无线电接收机英文资料及中文翻译.doc

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1、英文资料及中文翻译RadioReceiverAblockdiagramforamodernradioreceiverisshowninFig..2-4.Theinputsignalstothisradioareamplitude-modulatedradiowaves.Thebasicelectroniccircuitsinclude:antenna,tuner,mixer,localoscillator,IFamplifier,audiodetector,AFamplifier,loudspeaker,andpowersupply.Fig.2-4ABlockDia

2、gramForModernRadioReceiverAnyantennasystemcapableofradiatingelectricalenergyisalsoabletoabstractenergyfromapassingradiowave.Sinceeverywavepassingthereceivingantenna.Inducesitsownvoltageintheantennaconductor,itisnecessarythatthereceivingequipmentbecapableofseparatingthedesiredsignalfrom

3、theunwantedsignalsthatarealsoinducingvoltagesintheantenna.Thisseparationismadeonthebasisofthedifferenceinfrequencybetweentransmittingstationsandiscarriedoutbytheuseofresonantcircuits,whichcanbemadetodiscriminateverystronglyinfavorofaparticularfrequency.Ithasalreadybeenpointedthat,bymak

4、ingantennacircuitresonanttoaparticularfrequency,theenergyabstractedfromradiowavesofthatfrequencywillbemuchgreaterthantheenergyfromwavesofotherfrequencies;thisalonegivesacertainamountofseparationbetweensignals.Stillgreaterselectiveactioncanbeobtainedbytheuseofadditionalsuitablyadjustedr

5、esonantcircuitslocatedsomewhereinthereceiverinsuchawayastorejectallbutthedesiredsignal.Theabilitytodiscriminatebetweenradiowavesofdifferentfrequenciesiscalledselectivityandtheprocessofadjustingcircuitstoresonancewiththefrequencyofadesiredsignalisspokenofastuning.Althoughintelligiblerad

6、iosignalshavebeenreceivedfromthestationsthousandsofmilesdistant,usingonlytheenergyabstractedfromtheradiowavebythereceivingantennamuchmoresatisfactoryreceptioncanbeobtainedifthereceivedenergyis11amplified.Thisamplificationmaybeappliedtotheradio-frequencycurrentsbeforedetection,inwhichca

7、seitiscalledradio-frequencyamplificationoritmaybeappliedtotherectifiedcurrentsafterdetection,inwhichcaseitiscalledaudio-frequencyamplification.Theuseofamplificationmakespossiblethesatisfactoryreceptionofsignalsfromwavesthatwouldotherwisebetooweaktogiveanaudibleresponse.Theprocessbywh