CDMA直扩收发系统的Simulink仿真

范文编号:TX297  范文字数:16131,页数:39

摘  要
 
 从人类开始进入信息社会至今，通信技术的发展取得了令人瞩目的成绩。随着通信的普及，信道中的各种干扰也愈加增多。如何在恶劣的环境条件下保证信息能够有效可靠的传输已俨然成为当今通信研究人员所面临的重大难题。
 扩频通信是指用于传输信号的信道带宽远远大于信号自身带宽的一种通信方式。与传统无线通信方式相比，其在抗噪声、抗干扰、抗多径衰落、码分多址、信号的隐蔽性及保密性等方面有着无与伦比的优势，从而与光纤通信、卫星通信一起被誉为信息时代的三大主流通信传输方式。本文主要阐述用simulink软件对CDMA直扩收发系统进行仿真，研究其优越的抗噪声、抗干扰、抗多径、多址等性能。
 本文的主要内容有：
 1. 对扩频通信中各种主要技术进行一定的理论分析；
 2. 对当前一些流行的模型实现方法进行描述，包括数字匹配滤波捕获技术、迟早环跟踪技术等；
 3. 介绍如何使用simulink软件进行扩频通信系统的仿真；
 4. 结合仿真结果对扩频通信系统进行性能分析。
关键词：扩频通信；simulink；CDMA直扩收发系统；

Abstract
 
 From the information society humans enter, the development of communication technology has making miraculous progress. As the popularization of communication, a variety of Interference in transport channel increases dramatically. That how to transport information efficiently and correctly under the adverse circumstances has become a rough problem the researcher of communication has to face with
 Spread spectrum communication is a kind of communication patterns in which the band bandwidth  used to transport information is far larger than the original signal. Compared with the traditional wireless communication, it has many unparalleled advantages on the performance of anti-noise, anti-jamming, fighting against multi-path fading, code division multiple access and the elusive and confidentiality of the signal. It has become the three major communication patterns with the fiber communication and satellite communications. This text mainly expound that how to simulate the DS-CDMA system use the SIMNLINK software and study it’s superior  capacity of anti-noise, anti-jamming, fighting against multi-path fading and code division multiple access.
 The main body of this article as follows:
 1. Studying the main technology theoretically in Spread spectrum communication;
 2. Depicting some current mode, including digital matched filter for capture, L L-DPLL for coder tacking and so on;
 3. Illuminating how to use the SIMULINK software to simulate the DS-CDMA system;
 4. Analyzing the performance of the DS-CDMA system combined with the consequence of simulation.
Keyword: spread spectrum communication; simulink; DS-CDMA

目    录
引言·1
1  扩频通信理论分析·1
1.1 扩频通信理论基础1
1.1.1 Shannon公式·1
1.1.2 直接序列系统·2
1.1.3 扩频通信系统的模型分析3
1.1.4 扩频通信系统的处理增益4
1.1.5 扩频通信系统的干扰容限4
1.2 直扩系统的m序列·5
1.3 扩频信号的调制与解调·7
1.4 扩频系统的同步·9
1.4.1 扩频系统的捕获9
1.4.2扩频系统的跟踪·13
2  用simulink软件对DS-CDMA系统进行仿真15
2.1 simulink简介15
2.2 模型搭建与主要模块设计·15
2.2.1 信源及扩频码·15
2.2.2 信号调制·17
2.2.3 信道·18
2.2.4解调与解扩19
2.2.5低通滤波20
2.2.6扩频同步的捕获21
2.2.7扩频同步的跟踪24
2.3 直接序列扩频通信系统仿真模型·26
3  仿真结果及分析·28
3.1 ｍ序列及信源仿真分析28
3.2调制解调仿真分析30
3.3捕获性能分析32
3.4跟踪性能分析33
3.5抗多径干扰分析·34
3.6多用户干扰分析36
3.7直扩系统整体性能分析37
4  结论·37
谢辞38
参考文献·39

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