Extending the Stability Limit of the FDTD Method With Spatial Filtering

It is shown that the well-known Courant stability limit of the finite-difference time-domain (FDTD) method can be controlled and extended by filtering out unstable spatial harmonics that develop when the time-step is chosen to exceed this limit. The formulation of a spatially filtered FDTD algorithm is accompanied by a numerical benchmarking study that includes cavity resonator and backward wave media simulations.