Hi PlanarMetamaterials , I am using HFSS , I can not use floquet port becouse there is a problem for the S11 , the problem is : if you add a substrate on the cell and you want measure the S11 at the surface of substrate HFSS show you strange results of S11 , I calculated the S11 with matlab using the trasmission line model and there are some big differences , so I wanted to try other ways to calculate the S11 , I solved the problem using a wave port and putting Perfect E along the X walls and Perfect H along the Y walls , I obtain the same results as floquet. Thx for your quickly answer