HFSS: phase of S parameters in FSS simulations

Hi,

I'm trying to simulate an FSS in HFSS using master/slave boundary conditions on sides of the unit cell box and PML on top and bottom. my incident field is a plane wave source.
I get the magnitude of S parameters using the "reference for FSS" on PMLs but phase is zero.
I know that I can use for instance Floquet ports but I need all the modes in my simulations so I have only the choice of plane waves as the excitation.
Can any one please tell me how to calculate the phase?



Thank you
Kami