DigitalSignalProcessingFundamentals.ppt

DigitalSignalProcessing DSP Fundamentals Overview WhatisDSP ConvertingAnalogintoDigitalElectronicallyComputationallyHowDoesItWork FaithfulDuplicationResolutionTrade offs WhatisDSP Convertingacontinuouslychangingwaveform analog intoaseriesofdiscretelevels digital WhatisDSP TheanalogwaveformisslicedintoequalsegmentsandthewaveformamplitudeismeasuredinthemiddleofeachsegmentThecollectionofmeasurementsmakeupthedigitalrepresentationofthewaveform WhatisDSP ConvertingAnalogintoDigitalElectronically ThedevicethatdoestheconversioniscalledanAnalogtoDigitalConverter ADC ThereisadevicethatconvertsdigitaltoanalogthatiscalledaDigitaltoAnalogConverter DAC ConvertingAnalogintoDigitalElectronically ThesimplestformofADCusesaresistanceladdertoswitchintheappropriatenumberofresistorsinseriestocreatethedesiredvoltagethatiscomparedtotheinput unknown voltage ConvertingAnalogintoDigitalElectronically TheoutputoftheresistanceladderiscomparedtotheanalogvoltageinacomparatorWhenthereisamatch thedigitalequivalent switchconfiguration iscaptured ConvertingAnalogintoDigitalComputationally TheanalogvoltagecannowbecomparedwiththedigitallygeneratedvoltageinthecomparatorThroughatechniquecalledbinarysearch thedigitallygeneratedvoltageisadjustedinstepsuntilitisequal withintolerances totheanalogvoltageWhenthetwoareequal thedigitalvalueofthevoltageistheoutcome ConvertingAnalogintoDigitalComputationally Thebinarysearchisamathematicaltechniquethatusesaninitialguess theexpectedhigh andtheexpectedlowinasimplecomputationtorefineanewguessThecomputationcontinuesuntiltherefinedguessmatchestheactualvalue oruntilthemaximumnumberofcalculationsisreached Thefollowingsequencetakesyouthroughabinarysearchcomputation BinarySearch InitialconditionsExpectedhigh5 voltsExpectedlow0 volts5 volts256 binary0 volts0 binaryVoltagetobeconverted3 42 voltsEquatesto175binary Analog Digital 5 volts 256 0 volts 0 2 5 volts 128 3 42 volts Unknown 175 BinarySearch Binarysearchalgorithm FirstGuess Analog Digital 5 volts 256 0 volts 0 128 3 42 volts unknown GuessisLow BinarySearch NewGuess 2 Analog Digital 5 volts 256 0 volts 0 192 3 42 volts unknown GuessisHigh BinarySearch NewGuess 3 Analog Digital 5 volts 256 0 volts 0 160 3 42 volts unknown GuessisLow BinarySearch NewGuess 4 Analog Digital 5 volts 256 0 volts 0 176 3 42 volts unknown GuessisHigh BinarySearch NewGuess 5 Analog Digital 5 volts 256 0 volts 0 168 3 42 volts unknown GuessisLow BinarySearch NewGuess 6 Analog Digital 5 volts 256 0 volts 0 172 3 42 volts unknown GuessisLow butgettingclose BinarySearch NewGuess 7 Analog Digital 5 volts 256 0 volts 0 174 3 42 volts unknown GuessisLow butgettingreally really close BinarySearch NewGuess 8 Analog Digital 5 volts 256 0 volts 0 3 42 volts 175 GuessisRightOn BinarySearch Thespeedthebinarysearchisaccomplisheddependson TheclockspeedoftheADCThenumberofbitsresolutionCanbeshortenedbyagoodguess butusuallyisnotworththeeffort HowDoesItWork FaithfulDuplication Nowthatwecansliceupawaveformandconvertitintodigitalform let stakealookathowitisusedinDSPDrawasimplewaveformongraphpaperScaleappropriately Gather digitaldatapointstorepresentthewaveform StartingWaveformUsedtoCreateDigitalData HowDoesItWork FaithfulDuplication SwapyourwaveformdatawithapartnerUsingthedata recreatethewaveformonasheetofgraphpaper WaveformCreatedfromDigitalData HowDoesItWork FaithfulDuplication Comparetheoriginalwiththerecreating notesimilaritiesanddifferences HowDoesItWork FaithfulDuplication Oncethewaveformisindigitalform therealpowerofDSPcanberealizedbymathematicalmanipulationofthedataUsingEXCELspreadsheetsoftwarecanassistinmanipulatingthedataandmakinggraphsquicklyLet sfirstdoalittlefilteringofnoise HowDoesItWork FaithfulDuplication Usingyourrawdigitaldata createanewtableofdatathataveragesthreedatapointsAveragethepointbeforeandthepointafterwiththepointinthemiddleEnteralldatainEXCELtohelpwithgraphing NoiseFilteringUsingAveraging HowDoesItWork FaithfulDuplication Let stakecareofsomestaticcrashesthatcausesomeinterferenceUsingyourrawdigitaldata createanewtableofdatathatreplacesextremehighandlowvalues Replacevaluesgreaterthan100with100Replacevalueslessthan 100with 100 ClippingofStaticCrashes HowDoesItWork ResolutionTrade offs Nowlet stakealookathowsamplingratesaffectthefaithfulduplicationofthewaveformUsingyourrawdigitaldata createanewtableofdataanddeleteeveryotherdatapointThisisthesameassamplingathalftherate HalfSampleRate HowDoesItWork ResolutionTrade offs Usingyourrawdigitaldata createanewtableofdataanddeleteeverysecondandthirddatapointThisisthesameassamplingatone thirdtherate 1 2SampleRate HowDoesItWork ResolutionTrade offs Usingyourrawdigitaldata createanewtableofdataanddeleteallbuteverysixthdatapointThisisthesameassamplingatone sixththerate 1 6SampleRate HowDoesItWork ResolutionTrade offs Usingyourrawdigitaldata createanewtableofdataanddeleteallbuteverytwelfthdatapointThisisthesameassamplingatone twelfththerate 1 12SampleRate HowDoesItWor