Scattering from apertures in ground planes using FDTD

The scattered field version of FDTD (finite-difference time-domain) is modified to allow calculation of scattering from an aperture in an infinite ground plane. The modification is required so that the fields reflected from the ground plane are not computed as scattered fields. These fields are usually of much higher amplitude than the desired aperture-scattered fields, and the reflection of these fields from the outer absorbing boundaries introduces errors in low amplitude scattering from the aperture. Also, the scattering from the edges of the ground plane where it is terminated at the FDTD outer boundary must be eliminated for accurate results. To demonstrate the results that can be obtained, scattering from a 100 cm /spl times/ 5 cm aperture in an infinite ground plane has been calculated.<>