大区域地理环境的电磁建模及高效抛物方程方法研究

发布时间：2018-06-30 01:27

本文选题：电波传播 + 抛物方程　；参考：《西南交通大学》2016年博士论文

【摘要】：近年来,复杂电磁环境中电波传播问题的研究已成为国内外学者关注的热点问题。构建复杂环境要素的可计算模型,并实现大区域复杂环境中电磁分布特性的快速仿真和分析,能为无线通信、电磁监控、电子对抗等实际应用提供关键的数值模拟技术和数据支撑,具有非常重要的军用以及民用价值。与已有的电波传播模型相比,抛物方程本身就能体现电波传播的折射与绕射效应,可以充分考虑不规则地表结构、非均匀媒质等复杂环境对电波传播的影响,且其SSFT解法在传播方向的网格步长几乎不受波长限制,因此非常适合于大区域复杂环境中电磁覆盖特性预测。本文基于抛物方程,对森林、粗糙海面等复杂地理环境的电磁建模方法以及抛物方程的高效网格模型、高效数值解法等进行了深入研究,这对于快速高效地求解大区域复杂环境中的电波传播问题具有重要意义。本文主要研究工作如下：第一,基于抛物方程对森林、陡峭障碍物、粗糙海面等复杂地理环境的电磁建模方法展开了研究。根据森林环境的物理组成,应用两相混合物折射方法改进了森林的等效抛物方程模型,与文献实验结果的对比验证了该模型的有效性,在此基础上,讨论了森林的植物体积含量、重量含水量以及自由水盐度对电波传播的影响。为了计算陡峭障碍物的后向反射波,研究了双向抛物方程方法,并采用射线跟踪法对其正确性进行了验证,在此基础上,提出了双向抛物方程的并行方法,并探讨了其并行性能,结果表明,该并行方法大大提高了双向抛物方程对障碍物间多次反射波的求解速度；针对室内垂直墙面、家具等对电磁波后向反射较大的问题,提出了Pade型双向抛物方程模型,并应用该模型模拟了存在二栋双层建筑物时室内的电磁分布特性。另外,在考虑海浪阴影效应的情况下,构建了粗糙海面的等效抛物方程模型,实例仿真了电磁波在粗糙海面环境中的传播特性,结果表明,该模型能够体现海浪阴影效应以及不同海面风速对电波传播的影响。第二,提出了抛物方程的非均匀网格模型、多重非均匀网格模型以及亚网格模型等高效网格模型。首先,详细探讨了抛物方程水平网格步长的取值范围,并通过对传播空间的不同区域采用不同的网格划分,构建了抛物方程的非均匀网格模型,与双射线模型以及均匀细网格抛物方程的对比验证了该模型的正确性和高效性,同时,应用该模型模拟了三维复杂环境中的电磁覆盖特性,进一步证明了非均匀网格模型的优越性。在非均匀网格模型的基础上,结合坐标变换技术、网格插值技术等,提出了抛物方程的多重非均匀网格模型及其基于OpenMP的并行方法,并模拟了复杂环境中存在四个辐射源时的电磁分布特性,由结果可知,多重非均匀网格模型使得抛物方程能够对三维空间中的多辐射源电波传播问题进行求解,且其并行方法大大提高了多辐射源问题的求解速度。最后,针对大区域复杂环境中存在关键目标的电波传播问题,提出了抛物方程的亚网格模型,并详细阐述了亚网格模型的具体实现方案,通过与均匀细网格抛物方程进行对比,验证了亚网格模型的高效性,在此基础上,对大尺度海面环境中舰船区域的场分布进行了预测和分析。第三,为了提升抛物方程的求解速度,本文对抛物方程的高效数值解法展开了研究。基于镜像原理,提出了抛物方程SSFT解法的快速计算方法,与已有的奇偶分解法相比,抛物方程的求解速度得到了有效的提升。同时,研究了抛物方程的ADI解法,推导了自由空间以及边界上的场所满足的ADI差分格式,并基于OpenMP提出了抛物方程ADI解法的并行方法,通过对加速比、并行效率等的分析可知,并行方法大大加快了抛物方程ADI解法的计算速度。另外,为了高效求解大区域复杂环境中存在隧道等腔体环境的电波传播问题,提出了将抛物方程SSFT解法和ADI解法相结合的高效数值解法,并阐述了结合解法的具体实现方案,实例仿真表明,与ADI解法相比,结合解法极大地提高了抛物方程对该类问题的求解效率,在此基础上,采用该结合解法模拟和分析了大区域环境中隧道内部的电磁分布特性。第四,基于并行自适应结构网格应用支撑软件(JASMIN)框架研究了适用于高性能仿真平台的抛物方程并行计算方法,进一步提高了抛物方程的求解速度。通过将同一步进面划分成多个网格片,并分配到不同的处理器进行运算,实现了抛物方程FD解法的并行计算,与理论解的对比验证了并行方法及程序的正确性,同时通过实例分析了并行程序的并行性能,算例表明,抛物方程FD解法的求解效率得到了有效地提高,在此基础上,模拟了某一电信基站天线在包含9栋规则建筑物的城市小区环境中的电磁覆盖特性。针对大区域复杂环境中的电波传播问题,研究了抛物方程SSFT解法在JASMIN框架上的并行方法,并实现了相应的并行仿真程序,实例验证了并行方法及程序的正确性和高效性,同时,基于该并行程序,完成了典型综合三维大尺度场景的一体化建模,并对包含土壤、森林、大气波导等复杂环境因素的典型综合场景中的电波传播特性进行了预测和分析。
[Abstract]:In recent years, the research of wave propagation in complex electromagnetic environment has become a hot topic of attention of scholars at home and abroad. To build a computable model of complex environment elements and to realize rapid simulation and analysis of electromagnetic distribution characteristics in large area complex environment can provide the key to the practical application of wireless communication, electromagnetism monitoring, electronic countermeasures and so on. The numerical simulation technology and data support have very important military and civil value. Compared with the existing wave propagation model, the parabolic equation itself can reflect the refraction and diffraction effect of the wave propagation. It can fully consider the influence of irregular surface structure, non-uniform medium and other complex environment on the wave propagation, and its SSFT solution is used. The mesh size of the propagation direction is almost unrestricted by the wavelength, so it is very suitable for the prediction of the electromagnetic coverage in the complex environment of large regions. Based on the parabolic equation, the electromagnetic modeling method of the complex geographical environment such as the forest, the rough sea and the sea surface, the efficient mesh model of the parabolic equation and the efficient numerical solution are studied in this paper. It is of great significance to quickly and efficiently solve the problem of wave propagation in large area complex environment. The main research work of this paper is as follows: firstly, the electromagnetic modeling method of the complex geographical environment such as forest, steep obstacle and rough sea surface based on parabolic equation is studied. According to the physical composition of the forest environment, the two phase mixing is applied. The method of refraction improved the equivalent parabolic equation model of forest. Compared with the results of literature experiment, the validity of the model was verified. On this basis, the effect of plant volume content, weight water content and free water salinity on the wave propagation was discussed. In order to calculate the backward reflection wave of steep obstacles, the two-way throwing was studied. On the basis of this, a parallel method of bidirectional parabolic equation is proposed and its parallel performance is discussed. The results show that the parallel method greatly improves the speed of the two-way parabolic equation to solve multiple anti ejection waves between obstacles; for indoor vertical walls, furniture In the case of large backward reflection of electromagnetic wave, a Pade type bidirectional parabolic equation model is proposed. The model is used to simulate the indoor electromagnetic distribution characteristics in the presence of two double deck buildings. In addition, the equivalent parabolic equation model of the rough sea surface is constructed in the case of the sea wave shadow effect, and the electromagnetic wave is simulated in the rough. The propagation characteristics of the sea surface environment show that the model can reflect the effect of sea wave shadow and the influence of different sea surface wind speed on the wave propagation. Second, the non-uniform grid model of parabolic equation, the multi inhomogeneous mesh model and the subgrid model are proposed. First, the parabolic equation horizontal network is discussed in detail. A non uniform mesh model of parabolic equation is constructed by using different meshes of different regions in different regions of the space. The correctness and efficiency of the model are verified by the comparison with the double ray model and the uniform fine mesh parabolic equation. At the same time, the model is used to simulate the electricity in the three-dimensional complex environment. The characteristics of magnetic coverage further prove the superiority of the non-uniform grid model. On the basis of the non-uniform grid model, combining the coordinate transformation technique and the grid interpolation technique, the multiple non-uniform grid model of parabolic equation and the parallel method based on OpenMP are proposed, and the electromagnetic field of four radiation sources in the complex environment is modeled. The distribution characteristics can be seen from the results that the multiple non-uniform grid model makes the parabolic equation can solve the problem of the multi radiation source wave propagation in the three-dimensional space, and its parallel method greatly improves the speed of solving the problem of multiple sources. Finally, the problem of the wave propagation of the key targets in the complex environment of large regions is proposed. The subgrid model of parabolic equation and detailed implementation of submeshes model are described in detail. By comparing with the uniform fine mesh parabolic equation, the efficiency of the subgrid model is verified. On this basis, the field distribution of the ship area in the large scale sea surface environment is predicted and analyzed. Third, in order to improve the parabolic equation, In this paper, the efficient numerical solution of parabolic equation is studied in this paper. Based on the principle of mirror image, a fast calculation method of the parabolic equation SSFT solution is proposed. Compared with the existing odd even decomposition method, the solution speed of the parabolic equation is improved effectively. At the same time, the ADI solution of the parabolic equation is studied and the free space is derived and the free space is derived. The ADI difference scheme for the place on the boundary is satisfied and a parallel method of the parabolic equation ADI solution is proposed based on OpenMP. By the analysis of the acceleration ratio and the parallel efficiency, the parallel method greatly speeds up the calculation speed of the parabolic equation ADI solution. In addition, in order to efficiently solve the tunnel and other cavity environment in the large area complex environment, The problem of wave propagation is presented. A high efficient numerical solution is proposed, which combines the SSFT solution of parabolic equation and the ADI solution. The concrete realization scheme of the combined solution is expounded. The simulation shows that the solution efficiency of the parabolic equation is greatly improved by the method of solving the solution of the ADI solution. On this basis, the combination method is used to simulate the solution. The characteristics of the electromagnetic distribution inside the tunnel in large area are analyzed. Fourth, based on the parallel adaptive structure grid application support software (JASMIN) framework, the parallel calculation method of parabolic equation suitable for high performance simulation platform is studied, and the solution speed of the parabolic equation is further improved. By dividing the same step into multiple grids, the same step is further divided into multiple grids. The parallel computing of the parabolic equation FD solution is realized. The parallel method and the program are verified by comparison with the theoretical solution. At the same time, the parallel performance of the parallel program is analyzed by an example. The calculation example shows that the solution efficiency of the parabolic equation FD solution is effectively improved. On this basis, the calculation example shows that the solution efficiency of the parabolic equation method is improved effectively. The electromagnetic coverage characteristics of a telecommunication base station antenna in the urban residential area containing 9 regular buildings are simulated. The parallel method of the parabolic equation SSFT solution on the JASMIN frame is studied for the problem of the wave propagation in the complex environment of the large area. The corresponding simulation program is realized. The parallel method and the process are verified by an example. At the same time, based on the parallel program, the integrated modeling of typical integrated three-dimensional large scale scene is completed, and the wave propagation characteristics in the typical comprehensive scenes including soil, forest and atmospheric waveguide are predicted and analyzed.
【学位授予单位】：西南交通大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN011

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