Treating late-time instability of partially tetrahedral-gridded finite difference time domain method

Abstract

A partially tetrahedral-gridded FDTD method has recently been proposed to solve the time-domain electromagnetic scattering of two or threedimensional arbitrarily shaped dielectric objects [1], [2]. It successfully employs the conventional FDTD method for most of the regular region but introduces (.he tetrahedral edgebaaed finite element scheme to model the region near the arbitrarily curved surfaces. Numerical results of early time simulation validate that the method has the advantages of accuracy, flexibility, stability, and computational effiriency. For the analyses of electromagnetic problems of high Q systems, transient response over a very long duration is necessary. It is found that the simulation may suffer from late-time instability and spurious dc modes. This paper is focused on treating the two drawbacks of the hybrid method. A. Temporal Filtering Technique for Late Time instabilityThe strategy employed here is to derive a low pass filter to suppress the computational error which is of higher frcquencies, while keeping the low frequency components nearly unchanged. The filter corresponds to an IIR system defined by