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1、毕业（设计）论文外 文 翻 译外文题目ANINTRODUCTIONTOSPEREAD-SPECTRUMCOMMUNICATION译文题目扩频通信系统的介绍系别机电工程系专业测控技术与仪器班级162902学生姓名王延学号092151指导教师吴鹏飞报告日期2012.3.1817ANINTRODUCTIONTOSPEREAD-SPECTRUMCOMMUNICATIONIntroductionAsspread-spectrumtechniquesbecomeincreasinglypopular,electricalengineersout
2、sidethefieldareeagerforunderstandableexplanationsofthetechnology.Therearebooksandwebsitesonthesubject,butmanyarehardtounderstandordescribesomeaspectswhileignoringothers(e.g.,theDSSStechniquewithextensivefocusonPRN-codegeneration).Thefollowingdiscussioncoversthefullspec
3、trum(punintended).AShortHistorySpread-spectrumcommunicationstechnologywasfirstdescribedonpaperbyanactressandamusician!In1941HollywoodactressHedyLamarrandpianistGeorgeAntheildescribedasecureradiolinktocontroltorpedoes.TheyreceivedU.S.Patent#2.292.387.Thetechnologywasnot
4、takenseriouslyatthattimebytheU.S.Armyandwasforgottenuntilthe1980s,whenitbecameactive.Sincethenthetechnologyhasbecomeincreasinglypopularforapplicationthatinvolveradiolinksinhostileenvironments.Typicalapplicationsfortheresultingshort-rangedatatransceiversincludesatellite
5、-positioningsystemsGPS，3Gmobiletelecommunications,W-LAN(IEEE®802.11a,IEEE802.11b,IEEE802.11g),andBluetooth®.Spread-spectrumtechniquesalsoaidintheendlessracebetweencommunicationneedsandradio-frequencyavailability-situationswheretheradiospectrumislimitedandis,therefore,a
6、nexpensiveresource.TheoreticalJustificationforSpreadSpectrumSpread-spectrumisapparentintheShannonandHartleychannel-capacity17theorem:C=B×log2(1+S/N)(Eq.1)Inthisequation,Cisthechannelcapacityinbitspersecond(bps),whichisthemaximumdatarateforatheoreticalbit-errorrate(BER)
7、.BistherequiredchannelbandwidthinHz,andS/Nisthesignal-to-noisepowerratio.Tobemoreexplicit,oneassumesthatC,whichrepresentstheamountofinformationallowedbythecommunicationchannel,alsorepresentsthedesiredperformance.Bandwidth(B)isthepricetobepaid,becausefrequencyisalimited
8、resource.TheS/Nratioexpressestheenvironmentalconditionsorthephysicalcharacteristics(i.e.,obstacles,presenceofjammers,
