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DX中波发射机模拟输入板主要电路的分析与计算 Title:AnalysisandCalculationofMainCircuitsinDXAMTransmitter'sSimulationInputBoard Introduction: Inthefieldofradiofrequencycommunication,medium-wave(MW)amplitudemodulation(AM)transmittersplayasignificantroleinbroadcasting.Toensuretheefficientandreliabletransmissionofsignals,itiscrucialtodesignandanalyzethemaincircuitsoftheDXAMtransmitter'ssimulationinputboard.ThispaperaimstodiscusstheanalysisandcalculationoftheprimarycircuitsinvolvedinaDXAMtransmitter'ssimulationinputboard. 1.Oscillator: Themainfunctionofanoscillatorinthesimulationinputboardistogenerateastableandcontrollablecarrierfrequency.ThedesignoftheoscillatorisbasedontheColpittsoscillatorconfiguration,whichconsistsofaninductor,capacitors,andtransistors.Theinductorandcapacitorsformaresonantcircuit,whilethetransistorsprovidethenecessaryamplification.Thecalculationoftheoscillator'sfrequencycanbedoneusingformulasrelatedtotheLCcircuit'sresonantfrequency.Bychoosingappropriatevaluesfortheinductorandcapacitors,thedesiredcarrierfrequencycanbeachieved. 2.ModulationCircuit: ThemodulationcircuitinthesimulationinputboardisresponsibleforcombiningtheaudiosignalwiththecarrierwavetoproducetheAMmodulatedsignal.Itmainlyconsistsofanaudioamplifierandadiodemodulator.Theaudioamplifieramplifiestheaudiosignaltoanappropriatelevel,whilethediodemodulatorimposestheamplitudevariationsontothecarrierwave.Thecalculationofthemodulationindex,whichdeterminestheextentofamplitudevariations,canbedoneusingtheformula(ModulationIndex=(MaximumAmplitude-MinimumAmplitude)/(MaximumAmplitude+MinimumAmplitude)). 3.PowerAmplifier: IntheDXAMtransmitter'ssimulationinputboard,thepoweramplifiercircuitiscrucialforamplifyingthemodulatedsignaltoasufficientpowerlevelfortransmission.ThiscircuitisdesignedusingaclassCamplifierconfiguration,whichconsistsofatransistor,amatchingnetwork,andaloadimpedance.Thecalculationofthetransistor'sgainandpoweroutputcanbedoneusingtheformulasrelatedtothemaximumpowertransferandtransistorcharacteristics. 4.AntennaCoup