Site Validation Above 1 GHz (CISPR proposals).pdf

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1、SiteValidationAbove1GHz(CISPRproposals)PresentationtotheSeattleandPortlandIEEEEMCSocietyChaptersMay23-24,2005ClarkVitekSeniorEMCEngineer1Overview•TestEnvironment•ValidationMethod(SiteVSWR)•IdealSiteModeling–(FreeSpaceOATS)•AcceptanceCriteria21TestEnvironment•Since1999,CISPR1

2、6-1hasspecified“ReflectionFree”asthedesiredtestenvironmentformeasurementsinthefrequencyrangeof1-18GHz.–(Reference:CISPR16-1-4,ed.12003,clause8)•However,nomethodhasyetbeenpublishedtoverify“reflectionfree”conditions.3ValidationMethod•CISPRSubcommitteeA,WorkingGroup1hasproduced

3、7draftsonsitevalidation.Currentdraftisnowinfirststageofvoting(calledCDV)tocloseDecember2005.•Themethodisbasedontheconceptthatreflectionscanbedetectedaspeaksandnullsinthereceivedsignalwhenreflectionsarepresentandasourceismovedaroundinthetestvolume.42Background•Inpresenceofref

4、lection,theratioofmaximumreceivedsignaltominimumreceivedsignal,measuredoveraquarterwavelengthisgivenby:EE+Emaxdr=(A1)EE−EmindrWhereEdistheDirectpathsignalandEristhereflectedsignal.5BackgroundIndecibels,astandingwaveratio,S,candBbedefinedastheratioofthemaximumtominimumsignal:

5、EE+EmaxdrS=20log=20log=E−EdBEE−EmaxdBmindBmindr(A2)63Background:ReflectionsAreflectedsignallevelcanalsobeexpressedasadecibel(dB)levelbelowthedirectsignalasfollows:EdE=20log(A3)rdBErBysubstituting(A3)into(A2),therelationshipbetweenSdBandErdBisasfollows

6、:ErdB1020+1S=20log(A4)dBErdB1020−17Background:ReflectionLevelThiscanberearrangedtostateintermsofa“reflectionlevel”:SdB1020+1E=20log(A5)rdBSdB1020−1SinceSdB=EmaxdB–EmindBequationA5providesasimplerelationshipbetweenthelevelofreflection(ErdB)andsomethingwecanm

7、easurewithstandardEMCequipment(SdB=Max–Minfieldstrength).84ReflectionLevelvs.Peak-to-PeakRipple-10)-15rdB-20TargetValue,+/-1dB-25SiteInfluenceduetoReflections-30-35ReflectionLevel(E-4000.511.522.533.54PeaktoPeakRipple(SdB)9SiteVSWRMethod•ThemagnitudeofSisdirectlyrelatedtothe

8、levelofreflectionpresent–thusaquantitativemeasureof“reflectionfree”ispossib