The calculation of dispersion diagrams and field patterns of metallic rectangular waveguides filled with an inhomogeneous dielectric whose permittivity varies continuously along the broad size of the guide is considered. In general, this problem has no exact solution, thus numerical techniques should be used. In this article, the pseudospectral frequency-domain (PSFD) method is proposed to address the problem. Starting from the Helmholtz equation, a matrix eigenvalue problem is obtained by applying the collocation technique with Chebyshev polynomials as basis functions. The results obtained are compared with those calculated by the conventional finite-difference frequency-domain method showing that the PSFD technique provides an excellent accuracy.
