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ID:39714760
大小:3.28 MB
页数:229页
时间:2019-07-09
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1、chapter1IntroductiontoDigitalSignalProcessingandDigitalFilteringIntroductiontoDigitalSignalProcessingandDigitalFiltering1.1IntroductionDigitalsignalprocessing(DSP)referstoanythingthatcanbedonetoasignalusingcodeonacomputerorDSPchip.Toreducecertainsinusoidalfr
2、equencycomponentsinasignalinamplitude,digitalfilteringisdone.Onemaywanttoobtaintheintegralofasignal.Ifthesignalcomesfromatachometer,theintegralgivestheposition.Ifthesignalisnoisy,thenfilteringthesignaltoreducetheamplitudesofthenoisefrequenciesimprovessignalq
3、uality.Forexample,noisemayoccurfromwindorrainatanoutdoormusicpresentation.Filteringoutsinusoidalcomponentsofthesignalthatoccuratfrequenciesthatcannotbeproducedbythemusicitselfresultsinrecordingthemusicwithlittlewindandrainnoise.Sometimesthesignaliscorruptedn
4、otbynoise,butbyothersignalfrequenciesthatareofnopresentinterest.Ifthesignalisanelectronicmeasurementofabrainwaveobtainedbyusingprobesappliedexternallytothehead,otherelectronicsignalsarepickedupbytheprobes,butthephysicianmaybeinterestedonlyinsignalsoccurringa
5、taparticularfrequency.Byusingdigitalfiltering,thesignalsofinterestonlycanbepresentedtothephysician.1.2HistoricalPerspectiveOriginallysignalprocessingwasdoneonlyonanalogorcontinuoustimesignalsusinganalogsignalprocessing(ASP).Untilthelate1950sdigital1DigitalSi
6、gnalProcessingcomputerswerenotcommerciallyavailable.Whentheydidbecomecommerciallyavailabletheywerelargeandexpensive,andtheywereusedtosimulatetheperformanceofanalogsignalprocessingtojudgeitseffectiveness.Thesesimulations,however,ledtodigitalprocessorcodethats
7、imulatedorperformednearlythesametaskonsamplesofthesignalsthattheanalogsystemsdidonthesignal.AfterawhileitwasrealizedthatthesimulationcodingoftheanalogsystemwasactuallyaDSPsystemthatworkedonsamplesoftheinputandoutputatdiscretetimeintervals.Buttoimplementsigna
8、lprocessingdigitallyinsteadofusinganalogsystemswasstilloutofthequestion.Thefirstproblemwasthatananaloginputsignalhadtoberepresentedasasequenceofsamplesofthesignal,whichwerethenconvertedtothecomp
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