DSCDMA通信系统中的RAKE接收技术研究-毕业设计论文.doc

摘 要 在CDMA移动通信系统中，因为信号带宽比较宽，会存在着复杂的多径无线电信号，所以通信受到多径衰落的影响。分集接收是抵抗多径衰落的有效方法，RAKE接收技术实际上是一种多径分集接收技术。RAKE接收机能够在时域中充分利用信号的多径结构，从而提高系统的输出信噪比 ，因而成为目前CDMA系统中广泛被应用的抗多径衰落技术。 本文在CDMA系统多径衰落信道下，对单用户RAKE接收机和多用户RAKE接收机进行MATLAB仿真。并分别对最大比合并、等增益合并、选择式合并这三种合并方式进行比较。仿真得到RAKE接收机的误码率性能。通过三种合并方式的比较，得出最大合并比方式的误码率性能最好。通过单用户与多用户RAKE接收机的比较，得出RAKE接收机更适合于多用户情况。 关键词 RAKE接收机；多径；多址；分集；误码率  ABSTRACT In the CDMA mobile communication system, because of the signal bandwidth is so wider that exist complex multipath radio signals, communication is effect by multipath fading. The diversity receiving techniques can efficacious reduce the influence of multipath fading, RAKE reception technology is actually a kind of multipath diversity. RAKE receiver can full use of the structure of multipath to improve the SNR of output signal,it have become the method accounting to multipath fading which widely use in CDMA communication system. This paper discussed the simulation under the condition of code division multiple access CDMA system multipath fading channel, single user RAKE receiver and RAKE receiver respectively between multiple users were simulated by MATLAB simulation software. And the biggest ratio merger, etc, choose best the merger of comparison of three kinds of merger. Simulation results are shown and also the SER performance parameters. Through the comparison of the three ways of merger,get the result that no way is more suitable than the largest ratio merger. Through a single user RAKE receiver with multiple users, RAKE receiver is more suitable for many users. Keywords　 RAKE receiver；Multipath；Multiple access；Diversity；SER  目 录 摘 要 I ABSTRACT II 第1章 概 论 1 1.1 课题背景 1 1.1.1 直扩码分多址（DS-CDMA） 1 1.1.2 移动信道传输 1 1.1.3 移动信道的多径传播 2 1.2 RAKE接收机的由来 3 1.3 国内外现状及研究成果 3 1.4 研究本课题的意义 4 第2章RAKE接收机设计的相关原理 5 2.1 码分多址与扩频 5 2.1.1 码分多址 5 2.1.2 扩频技术 6 2.2 分集接收原理 7 2.2.1 分集接收的定义 7 2.2.2 分集接收的方式 7 2.2.3 合并方式 8 2.3 RAKE接收机 9 2.3.1 RAKE接收机的定义 9 2.3.2 RAKE接收机的原理 10 2.3.3 RAKE接收机的性能分析 12 第3章 RAKE接收机的仿真 16 3.1 程序流程 16 3.