摘要直接序列扩频通信系统由于信号发射功率小、抗干扰性好、隐蔽，容易完成码分多址（CDMA），抗多径，作为一种十分先进的高科技的通信技术手段，直接序列扩频通信势必会成为下一代移动通信技术的关键。直接序列扩频通信速率有着明显的优势，在生活中有着广泛的应用。直接序列扩频通信技术在现在的移动通信系统中的地位已经变得越来越重要了，它是使用最多的一种扩频通信系统，随着无线通信已经越来越离不开人们的生活，它受到人们的关注度也越来越多。85050

本文根据扩频通信的基本原理，通过MATLAB软件对信号依次进行扩频码构成，扩频、调制、解扩、解调环节实现了直接序列扩频通信系统的仿真，并研究了扩频增益对扩频系统性能的影响，根据直序扩频通信系统的仿真结果得出扩频增益越大系统的性能越好；但是增益太大会影响系统的传输速率，所以扩频增益的选择要考虑这两方面的因素确保系统性能达到最佳。

毕业论文关键词：扩频序列；直序扩频；扩频增益；误码率

Abstract Direct sequence spread spectrum communication system is a very advanced high-tech technical means of communication and is bound to becoming the next generation mobile pass key technique, because it has advantages of small signal transmitting power , good anti - interference, hidden, easy to complete code pision multiple access (CDMA), anti-multipath interference。Direct sequence spread spectrum communication rate has obvious advantages and has a wide range of application in the life。 Status of direct sequence spread spectrum communication technology has become more and more important in the current mobile communication system。 It is the most popular spread spectrum communication system, with wireless communication having become increasingly inseparable in our lives, people also pay more attention to it。

According to the basic principle of spread spectrum communication, MATLAB software is used to construct the spread spectrum codes for signal, spread spectrum, modulation, solution of expansion, and countermodulation to achieve the simulation of direct sequence spread spectrum communication system and study the influence of the spread spectrum gain of spread spectrum system performance。 According to the results of the simulation of direct sequence spread spectrum communication system, the bigger of spread spectrum gain makes system greater; but too big affects the system the transmission rate of the system, so choosing spreading gain should consider these two factors to make the system performance best。

Key words: Spread spectrum sequence; Direct sequence spread spectrum; Spread spectrum gain; Bit error rate

目录

第一章 绪论 1

1。1 研究的背景和意义 1

1。2 国内外研究现状 1

1。3 论文结构和课题的研究内容 2

第二章 CDMA通信系统 4

2。1 多址技术 4

2。2 CDMA技术 4

2。3 CDMA数字移动通信的基本原理 6

第三章 直接序列扩频通信 7

3。1 直接扩频通信系统的理论基础 7

3。2直接序列扩频通信系统的原理 8

3。3扩频码 10

3。3。1 m序列 11

3。3。2 Gold码序列 12

3。4 直接序列扩频通信系统的同步原理