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Inconsistent Simulation Results When Narrowing Frequency Range (Electromagnetic Simulation)

Posted 21 mag 2025, 09:56 GMT-4 RF & Microwave Engineering, Results & Visualization Version 6.0 2 Replies

Ricarte Ferreira
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Hello everyone,

I'm currently running an electromagnetic simulation in COMSOL, and I'm encountering an unexpected issue regarding the frequency sweep.

When I simulate over the full frequency range from 0.3 GHz to 3 GHz, the results behave as expected — including the appearance of a resonance peak around 0.685 GHz.

However, when I narrow the frequency range to focus specifically on this peak, for example from 0.68 GHz to 0.71 GHz, the simulation produces different values for S-parameters, and the peak response does not exactly match the one seen in the full-range sweep.

I'm using the same physics settings, mesh, and solver configurations in both cases. Has anyone experienced similar behavior? Could this be related to frequency-dependent boundary conditions, mesh resolution, or solver settings that are sensitive to the sweep range?

Any insights or suggestions would be greatly appreciated!

Best regards, Ricarte Ferreira

2 Replies Last Post 23 mag 2025, 07:40 GMT-4
Robert Koslover Certified Consultant
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Posted: 6 months ago 21 mag 2025, 10:17 GMT-4

Re: "Could this be related to frequency-dependent boundary conditions, mesh resolution, or solver settings that are sensitive to the sweep range?" Maybe. Also, you say "the peak response does not exactly match..." Ok, but how much difference is there? Is the difference negligible or substantial? Are you using "frequency dependent" boundary conditions? Is your model configured to use the same mesh at all frequencies or are you remeshing it as a function of frequency? If thinking through these questions doesn't help you, then I suggest you post your model to the forum.

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Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
Re: "Could this be related to frequency-dependent boundary conditions, mesh resolution, or solver settings that are sensitive to the sweep range?" Maybe. Also, you say "the peak response does not exactly match..." Ok, but how much difference is there? Is the difference negligible or substantial? Are you using "frequency dependent" boundary conditions? Is your model configured to use the same mesh at all frequencies or are you remeshing it as a function of frequency? If thinking through these questions doesn't help you, then I suggest you post your model to the forum.
Acculution ApS Certified Consultant
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Posted: 6 months ago 23 mag 2025, 07:40 GMT-4

I am not quite sure what you are experiencing here, but it is very normal to see for example a higher peak in a resonance, when you narrow in on it, simply due to the frequency resolution being higher. Hopefully, you have the same values at some frequency such as 0.685 GHz for either of the two sweeps?

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René Christensen, PhD
Acculution ApS
www.acculution.com
info@acculution.com
I am not quite sure what you are experiencing here, but it is very normal to see for example a higher peak in a resonance, when you narrow in on it, simply due to the frequency resolution being higher. Hopefully, you have the same values at some frequency such as 0.685 GHz for either of the two sweeps?

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