典型地海粗糙面的电磁散射算法的研究

发布时间：2018-01-25 08:30

本文关键词： 雷达散射截面随机粗糙面小斜率算法谱模型地貌海面　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：电磁散射是物质和电磁波相互作用后在外空间产生的宏观现象,依据电磁基本原理、结合目标特征推导出适合的算法,求解出目标物的回波信号,并提取关键信息,目前已经成为信息化作战和海况农情监测等军民领域的迫切需求。在军事领域中,武器装备大多数以自然环境作为背景,而地表和海洋是最多样的背景,其复杂性体现在附着物、形状轮廓、洋流涌浪等。本文重点研究电磁近似算法,经典理论包括基尔霍夫近似和微扰法,但两者适用范围较窄,需要进一步修正或者扩展。在此基础上,深入研究统一理论中的小斜率近似算法(SSA),主要工作是借同鉴基尔霍夫法和积分方程法相似部分的数学推导,将原本和表面高度、计算区域相关的积分项变为统计谱模型的解析公式,提高了运算速度,降低了实现的复杂度。由于自然表面的丰富多样性,依据常用的单尺度高斯谱和指数谱,进行了多尺度的扩展和混合,提出了几种新的综合谱模型。在模型具备情况下,研究了常见地物的介电特性和有效海谱模型,将电磁散射技术应用到实际的地海粗糙面中,给出了土壤、路面、风驱海洋的电磁散射数据。本文的主要贡献包括以下三个方面。1.深入分析了基尔霍夫近似和微扰法两种经典算法,给出了它们的适用范围、求解原理和散射系数公式,并进行了遮蔽修正。随后扩展到了双尺度法和积分方程法。2.重点研究了小斜率近似法,该算法适用角度广,限制条件少,通过保留展开项中的阶数来满足精确度。推导出散射振幅的三阶表达式,将得到的数据结果同矩量法进行比对,验证了正确性。对比了一阶和三阶小斜率的精确度。结合蒙特卡洛方法对粗糙面离散剖分,分析电磁散射系数同粗糙度、介电常数等关系。最后推导出了广泛适用的解析表达式,给出了多尺度高斯和指数谱以及它们的混合谱模型,尽可能地逼近真实的自然表面。3.在前面的算法和谱模型基础上,给出了沙粒、沥青混凝土、雪、土壤等典型地表附着物的介电常数特征,应用电磁散射技术求解沙土、耕地、沥青水泥路面的散射系数。因为海洋的特殊性,单独提出了三种海谱模型,并求解风驱表面的电磁散射系数。
[Abstract]:Electromagnetic scattering is a macroscopic phenomenon in the outer space after the interaction of matter and electromagnetic wave. According to the basic principle of electromagnetic, the suitable algorithm is deduced according to the characteristics of the target, and the echo signal of the target is solved. Extraction of key information has become an urgent need in military and civilian fields such as information operations and sea condition monitoring. In the military field, most of the weapons and equipment take the natural environment as the background. The surface and ocean are the most diverse background, its complexity is reflected in the appendage, shape contour, ocean current surge, etc. This paper focuses on electromagnetic approximation algorithm, classical theory including Kirchhoff approximation and perturbation method. However, the scope of application of the two is relatively narrow, which needs to be further modified or expanded. On this basis, the small slope approximation algorithm in the unified theory is studied in depth. The main work is to use the mathematical derivation of the similar parts of the Kirchhoff method and the integral equation method to change the integral terms related to the original and surface height into the analytical formula of the statistical spectral model and improve the operation speed. Because of the rich diversity of the natural surface, the multiscale expansion and mixing are carried out according to the common single-scale Gao Si spectrum and exponential spectrum. In this paper, several new comprehensive spectral models are proposed. The dielectric properties of common ground objects and the effective sea spectral model are studied. The electromagnetic scattering technique is applied to the actual rough surface of the ground sea, and the soil is given. The main contributions of this paper include the following three aspects. 1. Two classical algorithms of Kirchhoff approximation and perturbation method are analyzed in depth and their application range is given. The principle and the formula of scattering coefficient are solved, and the shading correction is carried out. Then, the two-scale method and the integral equation method are extended. 2. The small slope approximation method is mainly studied. The algorithm is suitable for a wide range of angles and has few limiting conditions. The third-order expression of scattering amplitude is derived by preserving the order of the expansion term to satisfy the accuracy. The results obtained are compared with the method of moments. The accuracy of the first order and the third order small slope is compared, and the electromagnetic scattering coefficient is analyzed with the roughness of the rough surface by the Monte Carlo method. Finally, the widely applicable analytical expressions are derived, and the multiscale Gao Si and exponential spectra and their mixed spectral models are given. Based on the previous algorithms and spectral models, the dielectric constant characteristics of typical surface appendages, such as sand particles, asphalt concrete, snow, soil and so on, are given. The scattering coefficient of sand, cultivated land and asphalt cement pavement is solved by electromagnetic scattering technique. Because of the particularity of ocean, three kinds of sea spectral models are proposed separately, and the electromagnetic scattering coefficients of wind drive surface are solved.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN011

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