Comparison of shielding by infinite and finite planar grids over a lossy half space

The shielding properties of finitely extended and infinitely extended parallel thin-wire grids over a lossy half space are considered when illuminated by a downcoming plane wave whose electric field vector is parallel to the wires. Numerical comparisons of the electric field in the illuminated, transition, and shadow regions for the finitely extended case are made with the electric field in the shadow region for the infinitely extended case. The field responses of both grids in the shadow region are shown to be similar. Edge effects, however, may be significant if the field is observed near the truncation of the grid of finite extent. It is demonstrated that a reasonable approximation for the current distribution in the current region of the finite grid is the computed value determined for the infinite grid