Estimation of Reflection Coefficients for an Open-Ended Coaxial Waveguide Radiating Into a Chiral Half-Space

Abstract

A spectral-domain moment method solution is presented for estimation of the reflection coefficients of an open-ended coaxial waveguide radiating into a chiral half-space. The electromagnetic fields in the waveguide region are expanded in the normal waveguide modes, while those in the half-space are formulated in terms of plane wave spectrum using two dimensional Fourier transform. A spectral domain admittance matrix is derived through which an electric field integral equation can be obtained by matching the tangential field components on the open end interface. This integral equation is solved with the Galerkin method. The coefficients of the matrix equation are reduced to one-dimensional integrals to facilitate numerical calculation. The problem is different from the case of isotropic non-chiral medium in that chirality causes excitation of TE modes, whose effect is accounted for rigorously in the formulation. This is in contrast to plane wave reflected from a chiral media at normal incidence, where no depolarization effect can be observed. Numerical results are presented to illustrate the idea that the reflectivity of TEM mode carries information on the presence of chirality. The analysis has a potential application in developing an open-ended waveguide method for the characterization of chiral materials using only reflection measurements including depolarization effects.