Electromagnetic scattering from a rough surface of layered medium is investigated,and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough surface with exponential correlation function is presented for describing a rough soil surface of layered medium,the formula of its scattering coefficient is derived by considering the spectrum of the rough surface with exponential correlation function; the curves of the bistatic scattering coefficient of HH polarization with variation of the scattering angle are obtained by numerical calculation. The influence of the permittivity of layered medium,the mean layer thickness of intermediate medium,the roughness surface parameters and the frequency of the incident wave on the bistatic scattering coefficient is discussed. Numerical results show that the influence of the permittivity of layered medium,the mean layer thickness of intermediate medium,the rms and the correlation length of the rough surface,and the frequency of the incident wave on the bistatic scattering coefficient is very complex.
基于矩量法(method of moment,MOM)及基尔霍夫近似(Kirchhoff approximation,KA)研究了分层粗糙面的电磁散射问题。首先,利用经典MOM求解了上层粗糙面的总场,包括直接入射场及由其激发的直接散射场。然后,将锥形入射波引入到传统KA中,利用其求解了分层粗糙面的透射场。数值计算并讨论了粗糙面高度起伏均方根、相关长度及分层粗糙面间距等参数对分层高斯粗糙面双站散射系数的影响。
This paper is devoted to the study of polarization properties,scattering properties and propagation properties of global positioning system(GPS) scattering signal over the rough sea surface.To investigate the polarization and the scattering properties,the scattering field and the bistatic scattering coefficient of modified Kirchhoff approximation using the tapered incident wave is derived in detail.In modeling the propagation properties of the GPS scattering signal in the evaporation duct,the initial field of parabolic equation traditionally computed by the antenna pattern using fast Fourier transform(FFT) is replaced by the GPS scattering field.And the propagation properties of the GPS scattering signal in the evaporation duct with different evaporation duct heights and elevation angles of GPS are discussed by the improved discrete mixed Fourier transform taking into account the sea surface roughness.
Composite electromagnetic scattering from a two-dimensional(2D) ship-like target on a one-dimensional sea surface is investigated by using the finite-difference time-domain(FDTD) method.A uniaxial perfectly matched layer is adopted for truncation of FDTD lattices.The FDTD updated equations can be used for the total computation domain by choosing the uniaxial parameters properly.To validate the proposed numerical technique,a 2D infinitely long cylinder over the sea surface is taken into account first.The variation of angular distribution of the scattering changing with incident angle is calculated.The results show good agreement with the conventional moment method.Finally,the influence of the incident angle,the polarization,and the size of the ship-like target on the composite scattering coefficient is discussed in detail.
This paper studies the influence of wind parameters and fractal dimension from an improved two-dimensional sea fractal surface on the polarimetric scattering by using facet integration.A two-dimensional improved sea surface simulated is discretized into three matrices of sea surface facets including a height matrix and two slope matrices on orthogonal directions.Based on the Kirchhoff approximation,the polarimetric scattered field is derived in the Cartesian coordinate system by integration of three matrices mentioned above.Finally,the fully polarised radar cross section is numerically simulated and the dependence of the polarimetric scattering on the sea fractal surface,such as the wind speed,the wind direction,as well as the fractal dimension,is discussed in detail.
