Frequency selective surfaces comprised of periodic arrays of two-turn square spiral shaped conductors

The scattering of electromagnetic waves from a frequency selective surfaces (FSSs) composed of a new two-turn square spiral shaped periodic structures are investigated by using modal expansion method. The moment method of Galerkin type is employed by expressing the current induced on the metallic surfaces in terms of Piecewise Sinusoidal (PWS) basis functions to determine the FSS structure reflection and transmission coefficients.