Extending shooting-and-bouncing rays method with creeping waves for radar signature prediction

The shooting-and-bouncing rays (SBR) method for solving large-scale scattering problems uses geometrical optics (GO) ray tracing to extend physical optics (PO) to multi-bounce geometries. In this paper, we explain how the accuracy of SBR for predicting radar signatures can be improved with the addition of creeping-wave (CW) rays. CW rays are launched from the shadow boundaries of convex surfaces and continue along geodesic paths into the shadow region. As they propagate, the CW rays paint surface currents in the shadow region where GO rays do not directly travel, creating delayed signature features. Further, by using a creeping wave formulation that yields continuous fields across the shadow boundary, the PO currents in the lit region are simultaneously corrected, eliminating the shadow-boundary diffraction erroneously predicted by PO.