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1、DigitalSignalProcessing(DSP)FundamentalsOverviewWhatisDSP?ConvertingAnalogintoDigitalElectronicallyComputationallyHowDoesItWork?FaithfulDuplicationResolutionTrade-offsWhatisDSP?Convertingacontinuouslychangingwaveform(analog)intoaseriesofdiscretelevels(digital)WhatisDSP?Theanalogwaveformisslicedintoe
2、qualsegmentsandthewaveformamplitudeismeasuredinthemiddleofeachsegmentThecollectionofmeasurementsmakeupthedigitalrepresentationofthewaveformWhatisDSP?ConvertingAnalogintoDigitalElectronicallyThedevicethatdoestheconversioniscalledanAnalogtoDigitalConverter(ADC)Thereisadevicethatconvertsdigitaltoanalog
3、thatiscalledaDigitaltoAnalogConverter(DAC)ConvertingAnalogintoDigitalElectronicallyThesimplestformofADCusesaresistanceladdertoswitchintheappropriatenumberofresistorsinseriestocreatethedesiredvoltagethatiscomparedtotheinput(unknown)voltageConvertingAnalogintoDigitalElectronicallyTheoutputoftheresista
4、nceladderiscomparedtotheanalogvoltageinacomparatorWhenthereisamatch,thedigitalequivalent(switchconfiguration)iscapturedConvertingAnalogintoDigitalComputationallyTheanalogvoltagecannowbecomparedwiththedigitallygeneratedvoltageinthecomparatorThroughatechniquecalledbinarysearch,thedigitallygeneratedvol
5、tageisadjustedinstepsuntilitisequal(withintolerances)totheanalogvoltageWhenthetwoareequal,thedigitalvalueofthevoltageistheoutcomeConvertingAnalogintoDigitalComputationallyThebinarysearchisamathematicaltechniquethatusesaninitialguess,theexpectedhigh,andtheexpectedlowinasimplecomputationtorefineanewgu
6、essThecomputationcontinuesuntiltherefinedguessmatchestheactualvalue(oruntilthemaximumnumberofcalculationsisreached)ThefollowingsequencetakesyouthroughabinarysearchcomputationBinarySearchInitialconditionsExpectedhigh5-voltsExpectedlow0-volts5-volts256-binary0-volts0-binaryVoltagetobeconverted3.42-vol
7、tsEquatesto175binaryAnalogDigital5-volts2560-volts02.5-volts1283.42-voltsUnknown(175)BinarySearchBinarysearchalgorithm:FirstGuess:AnalogDigital5-volts2560-volts01283.42-voltsunknownGuessisLowBinarySearchNewGuess(2):AnalogDigital5-volts2560-volts01923.42-voltsunknownGuessisHighBinarySearchNewGuess(3)
8、:AnalogDigital5-volts2560-volts01603.42-voltsunknownGuessisLowBinarySearchNewGuess(4):AnalogDigital5-volts2560-volts01763.42-voltsunknownGuessisHighBinarySearchNewGuess(5):AnalogDigital5-volts2560-volts01683.42-voltsunknownGuessisLowBinarySearchNewGuess(6):AnalogDigital5-volts2560-volts01723.42-volt
9、sunknownGuessisLow(butgettingclose)BinarySearchNewGuess(7):AnalogDigital5-volts2560-volts01743.42-voltsunknownGuessisLow(butgettingreally,really,close)BinarySearchNewGuess(8):AnalogDigital5-volts2560-volts03.42-volts175!GuessisRightOnBinarySearchThespeedthebinarysearchisaccomplisheddependson:Thecloc
10、kspeedoftheADCThenumberofbitsresolutionCanbeshortenedbyagoodguess(butusuallyisnotworththeeffort)HowDoesItWork?FaithfulDuplicationNowthatwecansliceupawaveformandconvertitintodigitalform,letstakealookathowitisusedinDSPDrawasimplewaveformongraphpaperScaleappropriately“Gather”digitaldatapointstorepresen
11、tthewaveformStartingWaveformUsedtoCreateDigitalDataHowDoesItWork?FaithfulDuplicationSwapyourwaveformdatawithapartnerUsingthedata,recreatethewaveformonasheetofgraphpaperWaveformCreatedfromDigitalDataHowDoesItWork?FaithfulDuplicationComparetheoriginalwiththerecreating,notesimilaritiesanddifferencesHow
12、DoesItWork?FaithfulDuplicationOncethewaveformisindigitalform,therealpowerofDSPcanberealizedbymathematicalmanipulationofthedataUsingEXCELspreadsheetsoftwarecanassistinmanipulatingthedataandmakinggraphsquicklyLetsfirstdoalittlefilteringofnoiseHowDoesItWork?FaithfulDuplicationUsingyourrawdigitaldata,cr
13、eateanewtableofdatathataveragesthreedatapointsAveragethepointbeforeandthepointafterwiththepointinthemiddleEnteralldatainEXCELtohelpwithgraphingNoiseFilteringUsingAveragingHowDoesItWork?FaithfulDuplicationLetstakecareofsomestaticcrashesthatcausesomeinterferenceUsingyourrawdigitaldata,createanewtableo
14、fdatathatreplacesextremehighandlowvalues:Replacevaluesgreaterthan100with100Replacevalueslessthan-100with-100ClippingofStaticCrashesHowDoesItWork?ResolutionTrade-offsNowletstakealookathowsamplingratesaffectthefaithfulduplicationofthewaveformUsingyourrawdigitaldata,createanewtableofdataanddeleteeveryo
15、therdatapointThisisthesameassamplingathalftherateHalfSampleRateHowDoesItWork?ResolutionTrade-offsUsingyourrawdigitaldata,createanewtableofdataanddeleteeverysecondandthirddatapointThisisthesameassamplingatone-thirdtherate1/2SampleRateHowDoesItWork?ResolutionTrade-offsUsingyourrawdigitaldata,createane
16、wtableofdataanddeleteallbuteverysixthdatapointThisisthesameassamplingatone-sixththerate1/6SampleRateHowDoesItWork?ResolutionTrade-offsUsingyourrawdigitaldata,createanewtableofdataanddeleteallbuteverytwelfthdatapointThisisthesameassamplingatone-twelfththerate1/12SampleRateHowDoesItWork?ResolutionTrad
17、e-offsWhatconclusionscanyoudrawfromthechangesinsamplingrate?Atwhatpointdoesthewaveformgettoocorruptedbythereducednumberofsamples?Isthereapointwheremoresamplesdoesnotappeartoimprovethequalityoftheduplication?HowDoesItWork?ResolutionTrade-offsBitResolutionHighBitCountGoodDuplicationSlowLowBitCountPoorDuplicationFastSampleRateHighSampleRateGoodDuplicationSlowLowSampleRatePoorDuplicationFast
