calculating S11 in CST MWS

Hi,
I have a multilayered problem to solve. But to start with I want to calculate the S11 for a simple air-water interface(whose S11 I can calculate easily). I want to have finite dimension along one axis and infinite along the other two. I tried implementing it but I am not getting the correct result. Please tell me how to approach.
Thanks

Hi
if your structure is Optical ,please download below tutorials from CST , it might be help.
https://www.google.com/url?sa=t&rct=...61535280,d.Yms
https://www.google.com/url?sa=t&rct=...61535280,d.Yms

Thank you very much.. do you know about any more optical papers on CST?