HFSS - solution/mesh frequency for bandpass filter

[elektr0]

Hi,
what is the best solution/mesh frequency for bandpass filters.
I get different results, wenn using 90 GHz (center frequency) or 120 GHz (far above center frequency) for mesh generation (solution setup). Which result should I trust ?

-e

 

[PlanarMetamaterials]

Hi elektr0,

Depending on your setup, you will be exciting a number of modes -- at a higher frequency such as 90GHz, it is likely that a number of different modes exist between 90 and 120 GHz.

The adaptive meshing process will mesh for whatever modes are present. For this reason, you probably want to mesh right at your resonant frequency (90 GHz), to ensure the right mode is being meshed.

However, for this same reason, the higher frequency data may be incorrect.

 

[elektr0]

Dear PlanarMetamaterials,
thank you for your help. My setup does only allow for one mode up to the maximum frequency of the simulation.
We have experienced this many times with bandpass filters. Only with mesh/solution frequency inside the passband, it gives correct results.
BUT: What if you dont know the structure you are simulating. I would simply believe what HFSS gives first. It would be required to readjust the
mesh frequency to a certain passband (if applicable). This is a problem!
-e

 

[PlanarMetamaterials]

BUT: What if you dont know the structure you are simulating.

This is what eigenmode simulations are for -- they give you the frequencies of the supported modes, such that you can tell what is going on.