Modeling the forward-scatter cross section of 3-dimensional objects by means of the shadow contour theorem: an assessment

In this contribution, we analyze the forward-scatter cross-section (FS-CS) of three-dimensional (3-D) metallic targets in a forward scatter radar (FSR) system, moving along arbitrary trajectories, in the transition between far- and near-field regions with respect to the receiving antenna. A vector formulation is introduced, together with a simplified approach based on a physical-optics solution of the scattering integral, and validated by means of full-wave numerical evaluations. This model is exploited to characterize the FS-CS of 3-D targets that have specific 2D contours and cross the baseline at variable distances and directions with respect to the receiving antenna. For these targets, the application of an extended Shadow Contour Theorem (SCT) provides an extremely simplified model that can be particularly useful for a fast and accurate characterization of the FS-CS, leading, in specific cases, to closed-form analytical formulation of the scattering. By comparing the FS-CS of the 3-D object having both sharp edges and smooth shapes with the results of the SCT applied to the 2-D shapes, an accurate assessment of the theorem is outlined. This provides useful insights on the application of the SCT in conjunction with a PO solution of the object contour, for developing advanced signal processing techniques based on a realistic but simplified FS-CS target