无线通信英文概要

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1、1.ShowthatthewavefunctionsatisfiesthedifferentialEMwaveequationS：Similarly,ClearlyAandBareequivalentprovidedthat：2.ShowthatthewavefunctionsatisfiesthedifferentialEMwaveequationS：SinceMagneticfieldonlyvariesinzdirection(eyforunitvectorofy-axisOrthogonaltothevaria

2、tionexforthex-axisincaseofelectricfield)wehaveButj2=-1NowButj2=-1ThereforeAsforQuestion1forAandBtobeequalweneedthefollowingtobetrue:Whichisasbefore:Tutorial61.Briefly(1-2sentences)explainthefollowingterms:(a)ThePoyntingVector(b)ForwardErrorCorrection(c)DopplerSp

3、read(d)Mutualorthogonality(ofasetofvectors)(e)Inter-symbolinterference(f)Polarisation(ofanelectromagneticfield)(g)Antennanoisetemperature(h)Antennasidelobes(i)ChannelequalisationS：(a)•Poyntingvector,P,isthepowerflowthroughareaS,thatresultsinthechangeinstoredener

4、gywithinS•Atanypointinspace,Pgivesthemagnitudeanddirectionofpowerflow•PisthecrossproductofEandH,itisavector,andisorthogonaltobothEandHiePoyntingvectorisdefinedasP=ExH•Ithasdimensionsofwatts/squaremetreb)Thisiswheresingleordoubleormulti-biterrorscanbeaccountedfor

5、andcorrectedbyusingcoding/codewords,forexampleevenandoddparitycanbeusedtodetectsinglebiterrors;sometechniquesallowformorebiterrorstobedetectedandcorrectedegspacingcodewords(Hammingcodes)sofarapartthatmultiplebiterrorscanbedetectedbutthisisatthecostofcreatingextr

6、aoverheadbitsandreducingavailablebandwidthforactualdata–thereisanentireareaoferrorcodingwithinwirelesswhichdealswiththis!(c)Dopplershiftisthemodulation(i.e.variation)ofthenominalfrequencyofanelectromagneticsignalresultingfromrelativemotionofthetransmitter,receiv

7、erand/orreflectors.(d)Thisiswherethedotproductoftwovectorsiszero,indicatingthatintheirn-dimensionalsubspacethattheyareperpendiculartoeachother(forexampleifina2or3dimensionalcoordinatesystem–weessentiallyextendthisintoann-dimensionalsystemfororthogonalcodeswheren

8、>3).Thisisnottrueoftheirshiftedversions–thereasonforMultipleAccessInterference(MAI)(e)Thisiswhereonesymbolinterfereswithanother(dueinwirelesstomultipath)intheconsecut