Is there an amateur test tool project to test a Band Pass Filter?
Instead of buying a network analyzer, is there a hobby project of a tool to measure the S21 parameter?
I think a sweeping generator, RF comparator, A/D converter and a PC software can do the job cheaply. The frequency range is 1-7 Ghz.
Thanks in advance....
For a reasonable test of any device over 1 to 7 GHz, you need a calibrated detector and a sweep generator with an oscilloscope.
First you should use the detector to check the output power from the sweeper, then, you can measure the insertion loss over frequency of e.g. your filter.
If the filter response is flat, usually the S11 and S22 are good, too.
The Vector Network Analyzer can give you the complete filter parameters.
You could contact filter-making companies, some can offer you the filter measurement as a paid service.
I doubt you can do a good test with an amateur equipment.
It depends how accurate you want your measurements to be. You could hire a VNA and this would be the best option for accuracy.
The other end of the scale is to get eval boards for the ADF4350 wideband PLL/VCO synth from Analog devices to do the swept source (maybe add a doubler to get 7GHz?) and maybe an eval board for a HMC602LP4 log detector from Hittite and lash together something using a common MCU/ADC (display data via MCU UART on a PC?) that will provide a scalar measurement. But it won't be very accurate and it won't have the dynamic range to see the full performance of the cavity.
There are amateur VNA's project, just do the search search.
This is for a start:
N2PK
http://www.oz6frs.dk/oz6frsold/2007/...NA_3_Color.pdf
I remember seeing other projects but I can't find the links at the moment.
I have checked the project, it uses a DDS for frequencies up to 60 Mhz.
I wonder if it would work if I use a 2 ghz mixer to shift it to the 2- 2.060 Ghz range?
maybe you should make it clear.
what is your IF if you use mixer?
You should filter the RF after the mixer, if it is possible is determined by whether the filter make sense or not.
I guess, one double input accurate power meter and two directional couplers will serve you as a Scalar Network Analyzer.You may connect one of the directional couplers to input, and other to output and terminate them with 50 Ohm. Then measure the reflected power and delivered power to load and repeat this measurement for reverse path with a cheap signal generator.
So basically you can catch the magnitude of S11,S22 and S21 and S12..
All of them will cost you max. 1-2 KS with used equipments.
But I personally prefer to buy a used but old model VNA that can be found around 5K-7KS
Just do the search, you can use an upconverter. There are amateur projects that will measure in any frequency range. To build suc a VNA is a big project, and I agree with BigBoss that you would be better off buing one. And if it is just one filter that you "must" measure I would just hire a VNA for a day.