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1、山东理工大学毕业设计（外文翻译材料）学院：专业：学生姓名：指导教师：电气与电子工程学院电子信息工程0503应李俊苗汇静2009年6月外文翻译（原文）DIGITALFILTERSDigitalfilteringisoneofthemostpowerfultoolsofDSP.Apartfromtheobviousadvantagesofvirtuallyeliminatingerrorsinthefilterassociatedwithpassivecomponentfluctuationsovertimeandtemperature,opampdrift(activefilters),etc
2、.,digitalfiltersarecapableofperformancespecificationsthatwould,atbest,beextremelydifficult,ifnotimpossible,toachievewithananalogimplementation.Inaddition,thecharacteristicsofadigitalfiltercanbeeasilychangedundersoftwarecontrol.Therefore,theyarewidelyusedinadaptivefilteringapplicationsincommunicatio
3、nssuchasechocancellationinmodems,noisecancellation,andspeechrecognition.Theactualprocedurefordesigningdigitalfiltershasthesamefundamentalelementsasthatforanalogfilters.First,thedesiredfilterresponsesarecharacterized,andthefilterparametersarethencalculated.Characteristicssuchasamplitudeandphaserespo
4、nsearederivedinthesameway.Thekeydifferencebetweenanaloganddigitalfiltersisthatinsteadofcalculatingresistor,capacitor,andinductorvaluesforananalogfilter,coefficientvaluesarecalculatedforadigitalfilter.Soforthedigitalfilter,numbersreplacethephysicalresistorandcapacitorcomponentsoftheanalogfilter.Thes
5、enumbersresideinamemoryasfiltercoefficientsandareusedwiththesampleddatavaluesfromtheADCtoperformthefiltercalculations.Thereal-timedigitalfilter,becauseitisadiscretetimefunction,workswithdigitizeddataasopposedtoacontinuouswaveform,andanewdatapointisacquiredeachsamplingperiod.Becauseofthisdiscretenat
6、ure,datasamplesarereferencedasnumberssuchassample1,sample2,sample3,etc.Figure1showsalowfrequencysignalcontaininghigherfrequencynoisewhichmustbefilteredout.ThiswaveformmustbedigitizedwithanADCtoproducesamplesx(n).Thesedatavaluesarefedtothedigitalfilter,whichinthiscaseisalowpassfilter.Theoutputdatasa
7、mples,y(n),areusedtoreconstructananalogwaveformusingalowglitchDAC.Digitalfilters,however,arenottheanswertoallsignalprocessingfilteringrequirements.Inordertomaintainreal-timeoperation,theDSPprocessormustbeab
