Spectrum analyzer Part IX High Voltage Supply

The workhorses of the spectrum analyzer the phase locked oscillators (PLO) need a control voltage greater than 20V. Scotty's controller pcb already has a switching converter section, but there were some problems  reported on the newsgroup. So Sam Wetterlin designed a new stand alone module for this purpose. It is a switching style design, but creates very little oscillator ripple at its input and output, and little radiation, though it still should be encased with a fence. 

Since I was lucky and got my hand on a pcb set which included also some Wetterlin pcbs I decided to use his design on my analyzer build.#

Soldering the module was pretty much easy and the module worked immeadetly.

#s

Sam Wetterlin's HV module

Links
HV Module Schema File
Pcb files
Sam Wetterlin Webpage


Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector
Spectrum analyzer Part III ADC 16
Spectrum analyzer Part IV Logarithmic Detector
Spectrum analyzer Part V Master Oscillator
Spectrum analyzer Part VI DDS 
Spectrum analyzer Part VII The Frame
Spectrum analyzer Part VIII The Mixer Modules 

Spectrum analyzer Part VIII The Mixer Modules

Friday morning the perfect time for a new Spectrum Analyzer build entry.

This time the four mixer modules are finished.
There is unfortunately not much to tell, except since one of them (Mixer 1)  is directly coupled to the input stage, shielding is important.

Mixer 1 is responsible for the input.
Mixer 2 is placed directly behind the cavity filter.
Mixer 3 is responsible for the tracking generator output.
Mixer 4 is needed for the Vna functionality.

Since I am building the full blown analyzer, I had to build all four of them.

Mixer 1 to 4 with brass shielding and matching lids

Links:
Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector
Spectrum analyzer Part III ADC 16
Spectrum analyzer Part IV Logarithmic Detector 
Spectrum analyzer Part V Master Oscillator
Spectrum analyzer Part VI DDS 
Spectrum analyzer Part VII The Frame

Spectrum analyzer Part VII The Frame

To be able to test the modules and later insert them in a proper case they have to be secured somehow.
Scotty suggested a double sided raw pcb and to cut holes into it where the future modules will be placed.

Since I did not have such a pcb in my stock but was fortunate enough to find some brass profiles I used these to build my frame.

I cut them to size using the following template on Scotty's website and hardsoldered them.
Unfortunately  they get pretty messed up during the soldering process.
To clean them up you have to bath them in a 40% sulfuric acid solution and wipe them clean afterwards using a polishing cloth.
The last step is to drill mounting holes into the frame's edges.

Frame after soldering

Frame after cleaning

 Links:
Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector
Spectrum analyzer Part III ADC 16
Spectrum analyzer Part IV Logarithmic Detector  
Spectrum analyzer Part V Master Oscillator
Spectrum analyzer Part VI DDS 

Spectrum analyzer Part VI DDS Module(s)

Description (copied from Scotty's web page)

The DDS module is designed and configured with a filter and squaring circuit in the DDS A path.  The filter shown is a 10.7 MHz crystal filter with a 15 KHz bandwidth.  
The squaring circuit of U3 will output a CMOS level, capable of driving a 50 ohm line (J4).  
J3 output is an unfiltered output of the DDS B and will contain all harmonics and aliases of a normal DDS output.  Its output power level is approximately -8 dBm.
For best results, the Clock Input at J1 should be a 5 volt peak to peak square wave, but it will operate at a much lower input.  R3 determines the input impedance of the module.  The input clock frequency must be between 1 MHz and 125 MHz, although the AD9850 is somewhat underrated.

Build process

Soldering the dds chip is somewaht tricky, good magnifying glasses are a must.
Since the DDS chips are serially programmed, I use a different pcb (which I got in a group buy) with only 5 inputs.I think it was routed by Sam Wetterlin but I am not sure.
Studying the schema carefully is highly advisable since there is always a chance that components are placed in a different location.
Because I am building the complete" analyzer, I had to solder two of this modules, the second one is used in the tracking generator.

One of the coming blog posts will be about testing the DDS module and how to shield a Slim module properly.

DDS module rev D with serial input only

 Links:
Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector
Spectrum analyzer Part III ADC 16
Spectrum analyzer Part IV Logarithmic Detector
Spectrum analyzer Part V Master Oscillator

DDS Module

Spectrum analyzer Part V Master Oszillator

Description (copied from Scotty's web page)

The Master Oscillator, contains a 64 MHz oscillator and 3 buffered line drivers.
Each output is 5 volt CMOS that can drive a 50 ohm line that is terminated with either, a high impedance load, or 50 ohms.  A 33 ohm resistor is shown as a series element in each output.
The frequency will drift with temperature. I was able to test only one sample. It had a positive frequency/temperature coefficient of .15 parts per million per degree F (9.6 Hz / 1 deg F)

The build was fairly easy you just have to take care of possible cold solder joints around the crystal oscillator. This kind of packaging easily produces cold solder joints.

Since the unit is already tested I already shielded it.

Master Oscillator rev B

MO back side

Side view of shielded oscillator

 Links:
Spectrum analyzer Part I Controller board Spectrum analyzer Part II Phase Detector   Spectrum analyzer Part III ADC 16 
Spectrum analyzer Part IV Logarithmic Detector 

Master Oscillator 

Spectrum analyzer Part IV Logarithmic Detector

Description (copied from Scotty's web page)

The 8306 Log Detector Module has a dual function.  It is used as a detector to convert RF power to DC voltage (RSSI).  And, it is used as a high gain, RF limited amplifier.
The module has an input impedance of 50 ohms (J1) and a bandwidth of  3 MHz to 160 MHz.  
The RSSI dynamic range is -90 dBm to +10 dBm, with a DC output of +0.4 volts to +2.4 volts, on J2, "MAGVOLTS".  The Limited I.F. Output (J3) is a 50 ohm source with 50 mv peak to peak output.  
The limiter input dynamic range is from -77 dBm to +10 dBm.

Log Detector Rev 0

Build process

So far the Log Detector was one of the easiest modules to solder.

The only problem was to get hold of T1 but fortunately Coilcraft was kind enough to send me two pieces.

Once the module is thoroughly tested and confirmed working it is very important to shield this kind of units properly. 

 Links:
Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector  
Spectrum analyzer Part III ADC 16

Log Detector Module
 

Spectrum analyzer Part III ADC 16

There are two Slim modules for the ADC section.
Their main difference is resolution one delivers 16 bit the other module 12 bit.
Although the 12 bit version is cheaper and has a way easier to solder footprint, I choose the 16 bit version.
 
 Description

The ADC-16 is a dual 16 bit, serial, analog to digital converter, using two AD7685's.  
There is no manual adjustment to set the A to D range.  It is not needed to obtain excellent resolution in the MSA and VNA systems.  Each ADC will digitize its input of 0 to 5 volts to a bit value of 0 to  65535 bits.  This equates to 76.3 uv per bit.
Both A/D's will capture, and clock out their data simultaneously. 

ADC 16 rev A

Spectrum analyzer Part II Phase Detector Module

The  Phase Detector Module is a 360 degree, Phase to Voltage Converter.  It is specifically designed to operate at 10.7 MHz, but will operate in the KHz range up to 30 MHz.  
 The J1 and J2 inputs can be sine or square wave .  The min / max sine input is -20 dBm to +18 dBm.  The min / max square input is 10 mvpp to 5vpp.  Input impedance is nominally 50 ohms, but can be changed to any input impedance.
The output, at J3, is a DC voltage that is proportional to the differential phase of the input signals at J1 and J2.  The 0v to +5v output should be loaded with 100 K or higher.  A realistic phase range is from 20 degrees to 340 degrees with error less than .1 degrees.
Power requirement for the is +7 volts to +15 volts at 50 ma.

To build the RevC module I had to made some component changes and add some capacitors.
The most visible change is the added jumper wire in the bottom right.
It is not easy to solder a jumper to an ic with such a small footprint, but it is manageable as long as you have a good magnifying glass as guidance.

Phase Detector rev C

Links:
Spectrum analyzer Part I Controller board build notes

Phase Detector Slim Module

Spectrum Analyzer Build

Two weeks ago I started to build a 0-3 Ghz Spectrum Analyser based on Scotty's design.

For more information you can visit his build page.


I first started with the rev. c controller module.

From left to right: Usb2Lpt Gender changer Controller board rev C

Since the controller uses an parallel board which modern computers dont't have anymore, I used an Usb2Lpt adapter to talk to the board.
Unfortunately the controller and the adapter are routed for a female plug , so their pins are mirrored.
I could easily fix that problem by soldering a quick and dirty gender changer (the board in the middle).

First tests showed the board is working.

Links:
Controller Page
Usb2Lpt



The next step to a spectrum analyser is the  phase detector module.