Absorption/Reflection Simulation in HFSS

I am modeling a periodic structure with a floquet port in HFSS. I have a tall rectangular box whose top face is a floquet port and bottom is PEC. a unit cell of teh peridodic structure is within the box. I have master and slave moundaries on the side walls.

I would like to simulate a scattered field pattern. S11 at the floquet port seems to collect all energy scatted in all directions. Thus S11 can be used to determine how much power was absorbed by the structure. However, it does not give how much energy was reflected back monostatically. I plotted a radiation pattern. It appears to be a scatter field caused by the structure, shape-wise... but i don't know how the field strength in the pattern is related to the incident field.

I would appreciate it if anybody could advise me on how to simulate a scattered field that includes diffused electromagnetic waves.

Thanks!