[HFSS]How to set the BC and Excitations of a finite-unit FSS

i don't want use the Master-Slaver BC and Floquet port to solve the problem, which recommended by HFSS hand book.
i have draw a 8*8 (finite-unit) FSS in HFSS 11, and just care about the 4*4 units in the central area. How should i set the boundary condition and Excitation?[/img]