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ID:59005789
大小:6.12 MB
页数:62页
时间:2020-09-27
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1、ThePhysicalLayerChapter2TheTheoreticalBasisforDataCommunicationFourierAnalysisBandwidth-LimitedSignalsMaximumDataRateofaChannelBandwidth-LimitedSignalsAbinarysignalanditsroot-mean-squareFourieramplitudes.(b)–(c)Successiveapproximationstotheoriginalsignal.Bandwidth-LimitedSignals(2)(d)–(
2、e)Successiveapproximationstotheoriginalsignal.Bandwidth-LimitedSignals(3)Relationbetweendatarateandharmonics.GuidedTransmissionDataMagneticMediaTwistedPairCoaxialCableFiberOpticsTwistedPair(a)Category3UTP.(b)Category5UTP.CoaxialCableAcoaxialcable.FiberOptics(a)Threeexamplesofalightrayfr
3、ominsideasilicafiberimpingingontheair/silicaboundaryatdifferentangles.(b)Lighttrappedbytotalinternalreflection.TransmissionofLightthroughFiberAttenuationoflightthroughfiberintheinfraredregion.FiberCables(a)Sideviewofasinglefiber.(b)Endviewofasheathwiththreefibers.FiberCables(2)Acomparis
4、onofsemiconductordiodesandLEDsaslightsources.FiberOpticNetworksAfiberopticringwithactiverepeaters.FiberOpticNetworks(2)Apassivestarconnectioninafiberopticsnetwork.WirelessTransmissionTheElectromagneticSpectrumRadioTransmissionMicrowaveTransmissionInfraredandMillimeterWavesLightwaveTrans
5、missionTheElectromagneticSpectrumTheelectromagneticspectrumanditsusesforcommunication.RadioTransmission(a)IntheVLF,LF,andMFbands,radiowavesfollowthecurvatureoftheearth.(b)IntheHFband,theybounceofftheionosphere.PoliticsoftheElectromagneticSpectrumTheISMbandsintheUnitedStates.LightwaveTra
6、nsmissionConvectioncurrentscaninterferewithlasercommunicationsystems.Abidirectionalsystemwithtwolasersispicturedhere.CommunicationSatellitesGeostationarySatellitesMedium-EarthOrbitSatellitesLow-EarthOrbitSatellitesSatellitesversusFiberCommunicationSatellitesCommunicationsatellitesandsom
7、eoftheirproperties,includingaltitudeabovetheearth,round-tripdelaytimeandnumberofsatellitesneededforglobalcoverage.CommunicationSatellites(2)Theprincipalsatellitebands.CommunicationSatellites(3)VSATsusingahub.Low-EarthOrbitSatellitesIridium(a)TheIridiumsatellitesfromsixnecklace
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