Large Overlapping Subdomain Method of Moments for the Analysis of Frequency Selective Surfaces

A new set of basis functions is presented for the analysis of frequency selective surfaces (FSSs) by the method of moments (MoM). Each of the separate patches in the unit cell of an FSS is covered with some large overlapping sub-patches. Each sub-patch has a shape that is simple enough for obtaining an appropriate set of basis functions analytically from an eigenvalue problem. This technique is called the large overlapping subdomain MoM. It is shown that the proposed method has a better convergence than the standard MoM with rooftop basis functions in terms of both required basis functions and Fourier modes. Furthermore, this approach offers a much easier way to model patches with curved boundaries. The extraction of the proposed basis functions involves mostly analytical procedures. Therefore, this kind of moment method is computationally more efficient than versions with entire domain basis functions, in which the basis is obtained from the boundary integral resonant mode expansion technique. Nonetheless, this is accompanied by a small decay in the convergence rate, i.e., the large overlapping subdomain is clearly placed between the standard subdomain and entire domain versions of the MoM. It is shown that the developed method is advantageous for usual FSSs and unit cell configurations with several patches.