光无线通信系统中移动终端APT技术研究

【作者】 张尚剑；

【导师】 刘永智；

【作者基本信息】 电子科技大学 ， 光学工程， 2003， 硕士

【摘要】 本文在介绍光无线通信系统基本原理和组成的基础上，对其APT（Acquisition，Pointing，Tracking）子系统结构进行了理论设计，并对APT技术算法进行了深入研究。通过对通信系统工作波长选择、光学天线选择等阐述，选择了1550 nm作为系统工作波长、卡塞格伦（Cassegrain）收发合一天线作为系统光学天线；通过对APT子系统功率测算、束散角和瞄准误差、误差提取信号等的讨论，给出了APT子系统结构和理论设计指标，并将其与现有的光无线通信系统进行比较，说明该设计方案是可行的。由于在拟用环境中对系统机动性要求较高，因此本文着重对APT技术中的超前校正进行了分析。为了能够较好的给出运动终端的超前校正值，必须了解终端的运动特性，本文对海上舰船运动进行了数值仿真，给出了二级海浪下18kn速度航行的运动时间历程。并在此基础上讨论了滑动窗多项式拟合预测算法（SPFM），对该算法与普通的多项式外推预测进行了比较，对模型进行了适应性修正，并对算法的参数：系统采样频率、滑动窗大小、拟合多项式指数进行了优化。最后通过计算机仿真说明在预测海上舰船运动时要求采样频率大于4 Hz，滑动窗大小取10～20，多项式为3或4阶时计算量和误差较小，预测效果较好。当舰船速度从0到30kn节之间变化时，发现预测误差有所增大，当到一定速度之后其预测误差保持不变。更多还原

【Abstract】 Based on the basic theories and composition of optical wireless commu-nication system, the structure design of its APT (Acquisition, Pointing, Tracking) sub-system and further research on APT technical algorithm have been discussed theoretically in this thesis. 1550nm is chosen as the work wavelength, Cassegrain transmitting-receiving antenna as the optical antenna of the system through the elucidation of how to choose the work wavelength and optical antenna of comm-unication system. The structure and theoretical design parameter of APT sub-system have been presented through the discussion of the optical signal power estimation of APT sub-system, beam divergence angle, pointing error, and error signal extraction. Compared with existed optical wireless communication system, the design scheme proves applicable.Because of high requirement of maneuverability for the system, the beforehand emendation in APT technology has been analyzed with great exertion in the last part of the thesis. To obtain better value of beforehand emendation for maneuvering terminals, the movement characteristics of terminal must be understood well. Firstly, the motion time course for speed of 18kn under the condition of second level ocean wave was given through the numerical simulation of naval ships. Secondly, SPFM (Sliding Polynomial Fitting Method) was discussed and the arithmetic has been compared with PFM (Polynomial Fitting Method). Meanwhile, the model was corrected, and the parameters of arithmetic--system sampling frequency, the length of sliding window and the exponent of fitting polynomial--have been optimized. Finally, the small computing load and error, and the better estimation effect can be obtained when sampling frequency is more than 4Hz and sliding window is between 10 and 20 and polynomial exponent equals 3 or 4 by the computer-based simulation. When the speed of naval ships varies from 0 to 30kn, the estimated error is found increased. While the naval ships reach a certain speed, the estimated error will keep constant.更多还原