卫星通信远端站数字基带系统的研究和实现
Research and Implementation of Digital Baseband Satellite Communication System for Remote Station
【中文摘要】 软件无线电是一种全新的通信系统设计理念,将通信系统的功能利用软件的方式实现在通用的硬件平台上,使得通信系统能够适应多种“标准”以及调制方式。采用软件无线电思想设计的通信系统具有很强的适应能力与扩展性,因而软件无线电技术的研究与实现对新一代通信系统的设计有着非常重大的意义。本文对通信系统的软件无线电实现做了一定的研究,并具体结合本人实际设计的卫星通信数据采集系统来阐述软件无线电的设计思路与通信领域中的关键技术。本文首先研究了QPSK解调器的实现,利用两块专用的QPSK解调芯片实现解调功能,并结合这两块芯片的内部结构,分析了锁相环路的工作原理、跟踪性能以及频率捕获与跟踪的原理。然后在Costas环的基础上讨论了频率捕获技术中的一个重要问题:频率的错锁,经过理论推导指出了错锁的来源以及错锁点的位置。试验数据与图片表明这两块芯片确实能够实现QPSK解调功能。其次,本文讨论了通信中比较重要的信道编译码技术,重点介绍了Viterbi译码器的FPGA实现并提出了实现中的两大问题:路径度量值溢出和回溯算法的实现。同时给出了相应的解决方案:二进制补码取模和流水线的回溯算法,并取得了很好的效果。最后对各个分模块进行了介绍,而且给出一种纠正QPSK解调器相位模糊问题的新思路,利用Modelsim对整个设计进行仿真并验证设计的有效性。再次,本文深入讨论了信噪比检测技术,介绍了两种不同的信噪比检测方法,即信号分解法和四阶矩法,并对其中的四阶矩方法做了改进。仿真结果表明:1.信号分解算法在大信噪比情况下(>5dB)工作良好但是对小信号将产生比较大的估计误差。2.四阶矩算法在小信号情况下(>-10dB)能正常工作而且改进后的算法在信号非常小的情况下(<-10dB)将给出比原算法更好的估计结果。利用DSP具体地实现了信号分解算法,并给出了实际测得的卫星信道信噪比估计结果。最后给出了该系统的测试结果与性能分析,测试结果表明该卫星通信系统能够实现预想的通信功能。然后对该卫星通信系统整体设计方案进行了讨论,并针对其中的不足作出了改进,而且最终实现了改进的方案。在已经实现的方案基础上又提出了新的完全基于软件无线电设计思想的系统方案,该方案利用信道中导频信号巧妙地简化了频率捕获与跟踪问题。

【英文摘要】 Software radio is a new technique that is used in the development of communication system. It can give the communication system high adapting ability and broad expansibility. So research of software radio can contribute a lot to the development of new generation communication system. This paper makes a deep research on the technique of software radio and discusses a lot about the key techniques in the communication field based on a satellite communication system which is designed by the author.QPSK demodulator is the first part and has been realized by two ASIC which are HSP50110/HSP50210. From discussing some details of the two chips, it can give a full explanation of QPSK demodulation and frequency acquisition and tracking. Also a common issue, false lock, has been introduced. Through the deduction based on Costas loop, it is clearly to understand the principium of the false lock and verify the false lock position. In the end, experimental data and chart are given to show the two chips can work well.Secondly, this dissertation focuses on the implementation of Viterbi algorithm by FPGA. There are two problems in the design of Viterbi decoder which are overflow of path metric and trace back algorithm and they have been resolved respectively by Two’s Complement Modulo technique and pipeline memory management. Then this paper goes through the details of different modules of the Viterbi decoder and the simulation results of Modelsim have been given to testify the validation of the design.Thirdly, this dissertation researches on SNR Estimator and introduces two algorithms which are signal decomposition algorithm and Four-Order Moments algorithm. An improvement on Four-Order Moments algorithm is proposed and based on the simulation result, and there are two conclusions as follows:1. The signal decomposition algorithm can work well under enough SNR(>5dB), while it would lost accuracy for small signal.2. The Four-Order Moments algorithm can give wonderful estimation of small signal (>-10dB) and the improvement of this algorithm owns better result for extreme small signal(<-10dB).In the satellite communication system, signal decomposition algorithm has been realized by DSP and actual experimental results are given.Finally, an introduction of this satellite communication system is given and some improvements are made according to the weakness of the former design. Based on the improved one, the author has turned it into a real product which has all the functions finished. On the base of the implementation of the improved design, a whole new design scheme is proposed, a design that absolutely incarnating the software radio spirit. By utilizing the guiding frequency, the frequency acquisition and tracking can be realized more easily. 

【中文关键词】 DSP; Viterbi; 信噪比检测; Costas环
【英文关键词】 DSP; Viterbi; SNR Estimation; Costas Loop
【毕业论文目录】
  卫星通信远端站数字基带系统的研究和实现

摘要 4-6
ABSTRACT 6-7
第1章 概述 11-20
    1.1 软件无线电概述 11-14
        1.1.1 软件无线电的概念 12-13
        1.1.2 软件无线电系统“软件化”程度的评价 13-14
        1.1.3 软件无线电的关键技术 14
    1.2 卫星通信系统概述 14-18
    1.3 论文主要内容与组织结构 18-20
第2章 QPSK 解调与载波同步的实现 20-38
    2.1 QPSK 介绍 20-22
    2.2 QPSK 解调 22-34
        2.2.1 Costas 环与HSP50110/HSP50210 芯片组 22-25
        2.2.2 载波环数学模型与参数控制 25-28
        2.2.3 环路错锁分析及解决方法的实现 28-34
    2.3 系统实现与性能测试 34-37
    2.4 本章小结 37-38
第3章 信道编解码的实现 38-66
    3.1 信道编码 38-42
        3.1.1 扰码 38-41
        3.1.2 卷积编码 41-42
    3.2 Viterbi 译码器中关键技术的解决与 FPGA 实现 42-62
        3.2.1 加比选模块与度量值溢出处理 43-47
        3.2.2 流水线路径回溯算法 47-50
        3.2.3 Viterbi 模块中关键技术的解决与功能描述 50-62
    3.3 相位模糊问题的解决与仿真结果分析 62-65
        3.3.1 ISE6.1 FPGA 开发平台 62-63
        3.3.2 相位模糊仿真结果分析 63-65
    3.4 本章小结 65-66
第4章 信噪比检测算法的优化与DSP 实现 66-81
    4.1 噪声的定义 66-68
    4.2 信噪比估计算法 68-74
        4.2.1 信号分解估计算法 68-71
        4.2.2 基于四阶矩的信噪比估计算法 71-72
        4.2.3 改进的四阶矩信噪比估计算法 72-73
        4.2.4 算法的改进及性能与测试结果分析与仿真 73-74
    4.3 自动功率控制方案及Eb/ N 0 的DSP 实现 74-79
        4.3.1 自动功率控制方案 74-76
        4.3.2 ADI Blackfin DSP 简介 76-77
        4.3.3 实现方案 77-79
    4.4 本章小结 79-81
第5章 系统测试结果分析与方案的改进 81-91
    5.1 系统测试结果分析 81-87
        5.1.1 调制器误码率测试 81-82
        5.1.2 解调器误码率测试 82-84
        5.1.3 解调器数据测试 84-85
        5.1.4 HDLC 协议测试 85-87
    5.2 系统方案的改进 87-91
        5.2.1 最初的设计方案 87-88
        5.2.2 改进的设计方案 88-89
        5.2.3 最新的设计方案 89-91
第6章 总结与展望 91-93
参考文献 93-95
附录1 95-96
附录2 96-97
致谢 97-98
攻读学位期间发表的学术论文 98-99
上海交通大学学位论文答辩决议书 99