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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
2、,themostcommonbeingthetelephone,radio,television,andtheInternet.Thoughthesemediaweareabletocommunicate(nearly)instantaneouslywithpeopleondiffidentcontinents,transactourdailybusiness,andreceiveinformationaboutvariousdevelopmentsandeventsofnotethatoccurallarou
3、ndtheworld.Electronicmailandfacsimiletransmissionhavemadeitpossibletorapidlycommunicatewrittenmessageacrossgreatdistances.Wirelesscommunications.ThedevelopmentofwirelesscommunicationsstemsfromtheworksofOersted,Faraday,Gauss,Maxwell,andHertz.In1820,Oersteddem
4、onstratedthatanelectriccurrentproducesamagneticfield.OnAugust29,1831,MichaelFaradayshowedthataninducedcurrentisproducedbymovingamagnetinthevicinityofaconductor.Thus,hedemonstratedthatachangingmagneticfieldproducesanelectricfield.Withthisearlyworkasbackground
5、,JamesC.Maxwellin1864predictedtheexistenceofelectromagneticradiationandformulatedthebasictheorythathasbeeninuseforoveracentury.Maxwell’stheorywasverifiedexperimentallybyHertzin1887.In1894,asensitivedevicethatcoulddevicethatcoulddetectradiosignals,calledtheco
6、herer,wasusedbyitsinventorOliverLodgetodemonstratewirelesscommunicationoveradistanceof150yardsatOxford,England.GuglielmoMarconiiscreditedwiththedevelopmentofwirelesstelegraphy.Marconidemonstratedthetransmissionofradiosignalsatadistanceofapproximately2kilomet
7、ersin1895.Twoyearslater,in1897,hepatentedaradiotelegraphsystemandestablishedtheWirelessTelegraphandSignalCompany.OnDecember12,1901,MarconireceivedaradiosignalatSignalHillinNewfoundland,whichwastransmittedfromCornwall,England,adistanceofabout1700miles.Theinve
8、ntionofthevacuumtubewasespeciallyinstrumentalinthedevelopmentofradiocommunicationsystem.ThevacuumdiodewasinventedbyFlemingin1904andthevacuumtriodeamplifierwasinventedbyDeForestin1906,aspreviousl
