Rake receiver瑞克接收机

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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