射频技术入门之：天线基础

射频技术入门之：天线基础9AntennaBasicsIntroductionAntennasareaveryimportantcomponentofcommunicationsystems.Bydefinition,anantennaisadeviceusedtotransformanRFsignal,travelingonaconductor,intoanelectromagneticwaveinfreespace.Antennasdemonstrateapropertyknownasreciprocity,whichmeansthatanantennawillmaintainthesamecharacteristicsregardlessifitistransmittingorreceiving.Mostantennasareresonantdevices,whichoperateefficientlyoverarelativelynarrowfrequencyband.Anantennamustbetunedtothesamefrequencybandoftheradiosystemtowhichitisconnected,otherwisethereceptionandthetransmissionwillbeimpaired.Whenasignalisfedintoanantenna,theantennawillemitradiationdistributedinspaceinacertainway.Agraphicalrepresen