A Study Of Simulation Methods For Transient Scattering From Time-Evolving Ocean-Like Surfaces

The analyses of transient scattering from time-evolving sea surfaces have important application in ocean remote sensing, target detection or identification in oceanic environment. It can be transformed to study the transient scattering from random rough surfaces, based on the fact that the time-evolving sea surfaces are random rough surfaces changing with the time factor. With the development of short-pulse and wide-band technologies in the field of remote sensing, study of transient scattering from random rough surfaces is becoming a hot topic. The paper is organized as follows:Firstly, transient scattering problems for two-dimensional configurations are studied in great detail. Two strategies will be adopted to deal with the time domain integral equation. One is the choice of temporal basis function, and the other is precise evaluations of matrix elements. The quadratic B-spline function will be adopted as the temporal basis function. Precise evaluations mean, in this work, that time integral will be performed analytically, singularity terms will be treated analytically too, and non-singularity terms will be evaluated by seven-point Gaussian quadrature. Detailed derivations of various time domain integral equations as well as discretizing schemes are given. Numerical results scattering from closed and open objects will be presented to verify the accuracy, stability and feasibility of the proposed method.Secondly, transient scattering problems from two-dimensional uniform dielectric objects are discussed. Both PMCHWT and Muller equations are employed. Specially, the same strategies for choice of basis functions and precise evaluations for matrix elements as the above will be used again. The purpose is, on the one hand, to examine the accuracy and the stability of the method proposed in the 2-D dielectric objects, on the other hand, to compare the performance of the PMCHWT and Muller equations.Finally, based on the research experience above, I will concentrate on analyses of transient scattering from time-evolving sea surfaces and the Doppler spectrum. Modeling of transient scattering from one-dimensional perfectly electrically conducting (PEC) sea surfaces is developed. The echoes from the sea surfaces based on the TDIE method are used to calculate the Doppler spectral characteristics. Message Passing Interface (MPI) and matrix compression store technologies will be applied to improve the computational efficiency and reduce the memory usages. Furthermore, the impendence boundary condition (IBC) method is used to cut down the number of unknowns for good conductive dielectric sea surfaces in the L band. Comparisons of scattering characteristics between good conductive and PEC sea surfaces are illustrated.