基于带电颗粒电磁波散射特性的相关研究

发布时间：2018-07-12 17:26

本文选题：带电颗粒Mie理论 + 散射相位函数　；参考：《兰州大学》2017年硕士论文

【摘要】：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。
[Abstract]:The rapid development of electromagnetic wave technology has been widely used in many fields, such as the transmission of electromagnetic wave in extreme environment (dust storm, haze and so on) and the monitoring of particle composition in atmosphere by electromagnetic wave technology. The properties of particles, such as charged particles, will have an effect on electromagnetic wave scattering, which will directly affect the signal transmission quality and monitoring results. Therefore, based on the scattering property of charged particle electromagnetic wave, the phase function of charged particle electromagnetic wave scattering, the properties of charged particle, including the band electric quantity and relative refractive index, and the radar atmospheric detection ability in charged particle system are studied in this thesis. The main work is as follows: based on the Mie scattering principle of charged particles, first of all, the scattering phase function of spherical charged particles is derived, and the difference between the scattering phase functions of charged particles and that of uncharged particles is obtained. The scattering phase function changes with the changes of surface conductivity, particle size parameters, incident frequency of electromagnetic wave and relative refractive index of particles, and increases the value of backscattering phase function after charged particles. For the case of fixed incident wave frequency and relative refractive index of particles, the variation of scattering phase function with particle surface conductivity has a critical surface conductivity under each particle size parameter. If the surface conductivity of particles is larger than this critical value, the dependence of scattering phase function on the surface conductivity of particles will be weakened, indicating that charged particles play a leading role. Secondly, The amplitude ratio and phase difference of electromagnetic wave scattering electric field in the direction of transverse component are derived. It is found that there is a good linear correlation between the amplitude ratio and phase difference of scattering electric field perpendicular to the incident wave and the amount of electrical energy on the surface of the particle. According to the linear correlation relationship, the slope of linear correlation is different with different influence parameters. Based on this relationship, a method for retrieving the energy of particle band and the relative refractive index of particles based on electromagnetic wave scattering signal is proposed. The extinction coefficient and backscattering coefficient of charged particle system are analyzed, and the radar ratio of radar irradiating on particle system is derived. It is found that there is a significant difference in the ability of different band radar to detect charged particle system, especially for dust particle system, the influence of charged sand particle on lidar detection is the least, compared with other band radar. Lidar has obvious advantages in detecting charged sand particle system. In addition, the detection ability of lidar will change with the change of the electric quantity of particle surface and the properties of particle.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O441.4

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