Study On Electromagnetic Scattering Of Combinative Objects Based On TDSBR-FDTD Hybrid Approach

The electromagnetic (EM) scattering characteristic of target has become an important part of radar system design, and the EM numerical simulation technologies have become important tools for analyzing the EM scattering characteristic of target. The EM numerical methods can be categorized into high-frequency (HF) methods and low-frequency (LF) numerical methods. The HF methods have advantages in fast evaluation of electrical large objects and the LF methods provide high precision in the analysis of electrical small objects contain electrical small structures. As for the combinative objects, both of the methods can hardly meet the requirements of computational speed and accuracy in the same time, thus the hybrid methods have been applied to solve this problem.This paper first introduces the basic principles of the shooting and bouncing rays (SBR) method, and the process of ray tracing and physical optics integration of traditional SBR are studied.For the flat surface scatterers, an improvement has been made about ray-tracing procedure and intersection tests, based on traditional shooting and bouncing rays (SBR). Combine with SBR, this paper studies a fast method of ray/triangle intersection. The surface of the targets was subdivided by triangles twice, obtaining low density of triangles using for intersection tests and high density of triangles using for ray tracing as the original ray tubes. After ray-tracing program, the electromagnetic scattering problem can be carried out by physical optics (PO) integration. The results of the proposed method are compared with those in the references. The good agreement between the results proved the preciseness of this method. And the efficiency of the method was proved by the results of different densities of subdivision.Based on the Frequency-Domain SBR (FDSBR), the Time-Domain SBR (TDSBR) is studied. The process of ray tracing and blind judgment is same with the FDSBR. The integration in TDSBR is carried out by radon transform interpretation. Through the numerical simulation of the model of one time bouncing and multiple bouncing, the method is verified to be correct.Finally, the TDSBR-FDTD hybrid approach has been established. The calculation area divided into TDSBR area and FDTD area. When dealing with the coupling of two areas, the near-to-far field extrapolation technique based on Kirchhoff’s surface integral representation is used and a sequential transfer method is developed. The data storage during the coupling is introduced. The sequential transfer method has some advantages in high efficiency and small amounts of computer memory. The numerical simulation for radiation model and scattering model is carried out, and the feasibility of the hybrid method is proved by the simulation results.