Agile PLL

Agile PLL


VK3XDK Agile 10 MHz-Lockable PLL Synthesizer           

Jointly developed in 2010 by Graham Byrnes, VK3XDK, and David Smith,VK3HZ, this PLL Synthesizer board covers from approximately 432MHz to almost 2000 MHz over three ranges;

            Range 1: 432 - 800MHz          (Typical lock range: 414 - 562MHz)      

            Range 2: 800 - 1400MHz        (Typical lock range: 1040 - 1393MHz)

            Range 3: 1400 - 2000MHz      (Typical lock range: 1567 - 2070MHz)

Board features

  • ·         small footprint (only 62mm x  58mm)                                                         
  • ·         delivers approx 0dbm over full range
  • ·         utilises an Si4133G-bt PLL/VCO IC
  • ·         PICAXE controller, end-user programmable
  • ·         requires external 10MHz reference @ 0-5dBm
  • ·         optional MMIC for higher output level
  • ·         requires 8VDC @ 20mA                                                        

 


This PLL Synthesizer board is small and very versatile - use it as a reference source, or as an injection oscillator.

It requires an external 10MHz reference signal @ approx 0 - 5dBm, either from a GPS-locked source, or from an Oven Controlled Crystal Oscillator (OCXO).

A regulated 8V DC supply is required, which is easily obtained using a LM7808 voltage regulator (with appropriate bypass capacitors), fed from your 12VDC or 13.8VDC supply.

Provision on the PCB allows for adding an optional MMIC IC for increasing the output to over 10dbm.   Higher output will produce "handy harmonics" right up to 10.368GHz, and becomes useful for a field frequency reference, especially when GPS Locked.

Note: Complete 432 - 2000MHz range is not available without gaps!

Price is $100 + P&P approx $5 (within Australia) for a fully built up and tested board.

Please direct availability and postage enquires to Graham, VK3XDK,  grumss@yahoo.com.au

(Sorry - due to the small size of the SMD si4133 IC and soldering difficulties, kits will not be available)

PICAXE Controller

A PICAXE controller was chosen, and with a great deal of help from David VK3HZ, we have developed "PICAXE BASIC" coding that allows easy changes to be done by the end-user.

16 "standard" frequencies are programmed into the internal eEPROM in the first 16 lines of code.

Frequencies are stored on the PICAXE Microcontroller and programming has been set up so that most people can readily Edit the frequencies using PICAXE Editor Freeware.

To change any of the pre-programmed frequencies, three pads on the PCB are provided, to enable hooking up a temporary three-wire serial interface to a standard PICAXE programming lead. 

PICAXE programming leads available from PICAXE stockist in both USB and DB9 Com port variants.

No special programmer is necessary, and PICAXE editor software is free - see PICAXE website.

It's just a matter of converting a frequency of your choice to HEX and then replace an/any existing Data value with this new HEX value (LSB,MSB).

Any new code is then loaded via the Serial Interface into the PLL, and stored permanently.

It’s actually quite a simple process, and people with no programming experience should be able to work it out fairly quickly!

If anyone is interested in seeing the code, send VK3XDK an email, and it can be viewed on Notepad or PICAXE Programming Editor (freeware)

 

Code Versions

The Si4133 chip used is meant for a 13MHz reference, but with programming, a 10MHz Reference is accommodated.

Please note – due to the redesign to cater for 10 MHz Reference (in lieu of 13MHz), only EVEN, WHOLE MHZ values can be programmed with a 10MHz reference.

Alternative code is available to suit a 13MHz Reference will allows both EVEN or ODD MHz values.

Standard Pre-programmed Frequencies

A 4-way DIP Switch on the board allows convenient preset frequency selection, and the PICAXE is pre-programmed with the following standard frequency set:

HEX Add     FREQUENCY CONTENTS (MHz)

 

F, 15       1008 - x3 = 3024 MHz Injection: with 432 MHz IF for 3456 (USA)

E, 14       1066 - x5 = 5330 MHz Injection: with 430.1 MHz IF for 5760.1

D, 13       1104 - x3 = 3312 MHz Injection: with 144 MHz IF for 3456

C, 12       1134 - x3 = 3402 MHz Reference: (tuned by the IF going up 2MHz)

B, 11       1152 - for MANY options: see note below.

A, 10       1202 - x2 = 2404, 2403 MHz Reference: (tuned by IF going up 1 MHz)

9, 9        1242 - x8 = 9936 MHz Injection

8, 8        1278 - x2 = 2556 x4 = 10224MHz Injection: with 144MHz IF for 10368

7, 7        1296 - x8 = 10368 MHz Reference

6, 6        1332 - x2 = 2664 & x4 = 5328 MHz Injection: with 432MHz IF for 5760

5, 5        1336 - x18 = 24048 MHz Reference

4, 4        1344 - x18 = 24192 MHz Reference (USA)

3, 3        1656 - x6 = 9936 MHz Injection: with 432MHz IF for 10368

2, 2        1700 - x2 = 3400 MHz Reference

1, 1        1776 - x3 = 5328 MHz Injection: with 432MHz IF for 5760

0, 0        1872 - x3 = 5616 MHz Injection: with 144MHz IF for 5760

 

The actual PICAXE code, at the top of the program, looks similar to this:

eeprom 0,($f0,$03)      ;1008 (ie: 1008MHz in hex notation (LSB, MSB) = $F0,$03)

eeprom 2,($2a,$04)      ;1066

eeprom 4,($50,$04)      ;1104

eeprom 6,($6e,$04)      ;1134

eeprom 8,($80,$04)      ;1152

eeprom 10,($b2,$04)     ;1202

eeprom 12,($da,$04)     ;1242

eeprom 14,($fe,$04)     ;1278

eeprom 16,($10,$05)     ;1296

eeprom 18,($34,$05)     ;1332

eeprom 20,($38,$05)     ;1336

eeprom 22,($40,$05)     ;1344

eeprom 24,($78,$06)     ;1656

eeprom 26,($a4,$06)     ;1700

eeprom 28,($f0,$06)     ;1776

eeprom 30,($50,$07)     ;1872

 

1152 MHz

One frequency of special interest is 1152 MHz.

1152, x2 = 2304 MHz (USA)                   1152, x3 = 3456 MHz (USA)                   1152, x5 = 5760 MHz

1152, x9 = 10368 MHz                           1152, x21 =24192 MHz (USA)


Output Buffering;

The standard PLL has an output level of between -5 to 0dDm.  Since this may be too low for some applications, there is space on the PCB for an optional MMIC buffer stage.

Cut the track under where the MMIC would be fitted, and add the 27nH bias inductor.

Tested so far are;

ERA1 - around 10dbm O/P (@ fundamental freq) with good loud harmonics up to 10GHz (typically -55 dBm or better).

ERA2 - around 13dbm O/P with a lot cleaner signal. Ideal for an Injection source.  Excellent results have been achieved at 1970MHz (for a 2.4GHz LO) where it delivers >7dbm for Mixers (two outputs using 1/4 divider).

ERA3 - not tested yet, but should be rich in handy harmonics up to 10GHz.

Other MMICs may be good depending on voltage (3.3V) and required spectrum.

MMIC BIAS inductor is found to be around 27nH.

 

The table below indicates the gain offered when an ERA2 MMIC is fitted to the board.

Freq

Output Level
Without ERA 2

Output Level
with ERA2

1728MHz

-3dBm

+11dBm

3456MHz

-31dBm

-14dBm

5184MHz

-28dBm

-17dBm

6192MHz

-44dBm

-39dBm

8640MHz

-65dBm

-33dBm

10368MHz

-65dBm

-47dBm

 

For use as a Reference Frequency:          Harmonics are excellent.(with ERA1 buffer)

For use as an Injection Source:                 Feed Output to appropriate Multiplier chain(s)

Inductor Range Setting:

The three VCO’s within the Si4133 IC use external inductors, and set the appropriate “centre” frequencies.

(See Si4133 data sheet for more detailed information)

Inductors have been roughly set for the standard set of frequencies. If some frequencies are not locking, small (VERY small) adjustments may be needed.

Take care if you choose to adjust the inductors, a little can be a LOT.

 

Inductor ranges and VCO crossover frequencies

The SMD inductor across pins 19 & 20 sets 430MHz - 800MHz output at RF2 SMA O/P connector.

Small printed PCB inductor across pins 7 & 8 sets 1400MHz - 1970MHz output at RF1 SMA O/P connector.  This inductor short is often placed right across pins 7 and 8 of the si4133 IC itself - this is not a soldering error!

Large printed PCB inductor across pins 4 & 5 sets 800MHz - 1400MHz at RF1 SMA O/P connector.


Miscellaneous Notes

PLEASE NOTE:    8VDC MAXIMUM supply voltage

It has been found that higher than 8V may destroy the on-board 3.3V voltage regulator, even though this regulator should be able to handle 15V.

 

Frequency Changes

With the standard PICAXE program, the board needs to be re-powered for a change of frequency.

David, VK3HZ, has an alternate version available that does not require a power-down reset to facilitate a frequency change.  This version is ideal when the PLL Board is used as a stand-alone signal source. 

To facilitate the VK3HZ version of code, the GND leg of 47k resistor going to PICAXE pin 3 is lifted from GND, and taken to pin 1 (VDD) instead.

 

The PLL Board developer, Graham, VK3XDK, can be contacted at: grumss@yahoo.com.au


PCB Overlay

 


PICAXE Programming Interface

When interfacing the PLL Board to a standard AXE027 USB programming lead, refer to the colour-coded diagram below.

 

 

PICAXE components, programming leads, etc are available from MicroZed Computers, the Australian distributor;  http://microzed.com.au/


AXE027 Programming Lead Adapter 

To facilitate a no-solder interface, a 3-way 0.1" right/angle header can be fitted to the PCB.

 

A 3-way header socket to 3.5mm socket adapter lead allows easy connection to the AXE027 lead.