一维含破碎波粗糙海面总体电磁散射的FMM研究

发布时间：2018-10-10 18:19

【摘要】：随着海洋资源的开发和其战略位置的重要性,对粗糙海面的电磁散射特性研究越来越受到各国重视。由于海面环境的复杂多变,海杂波对于雷达目标探测,截获和制导等等带来干扰,所以分析不同海态海况不同条件下的海面电磁散射刻不容缓。本论文就快速多极子方法(FMM)和基于矩量法(MOM)的并行计算方法在低掠角下的破碎波电磁散射应用中展开理论研究。论文主要工作如下:1.对粗糙面电磁散射基本理论进行了简述,包括雷达方程,海水介电常数的双Debye模型,入射锥形波各参数的选择,使用蒙特卡罗方法模拟生成了PM海谱,结合LONGTANK破波模型,建立了破碎波的几何模型。2.简单介绍了矩量法(MOM)和快速多极子方法(FMM)的基本原理,进而推导了快速多极子方法的计算公式,研究了低掠角下快速多极子方法在粗糙海面电磁散射中的应用,在不同极化,不同入射角度,不同频率,不同风速下的导体海面和介质海面的电磁散射系数随散射角度的变化。3.将基于MPI的并行计算和基于OpenMP的并行计算引入到粗糙海面的电磁散射快速算法当中,给出了并行算法的具体加速过程,并将两种并行算法计算结果和时间与矩量法或是快速多极子方法进行了对比,验证了并行算法的高效精确,突出了并行算法在求解矩阵当中的优势。4.将快速多极子方法和并行计算方法应用到破碎波的电磁散射计算当中,分析讨论了破碎波生成过程当中的不同时期的电磁散射状况,依据其后向电磁散射随入射角的变化,在破碎波形成前期,未显现多径效应,VV极化大于HH极化,在破碎波生成中期,开始出现浪尖,VV极化减弱而HH极化增强,随着海面演变,在破碎波形成后期,海面出现完整卷浪,明显的海尖峰现象,HH极化和VV极化差异变大
[Abstract]:With the development of marine resources and the importance of their strategic position, more and more attention has been paid to the electromagnetic scattering characteristics of rough sea. Due to the complexity of sea environment and the interference of sea clutter to radar target detection, interception and guidance, it is urgent to analyze the electromagnetic scattering of sea surface under different sea conditions. In this paper, the fast multipole method (FMM) and the parallel computing method based on the method of moments (MOM) are studied in the applications of electromagnetic scattering of broken waves at low grazing angles. The main work of this paper is as follows: 1. The basic theory of electromagnetic scattering from rough surface is briefly described, including the radar equation, the double Debye model of the dielectric constant of seawater, and the selection of parameters of the incident conical wave. The PM sea spectrum is simulated by Monte Carlo method and combined with the LONGTANK wave breaking model. The geometric model of broken wave is established. 2. In this paper, the basic principles of (MOM) and (FMM) are introduced, and the formula of fast multipole method is deduced. The application of fast multipole method in electromagnetic scattering from rough sea surface at low grazing angle is studied. The variation of electromagnetic scattering coefficient of conducting sea surface and medium sea surface with different incident angle, frequency, wind speed and scattering angle. 3. The parallel computation based on MPI and the parallel computation based on OpenMP are introduced into the fast electromagnetic scattering algorithm of rough sea surface, and the concrete acceleration process of the parallel algorithm is given. The results and time of the two parallel algorithms are compared with the method of moments or the fast multipole method, which verifies the high efficiency and accuracy of the parallel algorithm, and highlights the advantages of the parallel algorithm in solving the matrix. 4. The fast multipole method and the parallel calculation method are applied to the electromagnetic scattering calculation of broken waves. The electromagnetic scattering conditions in different periods during the process of breaking wave generation are analyzed and discussed. According to the variation of the backscatter with the incident angle, In the early stage of breaking wave formation, there was no multipath effect. VV polarization was larger than HH polarization. In the middle stage of breaking wave formation, wave tip began to appear. VV polarization weakened and HH polarization increased. With the evolution of sea surface, the whole wave appeared in the later stage of breaking wave formation. The obvious sea spike phenomenon, the difference between HH polarization and VV polarization becomes bigger.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN011

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