the boundary condition of microstrip line in CST?

hi,friends

can someone tell me how to deal the boundary condition of a regular
microstrip line in CST?

best regards!

You have first to add some air above the microstrip line with the "backround
material" tool and then set the boundary conditions to electric. It would be
better not to put symmetry planes because you have a quasi-TEM wave, else you may take incorrect results..Good luck!

vtrs,thanks for your help!
As i know,the default background material in cst is just air,then whether i need add another air layer?

hi,
yes you do need to put air because otherwise your PEC boundary above the microstrip line would be in touch with it, shortcircuiting it. I am not sure but probably CST would give an error message, or at least a warning message.
regards

I agree with the replies, and would just like to add something:
You can follow the CST examples and implement their setup in your model (look for "radial stub microstrip").
Good luck,
P.

Dch316 is right,CST will not probably give an error message, but if you do not
put air above te microstrip line your structure will automatically become a planar waveguide..You must do the same thing if your ground plane is interrupted (i.e holes etched in ground,EBG stucture).In that case you must also be carefull while setting the waneguide ports