1、外文原文：http:/ 1 中文 2330 字 毕 业 设 计（论 文）附 件 外 文 文 献 翻 译 学 号： 姓 名： 所在院系： 数理系 专业班级： 指导教师： 原文标题： Research of Parameter Adju
2、stable Harmonic Signal Generator Based on DDS 2014 年 6 月 10 日 2 2008ISECSInternationalColloquiumonComputing,Communication,Control,andManagement ResearchofParameter AdjustableHarmonicSignalGeneratorBasedonDDS LI Wei ZHANGJinbo
3、 CollegeofComputerandInformation CollegeofComputerandInformationEngineering Engineering HohaiUniversity HohaiUniversity Changzhou,213022,China Changzhou,213022,Chinaliwei_ Abstract Harmonicsignalgeneratorwhosefrequency,phaseandharmonicproportionareadjustableisdesignedforthe
4、detectingequipmentofpowersystem.TheprincipleofDDSandthedesign requirement are introduced.ThenthealgorithmofROMcompression based onthe symmetry ofsinewaveisexpounded.Finally,usingAlteraFPGA,thedetaildesignofthewholesystemispresentedandtestwaveformsaregiven.Testresultsindicatethatthesystemfulfilsthede
5、signrequirements. 1. Introduction Anideal power systemsupplies powerwithsinewave,butthepracticalwaveformofpowersupplyoftenhasmanyharmoniccomponents.Thebasicreasonofharmonicisthatthepowersystemsuppliespowertotheelectricalequipmentwithnonlinearcharacteristic.Thesenonlinearloadsfeedhigherh
6、armonicbacktothepowersupply,andmakethewaveformofcurrentandvoltageinpowersystemproduceseriousdistortion. Inthedetectionfieldofpowersystem,standardsignalgeneratorswhichcansimulatethepowerharmonicarehighlyneededtocalibratethepowerdetectingequipment,suchasphasedetector,PDdetector,andsoon.Sotheresearchof
7、parameteradjustableharmonicsignalgeneratorprovides theexactbasis forthestableoperationofpowerdetectingequipment,andhasgreateconomicbenefitandsocialvalue. 2. Principleofdirectdigitalsynthesis Directdigitalsynthesis(DDS)isanewfrequencysynthesistechnologywhichdirectlysynthesizeswaveformonth
8、ebasisofphase.Usingtherelationshipbetweenphaseandamplitude,thephaseofwaveformis 3 segmented and assignedrelevant addresses. Ineachclockperiod,theseaddresses are extractedandtherelevantamplitudesaresampled.Theenvelopeofthesesampledamplitudesistheexpectedwaveform.Iftheclockfrequencyiscons
9、tant,thefrequencyofoutputsignalisadjustablewithdifferentextractedstepsofaddresses1.TheprinciplediagramofDDSisshowninFig.1. Figure1.PrinciplediagramofDDS Intheaboveprinciplediagram,DDSiscomposedofphaseaccumulator,ROMtable,DACandLPF.Ineachclockperiod,theoutputofphaseaccumulatorisaccumulatedwithf
10、requency controlword,andhighL-bitoftheoutput are used as address to querythe ROM table.IntheROM,theseaddressesareconvertedtothesampledamplitudes of theexpectedwaveform.Then DACconvertsthesampledamplitudestoladderwave.IntheLPF,theladderwaveissmoothed,andtheoutputisthecontinuousanalogwaveform2.
11、Supposethattheclockfrequencyisfc,frequencycontrolwordisK,phaseaccumulatorisN-bit,thenoutputfrequencyisfout=(K/2N)fc,frequencyresolutionisfmin=fc/2N.AccordingtotheNyquistSampleCriterion,outputfrequencyupperlimitisfmax<0.5fc.Becauseofthenon-idealcharacteristicofLPF,outputfrequencyupperlimitofDDSisfmax=0.4fc. 3. Schemedesign 3.1. Designrequirements
