On the Analysis of Frequency-Selective Surfaces Using Subdomain Basis Functions

The problem of scattering from frequency-selective surfaces (FSS) has been investigated by expanding the unknown current distribution with three different sets of basis functions, namely, the roof top, the surface patch, and the triangular patches. The boundary condition on the total electric field on the FSS due to this current distribution is tested either by a line integral or by the Galerkin procedure. This results in an operator equation that can be solved either by a direct matrix inversion method or by an interative procedure, viz., the conjugate gradient method (CGM). The performance of each of these basis and testing functions is evaluated. It is found that the rooftop and the surface patch basis functions in conjunction with the Galerkin testing are superior in computational efficiency as compared to other combinations of basis and testing functions that have been studied in this paper. Comparison of the CPU times on a Cray X-MP/48 supercomputer in solving the operator equation by the direct matrix inversion method and the CGM is provided. Frequency responses of freestanding, periodic arrays of conducting and resistive plates are also presented. © 1990 IEEE