Analysis of Waveguide Components and Inductive Frequency-Selective Surfaces by Using a Hybrid Mode Matching-Finite Element Technique with Edge Elements

A hybrid mode matching (MM)–finite element (FE) technique is presented, with application to the analysis of waveguide components and inductive frequency selective surfaces (FSSs). The proposed hybrid approach combines the computational efficiency of the MM analysis with the versatility and flexibility of the FE method. One of the key features of the present formulation is the expansion of transverse electric and magnetic fields by using tangential vector edge elements (TVEEs), which guarantee spurious-free solutions; indeed, this property is very important for an accurate numerical determination of the modal eigenvalues. FSSs, realized by periodically perforating thick metallic screens with arbitrarily shaped apertures, are analyzed by expanding the electromagnetic fields in the free-space region through a complete set of Floquet modes that allows us to reduce the analysis to the single periodicity cell; modes inside apertures are determined through a FEM procedure. A spectral criterion to determine the correct ratio between the number of FEM-reconstructed and analytically derived modes is adopted. Samples of numerical results are shown in order to check both the effectiveness and the accuracy of the proposed procedure.