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1、外文文獻(xiàn)外文文獻(xiàn)原文：原文：DDSdevicestoproducehighqualitywavefm:asimpleefficientflexibleSummaryDirectdigitalfrequencysynthesis(DDS)technologyfthegenerationregulationofhighqualitywavefmswidelyusedinmedicalindustrialinstrumentationcomm

2、unicationsdefensemanyotherareas.ThisarticlewillbrieflydescribethetechnologyonitsstrengthsweaknessesexaminesomeapplicationexamplesalsointroducedsomenewproductsthatcontributetothepromotionIntroductionAkeyrequirementinmanyi

3、ndustriesisanexactproductioneasyoperationquickchangeofdifferentfrequenciesdifferenttypesofwavefms.Whetheritisbroadbtransceiverrequireslowphasenoiseexcellentspuriousfreedynamicperfmanceofagilefrequencysourcefindustrialmea

4、surementcontrolsystemneedsastablefrequencyexcitationfasteasyeconomicaltoproduceadjustablewavefmwhilemaintainingphasecontinuitycapabilitiesarecriticaltoadesignstardwhichiswhattheadvantagesofdirectdigitalfrequencysynthesis

5、.FrequencysynthesistaskThegrowingcongestionofthespectrumcoupledwithlowerpowerconsumptionqualityofneverendingdemfhighermeasuringequipmentthesefactsrequiretheuseofthenewfrequencyrangerequiresabetteruseofexistingfrequencyra

6、nge.Aresultthesearchfbettercontrolinmostcasesbymeansoffrequencysynthesizerffrequencygeneration.ThesedevicesuseagivenfrequencyfCoftogenerateatargetfrequency(phase)fOUTthegeneralrelationshipcanbesimplyexpressedas:fOUT=εxfC

7、Amongthemthescalefactεxsometimesknownasthenmalizedfrequency.Theequationisusuallygradualapproximationoftherealnumberalgithms.Whenthescalefactisarationalnumbertworelativelyprimenumbers(outputfrequencyreferencefrequency)tha

8、ntheharmonic.HoweverinmostcasesεxmaybelongtoabroadersetofrealnumberstheapproximationprocessiswithintheacceptablerangewillbedDirectDigitalFrequencySynthesizerThefrequencysynthesizerapracticalwaytoachieveisthedirectdigital

9、frequencysynthesis(ofDDFS)usuallyreferredtoasdirectdigitalsynthesis(DDS).ThistechniqueusingdigitaldataprocessingtogenerateafrequencyphaseadjustableoutputtheoutputafixedfrequencyreferenceclocksourcefC.related.DDSarchitect

10、urethereferencethesystemclockfrequencydividedbyascalefacttoproducethedesiredfrequencythescalefactiscontrolledbythebinarytuningwdprogrammable.Inshtdirectdigitalfrequencysynthesizertoconvertabunchofclockpulsesintoananalogw

11、avefmusuallyasinewavetrianglewavesquarewave.ShowninFigure1itsmainparts:thephaseaccumulat(toproducetheoutputwavefmphaseangledata)relativetodigitalconverter(abovethephasedataisconvertedtotheinstantaneousoutputamplitudedata

12、)digitaltoanalogconverter(DAC)(themagnitudeofdataintoasampledanalogdatapoints)IntegratedinasingledeviceontheengineofaDDSaDAChasbothadvantagesdisadvantageshoweverwhetherintegratednotneedaDACtoproduceultrahighpurityhighqua

13、lityanalogsignal.DACwillconvertdigitalsinusoidaloutputtoananalogsinewavemaybesingleendeddifferential.Someofthekeyrequirementsflowphasenoiseexcellentwideb(WB)narrowb(NB)spuriousfreedynamicrange(SFDR)lowpowerconsumption.If

14、theexternaldevicetheDACmustbefastenoughtohlethesignalsothebuiltinparallelptdeviceisverycommon.DDSothersolutionsThefrequencyanalogphaselockedloops(PLLs)clockgenerattheuseofFPGAdynamicprogrammingoftheoutputoftheDAC.Byexami

15、ningthespectrumofperfmancepowerofthesetechnologiesasimplecomparisonTable1showsthequalitativeresultsofthecomparisonTable1.DDSwithcompetingtechnologiesAdvancedcomparePowerconsumptionSpectralpurityRemarksDDSLowdleEaseoftuni

16、ngDiscreteDACFPGAdledleHighWithtuningcapabilitiesAnalogPLLMilddleHighDifficulttuningPhaselockedloopisafeedbackloopitscomponents:aphasecomparatadividerapressurecontrolledoscillat(VCO)phasecomparatreferencefrequencyoutputf

17、requency(usuallytheoutputfrequencyisN)frequency)werecompared.TheerrvoltagegeneratedbythephasecomparatisusedtoadjusttheVCOthustheoutputfrequency.Whentheloopisestablishedtheoutputfrequencyphasewiththereferencefrequencytoma

18、intainapreciserelationship.PLLhaslongbeenconsideredinaparticularfrequencyrangehighfidelityconsistentsignallowphasenoisehighspuriousfreedynamicrange(SFDR)areidealfapplications.PLLcannotbepreciselyquicklytuningthefrequency

19、outputwavefmtheslowresponsewhichlimitstheirapplicabilityffastfrequencyhoppingpartofthefrequencyshiftkeyingphaseshiftkeyingapplications.OtherprogramsincludingintegratedDDSenginefieldprogrammablegatearrays(FPGAs)asynthetic

20、sinewaveoutputwiththeofftheshelfDACthoughthePLLfrequencyhoppingproblemcanbesolvedbutthereownshtcomings.Thedefectsofthemajsystemswkinterfacepowerrequirementshighcostlargesizesystemdevelopersmustalsoconsidertheadditionalso

21、ftwarehardwarememy.FexampleusingtheDDSengineoptioninthemodernFPGAtogeneratethe10MHzoutputsignaldynamicrangeis60dBupto72kBmemyspace.InadditiondesignersneedtoacceptbefamiliarwiththesubtlebalanceDDScearchitecture..Fromaprac

22、ticalpointofview(seeTable2)thankstotherapiddevelopmentofCMOStechnologymoderndigitaldesigntechniquesaswellastheimprovementoftheDACtopologyDDStechnologyhasbeenabletoachieveunprecedentedlowpowerconsumptioninawiderangeofappl

23、icationsspectrumperfmancecostlevels.AlthoughthepureDDSproductsinperfmancedesignflexibilitytoachievethelevelofhighendDACtechnologyFPGAbuttheadvantagesofDDSintermsofsizepowerconsumptioncostsimplicitymakingittheprimarychoic

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