Optimal choice of the E.M. expansion for arbitrary shaped aperture/patch FSSs in planar phased arrays

In this paper, we present the analysis of frequency selective surfaces (FSS), which comprise periodic arrays of patches or apertures in conducting screens, by means of the multimode equivalent network (MEN) approach. The unknown quantities are expanded in terms of piecewise sinusoidal/linear expanding functions or in terms of full domain basis functions. The latter correspond to the eigenmodes of a waveguide with the same cross section of the FSS patch/aperture. These eigenmodes are derived using BCMM (boundary contour mode matching).