Cst microwave problem - Waveguide simulation

Hello all,

I am currently using CST Microwave Studio to simulate my project dealing with waveguide.
The problem is we are simulating the problem in a wide frequency range (2-22GHz). There is a warning "At least one propagating modes at port 1 is not considered in time domain calculation. It might be better to increase the number of modes at port x".

I have tried increasing the number of modes because obviously over that frequency range there is quite number of modes propagating. However that didn't give correct result. I can say that because I have an empirical data that I can compare to.

This has trigerred two questions. (1) What is the meaning of the error and what could be done to solve the it.
(2) Can I simulate wide frequency range with several modes(2-22GHz) in waveguides just by leaving the default settings?

Thanks heaps.

Hi Sharp,

Well, I to faced the similar problem sometime ago..and message will appear like

Increase the number of modes or reduce the upper limit of the frequency,

I tried both the way:

i) If u reduce the frequency limit, say 8 or 10 Ghz, u might get the simulation without error

ii) if u increase the mode numbers say 2 in that particular port, it takes too long to resolve the simulation...and finally it may ended simulation error..

But can try to increase or decrease the size of the port.....I am still trying it..

Any CST Users out there to suggest us the corret way of get rid of this problems...?

Thank you

Hello Isharan,

Thanks for the feedback.

Yea I agree with u that by increasing the number of modes, the simulation does take longer.

I have tried make the port size smaller and the error did go out, but the result still doubtful. Probably I am gonna play a bit more with the boundary conditions, though I'm still not sure what to adjust.

All the best man and hope anyone can recommend other solutions.

wht about your bounday condition?

I am still not sure whether my settings are correct and whether it does influence the result.

I set Et = 0 for all the faces of the waveguide. The background is conductor.

put the backround as normal try thisss........... otherwise u send ur design .......

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