APPLICATION OF THE AWE METHOD WITH THE 3-D TVFEM TO MODEL SPECTRAL RESPONSES OF PASSIVE MICROWAVE COMPONENTS

This paper describes an efficient algorithm to evaluate the spectral r esponse of passive microwave devices. The method is based on the combi nation of the tangential-vector finite-element method (TVFEM) for mode ling three-dimensional (3-D) microwave passive components and the asym ptotic waveform evaluation (AWE) technique for efficiently computing t he spectral responses. Unlike previous AWE approaches, which use direc t matrix factorization to solve for the moments, we employ a precondit ioned conjugate gradient (PCG) method. It is observed that the iterati ve PCG solver converges much faster by solving only the additional com ponents of the higher moments outside the span of previous moments. Mo reover, this paper discusses the effect of shifting the expansion freq uency from the real frequency axis to the lower half of the complex fr equency plane. Through several numerical examples, a waveguide with an obstacle inside, mitered 90 degrees E- and H-plane waveguide bend, mi crostrip low-pass filter, and microstrip patch antenna, we show that s hifting reduces the pollution due to dominant resonant modes and, cons equently, results in a much wider convergence range for the moment-mat ching AWE technique.