The Study Of Electromagnetic Scattering Method To The Ground And Sea Rough Surface

Electromagnetic scattering is a macroscopic phenomenon in outer space generated by the interaction between substances and electromagnetic waves. Algorithm is derived from the electromagnetic principle and substance characteristics. Extracting the useful information from the target echo signal has become an urgent demand in the military attack field and agricultural monitoring. Weapons and attack targets in most cases are surrounded by natural environment, which is the most complicated and diversified circumstance. Surface deposits, geomorphology ecological, topographical contours, and ocean waves are the difficult situations in the study. The calculating results determine the accuracy and reliability in the armed defense. The thesis focuses on the electromagnetic approximation algorithms.The classical theories are Kirchhoff approximation(KA) and perturbation method. Their scope is narrow, so there is demand for the in-depth study of small slope approximation, which is a kind of unified theory. The main objective of this thesis is to derive the analytical formula of small slope algorithm, which is based on the physical theory and mathematical derivation of similar parts in KA. In practical applications, taking into account the rich diversity of natural surfaces, with the usual Gaussian spectrum and exponential index, a variety of new integrated spectrum has been achieved. Then application of electromagnetic scattering techniques are put into the use of typical ocean surface and land rough surface. The main contributions of the thesis include:The basic equations and boundary conditions for electromagnetic scattering are reviewed and the scattering parameters are given. Statistical methods and mathematical models are used to describe the random rough surfaces. Analyses of the Kirchhoff approximation and Perturbation method is presented, as well as the scope, principles and scattering equations. Then a simple correction to Kirchhoff approximation for the shading effect is given.The small slope approximation method id mainly investigated. The algorithm applies a wide angle, less restrictive conditions and we can get the result to a certain accuracy by reserving the order of the expanding formula. The comparison of the data with the result from the method of moments proves its correctness. Combined with Monte Carlo method we can solve the electromagnetic scattering of a specific rough surface, and subsequently we deduce the widely used analytical expressions. We also put forward the multi-scale Gaussian and exponential spectrum and their mixed spectrum, in order to simulate the real surfaces as much as possible.On the basis of the previous algorithms and spectral model, the dielectric constants of sand, asphalt, snow and other typical surface nature are given. These the technologies are used to solve the scattering of electromagnetic from the concrete background. Considering the particularity of the ocean, we provide three special sea surface models, and obtain the electromagnetic scattering coefficients.