about microstrip simulation questions using HFSS!

microstrip is open.not close.
so will radiation boundary alse be placed in simulating microstrip problems?
recently. I simulated a modal about microstip-to-NRD. I use radiation boundary
to round the modal, but the value of S21 is not very matched with the ones measured. measured value: -0.8dB simulation result:-2dB
please who can give me some ideas about it? thanks very much!

(1) Using a radiation boundary that is lambda/4 away from the transmission line should be fine. Since you are not simulating an antenna (strong radiator), you may could even use a PEC boundary if its far enough away from the transmission line. Since the signal is propagating down the microstrip line and not into free space, as long as you don't intefere with the fields above the trace it should be fine.

(2) Make sure the copper thickness and finite conductivity are correctly modeled. Also include the dielectric losses of the substrate in the model.

(3) Be sure to use a wave port instead of a lumped port, and make the port convergence criteria more strict.

(4) Renormalize the HFSS predicted S-parameters to 50 Ohms.

Good luck.

I think a PML BC may be more effieient for Microstrip Simulation Problem

hi

i think "defining rad boundary" is not really needed. just add air to your model.
i have tested it. it works.
root of your problem is something else.
maybe your model sizes are not appropriate to the operating frequency.
is the dimensions of your substrate at least 4-lambda?

tell me more about your problems