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1、RakeReceiverDefinition:Rakereceivetechnologyisoneofthemostimportanttechnologyin3rdgenerationCDMA/WCDMAmobilecommunicationsystem.InCDMA/WCDMA,thereareplentyofcomplicatedmultipathradiosignalsinthewiderangeofbandwidth.Theyaretransmittedfromdifferentpathtothereceiverwhichcanbringthet
2、imedifference.Receiverwillhaveseveraldifferentstrengthsignals.Itwillbringquitebigeffecttocommunication.However,RakeReceiverusesmultipath?diversityreceptiontechnologytodistinguishthetinydifferencesineachreceived-signal.Inaddition,itcandoweightingadjustmentonthesemultipathsignalsan
3、dstrengthenthemtomakeitbecometheoriginalsignal.TheprincipleofRakeReceiverisDiversityReceptionTechnology.TherearefourkindsofdiversitytechnologywhichareSpaceDiversity,TimeDiversity,FrequencyDiversityandPolarizationDiversity.Spacediversityistouseseveralsub-receiverstoreceivethesigna
4、lindividuallythencombinethemthatcanhighlydecreasetheattenuation.FrequencyDiversityistosendandreceivethesamedatebyseveralmicrowavefrequencywhichhavesamefrequencyspace.Thenthesystemcancombineorselectthembycomparingthedifferencebetweendifferentfrequencybands.TimeDiversityissendingth
5、esamedateindifferenttimedomains.Alternatively,aredundant?forwarderrorcorrectioncode?isaddedandthemessageisspreadintimebymeansof?bit-interleavingbeforeitistransmitted.Polarizationdiversity:istousemultipleversionsofasignaltransmittedandreceivedviaantennaswithdifferentpolarization.A
6、diversitycombining?techniqueisappliedonthereceiverside.InRakeReceiver,thereareasetofsub-radiowhicharetheindividualcomponentsofthemultipathcanbetunedproperlyanddecodedcompletelyindependentlybutcombineatlast.Eachofthesub-radioRakeReceiverisaFingerwhichisusedtocollecttheenergyofbito
7、rsymbolfromchannel.Indetail,CDMAusedmultiplecorrelatingreceiversandallocationeachreceived-signaltothestrongestsignalwhichisfeasiblefortheCDMAsendthesynchronizedmobilesignaltotheservingbasestation.Whenasignalhasbeensentfromthephone,mobilereceivercandistinguishthedirectsignalseasil
8、ybecausedirectsignaltaketheshortesttimet
