FDTD和PSTD的混合算法在低频地波传播中的应用

发布时间：2018-04-08 21:59

本文选题：低频地波　切入点：时域有限差分方法　出处：《西安理工大学》2017年硕士论文

【摘要】：低频地波信号因其传输稳定、衰减小、绕射能力强、传播距离远等特点而被广泛应用于远距离导航、授时和通信等方面。然而,受到传播路径地形起伏变化、地物非均匀分布、大气环境空时变化等因素的影响,使得实际低频地波信号的传播速度、方向和相位等有别于真空中的情况。研究复杂环境下低频地波传播特性的高精度快速预测方法是提高低频地波导航授时系统精度的关键。现有的时域有限差分方法(Finite-Difference Time-Domain Method,FDTD)能够模拟实际信号的传播过程,但长距离应用时存在数值色散误差大、计算机消耗过大等问题;时域伪谱方法(Pseudo-spectral Time-Domain Method,PSTD)能够处理电大尺寸电磁计算问题,但对复杂结构及媒质突变问题处理困难。针对上述问题,本文提出一种“FDTD+PSTD”频域空域结合的数值预测方法,通过将传播区域进行划分,结合FDTD方法与PSTD方法各自优势,实现低频地波传播性能的高精度、快速预测。具体研究内容包括:首先,从FDTD和PSTD的基本理论出发,推导了两种算法的实现过程并进行了仿真验证,对比分析了各算法的特点;其次,针对低频地波传播问题,分析了 FDTD方法与PSTD方法应用于该问题的可行性与存在的问题;再次,基于上述分析结果,提出“FDTD+PSTD”频域空域结合的数值预测方法,从区域划分、结合模式、场量迭代方式、网格剖分、分界面处场量传递等方面进行系统研究,仿真验证了不同地面模型下混合算法的有效性;最后,将混合方法进一步应用于天线近场效应研究,仿真分析了地面条件对天线辐射特性的影响。仿真结果表明:在保证一定的预测精度下,计算相同区域时混合算法比FDTD在计算速度上快3～4倍,而在内存占用上则少1～2倍;同时,近场区地面条件对天线的辐射特性及相位中心将产生较大的影响。本文研究成果将为长距离、大面积低频地波传播性能的高精度预测及其工程实现提供技术支撑。
[Abstract]:Low frequency ground wave signal is widely used in long range navigation, timing and communication because of its characteristics of stable transmission, low attenuation, strong diffraction ability and long propagation distance.However, due to the influence of the topographic fluctuation of the propagation path, the uneven distribution of ground objects and the space-time variation of the atmospheric environment, the propagation speed, direction and phase of the actual low-frequency ground wave signal are different from those in the vacuum.It is the key to improve the accuracy of low-frequency ground-wave navigation and timing system to study the high-precision and fast prediction method of low-frequency ground wave propagation in complex environment.The existing Finite-Difference Time-Domain method (FDTD) can simulate the actual signal propagation process, but the numerical dispersion error is large and the computer consumption is too large.Pseudo-spectral Time-Domain method (PSTD) can deal with electrically large size electromagnetic computation problems, but it is difficult to deal with the problem of complex structure and medium mutation.In order to solve the above problems, this paper presents a numerical prediction method combining "FDTD PSTD" in frequency domain. By dividing the propagation region and combining the advantages of FDTD method and PSTD method, the high precision and fast prediction of low-frequency ground wave propagation performance can be realized.The specific research contents are as follows: firstly, from the basic theory of FDTD and PSTD, the realization process of the two algorithms is deduced and verified by simulation, and the characteristics of each algorithm are compared and analyzed. Secondly, aiming at the problem of low-frequency ground wave propagation,The feasibility and existing problems of applying FDTD method and PSTD method to this problem are analyzed. Thirdly, based on the above analysis results, a numerical prediction method combining "FDTD PSTD" in frequency domain is proposed, which can be divided into regions and combined modes.The simulation results show that the hybrid algorithm is effective under different ground models. Finally, the hybrid method is applied to the near field effect of antenna.The effects of ground conditions on antenna radiation characteristics are simulated and analyzed.The simulation results show that the hybrid algorithm is 3 ~ 4 times faster than FDTD in computing the same area and 1 / 2 times less in memory than FDTD under certain prediction accuracy.The near field ground condition will have a great influence on the radiation characteristics and phase center of the antenna.The research results in this paper will provide technical support for the high precision prediction and engineering realization of the low frequency ground wave propagation performance in long distance and large area.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN011

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