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Radiowave propagation studies in tunnels using ADI-PE technique .

机译：利用ADI-PE技术研究隧道中的无线电波传播。

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Due to the growth of mobile communication systems, there is an increasing demand for numerical techniques capable of predicting signal strength in subway, railway and underground road tunnels. In this dissertation, we study radio wave propagation in tunnels using the alternating direction implicit (ADI) method and the parabolic equation (PE). The PE models waves that travel predominantly in one direction and corresponds to the low order modes in real tunnels. It has been well documented that tunnels are characterized by these low order modes at large distances. The Crank-Nicolson method is the traditional finite difference method used to solve the PE. However, one of the limitations of the Crank-Nicolson method is that it involves the inversion of large matrices that result from discretizing the tunnel cross-section. We explore the use of the ADI scheme as a computationally efficient alternative to the Crank Nicolson method. In the ADI scheme, smaller matrices are used by solving the fields in the transverse plane line by line along one dimension in one half step, and then line by line along the other dimension in the next half step. However, one of the trade-offs is that the ordering of the line by line decomposition becomes important when dealing with circular cross-sections. Also, the boundary conditions at the half step plane are not necessarily the same as the physical boundary conditions and this can effect the overall accuracy of the sheme. We formulate the ADI scheme for use in tunnels with rectangular, circular and arched cross-sections with lossy walls. We also study various realistic tunnel variations, such as curved, branched and rough-walled tunnels. A full vector-PE is used and the wall loss is characterized by the impedance boundary condition. To validate the ADI-PE, we show simulation results for tunnel test cases with known analytical solutions. Furthermore, the ADI-PE is used to simulate real tunnels in order to compare with experimental data. There is good agreement with the ADI-PE and theoretical tunnels where the initial field and wall electrical parameters are completely known. Disagreement with the PE solution is observed when compared to experimental data for tunnels whose electrical parameters and initial fields are not completely defined. The ADI-PE models the electric fields most accurately in real tunnels at large distances and at high frequencies.
机译：由于移动通信系统的发展，对能够预测地铁，铁路和地下公路隧道信号强度的数值技术的需求日益增长。本文采用交替方向隐式（ADI）方法和抛物线方程（PE）研究隧道中的无线电波传播。 PE模拟的波主要沿一个方向传播，并与实际隧道中的低阶模式相对应。已有大量文献证明，隧道的特征是在远距离处具有这些低阶模式。 Crank-Nicolson方法是用于求解PE的传统有限差分方法。但是，Crank-Nicolson方法的局限性之一在于，它涉及将隧道横截面离散化而导致的大矩阵反演。我们探索使用ADI方案作为Crank Nicolson方法的计算有效替代方案。在ADI方案中，使用较小的矩阵，方法是在一个半步中沿一个维度逐行求解横向平面中的场，然后在下一个半步中沿另一个维度逐行求解。但是，权衡之一是在处理圆形横截面时，逐行分解的顺序变得很重要。同样，半阶梯平面上的边界条件不必与物理边界条件相同，并且这可能会影响sheme的整体精度。我们制定了ADI方案，以用于具有矩形，圆形和拱形横截面且有损壁的隧道。我们还研究了各种现实的隧道变化，例如弯曲的，分支的和粗糙的隧道。使用全矢量PE，并且壁损耗由阻抗边界条件表征。为了验证ADI-PE，我们使用已知的分析解决方案显示了隧道测试案例的仿真结果。此外，ADI-PE用于模拟真实隧道，以便与实验数据进行比较。与ADI-PE和理论隧道有着良好的一致性，在这些隧道中，初始场和壁电参数是完全已知的。与未完全定义电参数和初始场的隧道的实验数据相比，发现与PE解决方案存在分歧。 ADI-PE最能精确模拟远距离和高频真实隧道中的电场。

著录项

  • 作者

    Martelly, Richard.;

  • 作者单位

    University of Massachusetts Amherst.;

  • 授予单位 University of Massachusetts Amherst.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 133 p.
  • 总页数 133
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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