Microstrip filter design help

hairpin 1296mhz

I am ham radio YO3HCV and currently working on 1296 MHz transverter project .
I try to design some filters on FR-4 material but my knowledge in microstrip’s are so poor … on google I found some nice programs like Sonnet and Parfil but of course, not for free. Does any body know where to find a full version of these, or at least a functional demo ?!?

For example with Sonnet, when I try a hairpin filter, ask me to register…I register but program needs a lot of memory ?!?... and in demo I cannot do nothing but see his nice examples. And with Parfil, I cannot design on FR-4 …lol… the only demo it has…

Can anybody help ?

Best regards,
YO3HCV, Eddy

board layout + 1296mhz

Diel const of FR4 can vary from 4.3-4.8 from batch to batch. And is temperature sensitive as well. Loss Tangent can vary between 0.018-0.030, depending on number of layers, board thickness, etc.

Using FR4 as substrate for microwave filters, requires accurate tolerance analyses of the FR4 parameters in a microwave design program, to predict spread in performance of the finished design. Using e.g. Monte Carlo analysis here can avoid many traps.

There are better and more suitable substrates for 1296 MHz filter designs, for example Rogers RO3000 series. See http://www.rogerscorporation.com/acm/litintbl.htm.

fr4 filter design

Hi Edygo -- You might post your circuit on the Sonnet forum, www.sonnetsoftware.com, people there will help you modify the meshing and circuit so you can analyze your filter. As an example of what can be done, click on help, then Examples, then Filters, then Hairpin. You will see a 6 resonator hairpin filter. Click on "Load into xgeom" and the circuit appears in the layout editor. As I recall, it is centered on about 4 GHz. So if you double all dimensions (including cell size), you should get a filter that is very close to your needs. It requires 3 seconds per frequency to analyze using my notebook computer. Sonnet's defaults are all set for the most accurate analysis. If you need a faster analysis that uses less memory, there are many things that can be done. If you have problems, just ask on the Sonnet forum. There are many skilled users there who can help.