兰州大学机构库 >土木工程与力学学院
基于带电颗粒电磁波散射特性的相关研究
Alternative TitleA Study Related to Electromagnetic Wave Scattering by Charged Particles
秦建虎
Thesis Advisor谢莉
2017-04-28
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword带电颗粒Mie理论 散射相位函数 颗粒带电量 雷达探测
Abstract

快速发展的电磁波技术在很多领域得到广泛的应用,例如极端环境(沙尘暴、雾霾等天气)中电磁波的传输以及利用电磁波技术对大气中颗粒成分的监测等。颗粒的属性如颗粒带电会对电磁波散射产生影响,直接影响其信号传输质量以及监测结果。因此,本硕士论文基于带电颗粒电磁波的散射性质,对带电颗粒电磁波散射相位函数、带电颗粒属性包括带电量和相对折射率以及带电颗粒系统中雷达大气探测能力展开研究,主要工作如下:

基于带电颗粒的Mie散射原理,首先,推导了球形带电颗粒的散射相位函数,得到带电颗粒的散射相位函数与不带电颗粒的散射相位函数之间存在显著差异,主要体现在散射相位函数随着颗粒表面电导率、颗粒尺度参数、电磁波入射频率以及颗粒相对折射率的变化而发生改变,颗粒带电后会增加后向散射相位函数的值,对固定入射波频率和颗粒相对折射率的情形下,散射相位函数随颗粒表面电导率的变化在每一种颗粒尺度参数下都存在一个临界表面电导率,如果颗粒表面电导率大于此临界值,散射相位函数对颗粒表面电导率的依赖性将会减弱,表明颗粒表面带电起到了主导作用;其次,导出了在横向分量方向上电磁波散射电场的振幅比及相位差,分析发现在垂直于入射波的方向上散射电场振幅比和相位差与颗粒表面带电量的大小之间存在非常好的线性相关关系,此线性相关关系会随着不同的影响参数而表现在线性相关的斜率不同,根据此关系提出了基于电磁波散射信号反演颗粒带电量和颗粒相对折射率的方法;最后,分析了带电颗粒系统的消光系数和后向散射系数,导出雷达照射在颗粒系统上的雷达比率,通过对雷达比率的分析,发现不同波段雷达对探测带电颗粒系统的能力之间存在着显著的差异,特别地对沙尘颗粒系统,沙粒带电对激光波段雷达探测的影响最小,相比较于其他波段雷达,激光波段雷达在探测带电沙粒系统具有明显的优势,另外,雷达探测能力的大小也会随着颗粒表面带电量大小及颗粒属性的变化而出现变化。

Other Abstract

Electromagnetic (EM) wave technology is rapidly developed to be widely used in many fields. For example, EM wave must be propagating in extreme environments such as dust storms, fog and haze weather and EM wave technology is also used to monitor the composition of atmosphere particles in these weather. The properties of particles, such as the charge of particles, can affect the scattering of EM waves, and thus affect the quality of signal transmission and monitoring results. In this thesis, based on the EM scattering properties of charged particle, the scattering phase function of a charged particle was investigated, and the properties and charge of charged particle were reversely calculated and the effect of charged particle systems on the capability of radar atmospheric detection was studied. The main work includes as following:

First, we deduced out the scattering phase function (SPF) of a charged spherical particle, which is significantly different from the SPF of uncharged spherical sphere. The difference between the SPF of a charged spherical particle and the SPF of an uncharged spherical sphere is related to the surface conductivity, particle size parameter, the frequency of the EM waves and the refractive index of the particle. The surface charges carried by the particle makes the backward scattering of EM waves increasing. Given the EM wave frequency and the refractive index, there is a threshold of surface conductivity for each particle size number, beyond which SPF mainly depend on the surface conductivity. Second, we derived the amplitude ratio and phase difference of the transverse components of the scattered electric field. We found that in the direction perpendicular to the incident direction of the EM waves, the amplitude ratio and phase difference are linearly dependent on the surface potential. For particulate systems, the surface electric potential and relative refractive index of a charged particle are mathematically expressed by amplitude ratio and phase difference, and a method to estimate the surface potential and the relative refractive index was proposed based on the observation of EM wave’s signals. Finally, we investigated the radar ratio of charged particles system combining the extinction coefficient and backscattering coefficient of charged particle. The results show that there are significant differences in the ability of detecting the charged particle system with different bands radar. For the sand and dust particles system, the effect of charged particles on laser band radar detection is minimal. Compared with other band radars, the advantage of laser-band radar measurement of charged particle system is significant. In addition, radar detection capability will also depend on the charge of particles and particle properties.

URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226272
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
秦建虎. 基于带电颗粒电磁波散射特性的相关研究[D]. 兰州. 兰州大学,2017.
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