误码测试基础PPT演示课件

误码测试基础,AnritsuCompanyLTD.MarketingDept.,内容提要,误码测试图案误码仪和示波器误码测量的同步用误码仪进行幅度/相位冗余测量测量部分时间的误码突发信号误码测量抖动测量,ATestPatternisthePre-DefinedsequenceofBitsoutputbyaPulsePatternGenerator(PPG),storedasreferenceintheErrorDetector(ED)Therearetwocategoriesoftestpatterns:Pre-DefinedTestPatternsPRBSVariableMarkRatioQuasi-PRBSZeroSubstitutionUser-DefinedTestPatternsProgrammed(PRGM)AlternatingMixed,误码测试图案,PRBS图案,Pseudo-RandomBinarySequencearepre-definedtestpatternsusedtoassesstheperformanceofdigitaltransmissionequipment.,Pseudo-RandomBinarySequencesarethemostcommonlyusedtypeofBERTtestpattern.PRBSpatternsaredesignedtoSimulateRealTrafficPRBSpatternshavea2n-1LengthMostCommonnvaluesare7,9,11,15,20,23,31TheyareITUdefinedpatternsandarerecognizedthroughoutthetelecomindustryPRBSpatternsaregeneratedwithShiftRegisterstages,XORgatesContains2n-1numberofONEsand2n-1-1numberofZEROs,PRBSSpectralContent,PRBSnvalue(PatternLength)effectsSpectralContent,BitRate,PatternRepetitionFrequencyBitRate/(#ofBitsinPattern),Frequency,Power,1,1,1,1,1,1,1,1,1,0,1,0,0,0,0,0,0,0,0,0,PatternRepetitionPeriod=(#ofBitsinPattern)xBitPeriod=(#ofBitsinPattern)/BitRate,TheHigherthenValue,theSmallertheSpectralLineSpacing,Note:NumberofSpectrafrom0HztoBitRate=2n-1,PRBSSpectralContent,Spectrumof215-1Patternat1Gbit,Nullsat1G,2G,etc.,PRBSSpectralContent,Example1:10GRate,215-1PatternSpectralLineSpacing=10G/32,767=305,185HzExample2:10GRate,231-1PatternSpectralLineSpacing=10G/2,147,483,647=4.65HzLongerPRBSPatternshaveGreaterSpectralContent.TheyContainLowerFrequencyComponents.Therefore,LongerPatternsaremoreStressful.,215-1PRBSSpectralContent,Spectrumof215-1Patternat10Gbit,SpectralSpacingisapprox.305kHz,231-1PRBSSpectralContent,Spectrumof231-1Patternat10Gbit,SpectralSpacingisapprox.5Hz,27-1PRBSPattern,1,2,3,4,5,6,7,27-1127bitslong,GenerationPolynomial:1+x6+x7,0000001000001100001010001111001000101100111010100111110100001110001001001101101011011110110001101001011101110011001010101111111,1stBitSent,17thBitSent,7Consecutive1s,6Consecutive0s,Repeat1stBit,64“1”63“0”,29-1,211-1PRBSPatterns,1,2,3,4,5,6,7,8,9,1,2,3,9,10,11,29-1511bitslong,GenerationPolynomial:1+x5+x9,211-12047bitslong,GenerationPolynomial:1+x9+x11,215-1,220-1PRBSPatterns,1,2,3,13,14,15,1,2,3,4,19,20,215-132,767bitslong,GenerationPolynomial:1+x14+x15,220-11,048,575bitslong,GenerationPolynomial:1+x3+x20,223-1,231-1PRBSPatterns,1,2,18,19,20,21,22,1,2,3,30,31,223-18,388,607bitslong,GenerationPolynomial:1+x18+x23,231-12,147,483,647bitslong,GenerationPolynomial:1+x28+x31,23,28,29,PRBSforTestingMUX,PRBSPatternshaveaPropertyUsefulforTestingBitInterleavedMUXCircuits:MParallelPRBSpatternscanbecombinedtogivethesamePRBSpattern.Thepatternsmustbetimedelayedwithrespecttoeachotherby(PatternLength/M)bits,Bit1,2n-1Pattern,LeadingBitsi.e.1/4Pattern,4:1MUX,1,2,3,4,2n-1PatternOutput,PRBSforMUXTesting,0000001000001100001010001111001000101100111010100111110100001110001001001101101011011110110001101001011101110011001010101111111,Example:8:1MUX,PatternDownColumns,SameasPatternAcrossRows,Channel8Input,Channel1Input7/8PatternDelayw.r.tChannel8,PRBSforDEMUXTesting,4:1DEMUX,1,2,3,27-1,27-1,Example:27-1,PRBSPatternshaveausefulpropertyfortestingBitInterleavedDEMUXcircuits:WhenPRBSPatternsareDEMUXedbyaBitInterleaveDEMUXCircuit,eachDEMUXChannelCarriesthecompleteinputPRBSPattern,staggeredwithrespecttoeachother.,27-1,27-1,27-1,1/4PatternShift,4,EachDEMUXChannelcarriestheSAMEPATTERN!,0000001000001100001010001111001000101100111010100111110100001110001001001101101011011110110001101001011101110011001010101111111,Example:16:1DEMUX,PatternDownColumns,SameasPatternAcrossRows,Channel1Output15/16PatternDelayw.r.t.Channel16,PRBSforDEMUXTesting,Non-PRBSPatternforTestingDEMUX,ANon-PRBSPattern(example:User-DefinedPattern)mayresultinDEMUXchannelsthatcarryNon-RandomDATA.,4:1DEMUX,1,2,3,4,01011010,00000000,10111111,10110100,11000001110011010101110001010100,Example:UserDefined32bitPattern,Channel2and3haveNon-RandomDATA,EachDEMUXChannelcarriesaDIFFERENTPATTERN!,VariableMarkRatioQuasi-PRBS,VariableMarkRatioCanBeAdjustedtoCreatePatternswithHighONEsDensityorHighZerosDensityPurposeistostresstheDevicesUnderTest(DUT)VariableMarkRatioPRBSarenotStandardPRBSPatternsDerivedfromStandardPRBSpatternsVariableMarkRatiopatternsareimplementedbyaddingoneormoreANDgatesattheoutputofthestandardPRBSpatterngenerationcircuitry.ThemostcommonavailableMarkRatiosare1/8,1/4,3/4and7/8.Agivenmarkratiocanbegeneratedusingeithera1BitShiftedor3BitShiftedtechnique.,Realizationof1/4MarkRatioQuasi-PRBS,StandardPRBSPatternGenerator,1,2,3,4,5,6,1/2MarkRatio,1/4MarkRatio(1bitShift),StandardPRBSPatternGenerator,1,2,3,4,5,6,1/2MarkRatio,1/4MarkRatio(3bitShift),Realizationof1/4MarkRatiowith1BitShift,Realizationof1/4MarkRatiowith3BitShift,3/4MarkRatioisAchievedbyInverting1/8MarkRatioPattern,Exampleof1/4MarkRatioQuasi-PRBS,0000000000000000000000000001001000000100100010000100110100000000000001001001101001011010110000001001001001100010001000000101111,0000000000000100000000000111000000001000110000000011110000000110000000000100100001001110010000100000001100110001000000000111111,27-11/4MarkRatio1BitShift,27-11/4MarkRatio3BitShift,32ONEs,95ZEROsNo101Patterns,32ONEs,95ZEROsContains101Patterns,Exampleof1BitShiftand3BitShift1/4MarkRatioPattern,Realizationof1/8MarkRatioQuasi-PRBS,StandardPRBSPatternGenerator,1,2,3,4,5,6,1/2MarkRatio,1/8MarkRatio(1bitShift),1/2MarkRatio,1/8MarkRatio(3bitShift),Realizationof1/8MarkRatiowith1BitShift,Realizationof1/8MarkRatiowith3BitShift,StandardPRBSPatternGenerator,1,2,3,4,5,6,7/8MarkRatioisAchievedbyInverting1/8MarkRatioPattern,1/2MarkRatio,231-1Pattern,10Grate,EyeDiagramof1/2MarkRatioPRBS,1/8MarkRatio,231-1Pattern,10Grate,EyeDiagramof1/8MarkRatioQuasi-PRBS,7/8MarkRatio,231-1Pattern,10Grate,EyeDiagramof7/8MarkRatioQuasi-PRBS,ZeroSubstitutionPatterns,2nbits,TheZeroSubstitution(ZS)patternissimilartoastandardPRBSpattern,butitcontainsalongermaximumstringofconsecutiveZEROS(longerthann-1).LengthofZEROstringisVariableThepatternsarenotimplementedusingthestandardPRBSpatterngenerationcircuitry.Rather,theyarepre-storedinsystemmemory.Memoryresolutionrestrictionsrequirethatthepatternbeanevenlength.ZeroSubstitutionPatternsdesignedforTestingClockRecoveryCircuitsCanbeinvertedtogiveConsecutiveONEsstring,Exampleof27ZeroSubstitutionPattern,0000001000001100001010001111001000101100111010100111110100001110001001001101101011011110110001101001011101110011001010101111111,00000000001011000010100011110010001011001110101001111101000011100010010011011010110111101100011010010111011100110010101011111111,Exampleof27ZeroSubPatternwithstringof10ConsecutiveZEROs,Addsanextra1atendofpattern,Standard27-1PRBSPattern,ZeroSubstitutionPatternApplication,TestingClockRegenerationofaNetworkElementReceiver,Pre-amplifier,RetimedData,3RRepeater,VariableZEROSubstitution,DecisionCircuit,ErrorDetector,PPG,Clock,TheusercandeterminetheZEROstringlengthwhichcausesthePLLcircuitintheCDRtoloselock.,Programmed(User-Defined)Pattern,ProgrammedorUser-Definedpatternsaredictatedbytheuser.Typically,userswillprogrampatternsthatemulatepopulartransmissionprotocols,including:SONETATMIPGigabitEthernetProgrammedpatternscanbemanuallyenteredonthefrontpaneloftheBERTordownloadedviaGPIBorfloppydisk.,ProgrammedSONETFrames,TofacilitatethedownloadingoflengthySONETframes,AnritsudevelopedaccessorySONETFrameEditorsoftware.ThissoftwarehasDefaultSONETOverhead,PayloadTypically,UserChangesonlyaFewBytesThe#ofSONETFramesthatcanbedownloadedislimitedbyBERTMemorySize8MbitCanHold6OC-192Frames,26OC-48Frames,BERT,DirectTransferviaGPIB,IndirectTransferviaFloppyDisk,ProgrammedEthernetFrames,AlternatingPatterns,AlternatingPatternsareaspecialclassofUser-Definedpatternthatoutputstwoindependent(differentcontent)AandBpatterns.NumberofRepetitionsisSettablebytheuser.,A,A,A,B,B,A,A,B,A,B,B,A,A,A,B,A,B,A,B,B,A:1Repetition,B:1Repetition,A:3Repetitions,B:2Repetitions,AlternatingPatternApplication,AnapplicationforAlternatingPatternmodeistheverificationofaSONETreceiversabilitytocorrectlydetectalarms.ExampleApplication:OC-192OOFAlarmStressTestPattern“A”containsanOC-192FramewithgoodframingCharacteristicsPattern“B”containsanOC-192Framewithbiterrorsintheframing,ThisTransmittedOC-192PatternwillGenerateanOOFConditioninaNetworkelement.,GoodFraming3Repetitions,AAA,BBBBB,AAA,AbnormalFraming5Repetitions,GoodFraming3Repetitions,MixedPattern,MixedPatternsareaCombinationofUserPatternsandPRBSPatterns.UsefulforGeneratingSONET,ATM,IP,andothercomplexProtocolTestSequencesOverheadisgeneratedwithProgrammablePattern(PRGM)PayloadissimulatedwithPRBSPatternCanInterleaveMultipleBlocksofPRGMandPRBSPatterns,PRGM,PRBS,PRGM,PRBS,MixedTestPattern,Summary,TherearetwotypesofTestPatterns:Pre-DefinedTestPatternsPRBSVariableMarkRatioQuasi-PRBSZeroSubstitutionUser-DefinedTestPatternsProgrammed(PRGM)AlternatingMixedTestpatternsaredesignedtotesttheperformanceofNetworkElements.,UsingBERTswithOscilloscope,BERTsProvideTwoTypesofScopeTriggerOutputs:Sub-RateClockOutputforGeneratingEyeDiagramsExample:1/64Clock,1/8ClockPatternTriggerforViewingIndividualBitSequencesorPulseTrainsFixedPosition:TriggeralignswithBit1ofPatternVariablePosition:TriggeroccursatUser-SelectedBitPositioninPatternAnritsuprovidesTriggerOutputsonboththePPGandED,TriggerOut,DATAOut,Oscilloscope,BERT,BERTScopeTriggersTimingDiagram,DATA,1/64Clock,FixedPosition,VariablePosition,Shiftednx16bits,PatternLength,Trigger,Trigger,Trigger,Trigger,Trigger,Trigger,Trigger,1/64Clockprovides1TriggerEvery64BitsFixedonlypriorknowledgeofthepatternlengthisrequired.Synctimesareveryrapid,ontheorderofusfor10Gbitrates.QuickSyncisusefulforsynconlongpatterns(100kBit)andBurstData.AvailableforUserandZeroSubstitutionPatternsUsewithCautionCangivemisleadingresults,QuickSync,1111000010100101111100001010010111110000.,Step1:EnterPatternLength,N,intoErrorDetectorStep2:SelectQuickSyncStep3:ErrorDetectorCapturesnextNbitsandstoresthemastheReferencePatternStep4:ErrorDetectorComparesNextNIncomingDataBitsandComparesthemtoReference,StoredasReferencePattern,ComparedtoReferencePattern,ErrorDetector,Example:N=16,MarginMeasurements,ThresholdandPhaseMarginmeasurementsareimportantforpredictingsystemperformance.Generally,thehigherthemargins,thelowerthesystemBER.ThreeTypesofMarginMeasurementscanbemadeAUTOMATICALYwithBERTs:MarginataDecisionPointEyeContourMaps*QMeasurements*,*BERTMayrequireexternalsoftwaretogenerateEyeContourandQMeasurement.MP1763/6412.5GBERTrequiresMX2210Aaccessorysoftware,MarginataDecisionPoint,AllAnritsuBERTsProvideAutomaticMarginataSingleDecisionPointmeasurementsThismeasurementprovidesafastanddirtyassessmentofthemargin.Testingtimeistypically10seconds.MeasurementProcedure:Pre-SelectDecisionPointbyadjustingThresholdandDelay.SelectErrorRateCriteriaSelectMarginMeasurementStartBERTAutomaticallyAdjustsThresholdUp/Down,DelayLeft/RighttoDetermineMarginValuesThresholdMarginisgiveninUnitsofmVpp,PhaseMarginisgiveninUnitsofpsppMeasurementtakesabout10seconds,BER=1E-9,PhaseMargin,VoltageMargin,DecisionPoint,Example1:10GbitRate,1VppDATAInputVoltageMargin=720mVpp1E-9PhaseMargin=80pspp1E-9,MarginataDecisionPoint,MarginataDecisionPoint,BER=1E-9,VoltageMargin,DecisionPoint,Example2:10GbitRate,1VppDATAInputVoltageMargin=600mVpp1E-9PhaseMargin=70pspp1E-9,PhaseMargin,NOTE:MarginmeasurementcanbeoflimitedvalueifDecisionPointisnotneartheeyecenter,EyeContourMaps,EyeContourMapsareAnExtensiontoMarginataDecisionPointMeasurements.MultipleMarginmeasurementsaretaken,creatingaContourMeasurementProcedure:SetInitialDecisionPoint.PositionisnotCriticalSelectNumberofContourstobeplotted(numberofErrorRates)SelectPhaseAdjustmentResolutioninps.ThisdeterminesthenumberofpointsincontourPressStartForagivenPhaseValue,ThresholdIsAdjustedUp/DownuntilreachingthedesignatedErrorRate.PlotPointsRepeatThresholdAdjustmentProcessatdifferentPhaseValuesMeasurementTimeDependsonBitRate,PhaseAdjustmentResolution,NumberofContours,EyeContourMap,BER=1E-6,BER=1E-4,BER=1E-9,SelectableErrorRateRangeis1E-4to1E-12in12.5GBERTsoftware.LowerErrorRatestakelongertimetocomplete.,EyeContourMapMeasurementExample,BER=1E-4,BER=1E-6,PhaseAdjustmentRes.,Conditions:10Gbits,2Vpp,0VOffset,231-1PRBS,QFactorMeasurements,QFactorisaQuantitativeMeasureoftheQualityoftheEye.TheHighertheQ,theLessNoiseontheUpperandLowerRails.TheQfactorisUsefulforpredictingveryLowErrorRates.MeasurementProcedure:Pre-SelectaDecisionPointHoldPhaseConstant.AdjustThresholdUpward.PlotBERvs.Thresholdvaluesinrange1E-5to1E-10.CurveFittoGenerateUpperRailBERvs.ThresholdLine.AdjustThresholdDownward.GenerateLowerRailBERvs.ThresholdLineCalculate1,0,1,0Q=20Log(1-0)/(1+0)Measurementtakesafewminutes,QFactorMeasurementExample,QFactor,LowerRailBERvs.Threshold,UpperRailBERvs.Threshold,DataTakenwithMX176400AandMP1763C/64CBack-to-Back,Conditions:10Gbits,2Vpp,0VOffset,231-1PRBS,AutoSearch,AutoSearchisanErrorDetectorFunctionwhichautomaticallyLocatestheCenteroftheEyeAutosearchautomaticallyAdjustsbothThresholdandPhaseAutoSearchTimeisabout10SecondsProvidesgoodFirstCutDecisionPointValues.MAYNOTFINDOPTIMUMCENTER,especiallyifthereisasymmetryistheEyeShape.ManualAdjustmentwillprovidebetterresults.ThresholdLocationisdeterminedbyPeaktoPeakDetectionCircuit.MeasurePeakPeakVoltageofIncomingSignal,divideby2.PhaseLocationisdeterminedbyCrossoverDetectionCircuit.Measuredifferencebetweenadjacentcrossoverpeaks,divideby2.,AutoSearch,PeaktoPeakDetection,CrossoverPointDetection,V2,V1,T1,T2,AutoSearchThreshold=(V2-V1)/2AutoSearchPhase=(T2-T1)/2,AutoSearchResult,AutoSearchLimitations,AutoSearchResult,OptimumDecisionPoint,Example:AsymmetricEyeduetoNoiseonUpperRail,Masking,MaskingreferstoselectingportionsofapatternthatwillbeignoredinmeasuringBER.Maskscanbeusefulfortrackingdownpatterndependenterrors.Theusercanaccesstheportionsofthepatternthatarecontributingtoerrors.TwoTypesofMasksBlockMask:MasksagroupofconsecutiveBits.For12.5GBERT,theBlockMaskis32bits.BitMask:MasksoneoutofeveryNbits.For12.5GBERT,N=32.MultipleBlockMasksandBitMaskscanbeusedSimultaneously,allowingusertoMaskallbut1bit.,01011011111101101100110010100010101110100110101011101000110101101000011001010011011011100010110100101111111100011011101001010011,BlockMaskExample,BlockMaskExample:128BitPatternLengthMaskAppliedtoBits65to96,IncomingDATA,Ref.Pattern,MASKON:MeasuredErrorCount=2MeasuredErrorRate=2/96=2.1E-2,MASKOFF:MeasuredErrorCount=6MeasuredErrorRate=6/128=4.7E-2,IncomingDATA,BitWindowExample,BitMaskExample:128BitPatternLengthMaskAppliedtoBits2,34,66,98,Ref.Pattern,MASKON:MeasuredErrorCount=1MeasuredErrorRate=1/124=8.1E-3,MASKOFF:MeasuredErrorCount=4MeasuredErrorRate=4/128=3.1E-2,01011011111101101100110010100010101110100110101011101000110101101000011001010011011011100010110100101111111100011011101001010011,00010011111101101100110010100010111110100110101011101000110101101100011001010011011011100010110100101111111100011011101001010011,1011101000110,01101,BurstMeasurements,Non-ContinuousDATAiscalledBurstData,IntoErrorDetector,IntoErrorDetector,ContinuousDATA.steadystreamof1sand0s,BurstDATA.Intervalswithno1sand0s,DATAPresent,NoDATAPresent,0101101111110110110011001010001010111010011010101110100011,BurstMeasurements,TheErrorDetectorMustBeToldwhenDATAisPresent.ABurstInputTriggerisRequired.TheBurstTriggerstaysHighDuringDurationofDATA(minusafewstoavoidtransients)TheErrorDetectorMustRe-SyncforeachBurstPulse.ValidBERMeasurementscannotbeginuntilafterSync.Re-SyncTimesmustbeFasttoAvoidMissingtoomuchDATA.,BurstMeasurements,896s,2s,100s,2s,ValidBERMeasurement,AutomaticMasktoAvoidRisingEdgeTransients,Sync,DATABurst,BurstTrigger,TriggerPulseNarrowedtoAvo