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1、------------------------------------------------------------------------------------------------無線電接收機(jī)英文資料及中文翻譯英文資料及中文翻譯RadioReceiverAblockdiagramforamodernradioreceiverisshowninFig..2-4.Theinputsignalstothisradioareamplitude-modulatedradiowaves.Thebasicelectroniccircuit
2、sinclude:antenna,tuner,mixer,localoscillator,IFamplifier,audiodetector,AFamplifier,loudspeaker,andpowersupply.Fig.2-4ABlockDiagramForModernRadioReceiverAnyantennasystemcapableofradiatingelectricalenergyisalsoabletoabstractenergyfromapassingradiowave.Sinceeverywavepassing
3、thereceivingantenna.Inducesitsownvoltageintheantennaconductor,itisnecessarythatthereceivingequipmentbecapableofseparatingthedesiredsignalfromtheunwantedsignalsthatarealsoinducingvoltagesintheantenna.Thisseparationismadeonthebasisofthedifferenceinfrequencybetweentransmitt
4、ingstationsandiscarriedoutbytheuseofresonantcircuits,whichcanbemadetodiscriminateverystronglyinfavorofaparticularfrequency.Ithasalreadybeenpointedthat,bymakingantennacircuitresonanttoaparticularfrequency,theenergyabstractedfromradiowavesofthatfrequencywillbemuchgreaterth
5、antheenergyfromwavesofotherfrequencies;thisalonegivesacertainamountofseparationbetweensignals.Still——————————————————————————————————————------------------------------------------------------------------------------------------------greaterselectiveactioncanbeobtainedbyt
6、heuseofadditionalsuitablyadjustedresonantcircuitslocatedsomewhereinthereceiverinsuchawayastorejectallbutthedesiredsignal.Theabilitytodiscriminatebetweenradiowavesofdifferentfrequenciesiscalledselectivityandtheprocessofadjustingcircuitstoresonancewiththefrequencyofadesire
7、dsignalisspokenofastuning.Althoughintelligibleradiosignalshavebeenreceivedfromthestationsthousandsofmilesdistant,usingonlytheenergyabstractedfromtheradiowavebythereceivingantennamuchmoresatisfactoryreceptioncanbeobtainedifthereceivedenergyis1amplified.Thisamplificationma
8、ybeappliedtotheradio-frequencycurrentsbeforedetection,inwhichcaseitiscalledradio-frequencyamplification
