漏泄波导不连续处对辐射特性的影响及其改进方法

发布时间：2018-04-09 12:11

本文选题：漏泄矩形波导　切入点：不连续结构　出处：《北京交通大学》2017年硕士论文

【摘要】：随着通信技术的发展和应用需求的不断提高,对受限空间和狭长区域的无线通信质量也提出了更高的要求,如地铁、隧道、矿井、以及高铁和轻轨沿线等环境都要求提供稳定可靠的无线通信,因此对这类场合中的电波覆盖也相应提出了更高的要求。然而,由于受限空间中电波多径衰落影响大,狭长空间中电波容易干扰周边或受周边干扰,使用分立式天线系统通常无法达到满意效果,因此在这类受限空间中通常采用漏泄同轴电缆或者漏泄波导来实现电波的高效覆盖。然而,漏泄波导的实际应用中也存在多种影响其辐射特性的因素,如各种不连续结构或环境都会影响到其周围电场的分布,因此需要对各种不连续情况可能带来的影响进行研究。本文针对这类应用需求,重点研究波导之间法兰盘、环境积雪以及中继放大器前后功率差对漏泄波导产生的电波覆盖的影响,为受限及狭长空间中基于漏泄波导的电波覆盖系统的设计和评估提供重要依据。本文的主要工作和研究成果如下:1.研究了漏泄波导通过法兰盘连接时造成的结构上的这种不连续及其周围电场分布的影响,同时还研究了法兰盘位置偏离左右缝隙对称中心时,对近场分布的均匀性造成的影响。针对这类情况提出了改善措施,即通过降低法兰盘的高度或者将法兰盘上部以不同的角度削掉来减少法兰盘对电磁波的遮挡,从而提高电场分布的稳定性。2.通过经验公式计算出含水量不同的雪在2.4GHz时的介电参数,研究了积雪在漏泄波导上以不连续状态随机分布时,漏泄波导周围场分布受到的影响,并且分别从场沿波导的周向分布和轴向分布两种情况深入分析了雪对场分布的影响机理。在分析研究基础上,提出了减弱积雪影响的改善措施,即在积雪与波导之间放置介质层,以减弱雪对能量的直接吸收。3.根据磁流源等效原理和阵列天线阵元与阵因子的关系,推导出了适用于漏泄波导近场分布的理论计算公式,研究了当漏泄波导中继放大器功率突然放大不同倍数(100倍、500倍、1000倍)时对中继器所在区域耦合损耗的影响,并从理论上分析了这种现象出现的原因。据此提出了改进措施,即采用涂覆吸波材料的方法,对功率较强一边在一定距离内的能量进行适当抑制,从而实现了中继器前后耦合损耗的平稳过渡。
[Abstract]:With the development of communication technology and the continuous improvement of application demand, the wireless communication quality of restricted space and narrow area has also put forward higher requirements, such as subway, tunnel, mine, etc.As well as high-speed rail and light rail along the environment are required to provide stable and reliable wireless communications, so the radio coverage in such cases is also put forward higher requirements.However, due to the large influence of multipath fading in confined space, radio waves in long and narrow space are apt to interfere with or be affected by peripheral interference, so it is usually not possible to achieve satisfactory results by using discrete antenna systems.Therefore, leakage coaxial cables or leaky waveguides are usually used to cover radio waves efficiently in this kind of confined space.However, in the practical application of leaky waveguides, there are many factors that affect their radiation characteristics, such as various discontinuous structures or environments that affect the distribution of electric fields around them.Therefore, it is necessary to study the possible effects of various discontinuities.In this paper, the effects of flange between waveguides, environment snow and power difference before and after relay amplifier on the radio wave coverage of leaky waveguides are studied in order to meet the needs of this kind of applications.It provides an important basis for the design and evaluation of radio coverage systems based on leaky waveguides in restricted and narrow space.The main work and research results of this paper are as follows: 1.The discontinuity of the structure and the influence of the electric field distribution around the leaky waveguide when connected through the flange are studied. The influence of the flange position deviation from the left and right slot on the distribution uniformity of the near field is also studied.The improvement measures are put forward, that is, by reducing the height of the flange or cutting off the upper flange at different angles to reduce the shielding of electromagnetic wave by the flange, thus improving the stability of electric field distribution.The dielectric parameters of snow with different water content in 2.4GHz are calculated by empirical formula. The effect of random distribution of snow on leakage waveguide in discontinuous state is studied.The influence mechanism of snow on the field distribution is analyzed from the circumferential distribution and axial distribution of the field along the waveguide.On the basis of analysis and research, the improvement measures of reducing the influence of snow cover are put forward, that is, the dielectric layer is placed between the snow and the waveguide to weaken the direct absorption of energy by snow.Based on the equivalent principle of magnetic current source and the relationship between array antenna elements and array factors, a theoretical calculation formula suitable for the near-field distribution of leaky waveguide is derived.The influence of the leakage waveguide relay amplifier on the coupling loss in the repeater region is studied when the power of the relay amplifier suddenly amplifies by 100 times or 500 times (1 000 times), and the reason of this phenomenon is analyzed theoretically.Based on this, the improvement measures are put forward, that is, the energy of the stronger side within a certain distance can be restrained properly by using the method of coating the absorbing material, so as to realize the smooth transition of the coupling loss before and after the repeater.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN814

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