Incremental Fringe Formulation for a Complex Source Point Beam Expansion

An incremental fringe formulation (IFF) for the scattering by large metallic objects illuminated by electromagnetic complex source points (CSPs) is presented. This formulation has two main advantages. First, it improves the accuracy of physical optics (PO) computations by removing spurious scattered field contributions and, at the same time, substituting them with more accurate Incremental Theory of Diffraction field contributions. Second, it reduces the complexity of PO computations because it is applicable to arbitrary illuminating fields represented in terms of a CSP beam expansion. The advantage of using CSPs is mainly due to their beam-like properties: truncation of negligible beams lowers the computational burden in the determination of the solution. Explicit dyadic expressions of incremental fringe coefficients are derived for wedge-shaped configurations. Comparisons between the proposed method, PO and the Method of Moments (MoM) are provided.