Beam Tracing with Physical Optics for Angular Glint Calculation in Near Field

Angular glint is an important factor affecting radar measurement accuracy, which comes from the interaction of multiple scattering centers of the extended target and cannot be eliminated. In the near-field region, angular glint exerts a more significant impact on radar tracking accuracy, and may even cause radar pointing to fall beyond the actual target extent. There are two methods for calculating angular glint, the Poynting vector method (PVM) and the phase gradient method (PGM), of which PVM is commonly used for theoretical calculations and PGM is often used for practical measurements. In this paper, the angular glint is calculated by PVM using the scattered field of the target. Therefore, optimizing the computational efficiency of the near-field scattered field is of utmost significance. While Geometrical Optics (GO) and Physical Optics (PO) are commonly used methods for high-frequency electromagnetic scattering calculations, GO can only calculate the scattered field in the specular direction, and PO is not applicable to scenarios involving multiple reflections. Therefore, this paper proposes a physical optics method based on beam tracing, which can not only calculate the scattered field in any direction but also solve the problem of multiple reflections. Furthermore, the PO method requires the initial subdivision of the target into small facets. The size of these facets is dependent on the frequency, and the number of facets for the target substantially increases as the frequency rises, thereby affecting computational efficiency. In the proposed method in this paper, the target can be composed of large-size facets, allowing for the rapid computation of the near-field scattering field, and higher computational efficiency can be obtained by introducing space acceleration structure and parallel computing techniques.