Analysis of Frequency Selective Surfaces on Periodic Substrates Using Entire Domain Basis Functions

The paper presents an efficient procedure to utilize the existing method of moments/boundary integral-resonant mode expansion approach for the analysis of frequency selective surfaces printed on periodic and inhomogeneous substrates. The Green´s function matrix of the structure is obtained using a multiconductor transmission line model. The resulting series equations are solved by using the periodic method of moments with entire domain functions as both basis and test functions. The required entire domain functions are extracted using boundary integral-resonant mode expansion. The Fourier coefficients of the basis functions are evaluated from the coupling integrals by applying a coordinate transformation. Some examples are analyzed and compared to measurement data. To illustrate the excellent convergence of the method, a comparison between using entire domain and sub-domain functions is made. It is shown that by using the proposed approach not only the number of required basis functions reduces but also lower truncation orders in the Fourier expansions need to be considered. This leads to a drastic reduction of the computation time.