How to simulate a CPW in HFSS, How to add a excitation

How to simulate a CPW without metal plan in the beneath of the substrate in HFSS?
How to add a excitation?

Thanks.

You can add excitation as waveguide or lumped port, but the HFSS automatically sets the background material as PEC and as I know this material can't be changed. I know only one way: set the radiation port on the plain that must be a non-PEC.

Best regards,
Kit-the-great

you can add space by 1/4 wavelength to the below boundaries of the substrate and then set the boundaries to PEC. Wave port is ususlly used as excitation for CPW.

The end of CPW, including strip and ground on both side, how to set the port in the strip and exclude the ground?