Proposed an improved bidirectional ray tracing method based on the bounding volume hierarchy acceleration structure. To enhance computational efficiency while maintaining accuracy, this method employs the Surface Area Heuristic criterion to partition and assign all triangular elements to different bounding boxes. Furthermore, we enhance the bidirectional tracing method by introducing a circumradius criterion, reducing the number of facets that require backward tracing. To validate our approach, we provide two examples involving dihedral and three trihedral corner reflectors. The computational results demonstrate significant advancements in improving computational efficiency, making it highly valuable for rapidly calculating electromagnetic scattering using physical optics methods.

In this letter, a novel method is proposed to rapidly simulate the multiaspect monostatic radar cross section of electrically large complex targets based on the shooting and bouncing ray method (SBR). The core of the method is to use the inheritance of the illumination to determine the illumination of the target surface, rather than independently simulating for each required aspect angle as in the traditional SBR method. To achieve this, the illumination variation on the target surface is summarized and the genetic illumination information is defined. The error of the method is also discussed and the multiple precalculation solutions is proposed to control the error. Different simulation examples show our method has good general applicability and great efficiency. Finally, a realistic aircraft is simulated at 10 GHz using the multiple precalculation solution.

An enhanced KD-tree-based ray tube subdivision shooting and bouncing ray method (SBR) is proposed for fast radar cross section (RCS) prediction of electrically large targets. In the enhanced subdivision process, according to the position code of the leaf nodes intersected by the parent ray tube, the traversal process of the child rays starts directly from the deepest common node (DCN) instead of the root node. In addition, an improved ray tracing process is proposed to avoid double ray tracing. The neighbor search technique also seamlessly integrates with the new SBR to accelerate the high-order ray tracing. The highly compatible integration of multiple acceleration techniques enables the new SBR to realize cumulative acceleration. Simulation examples validate the accuracy and high efficiency of the new SBR with acceptable and stable RAM consumption.

The coupling of two antennas can be described with mutual impedance. This paper proposes computing the mutual impedance by reaction theorem, which involves integrating vector products of near fields over a sphere surrounding the second antenna. We express the near fields of both antennas by the vector Spherical Harmonic Transform (SHT), evaluate the near fields of the first antenna on the eccentric sphere by a new FFT/interpolation method efficiently, and then obtain the mutual impedance by the reaction integrals. This new method has a computation complexity of O(N3), where N represents the truncation order in SHT. The comparison with the Higher Order Moment Method (HOMOM) indicates that the proposed method is a fast, accurate, stable and universal method to analyze the coupling of any two antennas.