What exactly are the S-Parameters in Comsol? In my opinion, the S-Parameters (S11, S21, etc.) are normally defined as S11=reflected field over incident field and S21=transmitted field over incident field.
In Comsol this seems to be different since the S-Parameters depend on the size of the simulation box (ports at top and bottom) filled with vacuum (periodic conditions left and right). Is there a phase in the definition of the S-Parameters?