AN379 ANTENNA DIVERSITY WITH EZRADIOPRO英文文献资料

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1、AN379A®NTENNADIVERSITYWITHEZRADIOPRO1.PurposeThisdocumentdescribestheconceptofantennadiversity,atechniquethatcanbeusedtorecoverradiocommunicationinenvironmentsofdifficultreception.Antennadiversitycangreatlyimproveperformanceundermulti-pathfadingconditions.Thisdocumentalsoprovidesreal-worldmeasure

2、mentexamplesbydemonstratingtheimprovementthatcanbeachievedwiththebuilt-inantennadiversityavailableusingtheEZRadioPRO®wirelessfamilyofRFICs.Whileantennadiversitycanachievesignificantrangeimprovementsinwirelesscommunicationsystems,itisoftennotimplementedduetotheaddedcomplexity,computationcost,andcu

3、rrentconsumptionthatisrequiredtoimplementtherequisitealgorithmonthesystemMCU.EZRadioPROdeviceshaveabuilt-inantennadiversityalgorithmthatremovestheneedforthecustomertoimplementanyadditionalfirmwareontheirsystemMCU.ByincorporatingtheantennadiversityalgorithmintotheEZRadioPROdevicesdirectly,customer

4、scanachievethebenefitsofdiversitywithouttheproblemsofdevelopinganddebuggingthealgorithmthemselves,resultinginamorerobustsolutionandafastertimetomarket.2.OverviewofAntennaDiversity2.1.PerformanceDegradationduetoMultipath/FadingFadingisthephenomenaoftenobservedwhensmallmovementsbyeitheratransmitter

5、orareceivercanleadtolargedifferencesinlinkquality.Thishappensasanantennamovesinandoutofthepeaksofasignal.Figure1.FadingEffectsonanAntennaRev.0.22/10Copyright©2010bySiliconLaboratoriesAN379AN379Multipathexpandsonthisconcept.Asradiowavesaretransmitted,theymaynotbereceivedbythereceiverthroughonesign

6、alpath,butmaycomefrommultiplepathsthroughreflectionsoffotherobjectssuchaswallsandtrees-multipath.Thesignalsreceivedfromeachofthesepathsarelikelytoarriveatslightlydifferenttimeintervalsmeaningslightphaseshiftsmayoccur.Whenthesesignalscombinetheymayresultinpartialornear-totalcancellation-fading.Fig

7、ure2.DirectandIndirectRFPathwaysFigure3.WorstCaseRFFadingEffectfromPhaseShiftsCausedbyMultipathUsingaworstcasescenario,itcanbedemonstratedthatshouldtwosignalsarriveatareceiverwithequalamplitudesbutexactly180degreesouto