Network Analyzer Basic Introduction

AgilentNetworkAnalyzerBasics2AbstractThispresentationcoverstheprinciplesofmeasuringhigh-frequencyelectricalnetworkswithnetworkanalyzers.Youwilllearnwhatkindsofmeasurementsaremadewithnetworkanalyzers,andhowtheyallowyoutocharacterizebothlinearandnonlinearbehaviorofyourdevices.ThesessionstartswithRFfundamentalssuchastransmissionlinesandtheSmithchart,leadingtotheconceptsofreflection,transmissionandS-parameters.Thenextsectioncoversthemajorcomponentsinanetworkanalyzer,includingtheadvantagesandlimitationsofdifferenthardwareapproaches.Errormodeling,accuracyenhancement,andvariouscalibrationtechniqueswillthenbepresented.Finally,sometypicalswept-frequencyandswept-powermeasurementscommonlyperformedonfiltersandamplifierswillbecovered.Anappendixisalsoincludedwithinformationonadvancedtopics,withpointerstomoreinformation.3NetworkAnalysisisNot....Thismoduleisnotaboutcomputernetworks!Whenthename“networkanalyzer”wascoinedmanyyearsago,therewerenosuchthingsascomputernetworks.Backthen,networksalwaysreferredtoelectricalnetworks.Today,whenwerefertothethingsthatnetworkanalyzersmeasure,wespeakmostlyaboutdevicesandcomponents.WhatTypesofDevicesAreTested?Herearesomeexamplesofthetypesofdevicesthatyoucantestwithnetworkanalyzers.Theyincludebothpassiveandactivedevices(andsomethathaveattributesofboth).Manyofthesedevicesneedtobecharacterizedforbothlinearandnonlinearbehavior.Itisnotpossibletocompletelycharacterizeallofthesedeviceswithjustonepieceoftestequipment.Thenextslideshowsamodelcoveringthewiderangeofmeasurementsnecessaryforcompletelinearandnonlinearcharacterizationofdevices.Thismodelrequiresavarietyofstimulusandresponsetools.Ittakesalargerangeoftestequipmenttoaccomplishallofthemeasurementsshownonthischart.Someinstrumentsareoptimizedforonetestonly(likebit-errorrate),whileothers,likenetworkanalyzers,aremuchmoregeneralpurposeinnature.Networkanalyzerscanmeasurebothlinearandnonlinearbehaviorofdevices,althoughthemeasurementtechniquesaredifferent(frequencyversuspowersweepsforexample).Thismodulefocusesonswept-frequencyandswept-powermeasurementsmadewithnetworkanalyzers4DeviceTestMeasurementModelHereisakeytomanyoftheabbreviationsusedatright:Response840008400serieshigh-volumeRFICtesterDed.TestersDedicated(usuallyone-box)testersVSAVectorsignalanalyzerSASpectrumanalyzerVNAVectorsignalanalyzerTG/SATrackinggenerator/spectrumanalyzerSNAScalarnetworkanalyzerNFMtr.Noise-figuremeterImped.An.Impedanceanalyzer(LCRmeter)PowerMtr.PowermeterDet./ScopeDiodedetector/oscilloscopeMeasurementACPAdjacentchannelpowerAM-PMAMtoPMconversionBERBit-errorrateCompr’nGaincompressionConstell.ConstellationdiagramEVMError-vectormagnitudeEyeEyediagramGDGroupdelayHarm.Dist.HarmonicdistortionNFNoisefigureRegrowthSpectralregrowthRtnLsReturnlossVSWRVoltagestandingwaveratio5LightwaveAnalogytoRFEnergyOneofthemostfundamentalconceptsofhigh-frequencynetworkanalysisinvolvesincident,reflectedandtransmittedwavestravelingalongtransmissionlines.Itishelpfultothinkoftravelingwavesalongatransmissionlineintermsofalightwaveanalogy.Wecanimagineincidentlightstrikingsomeopticalcomponentlikeaclearlens.Someofthelightisreflectedoffthesurfaceofthelens,butmostofthelightcontinuesonthroughthelens.Ifthelensweremadeofsomelossymaterial,thenaportionofthelightcouldbeabsorbedwithinthelens.Ifthelenshadmirroredsurfaces,thenmostofthelightwouldbereflectedandlittleornonewouldbetransmittedthroughthelens.ThisconceptisvalidforRFsignalsaswell,excepttheelectromagneticenergyisintheRFrangeinsteadoftheopticalrange,andourcomponentsandcircuitsareelectricaldevicesandnetworksinsteadoflensesandmirrors.Networkanalysisisconcernedwiththeaccuratemeasurementoftheratiosofthereflectedsignaltotheincidentsignal,andthetransmittedsignaltotheincidentsignal.6WhyDoWeNeedtoTestComponents?Componentsaretestedforavarietyofreasons.Manycomponentsareusedas“buildingblocks”inmorecomplicatedRFsystems.Forexample,inmosttransceiversthereareamplifierstoboostLOpowertomixers,andfilterstoremovesignalharmonics.Often,R&Dengineersneedtomeasurethesecomponentstoverifytheirsimulationmodelsandtheiractualhardwareprototypes.Forcomponentproduction,amanufacturermustmeasuretheperformanceoftheirproductssotheycanprovideaccuratespecifications.Thisisessentialsoprospectivecustomerswillknowhowaparticularcomponentwillbehaveintheirapplication.Whenusedincommunicationssystemstopasssignals,designerswanttoensurethecomponentorcircuitisnotcausingexcessivesignaldistortion.Thiscanbeintheformoflineardistortionwhereflatmagnitudeandlinearphaseshiftversusfrequencyisnotmaintainedoverthebandwidthofinterest,orintheformofnonlineareffectslikeintermodulationdistortion.Oftenitismostimportanttomeasurehowreflectiveacomponentis,toensurethatitabsorbsenergyefficiently.Measuringantennamatchisagoodexample.7AgendaInthissectionwewillreviewreflectionandtransmissionmeasurements.WewillseethattransmissionlinesareneededtoconveyRFandmicrowaveenergyfromonepointtoanotherwithminimalloss,thattransmissionlineshaveacharacteristicimpedance,andthataterminationattheendofatransmissionlinemustmatchthecharacteristicimpedanceo