COKEVA 11940C Quick start guide
OperationNote
11940CClose‐FieldProbe
PartNo.CK‐11940‐90007
PrintedinUSAJan2013
Notice
ProductTransition
UndertheauthorizationofAgilentTechnologies,Cokeva,Inc.isofferingthe11940Casadirectreplacementforthe
Agilent11940A.The11940Cprovidesthefunctionalityandreliabilityyouexpect.
ContactingCokevaSalesandServiceOffice
Formoreinformation,pleasecontactusat:
Cokeva,Inc.
9000FoothillsBlvd,Roseville,CA95747USA
www.cokeva.com
Tel:+1916.462.6000
Businesshours:Mon–Fri|8:00AM‐4:30PM(PacificStandardTime)
Inanycorrespondenceortelephoneconversation,pleaserefertoyourinstrumentbyitsmodelnumberandfull
serialnumber.
©Cokeva,Inc.2013
AllRightsReserved.Reproduction,adaptation,ortranslationwithoutpriorwrittenpermissionisprohibited,except
asallowedunderthecopyrightlaws.
Certification
Cokeva,Inc.certifiesthatthisproductmetitspublishedspecificationsatthetimeofshipmentfromthefactory.
Warranty
ThisCokeva,Inc.productiswarrantedagainstdefectsinmaterialandworkmanshipforaperiodofoneyearfrom
dateofshipmentorforthelengthofapurchasedwarrantyextensionifapplicable.Duringthewarrantyperiod,
Cokeva,Inc.will,atitsoption,eitherrepairorreplaceproductswhichprovetobedefective.
Forwarrantyserviceorrepair,thisproductmustbereturnedtoCokeva,Inc.Buyershallprepayshippingcharges
toCokeva,Inc.andCokeva,Inc.shallpayshippingchargestoreturntheproducttoBuyer.Buyershallpayall
shippingcharges,duties,andtaxesforproductsreturnedtoCokeva,Inc.fromanothercountry.
Cokeva,Inc.warrantsthatitssoftwareandfirmwaredesignatedbyCokeva,Inc.forusewithaninstrumentwill
executeitsprogramminginstructionswhenproperlyinstalledonthatinstrument.Cokeva,Inc.doesnotwarrant
thattheoperationoftheinstrument,orsoftware,orfirmwarewillbeuninterruptedorerror‐free.
LIMITATIONOFWARRANTY
Theforegoingwarrantyshallnotapplytodefectsresultingfromimproperorinadequatemaintenanceor
calibrationbyBuyerorbyvendorsnotapprovedbyCokeva,Buyer‐suppliedsoftwareorinterfacing,unauthorized
modificationormisuse,operationoutsideoftheenvironmentalspecificationsfortheproduct,orimpropersite
preparationormaintenance.
NOOTHERWARRANTYISEXPRESSEDORIMPLIED.COKEVASPECIFICALLYDISCLAIMSTHEIMPLIEDWARRANTIESOF
MERCHANTABILITYANDFITNESSFORAPARTICULARPURPOSE.
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LIABLEFORANYDIRECT,INDIRECT,SPECIAL,INCIDENTAL,ORCONSEQUENTIALDAMAGES,WHETHERBASEDON
CONTRACT,TORT,ORANYOTHERLEGALTHEORY.
Assistance
Foranyassistance,contacttheCokeva,Inc.SalesandServiceOfficeat+1916.543.7600between8:00AM–4:30
PM(PST),Mon–Fri.
Content
1‐1.GeneralInformation.................................................................1
1‐2. Description.................................................................1
1‐4. InitialInspection.............................................................1
2‐1.Specifications.......................................................................1
3‐1.Operation..........................................................................3
3‐2. TheoryofOperation..........................................................3
3‐4. AntennaFactors.............................................................3
3‐8. PowerDensityandElectricFieldCalculations.....................................
.
5
3‐10. LocalizedFieldSource........................................................5
3‐12. TestSetups.................................................................6
3‐17. MeasurementTechniques.....................................................8
4‐1.OperationVerification................................................................8
4‐4. ReturnLossMeasurementTest................................................. 9
5‐1.SMARotaryJointInstallationProcedure.................................................12
Contents‐1
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Cokeva11940COperation Note
1
1‐1. GENERALINFORMATION
1‐2.Description
1‐3.TheCokeva11940CClose‐FieldProbeisahand‐held,electromagnetic‐fieldsensordesignedtomake
repeatable,calibratedmagneticfieldmeasurementsfrom30MHzto1GHz.Itisoptimizedforthelocationand
measurementofsourcesofelectromagneticinterference(EMI)inelectronicequipment.TheCokeva11940Ccanalso
beusedasalocalizedmagneticfieldsourcewhenoperatedinconjunctionwithanappropriatesignalgenerator,
therebyallowingcircuitboardlevelsusceptibilitytestingofinstruments.
IncludedinShipment:
ITEMDESCRIPTIONQTY
11940C Closefieldprobe,handheld,30MHzto1GHz 1
9320‐6720 ChinaRoHSAddendumforAccessories 1
1250‐1250 Adapter‐CoaxialStraightMale‐NFemale‐SMA 1
1250‐1700 Adapter‐CoaxialStraight Male‐BNCFemale‐SMA 1
8120‐4811 CableAssembly
–
Coaxial 1
CK‐11940‐90007OperationNote 1
1‐4.InitialInspection
1‐5.Iftheshipmentcontentsareincompleteordamaged,notifytheCokevaoffice.Iftheshippingcontaineris
damaged,orthecushioningmaterialshowssignsofstress,notifythecarrieraswellastheCokevaoffice.Keepthe
shippingmaterialsforthecarrier’sinspection.TheCokevaofficewillarrangeforrepairorreplacementwithout
waitingforaclaimsettlement.
1‐6.SeeParagraph4‐1forOperationVerification.
2‐1.SPECIFICATIONS
2‐2.SpecificationsfortheCokeva11940CarelistedinTable1.Anasterisk(*)placedafteranentryindicatesa
supplementalcharacteristic.Supplementalcharacteristicsarenotspecificationsbutarecharacteristicsincludedas
additionalinformationfortheuser.
2‐3.Figure1illustratesthecharacteristicfrequencyresponsefortheCokeva11940CClose‐FieldProbe.
SeeSection3‐4,AntennaFactors,foradditionalinformation.
Cokeva11940COperation Note
2
Table1.Cokeva11940CSpecifications
Figure1.Cokeva11940CCharacteristicAntennaFactors.30MHz‐1GHz
Cokeva11940COperation Note
3
3‐1.OPERATION
3‐2.TheoryofOperation
3‐3.TheCokeva11940Cisabalancedmagneticfieldsensorthatprovidesanoutputvoltageproportionaltothe
strengthofthemagneticfieldatitstip.RadiatedmagneticfieldscoupledirectlytotheCokeva11940Candproducean
outputsignal;radiatedelectricfieldsalsocoupletotheCokeva11940Cbutdonotproduceanoutputvoltagedueto
theconstructionoftheprobe.TheCokeva11940Cusesadual‐loopsensorandabaluntorejectelectricallycoupled
signals.SeeFigure2.Theprobepreservesfrequencyinformationandisideallysuitedforusewithaspectrum
analyzer.TheCokeva11940Ccircuitryispassiveandthereforeonlycontributesthermalnoisetoanymeasurement
system.Inspecttheprobetipfordamagebeforeusing.
Figure2.MagneticFieldOrientationforMaximumCoupling
3‐4.AntennaFactors
3‐5.TheCokeva11940Cissuppliedwithacalibrationtablemountedonitsside.Thetableprovidesantenna
factorsatfivecalibrationpoints:30MHz,100MHz,500MHz,850MHz,and1000MHz.Theantenna‐factorunits
usedinthistable,dB(μA/m/μV),areaccurateto±2dBina377ohmfieldimpedance.Addtheantenna‐factorunits
tothemeasuredvoltageindBμVindicatedonthespectrumanalyzertogivemagnetic‐fieldstrengthindB(μA/m).
Refertothefollowingequation:
4
3‐6.Us
includedi
n
3‐7.Th
e
rejection.
S
H
─FieldStr
e
ethedataincl
n
theprobe'sc
e
probemay
b
S
eeFigure3f
o
e
ngth
(
dB
µA
m
)
where
V
SA
=volta
AF=1194
0
K‐lossor
g
(Positi
v
udedinFigur
e
alibrationtabl
b
eusedbelow
o
rcharacteristi
Figure3.
C
)
=V
SA
+AF+K
geindBµVm
e
0
CAntenna
F
g
ainindBbet
w
v
evalueifloss
,
e
1forinterpol
e.
30MHzanda
b
cantennafac
t
C
okeva11940C
C
e
asuredonan
F
actorindB
(
µ
w
een11940C
a
,
negativevalu
atingantenna
b
ove1000MH
t
orsbelow30
M
Characteristic
C
okeva1
alyzer
µ
A/m
µ
V)
a
ndspectrum
a
eifgain.)
factorsbetwe
zwithoutcali
b
M
Hz.
AntennaFact
o
1940C
O
a
nalyzer
enthefivecal
b
rationandwi
t
o
rsbelow30M
H
O
peratio
n
ibrationfrequ
e
t
hreducedel
e
H
z
n
Note
e
ncies
e
ctricfield
Cokeva11940COperation Note
5
3‐8.PowerDensityandElectricFieldCalculations
3‐9.TheCokeva11940Cmeasuresmagneticfieldstrength.Assuminga377‐ohmfieldimpedance,anassociated
electricfieldstrengthorawavepowerdensitycanbecalculatedfromthemagneticfieldmeasurement.Refertothe
followingequations:
E─FieldStrength(dBµ
m)=VSA+AF+K+51.5
=VSA +AF+K+51.5
PowerDensity(dBmW
c
m2)=VSA+AF+K‐104.3
where
VSA=voltageindBµVmeasuredonanalyzer
AF=11940CAntennaFactorindB(µA/m
µV )
K=lossorgainindBbetween11940Candspectrumanalyzer
(Positivevalueifloss,negativevalueifgain.)
EXAMPLE:
At100MHz,measuredVSA=60.3dBµV.LetK=0andAF=44dB(µA/m
µ
V)
then
E(dBµV
m)=60.3+44+51.5=155.8dBµV/m=61.7V/m
S(dBmW
c
m2)=60.3+44–104.3=0dBmW
c
m2=1mW
c
m2
3‐10.LocalizedFieldSource
3‐11.Theprobecanalsobeusedasalocalizedmagneticfieldsourceforlocatingsusceptibilityproblemsonan
electroniccircuit.Itisareciprocaldevice;thatis,avoltagefedintotheunitwillcreateamagneticfieldatthedual‐
loopsensor.Forthisapplication,themaximuminputpoweris0.5Wwithacharacteristicworst‐caseVSWRof3:1.
Table2listscharacteristicmagneticfieldstrengthsdevelopedattheprobetipusing0dBmincidentpower.
Table2.CharacteristicMagneticFieldStrength
Frequency
(MHz)
InputPower
(incident)
MagneticFieldStrength
(H
),dB(µΑ/m)
300dBm101
1000dBm98
5000dBm94
8500dBm93
10000dBm98
6
3‐12.Te
s
3‐13.Th
e
following
p
setupequi
besubstit
u
lossestot
h
sensitivity
,
3‐14.Em
3‐15.Sti
m
structures
radiatesfr
o
frequency
s
tSetups
e
Cokeva1194
p
aragraphsde
s
pmentusedi
n
u
tedforthere
h
esignallevel
s
,
subtractitsg
a
Thediel
e
voltage
o
user,the
issionsTestS
e
m
ulusRespon
s
canbetested
o
manantenn
a
andrelativea
m
0
Coperatesa
s
s
cribedifferen
n
theseexamp
l
commended
e
s
indicatedon
a
infromthed
i
e
ctricmaterial
o
f1kV.Topre
v
probeshould
e
tup:Figure4i
s
eTestSetup:
T
usingstimulu
s
a
placedinsid
e
m
plitudeinfo
r
s
eitheralocal
tapplications
l
es.Anyequip
m
e
quipment.W
h
thespectrum
a
i
splayedsignal
onthetipof
t
v
entdamage
t
notbeused
w
llustratesthe
b
Figure4.E
m
T
herelatives
h
s
responsetec
h
e
theenclosur
e
r
mation.SeeS
e
C
izedmagnetic
andtestsetu
p
m
entthatsati
s
h
enusedasa
p
a
nalyzer.Ifa
p
level.
t
heprobehas
t
otheprobe
a
w
hereapoten
t
b
asicconfigur
a
m
issionsTest
h
ieldingeffecti
v
h
niques.SeeF
e
undertest,
w
e
ction3‐17fo
r
C
okeva1
fieldprobeor
p
sfortheprob
e
s
fiesthecritic
a
p
robe,besure
p
reamplifieris
acharacterist
a
nd/orperson
a
t
ialofover1
k
a
tionusedfor
d
Setup
v
enessofvari
o
igure5.Thetr
w
hiletheprob
e
r
properprobe
1940C
O
localizedmag
e
.Table3lists
a
lspecification
toaddthean
t
usedtoincrea
icbreakdown
a
linjurytoth
e
k
Visavailable
.
d
etectingEMl
o
usenclosure
s
ackinggenera
t
e
andspectru
m
placement.
O
peratio
n
neticfieldsou
r
therecomme
n
slistedinTab
l
t
enna‐factors
a
semeasurem
e
e
.
emissions.
s
andshielded
t
oroutputsig
n
m
analyzerpro
v
n
Note
r
ce.The
n
dedtest
l
e3may
a
ndcable
e
nt
n
al
v
ide
Cokeva11940COperation Note
7
Figure5.StimulusResponseTestSetup
3‐16.SourceTestSetup:Usedasafieldsource,theprobeprovidesamagneticfieldforsusceptibilitytestingof
electroniccircuits.Forbroadbandsusceptibilitytesting,usetheprobewithasweptortrackingsource.SeeFigure6for
anexampleofthebasiclocalizedfieldsourcetestsetup.
Powerappliedtotheprobemustnotexceedthemaximuminputpowerlisted
inTable1ordamagetotheprobewillresult.
Figure6.SourceTestSetup
Cokeva11940COperation Note
8
InstrumentCriticalSpecificationsRecommendedModel
SpectrumAnalyzerFrequencyRange:30MHz–1GHz
HP8567A(10kHz–1.5GHz)
HP8568B(100Hz–1.5GHz)
HP8566B(100Hz–22GHz)
TrackingGeneratorFrequencyRange:30MHz–1GHzHP8444A,Option059(100MHz–1.5GHz)
ForusewithHP8567AorHP8568B
SignalGeneratorFrequencyRange:30MHz–1GHzHP8656B(0.1–990MHz)
Preamplifier*FrequencyRange:30MHz–1GHz
RFGain:20dB
HP8447D(100kHz–1.3GHz)
(Gain>26dB)
*HP85685ARFPreselectormaybesubstitutedifaspectrumanalyzerlistedaboveisused.
Table3.RecommendedTestSetupEquipment
3‐17.MeasurementTechniques
3‐18.Theprobeisdesignedtobeheldveryclosetopotentialradiatingpoints.Theplaneoftheprobetiploopsmust
beperpendiculartotheradiatingmagneticfieldasillustratedinFigure2.Forexample,iftheseamofanenclosureis
beingtestedforEMl,holdtheprobeasillustratedinFigure7.Whenmeasuringtheradiationfromacoaxialcable,
positiontheprobetipasshowninFigure8.Thesideoftheprobewiththecalibrationlabelshouldbefacingaway
fromthecablebeingmeasured.
3‐19.TheprobemaybeusedasasourceinsusceptibilitytestingasdescribedinSection3‐11andParagraph3‐16.In
thisapplication,holdtheprobewithin1cmoftheelectroniccircuitcomponentbeingtested.
4‐1.OPERATIONVERIFICATION
4‐2.OperationVerificationfortheCokeva11940CconsistsoftheReturnLossMeasurementTestincludedinthis
section.Actualantennafactorverificationrequiresacalibratedbroadbandmagneticfield.Areturnlossmeasurement
providesareliablealternatemethodofdeterminingtheprobe'selectricalintegrity.Thetestisperformedovera
frequencyrangewheretheVSWRisapproximately1.25:1foraproperlyoperatingprobe.
Electricaldamageisindicatedbyanylargedecreaseinreturnloss(increaseinVSWR)asspecifiedinthetest.
4‐3.Probesthatfailthistest,althoughdamaged,maystilldetectelectromagneticradiation.Inthiscase,the
antennafactorslistedontheunitarenolongervalidandthecircuitrynolongerrejectselectricfieldcoupling.
Recalibrationoftheprobe'santennafactorsisnotpossible.
Cokeva11940COperation Note
9
4‐4.ReturnLossMeasurementTest
Description
Thistestmeasuresthereturnlossofthe11940Coverafrequencyrangeof30MHzto80MHz.The8750AStorage‐
Normalizerisoptionalandincreasestheeaseofreadingreturnlossmeasurements.Anyequipmentthatsatisfiesthe
followingcriticalspecificationsforthetestsetupmaybesubstitutedfortherecommendedequipment:
FrequencyRange .......................................................................200MHz
TestPortMatch...............................................................>22dBReturnLoss
Equipment
NetworkAnalyzer......................................................................HP8754A
Transmission/ReflectionTestSet.........................................................HP8502A
Storage‐Normalizer(Optional) .......................................................... HP8750A
Adapters:
TypeN(m)toSMA(f) .............................................................. HP1250‐1250
TypeSMA(m)toSMA(m) .......................................................... HP1250‐1159
TypeSMA(f)CoaxialShort ..........................................................HP0960‐0054
Cables:
RFCableKitforHP8502A .............................................................HP11851A
Cokeva11940COperation Note
10
Figure7.TestinganEnclosureSeam
Figure8.TestingaCoaxialCable
Cokeva11940COperation Note
11
Figure9.ReturnLossTestSetup
Procedure
1.ConnecttheequipmentasshowninFigure9.AllowtheHP8754A30minutesofwarm‐uptime.
2.IfanHP8750AStorage‐Normalizerisused,adjustthenormalizer'sgainandpositioncontrolsfortheproper
displayonthenetworkanalyzer.RefertotheHP8750AOperationandServiceManualfortheadjustmentprocedure.
3.SettheHP8754Acontrolsasfollows:
CH1REFPOSITION..................................................................ON
POLARCENTER.....................................................................OFF
START.............................................................................ON
TUNING............................................................ ...........30MHz
SWEEPWIDTH..................................................................50MHz
SWEEP......................................................................AUTOFAS
T
OUTPUT............................................................ ..........+10dBm
EXTFREQUENCYDOUBLER...........................................................OFF
Channel1
A/R................................................ ...............................ON
10dB/DIV..........................................................................ON
REFERENCE.....................................................................‐00dB
POLARA/R........................................................................OFF
Channel2.......................................................... ...............OFF
Cokeva11940COperation Note
12
4.SettheHP8502AInputAttenuationknobto0dB.
5.AdjusttheHP8754AtracetothetopgraticulelineusingtheCH1REFERENCEPOSITIONknob.
TurntheCH1REFERENCEPOSITIONoff.
6.OntheHP8754A,turnontheCH1REFERENCEOFFSET.Adjustthetrace,referenceline,tothetopCRTgraticule
usingtheREFERENCEOFFSETknob.TheHP8754Aisnowcalibratedformakingreturnlossmeasurementsrelativeto
theshort.
7.IfanHP8750AStorageNormalizerisused,pressthefollowingkeysontheHP8750A:[CH1],[INPUT],[STORE
INPUT],and[INPUT‐MEM].Thedisplayedreferencelinewillshifttothemiddleofthescreen.Errorsinthereflection
testsetwillnowbenormalized.
8.RemovetheSMACoaxialShortandreplaceitwiththeCokeva11940Cprobe.Thedisplayedtraceshouldbe16dB
ormorebelowthereferencelineatallfrequencies.Ifthetraceislessthan16dBbelowthereferenceline,theprobe
failsthetest.
5‐1.SMAROTARYJOINTINSTALLATIONPROCEDURE
Figure10.SMAADAPTERLOCATION
Figure11.RFRotaryJointMountedonProbe
Cokeva11940COperation Note
13
1.Usea7/32"wrenchtoremovetheoldSMAAdapter(seeFigure10).Turntheadaptercounterclockwise
asviewedlookingattherearoftheprobe.
2.TheSMARotaryJointhasoneSMAconnectorlocatedateachend.Oneconnectorrotateswithrespecttothe
bodyoftheRotaryJoint.Theotherconnectorisfixedtothebody.Covertwoorthreeendthreadsofthefixedend
connectorwithasmallamountofLoctite222®.
3.ScrewtherotatingendoftheRotaryJointclockwiseontotheprobe'sSMAConnector(seeFigure11).
4.Usinga9/32"torquewrench,tightentheRotaryJointto24inch‐pounds.
5.WhenattachingacabletotheRotaryJoint,holdtheRotaryJointbyhandtokeeptheconnectorfromturning.
PrintedinUSA
January2013
ForCokevaInternalReferenceOnly
CokevaPartNumberCK‐11940‐90007
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