电波传播预测计算中的准三维抛物线方程法

发布时间：2018-05-24 03:52

本文选题：抛物线方程 + 电波传播　；参考：《南京邮电大学》2017年硕士论文

【摘要】：抛物方程(Parabolic Equation,PE)法的计算公式不仅可以描述不规则的地形结构、反映不均匀大气的媒质特性给电波传播带来的影响,并且该方法具有网格步长不依赖于波长的优点,计算效率高。本文在基于二维抛物线方程(Two-Dimensional Parabolic Equation,2DPE)的研究基础上提出了准三维抛物线方程(Quasi-Three-Dimensional Parabolic Equation,Quasi-3DPE)法来预测三维空间中电波传播特性。首先,介绍了直角坐标系下二维格式。通过四种方法对伪微分算子做近似处理,选择传播仰角达30°的Feit-Flect法近似处理的PE。对该算法在求解过程中需考虑的边界条件和初始条件给出了理论知识和计算的实例。其次,建立地形遮蔽模型来处理不规则地形的边界,在二维空间用分步傅里叶抛物线方程(Split-Step Fourier Transforms,SSFT)法计算常见地形上的电波传播问题,来预测远距离不规则地形的电波传播特性。计算结果正确地验证了电波在不规则地形上的传播特性。再次,在SSFT法预测二维空间电波传播特性的基础上提出了准三维法来预测三维空间电波传播特性。以圆锥几何体为例,该方法从视图的角度,将圆锥视为两个二维图形,即三角形(垂直面)和圆形(发射源高度处的水平面),然后分别计算这两个面上的电波传播特性。在同一传播距离、同一高度处将两个平面上的场值相加,再计算相应的传播因子,即为圆锥的准三维结果。最后,研究了电波在对流层的复杂大气结构条件下的电波传播特性。结合PE法,对复杂的大气结构进行处理,并通过实例的计算结果验证理论的正确性。
[Abstract]:The parabolic equation (PE) method can not only describe the irregular topographic structure, but also reflect the influence of the medium characteristics of the inhomogeneous atmosphere on the radio wave propagation, and the method has the advantage that the grid step size is independent of the wavelength, and the calculation efficiency is high. In this paper, a quasi-three-dimensional parabola equation Quasi-Three-Dimensional Parabolic EquationQuasi-3DPE-based method is proposed to predict the propagation characteristics of radio waves in three-dimensional space based on the study of Two-dimensional Parabolic Equationation2DPE. Firstly, the two-dimensional scheme in right-angle coordinate system is introduced. The pseudo-differential operator is approximated by four methods, and the Feit-Flect method with propagation elevation of 30 掳is selected. The theoretical knowledge and calculation examples are given for the boundary conditions and initial conditions that need to be considered in the solution of the algorithm. Secondly, the terrain shading model is established to deal with the boundary of irregular terrain, and the propagation of radio waves on common terrain is calculated by using the split-step Fourier parabola equation in two-dimensional space to predict the propagation characteristics of radio waves in long distance irregular terrain. The numerical results verify the propagation characteristics of radio waves on irregular terrain. Thirdly, based on the prediction of the propagation characteristics of two-dimensional space radio waves by SSFT method, a quasi-three-dimensional method is proposed to predict the propagation characteristics of three-dimensional space radio waves. Taking the conical geometry as an example, the cone is regarded as two two-dimensional figures from the view angle, that is, the triangle (vertical plane) and the circular (horizontal plane at the height of the source), and then the propagation characteristics of the radio waves on these two planes are calculated respectively. At the same propagation distance and at the same height, the field values on the two planes are added together, and the corresponding propagation factors are calculated, that is, the quasi-three-dimensional results of the cone. Finally, the propagation characteristics of radio waves under the complex atmospheric structure in the troposphere are studied. The complex atmospheric structure is treated with PE method, and the correctness of the theory is verified by the calculation results of an example.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN011

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