Full wave solution of dielectric loaded waveguides and shielded microstrips utilizing finite difference and the conjugate gradient method

Dynamic analysis of waveguide structures containing dielectric and metal strips is presented. The analysis utilizes a finite difference frequency domain procedure to reduce the problem to a symmetric matrix eigenvalue problem. Since the matrix is also sparse, the eigenvalue problem can be solved quickly and efficiently using the conjugate gradient method resulting in considerable savings in computer storage and time. Comparison is made with the analytical solution for the loaded dielectric waveguide case. For the microstrip case, we get both waveguide modes and quasi‐TEM modes. The quasi‐TEM modes in the limit of zero frequency are checked with the static analysis which also uses finite difference. Some of the quasi‐TEM modes are spurious. This article describes their origin and discusses how to eliminate them. Numerical results are presented to illustrate the principles.