Stable FDTD solutions with higher-order absorbing boundary conditions

One-way wave equation type boundary operators can produce instabilities in finite-difference-time-domain (FDTD) simulations. Such instabilities become acute when the order of the operator is three or higher. Previous efforts to stabilize these operators sacrificed either efficiency or accuracy. This Letter presents a simple scheme that produces stable FDTD solutions by using double-precision arithmetic over a fraction of the domain while using damping coefficients that are small enough to maintain accuracy, especially over the lower frequencies. This procedure gives accurate solutions while only marginally increasing the memory overhead. (C) 1997 John Wiley & Sons, Inc.