Scattering from a corrugated thick screen

A closed form, high-frequency solution is presented for the scattering in the near zone by a semi-infinite thick screen, when it is illuminated by a line source at finite distance. This solution is derived for a thick screen with perfectly conducting side walls, and either perfectly conducting or artificially soft boundary condition on the top face joining the two wedges. This last condition is practically obtained by etching on this face a quarter of a wavelength deep corrugations with a small periodicity with respect to the wavelength. Owing to the particular properties of the artificially soft surface, a strong decoupling effect in the shadow region is achieved for both polarizations; thus, an effective shielding from undesired interferences is obtained. The formulation adopted is based on the spectral approach, which is summarized. The artificially soft boundary condition is accounted for by the spectral Green´s function. The procedure leads to a double spectral integral that is asymptotically evaluated. Thus, a high-frequency solution is obtained, that is described as a superposition of different diffracted field contributions, including doubly diffracted rays. This solution uniformly describes the total field, including those aspects where the transition regions of the diffracted fields from the two edges overlap, and an ordinary application of standard UTD fails. Numerical results are presented and discussed in order to emphasize the shielding effectiveness of the corrugated screen.