ABSTRACT
Surface impedance boundary conditions are employed to eliminate the internal volume of lossy dielectric objects from scattering calculations. In applications of FDTD they can be very important because they also eliminate the need to use small cells, made necessary by shorter wavelengths in conducting media, throughout the solution volume. In this chapter two FDTD implementations of the surface impedance boundary condition are presented. One implementation neglects the frequency dependence of the surface impedance boundary condition, while the other is a dispersive surface impedance boundary condition that is applicable over a very large frequency bandwidth and over a large range of conductivities. Validations are shown in one (1-D) and two dimensions (2-D). Extensions to three dimensions (3-D) should be straightforward. To simplify the derivation we have considered total fields, but the extension to scattered field formulation would involve a straightforward application of the methods of Chapter 2. Because the total fields can be obtained at any time during a scattered field FDTD computation, alternatively for field components involving surface impedance conditions one could use total fields even if the remaining cells in the FDTD space were computing scattered fields.
