【正文】 1 CDMA 移動通信 RAKE 接收技術研究 摘要 ： RAKE 接收技術是 CDMA 擴頻通信的關鍵技術之一，作為 CDMA 系統(tǒng)中實現(xiàn)多經(jīng)分集接收的核心部件，它可以分辨出接收信號中不同的多徑分量，克服多徑衰落，提高系統(tǒng)性能。RAKE 接收技術可以在時間上分辨出細微的多徑信號，對這些分辨出來的多徑信號分別進行加權調整、使之復合成加強的信號。 本文對在 CDMA 移動通信中的 RAKE 接收機進行了簡要的介紹， 其基本原理是將信號的多徑分量提取出，對他們進行延遲和相位校正，使之在某一時刻對齊，并按一定的規(guī)則進行合并，變矢量 合并為代數(shù)合并，有效地利用多徑，提高多徑分集的效果。本文還根據(jù) RAKE接收技術的原理 設計了接收機的系統(tǒng)框圖， 用三種不同的合并方式， 利用 matlab 實現(xiàn)了多徑信道的仿真 ， 并賦予了相應的說明， 分析 RAKE 接收機的性能 。 關鍵詞 ： CDMA ； RAKE 接收 ；多徑 ；分集接收 2 Abstract： The Rake receiver is one key techniques of the CDMA spreading spectrum munication .As for the core part of achieving the multipath diversity reception of CDMA system .It can distinguish the different multipath ponents in received signals ,overe the diversity fading ,and improve the system performance .RAKE receiver technique can distinguish the subtle multipath signals in time domain ,modulate the distinguished signals ,posite into the enhanced signals . This paper has simply introduced the RAKE receiver in CDMA system ,the basic principal is to extract the multipath ponent of signals,and delay them for the phase calibration ,to make the phase identical at some moment,and merge based on some rules . Change the vector bination into the algebra bination to use the multipath effectively and to enhance the effect of the multipath diversity . The paper also designs the system block diagram of the RAKE receiver by three different bining methods , and achieve the simulated multipath channel by matlab and containing some corresponding notes . Key words: CDMA 。 RAKE receiver 。 multipath 。 diversity reception 。 3 目錄 CDMA 移動通信 RAKE 接收技術研究 .................................................................................... 1 目錄 ................................................................................................................................. 3 1 緒論 ............................................................................................................................. 4 所選課題的目的和意義 ....................................................................................... 4 國內外研究現(xiàn)狀 ................................................................................................. 5 本文的研究內容及安排 ....................................................................................... 6 2 CDMA 的基本原理 ........................................................................................................... 7 碼分多址基本概念 .............................................................................................. 7 CDMA 通信系統(tǒng)的優(yōu)點 ......................................................................................... 8 抗干擾能力強 ........................................................................................... 8 系統(tǒng)容量大 .............................................................................................. 8 軟容量 ..................................................................................................... 8 保密性強 ................................................................................................. 8 高的話音質量和低的發(fā)射功率 .................................................................. 8 易于實現(xiàn)精確定時與測距 ......................................................................... 8 多址技術 ............................................................................................................ 9 時分多址 （ TDMA） ................................................................................. 9 頻分多址 （ FDMA） ................................................................................. 9 碼分多址 （ CDMA） ................................................................................10 擴頻技術 ...........................................................................................................10 3 RAKE 接收技術 ..........................................................................................................12 RAKE 接收機及其譯名 .................................................................................12 RAKE 接收機的基本原理 ..............................................................................13 RAKE 接收機的數(shù)學實現(xiàn)模型 .......................................................................16 RAKE 接收機誤碼性能分析 ..........................................................................19 4 RAKE 接收機的仿真 ....................................................................................................23 初狀態(tài)設定 ................................................................................................23 MATLAB 性能仿真 ........................................................................................24 MATLAB 仿真結果及分析 ..........................................................................24 5 總結與展望 ..................................................................................................................26 本文所做的工作 .........................................................................................26 CDMA 通信系統(tǒng)中 RAKE 接收技術的展望 .........................