MODELING GOOD CONDUCTORS USING THE FINITE-DIFFERENCE, TIME-DOMAIN TECHNIQUE

Finite-difference, time-domain (FDTD) is based upon the assumption that field behavior between sample points (i.e., cell nodes) is linear; for propagation in lossless or low-loss materials, the assumption of Linearity will be valid as long as the number of cells per wavelength is kept above some minimum value. For good conductors, where the wavelength decreases many orders of magnitude from its free-space size, and the fields are decaying exponentially, it becomes impractical to shrink the cell size so as to maintain linearity between cells. When the number of cells per wavelength criterion is, violated at a boundary, FDTD will not yield correct estimates of reflection from, or transmission into, that boundary. The work presented here details and provides validation for two approaches that can be used to achieve realistic results when modeling good conductors with FDTD using practical cell sizes, These approaches do not require modifications to the FDTD algorithms, and do not affect program execution times. Achieving,accurate loss estimates will be of particular interest to those modeling resonant structures using FDTD.