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1、DigitalSignalProcessinDigitalSignalProcessingFundamentalsgFundamentalsOverviewWhatisDSP?ConvertingAnalogintoDigitalElectronicallyComputationallyHowDoesItWork?FaithfulDuplicationResolutionTrade-offsWhatisDSP?Convertingacontinuouslychangingwaveform(analog)intoaseriesofdiscretelevels(digital)WhatisDSP?
2、TheanalogwaveformisslicedintoequalsegmentsandthewaveformamplitudeismeasuredinthemiddleofeachsegmentThecollectionofmeasurementsmakeupthedigitalrepresentationofthewaveformWhatisDSP?ConvertingAnalogintoDigitalElectronicallyThedevicethatdoestheconversioniscalledanAnalogtoDigitalConverter(ADC)Thereisadev
3、icethatconvertsdigitaltoanalogthatiscalledaDigitaltoAnalogConverter(DAC)ConvertingAnalogintoDigitalElectronicallyThesimplestformofADCusesaresistanceladdertoswitchintheappropriatenumberofresistorsinseriestocreatethedesiredvoltagethatiscomparedtotheinput(unknown)voltageConvertingAnalogintoDigitalElect
4、ronicallyTheoutputoftheresistanceladderiscomparedtotheanalogvoltageinacomparatorWhenthereisamatch,thedigitalequivalent(switchconfiguration)iscapturedConvertingAnalogintoDigitalComputationallyTheanalogvoltagecannowbecomparedwiththedigitallygeneratedvoltageinthecomparatorThroughatechniquecalledbinarys
5、earch,thedigitallygeneratedvoltageisadjustedinstepsuntilitisequal(withintolerances)totheanalogvoltageWhenthetwoareequal,thedigitalvalueofthevoltageistheoutcomeConvertingAnalogintoDigitalComputationallyThebinarysearchisamathematicaltechniquethatusesaninitialguess,theexpectedhigh,andtheexpectedlowinas
6、implecomputationtorefineanewguessThecomputationcontinuesuntiltherefinedguessmatchestheactualvalue(oruntilthemaximumnumberofcalculationsisreached)ThefollowingsequencetakesyouthroughabinarysearchcomputationBinarySearchInitialconditionsExpectedhigh5-voltsExpectedlow0-volts5-volts256-binary0-volts0-bina
7、ryVoltagetobeconverted3.42-voltsEquatesto175binaryAnalogDigital5-volts2560-volts02.5-volts1283.42-voltsUnknown(175)BinarySearchBinarysearchalgorithm:FirstGuess:AnalogDigital5-volts2560-volts01283.42-voltsunknownGuessisLowBinarySearchNewGuess(2):AnalogDigital5-volts2560-volts01923.42-voltsunknownGues
8、sisHighBinarySearchNewGuess(3):AnalogDigital5-volts2560-volts01603.42-voltsunknownGuessisLowBinarySearchNewGuess(4):AnalogDigital5-volts2560-volts01763.42-voltsunknownGuessisHighBinarySearchNewGuess(5):AnalogDigital5-volts2560-volts01683.42-voltsunknownGuessisLowBinarySearchNewGuess(6):AnalogDigital
9、5-volts2560-volts01723.42-voltsunknownGuessisLow(butgettingclose)BinarySearchNewGuess(7):AnalogDigital5-volts2560-volts01743.42-voltsunknownGuessisLow(butgettingreally,really,close)BinarySearchNewGuess(8):AnalogDigital5-volts2560-volts03.42-volts175!GuessisRightOnBinarySearchThespeedthebinarysearchi
10、saccomplisheddependson:TheclockspeedoftheADCThenumberofbitsresolutionCanbeshortenedbyagoodguess(butusuallyisnotworththeeffort)HowDoesItWork?FaithfulDuplicationNowthatwecansliceupawaveformandconvertitintodigitalform,letstakealookathowitisusedinDSPDrawasimplewaveformongraphpaperScaleappropriately“Gath
11、er”digitaldatapointstorepresentthewaveformStartingWaveformUsedtoCreateDigitalDataHowDoesItWork?FaithfulDuplicationSwapyourwaveformdatawithapartnerUsingthedata,recreatethewaveformonasheetofgraphpaperWaveformCreatedfromDigitalDataHowDoesItWork?FaithfulDuplicationComparetheoriginalwiththerecreating,not
12、esimilaritiesanddifferencesHowDoesItWork?FaithfulDuplicationOncethewaveformisindigitalform,therealpowerofDSPcanberealizedbymathematicalmanipulationofthedataUsingEXCELspreadsheetsoftwarecanassistinmanipulatingthedataandmakinggraphsquicklyLetsfirstdoalittlefilteringofnoiseHowDoesItWork?FaithfulDuplica
13、tionUsingyourrawdigitaldata,createanewtableofdatathataveragesthreedatapointsAveragethepointbeforeandthepointafterwiththepointinthemiddleEnteralldatainEXCELtohelpwithgraphingNoiseFilteringUsingAveragingHowDoesItWork?FaithfulDuplicationLetstakecareofsomestaticcrashesthatcausesomeinterferenceUsingyourr
14、awdigitaldata,createanewtableofdatathatreplacesextremehighandlowvalues:Replacevaluesgreaterthan100with100Replacevalueslessthan-100with-100ClippingofStaticCrashesHowDoesItWork?ResolutionTrade-offsNowletstakealookathowsamplingratesaffectthefaithfulduplicationofthewaveformUsingyourrawdigitaldata,create
15、anewtableofdataanddeleteeveryotherdatapointThisisthesameassamplingathalftherateHalfSampleRateHowDoesItWork?ResolutionTrade-offsUsingyourrawdigitaldata,createanewtableofdataanddeleteeverysecondandthirddatapointThisisthesameassamplingatone-thirdtherate1/2SampleRateHowDoesItWork?ResolutionTrade-offsUsi
16、ngyourrawdigitaldata,createanewtableofdataanddeleteallbuteverysixthdatapointThisisthesameassamplingatone-sixththerate1/6SampleRateHowDoesItWork?ResolutionTrade-offsUsingyourrawdigitaldata,createanewtableofdataanddeleteallbuteverytwelfthdatapointThisisthesameassamplingatone-twelfththerate1/12SampleRa
17、teHowDoesItWork?ResolutionTrade-offsWhatconclusionscanyoudrawfromthechangesinsamplingrate?Atwhatpointdoesthewaveformgettoocorruptedbythereducednumberofsamples?Isthereapointwheremoresamplesdoesnotappeartoimprovethequalityoftheduplication?HowDoesItWork?ResolutionTrade-offsBitResolutionHighBitCountGoodDuplicationSlowLowBitCountPoorDuplicationFastSampleRateHighSampleRateGoodDuplicationSlowLowSampleRatePoorDuplicationFast
