Far-field orthogonality of volume-based characteristic modes for real materials

摘要

Two different solutions for the characteristic modes (CMs) of lossy structures were previously developed using induced volume currents. The first solution diagonalizes the scattering and perturbation matrices, guaranteeing far-field orthogonality at the cost of imaginary eigenvalues and eigencurrents. The second solution does not perfectly diagonalize these matrices, but maintains real-valued eigenvalues and eigencurrents. When these matrices are non-perfectly diagonalized the characteristic far-fields are no longer fully orthogonal to one another. However, the second formulation has not yet been investigated, and as such the effect of non-perfect diagonalization on the orthogonality of the far-field patterns is still unknown. For this reason, it is not clear if volume-based characteristic modes can be used for CM analysis (CMA) of lossy dielectric structures. This article evaluates the effect of different losses on the modal orthogonality of two dielectric resonant structures, and determines the practicality of using volume-based CMA.