OpenSynth PLL - Reactance Labs
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1. 1 lt lt PB3 set LD pin to input DDRD 1 lt lt PD2 set output PD2 LDO THIS IS THE VARIABLE DECLARATION SECTION uint32_t Nreg initialize the N Divider Register as a 32 bit integer uint32_t Rreg initialize the R Divider Register as a 32 bit integer uint32_t Creg initialize the Control Register as a 32 bit integer uint32_t NSreg initialize the Noise and Spur Register as a 32 bit integer THIS IS THE USER DATA SECTION Nreg 0x3FC060 set nominal value of Nreg Rreg 0x1440A1 set nominal value of Rreg Creg 0x0001E2 set nominal value of Creg NSreg 0x0003C7 set nominal value of NSreg THIS IS THE PROGRAM _delay_ms 100 Give the PLL a chance to boot up or whatever transfer 0x000003 11 Reset the Noise and Spur Register transfer NSreg 11 Set the Noise and Spur Register to nominal values Creg uint32_t 1 lt lt uint32_t 3 Enable the Counter Register by writing 1 to DB2 transfer Creg 16 Transfer the Control Register values with the enabled counter transfer Rreg 24 Load the R divider register values transfer Nreg 24 Load the N divider register values Creg amp uint32_t 1 lt lt uint32_t 3 Reset the Counter Register by writing 0 to DB2 transfer Creg 16 Reload the Control Register with the Counter disabled while 1 DDRD 1 lt lt LDO if PINB amp2. LED AER PD2 PD Extra I O lt PD4 PD5 GND Illustration 4 Microcontroller Pinout Green blocks indicate signal names PB3 ZER PB2 GEKEJ PB1 ATAl PBo ZER PDG The ATTiny2313 has an internal oscillator and requires no external parts to function As seen above in Illustration 4 there are 18 total I O pins in banks called PB PD and PA OpenSynth uses 4 pins to communicate with the PLL module LD Lock Detect CLK Clock DATA and LE Latch Enable LDO Lock Detect Output is an output line which lights an LED when the PLL is in a locked state It is tied to the 6 pin header connector as are PD3 PD5 which are extra I O pins available for programming for other uses PAO is tied to a red LED on the PCB and is also user definable as delivered this LED has no function 2 3 2 Synthesizer Programming Requirements Each MiniCircuits PLL module has a PLL controller chip which includes numerous functions requiring configuration In this section the KSN 2534A 119 module will be described This unit uses an Analog Devices ADF4153 The other modules use similar chips and require similar programming Four control registers require programming and are shown in Table 1 The ADF4153 is a Fractional N synthesizer requiring the setting of an Integer divider RO DB22 DB14 a Fractional divider DB13 DB2 a 12 bit modulus R1 DB13 DB2 There is also a reference divider R1 DB17 DB14 a reference doubler R2 DB11 a
3. 1 lt lt LD PORTD 1 lt lt LDO else PORTD amp 1 lt lt LDO return 0
4. R6 ATTI1 will vary between models of the OpenSynth PLL depending on the synthesizer used ATI 7dB PAT127CT ND Digikey Cl 10 uF 718 1760 1 ND Digikey C2 0 1 uF 478 1423 1 ND Digikey C3 1 uF 587 1291 1 ND Digikey C5 10 uF 490 5523 1 ND Digikey C6 0 1 uF 478 1423 1 ND Digikey C7 0 1 uF 478 1423 1 ND Digikey C9 1 uF 478 6247 1 ND Digikey Cll 10 uF 490 5523 1 ND Digikey C12 10 uF 718 1760 1 ND Digikey C13 0 1 uF 478 1423 1 ND Digikey C14 10 uF 718 1760 1 ND Digikey C15 0 1 uF 478 1423 1 ND Digikey C16 15 pF 478 6576 1 ND Digikey C17 15 pF 478 6576 1 ND Digikey Jl HEADER WM4204 ND Digikey IR 6PH 609 3202 ND Digikey J3 REF IN CONSMA003 062 ND Digikey J4 RF OUT CONSMA003 062 ND Digikey LEDI Green 160 1169 1 ND Digikey LED2 Red 160 1167 1 ND Digikey Ql 2N2222 PZT2222ACT ND Digikey Q2 2N2222 PZT2222ACT ND Digikey Q3 ERA 2SM ERA 2SM MiniCircuits RI 4 87k ohms P4 87KCCT ND Digikey R2 680 ohms P680ACT ND Digikey R3 10k ohms Digikey R4 69 8 ohms P69 8CCT ND Digikey R5 150 ohms P150ACT ND Digikey R6 215 ohms P215CCT ND Digikey R7 150 ohms P150ACT ND Digikey R8 120 ohms P120ACT ND Digikey R9 215 ohms P215AACT ND Digikey R10 150 ohms P150ACT ND Digikey Ul ATTiny23 13 ATTINY2313V 10SU ND Digikey U2 KSN 2534 119 KSN 2534 119 MiniCircuits U3 LT1762 LT1762EMS8 PBF ND Digikey U4 ADR440 ADR440ARMZ Digikey US LT1678 LT1678CS8 PBF ND Digikey U6 NCP1117 NCP1117ST33T3GOSCT ND Digikey 4 3 Microcontroller Source Code This code was writ
5. 4 KSN 3500A 119 3312 MHz 7 Take a moment to verify there are no shorts in the circuit by applying 12V as in the previous step and monitor the DC current to make sure that it does not exceed 100 mA should be well below this 3 2 7 LEDs Of the two LEDs installed only one of them LED1 is used with the default programming of the microcontroller and serves as a lock indicator LED2 is available for use by users who want additional status or even as a power on indicator etc These features require additional programming of the microcontroller Locate the following components R8 R10 LED1 LED2 Install the LEDs and resistors as shown Take special attention to observe the tiny green stripe at the cathode end of the LEDs You may have to tilt the LED slightly to see it hotograph 13 Close Up detail of the LED orientation The LEDs should be tested with the 12V disconnected Instead apply 3 3V to the pads indicated below to observe the function of each LED Ween Se Photograph 14 LED Testing points 3 2 8 Microcontroller Locate and install U1 the ATTiny2313 Microcontroller as shown below Photograph 15 Installed microcontroller Again take a moment to verify no shorts by powering up the circuit with 12V as before 3 2 9 Synthesizer Module Installation Locate and install U2 the MiniCircuits PLL module as below Not the orientation of the part to the board spec
6. components as shown below observing the polarity for C12 and C14 the polarized tantalum capacitors Photograph 7 Component locations for voltage regulator output components gt O O O O O O O O O Test Point 3 Once all the components are installed as above it is important to test the outputs to make sure the circuit is working Use the photograph below and probe at the indicated test points in accordance with Table 2 Record the values for TP3 TP4 and 12V in the table for future reference TP3 is the PLL supply voltage and TP4 is the VCO supply voltage Each are measured on the positive terminal of the black tantalum capacitors shown below Apply 12V as in the previous two sections Photograph 8 Voltage Regulator Components Installed Table 6 Voltage Regulator Test Table Label Description Measured Value TP3 PLL Supply Voltage see Table 4 or 5 for which voltage to expect TP4 VCO Supply Voltage see Table 4 or 5 for which voltage to expect 12V 12V Input 3 2 4 Buffer Amplifier Wire The final components to be installed on the back side of the board is the jumper wire Install the wire as shown below Photograph 9 Location of jumper wire Take a moment to verify that the resistance between TPS and TP6 is 215 ohms 3 2 5 3 3V Regulator The microcontroller runs off 3 3V and requires a regulator These components are to be installed onto the top side of the board Locat
7. controls all should be left alone The Counter Reset is changed in the programming sequence described later More details on all these functions can be found in the data sheet of the PLL chip The part number is indicated on each MiniCircuits PLL module data sheet For the ADF4153 the following programming sequence is required 1 Delay 100 msec this is to let the voltage regulators stabilize 2 Reset the Noise and Spur Register R3 send 0x000003 3 Set Noise and Spur Register R3 to nominal values see table above 4 Set Control Register with Counter set 5 Set R divider 6 Set N divider 7 Set Control Register with Counter reset Values sent to the PLL module are in hex To determine the hex value convert the 24 bit binary values above into a hex number To determine what values to program and how to set the dividers refer to the PLL IC data sheet It gives the required equations and examples to determine the proper values Often there are multiple solutions and in general it is preferred to keep the reference divider value as low as possible to maintain good phase noise 2 3 3 Microcontroller Functional Code Description The OpenSynth code is straightforward A function called transfer does most of the work in actually generating the signals going to the PLL module Specifically the transfer function generates clock pulses data pulses and sets and resets the Latch Enable which clocks in data after sending all of it The
8. remainder of the program simply calls transfer and supplies it with the relevant data word and word length This is done in accordance with the order of commands specified in the PLL chip datasheets A final element of the code checks the status of the Lock Detect output of the PLL and lights the LED when in lock 2 3 4 Microcontroller Programming Resources If you are new to programming microcontrollers there are many great resources for learning about how to program Programming in the C language for microcontrollers is slightly different than for a computer bit wise operations are used much more extensively for instance Also to program a OpenSynth board you ll need an In circuit Serial Programmer ISP which can be purchased at very reasonable prices from Atmel or other vendors Here are a few links to check out on programming Atmel microcontrollers Atmel s AVR series of microcontrollers http www atmel com products AVR In Circuit Serial Programming Tools http www atmel com dyn products tools_card asp tool_id 3808 http www adafruit com products 46 http www adafruit com products 26 cheapest option 7 50 Comprehensive basic introduction to programming AVRs http hackaday com 2010 10 23 avr programming introduction Bit Manipulation techniques The AVRfreaks net forum is a great resource in general http www avrfreaks net index php name PNphpBB2 amp file viewtopic amp t 37871 http Awww cpro
9. require multiple power supplies to run properly In the case of the MiniCircuits PLL modules used in this design two separate voltages are required a VCO supply and a PLL supply Due to the very high gain of the VCO any voltage noise on its supply will end up magnified greatly in the output signal taking the form of phase noise or equivalently timing jitter The OpenSynth PLL features a pair of ultra low noise discrete voltage regulators Originally the circuit was designed with common LM317s but their contribution to phase noise was excessive The addition of the more complex and costly discrete regulators improved the close in phase noise by 10 15 dB 12V Low Pass Low Noise SR Op Amp ADR440 Precision Voltage Reference Illustration 3 Schematic diagram of the discrete voltage regulators Integrated ultra low noise regulator solutions exist but they tend to have a couple key limitations which preclude their use in this kit First most are available in packages that require reflow soldering for which many builders lack the required specialized equipment Secondly most of them are limited to 5 5V output At least one of the MiniCircuits PLL modules requires 7V and the discrete regulators in this circuit achieve that easily Illustration 3 shows the schematic diagram of the voltage regulators used for the PLL and VCO supplies A single reference voltage source Analog Devices ADR440 provides an ultra clean 2 048V referenc
10. REACTANCE LABS JH OpenSynth PLL Construction Guide and User s Manual Version 2 1 September 2012 Tony Long tony reactancelabs com Tony Long 2011 These materials are Open Source licensed under Creative Commons Attribution 3 0 Unported license See http creativecommons org licenses by 3 0 for details Table of Contents 1 Basic Overview 1 1 Basic Description Features 1 2 Uses 1 3 Basic Block Diagram and Design Philosophy 2 How It Works 2 1 Phase Locked Loop Synthesizer Basics 2 2 Voltage Regulators 2 3 Microcontroller and Code 2 3 1 Microcontroller Hardware Synthesizer Programming Requirements 2 3 3 Microcontroller Functional Code Description Microcontroller Programming Resources 3 How to Build it IF IMPATIENT START HERE 3 1 Introduction 3 2 Step by Step Instructions 3 2 1 RF Connector Installation 3 2 2 Voltage Reference Filter Capacitors 3 2 3 Voltage Regulator Components 3 2 4 Buffer Amplifier Wire 3 2 5 3 3V Regulator 3 2 6 Buffer Amplifier 3 2 7 LEDs Microcontroller 3 2 9 Synthesizer Module Installation 3 2 10 Connectors Heat Sink and Final Inspection Test 3 3 Recommendations for use installation 4 Documentation 4 1 Schematic Diagram 4 2 Bill of Materials 4 3 Microcontroller Code 1 1 Basic Description The OpenSynth PLL kit you now have in front of you is a collection of parts needed to construct a low phase noise miniature fr
11. e and install C11 and U6 as below Photograph 10 Installation of the 3 3V regulator and filter capacitor Test Point 4 Once the 3 3V regulator and filter capacitor are installed as above it is important to test the output to make sure the circuit is working Use the photograph below and probe at the indicated test points in accordance with Table 7 Apply 12V at the 12V pin and record the values for TP7 and 12V in the table for future reference Table 7 LDO Regulator Test Table Label Description Measured Value TP7 Regulator Output nominally 3 3V Pin 20 of U1 12V 12V Input GROUND Ground return 3 2 6 Buffer Amplifier In addition to providing extra output power the buffer amplifier isolates the output of the PLL from whatever load may be attached to the OpenSynth PLL board Locate the following components C26 C17 Q3 ATT1 Install the components as in the photograph below Take care to note the orientation of Q3 as well as ATI If ATT is not installed properly as shown the output power will be substantially lower than expected Each kit is supplied with a range of values for ATT1 See Table 8 below for suggested values Photograph 11 Installation of the buffer amplifier components Table 8 Attenuator value suggestions MiniCircuits P N Frequency typical Attenuator Value dB KSN 1150A 119 1152 MHz 4 KSN 2170A 219 2160 MHz 4 KSN 2534A 119 2556 MHz
12. e which is then further filtered by a low pass filter 16 Hz corner frequency before getting to the Linear Technology LT1678 dual low noise op amp A 2N2222 NPN transistor and voltage divider complete the feedback loop forming the remainder of the regulator circuit This feedback circuit acts not only to maintain the proper voltage but also to reject the noise on the 10V supply The microcontroller has its own 3 3V regulator 2 3 Microcontroller and Code The PLL chip within the MiniCircuits modules must be configured each time it is powered up OpenSynth PLL uses a microcontroller to send the appropriate commands to the PLL chip any of several Analog Devices PLL synthesizer chips As shipped each microcontroller is pre programmed to the frequency specified when ordering Provisions are made on the board for user reprogramming using any of several programmers including the inexpensive AVRISP from Atmel Source code is available on the Reactance Labs website as well as in this document 2 3 1 Microcontroller Hardware The microcontroller used in this circuit is an 8 bit Atmel ATTiny2313 This microcontroller was chosen for ease of programming free C compilers exist and are well supported its popularity in the hobbyist community and its large amount of I O pins It is an excessive microcontroller for the application but allows for additional applications which users may choose to implement PA2 vcc PDO PB7 PD1 PB6 PA1 PBS LED2 PAO PB4
13. equency synthesizer You probably already know this What you may not know is that the synthesizer features the following Miniature Size 1 5 by 2 Low Phase Noise Low DC Power Consumption Open Source Design Extra I O for Customization Buffered Output Specifications depend on synthesizer module used 1 2 Uses This kit was designed to provide a local oscillator LO for amateur receivers and transmitters operating at UHF and beyond At the heart of the OpenSynth PLL is a phase locked loop PLL module made by MiniCircuits the large metal can part in the kit These synthesizer modules are available in a wide range of frequencies 300 MHz to 4 GHz in narrow bands in the same physical footprint and pinout This affords great flexibility in the planning of multiplied LO or multiple conversion architectures while maintaining both low phase noise and power consumption Another feature of the OpenSynth PLL is the open nature of the design All design files and source code are freely available and may be used under the condition of attribution only That is to say anyone can freely take the design and modify reuse repackage resell it with the only condition that attribution to Reactance Labs is stated Because the microcontroller code is open source and the microcontroller is very common in the hobbyist community modification to the code can be made to enable new features Other uses include some require addit
14. gramming com tutorial bitwise_operators html http www avrfreaks net index php name PNphpBB2 amp file viewtopic amp t 97219 3 1 Introduction The OpenSynth PLL is not a beginner s kit but should not present a challenge to experienced builders of microwave electronics With the exception of the connectors all components are surface mount Several of the components are ESD sensitive so take care to handle and build this kit in an ESD controlled environment A grounded through a 1 Mohm resistor ESD wrist strap and soldering iron should be used at all times when handling and assembling parts or the finished kit Many hobbyists and engineers alike discount the significance of ESD but to ensure that your synthesizer performs well for a long time it is important to follow good ESD practices Creating good solder joints is helped by using paste flux and soaking up excess solder with solder braid It is crucial to clean flux from the board as it can cause performance problems in the long term The following tools are recommended for the assembly of the OpenSynth PLL kit ESD grounded temperature controlled soldering iron with fine tip Fine gauge solder Desoldering braid Paste flux A vise for holding the board Magnifying glass microscope Diagonal wire cutter Wire stripper Hobby knife Isopropyl alcohol Cotton swabs 3 2 Step by Step Instructions The OpenSynth PLL assembly is organized in a manner to allow incremental te
15. he Installation of the remaining components of the voltage regulator and filter capacitors for the PLL and VCO supply lines Locate the following components R4 R7 Q1 Q2 U5 R4 and R6 set the voltage for the PLL and VCO circuits respectively There are 4 different voltages required by the various MiniCircuits modules 3 0 3 3 5 7 V Refer to Table 4 below for common values or if you need to change values for another module refer to Table 5 Finally for any generic voltage you can use Equation 1 to determine what value you need Table 4 Resistor values for commonly used Synthesizer Modules MiniCircuits P N Frequency typical PLL Voltage VCO Voltage R4 Rp KSN 1150A 119 1152 MHz 5 5 215 215 KSN 2170A 219 2160 MHz 5 5 215 215 KSN 2534A 119 2556 MHz 3 5 69 8 215 KSN 3500A 119 3312 MHz 3 7 69 8 360 Table 5 Resistor values for all four possible voltages Voltage PLL or VCO Resistor Value R4 or R6 3 69 8 3 3 91 5 215 7 360 R 150 AN 2 048 150 quation 1 Equation to determine resistor values Refer to the following photograph for component positions ale 2716 9 1678 ui Le E O D w a oO S R Y w S K S O x k E lt Y s S 9 oO N je w v E Si gt lt S x oO N N F En S A Locate the following components R9 C10 C12 C15 C18 Install the
16. ifically that of the text label on the lid Soldering the leads may take some patience and definitely a fine tipped soldering iron hotograph 16 PLL Module Installed 3 2 10 Connectors Heat Sink and Final Inspection Test The last parts to be assembled are the programming header and the power control connector Finally if you have not already done so solder each end of the PLL Synthesizer lid to the circuit board This ensure a good ground connection Le e e ACTANCE o ix o s ek Photograph 18 Lid soldered to board The last step is the installation of the heat sink Remove the adhesive tape cover from the heat sink and stick onto the top of the silver PLL synthesizer module Construction is now complete Take a few minutes to carefully inspect all the solder joints spaces between pins and remove any remaining solder flux solder splatter etc After you have carefully inspected the board connect a 10 MHz reference 0 dBm to the REF port and measure the output of your synthesizer on your favorite spectrum analyzer power meter or frequency counter If you have any questions comments or need assistance feel free to email tony reactancelabs com 3 3 Recommendations for Use Installation Your OpenSynth PLL board can be mounted in a number of ways First is by using 4 standoffs and screws and mounting to a plate Another method is to mount the board on a panel using the SMA connectors f
17. ional code and or hardware LO Source with switchable offset useful for mixer only millimeterwave radios where the IF may not used during a CW transmission Beacon Transmitter With CW ID Test Source Frequency Hopped Source Remotely Activated Transmitter Narrow Band Swept Source Microcontroller can be used for T R sequencing or other uses in addition to PLL control 1 3 Basic Block Diagram and Design Philosophy 12V Input 3 3V vco PLL Regulator Regulator Regulator Microcontroller MiniCircuits PLL Module Output Ref Input Illustration 1 Block Diagram of the OpenSynth PLL The primary design goal for the OpenSynth kit was to develop a flexible circuit which would interface with the wide variety of synthesizer modules presently manufactured by MiniCircuits for use as LO sources for amateur microwave radios The desire for several key characteristics led to the final design low phase noise useful output power level low power consumption compact size buildable by experienced kit builders with basic tools open design for expandability and modification customization With the exception of the output stage all components have voltage regulators to maintain performance under conditions of uncertain input power such as when operating by battery power in a remote location Most modern high performance RF components are surface mount and it is expected that most people building a microwave radio ha
18. nd a bunch of other miscellaneous registers that require setting In particular the CP Polarity and PD Polarity are set by the VCO and loop filter characteristics These values are supplied in the PLL module data sheets provided by MiniCircuits v x e 9 9 bit Integer Value INT 12 bit Fractional Value FRAC Control Bits RO DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 D I DBO 0 0 D 3E 8 8 5 MUXOUT CG Q 4 bit R counter 12 bit Interpolator Modulus Value MOD Control Bits DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DBO 0 0 1 S D CO e 5 ss ee s Resync a a CE Current pop 2 Es Control Bits 2 0 Setting 8 g R 2 A o o D O x a O DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 D I DBO d 0 oO 3 E 2 Noise And Spur Mode Reserved H Control Bits 3 5 R3 Z DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 D I DBO 0 eae JE 1 Table 1 Programming Registers for ADF 4153 to generate 2556 MHz Fast Lock Load Control Prescalar Resync CP 2 LDP Power Down CP Three State Counter Reset Control Bits and Reserved and the Noise and Spur Mode
19. on signal which is amplified and then filtered by the Loop Filter ultimately commanding the VCO to move forward or backward in phase until the two oscillators are in sync This condition is called phase lock and is maintained as long as the drift of the VCO is within the tracking range of the circuit A successful PLL synthesizer design results in a circuit that produces a spectrally pure signal low phase noise and low spurious signal levels and locks up quickly and reliably under varying temperatures and component drift The majority of the design work in modern integrated circuit implementations is the design of the loop filter which usually takes the form of a low noise op amp filter circuit In high performance narrowband applications such as required for amateur microwave transceivers a narrow band VCO is used It is often the case that some oddball frequency is required when building a radio especially in multiple conversion architectures The difficulty is that for each frequency a new PLL circuit must be designed OpenSynth takes advantage of a large collection of designs done by MiniCircuits to enable rapid construction of high quality signal sources These PLL modules are available in a wide range of frequency bands with some gaps from about 500 MHz to 4 GHz Any of the synthesizers in the DK1042 and DK801 package style will work with the OpenSynth circuit board 2 2 Voltage Regulators PLL synthesizers often
20. or support If you choose this method make sure to install the connectors as in the assembly guide to avoid stress induced damage when securing the nuts on the connectors The following drawing should help guide the installation of the OpenSynth PLL in whatever application you intend Holes are 0 125 inch 3 175 mm in diameter 138 4 mm Y wits 3 81 mm 0 58 14 7 mm 1 68 42 67 mm lt 2 0 50 8 mm Illustration 5 Hole Pattern for the OpenSynth PLL Documentation 4 0 Schematic Diagram 4 1 210271271 Bue Auo 1 ebe ZHW 9SS2 Td HINAS N3d0 sge7 ALE joe oy J39 S1 219 100 11 gt JN 1 0 dn l Ab Pl gt 0096 295 TREES Ae Be gt 77 19 el 219 en An 1 8 3n oi V 61 l pEG2 NSX 4 z1s uquhs Wd swyo S12 3d S1 919 62 nel Oud Hecht 90d oad lad ead ead vad Ye OUUOIOUD 1 C1SOW SEd COSIN 98d ASIN 2d ZC Hdd 4O1S uuO9 dSI eege 431 11dw J jjng INO 1 Ind JJ Sdd vad Eld edd Yd V D H ebe SE Eege An 1 NAI a ebey eteevezve 5uoq Ruol ZHW 9SS2 Wd HINAS N3d0 sgel Sue32e 2jJ Suuo BSI 94291u 292 v 4oqeI nB 2 A4 I O43uooSodJor suojzetn6sy gan pue Wd a d a ey bn Obrany Su J gj 2a Be3a oA UOTStIaug 4 2 Bill of Materials The following bill of materials BOM was compiled for the 2556 MHz synthesizer Values of R4
21. s The next step Involves the assembly of the voltage reference and input output filter capacitors Locate the following components C1 C5 C4 is omitted R1 R2 U3 The bottom side of the circuit board has no silkscreen so refer to the following graphics for placement guidance Photograph 4 Voltage Reference and filter capacitor installation locations U4 is a fine pitch part and requires very careful attention to placement and soldering One suggestion is to solder two pins on a diagonal to anchor the part before soldering the remaining leads It is highly recommended that after soldering the part be inspected under a microscope to identify any shorts between pins C1 is the only polarized capacitor in this section Observe the orientation of both U4 and C1 in the photograph above Test Point 1 Once the precision voltage reference and input filter capacitors are installed as above it is important to test the output to make sure the circuit is working Use the photograph below and probe at the indicated test points in accordance with Table 2 Apply 12V at the 12V pin and record the values for TP1 and 12V in the table for future reference Photograph 5 Test points for the LDO regulator Table 2 LDO Regulator Test Table Label Description Measured Value TP1 Vref Output nominally 2 048V 12V 12V Input GROUND Ground return N A 3 2 3 Voltage Regulator Components This section describes t
22. sting of circuit elements before the next step of assembly This assures that when they most sensitive components are placed they will not be damaged It is recommended that assembly follow the steps below rather than all at once 3 2 1 RF Connector Installation Photograph 1 Various views of the SMA connectors used on the OpenSynth board The two SMA connectors are the first parts to be installed These connectors require some care to install and solder After carefully aligning the connectors to the board ensure that the center pins are truly centered on their pads solder just the center pins down Next solder the SMA connector ground legs to the board This step requires some patience and solder flux Applying the flux prior to soldering helps considerably in wetting the solder to the legs and the board Additionally it is recommended that heat be applied to the legs themselves until solder flows on them as they have a higher thermal capacity than the thin metal of the circuit board Take care to avoid using too much heat especially if using a hot air gun to preheat the joint as the center contact can come loose and alignment will be lost Your solder joints should look like those in photographs 2 and 3 below n H it g Open PUL kh A Se 34 et e e SL of o al SIP Rev 1 0 S o CS WER m TEO Photograph 3 An example of good solder joints on the back side of the PCB 3 2 2 Voltage Reference and Filter Capacitor
23. ten for the 2556 MHz model MiniSynth_KSN 2534 2556 c Created 12 17 2011 12 56 08 PM Author Tony Long KC6QHP include lt avr io h gt include lt util delay h gt define CLK PB2 Clock output line to synthesizer module define DATA PB1 Data output line to synthesizer module define LE PBO Latch enable define LD PB3 Lock detect INPUT from synthesizer module define LDO PD2 Lock detect OUTPUT pin to LED anode and lock pad on PCB void transfer uint32_t nData uint8_t nNumBits uint8 tj initialize the j variable used in the loop PORTB amp 1 lt lt LE Set LE low PORTB amp 1 lt lt CLK Set CLK low _delay_us 50 Delay for LE setup time gt 20 nsec for j 0 j lt nNumBits j if nData amp uint32_t 1 lt lt nNumBits 1 j PORTB 1 lt lt DATA set DATA output pin to high else PORTB amp 1 lt lt DATA set DATA output to low _delay_us 20 PORTB 1 lt lt CLK Set CLK high This is the clock pulse that clocks in data _delay_us 20 PORTB amp 1 lt lt CLK Set CLK low This is the end of the pulse _delay_us 20 PORTB 1 lt lt LE set LE high _delay_us 100 Delay for LE hold time PORTB amp 1 lt lt LE Set LE low _delay_us 50 int main void DDRB 1 lt lt PBO0 1 lt lt PB1 1 lt lt PB2 set outputs PBO CLK PB1 DATA PB2 LE DDRB amp
24. ve experience soldering tiny components Certain SMT components were excluded however specifically those that require reflow soldering techniques 2 1 Phase Locked Loop Synthesizer Basics The OpenSynth PLL kit incorporates a PLL frequency synthesizer Since its initial introduction in the 1930 s the PLL controlled oscillator circuit has been gaining popularity This increase in popularity accelerated rapidly in the 1970 s with the introduction of integrated circuit IC packaged PLL solutions Modern PLL ICs are smaller and operate at higher frequencies due to advanced semiconductor and packaging technologies PLL synthesizers generally make excellent LOs for microwave radios as they can be extremely stable in frequency and when properly designed exhibit very low phase noise A PLL frequency synthesizer operates by comparing two independent oscillators and adjusting the frequency and phase of one to match the other the reference The oscillator being adjusted is commonly a Voltage Controlled Oscillator VCO Reference Phase Loop Oscillator Detector Filter vco ei Divider Illustration 2 Phase Locked Loop Frequency Synthesizer Diagram In Illustration 2 the main blocks of a PLL synthesizer are shown Synthesis begins with the startup of the Reference Oscillator and VCO Initially these two may be running at slightly different frequencies and certainly with different phase The Phase Detector compares the two and generates a correcti
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