中英文翻譯--校園自動(dòng)鎖相調(diào)頻發(fā)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.校園自動(dòng)鎖相調(diào)頻發(fā)射原理調(diào)頻廣播是以調(diào)頻方式進(jìn)行音頻信號(hào)傳輸?shù)?，調(diào)頻波的載波隨著音頻調(diào)制信號(hào)的變化而在載波中心頻率（未調(diào)制以前的中心頻率）兩邊變化，每秒鐘的頻偏變化次數(shù)和音頻信號(hào)的調(diào)制頻率一致，如音頻信號(hào)的頻率為1KHz，則載波的頻偏變化次數(shù)也為每秒1K次。頻偏的大小是隨音頻信號(hào)的振幅大小而定。在國(guó)內(nèi)調(diào)頻發(fā)射機(jī)技術(shù)指標(biāo)允許最大頻偏限制在75KHz，頻率響應(yīng)80-10000Hz（3dB），諧波輻射強(qiáng)度-60dB（以基波為0dB），頻率穩(wěn)定度110-6，信噪比50dB，失真度0.1%，發(fā)射頻率87-108MHz，學(xué)校一般規(guī)定在70-87MHz之間。校園智能廣播系統(tǒng)作為一種新穎實(shí)用的現(xiàn)代教育設(shè)備，符合國(guó)家的產(chǎn)業(yè)導(dǎo)向和教育部的教育信息化要地，被廣泛認(rèn)為是替代學(xué)校傳統(tǒng)電子鈴聲和刺耳高音喇叭廣播的綠色環(huán)保型產(chǎn)品。該系統(tǒng)憑借最新的計(jì)算機(jī)數(shù)字控制技術(shù)、高保真