中英文翻译--校园自动锁相调频发射原理.doc

INTELLIGENTFREQUENCYMODULATIONOFCAMPUSBROADCASTINGSYSTEMFMradioisthewaytheFMaudiosignaltransmission,thecarrierwavefrequencymodulationwiththeaudiosignalchangescenterfrequencyinthecarrier(notthecenterfrequencymodulationago)onbothsidesofchange,secondchangetheoffsetfrequencyandaudiosignalthesamemodulationfrequency,suchasthefrequencyofaudiosignal1KHz,thecarrierfrequencyoffsetchangesinthenumberoftimespersecond1K.Thesizeofoffsetwiththeamplitudeofaudiosignalsize.FMtransmittersinthedomesticSpecificationslimittoallowthemaximumfrequencyoffset75KHz,thefrequencyresponse80-10000Hz(3dB),harmonicradiation-60dB(forafundamental0dB),thefrequencystabilityof110-6,letternoiseratio50dB,totalharmonicdistortion0.1%,transmittingfrequency87-108MHz,thegeneralprovisionsoftheschoolinthe70-87MHzbetween.Intelligentbroadcastingsystemoncampusasaninnovativeandpracticalequipmentofmoderneducation,inlinewiththecountrysindustryandtheMinistryofEducationseducation-orientedinformationtoandiswidelyconsideredanalternativeschooloftraditionale-ringandear-piercingloudspeakersbroadcastingthegreenenvironment-friendlyproducts.Thesystemwiththelatestcomputernumericalcontroltechnology,high-fidelityaudiotechnology,createdthemusic(ormusicringtones)insteadofe-ringprecedent.Broadcastsystem,whichisindispensableforeachschool,oneoftheinfrastructure,althoughinrecentyearsvideoandnetworktechnologyintherapiddevelopmentofthebroadcastingsystembutstillitspracticality,economy,conveniencewasavarietyofunits,placesofapplication.ExistingtypesofschoolsinChinaarebasicallythepublicaddresssystem,itmainlyusedforvariouspublicoccasions,suchasallofpublicbroadcasting,notification,broadcastavarietyofliteraryandartisticprograms,recognitionofadvancedschooltoconvenetheGeneralAssembly,suchas.Withmoderninformationtechnology,multi-mediateachinginschoolstokeepXinhuanetwidelypopular,themajorityofprimaryandsecondaryschoolstousevoicebroadcastingsystemoflanguageteachinginthecontinuingincreaseindemand,thetraditionalschoolpublicaddresssystemforbroadcastinganumberofsmall-scale,suchas:canteenmealsputonmusic,atdifferentlevelsondifferentclassesofvoicetraininginthemorningandeveningbroadcastsofquartershaveachoiceofbroadcastingdifficulttoachieve.Schoolscannotmeettheteachingvoice,voicetrainingneeds.SmartcampusFMradiosystemisbasedonthecurrentschoolsystemfunctionsonthecampusradiogrowingdemandtodevelopasetofinteractiveintelligentFMradiosystem,ithasnowiringPole,coveringawiderangeofunlimitedexpansion,installationandmaintenanceconvenience,investmentProvince,abeautifulclearsoundqualitycharacteristics.Thesystemiscurrentlyasetofmoreadvancedintelligentbroadcastingsystem.Sincethebirthofradiotechnology,informationtransmissionandinformationprocessinghasalwaysbeenitsmajortask.Toeffectivelylauncharadiosignalout,thesizeoftheantennaandthesignalwavelengthmustbethesameorderofmagnitude.Inordertoeffectivelycarryouttransmission,mustbetobringinformationtothedozensoflow-frequencysignalmodulationMHzmorethanafewhundredMHzhigh-frequencyoscillationsignal,andthensentbytheantenna.Inordertoreducethefactorsthatcausedinstabilityinthesystem,andenhancethereliabilityofthesystem,thesystemmustincludeautomaticgaincontrol,automaticfrequencycontrolandautomaticphasecontrol(PLL)circuitincludingthefeedbackcontrol.Theperformanceofphase-lockedloopcircuitinwhichitisparticularlyimportantTheuseofphase-lockedloopFMprogramsdirectly,sothatitnotonlyhasaveryhighfrequencystability(about10-6),alsohasarelativelyhighamountofthemaximumoffset.TheoverallintegrationoftheFMtransmittercontrolsignals,usedasthecoreoftheBH1417chipcircuitdesign,chipcrystaloscillatortoprovidebenchmarksfortheoscillationfrequencysignalsource,thesourceoscillationfrequencysynthesizerusingPLLmode.TheuseofFMmodulationsignalisaddeddirectlyontotherealizationofvoltage-controlledoscillator.VCOvaractordiodesandbytheBJToscillatorcomposedofthree-pointcapacitance.RFpoweramplifierusingahighefficiencyClassCamplifier.BH1417-houseconsistsofthreebasiccomponents:phasedetector(PD),loopfilter(LPF)andvoltage-controlledoscillator(VCO).Phasedetectorisaphasecomparisondevice,theinputsignalSi(t)andvoltage-controlledoscillatoroutputsignalSo(t)tocomparethephase,resultingintwosignalscorrespondingtotheerrorvoltagephaseSe(t).LoopfilteristofilterouttheerrorvoltageSe(t)inthehighfrequencycomponentsandnoiseinordertoensuretheperformanceoftherequestedlooptoincreasethestabilityofthesystem.VCOcontrolvoltagebySd(t)thecontrol,sothatthefrequencyofVCOfrequencytotheinputsignalside,untiltheeliminationofthelockfrequencydifference.Phase-lockedloopphaseerrorisarealcontrolsystem.BycomparingtheinputsignalandVCOphasedifferencebetweenoutputsignals,resultingintheerrorcontrolvoltagetoadjusttheVCOfrequency,soastoachievethesamefrequencywiththeinputsignal.Beganitsworkintheloop,iftheinputsignalfrequencyandvoltage-controlledoscillatorfrequencyisdifferentfromthetwosignalsduetotheinherentfrequencybetweenthepoor,isboundtohavebeenchangesinphasedifference,phasedetectoroutputvoltageontheerrorwithinacertainrangechange.Inthiserrorvoltagecontrol,voltage-controlledoscillatorfrequencyischanging.Ifthevoltage-controlledoscillatortochangethefrequencyoftheinputsignalwithfrequencyequaltothestabilityconditionsaremetinthisfrequencystabilized.Achievestability,theinputsignalandVCOoutputsignalfrequencydifferencebetweenthezero,adifferenceofnochangeovertime,theerrorvoltagetoafixedvalueintothelooponthelockstate.Loudspeakersbroadcasttheselectedenvironmentshouldinprinciplebeselectedasthespecificationsofdifferentspeciessuchastheradiospeakers,theceilingintheceilingoftheroom,tousetheembedded,non-afterspeakerenclosuresofsmallpox.Simplestructureofthesespeakers,butthepricesarerelativelycheap,andeasyconstruction.Themaindrawbackisthatafterthecoverisnoteasilyinsects,rodentsbite.Theonlyframeworkintheceilingwithouttheceilingoftheinteriorsurface(suchasopen-frameshoppingmalls)tousethelifting-styleballafterthespeakerorspeakerenclosureceiling.Duetoaceilingequivalenttotheinfinitebaffle,sotheconditionsintheceilingunderthehoodaftertheuseofloudspeakerswillnotcauseashortcircuit.Andthereisnoceilingwhenthesituationisverydifferent,ifstillfreeofsmallpoxafterspeakerenclosures,theeffectwillbepoor.Inprinciple,shouldbeusedwhenhoistingspeaker.However,toolargeinvestmentandcanalsobeusedforsmallpoxafterthespeakerenclosures.Afterthespeakershaverearhoodcoversmallpoxisnotonlytheroleofthegeneralmechanicalprotection,andtosomeextentplaytheroleofanti-short-circuit.校园自动锁相调频发射原理调频广播是以调频方式进行音频信号传输的，调频波的载波随着音频调制信号的变化而在载波中心频率（未调制以前的中心频率）两边变化，每秒钟的频偏变化次数和音频信号的调制频率一致，如音频信号的频率为1KHz，则载波的频偏变化次数也为每秒1K次。频偏的大小是随音频信号的振幅大小而定。在国内调频发射机技术指标允许最大频偏限制在75KHz，频率响应80-10000Hz（3dB），谐波辐射强度-60dB（以基波为0dB），频率稳定度110-6，信噪比50dB，失真度0.1%，发射频率87-108MHz，学校一般规定在70-87MHz之间。校园智能广播系统作为一种新颖实用的现代教育设备，符合国家的产业导向和教育部的教育信息化要地，被广泛认为是替代学校传统电子铃声和刺耳高音喇叭广播的绿色环保型产品。该系统凭借最新的计算机数字控制技术、高保真