【作者】 李昊；

【导师】 于思源；

【作者基本信息】 哈尔滨工业大学 ， 光学工程（专业学位）， 2020， 硕士

【摘要】 卫星激光通信是使用光波段的卫星互联网电磁波代替传统微波的通信方式,具有通信容量大,安全性高,能量集中,天线体积小,发射功耗低的优点。在星地通信中,激光在大气内传输受到大气干扰,畸变和衰减现象较为严重,而将其应用于真空的星间通信,则更能发挥其优势。近年来,利用通信卫星组网,与地面基站互联,构建天地一体化的互联网系统成为世界各国重点的竞争项目。其中,搭载于卫星上的激光通信终端则是今后卫星通信载荷的重点研究方向。卫星激光通信因为其极小的通信视场,必须要求终端设备搭载高精度的瞄准捕获跟踪系统,在数千甚至数万公里的距离上实现通信链路的构建与维持。然后,将接受到的空间光导入光纤,进行解调,实现通信功能。其中,极为关键的一环是空间光到光纤的耦合过程。相对多模光纤,单模光纤在耦合时具有耦合效率高,滤波性能好等优点,是目前常用的耦合光纤。但由于单模光纤端面直径小,若要实现更高的耦合效率,就需要光束与光纤的高对准精度。这是卫星激光通信的关键技术之一。近年来,采用章动耦合的技术方法来实现空间光到单模光纤的高耦合效率,受到研究者广泛的关注。其核心思想是使用快速反射镜提供圆锥扫描,根据能量反馈判断光束与光纤相对偏差,并加以修正。这种结构具有体积小,结构简单,精度高等优点,在卫星激光通信领域具有很大的应用价值。基于上述优势,本文对章动耦合技术在卫星激光通信中的应用问题进行研究,主要包括以下工作:首先,分析传统PAT中精瞄镜的工作原理和章动耦合系统章动镜的工作原理。认为章动镜与传统PAT结构的精瞄镜可以组成双镜系统,相对传统的单精瞄镜系统跟踪精度更高,稳定性更强。建立光束在双镜系统中传播的数学模型,分析双镜系统工作在空间域和时间域的适配性原则。其次,对章动耦合系统工作的关键参数进行深入的研究,通过仿真分析和对照实验,得到章动半径和迭代步长两个工作参数与章动耦合系统工作快速性,稳定性,精确性三个定性关系。研究发现,设定固定的工作参数难以满足卫星激光通信的实际需求。设计了工作参数可调的自适应章动耦合系统。再次,提出基于前馈回路的控制结构,使用较为简单的线性拟合,B-P神经网络和阈值划分,解决了章动扫描迟滞畸变,章动半径自适应调节和迭代步长自适应调节三个问题。最后,通过仿真验证自适应系统工作可靠性,并给出改进意见。章动耦合技术应用于星间激光通信,可有效促进终端小型化的发展,具有广阔的应用前景。本文的研究成果对章动耦合技术在卫星激光通信的工程实践有重要意义。更多还原

【Abstract】 Satellite laser communication is a communication method that uses light-wave satellite Internet electromagnetic waves instead of traditional microwaves.It has the advantages of large communication capacity,high security,concentrated energy,small antenna size,and low transmission power consumption.In satellite-to-earth communication,laser transmission in the atmosphere is affected by atmospheric interference,and distortion and attenuation are more serious.However,applying it to vacuum inter-satellite communication can give full play to its advantages.In recent years,the use of communication satellite networking,interconnection with ground base stations,and the construction of a world-integrated Internet system have become key competitive projects in countries around the world.Among them,the laser communication terminal mounted on the satellite is the key research direction of the satellite communication load in the future.Because of its extremely small communication field of view,satellite laser communication must require terminal equipment to be equipped with a high-precision aiming,acquisition and tracking system to realize the construction and maintenance of communication links over thousands or even tens of thousands of kilometers.Then,the received space light is led into the optical fiber,demodulated,and the communication function is realized.Among them,the most critical part is the coupling process of space light to optical fiber.Compared with multimode fiber,single-mode fiber has the advantages of high coupling efficiency and good filtering performance during coupling.It is currently commonly used coupling fiber.However,due to the small diameter of the end face of the single-mode fiber,to achieve higher coupling efficiency,high alignment accuracy of the beam and the fiber is required.This is one of the key technologies of satellite laser communication.In recent years,the use of nutating coupling technology to achieve high coupling efficiency from space light to single-mode fiber has attracted wide attention from researchers.The core idea is to use a fast mirror to provide conical scanning,determine the relative deviation of the beam and the fiber based on energy feedback,and correct it.This structure has the advantages of small size,simple structure and high accuracy,and has great application value in the field of satellite laser communication.Based on the above advantages,this paper studies the application of nutating coupling technology in satellite laser communication,mainly including the following work:First,analyze the working principle of fine sighting mirror in traditional PAT and the working principle of nutating mirror of nutating coupling system.It is believed that the nutating mirror and the traditional PAT structured precision scope can form a double mirror system,which has higher tracking accuracy and stronger stability than the traditional single precision scope system.The mathematical model of the light beam propagating in the dual mirror system is established,and the adaptability principle of the dual mirror system working in the space and time domains is analyzed.Secondly,in-depth study of the key parameters of the nutation coupling system work,through simulation analysis and control experiments,get two working parameters of nutation radius and iteration step and nutation coupling system work fast,stable,accurate three A qualitative relationship.The study found that setting fixed operating parameters is difficult to meet the actual needs of satellite laser communications.An adaptive nutating coupling system with adjustable working parameters needs to be designed.Finally,simulation experiments verify the reliability of the adaptive system,and put forward suggestions for improvement.The application of nutating coupling technology to satellite laser communication can promote the development of miniaturization of terminals,and has great application value in the future.The research results of this paper are of great significance to the engineering practice of nutating coupling technology in satellite laser communication.更多还原