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Electromagnetics

and

Communication

Lab.ANTENNAS

AND

RADIOWAVEElectromagnetics

and

Communication

Lab.PROPAGATIONRobertE.CollinElectromagneticsandCommunicationLab.SchoolofElectronics&InformationEngineeringXi’anJiaotongUniversity,P.R.ChinaProf.JiangYanshengReferencesElectromagnetics

and

Communication

Lab.1、AntenneTheory——analysisanddesign(secondedition) ConstantineA.Balanis2、《天線》JohnD.Kraus 章文勛譯電子工業(yè)出版社 2005年3、《天線工程手冊》林昌祿電子工業(yè)出版社2002年4.《近代天線設(shè)計(jì)》林昌祿主編人民郵電出版社CHAPTER

ONEElectromagnetics

and

Communication

Lab.COMMUNICATIONWITHRADIO WAVESCommunicationbyelectricalmeansbeganwiththeintroductionoftelegraphyin1844,followedbytelephonyin1878.Inthesesystemselectricalsignalsaresentovertwo-wiretransmissionlinesthatconnectthesenderandrecipient.Itwasnotuntil1897thatMarconifirstpatentedacompletewirelesstelegraphysystembasedontheuseofelectromagneticradiation(radiowaves)thathadbeenpredictedtheoreticallybyMaxwell43yearsearlier.1.1

Types

of

communicationsThere

are

two

broad

categories

ofcommunication

systems:

those

that

utilizetransmission

lines

in

an

interconnected

networkand

those

that

rely

on

electromagnetic

radiationwith

an

antenna

at

both

the

transmitting

andreceiving

sites.Twisted-pair

transmission

lines

will

introducean

attenuation

of

around

2

to

3dB/km

atfrequencies

around

10kHz.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Incommunicationsystemsusingelectromagneticradiation,thesignalpowerisradiatedintoasubstantialangularregionofspacebythetransmittingantennaandonlyasmallfractionofthisradiatedpowerisinterceptedbythereceivingantenna.Thereisthusaverysignificantcouplinglossbetweenthetransmittingandreceivingantennas.OntheOtherhand,thelossincurredversusdistanceisalgebraicinbehaviorElectromagnetics

and

Communication

Lab.Coaxialtransmissionline’slossisaround4to5dB/km.Thusalossof5dB/kmbecomesalossof100dBovera20-kmpath.Ifthepathisdoubledto40-kmanadditionallossof100dBissuffered.Whenitisrecalledthata100-dBlossisareductioninreceivedsignalpowerbyafactorof ,itisreadilyappreciatedthattheexponentialattenuationlawultimatelyplacesasevererestrictiononthedistanceoverwhichcommunicationcantakeplacewithouttheuseofrepeateramplifiers.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.1.2Antenna

SystemElectromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.Electromagnetics

and

Communication

Lab.1.3

Propagation

ofelectromagnetic

WavesElectromagnetics

and

Communication

Lab.1.4基低頻(VLF)低

頻 中

頻 高

頻 甚高頻(LF)

(MF) (HF)

(VHF

)特高頻(UHF)超高頻 極高頻(SHF)

(EHF)1超長波 長波VLW

LW中波MW超短波 分米波 厘米波 毫米波VSW米波3Hz

30Hz

300Hz音頻(VF)Frequency

Bands3kHz

30kHz

300kHz

3MHz

30MHz

300MHz3GHz30GHz300GHz3THz30THz300THz105km104km100m

10m1m100um103km

102km

10km

1km(公里)(米)10cm

1cm

1mm(厘米)(毫米)10

um

1

um(微米)短波SW音頻雷達(dá)頻率微波頻率紅外視頻Electromagnetics

and

Communication

Lab.Radar

BandsElectromagnetics

and

Communication

Lab.UHF波段

(300-800MHz)P波段(500-1000MHz)L波段(1000-2000MHz)S波段(2000-4000MHz)C波段(40

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