Scattering from frequency selective surfaces: a continuity condition for entire domain basis functions and an improved set of basis functions for crossed dipoles

A plane wave impinges on an infinite, plane frequency selective surface (FSS) composed of crossed dipoles, and a surface current is induced on the conducting parts of the FSS. Using the established spectral Galerkin method, where the method of moment (MoM) procedure is carried out in the spectral domain, the induced current is determined, and the scattering problem is solved. The authors derive a necessary continuity condition of entire domain basis functions, and show that basis functions which do not satisfy this condition are suppressed by the spectral Galerkin method. Specifically, an improved set of basis functions are presented, designed for crossed dipoles. This set of basis functions consists of traditional even (symmetric) dipole basis functions, and a new set of V-dipole basis functions. It is found that the present basis functions are considerably more efficient than the existing basis functions for crossed dipoles. It is found that it suffices to take four of the present basis functions into account, still getting highly accurate results, even above the first resonance frequency