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Differential equation methods often are used for the analysis of the waves scattered by a dielectric grating. It is known that accurate numerical solutions can be obtained if the number of expansion terms of the spatial harmonics is increased. However, when the differential equation method is applied to a dielectric grating with an extremely large permittivity, the convergence speed of the solution becomes excessively slow in the TM wave analysis. Because of the increase of the computation time and the memory capacity, an analysis based on the differential equation method becomes difficult in practice. In this paper, it is shown that a boundary element method using Green's function satisfying the periodic condition is effective for the analysis. By introduction of pseudo‐periodic Green's function, the definition region for the integral equation is limited to the grating surface. In comparison to the boundary element method using the Hankel function, the number of linear equations is reduced. By means of numerical examples, it is shown that the convergence speed of the solution by the present method is faster and the computation time is significantly shorter than the solution by the differential equation method even in the TM wave analysis of a dielectric grating with a large loss.

of FSSs made of a square patch. cross dipole, and circular loop with a circularly polarized incidence.Key words: Frequency-selective screen: electromagnetic wave scattering; infinite periodic array: circularly polarized incidence: moment method.In this paper. an FSS placed on a dielectric lens is considered, and the problem of scattering by an infinitely periohc array on a semiinfinite dielectric substrate is analyzed by the spectral domain moment method. The representation ofthe cUrreiit distribution used in the analysis by the induced emf method for a curved antenna by Amano et al. [6] isapplied,so that thecurrent onanarbitrarilyshaped conductor is expressed as a superposition of the piecewise sinusoidal (PWS) functions.