I have modeled a slab in CST Studio Suite with frequency dependent complex permittivity.When i simulate the slab for lower frequency range(at 20THz), obtain the s parameters and from the post-processing retreive the effective permittivity i get my input data at 20Thz itself(as expected, since there are no inclusions).But when i do the simulation at higher frequencies (at 700Thz) , my retreived permittivity data from post-processing does not match my input data at 700THz. Why does this happen?Does this mean my S-parameters value at 700 THz is also wrong?