Scattering from apertures in infinite ground planes using FDTD

A scattered field version of FDTD for scattering from an aperture in an infinite ground plane is presented. In this formulation the fields reflected from the infinite ground plane are computed analytically, not as FDTD scattered fields. This is necessary to eliminate scattering from the edges of the ground plane, where it is terminated at the FDTD outer boundary. Also, the fields scattered by the ground plane are usually of much higher amplitude than the desired aperture-scattered fields. In this formulation these fields need not be absorbed by the FDTD outer boundary. This provides more accurate calculation of low amplitude scattering from the aperture. The formulation can include materials in the aperture and on both sides of the infinite ground plane. For example, scattering from an aperture antenna with a dielectric cover backed by an aperture filled with lossy dielectric can be computed with this formulation