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1、双工无线语音数据传输系统的设计TriplewirelessvoicedatatransmissionsystemdesignStudent:Liufigure,physicsandinformationengineeringcollegesInstructor:XiaoYunhong,JianghanUniversityEveryday,inourworkandinourleisuretime,wecomeincontactwithanduseavarietyofmoderncommunicationmedia,themostcommonbeingthetelephone,radio
2、,television,andtheInternet.Thoughthesemediaweareabletocommunicate(nearly)instantaneouslywithpeopleondiffidentcontinents,transactourdailybusiness,andreceiveinformationaboutvariousdevelopmentsandeventsofnotethatoccurallaroundtheworld.Electronicmailandfacsimiletransmissionhavemadeitpossibletorapid
3、lycommunicatewrittenmessageacrossgreatdistances.Wirelesscommunications.ThedevelopmentofwirelesscommunicationsstemsfromtheworksofOersted,Faraday,Gauss,Maxwell,andHertz.In1820,Oersteddemonstratedthatanelectriccurrentproducesamagneticfield.OnAugust29,1831,MichaelFaradayshowedthataninducedcurrentis
4、producedbymovingamagnetinthevicinityofaconductor.Thus,hedemonstratedthatachangingmagneticfieldproducesanelectricfield.Withthisearlyworkasbackground,JamesC.Maxwellin1864predictedtheexistenceofelectromagneticradiationandformulatedthebasictheorythathasbeeninuseforoveracentury.Maxwell’stheorywasver
5、ifiedexperimentallybyHertzin1887.In1894,asensitivedevicethatcoulddevicethatcoulddetectradiosignals,calledthecoherer,wasusedbyitsinventorOliverLodgetodemonstratewirelesscommunicationoveradistanceof150yardsatOxford,England.GuglielmoMarconiiscreditedwiththedevelopmentofwirelesstelegraphy.Marconide
6、monstratedthetransmissionofradiosignalsatadistanceofapproximately2kilometersin1895.Twoyearslater,in1897,hepatentedaradiotelegraphsystemandestablishedtheWirelessTelegraphandSignalCompany.OnDecember12,1901,MarconireceivedaradiosignalatSignalHillinNewfoundland,whichwastransmittedfromCornwall,Engla
7、nd,adistanceofabout1700miles.Theinventionofthevacuumtubewasespeciallyinstrumentalinthedevelopmentofradiocommunicationsystem.ThevacuumdiodewasinventedbyFlemingin1904andthevacuumtriodeamplifierwasinventedbyDeForestin1906,aspreviousl