Research on Electromagnetic Scattering from Rough Surfaces and Composite Scattering from Rough Surface with Target
|School||Xi'an University of Electronic Science and Technology|
|Keywords||Electromagnetic scattering Transmission scattering Rough surface Layered media Analytic method Method of Moment Hybrid algorithm|
The study of electromagnetic wave scattering from rough surfaces and composite scattering from rough surface with target has been the subject of intensive investigation for its application in a number of important research areas, such as the remote sensing, the radar imaging, ocean engineering, wireless communications, surface optics, as well as the semiconductor physics. This dissertation presents theoretical studies of electromagnetic scattering from rough surfaces and composite scattering from the target below/above the rough surface. The first topic in this dissertation mainly focuses on the scattering from very rough surface and slightly rough surface of layered media, and transmission scattering from rough surface and slightly rough surface of layered media. The theory of scattering and transmission scattering from slightly rough surface of layered media is then extended to rough sea surface, the electromagnetic scattering and transmission scattering from a 2D anisotropic stratified sea surface with P-M spectrum and from the stratified sea surface simulated by an improved 2D fractal model are investigated. Finally, the composite scattering from the target located below and above the rough surface is examined. The main works and results are as follows:1. Mathematic representation of far field with plane electromagnetic wave incidence on the rough surface is derived according to the second Green Vector Theorem. The formula of bistatic scattering coefficient from the very rough Gaussian surface is then obtained by using Kirchhoff stationary phase approximation. The dependence of the bistatic scattering coefficient on the permittivity of medium, the correlation length and root mean square of rough surface, as well as the frequency of the incident wave are numerically discussed.2. The electromagnetic wave scattering and transmission scattering with plane wave incidence on the slightly rough surface of layered medium is studied using the small perturbation method. A Gaussian and an exponential distribution rough surface are presented for describing natural slightly rough surface, the formulae of scattering and transmission coefficient of layered medium for different polarizations are derived in associated with their power spectrum density. The influence of the permittivity of substrate medium, the permittivity and the mean layer thickness of intermediate medium, the correlation length and root mean square of rough surface, as well as the frequency of the incident wave on the scattering and transmission coefficient are calculated and discussed. The characteristic of electromagnetic scattering from two types of rough surface of layered media is analyzed. 3. Based on the second Green Vector Theorem, the electromagnetic wave transmission scattering from the rough surface with Gaussian correlation function is studied with the small perturbation method, Kirchhoff stationary approximation and Kirchhoff scale approximation. The transmission coefficient with different polarization are obtained by numerical implementation for different scattering angle, the scattering azimuth angle and the incident frequency. The influence of the permittivity of medium, the correlation length and root mean square of rough surface, as well as the frequency of the incident wave on the transmission coefficient for different polarizations is discussed.4. The electromagnetic scattering and the transmission scattering from a 2D stratified sea surface with P-M spectrum and improved fractal model are derived by using the theory of the electromagnetic and transmission scattering from rough surface of layered medium. The dependence of the scattering and transmission coefficient on the permittivity and the mean layer thickness of intermediate medium, the friction velocity, the wind field, the angle between observational direction and upwind direction, as well as the frequency of the incident wave are discussed by calculations. The basic characteristic, the zonal characteristic and characteristic with varying of frequency of the bistatic scattering and the transmission scattering are obtained.5. Using Method of Moment(MoM), the composite scattering from a perfect electric conducting(PEC) column located below a Gaussian and an exponential dielectric rough surface is investigated. The composite scattering is calculated and discussed for diffirent correlation length and root mean square of rough surface, the permittivity of medium below rough surface, as well as the radius and buried height of PEC column. A hybrid algorithm, combining analytic Kirchhoff approximation with MoM, is developed to solve the characteristics of composite scattering from a PEC object with arbitrary shape section above a 1D PEC surface. The essential principle of solving composite scattering from a target above a rough surface is presented, the influence of correlation length and root mean square of rough surface, the radius and height of PEC column on the composite scattering are discussed by numerical implementation.