On the analysis of capacitive rectangular waveguide discontinuities close to arbitrarily shaped conducting and dielectric posts

Abstract In this work, we propose an integral equation technique for the efficient analysis of capacitive step discontinuities in rectangular waveguides. The method allows for the inclusion of a number of arbitrarily shaped posts in the vicinity of the step discontinuity. The posts can be both metallic or composed of homogeneous dielectric materials. The integral equation formulation is based on the Surface Equivalence Principle, and uses the parallel plate Green’s functions that take into account for the boundary conditions imposed by the host waveguide. The formulation is written in the mixed spatial-spectral frequency domain, and takes advantage of the symmetry of the problem by reducing the original three dimensional (3D) problem to a so called 2.5D problem. The numerical technique has been validated with simulation examples, namely, two lowpass filters that use conducting and dielectric posts of different shapes as impedance inverters. The results provided by the method that we propose have been also compared to those obtained with a commercial full-wave software tool (ANSYS HFSS), showing in all cases a very good agreement with substantially higher computational efficiency.