Simplified Modal Expansion to Analyze Frequency-Selective Surfaces: An Equivalent Circuit Approach

This communication extends a previously reported analytical circuit that models the plane wave scattering by 2-D arrays of planar patches/apertures embedded in a layered media. In this extension, it is assumed that the current/electric field spatial profile in the patch/aperture region can directly be taken from the eigenfields of a waveguide whose cross section matches the scatterer boundaries. This methodology exploits all the advantages of the circuit modeling and gives place to a very efficient computational tool for many practical frequency-selective surfaces (FSSs). The circuit model is expected to work up to frequencies where the isolated scatterers have their third resonance. Thus, it allows us to provide unified equivalent circuits to deal with conical incidence and with certain symmetric cases involving two or three patches/apertures in the unit cell.