基于DDS和单片机数字控制信号发生器的设计外文翻译文献Word格式文档下载.docx

基于DDS和单片机数字控制信号发生器的设计外文翻译文献Word格式文档下载.docx

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Keywords:

DDS;

MCU;

Signalgenerator;

PhaseAccumulator;

DAC

Abstract.ItsadvantagetouseDDSchipisoutputsignalfrequencybigger,andprecisionhigher,Butuserscan'

tchangetheoutputsignalwaveforms.TheMCUcanproducetherequiredarbitrarywaveforms,butitsprogramexecutionoftheorderlimitthespeed.SoweusetheirSynergytodesignthedigitalcontrolledsignalgenerator.TheSystemhastheadvantageofoutputgoodqualitywaveform,frequencyofprecisionandstability,andhighfrequency,empty,amplitudeandphaseistostepintotheneed.

Introduction

Thedigitallysynthesizedsinewaveform（DirectDigitalSynthesis,DDS）isawell-knownmethodandhasbeenappliedtomanyembeddedapplications[1].Thistechniquecanbeusedtocreateapositivedigitalsinewaveform.Comparedtootherfrequencycomposingmethod,DirectDigitalFrequencySynthesis（DDS）hasbeenthemostpopulartrendinmodernfrequencysynthetictechniqueforitsexcellentcharacteristics.ThesignalsourcethattheDDStechnologyrealizescancarryoutaccuratecontrollingonDDSfrequency,extent,phaseexportingwaveform'

setc.bynumericalcontrolcircuit,thesystemmakinguseofthismethodhasmanymeritssuchasstability,reliablyandaccuracy.

ThecommercialDDSchipcanonlyexportasinewaveforthedataintheROMformalreadyhasbeensolidified.Ifneedingtocomeintobeinganywaveform,itmaycometruebythewaythatFPGAadoptsDDSIPcoreorhardwaredescribelanguageetc,however,thecostofThiswaycostishigh;

ontheotherhand,anywaveformcanbeachievedbymakinguseofmicrocontrollerunit（MCU）tocarryoutfigurefrequencycombiningandDAconverting.TheexperimentandapplyingtestinghaveshownthatthenumericalcontrolsignalsourcecomposedofSTM32microcontrollerandDDSchipcanworkwell.

DDSandwaveformprogrammingpattern

ThecoreofDDSsystemisphaseaccumulatorcarriage,anditiscomposedofaADRandone

unitphaseregister.Whenanyclockcomes,thephaseregisterincreasesbywiththesteplength,phaseregisteroutputandphasecontrolwordaddtogether,andthentheoutputisimportedtosineinquiryformaddress.

Thesineinquiringformincludesthenumeralextentinformationofone-periodsinewave,eachaddresscorrespondstothephasedotof0~360degreesofthesinewave.ThemappingdigitalsignaldrivesDACandoutputsanalogvalue.Theoutputsinecircleandfrequencyare

Thephaseregisterwillreturntotheoriginalstatewhenthe2N/Mfcclockisfinished.

Accordingly,theDDSsystemoutputasinewavewhenthesineinquiringformfinishacircle.TheoutputsinecircleandfrequencyisTO--outputsinewavecircle,unit:

s;

TC--externalreferencedclockcircle,unit:

M--accumulatedsteplengthofphaseregister,constant;

fout--outputsinewavefrequency,unit:

Hz;

fc--externalreferencedclockfrequency,unit:

N--phaseaccumulatordigit,constant.

Therelationshipamongthefrequencycontrolword,andtheoutputsignalfrequencyandthereferencedclockfrequencyare:

Frequencycontrolwordisdirectlyproportionaltotheoutputsignalfrequency.Inordertodescribeclearly,thesinewaveformisasonevectorturnsaroundphasecircle,thephasecirclematchesalongwithacyclesinewave.Everysamplingpotsinwaveformcorrespondstoaphasedotofthephasecircle.

Tosynthesistherequiredfrequencysignal,itneedstoaccomplishthefollowingsteps

1.Controllingeverysamplingincrementofphaseandaccumulatingthem（frequencycontrolwordK）,output2picumulatedphase（usingphaseaccumulator）.

2.Converting2piaccumulatingphaseintothecorrespondingsineamplitude,useROMtostorethecorrespondingphase-extentformofsinefunctioningeneral.

3.UseDACtochangeextentcodeintothesignalsimulatingvoltage.

4.ThevoltagesignalthatDACexportsisladderwaveform,therequiredsimulationvoltageoutisachievedafterLPFsmoothing.

NumericalcontrolDDSsignalsourcesystemdesignsanalysis

SystemusestheSTM32ascontrolcoreandtheAD9850asgenerator.STM32is32-bitARM-basedmicrocontrollerwith128Kbyteflashmemory.

ThetwosignaloutputofSTM32canbeachievedbycontrollingAD9850andDAC0832outputsimultaneously.ThesystemdesignsblockdiagramisshowninFig.1.Onesignaloutputcangenerate30MHzsinewaveandrectangularwavebycontrollingAD9850,theotheroutputgenerateanywaveformwithitsfrequencylessthan10KHzbynumericalfrequencymixtureofDAC0832.

Fig.1Systemdesignsblockdiagram

Hardwaredesign

AD9850module

AD9850containstheDDSsy