I was trying to simulate a conformal FSS as given in Figure 5 of the document attached. Here, I would like to assign periodic boundary conditions in one direction so that the conformal row repeats itself. However, when I tried this in CST Studio Suite (Assigned 'periodic' in Ymax,Ymin and 'open(add space)' in Xmax, Xmin, Zmin, Zmax and applied wave guide port in z direction), the following error message was displayed:

"Mesh for port1 is periodic,periodic ports are not supported."  

What is to be done in this regard? How to assign periodic boundaries in the case of such kind of conformal structures?