ANTENNA TEST RANGE - Colorado State University
Contents
1. Figure 23 Flowchart of Electronics USB to RS232 communication is achieved using FIDI FI232RL USB UART interface Communication will occur as the controller is given a command and when the control reports back that the command was accomplished The LabView software requires a 28800 baud ASCII will be sent and received through a virtual serial port Microprocessing will be done by the Atmel ATMega168 ASCII commands will be converted to the appropriate signals to motor driver IC and linear actuator We continue to use the ATMegal68 to reduce writing new code for the electronics the free application WinAVR to compile the 26 microprocessor code and because the debugger is already available for use Movement devices will be enabled based on counters and comparators contained in the microprocessot Motor driving is managed with the Allegro A3970 IC device This motor driver is equipped with PWM H Bridge and micro stepping capabilities The IC is an easy way to control the movement of a bipolar stepper motor and minimizes the circuitry greatly This will increase performance and stability of the system Bipolar step motors are chosen to drive the mechanics of the planar scanner The motors provide precise control and high torque which will eliminate some measurement error Figure 24 shows the basics of a stepper motor The motor consists of a magnetized rotating plate with alternating poles and two electromagnets The current through the2. 0 1 689655E 9 1 012923E 0 0 000000 0 0 000000E 0 4 000000E 0 1 724138E 9 328 393817E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 758621E 9 657 067657E 3 O 000000E 0 O 000000E 0 4 000000E 0 1 793103E 9 1493111E 0 Figure 18 Display data screen The Run Measurement Sub VI receives the measurement data back from the VNA before moving to the next measurement location After this Sub VI is done executing the program moves to the Array to Listbox state In is in this state where the program transforms the 2 dimensional array of data compiled received from the motor driver PCB and the VNA and transforms it into a Multi Column Listbox which is easy for the user to interact with Additionally at once this state is finished executing GUI is switched to the data display screen shown above This screen allows the user to see all the data generated by the scan as well as the sweep settings previously defined On the right is as a three dimensional model showing the data for one particular frequency The model is interactive meaning the user can zoom in or out and move it around Additionally the user can select the frequency displayed on the graph by double clicking a frequency in the data table However most of the time it will be for useful for the user to export the data to another analysis program such as Matlab These can be accomplished by selecting the Export Data button on the left side beneath the data table If the user w
3. Calibration 6113E135 28B0 432B 989E Channel 1 Bandwidth 700 0 Hz Sweep Gen Type 0 Analog Sweep Points 801 30 Sweep Type 0 Linear Frequency Linear Frequency lw Center Freq 1 5 E 9 Hz 1 500000G Span Freq 1 0 E 9 Hz 1 000000G Measurement Type 0 S11 Measurement Name MY_MEAS Port Power Figure 16 Configure VNA screen Alternatively if the user presses Configure Measurement the code moves to the Motor Sweep Setup state This state among other small tasks changes the GUI to the configure motors screen On this screen the user has the ability to input all the necessary information needed to create a sweep pattern for the measurement 18 FVP MAIN E fl Elevation Po dl eve mama EH z En SEA s Home Azimuth at EOS Zero Azimuth iS E Home Azimuth 2 T VISVisa Resoure ER VISVisa Resoure P Home Elevation J Positon a gt Zero Elevation fs 3 Polarization E Take Measurement Azimuth Y Elevation Error Out Error In 2 3 be Ka Home Azimuth 2 Figure 17 Run Measurement Sub VI Each of the boxes are already populated with default values that user can either keep or change Additionally each of the boxes has programmatic limits as to what values can be entered For example if the user tries to input a value of 1 into the Steps box the program will override it and replace it with the closest acceptable value Once the user has entered
4. a stationary transmitting antenna a dynamic scanning antenna The conceptual design includes three main mechanical elements the horizontal platform the elevator and the antenna mount Each will be briefly discussed The majority of the components will be manufactured out of Delrin acetal because of its low friction coefficient ease of precision manufacturing long durability high integrity and most very low conductance The horizontal sliding platform will support the whole system A belt drive will position the platform at the desired horizontal position upon a track The belt drive will have a worst case accuracy within 2mm This will be achieved by a bipolar stepper motor and gearbox The track and platform will support a load antenna antenna mount and elevator of at least 100 kilograms The elevator will control the vertical position of the antenna Top and bottom Delrin shelves for the antenna mount will be supported by three polycarbonate guide shafts with bushings and driven by a ball screw actuator A bipolar stepper motor and gear box will drive the actuator The goal weight for the elevator is 25 30 kilograms Figure 21 Planar Scanner Sketch Up 24 The antenna mount will control the polarization of the antenna The spherical scanner is using a stepper motor to accomplish this The drawbacks of the motor occurs when the connecting the cables to adapter positioned on the center backside of the antenna and th
5. code wakes up and grabs the user input parameter and chooses the next state based on these parameters From the state diagram for example in order to exit the program it is necessary to return to the home state and then choose exit Using the state diagram the software framework was then generated reflecting an equivalent program flow The framework within the code is the state machine itself and its supporting VPs Wait for Exit Event Motor Sweep Setup gt Event lt lt QUE VNA Setup E Event Run Measurement Ron m Array To Listbox Wait for Update Graph Figure 12 State Diagram 14 Program Development and Operation Maks the the vi template that you use for top level Top event strocture to force operators snmedutely a 0 Timeout Pl project directory ii d VISA session 5 ea hy h HIH Open lead E error in no error LEs ON XOFF v u time string Figure 13 Initialize State After the state diagram and the program framework were complete the real coding was ready to take place The figure below shows the overall frame work of the application and the Initialize state As in the state diagram the first state the code operates is the Initialize state Within this state the program retrieves the file structure location needed to open the error log and initializes the TCP IP connection with the VNA and the RS232 connecti
6. control contro Figure 8 Example Test System The test antenna positioning system is usually one of three types a planar spherical or cylindrical scanner We want to use one of these systems so that when we analyzed the measurement results we can simplify the mathematics In Figure 9 you can see the three different scanning methods Every dot in the picture is roughly a point where the antenna takes a measurement Of course the positions can be even finer in detail but that is entirely a decision for you to make _a b Cylindrical scanning c Spherical scanning a Planar scanning Figure 9 Scanning Methods 10 CHAPTER 4 ANTENNA TEST SOFTWARE Initial Development To control the antenna positioning system a complex software application needed to be developed The previous year s team developed a prototype of this software using C and Visual Studio Shown below is the GUI Graphical User Interface for this prototype which allows the user to interface with the system and configure measurements However this prototype lacked the ability to configure and load calibration files from the VNA Vector Network Analyzer Additionally the software did not allow the user to configure sweep measurements along multiple axes These among other small issues lead to the software being redeveloped using National Instruments LabView 8 6 Being a test and measurement based software LabView was an ideal choice for
7. electromagnets create a powerful magnetic field which will provide torque to step the plat from N to S poles In this example current flows from 1a to 1b and from 2b to 2a Sequencing the distribution of potential to the 4 ports will make the motor rotate Figure 24 Diagram of the Stepper Motor Microstepping creates intermediate steps between each pole step on the magnetized plate Figure 25 from the Allegro A3979 spec sheet shows the difference a normal stepping cycle and microstepping with 4 intermediate steps The microstepping is achieved by varying the ratio of torque between the 27 two phases in a sinusoidal cosinusoidal method Microstepping provides a much higher resolution of stepping but there is a trade off of accuracy for each intermediate step sema TU UU UU UU step incu HOME Output HOME Output Figure 25 Two Possible Types of Outputs From Motor Driver Pulse width modulation PWM is used to accelerate the motor and then to regulate the speed of the motor The duration of the pulse high time will determine the average voltage applied to the motors which the motor torque is proportional see Figure 26 Torque determines the speed at which the motor turns or slows down The motor driver IC will automate this signal Figure 26 Graph of PWM Signal 28 CHAPTER 6 FUTURE WORK Next semester we plan on continuing with the progress that we have made this semester The following is a brief list
8. of items we plan to accomplish Programming This semester we created a LabView program that acts as the control center combining information sent to and from the microprocessor and the Vector Network Analyzer Next semester we hope to expand that program to give us control of the planar scanner We also want to reprogram the microprocessor code to decrease the size and efficiency of the code We also want to take a look into a finer motor movement that gives us the ability to move two motors at once Mechanical Design and Analysis We plan on creating a CAD design of the planar scanner that we plan on using to simulate stresses and other dynamic tests on the planar scanner Doing so will give us confidence in the design we came up with this semester Also we need to order the parts needed and get them machined Electronics We hope to create a new printed circuit board PCB next semester that will house all the motor control electronics 29 APPENDIX 1 BUDGET This semester we focused on research and software design The school provided the developmental software used The only expense was due to electronics research with breadboard and components These expenses are covered by the funding given to all senior design students 10 eia af 50 readboardcomponets wus oo s Total 2 545 565 Figure 27 Expected Budget 30 BIBLIOGRAPHY Stutzman Warren L Thie
9. 0000E 0 1 931034E 9 1 072606E 0 0 000000 0 0 000000E 0 3 000000 0 1 965517E 9 1 444351 0 O 000000E 0 O 000000E 0 3 000000 0 2 000000E 9 879 488349E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 000000E 9 581 435561E 3 0 000000 0 0 000000E 0 4 000000E 0 1 034483 9 717 208922E 3 O 000000E 0 0 000000E 0 4 000000E 0 1 068966E 9 424 916148E 3 0 000000 0 0 000000E 0 4 000000E 0 1 103448E 9 906 291842E 3 O 000000E 0 0 000000E 0 4 000000E 0 1 137931E 9 536 875963E 3 0 000000 E 0 0 000000E 0 4 000000E 0 1 172414E 9 985 054791E 3 O 000000E 0 0 000000E 0 4 000000E 0 1 206897E 9 1 223547E 0 O 000000E 0 0 000000E 0 4 000000E 0 1 241379 9 169 645950E 3 O 000000E 0 0 000000E 0 4 000000E 0 1 275862E 9 568 466425E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 310345E 9 405 567497E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 344828E 9 632 225633E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 379310E 9 854 947090E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 413793E 9 458 507240E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 443276E 9 945 346355E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 482759E 9 744 BS3199E 3 0 000000E 0 O 000000E 0 4 000000E 0 1 517241 9 1 073691E 0 O 000000E 0 0 000000E 0 4 000000E 0 1 551724E 9 906 720877E 3 0 000000E 0 0 000000E 0 4 000000E 0 1 586207E 9 388 825446E 3 O 000000E 0 0 000000E 0 4 000000E 0 1 620690E 9 1 048312E 0 O 000000E 0 0 000000E 0 4 000000E 0 1 655172E 9 1 192842E 0 0 000000E 0 0 000000E 0 4 000000E
10. ANTENNA TEST RANGE First Semester Report Fall 2009 By Aaron Kim Ryan Koenig Michael Turner Prepared to partially fulfill the requirements for ECE401 Department of Electrical and Computer Engineering Colorado State University Fort Collins Colorado 80523 Report Approved Dr Branislav Notaros Olvera Notaros ABSTRACT Antenna research has progressed significantly over the past decade however to conduct any research there needs to be one common resource an antenna test range This is because of the need to experiment on physical antennas due to the mathematical complexity of analyzing such antennas numerically Such systems that are offered commercially are very expensive and may not come packaged with features that are important The primary goal of this project is to create an antenna test range without the expensive price tag of commercial systems For this project we utilize numerous advanced research tools and knowledge from electromagnetic theory antenna measurement theory RF microwaves electronics communications computer hardware control theory power analysis mathematics computational algorithms and programming Beyond the research required for this project we will be working on developing a design analyzing the design modeling and simulating our system programming building testing budgeting installing and assessing on the management and design levels The design level includes work on the syst
11. a Figure 3 shows the geometry of this type of range Figure 3 Geometrical Arrangement of an Elevated Range Slant Range A slant range places the source antenna close to the ground while the test antenna is placed on top of a tower It is best to make the tower out of nonconducting materials in order to suppress reflections from the tower This type of system requires less real estate than an elevated range However it is important to have a smooth ground surface to prevent any reflections from the ground Again this type of arrangement is susceptible to outdoor weather Fiberglass tower 7 Test antenna N 4 30m N Source antenna Image Figure 4 Geometrical Arrangement of a Slant Range Compact Antenna Test Range CATR This type of range utilizes a reflector that reflects a signal towards the test antenna The reflector 1s specially built so the reflected signal becomes a plane wave field without having to cover a large distance This satisfies the far field criteria in a small space This is an extremely useful way to test the far field characteristics inside a small chamber The downside is getting a reflector The reflector cannot have a smooth edge and instead must have a serrated edge This is to suppress the diffraction that occurs Also the reflector must be large and parabolic with a strong enough mount to keep it stable _ CATR d y Test reflector Zone Me j Vertex Parabo
12. all the information they have the option to select Next or Home If Home is selected then then program moves to the Home state and the home screen of the GUI reappears upon which the user again has the choices described above If Next is pressed the program moves to the VNA Setup screen which allows the user to input parameters to setup the VNA For example one of the parameters that the user has the ability to select is the calibration file For more information on calibrating the VNA for your specific measurement please read Agilent s user manual for the device In the VNA setup screen is shown below the user has the option once again to click Home or if the user wishes to continue Run Measurement If the user selects Run Measurement the code moves to the Run Measurement state and changes the GUI screen to scan in progress Within this state is a Sub VI containing a state machine of its own responsible for sending commands to the motors moving them to the proper locations and then requesting a measurement from the VNA 19 Frequency 1 827586E 9 Hz Polarization 0 Degrees j Double click a frequency to display on the plot Polarization Azimuth Elevation Frequency dB O 000000E 0 0 000000E 0 3 000000E 0 1 827586E 9 1 128251E 0 0 000000 0 0 000000E 0 3 000000E 0 1 862069E 9 1 200794E 0 O 000000E 0 0 000000E 0 3 000000E 0 1 896552E 9 852 360010E 3 0 000000E 0 0 000000E 0 3 00
13. ation implements Microsoft DirectShow tools and was written in C NET using Microsoft Visual Studio 21 Logitech QuickCam Orbit AF Figure 19 Flowchart of the Camera System The Cameras communicate with the operating computer via USB The test operator will then open ATRCamApp directly from the LabView Control application which will display on a second monitor When ATRCamApp loads the COM ports containing the two camera sources are found The sources are then initialized for video capture and designated a display panel on the application window The operator starts the cameras by clicking on the appropriate button on the application window When this event occurs the cameras ate powered and the raw image data is gathered filtered with DirectShow and made visible on the application window No other functions were necessary given the static environment of the Chamber Once the cameras are mounted they will not be moved The light source in the chamber will also not change Because of the static nature of the system the provided Logitech software can be used to initially configure the cameras for enhanced capture response This small application with its simplicity and accessibility will enhance the operation of the Antenna Test Range 22 ee ES ss Cr Figure 20 Example Image from Camera Software 23 CHAPTER 4 PLANAR SCANNER The second scanner of interest is planar A planar scanner will facilitate two purposes
14. ave This is because the reactive element is much greater than the radiating element Other than the reactive field there is the radiating field In this region also called the Fresnel Region the radiation fields dominate and angular field distribution depends on the distance from the antenna Far Field This region is usually the region most antenna research is based around In this region we can assume the radiation pattern is independent of the distance from the antenna This is because at a large enough distance the travelling wave emitted from an antenna appears to look like a plane wave Reactive Radiating Near Field Field V Fresnel Zone Radiating Far Fiek Fraunhofer Zone gt 20 or r gt 10 Figure 7 Field Regions BASIC SYSTEM Now that we have established a large chunk of the theory we must now discuss the basic setup of a system To begin we have to establish the basic elements a source antenna and a test antenna According to the reciprocity rule the antenna we want to test can be on the source side or the measurement side However it is conventional to place the antenna under test AUT on the measurement side Figure 8 shows what we mean by source and test Test antenna Test positioner Receiver eee iad indicators Pattern recorder Signal Source satin antenna Polarization positioner Source tower Source Source os tower tower indicators
15. e stepper motor is heave and conductive The planar scanner will use a small plastic linear scanner to push a right angle arm that pivots at its vertex see Figure 13 This method will be much more cost effective lighter and less noisy in the system while still providing rotation for polarization up to 200 degrees Other mounting plates and supports will be designed to accommodate a variety of antennas f f f y Fer i 0 35 E E INEAR ACTUATOR OA o PL f 209 2 INEAR ACTUATOR gr el ey Al 0 a INEAR ACTUATOR n Figure 22 Polarization Sketch Up 29 CHAPTER 5 ELECTRONICS The electronic system consists of four main parts communication between software and circuitry via USB to RS232 the micro processor motor driver and movement device 1 e motor and linear actuator see Figure 23 The planar scanner will be controlled using electronics remaining from the spherical positioned Similar circuitry will be implemented because of the identical parts except for controlling the electrical linear actuator for the antenna mount The printed circuit board layout will be designed using the freeware application CadSoft Eagle While commercial electronic systems are available none will offer the custom design needed at a cost effective price USB to RS232 Atmel ATMega168 Allegro A3979 Motor Microprocessor Motor driver Linear Actuator
16. ected off the ground This is a design constraint that is unique to each reflection range This type of range is useful for understanding the reflective quality of antennas and also accommodates antennas that operate in the Ultra High Frequency UHF range Receive antenna Transmit antenna Range surface i I ransmit antenna image es Figure 2 Geometrical Arrangement for a Reflection Range The downside to using reflection range is choosing the right location to place one of these ranges This range is susceptible to inclement weather in the general area a common problem with outdoor ranges Also this type of range needs to be installed in a location with a smooth uniform ground in order to get the intended reflection This type of range is especially prone to interference from the surrounding environment FREE SPACE RANGES Unlike the reflection range a free space range aims to decrease contributions from the environment This accomplished through several methods which vary Elevated Ranges This type of range is very similar to a reflection range however this type of range is used to test very large antennas The antennas are usually mounted atop a tall building with a clear line of sight to the source antenna Again these types of ranges are susceptible to inclement weather as these antennas are usually too large to place indoors Another downside is the need for a tall tower or building and a large test are
17. em hardware electronics and processor levels The work that has been done sets the stage for the actual building and testing of the planar scanner system next semester Spring 2009 In conjunction with last year s project we hope to create a fully functional antenna test range for use with research and for enhancing curriculum in academic courses TABLE OF CONTENTS Contents Til E e doi occ i aio TV Issacs E vce A A reece ce thence ssa II 11 Olor raynro eltte ao A En oo O irre ntrrre E ont reer et cre 1 Fao 0 O crap Terre reer te er ee 1 fauaure ater Meastiement Lacoste err tr rte tr 2 ee BA ie A E T A se E e E E A E E shueutacstsestiacdt 2 E S E 2 tatoo gt APA E T A A A A A ree ee en ee 4 Mt PP 7 SAIS ego o AAN O er re rr eer ee 9 Chapter 4 Antenna Lest SO sirrane i RE E tert etre 11 foie 18S D Ea eeo ai A A A E O NU E re rrr 11 PE EEES E O E E E E EEEN 12 Peeran Developmentand OET O eian E E A A E EE 15 Ghapter o Test Chamber Mono ca Snes treerere aaeh aaiae a iaaa aani Ea i 21 Ehapter as Plant CO renee tern eter eer E tree rr rt ee re re eee 24 CE Gen rset acon o oi A nn E 26 Daie o AA Eno eo O O 29 ME Hea a gts cue UN E O EEE EEEE 29 Mechanical Desion and Aa rios 2 MES EGG A II INUNDA II 29 yoo lt 1 81Gb ect 10 010 cB Mara mr terre ert nore OOO O O Prat are ROT ee OTS Cory ont Teme re een 30 PBO E tre ner reer mr Tree i O Ue O re re 31 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Fi
18. evices required extensive testing to ensure the quality of the signal transmitted and received Antenna Measurement Theory Oftentimes antennas are very complex This poses a problem for analyzing antennas as the mathematical computations are very complex as well It is very impractical in terms of time spent to take on the analysis of an antenna As a remedial solution simulation software has been created to model these antennas Unfortunately the software available for simulating antennas is based on theory and because antennas are breaking new ground every few months we are not entirely sure if the theoretical models are accurate Therefore we need to test the antenna in a test range By physically testing the antenna and measuring the behavior we can analyze the results more accurately and with much mote speed To perform an antenna test we must have an antenna test range Which test range we want to use is a tricky question There are many types of test ranges and each offer benefits as well as shortcomings Determining which test range to use is crucial to getting a good test Below you will find two main types of ranges and a brief analysis on their benefits and shortcomings REFLECTION RANGES This is one of the two basic types of ranges A reflection range is useful for creating a quiet zone in the region of the test antenna Figure 2 shows the geometrical arrangement for such a range As you can see the signal is refl
19. gure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 LIST OF FIGURES Near Field Radiation of Cell Phone Near Human Head oooccnccccnonucnonnanonnanannanonnaninnanonnaninnacinnnss 1 Geometrical Arrangement for a Reflection Range uned dada debas 3 Geometrical Arrangement of an Elevated Rande calidad lit 4 Geometrical Arrangement of a Slant Rania 5 Contorno ere mrt 6 Aste Ae C1 Chanel S 7 Kiele INC OL OIG avisado ida 8 Example Lest SY SUSI aiaeseesstaulecd tases a a a a ons 9 Sane Methods i 10 Antenna Soriware LLO PER AA A A auien 12 Proc ram Tuntun ANG StALeS anto 13 Se A 14 A en ne ne RE Oe oF TEE SPOS SO ECD Or SOIT a Ree eer 15 User merice hone SC he Stl iaa 16 CONSUE motors SCEE sexes as a r tue ntact rasa chara ledaie aulent tidal aSatendarslsceleeiuud 17 Contiente VIN NSH C1 n T E Dade leet hehe deeeueied ced a ras 18 Run Measurement SU V dintel olor 19 Disparate cn 20 Elo wenarrot tae amero Sleep E E E 22 Example msc trom Camera SONWALE sotana ca 29 Panar scanner o REE U aaa Aa E nia 24 Po On orcas 25 Flowchart or EleCHONC arire e aa r a 26 Diastamvor the Stepper Moi ioien re ann a aaiiadtae 2I Two Possible Types of Outputs From Motor Dfrivef ooooonconnnonnnnnnononcnnnnnnonorororerenanncncncacaos 28 Grippo or PWM Sera a a A O ene 28 Expec
20. ishes to take another measurement the home button will take the program back to the home screen where the program can either be exited or a new measurement can be started 20 CHAPTER 3 TEST CHAMBER MONITORING Radiation within the anechoic chamber and moving equipment create an environment that is dangerous for humans In order to observe the antenna testing experiments cameras will be placed in the test chamber This allows the test operators to verify the orientation of the various scanners and know if emergency shutoff is needed Both transmitter and recetver antennas will be monitored using two Logitech QuickCam Orbit AF webcams This camera was chosen because of the shaft extension high resolution and light management The shaft extension is the most important feature The long shaft will allow the base of the camera to be shielded by anechoic foam which should reduce the interference with the test Once the test chamber is functional the amount of camera interference will be analyzed and changes with the camera mounting will be investigated and improved if needed The standard software provided by the camera does not support the viewing of two cameras in the same application This required a small application to be written that will display both camera images on the same screen with simplified controls for turning on both cameras This camera application will be referred to as ATRCamApp The programming of the applic
21. le Gary A Antenna ORBIT FR Antenna Measurement Theory Theory and Design Second Edition John Wiley ORBIT FR 2003 amp Sons 1998 Allegro Microsystems 43979 Microstepping Balanis Constantine Antenna Theory Analysis and DMOS Driver with Translator Allegro 2008 Design Second Edition John Wiley amp Sons Agilent Technologies PNA Series Programming 1997 Information and Examples Agilent Technologies 2009 31
22. lic surface 4 Figure 5 Configuration of a CATR Anechoic Chambers Last but certainly not least is the anechoic chamber This type of test range is kept indoors where the walls are covered in absorber material This material suppresses the reflected waves to keep the measurement isolated The absorber material is also shaped like a pyramid to prevent any diffractive waves from reflecting Also to prevent any environmental noise a layer of conductive material should be laid out underneath the absorber material This creates a Faraday Cage inside the chamber An anechoic chamber is useful for providing a silent room as well as enough space to perform far field measurements Unfortunately the absorber materials are expensive along with finding a large enough room for these experiments Finally it is worth mentioning that this project utilizes an anechoic chamber and all the developments we have made are to outfit this anechoic chamber Figure 6 Inside an Anechoic Chamber MEASUREMENT METHODS To perform a measurement assuming all the conditions for a measurement are satisfied we must choose what kind of measurement we want to perform There are two distinct categories near field and far field Near Field There are two subregions in the near field region reactive near field and radiating near field The reactive near field region is the region in which we are interested in the reactive element of the travelling w
23. on with the motor driver board Once all the information is retrieved the program moves to the Open Error Log state The only function of this state is to create and open a text file in the previously obtained program directory and name it Administrative Error Log Once that state is complete the program can now track and record errors within the program for debug purposes The next state executed is the About state which has the sole purpose of opening a pop up window displaying the program name and version number The 15 window is timed and vanishes programmatically after a few seconds saving the user from having to close it The last of the hard coded startup states is the Home state This state is responsible for changing the GUI to the home screen that allows the user to give input for the first time Welcome to the Antenna Test Range Software To begin press Configure Measurement Frequency 1 758621E 9 Hz Polarization 90 0 Degrees Configure Measurement Eat Figure 14 User interface home screen 16 Figure 15 Configure motors screen The home screen of the GUI shown below has two buttons in the lower right corner Each if these buttons triggers a different event within the code If the user presses Exit the code with move to the Exit state and then to the Clean Up state these states will be discussed later on 17 Configure VNA Configure measurement Select
24. ors in choosing the overall architecture of the software For this application the following factors were important when choosing the correct architecture e RS232 communication with the custom motor driver PCB e TCP IP communication with the VNA e Fast enough to process gain information from the VNA while scanning e User interface with moderate functionality o Must support user options o Allow for data to be exported 12 Considering these factors it was decided that the best program architecture for this system would be an event bases state machine A state machine allows for the code to be easily expanded upon while keeping it fast enough to process large amounts of data quickly Moreover support for events gives the user a great amount of functionally in the GUI The next step in the development process was to determine what states would be necessary in order to meet the project specifications The figure below shows what functions the software needs to perform and what states are necessary to perform each specified function As seen in the figure most of the states within the program are used in the program utilities section which is responsible for all connections error logging and closing all references when done Input user sours SEE defined defined VNA ee Display scan utilities sweep Results parameter parameters Intialize Array To Listbox Open Error Log About Run Home Motor Sweep VNA Setup Upda
25. te Graph Measurement Default Clean Up Export Data Exit Figure 11 Program functions and states With the required states now determined the next step is to figure out what order each of these states should be called This is accomplished by creating a state diagram which indicates the top level program flow and allows the programmer to begin coding the framework of the application Another key aspect to consider when creating the state diagram is the GUI design For this application we decided to use a wizard type GUI in order to simplify measurement configuration The wizard GUI asks for certain parameters from the user and chooses the next screen based on those parameters For 13 example anyone who has set up a printer on their home computer most likely encountered a wizard asking for parameters on multiple screens This is another key difference between the new application and the previously developed prototype which had a traditional GUI Shown in the figure below is the state diagram for the application From the start position on the diagram one can trace their way through the different states of the program After the first four states the yellow states execute automatically on program startup the code will stop and wait for user input When the user has finished inputting their desired parameters and clicks for example next it triggers an event in the code When the next button is pushed the
26. ted Dudo etario 30 CHAPTER 1 INTRODUCTION Due to the high saturation of electronics in today s society antenna research is an immensely hot topic Just in one day the number of times an average person uses an antenna is staggering This is all the motivation needed to foray into antenna research This chapter discusses the need for antenna research and presents current applications of such research Applications One recent application of antenna research that has received a dosage of media coverage is the cell phone and brain tumor link Using antenna test ranges as well as simulation software this topic has been researched extensively however the research is still inconclusive Using the test chamber we can measure the strength of the signal coming from a cell phone and deduce the possible biological effects it may have on the human body This can also be done for other electronics as well Figure 1 Near Field Radiation of Cell Phone Near Human Head With consumer electronics becoming smaller and smaller yet demanding a connection to the digital world it is no wonder there is an emphasis on the research and development of newer smaller more reliable antennas These can be applied in almost any modern day electronic device such as Global Positioning System GPS devices smart phones portable computing wireless networking Radio Frequency Identification RFID and many more Each of the antennas developed for these d
27. this application and ultimately lead to significant cuts in development time So exactly what is LabView one might ask To answer this one has to think of writing code in an entirely new way Normally when a programmer sits down and begins writing a piece of code they begin to typing line after line of code In LabView however the code is graphical not text based so a LabView developer would sit down and begin creating a block diagram not lines of text This is the fundamental difference between other languages like C and LabView This difference enables the programmer to see the program visually and in many cases increases the speed of development 11 es IIR l li ff ry hel P iie gt MINAS AEAN LATA lela Maansa t ye th j aili 4 het l q i os Me iihi y Meanjerert Rat Postor Restor Cegees Deta Ports Per Posbon Y oore Messazes WIA Messages mt 2 Pt 200 P30 P4 0 A2000 02000 52000 ve 425 00 M 591 A rr AS Figure 10 Antenna Software Prototype Program Architecture The first task of development is to choose a program architecture that best matches the application In order to accomplish this task it is necessary to know what the desired functions of the software are to be what other devices or programs the software will communicate with and what speed requirements must the software meet These among other requirements and specifications are important fact
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