Study Of Electromagnetic Scattering From Targets On Ocean Like Surfaces

Researches on electromagnetic scattering of rough surfaces have developed quickly in recent years. It has abroad application in radar detect, remote sensing, salvage, communication and so on. Method of researches includes approximate methods and numerical method. Approximate methods such as Kirchhoff approximate, small perturbation method(SPM) is simple and quick but low precision. Numerical methods such as MOM, FDTD is precise and the simulation is more exact.In this paper, some familiar sea-spectrum are introduced, method of calculate sea-spectrum parameter is also given. Then the methods for modeling sea surfaces are outlined, including models and fractal models. According to this paper, One-dimensional rough sea surfaces are created by the method of Monte Carlo technology and Weierstrass-Mandelbort fractal function. In the end, scattering of targets above the sea is calculated using FDTD and UPML, which gives a suggestion to scattering characteristic of targets on ocean like surfaces.As for absorbing boundary condition, UPML is used instead of Mur absorbing boundary and PML. And the computing of the FDTD is simplified by the Z transformation of digital signal processing. D-B method is uses instead of E-H method, which is more suitable for dealing with dispersive material. Based on this method, radiation of wave source and scattering of infinite conductor square cylinder is analyzed, compared with MOM. In addition, the application of improved absorbing boundary condition using in 1D and 2D is given. The numerical experiments have verify this method.In the end, electromagnetic scattering of sea level is analyzed compared to rough surfaces caused by Gauss spectrum P-M spectrum and band-limited Weierstrass fraction function. We also pointed out the influence of incident wave angle and the root-mean-square high of the sea. Due to the application of compound scattering of rough surface and the goals above in military and civil affairs, the compound scattering between sea surfaces and targets above sea surfaces is studied. According to the result, it is found that the existence of the goals have great influence to back electromagnetic scattering.