Com-Power CG-515 User manual
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INSTRUCTIONMANUAL
Forthe
CombGenerators
CG‐515
1&5MHzstep
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Table of Contents
Productspecifications…………………………………………………………3
Importantprecautionsandmaintenance...……………………………….....4
Warrantyinformation…………………………………………………………5
ProductDescription……………………………………………………………6
Controls&Indicators……………………………………………………..……7
Theory………………….………………………………………………..………8
Application…………….………………………………………………...………9
Typicalradiatedoutput.....................................................................................11
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Introduction
ThismanualprovidesonhowmaintainandusetheCombGenerator.
InformationcontainedinthismanualisthepropertyofCom‐PowerCorporation.Itisissuedwiththe
understandingthatnoneofthematerialmaybereproducedofcopiedwithoutpermissionfromCom‐Power.
ProductSpecifications
Modelscovered:CG‐515
Frequencystepsize:
1or5MHz
Numberofantennasincluded:
Two
Antenna1Freq.range/height: 1–580MHz/(12inches/30.4cm)
Antenna2Freq.range/height: 580to1500MHz/(3inches/7.6cm)
OutputVariation:
<±1dB(attheantennainput)*
UsableFrequencyradiated:
1MHz‐1.5GHz
InternalBatteryType:
6VRechargeableNimH
Batterychargeradapterspecifications:
‐Input: 115/230VAC,60/50Hz
‐Output:
6VDC@500mA(unregulated)
‐Plugtype: 2.5IDx5.5ODmm(centerpinpositive)
Outputconnectortype:
BNC(f)
OperatingtemperatureRange:
0°Cto40°C
Weight:
2lb.(max.)
Dimensions(WxH):3x3x3inches/7.6x7.6x7.6cm
Weight(lb/kg):1lb/0.45kg
*ThisisconductedoutputvariationwithCombGeneratorconnecteddirectlytoEMIreceiverorspectrumanalyzer.
OtherCombGeneratormodelsavailablefromCom‐Power
• CGO‐520CombGenerator,20MHzstep
• CGO‐5100BCombGenerator,100MHzstep
• CGO‐51000ACombGenerator,1GHzstep
• CGC‐510EConductedCombGenerator,100/500KHzstep
• CGC‐255EConductedCombGenerator,50/250kHzstep
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Important precautions and Maintenance
Precautions:
ACombGeneratorisanintentionalradiatordesignedtoproducessignalsoverwidefrequencyrange.Itwas
designedforuseinEMItestlaboratorytoverifyoperationofEMIemissionstestequipment.Theseradiated
signalsmaycauseunwantedradiofrequencyinterferencetootherequipmentoperatinginthevicinity.Ifyou
detectanyinterferenceincreasetheseparationbetweenCombGeneratorandtheotherequipment.
Maintenance:
Therearenouserserviceablepartsinsidetheunit.UsermodificationstotheCombGeneratorwillvoidwarranty.
TheCombGeneratorusesre‐chargeableNimHbatteries.Callthefactoryifthebatteryneedsreplacement.Send
CombGeneratortoauthorizedCom‐Powerservicecenterifneedsrepair.Pleasevisitourwebsiteatwww.com‐
power.comtorequestareturnmerchandiseauthorizationnumber(RMA)beforeyousendtheunitinforservice.
Batterycareandinstructions
Toavoidanyriskofexplosion
• Replacebatterieswiththesizeandtypespecifiedinthismanual.
• Donotdisposeofbatteriesinafireortrashincinerator,orleavebatteriesunderdirectsunlight.
• Donotimmersebatteriesinwaterorotherwisegetthemwet.
• Donotchargebatteries,thatappeartobeleaking,discolored,rusty,deformed;emitanodor
• UseonlybatterychargeradaptersuppliedwiththeCombGeneratortochargethebatteries.
EnvironmentalConditions
ThisequipmentisdesignedforindoorandoutdooruseandissafeunderthefollowingenvironmentalConditions:
• Temperature:5°Cto40°C
• Maximumrelativehumidity:80%
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Warranty
Com‐PowerwarrantstoitsCustomersthattheproductsitmanufactureswillbefreefromdefectsinmaterialsand
workmanshipforaperiodof3years.Thiswarrantyshallnotapplyto:
a)Transportdamagesduringshipmentfromyourplant.
b)Damagesduetopoorpackaging.
c)Productoperatedoutsidetheirspecification.
d)Improperlymaintainedormodified.
e)Consumableitems,fuses,powercords,cables,etc.
f)Normalwear
g)Calibration
h)ProductisshippedoutsidetheUnitedStateswithoutthepriorknowlegeofCom‐Power.
Inaddition,Com‐Powershallnotbeobligedtoprovideserviceunderthiswarrantytorepairdamageresultingfrom
attemptstoinstall,repair,serviceormodifytheinstrumentbypersonnelotherthanCom‐Powerservice
representative.
UndernocircumstancesdoesCom‐Powerrecognizeorassumeliabilityforanyloss,damageorexpensearising,
eitherdirectlyorindirectlyfromtheuseorhandlingofthisproduct,oranyinabilitytousethisproductseperately
orincombinationwithotherequipment.
Whenrequestingwarrantyservices,itisrecommendedthattheoriginalpackagingmaterialbeusedforshipping.
Damageduetoimproperpackagingwillvoidwarranty.
Inthecaseofacomplaint,alabelshouldbeattachedtothehousingoftheinstrumentwhichdescribesbrieflythe
faultsobserved.Ifatthesametimethenameandtelephonenumber(dialingcodeandtelephoneordirectnumber
ordepartmentdesignation)isstatedforpossiblequeries,thishelpstowardsspeedinguptheprocessingof
warantyclaims.Inordertoobtainserviceunderthiswarranty,CustomersmustcontacttheCom‐Power.
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Product Description
Overview
TheCG‐515CombGeneratorsarereferencesignalsources.TheyweredesignedforEMClaboratoriesuse.Itis
idealforquicklydetectingmalfunctioningequipmentintheradiatedemissionstestsetupinbetweenfull
calibrationintervals.Thesemalfunctionsmaygoundetected,unlessittheyarecheckedoften.Fullsitecalibration
althoughmoreaccurateistimeconsumingisnotpracticalforaquicktest.BycomparingCombGeneratordata
takenatregularly,theEMIlabcanensurethatallthetestequipmentandaccessoriesareoperatingwithinthe
expectedrange.Ifanyabnormalityisdetected,itcanbequicklyinvestigatedandrectifiedbeforeitcauses
measurementerrors.
TheCombGeneratorscanalsousedforcomparingtwoormoresiteswithsimilarsetup.Theycanalsobeutilized
asconductedsignalsourcefortestingLineImpedanceStabilizationNetwork(LISN),filtersandcables.
ItemsincludedwithCombGenerators
Equipment,accessories,anddocumentssuppliedwiththemodelCG‐515CombGeneratorsareasfollows:
o User'sguide
o Customwoodenstoragebox
o BatteryChargeradapter
o Twoantennas
o Testdata(optionalreferencedataatextracost)
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Controls and indicators
PoweronSwitch
ThisislocatedonthesideoftheCombGenerator.Itonlynotonlypowersunitonoroff,italsoenablesordisables
thesignaloutput.
Outputconnector
ThecombgeneratoroutputisavailableattheBNCconnectorlocatedonthetopoftheunit.Thisoutputcanbe
usedforradiatedorconductedemissionstesting.Forradiatedmeasurements,themonopoleantennaisattached
tothisconnector.TherearetwoantennaswithBNCmaleconnectorsprovidedtocovertheCombGenerator
radiatedfrequencyrange.Pleaserefertopage3todeterminetheapproximatefrequencyrangeofeachantenna.
Theantennacanbedisconnectedforconductedemissionsmeasurements.DonotconnecttheCombGenerator
conductedoutputaLineImpedanceStabilizationNetwork(LISN)thatisconnectedtoACpower.Wealsodonot
recommendconnectingtheCombGeneratorconductedoutputdirectlytoapreamplifierinput.
Frequencyselectionswitch(1/5MHz)
Thisswitchisallowstheusertoselectbetween1or5MHzfrequencystepsize.
PowerOnindicator
ThegreenpoweronLEDislit,theCombGeneratorispoweredonandoutputisavailableformeasurement.
BatteryLowindicator
WhenredbatteryLowLEDislit,theinternalbatteryneedsrecharging.Theoutputmaynotbereliable.Turnoff
CombGeneratorandchargethebatterywiththesuppliedadapter.Theapproximatetimetofullychargethe
batteryis8hours.TheCombGeneratorcanoperateapproximately18hourswhenfullycharged.Pleasenote
however,thattheoperatingtimegiveninthismanualisapproximateanddependsontheconditionofbattery,
storageperiodandthenumbertimesithasbeenchargedanddischarged.Iftheoperatingtimekeepsdecreasing,
youmayneedtoreplacethebattery.
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Theory
TheCombGeneratorusesanimpulsetogenerateitsstepfrequencyoutput.Itusesastablepowersupplyand
signalshapingcircuittoobtainrelativelystablesignaloutputwithfrequencycomponentsextendingbeyond1GHz.
TheCombGeneratoroperatesonbatterypower.Thebatteryoutputiscontrolledbyavoltagetheregulatorcircuit
toprovidestablepoweroutputtothesignalgeneratingcircuit.Thesignalgeneratingcircuitconsistsofaclock
generator,impulsegenerator,waveshapingcircuitandoutputmatching.Thesignalfrequencyisgeneratedbya
crystaloscillator.
Animpulseintimedomaincorrespondstoaflatoutputacrosstheentirefrequencyspectruminfrequency
domain.Anidealimpulse,bydefinitionisaninfinitemagnitudepulsewithzeroriseandfalltimewithzero
duration.Suchapulseisnotpractical;however,theModelCGO‐501,505and515CombGeneratorsusethis
principletogetanoutputacrossawideband.Thehighlystablefrequencyoutputfromtheoscillatorisusedto
generateanimpulsewithveryshortdurationandsharpriseandfalltimes.Theshapingcircuitwasdesignedfor
improvedstability,extendedfrequencyresponse,andoutputimpedancematchingto50ohms.
Theradiatedreferencesignalistransmittedbytheantennasaffixedontopoftheunit.Anelectricallyshort
monopoleantennaisanantennathatisshortcomparedtothewavelengthofthefrequencyitradiates.Suchan
antennageneratesaradiatedfieldproportionaltoitslength.Theradiatedfield,therefore,compensatesfor
decreasingsignaluptoafrequency,wheretheantennacannotbecalledelectricallyshort.Thistheorydescribes
thegeneralbehaviorofthefield,buteachCombGeneratormaybehaveslightlydifferentthantheotherdueto
circuitvariation.SincetheCombGeneratorsweredesignedtoprovideareferencereadingatagivenfrequency,
thislimitationisnotaproblem.
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Application
RadiatedEmissions
EMItestsitessuchasOpenAreaTestSite(OATS)orAnechoicchambersareconstructedwithspecific
requirementsandarecalibratedinaprecisemannertooptimizethereliabilityoftheemissionsmeasurements.
Thetimeandexpenseincurredisconsideredessentialtoincreasetherepeatabilityofthedata.
Thedatatakenontheabovesitesaregenerallyreliable.However,insomeinstances,discrepanciesdooccur,and
thereliabilityofdataisquestionable.Suchdiscrepanciescouldbediscoveredwheneither(a)datafromtwosites
forthesameequipmentdonotmatch,or(b)thedatafromtwodifferentoccasionsforthesameequipmentatthe
sameOATSarenotconsistent.Itisimportanttofindthecauseforsuchinconsistency.Thisisgenerallyaverytime
consuminganddifficultprocessbecausethereasoncouldbeoneoffourcomplexfactors.
(1)Equipmentundertest(EUT),
(2)TheTestSite
(3)Instrumentation
(4)Testpersonnel.
Eachofthesefactorsmayhavemanypossiblecauses.TheEUT,forexample,mayhavechangeddueto
componentvariation,temperature,operatingmode,wearandtear,designetc.Thetestsitemaybeacausedueto
areflectiveobjectnearthesite,variationofgroundsaturationorambientsignalpresence.Italsocouldbedueto
malfunctioningtestinstrumentation.
Byestablishingsimplemeasurementproceduresimilartotheonedescribedbelowthetestlabcanreduce
occurrenceoftheseproblems.Therebyincreasingthereliabilityofmeasurementstakenonthesite.The
proceduredescribedisjustaguideandcanvariedaccordingtoyourneeds.
MeasurementProcedure
Asmentionedbefore,takingmeasurementmorefrequentlyisimportant.Createalogwithfrequencyandlevels
thatyouwouldliketorecord.Thiscanbedaily,weeklyormonthlylog.WerecommendtakingCombGenerator
measurementbeforetostartingaradiatedemissionstest.SetuptheCombGeneratorwiththeappropriate
antenna(seefrequencyrangeonpage3).PuttheCombGeneratorwheretheequipmentundertest(EUT)is
normallyplacedduringthetest.
MakeameasurementlikeyouwouldonaEUT.Werecommendusingdiscretefrequencypointsratherthanawide
frequencysweep.Suchas30MHz,40MHz,100Hz,900MHz,etc.Recordthelevelforeachfrequency.
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Comparetheselevelswithallsubsequentmeasurementstomakesurethatthepatterndoesnothaveabrupt
changefromtheestablisheddailylogatanyfrequency.Themorehigherthenumberoffrequencypointsthe
highertheaccuracyofthereferencemeasurements.
Thislogisusedtodetectanytestequipmentortestsiterelatedproblemasdescribedbelow.
ProblemsRelatedtoTestEquipment
VariationonthelogoftheCombGeneratoroutputdataisdependentonthetestequipmentaswellassite.The
CombGeneratorreplacestheEUT.TheCombGeneratornotonlygeneratestheoutputsimultaneouslyatallthe
harmonics,butitminimizesanyvariationofitsoutput.Thisisachievedbyutilizingastabilizedsignalcircuitaswell
asgeometryoftheradiator.Thecircuitstabilityismaximizedbydesign,whereasthegeometryoftheradiated
sourceisoptimizedbyeliminatingallcablesduringtheRadiatedEmissionMode.ThetypicalvariationofComb
Generatoroutputatanyfrequencyislessthan±1dB.
WiththevariationsduetotheEUTpracticallyeliminated,onlyvariationsremainingareduetootherfactors,
mainlythetestinstrumentationandthesite.Thevariationduetotestinstrumentationislimitedtothesumtotal
ofthetoleranceonalltestequipmentused(spectrumanalyzer,antenna,preamplifier,cables).Afewdaysofdata
willestablishtherangeofvariationtobeexpectedatasite.Thisisgenerallylessthan±3dB.Anyvariationinthe
readingsabovenormalvariationindicatesapotentialproblem.
Afterthedailylogisestablishedforafewdays,anyproblemiseasilydetectedasalargervariation.Thisprocedure
allowsimmediatedetectionofamajorproblemwiththetestequipment.
ProblemsRelatedtosite
Theaboveprocedurecannotdistinguishtheproblemsrelatedtothetestsite.TheCombGeneratorcanbeusedin
twowaystodetectanyproblemwithatestsite.Onemethodistostartthedailylogimmediatelyafterthetestsite
iscalibrated.Thisway,oneiscertainaboutthevalidityofthedatatakenonthetestsite.Thesecondmethodisto
calibratetheCombGeneratorradiatedoutputasabsoluteemissionlevel.Suchcalibrationisprovidedasanoption
withtheCombGenerators.
Inaddition,whendifficultyariseswithanyEUTdatatakenattwodifferentsites,theCombGeneratorcanbeused
todetermineifbothsitesgivereliableresults,justbycomparingthedataatthetwositeswiththeComb
Generator.Inthiscase,ifthetwositesdonotproducecomparableresults,aCombGeneratorwithcalibrateddata
iscertainlyrequiredtodeterminethefaultysite.
ProblemsRelatedtoTestPersonnel
TheCombGeneratorcannotdirectlyhelptoeliminatethetestpersonnelrelatedproblems.However,by
increasingtheconfidencelevelandestablishingdefiniteproceduresforeliminatingsiteandequipmentrelated
problemsithelpstremendouslytoreducetheproblemsrelatedtoEMImeasurements.
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Typical radiated output
TheseareCombGeneratorradiatedoutputat3meterdistancewiththereceivingantennaheightvariedfrom1to
4meterstakeninanopenareatestsite.
Figure1:1MHzstepsize
Figure5MHzstepsize
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