Research On Characteristics And Metheds Of Electromagnetic Scattering From A Random Rough Surface

Research on electromagnetic scattering from random rough surfaces with or without targets is of great significance in both reaserch and applications. Therefore this is a hot research topic in the computational electromagnetics field. In this thesis, both electromagnetic scattering from a rough surface and composite scattering of the combinative target composed of a rough surface and a target will be analyzed. The main contents include of two aspects: geometric modeling and electromagnetic modeling, which are summarized as follows:1、The specific process of generating a rough surface using the Monte Carlo method is given. It is analyzed how the rough surface profiles of PM spectrum, Gauss spectrum and Exponent spectrum change with their statistical parameters. NURBS surface modeling method is introduced into the geometric modeling of the rough surface based on which a unified modeling can be achieved by performing the Boolean operation. The intersection between a rough surface and a targe does not need special handling when creating the mesh of a composite model.2、When simulating rough surfaces of Gaussian spectrum, Exponent spectrum and PM spectrum, different analytical methods including PO and IPO are used respectively to analyze the influence of the different incident parameters, dielectric properties and the roughness on scattering characteristics.3、For the composite scattering of a rough surface and the above target, the composite scattering model based on iteratively coupled idea and the procedure of the PO+MLFMA hybrid algorithm are presented, and composite scattering characteristics of PEC or dielectric rough surfaces and the above targets under different circumstances are discussed.4、When the target intersects the rough surface, the rough surface and the target are considered as a whole target. The numerical method MLFMA is utilized to calculate the composite scattering coefficients, and the effects of the rough surface roughness and the target size on the composite scattering are investigated.5、To simulate the scattering from different kinds of composite models, i.e. a target above a rough surface and a target half embedded in a rough surface, a high-frequency hybrid method based on ray-tracing principle is proposed as GO+PO+PTD. The hybrid method has a highly computational efficiency, a low requirement on the establishment and the meshing of composite mode. Provided that the rays are traced correctly, the coupling effect between the target and rough surface will be considered adequately. To show its above advantages, the composite scattering cross section of a missile, a simplified ship model and a rough surface is computed by GO+PO+PTD.The computational methods and the scattering results in this thesis provide a valuable reference for the study on EM scattering characteristics of the rough surface with or without targets.