Comprehensive Multimode Reflection Analysis of a Dielectric-Loaded Rectangular Waveguide Terminated by Semi-Infinite Dielectric Media

Abstract

This article presents a comprehensive multimode reflection analysis of a dielectric-loaded rectangular waveguide terminated by semiinfinite dielectric media. A Fourier-based analysis approach is extended for different incident modes of the waveguide to calculate the amplitude coefficients of the reflected modes when the flange or the waveguide walls have different finite conductivities. We calculate the complex propagation constant using the method of perturbation of the boundary conditions. The modal scattering parameters are defined based on the voltage wave normalized amplitudes to be valid for both propagating and evanescent fields. The inclusion of coupled and noncoupled modes in the solution is evaluated in terms of calculation time and the accuracy of the results. An algorithm is presented to calculate the reflection coefficient of variations in terms of the coupled modes included in the solution. It is shown that these variations are dependent on the operating frequency and dielectric properties used in the geometry. Our results are compared with 3-D full-wave simulations, and an excellent agreement is achieved over a wide frequency range by using the primary coupled modes in the solution. The modal aperture admittance is calculated for different modes to show the coupled modes’ effect on the results. Also, the proposed algorithm is modified to find the effective coupled modes much faster. These modes are used to obtain accurate results for different dielectric-loaded structures.