COMMUNICATION WITH RADIO WAVES 《天线与电波传播》课件培训讲解.pptx

ElectromagneticsandCommunicationLab.

ANTENNASAND RADIOWAVEElectromagneticsandCommunicationLab.PROPAGATIONRobertE.CollinElectromagneticsandCommunicationLab.SchoolofElectronicsInformationEngineeringXi’anJiaotongUniversity,P.R.ChinaProf.JiangYansheng

ReferencesElectromagneticsandCommunicationLab.1、AntenneTheory——analysisanddesign(secondedition) ConstantineA.Balanis2、《天线》JohnD.Kraus 章文勋译电子工业出版社 2005年3、《天线工程手册》林昌禄电子工业出版社2002年4、《近代天线设计》林昌禄主编人民邮电出版社

CHAPTER ONEElectromagneticsandCommunicationLab.COMMUNICATIONWITHRADIO WAVESCommunicationbyelectricalmeansbeganwiththeintroductionoftelegraphyin1844,followedbytelephonyin1878.Inthesesystemselectricalsignalsaresentovertwo-wiretransmissionlinesthatconnectthesenderandrecipient.Itwasnotuntil1897thatMarconifirstpatentedacompletewirelesstelegraphysystembasedontheuseofelectromagneticradiation(radiowaves)thathadbeenpredictedtheoreticallybyMaxwell43yearsearlier.

1.1 TypesofcommunicationsTherearetwobroadcategoriesofcommunicationsystems:thosethatutilizetransmissionlinesinaninterconnectednetworkandthosethatrelyonelectromagneticradiationwithanantennaatboththetransmittingandreceivingsites.Twisted-pairtransmissionlineswillintroduceanattenuationofaround2to3dB/kmatfrequenciesaround10kHz.ElectromagneticsandCommunicationLab.

ElectromagneticsandCommunicationLab.

ElectromagneticsandCommunicationLab.

Incommunicationsystemsusingelectromagneticradiation,thesignalpowerisradiatedintoasubstantialangularregionofspacebythetransmittingantennaandonlyasmallfractionofthisradiatedpowerisinterceptedbythereceivingantenna.Thereisthusaverysignificantcouplinglossbetweenthetransmittingandreceivingantennas.OntheOtherhand,thelossincurredversusdistanceisalgebraicinbehaviorElectromagneticsandCommunicationLab.

Coaxialtransmissionline’sloss