Spectral Numerical Green’s Function Based Eigenanalysis for Cavity Perturbations

Efficient eigenanalyses are proposed for cavities which are geometrically or materially perturbed. The method leverages the spectral representation of the numerical Green’s function (NGF) of the unperturbed cavity system. The convergence of the series formed by resonant solenoidal modes is accelerated by performing an NGF extraction at one low wavenumber. With spectral NGFs, this approach gives rise to small, linear matrix eigenvalue problems without the generation of spurious DC modes.