attenuation design - google code衰减设计谷歌代码

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1、DDSFREQUENCYGENERATORJonathanHull&KentWarnerSeniorDesign,Fall2010TheDirectDigitalSynthesisfrequencygeneratorwasdesignedtoprovideaninexpensiveandaccuratesolutionforlabbasedtesting.Thisgeneratoroutputssinusoidalandsquarewavesatuserdefinedfrequencies,withavariableattenuationoptio

2、nforthesinusoutput.Introduction:Thepurposeofthisprojectwastopresentaproofofconceptideathatafrequencygeneratorcouldbecreatedwithanimpeccableaccuracyatanextremelylowprice.Frequencygeneratorscurrentlyusedinthelabareprohibitivelyexpensiveandoftencontainunnecessaryoverkillfeaturest

3、hatsimplyaddtothisinaneprice.SimplefrequencygenerationforthelabsettingcanbeachievedwiththeDirectDigitalSynthesischipatamuchlowercostwhilestillmaintainingaccuracyintheoutputwaveform.ThisprojectinvolvedtheconstructionofafrequencygeneratorviatheuseoftheDDSchipandMicroprocessor.Th

4、elabuserselectsadesired,andappropriateperspecifications,frequencyandattenuationlevelthroughaserialterminal.Asinusoidalandsquarewaveoutputisthenproducedandhelduntiltheuserselectsadifferentoutputwave.Thisgeneratorprojectalsoinvolvedtheconstructionofthepowersupply.Thisisanunspons

5、oredprojectandthus,completedforacademicpurposes.ArchitecturalOverview:BlockDiagram:TechnologyChoices:·MicroprocessoroAVR8535Micro§40pinsforversatilefunctionalitywithattenuationlines§Internal1MHzoscillator§+5Vsupplyfromconstructedpowersupply§UsedtopowertheDDSchip,Attenuator,Ser

6、ialcommunication·DirectDigitalSynthesis(DDS)oAD9851DDS§Inexpensive,mainstreamDDSoption§Optionof6Xreferenceclockmultiplier§0-90MHzoutputfrequencyrange(withreferenceclockof180MHz)§OnboardAnalogcomparator,forCMOSsquarewaveoutput§Usedtogeneratesinusoidsforoutput·RS232SerialCommuni

7、cationoSpring2010EmbeddedSystemsDevelopmentBoardoST232CNRS232chiponboard§Configuration:·4800Baud·8DataBits·1StopBit·AmplificationoLM7171Operationalamplifiers§GainBandwidthà200MHz§+/-5Voperationo25MHzRClowpassfilters§Maxspecifiedoutput20MHz·AttenuationoZettlerAZ822Relay§DoubleP

8、oleDoubleThrowrelayonlyrequires10linesforthespecifiedattenuat