Electromagnetic scattering of underground object using nonuniform mesh FDTD and PML

In this paper, we present a finite-difference time-domain (FDTD) algorithm for modeling buried objects using very low frequencies, e.g., those in the ELF range. It is shown how long-wavelength electromagnetic signals, guided by the earth-ionosphere waveguide and serving as illuminating sources, are scattered by underground structures, and that that scattered fields may be measured above the earth surface, and subsequently analyzed to yield the lo cation of the underground objects. The problem of large computational domai ns is made manageable via the use of the nonuniform FDTD, and the mesh trun cation aspect is addressed by using the perfectly matched layer (PML) conce pt. (C) 1999 John Wiley & Sons, Inc.