WirelessTransmission：无线传输

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1、WirelessTransmissionTheElectromagneticSpectrumRadioTransmissionMicrowaveTransmissionInfraredandMillimeterWavesLightwaveTransmissionTheElectromagneticSpectrumTheelectromagneticspectrumanditsusesforcommunication.RadioTransmission(a)IntheVLF,LF,andMFbands,radiowavesfol

2、lowthecurvatureoftheearth.(b)IntheHFband,theybounceofftheionosphere.PoliticsoftheElectromagneticSpectrumTheISMbandsintheUnitedStates.LightwaveTransmissionConvectioncurrentscaninterferewithlasercommunicationsystems.Abidirectionalsystemwithtwolasersispicturedhere.Ligh

3、twaveTransmissionCommunicationSatellitesGeostationarySatellitesMedium-EarthOrbitSatellitesLow-EarthOrbitSatellitesSatellitesversusFiberCommunicationSatellitesCommunicationsatellitesandsomeoftheirproperties,includingaltitudeabovetheearth,round-tripdelaytimeandnumbero

4、fsatellitesneededforglobalcoverage.CommunicationSatellites(2)Theprincipalsatellitebands.CommunicationSatellites(3)VSATsusingahub.Low-EarthOrbitSatellitesIridium(a)TheIridiumsatellitesfromsixnecklacesaroundtheearth.(b)1628movingcellscovertheearth.Globalstar(a)Relayi

5、nginspace.(b)Relayingontheground.