对流层电磁波传播的抛物型方程法研究

发布时间：2019-05-12 17:28

【摘要】：对流层大气高度一般在17千米以内,大多数电磁波传播现象都在对流层中进行。对流层大气对电磁波传播的影响是多方面的,其中包括对电磁波的散射、折射、绕射等传播效应。对流层大气环境条件下所形成的波导是一种异常的大气结构,它的出现成为影响电磁波在对流层中传播的主要因素。这对舰船上以及海岸运作的雷达、通信设备等都有很大影响。我国四大领海以及东南沿海都处在对流层波导高发地区,因此开展对流层大气波导环境下电磁波传播特性研究具有实际的通信应用价值和国防意义。本文首先介绍蒸发波导、无基础层表面波导、有基础层表面波导、悬空波导、混合型波导等的形成条件、折射率剖面模型以及分布区域。其次,从赫姆霍兹波动方程开始,逐步推导出窄角抛物型方程。然后,使用分步傅里叶算法求解抛物型方程,分别得到标准大气以及上述五种波导结构下的电磁波传播损耗分布情况。文章还分析大气压强,温度,相对湿度对大气折射率梯度的影响以及海水介电常数,天线高度等对电磁波传播损耗的影响。结果表明,空气的相对湿度对大气折射指数影响最大;海水介电常数对电磁波传播损耗影响较小,可以忽略不计。文章对窄角抛物型方程推导以及求解过程中引入的主要误差进行分析,建立伪微分算子引入误差随传播仰角与折射指数变化的关系式,定量分析相对误差随上述因子变化的关系。进一步从分离指数项所带来误差入手,兼顾计算精度,给出了计算步长与频率的关系,由此可以在一定误差范围内,最大限度的增加计算步长,从而减少计算量,提高计算效率,这对嵌入抛物型方程算法系统的实时性具有重要意义。
[Abstract]:The tropospheric atmosphere is usually within 17 km, and most of the electromagnetic wave propagation takes place in the troposphere. The influence of tropospheric atmosphere on electromagnetic wave propagation is multifaceted, including scattering, refraction, diffraction and other propagation effects. The waveguide formed in the tropospheric atmosphere is an abnormal atmospheric structure, and its appearance becomes the main factor affecting the propagation of electromagnetic wave in the troposphere. This has a great impact on radar and communication equipment on ships and on the coast. The four major territorial seas and the southeast coast of China are all in the high incidence areas of tropospheric waveguides. Therefore, the study on the propagation characteristics of electromagnetic waves in tropospheric atmospheric waveguides has practical application value and national defense significance. In this paper, the formation conditions, refractive index profile model and distribution region of evaporation waveguide, non-base layer surface waveguide, suspended waveguide and hybrid waveguide are introduced. Secondly, starting with Hermholtz wave equation, the narrow angle parabolic equation is derived step by step. Then, the parabola equation is solved by using the split-step Fourier algorithm, and the electromagnetic wave propagation loss distribution in the standard atmosphere and the above five waveguide structures is obtained respectively. The effects of atmospheric pressure, temperature and relative humidity on the refractive index gradient of the atmosphere, and the effects of sea water dielectric constant and antenna height on the propagation loss of electromagnetic waves are also analyzed. The results show that the relative humidity of air has the greatest influence on the refractive index of the atmosphere, and the dielectric constant of seawater has little effect on the propagation loss of electromagnetic wave, which can be ignored. In this paper, the derivation of narrow angle parabola equation and the main errors introduced in the process of solving it are analyzed, and the relationship between the error introduced by pseudo differential operator and the variation of propagation elevation angle and refractive index is established. Quantitative analysis of the relationship between relative error and the above factors. Furthermore, starting with the error caused by the separation index term and taking into account the calculation accuracy, the relationship between the calculation step size and the frequency is given, so that the calculation step size can be increased to the greatest extent in a certain error range, thus reducing the amount of calculation. It is of great significance to improve the computational efficiency for the real-time performance of embedded parabola equation algorithm system.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN011.3

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