【作者】 冯立坤；

【导师】 王春晖；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2008， 硕士

【摘要】 激光相干测风雷达是目前大气风场测量的主要手段之一,以其高信噪比和接收带宽短等优点受到各国科学家的重视,激光测风雷达对于数值天气预报、大气动力学研究、航空安全预警和国防应用都有重要的意义和良好的应用前景。本文针对评价相干激光雷达系统重要参数之一的天线效率进行了分析,给出了相干激光雷达光学天线的设计依据,并对设计好的天线系统的天线效率做出了评估。主要内容如下:(1)给出了相干激光雷达系统的天线效率与外差效率的关系,讨论了外差效率的最佳匹配条件,并针对不同的收发结构形式给出了外差效率的简化表达式。(2)讨论了发射和接收光束的截断比对接收外差信号的影响,针对在接收面处混频和探测面处混频的两种接收方式,在不同的光场模型下分别做出了讨论,通过仿真计算得出不同的截断比对外差接收信号的影响,得到收发合置系统下的最佳截断,为相干激光雷达系统的光学天线设计提供了可靠的依据。(3)设计一套收发合置的相干激光雷达光学天线系统,主天线采用离轴卡塞格伦的双发射式结构。预扩束系统采用的是无实焦点的伽利略式的透射式望远镜系统。要求按照外差接收系统的相干接收条件来设计光学天线系统,要求设计达到的波前差小于λ/20的衍射极限系统。(4)利用天线设计结果及相应的系统结构参数,针对不同的工作距离,不同的大气条件仿真出收发合置结构下系统的天线效率。更多还原

【Abstract】 Coherent wind lidar is one of the major means which measures the atmospheric wind fields, with a high signal-to-noise ratio and receive short bandwidth by the advantages, many scientists from various countries attention it. Lidar has important significance and a good prospect in many fields, such as numerical weather prediction, atmospheric dynamics, aviation safety warning and defense applications. Based on the need of coherent wind lidar system weak signal detection, coherent wind lidar systems acoustic frequency shifter technical problems were studied,Antenna efficiency, which is one of most important parameter of the coherent wind lidar system, is analyzed. The design process is presented and the evaluation about antenna efficiency of an antenna system is investigated. It includes:(1) Relationship between antenna efficiency and heterodyne efficiency is proposed. Optimum match condition is given out, and mathematical expression of heterodyne efficiency is showed for different transceiver systems.(2) A discussion about different truncation ratio of transmitter to receiver diameter is presented in different optical signal model for the two different mixing configurations on the received plane. It is calculated that different truncation ratios affect the heterodyne signal by numerical simulation, especially the optimum truncation ratio in mono-static system, which is helpful for design of optical antenna of coherent lidar, and heterodyne efficiency is enhanced by choosing reasonable truncation ratio.(3) A mono-static optical antenna has been designed for the coherent lidar system, and primary antenna is an unfocused-Cassegrain bi-transmitted configuration. The beam pre-expand system is an afocal Galileo-transmission telescope system. According to coherent condition for the heterodyne system, wave-front aberration need be less thanλ/20 for a diffraction-limited system.(4) For different operation ranges and atmospheric condition, antenna efficiency is investigated and presented for mono-static configuration by using the simulation result for design and system configuration parameters.更多还原