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直接序列扩频的检测及参数估计摘要直接序列扩频通信具有低截获率、抗衰落能力强、抗多径干扰等优点，广泛应用于军事通信和民用通信。随着电子战和信息战技术的发展，非合作通信条件下扩频信号的检测与参数估计成为扩频通信领域的研究热点，为了适应未来战争对电子侦察技术的需要，研究低信噪比下直接序列扩频信号检测与参数估计方法具有重要的现实意义。本文对低信噪比情况下直扩信号的检测及参数的估计进行了理论研究。首先简要概述了扩频通信的基本知识；再采用自相关法及循环谱法完成对未知信号的检测；在确定未知信号是要分析的BPSK—DSSS信号后，先采用平方倍频法估计出信号的载频，然后通过信号功率谱的二次处理法估计出PN码周期，采用信号延迟相乘对能量进行累积，判断能量最大化的方法，估计出PN码同步起止时刻及一个PN码周期内的信息码元个数；最终根据估计估计的参数完成了PN序列的恢复。理论仿真表明，本文采用的检测和参数估计方法对码长为31~1023的短PN码调制直扩信号均适用。关键词：直接序列扩频信号；参数估计；延时相乘法；循环谱；码速率；码周期直接序列扩频的检测及参数估计ABSTRACTDirectsequencespreadspectrumcommunicationsystemhavebeenwidelyusedinmilitaryandcivilcommunication.Becauseithasmanyadvantagessuchasanti-jammingcapability,lowprobabilityofinterception,multipleaccesscapabilityandsoon.Withthedevelopmentoftheelectronandinformationtechnology,theresearchofdetectionandparameterestimationofspreadspectrumsignalsinnon-cooperationcommunicationhasbeenaresearchhotspot.Tomeetthefuturedemandofelectronicreconnaissancetechniques,itisofgreatsignifieancetostudyparameterestimationmethodsforDSSSsignalsunderlowSNRs.Thetheoryresearchonthedetectionandparameterestimationofspreadspectrumsignalsinlowsignaltonoiseratios(SNR)areaccomplished.Firstly,thepapersummarizethebasicknowledgeofspreadspectrumcommunication.Secondly,themethodofcorrelationdetectionapproachandcyclicspectrumapproachisusedtodetecttheunknowsignals.AftertheunkownsignalisthesignalofBPSK-DSSS,thesquaredetectionisusedtoestimatethethecarrierfrequencyofthesignals,thereprocessedpowerspectrumofDSSSisusedtoestimatethesymbolperiod,thecyclicspectrumapproachisusedtoestimatethechiprate,thenaccordingtotheprincipleofthebase-bandsignaloftheDSsignalcanbeachievedmaximizethroughtheaccumulationofenergy,usingthetwo-dimensionalsearchalgorithm,notonlytheproblemofthestartofsynchronizationofthePNcodeandinformationcodeisresolvedsuccessly,butalsothenumberofinformationcodeinthelongpseudo-codemodulationisestimated.Finally,thePNsequenceisrecoveried.TheorysimulationresultsshowthatthemethodsmentionedarefeasibletodetectandestimatethePNsequencemodulationDSsignalswhosePNsequencelengthis31to1023.KeyWords:DSSS;parametersestimation;delayandmultiply;cyclicapectrum;chiprate;PNperiod直接序列扩频的检测及参数估计目录摘要......................................................................................................................................................................1ABSTRACT.........................................................................................................................................................2第1章引言.....................................................................................................................错误!未定义书签。1.1.直接序列扩频系统的研究背景...................................................................................................................11.2.直接序列扩频系统的特点...........................................................................................................................21.3.国内外研究现状...........................................................................................................................................3第2章直接序列扩频通信技术....................................................................................................................62.1.直接序列扩频的概念及理论基础...............................................................................................................62.1.1.直接序列扩频的概念.........................................................................................................................62.1.2.扩频通信的理论基础.........................................................................................................................62.1.3.扩频增益和抗干扰容限.....................................................................................................................72.2.直接序列扩频的基本原理...........................................................................................................................82.3.直扩系统的性能.........................................................................................................................................112.3.1.直扩系统的抗干扰性.......................................................................................................................112.3.2.直扩信号的抗截获性.......................................................................................................................122.3.3.直扩码分多址通信系统...................................................................................................................122.3.4.直扩系统的抗多径干扰性能...........................................................................................................132.4.扩频通信系统的同步原理.........................................................................................................................14第3章直扩信号的检测..............................................................................................................................163.1.自相关检测法............................................................................................................................................163.2.循环谱检测法..................................................