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1、2.3RadioReceiverCircuitRF,theradiofrequencyportionoftheradiospectrumisconsideredtoextendfrom3to1,000MHz(1GHz).Attheoppositeendofthespectrum,belowthehighfrequency(HF)band(3-30MHz),theAMradiobandextendsfrom650to1,650kHz.Attheserelativelylowfrequenciestheeffectsofparasitic
2、inductanceandcapacitanceoncircuitdesignsareminimal.OutlineThesuperheterodynereceiver-analogsystemReceivercharacterization7/24/20211《电子信息与通信工程专业英语》Terminologyanalogelectronics模拟电子技术digitalsignalprocessing（DSP）数字信号处理superheterodyne（superhet）[电子]超外差式收音机；adj.超外差的selectivity
3、n.选择性sensitivityn.敏感,灵敏(度)，灵敏性preselectorn.预选器，调谐器transmittern.转送者,传达人发报机,话筒,发射机,让渡者thereceivephase接收相位harmonicsn.谐波impedancematch阻抗匹配7/24/20212《电子信息与通信工程专业英语》undesiredsignal干扰信号thelocaloscillator本机震荡器intermediatefrequency（IF）中频modulationsidebands调制边带overloadcharacteris
4、tics过载特性demodulatorn.解调器sophisticatederror经验误差additive,white,Gaussiannoisen.加性高斯白噪声powerspectraldensity功率谱密度megahertzn.[物]兆赫(MHz)兆赫AGCabbr.自动增益控制Spuriousresponses(接收机)乱真信号响应7/24/20213《电子信息与通信工程专业英语》Thesuperheterodyne,orsuperhet,receiver,isawell-knownandalmostuniversalre
5、ceiverarchitectureforradioreceivers.Wewillseethatsuchareceivercanprovidebothgoodselectivityandsensitivity,becausethenoisebandwidthcanbelimitedtothechannelbandwidthwithoutcompromisingthereceiver'sabilitytotuneacrosstheentireRFband.ItsbasiccomponentsareshowninFig.2-3-1.In
6、troductionTexttour1.Thesuperheterodynereceiver-analogsystem7/24/20214《电子信息与通信工程专业英语》7/24/20215《电子信息与通信工程专业英语》ThepurposeofthiscomponentistofilteroutallunwantedsignalslyingoutsidetheRFbandcontainingthepossiblechannelstobedetected.Unwantedsignalscanincludesignalsfedfromthe
7、transmitteritself,whichmightshareacommonantenna.Inthiscasethepreselectoriseitheradiplexer,afilterthatallowsonefrequencybandtopassbetweentheantennaandreceiverandanother(different)bandtopassbetweenthetransmitterandantenna(as,forexample,inCDMAmobilesystems),and/oratransmit
8、/receiveswitchthatturnsonduringthereceivephaseandoffduringthetransmitphase(as,forexample,inGSMsystems).RFprese
