精品外文翻译基于m序列的扩频通信系统的仿真设计外文翻译.docx

精品外文翻译基于m序列的扩频通信系统的仿真设计外文翻译.docx

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精品外文翻译基于m序列的扩频通信系统的仿真设计外文翻译

中文字数7504字

届毕业设计外文翻译

毕业设计题目:

基于m序列的扩频通信系统的仿真设计

外文翻译题目:

SpreadSpectrumTechniques

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SpreadSpectrumTechniques

ByWikipedia

Abstract:

Spread-spectrumtechniquesaremethodsbywhichasignal（e.g.anelectrical,electromagnetic,oracousticsignal）generatedinaparticularbandwidthisdeliberatelyspreadinthefrequencydomain,resultinginasignalwithawiderbandwidth.Thesetechniquesareusedforavarietyofreasons,includingtheestablishmentofsecurecommunications,increasingresistancetonaturalinterferenceandjamming,topreventdetection,andtolimitpowerfluxdensity（e.g.insatellitedownlinks）.

HistoryFrequencyhopping:

Theconceptoffrequencyhoppingwasfirstalludedtointhe1903U.S.Patent723,188andU.S.Patent725,605filedbyNikolaTeslainJuly1900.Teslacameupwiththeideaafterdemonstratingtheworld'sfirstradio-controlledsubmersibleboatin1898,whenitbecameapparentthewirelesssignalscontrollingtheboatneededtobesecurefrom"beingdisturbed,intercepted,orinterferedwithinanyway."Hispatentscoveredtwofundamentallydifferenttechniquesforachievingimmunitytointerference,bothofwhichfunctionedbyalteringthecarrierfrequencyorotherexclusivecharacteristic.Thefirsthadatransmitterthatworkedsimultaneouslyattwoormoreseparatefrequenciesandareceiverinwhicheachoftheindividualtransmittedfrequencieshadtobetunedin,inorderforthecontrolcircuitrytorespond.Thesecondtechniqueusedavariable-frequencytransmittercontrolledbyanencodingwheelthatalteredthetransmittedfrequencyinapredeterminedmanner.Thesepatentsdescribethebasicprinciplesoffrequencyhoppingandfrequency-divisionmultiplexing,andalsotheelectronicAND-gatelogiccircuit.

FrequencyhoppingisalsomentionedinradiopioneerJohannesZenneck'sbookWirelessTelegraphy（German,1908,EnglishtranslationMcGrawHill,1915）,althoughZenneckhimselfstatesthatTelefunkenhadalreadytrieditseveralyearsearlier.Zenneck'sbookwasaleadingtextofthetime,anditislikelythatmanylaterengineerswereawareofit.APolishengineer,LeonardDanilewicz,cameupwiththeideain1929.Severalotherpatentsweretakenoutinthe1930s,includingonebyWillemBroertjes（Germany1929,U.S.Patent1,869,695,1932）.DuringWorldWarII,theUSArmySignalCorpswasinventingacommunicationsystemcalledSIGSALYforcommunicationbetweenRooseveltandChurchill,whichincorporatedspreadspectrum,butduetoitstopsecretnature,SIGSALY'sexistencedidnotbecomeknownuntilthe1980s.

ThemostcelebratedinventionoffrequencyhoppingwasthatofactressHedyLamarrandcomposerGeorgeAntheil,whoin1942receivedU.S.Patent2,292,387fortheir"SecretCommunicationsSystem".LamarrhadlearnedabouttheproblematdefensemeetingsshehadattendedwithherformerhusbandFriedrichMandl,whowasanAustrianarmsmanufacturer.TheAntheil-Lamarrversionoffrequencyhoppingusedapiano-rolltochangeamong88frequencies,andwasintendedtomakeradio-guidedtorpedoesharderforenemiestodetectortojam.Thepatentcametolightduringpatentsearchesinthe1950swhenITTCorporationandotherprivatefirmsbegantodevelopCodeDivisionMultipleAccess（CDMA）,acivilianformofspreadspectrum,thoughtheLamarrpatenthadnodirectimpactonsubsequenttechnology.ItwasinfactongoingmilitaryresearchatMITLincolnLaboratory,MagnavoxGovernment&IndustrialElectronicsCorporation,ITTandSylvaniaElectronicSystemsthatledtoearlyspread-spectrumtechnologyinthe1950s.Parallelresearchonradarsystemsandatechnologicallysimilarconceptcalled"phasecoding"alsohadanimpactonspread-spectrumdevelopment.

Commercialuse

The1976publicationofSpreadSpectrumSystemsbyRobertDixon,ISBN0-471-21629-1,wasasignificantmilestoneinthecommercializationofthistechnology.Previouspublicationswereeitherclassifiedmilitaryreportsoracademicpapersonnarrowsubtopics.Dixon'sbookwasthefirstcomprehensiveunclassifiedreviewofthetechnologyandsetthestageforincreasingresearchintocommercialapplications.

Initialcommercialuseofspreadspectrumbeganinthe1980sintheUSwiththreesystems:

EquatorialCommunicationsSystem'sverysmallaperture（VSAT）satelliteterminalsystemfornewspapernewswireservices,DelNorteTechnology'sradionavigationsystemfornavigationofaircraftforcropdustingandsimilarapplications,andQualcomm'sOmniTRACSsystemforcommunicationstotrucks.IntheQualcommandEquatorialsystems,spreadspectrumenabledsmallantennasthatviewedmorethanonesatellitetobeusedsincetheprocessinggainofspreadspectrumeliminatedinterference.TheDelNortesystemusedthehighbandwidthofspreadspectrumtoimprovelocationaccuracy.

In1981,