高通RF Calibration 介绍.ppt

RFCalibrationIntroduction,Agenda,WhatisRFcalibration.Whycalibration.NVitemsofRFcalibration.RxCalibration.TxCalibration.,WhatisRFcalibration,RFcalibrationistheprocessofmeasuringdatatobeusedinthesystemforthepurposeofcompensationofnon-linearcharacteristicsandfrequencyvariations,andtoprovideabsolutepowerreferenceandtemperaturecompensationtoensureperformanceoftheTxandRxpathsofasubscriberunit.Outputfromthecalibrationprocessisstoredinnon-volatile(NV)memoryitemsinAMSS.AMSSusescalibrationvaluesduringnormaloperationtoensuresystemperformanceismet.,Setup:,WhatisRFcalibration,Whycalibration,SubscriberunitshavedifferingRFcharacteristicsDifferencesindesignPart-to-partvariationsofcomponentsofthesamedesign,IndividualphonesalsochangetheirownRFcharacteristics:overfrequencychannelovertemperature,Whycalibration,Whycalibration,ThesubscriberunitmustestimatetheRxpowerproperlytomaximizesignal-to-noiseratiosandtoprovideabasisforTxpoweroutput.ThesubscriberunitmusttransmitatcorrectTxpowerleveloveritslargedynamicrange.TheMobileStationModem(MSM)deviceandsystemsoftwarecombinationmustknowtheRFandanalogcharacteristicsoftheparticularunit.FailuretocompensatefordifferingRF/analogcharacteristicsmaycausetheunittofailminimumperformancespecifications,Thecompensationvaluesareclassified:StaticRFNVitems:Measuredonceperdesign.CalculatedRFNVitems:RFNVitemsthatarecalculatedbasedonotherparametersofthedesignconfigurations.MeasuredRFNVitems:IsdeterminedbytheRFcalibrationprocess.,NVitemsofRFcalibration,RxcalibrationPhilosophyofRxAGC(AutomaticGaincontrol)loop.DVGA(DigitalVGA)offsetcalibration.LNA(LowNoiseAmplifier)offsetcalibration.,Rxcalibration(RxAGCloop),EachRxchainhasitsownreceiver.ReceivercalibrationprimarilyconsistsofmeasuringtheDVGAoffset(alsocalledVGAgainoffset)andmultipleLNAoffsets,allateachchosenfrequencyindex.Softwareloadsthefrequency-compensatedDVGAandLNAoffsetvaluesintothehardwareregistersshownabove.,PhilosophyofRxDVGAoffsetcalibration:,Rxcalibration(DVGAoffset),Rxcalibration(LNAoffset),PhilosophyofRxLNAoffsetcalibration:,Rxcalibration(LNAoffset),TxcalibrationPhilosophyofTxAGC(AutomaticGaincontrol)loop.TxLinearizerTxCompensationHDET(Highpowerdetector),Txcalibration(AGCLoop),ThetransmitterAGCmustadjusttheTxpowerlevelbasedontheRSSI,accessprobeparameters,closed-looppower-controlbits(PCBs),andchannel-configurationattributes.,Txcalibration(AGCLoop),Txcalibration(TxAGCCharacteristic),Txcalibration(TxLinearizer),Txcalibration(TX_GAIN_CTRL.),Txcalibration(HDETFeedbackloopop.),Txcompensation(1/3):,NV_BCy_TX_COMP0_INV_BCy_TX_COMP3_INV_BCy_TX_COMP0_I=CDMA_TX_COMP_VS_FREQ15:0+CDMA_TX_LIN_VS_TEMP7:0+CDMA_TX_SLP_VS_TEMP7:0,Txcalibration(TxComp.),CDMA_TX_LIN_VS_TEMP7:0:-UsedtoshifttheeffectiveTx-linearizercurvebyaconstantfortemperature-basedgainchanges.Forexample:Giventemperatureindex,theelementinthistableis0 x05,eachofthe36offsetsintheadjustedmastercurvetablewillbeincreasedbyfive,whenthetemperaturecorrespondstothatgivenindex.CDMA_TX_SLP_VS_TEMP7:0-UsedtoshifttheeffectiveTx-linearizercurvebyagraduatedamountfortemperature-basedgainchanges.Ps.typicallyallzerosunlessextraprecisionisdesired.,Txcalibration(TxComp.),High-powerdetector(HDET)(1/5):,1.OutputatthepowerleveldefinedbyTX_GAIN_CTL.2.TheHDETcircuitmeasurestheoutputpower.3.TheHDETvalueissampled.4.TablethatmapstheHDETvaluetoTxpowerlevel.TheHDETsestimatedpowerleveliscomparedtoTX_GAIN_CTLtodetermineanerrorvalue.TX_GAIN_LIMITisadjustedbythaterrorvalue.Note:OnlythemaximumpowerlimitisaffectedbytheHDETcircuit.,Txcalibration(TxHDET),HDET(2/5):,NV_BCy_TX_LIM_VS_FREQ_I:TheADCreadingsoftheHDETcircuitmayhavesomefrequencydependencies,thisNVitemcanbeusedtocompensateforsuchdependencies,Txcalibration(TxHDET),HDET(4/5):,NV_BCy_EXP_HDET_VS_AGC_I:AMSSusesthisNVitemtobuildalookuptable,whichindexesTxpowerestimationviaascaledTX_GAIN_CTL(representingthedesiredTxpower),totheassociatedHDETcircuitvaluesatreferencetemperatureandthereferencefrequency.,Procedure:,Breakuptheupper1/4ofTX_GAIN_CTLinto16segments.VarythedesiredTxpowerbymanipulatingtheTX_AGC_ADJPDM.ReadthevalueoftheHDETcircuitovereachofthe16segmentsandstoretheresultsinNV_BCy_EXP_HDET_