A hybrid MoM solution of scattering from finite arrays of cylindrical cavities in a ground plane

In this paper, we propose a novel hybrid space/spectral-domain method-of-moments (MoM) calculation of canonical planewave scattering from finite periodic structures comprised of dissimilar cylindrical cavities in an infinite ground plane, covered by a dielectric superstrate. We take full advantage of analyzing this particular type of problem (comprised of a canonical geometry) by employing a set of entire-domain basis functions (waveguide modes), which truly span the Hilbert space in which the desired solution resides. The convergence behavior of a solution using said functions is quite robust. Results show that typically only a few basis functions are required to adequately represent the aperture fields with fidelity. We have also reformulated the conventional magnetic field integral equation in a hybrid fashion, whereby the exterior (unbounded half space) MoM interaction terms have been cast in the spectral domain and the interior (cavity) interactions cast in the space domain directly. The spectral representation allows us to trivially include a superstrate layer in the geometry and additionally leads to an efficient evaluation of the interaction integrals due to an overall reduction in the spatial dimensionality. The interior interactions are readily handled in the space domain, where we take advantage of the orthogonality property of waveguide modes. Most importantly, the technique is significantly more accurate than purely numerical methods, i.e., those in which a discretization of the geometry is necessary.