Isotropic Spatial Filters for Suppression of Spurious Noise Waves in Sub-Gridded FDTD Simulation

A class of isotropic spatial filters is proposed to suppress spurious noise waves due to sub-gridding in finite difference time domain simulations. The proposed filters are suitable for both two-dimensional and three-dimensional applications. A simple procedure is introduced for the a-priori determination of the required filter order and the frequency with which the filter is applied based on the maximum temporal frequency bandwidth of the electromagnetic source. The proposed filters are easy to implement in the context of the standard Yee algorithm and are applicable for computational domains that involve quite arbitrary material and structural inhomogeneities.