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Unit9DigitalSignalProcessingPassageCComparisonofDSPandASP9单元数字信号处理C篇比较DSP和ASP学号：20107600姓名：章太元PassageCComparisonofDSPandASPSignalsmaybeprocessedusinganalogtechniques(analogsignalprocessing,orASP),digitaltechniques(digitalsignalprocessing,orDSP),oracombinationofanaloganddigitaltechniques(mixedsignalprocessing,orMSP).Insomecases,thechoiceoftechniquesisclear;inothers,thereisnoclearcutchoice,andsecond-orderconsiderationsmaybeusedtomakethefinaldecision.WithrespecttoDSP,thefactorthatdistinguishesitfromtraditionalcomputeranalysisofdataisitsspeedandefficiencyinperformingsophisticateddigitalprocessingfunctionssuchasfiltering,FFTanalysis,anddatacompressioninrealtime.信号可以用模拟技术处理（模拟信号处理，数字技术（或ASP），数字信号处理，或DSP），或一个组合的模拟和数字技术（混合信号处理，或MSP）。在某些情况下，技术的选择是明确的；在其他情况下，没有明确的选择，和二阶考虑可以用对于DSP，使得它与传统计算机数据分析是它的速度和效率，进行复杂的数字处理功能，如滤波，FFT分析，数据的实时压缩Thetermmixedsignalprocessingimpliesthatbothanaloganddigitalprocessingisdoneaspartofthesystem.Thesystemmaybeimplementedintheformofaprintedcircuitboardorasingleintegratedcircuitchip.Inthecontextofthisbroaddefinition,ADCsandDACsareconsideredtobemixedsignalprocessors,sincebothanaloganddigitalfunctionsareimplementedineach.RecentadvancesinVeryLargeScaleIntegration(VLSI)processingtechnologyallowcomplexdigitalprocessingaswellasanalogprocessingtobeperformedonthesamechip.TheverynatureofDSPitselfimpliesthatthesefunctionscanbeperformedinreal-time.术语混合信号处理意味着，模拟和数字处理系统的一部分。该系统可在印刷电路板或一个单一的集成电路芯片的形式实现。在这个广泛的定义下，ADC和DAC被认为是混合信号处理器，由于模拟和数字功能的实现在每个。在超大规模集成电路（VLSI）处理技术的进展使得复杂的数字信号处理和模拟处理的是在同一芯片上进行。DSP本身的性质意味着，这些功能可以在实时执行。ASPvs.DSPToday’sengineerfacesachallengeinselectingthepropermixofanaloganddigitaltechniquestosolvethesignalprocessingtaskathand.Itisimpossibletoprocessreal-worldanalogsignalsusingpurelydigitaltechniques,sinceallsensors(microphones,thermocouples,straingages,piezoelectriccrystals,diskdriveheads,etc.)areanalogsensors.Therefore,somesortofsignalconditioningcircuitryisrequiredinordertopreparethesensoroutputforfurthersignalprocessing,whetheritbeanalogordigital.Signalconditioningcircuitsare,inreality,analogsignalprocessors,performingsuchfunctionsasmultiplication(gain),isolation(instrumentationamplifiersandisolationamplifiers),detectioninthepresenceofnoise(highcommon-modeinstrumentationamplifiersetc.),dynamicrangecompression(logamps,LOGDACs,andprogrammablegainamplifiers),andfiltering(bothpassiveandactive).SeveralmethodsofaccomplishingsignalprocessingareshowninFigure9.5.Thetopportionofthefigureshowsthepurelyanalogapproach.ThelatterpartsofthefigureshowtheDSPapproach.NotethatoncethedecisionhasbeenmadetouseDSPtechniques,thenextdecisionmustbewheretoplacetheADCinthesignalpath.ASP与DSP今天的工程师在选择适当的混合模拟和数字技术来解决手头的信号处理任务所面临的挑战。这是不可能的真实世界的模拟信号处理采用纯数字技术，因为所有的传感器（麦克风，热电偶，应变计，压电晶体，磁盘驱动器的磁头，等）是模拟传感器。因此，某种形式的信号调理电路是为了准备传感器输出信号进一步处理，无论是模拟或数字。信号调理电路，在现实中，模拟信号处理器，如乘法执行这些功能（增益），隔离（仪表放大器和隔离放大器），在存在噪声检测（高共模仪表放大器等），动态范围压缩（对数放大器，logdacs，和可编程增益放大器），和过滤（包括被动和主动的）。完成信号处理的几种方法，如图9.5所示。图中的顶部显示纯模拟方法。图中的一部分显示的数字信号处理方法。请注意，一旦决定已经做出，采用DSP技术，未来的决定必须在什么地方ADC的信号路径。Figure9.5SomeMethodsofAccomplishingSignalProcessingIngeneral,astheADCismovedclosertotheactualsensor,moreoftheanalogsignalconditioningburdenisnowplacedontheADC.TheaddedADCcomplexitymaytaketheformofincreasedsamplingrate,widerdynamicrange,higherresolution,inputnoiserejection,inputfilteringandprogrammablegainamplifiers(PGAs),on-chipvoltagereferences,etc.,allofwhichaddfunctionalityandsimplifythesystem.Withtoday’shigh-resolution/highsamplingratedataconvertertechnology,significantprogresshasbeenmadeinintegratingmoreandmoreoftheconditioningcircuitrywithintheADC/DACitself.Inthemeasurementarea,forinstance,24-bitADCsareavailablewithbuilt-inprogrammablegainamplifiers(PGAs)whichallowfull-scalebridgesignalsof10mVtobedigitizeddirectlywithnofurtherconditioning.Atvoicebandandaudiofrequencies,completecoder-decoders(CodecsorAnalogFrontEnds)areavailablewhichhavesufficienton-chipanalogcircuitrytominimizetherequirementforexternalconditioningcomponents.Atvideospeeds,analogfrontendsarealsoavailableforsuchapplicationsasCCDimageprocessingandothers.在一般情况下，作为ADC接近实际的传感器，更多的模拟信号调理的负担，现在放在ADC。增加ADC的复杂性可以增加采样入滤波和可编程增益放大器（PGA），片上的参考电压，等等，所有这些新增功能和简化系统。今天的高分辨率、高采样率的数据转换技术，在集成越来越多的调理电路内的ADC/DAC本身取得了明显的进展。在测量领域，例如，24位ADC提供内置的可编程增益放大器（PGA）允许10MV全桥被数字化的信号编码器，完整模拟前端）可有足够的片上模拟电路，以尽量减少对外部条件的要求。在视频的速度，模拟前端也可用于CCDApracticalexampleAsapracticalexampleofthepowerofDSP,considerthecomparisonbetweenananalogandadigitallowpassfilter,eachwithacutofffrequencyof1kHz.ThedigitalfilterisimplementedinatypicalsampleddatasystemshowninFigure9.6.Notethatthere’areseveralimplicitrequirementsinthediagram.First,itisassumedthatanADC/DACcombinationisavailablewithsufficientsamplingfrequency,resolution,anddynamicrangetoaccuratelyprocessthesignal.Second,theDSPmustbefastenoughtocompleteallitscalculationswithinthesamplinginterval,1/fs.Third,analogfiltersarestillrequiredattheADCinputandDACoutputforanti-aliasingandanti-imaging,buttheperformancedemandsarenotasgreat.Assumingtheseconditionshavebeenmet,thefollowingoffersacomparisonbetweenthedigitalandanalo