The Analysis?Computation And Application Of Scattering From Multilayer Random Rough Sea Surfaces And The Composite Scattering From Rough Surface And Target

Electromagnetic scattering from rough surface and its composite with target are widely used in the field of Marine remote sensing.In the Marine remote sensing detection, we can consider the surface as a random rough surface and the ocean surface can be simulated based on the ocean spectrum. Then we can get the backscatter coefficient of the surface according to the corresponding electromagnetic theory.This thesis mainly uses three electromagnetic field numerical algorithms to calculate the backscatter scattering coefficient from the rough surface,which are the method of moments(MOM), the finite-difference time-domain method(FDTD) and accelerated method of MOM-fast multipole method(FMM).Then we can get relationship between the statistical parameters of the rough sea surface(such as the RMS slope?the RMS height of the rough sea surface) and the backscatter scattering coefficient.Because above the sea surface wind speed can affect the statistical parameters of the surface, then the relationship between scattering coefficient and the wind speed can be concluded which can provide certain theoretical support and basis for wind velocity retrieval.This thesis also studied the sea surface and the target compound electromagnetic scattering, so as to provide certain theoretical basis and reference for target detection.This thesis first analyzes some mainstream analytical and numerical algorithms of the the research on the random rough surface scattering. Then a model of the one-dimensional rough surface based on gaussian spectrum is introduced.Then several kinds of classic sea surface spectrum are introduced, based on which the random rough sea surfaces are generated.Then the method of moments is introduced to solve the electromagnetic scattering problems. In the process, this thesis respectively discusses electromagnetic scattering from the single layer conductor rough surface, the single layer medium rough surface, the single layer medium rough surface compounded by the target and the double layer medium rough surface. Then the thesis compared the results with the results of the kirchhoff approximation(KA), and in their effective application scope good matching results are obtained. Then the thesis describes in detail using the finite difference time domain method to deal with the electromagnetic scattering problems, and the calculated results are compared with the result of the moment method, the trend is consistent,which verify the validity of the results of the electromagnetic scattering problems. When calculating electromagnetic scattering problem of the big size coarse surface, the computer memory method of moments needs will increase rapidly, and the calculation time will greatly increase. Sometimes the efficiency is two low to complete the calculation Then the thesis introduces the accelerate algorithm of the method of moments- fast multipole algorithm, and use it for the calculation of the electromagnetic scattering.After comparing the results with the method of moments, results in good consistency are achieved.As an application of the electromagnetic scattering from rough surface, we introduced the current development of altimeter wind velocity retrieval and several classic altimeter wind velocity retrieval algorithms, but most of these algorithms based on the empirical formulas obtained from the measured data. This thesis tried to use the numerical method – MOM – to calculate rough surface electromagnetic scattering under different wind speed in the altimeter incident angles. Compared with the empirical formulas, the trend is generally consistent, which can provide a certain support for altimeter wind speed retrieval and has practical application value.