FPO-Based Shooting and Bouncing Ray Method for Wide-Band RCS Prediction

The fast physical optics (FPO) method for calculating the monostatic radar cross section (RCS) of an object over a range of frequencies is extended to the shooting and bouncing rays (SBR) method where the multi-bounce phenomena of the launched rays is considered. The FPO method is an improved version of the physical optics (PO) method, which is efficient when calculating the monostatic RCS over a wide range of frequencies or/and angles. The SBR method, based on the combination of geometrical optics (GO) and PO methods, can reach a higher accuracy compared with the PO method. However, due to different length of ray tube paths, it is difficult to implement the phase compensation and phase retrieval in the SBR as that in the FPO method. In this paper, a coordinate transformation is introduced in the integral equation, which transforms the original ray tubes model into a new one. The FPO technique can then be taken on the revised model without difficulty. The validity and efficiency of the proposed method are validated though a couple of numerical experiments. Index Terms Coordinate transformation, electromagnetic scattering, fast physical optics (FPO), shooting and bouncing rays (SBR), and wide-band RCS.