Debye function expansions of empirical models of complex permittivity for use in FDTD solutions

The method described provides an intuitive and straightforward approach for approximating arbitrary complex permittivities using sums of Debye functions. Because the distribution of relaxation frequencies is guided by the actual frequency range of interest, there is a greater chance that a minimum number of Debye functions will be required in the expansion. This leads to a more efficient FDTD solution, since computer memory requirements decrease as the number of Debye functions decreases.