First-order equivalent current and corner diffraction scattering from flat plate structures

The equivalent-current concept is used to compute the scattering patterns of flat plate structures. It is also used to obtain the broadside scattering lobe for any incidence plane. The essential feature is that only the components of the equivalent current perpendicular to the incidence plane are used. No special treatment of the singularity in the plane-wave diffraction coefficient (which is the basis of the equivalent-current concept) is required. Instead, the choice of equivalent-current components is such that the singularity at one edge segment is canceled by the singularity at the opposite edge segment. For modern-day computers there is sufficient accuracy that the main scattering lobe can be obtained in the limit as one approaches broadside. The same results can be obtained for plate structures made of straight edges by using a new corner-diffraction analysis. For certain cases where the observation angle is sufficiently removed from normal incidence to an edge, the corner-diffraction analysis appears to yield more accurate results.