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1、High-ResolutionAudioDACsFinalReportAReviewoftheDigitalAudioConversionProcess.IvarL?kken,2005-08-17IvarL?kkenPage117.08.20051IntroductionThisreportistheendresultofaPhD-levelcourseintendedtoprovideinsightintochallengesandsolutionsinaudioDACsystemsdesign.Itwillre
2、viewtheconceptsrelevanttothisapplicationandprovidethereaderwithasystem-leveloverviewaswellasinsightintofundamentalprinciplesandrelations.Figure1:TypicalAudioD/A-conversionsystem.Figure1showsatypicalaudioDACsystem.ThesignalistypicallytransferredthroughtheSony/P
3、hilips-DigitalAudioInterface(SP-DIF)whichisaone-wireserialtransmissionwithbiphase-markencodingandembeddedclocksignal.TheSP-DIFreceiverrecoverstheembeddedclockanddecodesthedata.ItisthentransferredtosubsequentchipsusingtheInter-IC-Sound(I2S)interface,whereserial
4、data,bitclockandwordclockaresentviathreeseparatewires.InmanysystemsithasinlateryearsbecomenormaltoinsertanasynchronoussamplerateconverterbeforetheDAC.Thisenablesthesystemtoacceptawiderangeofinputsampleratesandcanalsoimprovejitterperformance.Thenthesignalisinte
5、rpolatedtoaveryhighsamplerateanddecimatedusinganoise-shapingquantizerordelta-sigmamodulator.Traditionally,1-bitconvertershavemostlybeenused,butinlateryearsfew-bitthermometerDACswithdigitalelementmatchinghavebecomethenorm.Thereasonsforthiswillbecomeevidentasthe
6、readerprogressesthroughthisreport.Theanalogoutputsignalisnextfedtoalarge-scaleamplifierandultimatelyloudspeakers.Thelasttwoprocesseswillnotbereviewedhere.Thisreportwillbeginwithanintroductiontochallengessurroundingjitterandjittersuppression,withspecialemphasis
7、oninterfacingandtheSP-DIFformat.Boththeoreticalmodelsandassessmentsonhowtominimizetheresultingdistortionwillbepresented.Next,wewilllookattheprocessofsampling.ThissectionwillbeginwithashortrecapofShannon’ssamplingtheoremand,asmostaudioDACsystemsareoversamplingd
8、evices,alsolookatinterpolationanddecimation.Furthermore,asynchronoussamplerateconvertershavebecomeverypopularinaudioDACdesign.Wewillreviewtheprinciplesandlookatthebenefitsanddrawba
