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

A partially tetrahedral-gridded FDTD method has been proposed to solve the time-domain electromagnetic scattering of two or three-dimensional arbitrarily shaped dielectric objects. It successfully employs the conventional FDTD method for most of the regular region but introduces the tetrahedral edge-based 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 efficiency. 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.