Setting of TEM mode for a waveguide port in CST MWS

HI,
I am using a waveguide port to excite my structure in CST. I keep the no. of modes =1 which it by default takes as TM mode. But I want to have TEM mode. How is it to be done ?
Thanks

In my knowledge, TE mode with the angle of incident wave =0, that is TEM mode.

Hi Mona7150,
You will define the modes number, e.g how many modes are simulated, but what will define the propagating mode (TE, TM or TEM) will be your geometric structure. If your structure is a hollow waveguide, you will not see TEM modes, because the boundary conditions do not allow. Otherwise, if your structure is a coaxial waveguide or a two or more wire structure, then TEM mode will be the first propagating mode. In CST Help you can see some examples could be useful.
Best regards.

Thank you tiagojk11