Can't get correct filter Response?

[odyseus]

Hi all,
I've been playing around with HFSS and thought I'd try and model a VHF Comm Band pass filter that was described in an article 2008-Q1

I've attached the HFSS (V11) file but although it seems to give the correct filter shape there is massive insertion loss and return loss is 0db??

What have I done wrong? - It's driving me nuts trying to solve this??

All the best

Ody

 

[erno]

Hi Odyseus,

I had a look at your design and made some corrections/changes to model:
1) Resonators coupled still capacitively but from the side, not from the top.
2) Tuning screws added to design.
3) Capacitive coupling between resonators changed to inductive (to lower end).
4) Tuning between resonators can be changed by adjusting the aperture dimensions or by changing the coupling screw length.

Also the input/output couplings from the ports could be made inductive and thus get easier tunable filter, but I did not try that.

Anyway now you can play with the model and adjust the bandwidth/center frequency according to your needs. You could also change the E boundary to have finite conductivity and get thus more realistic loss. I used copper in all metal parts in the model.

I hope you can get your filter working now. My model is for HFSS 12 version.

Best regards

Erno

 

[odyseus]

Hi Erno!
Thanks for taking the time to reply! I'm in Tenerife at the moment but will have a good look on my return. The filter simulation was purely for education but would make a good topic for a hfss tutorial?
All the best
Ody