【作者】 秦岭；

【导师】 柯熙政；

【作者基本信息】 西安理工大学 ， 通信与信息系统， 2007， 硕士

【摘要】 大气激光通信是近年来人们关注的热点问题之一。它作为一种新的通信技术，拥有无线传输的便利和光纤通信的带宽优点，在几公里视距通信中具有非常诱人的前景，在局域网扩容、无线基站数据回传、临时应急通信、军事保密通信等领域已经崭露头角。调制解调是大气激光通信中的一项关键技术，脉冲位置调制(PPM)是大气激光通信系统中一种常用的调制技术。但是，PPM对带宽的要求很高，进而影响到信息传输的吞吐量。与PPM相比，多脉冲位置调制(MPPM)不仅可以提高带宽效率、功率效率和信息传输吞吐量。此外，它的抗干扰能力也较PPM优越。因此，这种调制技术越来越受到人们的重视。本文旨在根据MPPM的基本原理，分析其性能参数并与PPM进行比较，在此基础上寻求可行的编码映射方案，设计调制解调系统。文中的主要工作包括：1．根据MPPM的基本原理，对MPPM的传信能力、传输效率、带宽利用率等参数进行了详细的分析，并且与PPM进行了比较，为MPPM调制解调系统的设计提供了理论基础。2．推导了有保护时段的光MPPM信道容量的表达式。分析了光脉冲功率、系统带宽倒数以及单脉冲所含光子数对MPPM信道容量特性的影响。比较了MPPM和PPM在信道容量方面的优劣。3．利用矩阵的思想，提出了一种新的二脉冲的MPPM编码映射方法。这种方法采用一种通用的易实现的数学算法实现了输入二进制比特流与二脉冲MPPM符号之间的转换。4．采用Xilinx公司的Spartan-Ⅱ系列的FPGA为核心的处理板首次实现了三脉冲的MPPM编译码器。更多还原

【Abstract】 Atmospheric laser communication becomes one of the hot spots in recent years. It has advantages of wireless transmission and abundant bandwidth of fiber. It has good outlook in sight communication, and has apllied in expansion of LAN, data return of wireless base station, temporary emergency communication and military secure communication. Modulation-demodulation is a key technology in atmospheric laser communication. Pulse position modulation (PPM) is usually used in atmospheric laser communication system. But, the information throughput in transmission with PPM depends so much on bandwidth. Multi-pulse position modulation (MPPM) can increase efficiency of bandwidth, efficiency of power and information throughput compared with PPM. Besides, it has better anti-jamming ability than PPM and people pay more attention to this modulation technology.The purpose of this paper is to analyze property parameters of MPPM, compare with PPM, find feasible mapping scheme and design modulation-demodulation system based on principle of MPPM. This paper mainly focuses on the following aspects:1. According to principle of MPPM, MPPM parameters were analyzed and compared with PPMS for the purpose of design of MPPM system. These parameters include the capacity of information transmission, transmission efficiency, bandwidth efficiency, etc.2. Expression of MPPM channel capacity with protective time slot was deducted. It was evaluated that channel capacity of MPPM changed with optical pulse power, reciprocal of system bandwidth and the average number of photon for single pulse. The performance of MPPM was compared with PPM in channel capacity.3. A new mapping method for dual-pulse pulse position modulation was presented basing on matrix theory. It converted binary code stream to MPPM symbols by using a general mathematic method.4. Three-pulse position encoder and decoder of MPPM are realized with Xilinx’s FPGAprocessor.This project derives from Youth teacher characteristic and creative research plan of Xi’an University of Technology and the science and technology fund of Shannxi eduction department. It’s also a project of "Torch Plan", NO: 2002HK52.更多还原