Number of waveport modes in HFSS

Hello all,

I am simulating a simple microstrip antenna, and I have used a waveport. The problem is that when I set 2 for the number of modes in the waveport, the s11 will be completely different from the case with just 1 mode set in the waveport. Does any one know the reason?

Thanks.

Welcome mosala52,

The S11 of which mode? You can specify which modes to excite under HFSS -> Fields -> Edit Sources. I can't think of a reason why the S11 of the TEM mode should change.

I tried to specify the number of modes through HFSS -> Fields -> Edit Sources, but it was not possible! There is no option to change the modes. (I work with HFSS 14)
What do you mean by TEM mode?
When we excite the 2 modes in waveport, which modes are exactly excited? The first 2 dominant modes including TEM mode?

Thanks.

You can set the excitation magnitude and phases of the two modes. There are two modes shown in that window, correct?

The microstripline mode.

The TEM will be the first, the second might be a surface wave mode on the upper microstrip line -- I'm not sure, you'd have to check.