Analysis of multilayer frequency selective surfaces with rectangular geometries

Multilayered frequency selective surfaces (FSS) are analysed in a flexible way by cascading the generalized scattering matrices (GSM) of each interface with periodic metallizations. Usually, the scattering parameters of each interface are computed independently for each incident space harmonic, and only a small number of these can be handled for the cascade process. This is not a limitation when thick substrates are used. but for thin dielectric layers a prohibitive number of harmonics must be used to obtain accurate results. In the present paper, an efficient and rigorous mode matching (MM) technique has been implemented for the analysis of multilayered rectangular FSS, that allows to use a high number of space harmonics in the cascade. The elementary structure considered as a building block, is a metallic screen with periodic rectangular apertures (inductive screen) or an array of rectangular patches (the complementary capacitive screen), placed on the interface between two different dielectrics. First, the whole GSM of a single screen, with a high number of space harmonics (several hundreds), is computed directly, assuming multiple harmonic incidence. Then, the GSMs are cascaded iteratively to analyse the multilayer structure. Numerical results are presented to show the importance of higher order space harmonics