Problem with Resonances in Combline Filter

Hello,

I am designing a 5 pole combline filter. The problem I have been facing is that whenever I simulate a combline filter of order more than 3, the S11 response always shows lesser no of resonances and hence getting the required bandwidth and ripple levels is very hard. I tried to use both peter martin's equations and also the eigen mode analysis method to determine the rod spacing but to no avail. I'm attaching a HFSS file with one such simulation where only 3 resonances are distinct for a 5-pole filter. Please help

Thanks

I can't read your file, but how distinct the VSWR ripples will be depends upon the amplitude response of your design. A Bessel response will only show one dip at centre frequency, but a 1dB Chebyshev will clearly show all 5.

If want a quick design tool then download Ansoft DesignerSV, the filter design wizard is easy to use and gives some good start values. If you have HFSS you probably already have Designer or something similar anyway.

Hello,

I'm attaching the zip file and hope you can see it. The amplitude response I have chosen is chebyshev with 0.1dB ripple. That is the reason why I'm looking for 5 resonances. Thanks for your reply.

I hope you can help me now

Hello

I need help urgently !
Thanks

Try to use the cosimulation method with ansoft designer. export the S parameter into the circuit and tune it in the linear simulator to get correct respond. U