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1、外文文献原文：AskTheApplicationEngineer—33AllAboutDirectDigitalSynthesisByEvaMurphy,(eva.murphy@analog.com)ColmSlattery(colm.slattery@analog.com)ByAnalogDialogueVolume38Number3ofADIWhatisDirectDigitalSynthesis?Directdigitalsynthesis(DDS)isamethodofproducingananalogwaveform—usuall
2、yasinewave—bygeneratingatime-varyingsignalindigitalformandthenperformingadigital-to-analogconversion.BecauseoperationswithinaDDSdeviceareprimarilydigital,itcanofferfastswitchingbetweenoutputfrequencies,finefrequencyresolution,andoperationoverabroadspectrumoffrequencies.Wit
3、hadvancesindesignandprocesstechnology,today’sDDSdevicesareverycompactanddrawlittlepower.Whywouldoneuseadirectdigitalsynthesizer(DDS)?Aren’tthereothermethodsforeasilygeneratingfrequencies?Theabilitytoaccuratelyproduceandcontrolwaveformsofvariousfrequenciesandprofileshasbeco
4、meakeyrequirementcommontoanumberofindustries.Whetherprovidingagilesourcesoflow-phase-noisevariable-frequencieswithgoodspuriousperformanceforcommunications,orsimplygeneratingafrequencystimulusinindustrialorbiomedicaltestequipmentapplications,convenience,compactness,andlowco
5、stareimportantdesignconsiderations.Manypossibilitiesforfrequencygenerationareopentoadesigner,rangingfromphase-locked-loop(PLL)-basedtechniquesforveryhigh-frequencysynthesis,todynamicprogrammingofdigital-to-analogconverter(DAC)outputstogeneratearbitrarywaveformsatlowerfrequ
6、encies.ButtheDDStechniqueisrapidlygainingacceptanceforsolvingfrequency-(orwaveform)generationrequirementsinbothcommunicationsandindustrialapplicationsbecausesingle-chipICdevicescangenerateprogrammableanalogoutputwaveformssimplyandwithhighresolutionandaccuracy.Furthermore,t
7、hecontinualimprovementsinbothprocesstechnologyanddesignhaveresultedincostandpowerconsumptionlevelsthatwerepreviouslyunthinkablylow.Forexample,theAD9833,aDDS-basedprogrammablewaveformgenerator(Figure1),operatingat5.5Vwitha25-MHzclock,consumesamaximumpowerof30milliwatts.Figu
8、re1.TheAD9833—aone-chipwaveformgenerator.WhatarethemainbenefitsofusingaDDS?DDSdeviceslike
