COKEVA 11940C Quick start guide

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OperationNote
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11940CClose‐FieldProbe
PartNo.CK‐11940‐90007
PrintedinUSAJan2013

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Notice
ProductTransition
UndertheauthorizationofAgilentTechnologies,Cokeva,Inc.isofferingthe11940Casadirectreplacementforthe
Agilent11940A.The11940Cprovidesthefunctionalityandreliabilityyouexpect.
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ContactingCokevaSalesandServiceOffice
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Formoreinformation,pleasecontactusat:
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Cokeva,Inc.
9000FoothillsBlvd,Roseville,CA95747USA
www.cokeva.com
[email protected]
Tel:+1916.462.6000

Businesshours:Mon–Fri|8:00AM‐4:30PM(PacificStandardTime)
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Inanycorrespondenceortelephoneconversation,pleaserefertoyourinstrumentbyitsmodelnumberandfull
serialnumber.
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©Cokeva,Inc.2013
AllRightsReserved.Reproduction,adaptation,ortranslationwithoutpriorwrittenpermissionisprohibited,except
asallowedunderthecopyrightlaws.


Certification
Cokeva,Inc.certifiesthatthisproductmetitspublishedspecificationsatthetimeofshipmentfromthefactory.
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Warranty
ThisCokeva,Inc.productiswarrantedagainstdefectsinmaterialandworkmanshipforaperiodofoneyearfrom
dateofshipmentorforthelengthofapurchasedwarrantyextensionifapplicable.Duringthewarrantyperiod,
Cokeva,Inc.will,atitsoption,eitherrepairorreplaceproductswhichprovetobedefective.
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Forwarrantyserviceorrepair,thisproductmustbereturnedtoCokeva,Inc.Buyershallprepayshippingcharges
toCokeva,Inc.andCokeva,Inc.shallpayshippingchargestoreturntheproducttoBuyer.Buyershallpayall
shippingcharges,duties,andtaxesforproductsreturnedtoCokeva,Inc.fromanothercountry.
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Cokeva,Inc.warrantsthatitssoftwareandfirmwaredesignatedbyCokeva,Inc.forusewithaninstrumentwill
executeitsprogramminginstructionswhenproperlyinstalledonthatinstrument.Cokeva,Inc.doesnotwarrant
thattheoperationoftheinstrument,orsoftware,orfirmwarewillbeuninterruptedorerror‐free.
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LIMITATIONOFWARRANTY
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Theforegoingwarrantyshallnotapplytodefectsresultingfromimproperorinadequatemaintenanceor
calibrationbyBuyerorbyvendorsnotapprovedbyCokeva,Buyer‐suppliedsoftwareorinterfacing,unauthorized
modificationormisuse,operationoutsideoftheenvironmentalspecificationsfortheproduct,orimpropersite
preparationormaintenance.
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NOOTHERWARRANTYISEXPRESSEDORIMPLIED.COKEVASPECIFICALLYDISCLAIMSTHEIMPLIEDWARRANTIESOF
MERCHANTABILITYANDFITNESSFORAPARTICULARPURPOSE.
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EXCLUSIVEREMEDIES
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THEREMEDIESPROVIDEDHEREINAREBUYER'SSOLEANDEXCLUSIVEREMEDIES.COKEVA,INC.SHALLNOTBE
LIABLEFORANYDIRECT,INDIRECT,SPECIAL,INCIDENTAL,ORCONSEQUENTIALDAMAGES,WHETHERBASEDON
CONTRACT,TORT,ORANYOTHERLEGALTHEORY.
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Assistance
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Foranyassistance,contacttheCokeva,Inc.SalesandServiceOfficeat+1916.543.7600between8:00AM–4:30
PM(PST),Mon–Fri.
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Content
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1‐1.GeneralInformation.................................................................1
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1‐2. Description.................................................................1
1‐4. InitialInspection.............................................................1
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2‐1.Specifications.......................................................................1
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3‐1.Operation..........................................................................3
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3‐2. TheoryofOperation..........................................................3
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3‐4. AntennaFactors.............................................................3
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3‐8. PowerDensityandElectricFieldCalculations.....................................
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5
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3‐10. LocalizedFieldSource........................................................5
3‐12. TestSetups.................................................................6
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3‐17. MeasurementTechniques.....................................................8
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4‐1.OperationVerification................................................................8
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4‐4. ReturnLossMeasurementTest................................................. 9
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5‐1.SMARotaryJointInstallationProcedure.................................................12
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Contents‐1
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Cokeva11940COperation Note

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1
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1‐1. GENERALINFORMATION
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1‐2.Description
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1‐3.TheCokeva11940CClose‐FieldProbeisahand‐held,electromagnetic‐fieldsensordesignedtomake
repeatable,calibratedmagneticfieldmeasurementsfrom30MHzto1GHz.Itisoptimizedforthelocationand
measurementofsourcesofelectromagneticinterference(EMI)inelectronicequipment.TheCokeva11940Ccanalso
beusedasalocalizedmagneticfieldsourcewhenoperatedinconjunctionwithanappropriatesignalgenerator,
therebyallowingcircuitboardlevelsusceptibilitytestingofinstruments.

IncludedinShipment:

ITEMDESCRIPTIONQTY
11940C Closefieldprobe,handheld,30MHzto1GHz 1
9320‐6720 ChinaRoHSAddendumforAccessories 1
1250‐1250 Adapter‐CoaxialStraightMale‐NFemale‐SMA 1
1250‐1700 Adapter‐CoaxialStraight Male‐BNCFemale‐SMA 1
8120‐4811 CableAssembly
–
Coaxial 1
CK‐11940‐90007OperationNote 1
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
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
1‐4.InitialInspection

1‐5.Iftheshipmentcontentsareincompleteordamaged,notifytheCokevaoffice.Iftheshippingcontaineris
damaged,orthecushioningmaterialshowssignsofstress,notifythecarrieraswellastheCokevaoffice.Keepthe
shippingmaterialsforthecarrier’sinspection.TheCokevaofficewillarrangeforrepairorreplacementwithout
waitingforaclaimsettlement.

1‐6.SeeParagraph4‐1forOperationVerification.
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2‐1.SPECIFICATIONS
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2‐2.SpecificationsfortheCokeva11940CarelistedinTable1.Anasterisk(*)placedafteranentryindicatesa
supplementalcharacteristic.Supplementalcharacteristicsarenotspecificationsbutarecharacteristicsincludedas
additionalinformationfortheuser.

2‐3.Figure1illustratesthecharacteristicfrequencyresponsefortheCokeva11940CClose‐FieldProbe.
SeeSection3‐4,AntennaFactors,foradditionalinformation.




Cokeva11940COperation Note
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
2
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Table1.Cokeva11940CSpecifications
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
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Figure1.Cokeva11940CCharacteristicAntennaFactors.30MHz‐1GHz


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 




Cokeva11940COperation Note
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

3
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3‐1.OPERATION
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3‐2.TheoryofOperation

3‐3.TheCokeva11940Cisabalancedmagneticfieldsensorthatprovidesanoutputvoltageproportionaltothe
strengthofthemagneticfieldatitstip.RadiatedmagneticfieldscoupledirectlytotheCokeva11940Candproducean
outputsignal;radiatedelectricfieldsalsocoupletotheCokeva11940Cbutdonotproduceanoutputvoltagedueto
theconstructionoftheprobe.TheCokeva11940Cusesadual‐loopsensorandabaluntorejectelectricallycoupled
signals.SeeFigure2.Theprobepreservesfrequencyinformationandisideallysuitedforusewithaspectrum
analyzer.TheCokeva11940Ccircuitryispassiveandthereforeonlycontributesthermalnoisetoanymeasurement
system.Inspecttheprobetipfordamagebeforeusing.

Figure2.MagneticFieldOrientationforMaximumCoupling
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3‐4.AntennaFactors

3‐5.TheCokeva11940Cissuppliedwithacalibrationtablemountedonitsside.Thetableprovidesantenna
factorsatfivecalibrationpoints:30MHz,100MHz,500MHz,850MHz,and1000MHz.Theantenna‐factorunits
usedinthistable,dB(μA/m/μV),areaccurateto±2dBina377ohmfieldimpedance.Addtheantenna‐factorunits
tothemeasuredvoltageindBμVindicatedonthespectrumanalyzertogivemagnetic‐fieldstrengthindB(μA/m).
Refertothefollowingequation:





4
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3‐6.Us
includedi
n

3‐7.Th
e
rejection.
S




H
─FieldStr
e








ethedataincl
n
theprobe'sc
e
probemay
b
S
eeFigure3f
o

e
ngth ( dB
µA
m

)
where

V
SA
=volta
AF=1194
0

K‐lossor
g
(Positi
v
udedinFigur
e
alibrationtabl
b
eusedbelow
o
rcharacteristi
Figure3.
C
)
=V
SA
+AF+K
geindBµVm
e
0
CAntenna
F
g
ainindBbet
w
v
evalueifloss
,
e
1forinterpol
e.
30MHzanda
b
cantennafac
t
C
okeva11940C
C

e
asuredonan
F
actorindB ( 
µ
w
een11940C
a
,
negativevalu

atingantenna
b
ove1000MH
t
orsbelow30
M

Characteristic




C
okeva1
alyzer
µ
A/m
µ
V)

a
ndspectrum
a
eifgain.)
factorsbetwe
zwithoutcali
b
M
Hz.
AntennaFact
o
1940C
O
a
nalyzer
enthefivecal
b
rationandwi
t
o
rsbelow30M
H
O
peratio
n


ibrationfrequ
e
t
hreducedel
e

H
z
n
Note

e
ncies
e
ctricfield

Cokeva11940COperation Note
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5
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3‐8.PowerDensityandElectricFieldCalculations
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3‐9.TheCokeva11940Cmeasuresmagneticfieldstrength.Assuminga377‐ohmfieldimpedance,anassociated
electricfieldstrengthorawavepowerdensitycanbecalculatedfromthemagneticfieldmeasurement.Refertothe
followingequations:
E─FieldStrength(dBµ
m)=VSA+AF+K+51.5
=VSA +AF+K+51.5
PowerDensity(dBmW
c
m2)=VSA+AF+K‐104.3

where

VSA=voltageindBµVmeasuredonanalyzer

AF=11940CAntennaFactorindB(µA/m
µV )
K=lossorgainindBbetween11940Candspectrumanalyzer
(Positivevalueifloss,negativevalueifgain.)
 
EXAMPLE:

At100MHz,measuredVSA=60.3dBµV.LetK=0andAF=44dB(µA/m
µ
V)
then

E(dBµV
m)=60.3+44+51.5=155.8dBµV/m=61.7V/m

S(dBmW
c
m2)=60.3+44–104.3=0dBmW
c
m2=1mW
c
m2


3‐10.LocalizedFieldSource

3‐11.Theprobecanalsobeusedasalocalizedmagneticfieldsourceforlocatingsusceptibilityproblemsonan
electroniccircuit.Itisareciprocaldevice;thatis,avoltagefedintotheunitwillcreateamagneticfieldatthedual‐
loopsensor.Forthisapplication,themaximuminputpoweris0.5Wwithacharacteristicworst‐caseVSWRof3:1.
Table2listscharacteristicmagneticfieldstrengthsdevelopedattheprobetipusing0dBmincidentpower.

Table2.CharacteristicMagneticFieldStrength

  
Frequency
(MHz)
InputPower
(incident)
MagneticFieldStrength
(H

),dB(µΑ/m)
300dBm101
1000dBm98
5000dBm94
8500dBm93
10000dBm98
  

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