Abstract: In this paper the scattering characteristics of a plane wave incident on a thin perfectly conducting screen perforated periodically with apertures are analysed by the method of moments. The concept of generalized waveguide is introduced, and each element of this kind of frequency selective surface (FSS) can be taken as a junction between two generalized waveguides. The eigen modes in these waveguides are replaced by Floquet modes in periodic structures. An equivalece theorem and the method of moments are employed to obtain the generalized scattering matrix of the junction. As an example, the scattering from a conducting screen perforated periodically with rectangular, circular and equilateral triangular apertures are computed, respectively. Numerical results show good agreement with those published in available literature.

Key words: electromagnetic scattering, frequency selective surfaces（FSS）, the method of moments