A hybrid mode-matching finite-elements approach to the analysis of thick dichroic screens with arbitrarily shaped apertures

A hybrid mode-matching (MM) finite-elements (FE) technique for the rigorous analysis of thick-screen inductive frequency selective surfaces (FSSs) is presented. The proposed hybrid approach combines the computational efficiency of the MM analysis with the versatility and flexibility of the FE method, enabling us to accurately model the electromagnetic behavior of inductive dichroic screens. These latter are realized by periodically perforating thick metallic screens with arbitrarily shaped apertures. The electromagnetic fields in the free-space region are expanded through a complete set of Floquet modes allowing us to reduce the analysis to the single periodicity cell; a set of waveguide modes is used inside the openings, each mode is numerically determined through an FE method procedure that relies on edge elements. A spectral criterion to determine the correct ratio between the number of waveguide and Floquet modes is adopted. Samples of numerical results are shown in order to check both the effectiveness and the accuracy of the proposed procedure.