antenna For example the wavelength for 433 92 MHz is 0 69 m 2 27 ft and the wavelength for 916 MHz is 0 33 m 1 07 ft 433 92 MHz is a popular frequency for Remote Keyless Entry RKE systems such as car key fobs but obviously there is no way that a 2 27 foot antenna is going to fit into a key fob Fortunately for everyone who wants to carry their keys in their pocket there are ways to make the antenna smaller Since resonance will occur at whole number fractions 1 2 1 3 1 4 etc of the fundamental frequency shorter antennas can be used to send and recover the signal As with everything in engineering there is a trade off Reducing the antenna s size will have some impact on the efficiency and impedance of the antenna which can affect the final performance of the system A half wave dipole antenna has a length that is one half of the fundamental wavelength It is
180. uetooth low energy chipsets are available in two versions connected to a master in a production island In most cases an Infrastructure Ethernet network is available and there is no need for Robustness security and reliability mesh networks to extend the geographical coverage Bluetooth low energy technology like Classic Bluetooth features adaptive frequency hopping in order to secure a robust transmission even in harsh industrial environments To obtain simpler and cheaper radio chipsets Bluetooth low energy technology uses only 40 channels 2 MHz wide while Classic Bluetooth uses 79 channels 1 MHz wide Figure 2 A unit is always either a master or a slave but never both The master communicates with the slaves and it can also communicate simultaneously with multiple slaves Further the master controls the timing pattern for the links and the slaves only passes on requests made by the master A new feature introduced with Bluetooth low energy technology is the advertising function A unit announces itself by periodically advertising itself An advertisement can also _ for example include a process value or an event that has occurred Figure 4 navonIser u ens Se m E a G H M M a a a M M CO m e e e ee a U e o e e e Hiini 1E MH id MH mi BA Wi RAI UMI l MH 4 MH i hiii i MAII Pat MI HMH 4 Mii n hii Hh PALI UMH I MH 4 MH m hiii HALL UMN w Mil A MI MH ji MH it hii Ra
181. ugh wireless connectivity In today s marketplace green applications for smart appliances have begun to emerge that are centered around energy usage and monitoring Services such as Google PowerMeter see www microchip com Google have enabled consumers to gain instant access to their energy usage data In turn having this information has provided consumers with the impetus to undertake measures such as signing up for cost saving energy usage plans that are offered by their utility companies Utility companies are rapidly deploying wireless enabled smart meters that connect to Home Area Networks HANSs which allow them to provide load control features to the smart appliances The benefits are that the utility companies can better regulate their energy demands collect valuable real time usage data and offer more suitable tiers of services to their customers Using all this information utility companies can more precisely predict and plan their future infrastructure expansion Manufacturers are able to bring wirelessly enabled smart appliances quickly to the marketplace by integrating two key building blocks into their products wireless technology and advanced microcontrollers Figure 1 A smart home Additionally large groups of technology companies have recently joined forces to form consortiums that have defined the framework of how these smart wireless appliances communicate with each other The net effect of these developm
182. ult of design specific factors such as those discussed here as well as differing references methods of test and presentation formats among antenna suppliers With this in mind allowance must be made for testing and optimizing the antenna as an integral part of the overall design process While it is unlikely an end user will spend much time contemplating the nuances of antenna implementation they will certainly appreciate the range and reliability of a well designed product The field of antenna design and application is complex but by understanding a few ground rules it is not necessary to be an antenna designer to design with an antenna Did You Know An antenna s HPBW half power beamwidth is defined as the angle of separation between the two half power points on either side of the main lobe of its radiation pattern The specification can often give the user an idea of how directive the antenna is with a smaller beamwidth inferring a more directive antenna This is most useful with antennas that have a primary direction of propagation such as Yagi Uda or horn types wa TECHZONE Antenna Design for Portable Tracking Devices The designer of portable tracking devices is trapped in a space with three types of boundaries physics cost and available technology All are challenging but none are insurmountable Devices that you can interrogate by cellular radio to find out where the host platforms are located ha
183. um on each message A slave that receives a proper framing byte the correct number of bytes in the message and no parity or checksum errors will transmit a successful acknowledge message and act on the command embedded in the message If the acknowledge message is not received within a preset time the master re transmits the message up to ten times until a successful acknowledge message is sent The dedicated ASK protocol includes redundancy and improves the robustness of the TDA5051A even in environments that are comparatively noisy Figure 3 The TDA5051A in a home control network Sample application home control network Figure 3 shows the TDA5051A in a home control network The network includes a single control unit and several appliance units The control unit sits on a 220 V powerline and is connected to appliance units located throughout the house Each appliance unit is associated with an electrical appliance a lamp a fan or a refrigerator just about anything with an on off switch can be put on the network The control unit includes a microcontroller such as the LPC1114 and supports an interactive interface that the homeowner uses to configure and control the network Each appliance unit is equipped with a low cost microcontroller to process data received from and transmitted to the powerline The microcontroller in the control unit writes data to the TDA5051A The TDA5051A encodes the data and sends it over the pow
184. utions required but in developing efficient secure and scalable connectivity over a broad range of networks This middleware management platform will be a critical piece of the Smart Grid and must not only provide support for the new technologies but also manage devices and technologies that are already deployed Most importantly many M2M management platforms isolate the utilities applications from the specific communication network allowing new technologies to be deployed without disrupting existing systems Conclusion device management is key to being future proof The combined forces of all networking technology utilized in the Smart Grid are aimed at time sensitive collection of energy consumption data Whether utilizing power line carrier fiber cellular or proprietary wireless communications the goal is to determine what energy is being used and more importantly when If commute to the office during rush hour use far more WiFi Authentication Rabbit Semiconductor Rabbit Ssemiconductor s guide to WiFi authentication is a self paced tool to introduce design S engineers to update program firmware via a secure wireless connection The product training module allows deign engineers to learn about new features of Dynamic C v10 54 release recognize security terminology protocols and standards for WiFi authentication and to understand remote program update firmware and tools and sample
185. ve been around for some time in the form of vehicle trackers and covert devices Now consumer devices are becoming available that can be used for tracking children workers old people pets luggage and other personal property The list is seemingly endless Some trackers are equipped to provide an alert if the device is tampered with if the host device is removed or even if it goes out of a programmed area geo fencing Trackers can also be equipped with a panic or call button if the device is being worn by a lone worker Figure 1 shows a credit card size tracking device suitable for lone worker and executive security applications Mi0264 Planar Mount RF Antenna Modube Figure 1 Credit card size tracker device with GPS RF Antenna module visible highlighted at the bottom of the picture NB The GSM antenna cannot be seen in this view Device size 80 mm x 50 mm x 6 9 mm Lx Wx H In principle a tracker is a simple device having a GPS receiver so that it Knows where it is and a cellular radio terminal so that it can transmit this information when commanded to do so However in practice there are some challenging problems involved in designing the necessary radio system In this article we look at these problems and see how they can be overcome Portable tracking devices come in all shapes watches credit card format USB sticks dog collars etc but unfortunately they mainly come in one size small Small form factors crea
186. ve transmit Rx Tx data interface to the powerline are provided by a specialized converter transformer A series power inductor and a high voltage coupling capacitor afford powerline filtering The powerline isolation circuitry and the AC to DC power supply circuit provide the 5 V DC supply for the TDA5051A Figure 2 The TDA5051A with powerline isolation In the configuration shown the reference clock is generated by a low cost fundamental crystal oscillator The reference clock can also be provided by an external clock source such as from the microcontroller clock or the clock output CLK_OUT of the TDA5051A can be used as the clock for the microcontroller The CLK_OUT DATA_IN DATA_OUT and PD power down pins provide easy interface with the microcontroller ASK redundancy software protocol ASK transmission is relatively inexpensive easy to implement simple to modulate demodulate and requires little bandwidth compared to other formats such as Frequency Shift Keying FSK One drawback of ASK however is that it can be difficult to use in noisy environments www digikey ca wireless 45 To help address this NXP has developed a special ASK protocol for use with the Cortex MO microcontroller LPC1114 The software provides robust control via powerline communication for home automation of lighting appliances and security systems The protocol used for the ASK modem calculates and checks the parity on each byte and the checks
187. wise it shall be set back to the reset value Table 1 Receiver Sensitivity Control PDT_THRES Reset value to be used if AD algorithm is disabled 0x3 Recommended correlator threshold if AD algorithm is enabled Register OxOD ANT_DIV The ANT_DIV register configures and controls Antenna Diversity e Bit 7 ANT_SEL This register bit signals the currently selected antenna path The selection is based either on the last antenna diversity cycle if automated Antenna Diversity is enabled ANT_DIV_EN 1 or on the content of register bits ANT_CTRL refer to the previous section Transmit Diversity Procedure Table 2 Antenna Diversity Antenna Selection ANT_SEL o fw e Bit 6 4 Reserved e Bit3 ANT_DIV_EN 22 This register bit controls the AD algorithm On reception of a frame the algorithm selects an antenna autonomously during SHR search This selection is kept until e A new SHR search starts e The receive state is left e Disabling AD algorithm Selected antenna is defined by register bits ANT_CTRL e Bit 2 ANT_EXT_SW_EN Table 3 Antenna Diversity Algorithm Control vame oest oooO E Automated AD algorithm disabled Register Bit ANT_DIV_EN Automated AD algorithm enabled Note If ANT_DIV_EN 1 register bit ANT_EXT_SW_EN shall be set to 1 too If enabled pin 9 DIG1 and pin 10 DIG2 become output pins and provide a differential control signal for an Antenna Diversity switch T
188. y DoC which should be maintained in the applicant s files Transmitter certification is also relatively painless since many labs that are TCB certified are now allowed to issue certifications on behalf of the FCC Full transmitter and receiver testing can cost around 5 000 transmitter only around 3 500 and the receiver about 1 500 The entire process can now be rapidly completed and many labs can perform other testing at the same time such as Class A B Label the product and market it Following successful completion of the approval process products should be labeled as required by Part 2 925 and 2 926 as well as Part 15 19 or otherwise prescribed by the FCC Summary Bringing a product through the approval process summarized in Figure 1 involves cost effort and in some cases frustration but in the end your product will have an exciting new dimension of functionality and market appeal By following the steps outlined in this application note and reviewing a copy of CFR 47 you will be well on your way to RF success While complying with applicable provisions may seem unnecessarily restrictive such regulations serve to ensure the availability of usable RF spectrum for every product The approval process Introduction Here in the United States the Federal Communications Commission FCC is responsible for the regulation of all RF devices The FCC requires any device that radiates RF energy to be tested for compliance with FC
189. y available and then choose a specific frequency based on technical issues such as range propagation antenna length power consumption and potential interference If you are not familiar with these technical issues consult with a Linx application engineer or read Linx Application Notes focusing on those issues Component selection Once a frequency of operation has been selected the RF section and antenna must be carefully designed and optimized to comply with the allowed power and harmonic limitations imposed by Part 15 This process is greatly simplified if you are using a Linx module but it is still important to recognize that the antenna and layout play key roles in the product s legal operation Many modular RF transmitter products including those manufactured by Linx have the potential to output RF power in excess of Part 15 limits This extra power helps designers overcome inefficient antenna styles and take advantage of the FCC s averaging allowance when modulation techniques such as ASK OOK are employed If necessary output power may be reduced using the module s level adjust or an external attenuation pad Another consideration in antenna selection is that Part 15 203 requires the antenna to be permanently attached or coupled with a unique or proprietary connector While this requirement leaves room for interpretation the FCC s intention is that a user not be able to change the radiated characteristics of the device b
190. y easily interchanging the antenna with a higher performance model Build production ready prototypes After choosing a frequency for operation and a suitable RF stage you will want to move from concept breadboard prototypes to a production ready model as rapidly as possible ma TechZOne Prescreen and optimize Once a wireless product is finished its output power and harmonics should be checked to ensure that the RF stage is both optimized and Part 15 compliant This testing requires a spectrum analyzer and calibrated antennas If you do not have access to these instruments consider prescreening services such as those offered by Linx The prescreening process can result in a cost savings over formal testing and provides an opportunity to maximize product performance Send the production ready product to an FCC authorized testing facility Once your product is in its finished form exactly as it will be produced testing should be conducted by a properly approved laboratory In most cases it is not necessary to be present for testing and the laboratory will prepare the filing paperwork The FCC has greatly streamlined the approval process by allowing independent laboratories to issue certifications though the Telecommunication Certification Body TCB program Unless specifically requested pursuant to Section 2 1076 receivers no longer require certification They just require a quick test and issuance of a Declaration of Conformit

Wireless Solutions TechZone Magazine, March 2011 - Digi-Key

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