A spatial filter-enabled high-resolution subgridding scheme for stable FDTD modeling of multiscale geometries

As many real-life microwave structures include multiple space and time scales, research on stable subgridding schemes is as timely as ever. This paper presents a new approach to this old problem, within the context of the FDTD technique, based on a spatial filtering method that enables dense and coarse grids to be run at the time-step of the coarse grid. A spatial filter, coupled to the FDTD update equations, stabilizes those subgrids that are simulated at time steps above their stability limit. The proposed method is used to implement very high aspect ratio subgrids, maintaining late-time stability over millions of time steps.