We are measuring return loss of laminates using GRL calibration technique wherein the Laminate under test is placed at some distance from horn antenna in free space. Based on the return loss obtained, the laminate is characterised to find its permittivity and loss tangent. Is there a way in CST Studio Suite to do this? I tried return loss using permittivity and loss tangent. But, results not matching with measured return loss. Will horn antenna geometry matter a lot? (it is ridged horn antenna)