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1、單工無線呼叫系統(tǒng)（D題）摘要：單工無線呼叫系統(tǒng)分發(fā)射和接收兩大部分。發(fā)射部分采用鎖相環(huán)式頻率合成器技術(shù)，MC145152和MC12022芯片組成鎖相環(huán)，將載波頻率精確鎖定在35MHz，輸出載波的穩(wěn)定度達(dá)到4×10-5，準(zhǔn)確度達(dá)到3×10-5，由變?nèi)荻O管V149和集成壓控振蕩器芯片MC1648實現(xiàn)對載波的調(diào)頻調(diào)制；末級功放選用三極管2SC1970，使其工作在丙類放大狀態(tài)，提高了放大器的效率，輸出功率達(dá)到設(shè)計要求。接收部分以超大規(guī)模AM/FM立體聲收音集成芯片CXA1238S為主體，靈敏度、鏡像抑制、信噪比等各項性能指標(biāo)均達(dá)到設(shè)計要求；音頻功率放大器采用集成芯片LM386，電壓放大倍
2、數(shù)最大為200。采用PT2262/2272編碼/解碼電路實現(xiàn)了數(shù)據(jù)傳輸業(yè)務(wù)以及對臺號的選擇等功能；音頻輸入和數(shù)據(jù)輸入可自動轉(zhuǎn)換；AT89S52作為整個系統(tǒng)的控制部分，程序設(shè)計采用C語言在KEIL51的編譯器上編程實現(xiàn)；顯示采用128×64點陣型液晶顯示。經(jīng)測試，整機功能齊全，各項性能指標(biāo)符合系統(tǒng)要求，接收波形穩(wěn)定，無明顯失真。關(guān)鍵詞：鎖相環(huán)、壓控振蕩器、靈敏度、編碼/解碼simplexwireless-callingsystemAbstract:Thesimplexwireless-callingsystemconsistsoftwoparts:transmitpartandrec
3、eivepart.Thetransmitpartadoptsthephase-lockedlooppatternoffrequencysynthesizingtechnologyandusestheMC145152andMC12022chipstocomposethephase-lockedloop.Itlocksthefrequencyofthecarrier-waveat35MHz.Thestabilizationofthecarrier-wavecanbe4×10-5,theaccuracycanbe3×10-5.Thefrequencymodulationandthecon
4、fectionofthecarrier-wavearerealizedbythecapacity-changingdiodeV149andtheintegrationvoltage-controloscillatorMC1648chip.Theendpoweramplifierusestheaudion2SC1970tomakeitworkinthethirdmagnifyingstate,itimprovestheefficiencyofthemagnifierandthepoweroftheoutputreachesthedesigndemand.Thereceivepartu
5、sesthesupercosmicallyAM/FMdimensionalsoundstereoradioreceptionintegrationchipCXA1238Sasthemainpart.Thesensitivity、themirror-controlrestrain、theSNRandeverycapabilityindexallreachthedesigndemand.TheaudiofrequencypoweramplifieradoptstheintegrationchipLM386.Themaximumvoltageamplifyingmultipleis200
6、.ItusesPT2262/2272coding/decodingcircuittorealizethedatatransmissionoperationaswellastheplatform-choosingfunction.Theinputoftheaudiofrequencyandthedatacanbeautomaticallytransformed.AT89S52isusedasthecontrollingpartofthewholesystem.ThedesignoftheprogramadoptstheClanguagetomakeitbeprogramminglyr
7、ealizedinthetranslator.Thedisplayadopts128×64latticeLCDtoshow.Aftertested,thewholemachine’sfunctionisverycomplete,everydemandcanberealized,thereceivingwaveisstable,withoutevidentdistortion.Keyword:PLL、VCO、Sensitivity、Ding/decoding目錄1、系統(tǒng)
