Detailed near/far field modeling of complex electrically large three dimensional structures

The finite-difference time-domain (FD-TD) method is shown as a means of accurately computing electromagnetic scattering by arbitrary-shaped, extremely complex metal or dielectric objects excited by an external plane wave. In the present method, one first uses the FD-TD method to compute the near total fields within a rectangular volume which fully encloses the object. Then, an electromagnetic field equivalence principle is invoked at a virtual surface of this rectangular volume to transform the tangential near scattered fields to the far field. To verify the applicability of this method, the surface currents, near scattered fields, far scattered fields, and radar cross section of canonical two-dimensional and three dimensional objects are presented. For these cases, it is shown that the FD-TD method provides magnitude of current and field predictions which are within + or - 2.5 percent and further phase values within + or - 3 deg of values predicted by the method of moments (MOM) at virtually every point including in shadow regions. The FD-TD method is presently being extended to three-dimensional structures as large as twenty wavelengths.