扩频多径信道下的RAKE接收机.docVIP

天津理工大学 《扩频通信》课 程 报 告 扩频多径信道下的RAKE接收机 姓名： 刘 琛 学号： 133127314 扩频多径信道下的RAKE接收机 摘要：Walsh码是一种同步正交码，即在同步传输情况下, 利用Walsh码作为地址码具有良好的自相关特性和处处为零的互相关特性Walsh码生成容易应用方便。多径信号中含有可以利用的信息，所以接收机可以通过合并多径信号来改善接收信号的信噪比。RAKE接收技术实际上是一种多径分集接收技术，可以在时间上分辨出细微的多径信号，对这些分辨出来的多径信号分别进行加权调整、使之复合成加强的信号。RAKE接收机。Walsh码 RAKE接收技术 分集技术 Abstract: Walsh code is a kind of?synchronous orthogonal?codes,??namely that using the Walsh?code as address codes? with the properties of good autocorrelation ?and?good ?cross-correlation in the?synchronous transmission?case?. Meanwhile the Walsh code generates?easily?and handily,?and it has been widely?used in communication systems.?In mobile communication system,?because of the influence of city?building and terrain,?wave propagation process?will appear the?route and time delay?of different,?and then the?multipath effect appears, which seriously affect the quality of the communication?system.?The traditional Diversity technique?treats the?multipath signals as interference signals.?However,?with?the available information,?multipath?signal can be?used to improve?the SNR of received signal by the?receiver.?Based on the above?principle,?the RAKE receiving technology?is actually a?multipath diversity?receiving?technology,?which can?distinguish subtle multipath signals?in time,?and then weighting these multipath signals,?then?making the signals stronger.?Using the characteristic,?the RAKE receiver can achieve the goals of realizing the diversity reception,?resisting multipath interference?and fading. Key Words：Walsh codeThe RAKE receiving technology Diversity technique 目 录 一、Walsh函数及Walsh码 1 二、RAKE接收 3 2.1、RAKE接收的基本原理 3 2.2、RAKE接收机的数学实现模型 5 三、分集接收 8 3.1 空间分集 8 3.2 频率分集 8 3.3 时间分集 9 3.3.1最大比合并 9 3.3.2 等增益合并 10 3.3.3 选择式合并 10 四、附录 13 Walsh函数及Walsh码 在移动通信的发展过程中，随着通信容量和频带利用率的日益提高，会出现信道污染、交换技术复杂等问题。为解决这些问题，近年来形成了一种新的体制，即码分多址通信（CDMA）。CDMA技术的关键就是要产生不不同的相互正交的码序列，有多少个正交序列，就可以有多少个不用的码分信道，也就有多少人同时使用。 Walsh码又称沃尔什函数，在码分多址移动通信中占据非常重要的地位。Walsh码是一种正交码，具有良好的同步正交性，Walsh函数有