cst stripline port

I am simulating a 50 ou stripline in CST.But I cannot get the right result.And there are always some higher modes in wave port.Could you tell me how to set the wave port?

Higher modes are appearing naturaly. You need to select the right mode for your structure (I guess the TEM or QuasiTEM) and run analysis with this mode only: under Simulation Settings - mode X
You can post your structure here (without results)
rgz
eirp

I directly set the wave port on the edge face.And the first mode is the parallel plate mode.How should I set the wave port in order to make the first mode is the TEM mode for stripline not the parallel plate? The example is below.
Additionally,the field in coplanar waveguide or coupling microstrips is the superposition of even mode and odd mode. And the first three modes in wave port is ground mode , odd mode and even mode. Which of three Should I choose?
Could you tell me how to set the wave port for stripline,coplanar waveguide,conductor backed coplanar waveguide,coupling microstrip,slotline?
Thanks a lot!

Of course post you structure here, I think your port is too small for calculation try to increase your port dimesions.