Study Of The Electromagnetic Scattering From Two-dimensional Rough Sea Surface Based On Improved Wen’s Spectrum

Given the study of the electromagnetic scattering calculation from two-dimensional random rough sea surface is widely used in the fields of sea state detection, military remote sensing, target tracking and detection, the research of this scattering theory attracts much attention of many researchers at home and abroad in recent years. Firstly, this dissertation summarize the wordwide research background of the two-dimensional rough surface modeling based on power spectrum and its electromagnetic backscattering calculation, and then we point out the significance and the source of the topic. In the second part, this dissertation describe the formation mechanism and the external factors of the waves, and then we summarize the development history and the current research situation of the wave spectrum. The dissertation details several classic sea spectrum models in the world including Neumann spectrum, PM spectrum, Fung spectrum, DV spectrum, Apel spectrum, NRL spectrum, Wen’s spectrum and JONSWAP spectrum and so on. At the same time we elaborate several classic direction distribution function of Hwang, Ewans, Hasselmann, Mitsuyasu, Donelan, Guang-yi and Wen’s spectrum of direction. And not only that, we also study the adaptability of different sea spectrum models. Based on the classic simulation method of the two-dimensional random rough sea surface, in the third part we use the Monte Carlo method to simulate it, and then we use the approximate method to analyse the calculation results of the backscattering coefficient of the two-dimensional sea surface. Considering the Wen’s spectrum is suitable for different depth of the sea as well as different wind wave growth stage, the dissertation simulate the two-dimensional sea surface by improving the Wen’s spectrum combining the contrast test conclusions between Wen’s direction spectrum and Donelan direction function in the research of the two-dimensional random rough sea surface modeling. Comparing the experimental results with JONSWAP method, we illustrate the applicability of the improved Wen’s spectrum method in theory in this dissertation. The traditional TSM method in calculating the backscatter coefficient fully considers the adaptability of the KA method in solving large scale gravity waves and the SPM method in solving small scale tensile wave, which based on the theory of dividing the sea surface into gravitational waves of big roughness and capillary waves of small roughness artificially, however, the random rough sea surface in the nature is continuously changing actually. Combing the widely adaptability of SSA method both in big roughness sea surface and small roughness sea surface, this dissertation modify the classic TSM method in order to improve the unsmooth transition problem in the critical region of the two types of roughness in the fourth part. In the fifth part of the article, we illustrate several typical semi-empirical models for Backscattering Coefficient of Sea Clutter in details, including the GIT, TSC, HYB and NRL, and the models of GIT, TSC and HYB are simulated. In order to illustrate the adaptability of three kinds of models, we compare the experimental results of the improved TSM method with the simulation results of the three semi-empirical models for backscattering coefficient of sea clutter. In the research of analyzing the different fitting characteristics and the adaptability of the models we present a method named mean deviation method as the valuation criteria. Finally, comparing the electromagnetic scattering calculation results with Nathanson’s measured data, we analyse the electromagnetic scattering characteristics of the two-dimensional random rough sea surface based on the Wen’s spectrum in different sea condition, grazing angle, incident frequency, and different polarization modes of HH and VV in the sixth part.