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海面上方目标复合电磁散射的实验测量与理论研究

Experimental Measurement and Theory Study on the Composite Electromagnetic Scattering from a Target Above Sea Surface

【作者】 张景剑

【导师】 吴振森;

【作者基本信息】 西安电子科技大学 , 无线电物理, 2010, 硕士

【摘要】 论文研究了一维、二维导体海面与其上方目标高频复合电磁散射问题。目标与海面复合散射的总场分为海面和目标的一次散射场以及二次散射场来求解,并考虑了目标的边缘绕射场。利用基尔霍夫近似分别计算了一维、二维导体粗糙海面电磁散射场,给出了海面散射场随入射角以及散射方位角的变化关系,分析了入射波频率、海面风速等对海面散射场的影响;利用等效边缘电磁流法计算了导体正方形平板、菱形板、正方体、圆柱、尖锥柱以及梯形体等目标的散射截面,并将结果与商业软件CST和FEKO进行了比较,两者吻合得较好;将互易性定理和等效边缘电磁流法结合起来研究了目标与海面的耦合散射特性。分别给出了导体平板、尖锥柱以及梯形体和海面的复合后向散射截面随入射角变化的数值结果,改进了未考虑目标边缘绕射场的结果;分析了目标尺寸、目标距离海面的高度、海面风速以及入射波频率对复合散射场的影响;并将数值结果与实验测量结果进行了对比,两者吻合得较好。本文最后利用时域积分方程法计算海面的时域散射场,给出了海面的表面电流,分析了不同入射角对后向远场结果的影响。介绍了时域等效边缘电磁流法的一般理论,给出了求解目标时域场的一般步骤。

【Abstract】 The characteristics of high-frequency composite electromagnetic backscattering from a target above one- or two-dimensional conductor sea surfaces are investigated. The total composite scattering field can be split into first order scattering field and second order coupling scattering field to be calculated with the diffraction of the target fringe taken into account. The Kirchhoff Approximation (KA) is used to calculate the backscattering radar cross section (RCS) of 1-D and 2-D sea surface, respectively. The scattering field of sea surface versus incident angle and azimuth angle is presented. The impact of frequency and wind speed on RCS of sea surface is discussed. The RCS of conducting plate, rhombus, cube, cylinder, cone-cylinder and trapezia are computed by the method of equivalent edge currents (MEC). And it is compared to the results simulated by commercial software CST and FEKO, which get good agreement with each other. The reciprocity theorem method and the MEC are employed together to calculate the coupling scattering field between a target and sea surface. The numerical results of the backscattering RCS with different incident angle for the conducting plate, cone-cylinder and trapezia above the sea surface are presented, respectively, with the results improved from unconsidered diffraction. The dependence of the composite backscattering RCS on the target size, the height, the wind speed of sea surface and the frequency of incident wave is analyzed, which is in good agreement with the results of experiment. The time domain scattering field of sea surface is calculated based on the TDIE and the surface current of ocean is presented in the paper. The influence of incident angle on backward far field is analyzed. The theory of TD-EEC is introduced and the process of calculating time domain field of target is given.

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