Digita Signal Processing--Filtering Approach.pd...

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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