A FREQUENCY-DEPENDENT FINITE-DIFFERENCE TIME-DOMAIN FORMULATION FOR DISPERSIVE MATERIALS

Current finite-difference time-domain (FDTD) formulations require the permittivity, permeability, and conductivity to be independent of frequency. However, for many real materials of interest, these parameters vary significantly with frequency. This variation is included in a frequency-dependent FDTD formulation ((FD)2TD) by extending the traditional formulation to include a discrete time-domain convolution, which is efficiently evaluated using recursion. The accuracy of the extension is demonstrated by computing the reflection coefficient at an air-water interface over a wide frequency band including the effects of the frequency-dependent permittivity of water. Extension to frequency-dependent permeability and to three dimensions is straightforward. The (FD)2TD formulation will allow computation of electromagnetic interaction with virtually any material and geometry (subject only to computer resource limitations) with pulse excitation. Materials that are highly dispersive, such as snow, ice, plasma, and radar-absorbing material, may be considered efficiently by using (FD)2TD. © 1990 IEEE