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Download ECE123 Homework 1 1. What is the name of the vector S that
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ECE123 Homework1 1. WhatisthenameofthevectorSthatdescribespowerflowforplanewaves?Expressit intermsofEandH.IfSisorientedalongthe+zdirection,andEisalongthe+ydirection, whatisthedirectionofH? 2. WhatistheratioofE/Hforplanewavesinfreespace?Whatisthisratiointermsof permittivityandpermeability?Thisiscalledthewaveimpedance.Expressitsvaluein Ohms.Whatisthewaveimpedanceofglass,whichisanon-magneticmaterialthathas arefractiveindexn=1.5? 3. Whatisthespeedoflightinfreespacetermsofpermeabilityandpermittivity?What arethevaluesoftheseinMKSunits,andwhatspeeddotheycorrespondtoinm/s? Whatisthespeedoflightinanon-magneticmaterialwitharelativepermittivityof4? 4. Forradiationfromapointsourceorsmallantenna,whatisthedependenceofEorHon rinthefarfield?WhataretheunitsofEandHintheMKSsystem?Whatisthe dependenceofpowerdensitySonr?WhataretheunitsofSintheMKSsystem? 5. (Notethatyoumayneglect+/-signsforthisquestion…justindicatetheorientation.) Foradipoleantennaorientedalongz,forobservationpointsinthefarfield: a. WhatisthedirectionofA? b. WhatisthedirectionofE? c. WhatisthedirectionofH? d. WhatisthedirectionofS? 6. Whatisthemathematicalformforthewavefunctionproducedbyapointsource? Whichpartofthewavefunctioncorrespondstothephaseofthewave?Whichpart correspondstothemagnitude? 7. WhatdegreeoffreedomdowehaveindefiningthescalarelectricpotentialF?Inother words,whatarewefreetochangeaboutFthatwillhavenophysicalmeaning,andno effectonthesolutiontoanyproblem?WhataboutforthevectormagneticpotentialA? 8. Whatfrequencies(approximately)areradiatedbyyourmobilephone?Assume PCS/GSMcellularbandsfor3Gand4G,WiFi(802.11borother),andBluetooth.(Note– lookthemup,dependingonwhichcarrieryouhave,e.g.AT&T,T-Mobile,etc.)What wavelengthsdotheycorrespondto?Whatistheelectricallengthofyourmobilephone (e.g.iPhone5s,Samsung,etc.)inwavelengthsforeachofthesebands?Whataretheir bandwidthsinMHzandthefractionalbandwidthsin%foreachofthesebands?You shouldorganizetheseintoasimpletableforclarity. 9. Ifyourphonehadanold-style“whip”antenna,whichbasicallyactsasadipole,would youexpectyoursignaltobeamaximumorminimumifyoupointthetipoftheantenna directlytowardthebasestation? 10. Whatisthefundamentalsourceofelectromagneticradiation–i.e.whatphysically causesit,orinotherwordswhatisrequiredforradiationtooccur?
