外文翻译--相位锁相环

《外文翻译--相位锁相环》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、外文翻译--相位锁相环外文翻译■THEPHASE-LOCKEDLOOPPLLThePLLasanFMDemodulatorAsyouhaveseentheVCOcontrolvoltageinaPLLdependsonthedeviationoftheincomingfrequencyThePLLwillproduceavoltageproportionaltothefrequencyoftheincomingsignalwhichinthecaseofFMistheoriginalmodulatingsignalFigure13

2、-54showsatypicalconnectionfortheLM565asanFMdemodulatorIftheIFinputisfrequencymodulatedbyasinusoidalsignalyougetasinusoidalsignalontheoutputasindicatedSincetheimumoperatingfrequencyis500kHzthisdevicemustbeusedindouble-conversionFMreceiverisoneinwhichessentiallytwomixer

3、sareusedtofirstconverttheRFtoa107MHzIFandthenconvertthistoa455kHzIFThefree-runningfrequencyoftheVCOisadjustedtoapproximately455kHzwhichisthecenterofthemodulatedIFrangeCcanbeanyvaluebutRshouldbeintherangefrom2kΩto20kΩTheinputvanbedirectlycoupledaslongasthereisnodcvolta

4、gedifferencebetweenpins2and3TheVCOisconnectedtothephasedetectorbyanexternalwirebetweenpins4and5DeterminethevaluesforRCandCfortheLM565inFigure13-54forafree-runningfrequencyof455kHzandacapturerangeof±10kHzThedcsupplyvoltagesare±6VSolutionUseEquation13-5tocalculateCChoos

5、eR47kΩ■COMMUNICATIONSCIRCUITSThelockrangeandcapturerangemustbedeterminedbeforeCcanbecalculatedThelockrangeisUseEquation13-7tocalculateCThereforePracticeExerciseWhatcanyoudotoincreasethecapturerangefrom±10kHzto±15kHz13-8REVIEWQUESTIONS1Listthethreebasiccomponentsinapha

6、se-lockedloop2WhatisanothercircuitusedinsomePLLsotherthanthethreelistedinQuestion13WhatisthebasicfunctionofaPLL4WhatisthedifferencebetweenthelockrangeandthecapturerangelfaPLL5BasicallyhowdoesaPLLtracktheincomingfrequency■ASYSTEMAPPLICATIONTheDCEdatacommunicationsequip

7、mentsystemintroducedattheopeningofthischapterincludesanFSKfrequencyshiftkeyingmodemmodulatordemodulatorFSKisonemethodformodulatingdigitaldatafortransmissionovervoicephonelinesandisbasicallyaformoffrequencymodulationInthissystemapplicationthefocusisonthelow-speedmodula

8、tordemodulatormodemboardwhichisimplementedwithaVCOfortransmittingFSKsignalsandaPLLforreceivingFSKsignalsAftercompletingthiss