同轴电缆衰减的测试方法

ENGINEERINGCOMMITTEEInterfacePracticesSubcommitteeAMERICANNATIONALSTANDARDANSI/SCTE472007TestMethodforCoaxialCableAttenuationiNOTICETheSocietyofCableTelecommunicationsEngineers(SCTE)Standardsareintendedtoservethepublicinterestbyprovidingspecifications,testmethodsandproceduresthatpromoteuniformityofproduct,interchangeabilityandultimatelythelongtermreliabilityofbroadbandcommunicationsfacilities.ThesedocumentsshallnotinanywayprecludeanymemberornonmemberofSCTEfrommanufacturingorsellingproductsnotconformingtosuchdocuments,norshalltheexistenceofsuchstandardsprecludetheirvoluntaryusebythoseotherthanSCTEmembers,whetheruseddomesticallyorinternationally.SCTEassumesnoobligationsorliabilitywhatsoevertoanypartywhomayadopttheStandards.SuchadoptingpartyassumesallrisksassociatedwithadoptionoftheseStandardsorRecommendedPractices,andacceptsfullresponsibilityforanydamageand/orclaimsarisingfromtheadoptionofsuchStandardsorRecommendedPractices.Attentioniscalledtothepossibilitythatimplementationofthisstandardmayrequireuseofsubjectmattercoveredbypatentrights.Bypublicationofthisstandard,nopositionistakenwithrespecttotheexistenceorvalidityofanypatentrightsinconnectiontherewith.SCTEshallnotberesponsibleforidentifyingpatentsforwhichalicensemayberequiredorforconductinginquiresintothelegalvalidityorscopeofthosepatentsthatarebroughttoitsattention.Patentholderswhobelievethattheyholdpatentswhichareessentialtotheimplementationofthisstandardhavebeenrequestedtoprovideinformationaboutthosepatentsandanyrelatedlicensingtermsandconditions.AnysuchdeclarationsmadebeforeorafterpublicationofthisdocumentareavailableontheSCTEwebsiteat©SocietyofCableTelecommunicationsEngineers,Inc.2007140PhilipsRoadExton,PA19341iiTABLEOFCONTENTS1.0SCOPE.........................................................................................................12.0EQUIPMENT...............................................................................................13.0BLOCKDIAGRAM....................................................................................24.0TESTSAMPLES.........................................................................................25.0TESTMETHOD..........................................................................................36.0INSPECTION/REPORTFORM..................................................................411.0SCOPE1.1.Measurementtechniquefordeterminingattenuationofcoaxialcableatvariousselectedfrequencies.2.0EQUIPMENT2.1.NetworkAnalyzer:Agilent8753orequivalent75-ohmnetworkanalyzer.Minimumlossmatchingpadsmaybeusedifnecessary.2.2.Networkanalyzercalibrationkit,appropriatefortheconnectortypebeingused.StandardAgilentcalibrationkits(85039BF-Typeand85036BN-Type)arespecifiedto3GHz.2.3.Environmentalchamberorroomcapableofmaintaining68°F(20°C)andlargeenoughtoaccommodatecablesampletobetested.2.4.Thermometerconsistingofadigitalmultimeterandthermalprobeoranydevicecapableofaccuratelymeasuringthetemperatureinsidetheenvironmentalchamber.2.5.Cablepreparationandconnectorinstallationtoolsasrequired.2.6.DropCableTestProper“F”connectorforsizedropcableortheappropriatesizelaboratoryconnector.2.7.HardlineCableTestPush-ontypetestconnectorscableto“N”forthepropersizeofHardlinecableortheappropriatesizefieldconnector.23.0BLOCKDIAGRAMFigure1–NetworkAnalyzerTestSetup4.0TESTSAMPLES4.1.Prepareknownlengthsofcable.Samplesshouldexhibitatleast0.5dBlossatthelowestfrequencytested.4.2.Cuttheendsofthecableandpreparethemtoaccepttheappropriateconnector.4.3.Installtestconnectorsonthecablesampleperthemanufacturer’srecommendations.4.4.Placecablesamplesinanenvironmentalchambersetto68°F(20°C)andallowthetestsamplestostabilizeatthattemperatureforaperiodofatleast2hours.AnalyzerCablesCoaxCable35.0TESTMETHOD5.1.NetworkAnalyzer:5.1.1.Priortocalibrationandtesting,allowthenetworkanalyzertowarmupasdescribedintheoperationsmanual.5.1.2.Incorporatethedesiredfrequencypointsinquestiontobemeasuredwithintheanalyzersregister.5.1.3.SetListFrequencyto“Stepped”toutilizesteppedlistmode.NOTE:Whenusing“Stepped”allthelistedfrequencypointsaresortedasCWpointsinascendingorder.Thenetworkanalyzermeasureseachpointandbuildsasingletracefromthecompositeofalldata.WiththesteppedCWsweepthesweeptimeisslowerthanwhenusingacontinuoussweepforthesamenumberofpoints.5.1.4.Attachtestleadstothetwoportsoftheanalyzer.5.1.5.Connectthetestleadstogetherusinganadaptorfromtheappropriatecalibrationkit.5.1.6.SelectCalibrationmenuonanalyzerandperforma“Thru”calibration.NOTE:Ifminimumlossmatchingpadsarerequired,makesuretheyarepartofthetransmissionpathduringcalibrationorthattheattenuationtheycontributeismeasuredseparatelyandsubtractedfromtheoverallattenuationofthecable+minimumlosspadcombinationonapoint-by-pointbasis.5.1.7.Connectthecableendstothetestleadsortestportsfromthenetworkanalyzerandallowatleastonefullsweepacrosstheentirefrequencyrange..5.1.8.Recordsignallossateachfrequencylistedintheregisterorrunautomatedprogramandprintoutresults.5.2.AttenuationConversion5.2.1.TheconversionfromdB/leng