plane wave in cst - help please

I excite my structure by a plane wave in cst. The question is - how to control the phase of the plane wave? I need to put the zero phase in the center of coordinates and that should hold on several frequencies in wide frequency range.
Will be very thankful if someone helps!

I see that nobody is interested, but it is a real problem in CST! In HFSS for example, it is very easy to define the phase, just a simple click in the settings. But in CST there is no such option, amazing! The phase varies arbitrarily for different frequencies. It is no way to calculate polarizability of the structure, because you should definitely know the phase of incident field for this.
If I am wrong, correct me somebody!