How to set the direction of E-field in waveguide port [CST]

Hi,
I have a problem to set the direction of E-field in waveguides port [CST].
I can set the direction of incident wave, but I can not specific the direction of E-field (I simulate in transient mode). Could anyone help me to solve this problem, please?
Thank you.

hi
it's depend on your structure, what kind of your structure do you want to simulate ?

I try to simulate metamaterial structure.
Now, I already manage this plobem, it dependent on boundary condition.
E-field has direction as Etan=0 in CST
thanks,