How to setup a right CPW with bottom ground model in HFSS

Could somebody help me to analysis the attached model? I simulated it, but the result seems not ritht. S21 is near-150dB. I am not sure if the Port size is ok, or the model itself is ok?

Hi hqu_yuncs,

There are two things you need to change:

1. There is no airbox around your structure. Define an airbox and define the lower face as perfect_E and other as radiation boundary. The hight of the box should be at least quarter wavelength of lowest frequency. Since your lower frequency is 1 GHz you need very high airbox. You can consider using different frequency range. (I used an arbitrary size of airbox, please change it according to your range)

2. Your waveport should start from z=-0.7 and the integration line was not correct. It should be from middle trace to right or left top ground. If you take a look at the my attached file you know what I mean.

I've simulated the design and it is fine I guess.

regards,
Shameem