Re: 50 ohm termination
Hi, zahriladha.
I think in HFSS, if you are using Driven Modal and Waveport, the HFSS will calculate the intrinsic impedance of your port (not necessary 50 Ohm) and use that as the terminal impedance for your S-parameter.
However, you can renormalize your port impedance to 50 Ohm in the waveport options.
If you are also considering higher-order mode, things become complicated. And you can use Driven Terminal with defining the voltage integration line. Then you will also get 50 Ohm impedance S-parameters.
Hopefully that will help you.