Spectral-Domain Method of Moments for the Modal Analysis of Line Waveguides

A rigorous full-wave modal analysis based on the method of moments (MoM) in the spectral domain is presented for line waveguides constituted by two-part impedance planes with arbitrary anisotropic surface impedances. An integral equation is formulated by introducing an auxiliary current sheet on one of the two half-planes and extending the impedance boundary condition of the complementary half-plane to hold on the entire plane. The equation is then discretized with the MoM in the spectral domain, by employing exponentially weighted Laguerre polynomials as entire-domain basis functions and performing a Galerkin testing. Numerical results for both bound and leaky line waves are presented and validated against independent results, obtained for isotropic surface impedances with the analytical Sommerfeld-Maliuzhinets method and for the general anisotropic case with a commercial electromagnetic simulator. The proposed approach is computationally efficient, can accommodate the presence of spatial dispersion, and offers physical insight into the modal propagation regimes.