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1、Advantagesofanewmodulationschemeinanopticalself-mixingfrequency-modulatedcontinuous-wavesystemDanielNordinAbstract.Anewfrequency-modulatedcontinuouswavemodulationKaleviHyyppa¨scheme,whichgivescorrectresultsevenwhentheDopplershiftislargerLuleaUniversityofTechnolog
2、ythanthefrequencydifferenceassociatedwiththerange,ispresentedDivisionofIndustrialElectronicsandtestedwithatunablelaserdiodeandfiber-basedsystem.Byinsert-S-97187Lulea,Swedeningaconstantfrequencyregioninthemodulationscheme,boththeE-mail:danieln@sm.luth.semagnitudean
3、dthesignofallbeatfrequenciescanbedetermined.Whentheyareknown,thecorrectfrequencydifferenceasaresultoftherangecanbecalculated.Thisnewschemegivesmorefreedomwhenchoosingthemodulationparametersofthelaser,becauseincreasingthemodula-tionfrequency,and/orthefrequencyswee
4、p,toavoidambiguitiesresult-ingfromalargeDopplershiftnolongerbecomesnecessary.Thisisespeciallyusefulwhenusingasomewhatcheaperlaserdiodesource,sincethemaximumobtainablemodulationfrequencyandfrequencysweepcanbesomewhatlimited.Thesuggestedmodulationschememakesitpossi
5、bletousesomelaserdiodesinanapplicationtheyother-wisewouldnotbesuitedfor.©2002SocietyofPhoto-OpticalInstrumentationEn-gineers.[DOI:10.1117/1.1467063]Subjectterms:lidar;frequency-modulatedcontinuouswave;frequencymodula-tion;Dopplereffect.Paper010077receivedMar.2,20
6、01;revisedmanuscriptreceivedAug.23,2001;acceptedforpublicationNov.29,2001.1IntroductionElocos(vlot1ulo),theopticalpowerreceivedbythephoto-Frequency-modulatedcontinuouswave~FMCW!isarangediode,ignoringre¯ectionsatthephotodiode,willequalandradialvelocitymeasuringtec
7、hniquewellknownfromthe®eldofradarapplications.There¯ectedpartofanout-AF~t!5@Ecos~vt1u!1Ecos~vt1u!#2,~1!goingfrequencymodulatedwave(w1)ismixedwitharrrlololoZlocaloscillatorwave(w2),andasaresultthefrequencydifferencebetweenthetwosignalscanbeobtained.IfthewhereAisth
8、eactiveareaandZisthecharacteristicim-frequencymodulationischosenasatriangularwave,bothpedanceofthemediuminfrontofthedetector.Byexpand-radialvelocityandrangeoft
