Using the PML ABC for Air/Soil Wave Interaction Modeling in the Time and Frequency Domains

Abstract

The Perfectly Matched Layer (PML) and absorbing boundary condition (ABC) is applied to two-dimensional Finite Difference Time Domain (FDTD) and Finite Difference Frequency Domain (FDFD) simulations of wave interactions with a two-layer air and soil geometry. Since the soil medium is lossy and dispersive, modeling of wave propagation and scattering is significantly more difficult than for free space and pure dielectrics. In addition, specifying an ABC which efficiently prevents reflections from both the free space termination and the adjacent soil is challenging. The theoretical basis for terminating dispersive media for both the time and frequency domains is presented, and simulation results for plane wave and point source excitations are demonstrated. For the former case, scattering is computed from a buried mine-like target. Although the absorbing characteristics of the PML for the air/soil interface are not as good as for free space, it is shown that maximum local reflections of as low as −15dB for FDTD and −50dB for FDFD are possible.