Research On High-frequency Methods For Electromagnetic Scattering From Complex Target

Recently, the application about random rough surfaces has become more and more important, so research on electromagnetic scattering from it has been paid more attention by the researchers, especially, the computation of Radar Cross Section(RCS) about the complex target composed of random rough surfaces and objects is becoming hot issue in the field of computational electromagnetics(CEM), which has a huge impact on persons’ daily life. However, for the complexity of the complex target, in order to compute the electromagnetic scattering from it, there are some strict requirements on application range, and computational efficiency and memory consumption of methods. However, most methods seem much less effective owing to heavy computational simulation, enormous memory requirement and other limit factors. In this thesis, shooting and bouncing rays(SBR) will be used to solve computation of the electromagnetic scattering from the complex target according to its wide use range, high computation efficiency and computing precision.Firstly, the history about the research on the electromagnetic scattering from random rough surfaces is reviewed and the typical computational methods are briefly introduced, their merits, shortcomings and the application range are summarized in the thesis. And in view of all the characteristics of random rough surfaces, SBR is chosen to study the electromagnetic scattering from the random rough surfaces, which will be the key content in the thesis.Secondly, the complex target usually has complicated shape, when simulating it represented by flat triangles, it will lose all the data about the surface curvature of the complex target, so the computational accuracy of SBR will decries, especially, when the targets contain concave structure, the SBR will give wrong computational results. In order to overcome the difficulty, the Virtual Divergence Factor(VDF) is introduced in the thesis, which can amend the loss of surface curvature. As a result, with the VDF, the SBR can provide credible results with high computational accuracy. Moreover, the complex targets are usually very large compared with the wave length, so it will use a large numbers of flat triangles to simulate them, which will require SBR spending a lot of time to trace rays. In order to solve the problem, the Kd-tree data structure is introduced to accelerate the process of rays’ tracing. Furthermore, on the basis of Kd-tree data structure, the adjacent rays traverse(ART) technology is firstly proposed in the thesis, which can traverse the Kd-tree quicker, so the computational efficiency of SBR is further improved.Lastly, owing to the improvement described in the previous part, when SBR is used to compute the electromagnetic scattering from complex targets, it can provide a high-precision result, which match very well with ones provided by the numerical methods and the test ones. So it proves that SBR has these merits such as wide application range, high computational efficiency and accuracy. Finally, SBR is successfully used to compute the RCS of complex targets such as ocean surface with missile or ship.