三维含卷浪海面电磁散射的IPO优化算法研究

发布时间：2018-03-17 10:13

本文选题：卷浪　切入点：电磁散射　出处：《西安电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：海面的电磁散射研究不仅在军事国防领域的雷达制导、目标探索等方面都担当着重要的角色而且在民用等领域也愈加受到重视。海面的雷达回波(海杂波)通常会将利益目标的回波信息淹没掉,所以研究复杂条件下海面散射特性有着重要的意义。本文应用优化加速后的迭代物理光学(IPO)法初步讨论了低掠角下三维含卷浪(Overturing Wave)海面的电磁散射特性,分析了海尖峰形成机理,为三维含卷浪海面模型的建立及应用高频算法求解含卷浪问题提供了解决思路。本文首先对海面的基本特征参数进行了介绍,给出了几种海谱模型并讨论了由海谱反演海面的基本方法。介绍了加入风速影响的改进虚拟现实场景中的一维卷浪模型,该模型能够与相同风速下风浪场海面浪高与波长统一,并给出了其模型的仿真结果。其次讨论了高频近似算法物理光学法(PO),分别将导体情况与介质情况的公式进行了推导,并给出算例及验证;然后基于物理光学法讨论了处理导体与涂覆有耗介质的腔体及角反射器散射问题的迭代物理光学法。随后应用IPO法处理了海面电磁散射问题,并进行了优化处理,将迭代物理光学法的雅克比循环迭代改进为前后向(Forward Backward:FB)迭代,并引入欠松弛算法,得到带有松弛因子的前后向迭代物理光学(FBIPO)法公式。为进一步提高其运算效率,考虑了OpenMP技术,进行计算机的CPU并行加速,构建了整体性能较高的并行方案,有效地减小了迭代过程的时间消耗。最后,讨论了三维含卷浪海面模型的仿真建立,将特定风速下的三维卷浪模型前后附加PM谱生成的三维海面使之更接近实际海况,介绍了含卷浪海面模型构建的具体思路;将前文中经过优化处理后的迭代物理光学法应用到此模型中,讨论了电磁波在低掠角入射下卷浪从产生到坍塌形态下海面的散射特性。因为卷浪形成后类似一个腔体结构,可以将其等效为一个谐振腔,应用IPO方法处理腔体问题模式来处理海面含卷浪部分。当掠射角度逐渐减小时,卷浪的谐振腔作用越来越明显,与卷浪形成初期的散射特性完全不同,后向回波明显增强,并且后向回波HH极化明显大于VV极化,出现海尖峰现象。卷浪坍塌后,破碎区域会产生白冠现象,文中将卷浪破碎后卷入空气形成的海水与气泡混合的海面结构进行海水介电常数修正处理,并讨论了卷浪破碎区应用修正等效介电常数海面的散射特性。
[Abstract]:The study of electromagnetic scattering from the sea surface is not only for radar guidance in the field of military and national defense, Target exploration plays an important role and has attracted more and more attention in the field of civil affairs. Radar echo (sea clutter) on the sea surface usually inundated the echo information of the benefit target. Therefore, it is of great significance to study the scattering characteristics of sea surface under complex conditions. In this paper, the electromagnetic scattering characteristics of three dimensional sea surface with wave overhauling at low grazing angle are discussed by using the optimized accelerated iterative physical optics (IPO) method. In this paper, the formation mechanism of sea spike is analyzed, which provides a solution for the establishment of 3D sea surface model and the application of high frequency algorithm to solving the problem of wave entrainment. In this paper, the basic characteristic parameters of sea surface are introduced. In this paper, several sea spectral models are given, and the basic methods of sea surface inversion from sea spectrum are discussed. An improved one dimensional wave rolling model with wind speed effect is introduced. The model can be unified with the sea surface wave height and wavelength of the wind wave field under the same wind speed. The simulation results of the model are given. Secondly, the physical optics method of high frequency approximation algorithm is discussed, and the formulas of conductor and medium are deduced, and an example is given and verified. Then based on the physical optics method, the iterative physical optics method is discussed to deal with the scattering problem of the conductor and the cavity and angular reflector coated with lossy dielectric, and then the IPO method is used to deal with the electromagnetic scattering problem of the sea surface, and the optimization treatment is carried out. The Jacobian cycle iteration of iterative physical optics method is improved to forward backward forward: FB iteration, and an underrelaxation algorithm is introduced to obtain the formula of backward iterative physical optics FBIPO method with relaxation factor. Considering the OpenMP technology, the CPU parallel acceleration of the computer is carried out, and a parallel scheme with high overall performance is constructed, which can effectively reduce the time consumption of the iterative process. Finally, the simulation of the 3D sea surface model with rolling waves is discussed. The 3D sea surface generated by adding PM spectrum before and after the 3D wave model under specific wind speed is more close to the actual sea condition, and the concrete idea of constructing the sea surface model with rolling wave is introduced. The iterative physical optics method, which has been optimized in the previous paper, is applied to this model. The scattering characteristics of electromagnetic waves under low grazing angle are discussed, because the wave is similar to a cavity structure after it is formed. It can be equivalent to a resonator, and the IPO method is used to deal with the problem mode of the cavity to deal with the part of the sea surface with waves. When the grazing angle decreases gradually, the effect of the cavity is more and more obvious. The scattering characteristics are completely different from the initial wave formation, and the backward echo HH polarization is obviously larger than the VV polarization, and the sea spike appears. After the collapse of the wave, the white crown phenomenon will occur in the broken area. In this paper, the structure of sea surface mixed with air and sea water after wave breaking is modified, and the scattering characteristics of sea surface with modified dielectric constant in the breakup region are discussed.
【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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