【作者】 宋义伟；

【导师】 谭立英；

【作者基本信息】 哈尔滨工业大学 ， 物理电子学， 2011， 博士

【摘要】 卫星激光通信技术由于其传输数据率高、保密性好、体积小而且重量轻,受到世界各国越来越多的关注。美国、欧洲和日本等国已相继实现了卫星激光通信技术工程化,并成功进行了星地和星间激光通信实验,其他国家也在大力发展卫星激光通信技术。卫星激光通信由于传输距离远,激光光束束散角小,使得瞄准、捕获和跟踪(PAT)技术成为链路建立和保持的关键技术。卫星激光通信系统主要包括光信号收发子系统、跟瞄子系统以及通信子系统。跟瞄子系统由粗瞄机构和精瞄机构两部分构成,粗瞄机构的结构形式一般分为潜望式结构和经纬仪式结构。对于潜望式结构,需要在粗瞄机构上安装两块45度放置的反射镜,粗瞄机构及其45度反射镜安装在卫星舱外用以实现光信号的收发和跟瞄。这样,45度反射镜就暴露在空间热环境中,形成具有一定梯度的温度场并使反射镜产生热形变,对卫星激光通信系统的跟瞄性能和通信性能产生一定的影响。因此,研究潜望式卫星光通信终端45度反射镜空间温度场分布,及其对激光通信系统跟瞄性能和通信性能的影响具有重要意义。本文首先阐述了世界各国卫星激光通信技术的发展情况,介绍了空间热环境对激光通信终端性能影响的国内外研究现状。针对潜望式卫星光通信终端,对45度反射镜空间温度场分布、及其对系统跟瞄性能和通信性能的影响进行了深入系统的研究,具体工作如下:本文建立了潜望式卫星光通信终端45度反射镜上的温度分布对系统跟瞄性能影响的理论模型,分析了45度反射镜上的温度分布对发射端瞄准性能和接收端跟踪性能的影响,得到了跟瞄误差和接收平面上的光强分布随45度反射镜上温度梯度和均匀温差的变化规律。研究了存在卫星平台振动环境下,45度反射镜上的温度分布对系统通信性能的影响。在不考虑噪声和考虑噪声两种条件下,建立了45度反射镜上的温度分布对通信误码率影响的理论模型,给出了通信误码率随45度反射镜上的温度梯度和均匀温差的变化规律。分析过程中,通过采用不同的通信光波长、振动角偏差和光束切断比,在45度反射镜上存在温度分布变化情况下,得到了通信误码率随各个参量的变化关系。在45度反射镜上存在温度梯度和均匀温差分布情况下,对比分析了背部框架固定方式与传统的圆周压圈固定方式对系统跟瞄性能和通信性能的影响。分析结果表明,相比于圆周压圈固定方式,背部框架固定方式更加适合于45度反射镜的固定。建立了潜望式卫星光通信终端在轨运行过程中,45度反射镜在轨温度场分布的理论模型,给出了典型的低轨和高轨上45度反射镜的在轨温度场变化规律。对比分析了四种不同材料的45度反射镜的在轨温度场分布及其变化规律,结果表明SiC反射镜具有最小的温度变化范围和温度不均匀性,是45度反射镜的可选材料。本文对背部固定方式下SiC材料反射镜的在轨温度场分布情况进行了实验模拟,通过对实验结果与仿真结果的对比分析,验证了采用仿真方法进行45度反射镜在轨温度场计算的正确性。最后研究了45度反射镜在轨温度场分布对系统跟瞄性能和通信性能的影响,得到了潜望式卫星光通信终端在轨运行过程中,跟瞄误差、接收平面光强分布和通信误码率随时间的变化规律。该项研究工作为潜望式卫星光通信终端45度反射镜温控指标的设计、反射镜材料的选择及固定方式的选择提供了理论依据,为终端在轨性能指标优化设计提供重要的参考依据,也为实际应用中终端在轨性能测试结果的分析提供了理论依据和参考,因此,该项研究具有重要意义。更多还原

【Abstract】 More and more attentions globally are paid to satellite laser communication, a new communication technique which has many advantages including higher data rate, low probability of intercept, less volume, less mass and so on. Among others, America, Europe and Japan have come to the engineering reality of satellite laser communications, succeeding in the satellite-to-earth and intersatellite laser communication experiments, and investing more in this grow up field.Because of far communication distance and ultra-small divergence of laser beam, the pointing, acquisition and tracking (PAT) become the key technologies in founding and keeping the satellite laser communication links. Generally, a satellite laser communication system mainly includes transmitter-receiver, pointing-tracking, and communication subsystems. The pointing-tracking subsystem consists of coarse pointer and fine pointer mechanisms. A coarse pointer is usually of a periscope structure or a theodolite structure. For the periscope structure, two 45-degree placed reflectors should be set on the coarse pointer. The coarse pointer and 45-degree reflectors must be fixed outside the satellite to transmit-receive and point-track optical signal. Therefore, this makes the 45-degree reflectors on coarse pointing structure exposed to the space thermal environment. Apparently, the temperature field with temperature gradient will be formed on the reflectors and this in turn results in the deformation of the reflectors. Consequently, performance of the pointing, tracking and communication subsystems of satellite laser communication system will be affected. Therefore, it is of significance to study the temperature field distribution on 45-degree reflectors in periscopic satellite laser terminals in space and the induced influence to laser communications’performance.This dissertation is organized as follows, first, a brief review of the development status of satellite laser communications globally is given in this dissertation. We give the introduction of the research on the effect on the performance of laser communication terminals due to thermal environment in space. For periscopic satellite laser communication terminals, in-depth and systematic research is made on temperature field distribution on 45-degree reflectors in space, and its influence on pointing-tracking performance and communication performance in laser communication systems. The specific works are list as following.In this dissertation, we established the theoretical model of the effects on pointing and tracking performance due to temperature distribution on 45-degree reflectors in periscopic satellite optical terminals. Effects on pointing performance at emitter and tracking performance at receiver are analyzed respectively due to temperature distribution on reflectors. We got the variation of pointing error, tracking error and intensity distribution on receiving plane with the temperature gradient and uniform temperature difference on 45-degree reflectors.Effects on communication performance due to temperature distribution on 45-degree reflectors are studied when vibration of satellite platform exists. The theoretical model of effects on BER due to temperature distribution on reflectors is established in this dissertation with and without noise. The variation of BER with temperature gradient and uniform temperature difference on reflectors is given. Through the analysis of effects on BER because of different wavelength, vibration angle deviation and beam truncation, we got the relationship between BER and these parameters.When there is temperature gradient and uniform temperature difference on 45-degree reflectors, the effects on pointing-tracking and communication performance are compared to the back-fixing using blank and traditional around-fixing using press-board. It is found that the back-fixing method using blank is more suitable to be used to fix 45-degree reflectors comparing to around-fixing method using press-board.The theoretical model of temperature field distribution on 45-degree reflectors in periscopic satellite optical terminals on orbit is established in this dissertation. The variation regularity of temperature field on 45-degree reflectors is given most typical low earth orbit and high earth orbit. The temperature distribution on reflectors of the four different materials is given on orbit. It is found that the reflector with SiC material has the minimum temperature changing range and the minimum temperature difference on orbit. And SiC material is more suitable to be used to make 45-degree reflectors in periscopic satellite optical terminals. The experiment of temperature field distribution on orbit of SiC material reflectors under back-fixing method is given. Through the comparation of the experiment and simulation results, the simulation method computing 45-degree reflectors’temperature field on orbit is validated to be right.Finally, the influence of temperature field on 45-degree reflectors on orbit on pointing, tracking and communication performance in periscopic satellite optical terminals is studied at the end of this dissertation. The variation regularity of pointing error, tracking error, intensity distribution on receiving plane and communication BER performance with time on orbit is given.In summary, the study of this dissertation provides theoretical support guidance in the aim design of thermal control of 45-degree reflectors in periscopic satellite optical terminals, and also in choosing materials and fixing methods for 45-degree reflectors. This can serve as good reference in optimizing design of performance parameter of terminals on orbit in space, as well as theoretical support and reference in testing and evaluating of performance test of periscopic satellite optical terminals on orbit in practical application. Therefore, these research and works are of great significance.更多还原