RCS computation with HFSS

Hi group,
a question about computing RCS for a complex object in HFSS'enviroment. I've modeled the object, then assigned material's specifications and computed the back scattered field. I've obtained some results at four high frequencies (GHz). The strange thing is that the Total RCS becomes bigger when the frequency decrease... and also more nervous. The tehoretical relation wants the RCS to increase with the increasing of the freq. (Obviuously, every result is related to the modulus of the RCS).

Comments welcome!
Thanks -alessandra

Wenn your model isn't too big and too complicated, I could simulate it again to confirm the results.

Post your model here!!