AcademicYear2015-2016
ELEC0017:
ELECTROMAGNETICCOMPATIBILITY
LABORATORYSESSIONS
V.BEAUVOIS
P.BEERTEN
C.GEUZAINE
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CONTENTS:
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EMClaboratorysession1:
EMCtestsofacommercialChristmasLEDlightset..........................p.3
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CEMlaboratorysession2:
ReverberationchamberandMobilephonemeasurements.............p.6
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EMClaboratorysession3:
EMCconstraintsforintegratedcircuitsandPCBs.............................p.10
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EMClaboratorysession1
EMCtestsofacommercialChristmasLEDlightset
1. VisitoftheACEsemi-anechoicchamber
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WhatisananechoicchamberandwhyistheACEchambercalled‘semi-anechoic’?
Whatkindofmaterialis‘ferrite’?Whyisitusedinanechoicchambers?
Whataretheblueconesonthewallsofthechamberandwhataretheyusedfor?
Describebrieflyhowtoselectwhichstandard(s)mustbeappliedwhenfirstfacedto
theEquipment-under-Test(EUT).
Therearemanydifferenttypesofantennas,whatarethemostrelevantparameters
toconsiderwhenselectinganantennaforanEMIexperiment?
WhoneedstohaveEMCtestsdoneandwhy?
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2. EMCtestingoftheChristmaslightset
a. Emission
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Whichstandard(s)didyouchoosefortheemissiontests?Why?
WhatisaLISN?WhyisitusedfortheEMItests?
Whyareaverageandpeakvaluesbothmeasured?
Measurements:Doesthelightsetpassalltheemissiontests?Justify.
b. Immunity
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Whichstandard(s)didyouchoosefortheimmunitytests?Why?
Whatarethe3differentperformancecriteria?
Whatphenomenacausetheexistenceofsurgesinthenetwork?
Injected currents: why are they considered as conducted-only below 80 MHz and
radiatedabovethatfrequency?
Measurements:Doesthelightsetpassalltheimmunitytests?Justify.
WhathappenswhenEUTsfailtheEMCtests?
IftheChristmaslightsetfailedoneorseveralEMCtests,couldsomethingbedone
bythemanufacturertoimprovethelightsetperformances?
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3. Otherexamples:
Couldourlightsetbeinstalledinatrain?
Is a low cost supermarket voltmeter submitted to the same EMC tests as a high
precisionlaboratoryspectrum(botharelaboratoryequipment)?Why?
4. Electricfieldmeasurementunderhighvoltagecables
• Whatarethemainchallengesofon-siteopen-airmeasurements?
• Whatistheorderofmagnitudeoftheelectricfieldyoumeasuredunderthepower
line?Canyoucompareittootherrelevantelectricfieldvalues?
• Whatistheorderofmagnitudeofthemagneticfieldunderthepowerline?
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CEMlaboratorysession2:
ReverberationchamberandMobilephonemeasurements
Followtheinstructionsbelowandbrieflyanswerthefollowingquestionsinitalic(acoupleofsentences
maximum).
1. Thereverberationchamber(RC)
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Whatisareverberationchamber?Compareittotheanechoicchamberyouvisitedlasttime.
WhyarethewallsoftheRCmadeofmetal?
Whatistheroleofthestirrer?
WhyaretwocalibrationsnecessarybeforerunningtestsintheRC?
WhatistheparticularinterestofRCsforEMCtests?
ExplainthereasonswhytheRCmustbeoperatedwithinthe[200MHz–18GHz]range.
2. Shieldingeffectivenessofcommonmaterials
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Whatdoestheterm“shieldingeffectiveness”(SE)meanandhowisitcalculated?
Drawasimplediagramoftheexperimentalset-upusedtomeasuretheSE.
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Howdidyouchoosethefrequency?Howdidyouselecttheantennatouseforemissionandfor
reception?
• WhyisthevoltageontheESU/spectrumscaledindBµV?
• Check that the noise level is well below the signal level when the antenna is emitting and no
obstacleisplacedbetweentheantennas.
• Makeatablelistingallthematerialsyouplacedbetweentheantennasandtheresultingvoltage
measuredatthereceptionantenna.CalculatetheSEforallcases.
• Whatmaterialexhibitedthelargershieldingeffectiveness?Why?
3. Mobilephonemeasurements:
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a. Powerofasingletimeslot
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ConnecttheGSMantennatothespectrum.
Putthemobilephoneincommunications(call04/366.36.78e.g.).
PressthePRESETkeytosetthespectrumtoitsdefaultstate.
Find the frequency of the communication channel with the highest power: set the center
frequency (FREQ key) to 900 MHz with a span (SPAN key) and observe the peaks, use the
markerstofindtheexactfrequencycorrespondingtothehighest peak(fmax),putthetraceon
MAXHOLD(intheTRACEmenu)forbettervisibility.Whatisthefrequencycorrespondingtothe
maximumpeakyoucanobserve(fmax)?
PutthetracebacktoCLEAR/WRITEandchangethecenterfrequencytothevalueoffmaxwitha
span0Hz(orpresstheZEROSPANkey)tousethespectrumasasinglefrequencyscope.
Setthereferencelevelto10dBm(checkifthisvalueisappropriate)usingtheAMPTkey.
Setthesweeptimeto1msusingtheSWEEPkey(SweeptimeManual).
Toisolateandstabilizeasingleburst,adjustthetriggerparametersusingtheTRIGmenu:Press
the Trg/Gate Source key and use the arrows to select the Video mode. Then set the Trg/Gate
Levelto70%.Thetriggerlevelisvisibleonthedisplayasaredhorizontallinelabeledwiththe
absolutevalueforthetriggerthreshold.PlottheshapeoftheGSMtimeslotyouisolatedonthe
spectrum.
Tousethespectrumtomeasurethepoweroftheburst,opentheTimeDomainPowersubmenu
intheMEASmenu.SwitchtheLimitstoON.
Adjusttherightandleftlimits(verticallines)ofthebursttothebeginningandtheendofthe
burstusingtheRightLimitandLeftLimitsoftkeysandtherotaryknob.
ThepoweroftheburstvaluecanbefoundonthespectrumdisplayindBm(RMS).Whatisthe
durationoftheburst?Measurethecorrespondingpower.
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b. RiseandfalltimesoftheGSMburst
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To visualize the rising edge of the burst in high time resolution, first turn of the previous
measurement parameters by pressing the All Functions Off key in the MEAS menu. Set the
sweeptimeto100µsandsettheTriggerOffset(TRIGmenu)to-50µs.
Usethemarkerstoestimatethevalueoftherisetimeoftheburst.
Tovisualizethefallingedge,settheTriggerOffsetto500µs.
Use the markers to estimate the value of the fall time of the burst. Measure the rise and fall
timesoftheburst.
c. Signal-to-NoiseratiooftheGSMburst
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Resetthespectrumtoitsdefaultstatethensetthecenterfrequencybacktof_maxandreturn
tozerospanmode.
Settheresolutionbandwidthto1MHzusingtheResBWManualkeyintheBWmenu.
Setthereferencelevelto10dBm(AMPTmenu).
Setthesweeptimeto2ms(SweeptimeManualkeyintheSWEEPmenu).
Set the Trg/Gate Source to Video, the Trg/Gate level to 70% and the Trigger Offset to -1 ms
(TRIG menu). The GSM burst should be well displayed in the right-hand half of the spectrum
screen.
Measurethepoweroftheburstaccordingtothepreviousinstructions.Calculatethesignal-tonoiseratiooftheburst.
To simply and efficiently measure the power of the noise during an equivalent time interval,
simply set the Trg/Gate Polarity to Neg (the burst is now in the left-had half of the screen,
outsidethemeasurementzonepreviouslydefined).
d. RadiationDiagramoftheGSMandinfluenceofEMshields/patches
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Resetthespectrumtoitsdefaultstatethensetthecenterfrequencybacktof_maxandreturn
tozerospanmode.Setthereferencelevelto10dBm,setthesweeptimeto2msandsetthe
Trg/GateSourcetoVideo,theTrg/Gatelevelto70%andtheTriggerOffsetto-1ms.
Adjusttheleftandrightlimitsandthepoweroftheburstshouldbedisplayedonthescreen(as
inthesecondexperiment).
RotatetheGSMholderbyincrementsof60degreesandnotethecorrespondingpowervalues.
Repeatthepreviouspointforeachpatchorshieldandnotethevalues.
Plotinpolarcoordinatesasimplifiedradiationdiagramofthemobilephoneradiationpowerin
the time slot selected previously, do it again using the “electromagnetic shield” and with the
patch.Explaintheresultsinafewwords.
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EMClaboratorysession3:
EMCconstraintsforintegratedcircuitsandPCBs
Read again the slides on “Design Rules for electronic circuits and PCBs” (part I and II) from the EMC
coursefollowtheinstructionsbelowandbrieflyanswerthequestionsinitalic.
Experiment1:PCBtrackloopsandunshieldedcables
Requires:
-PCB[5.1]:singlelooptracktoa50ohmcharge,
-PCB[5.2]:looptrackwithaseriescapacitor,
-PCB[5.3]:twostraightparalleltracks,
-PCB[5.4]:singlestraighttrackwithabackgroundplane,
-adigitaloscilloscope,
-asignalgenerator.
Steps:
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ConnectbothendsofaBNCcabletotheoutputofthesignalgenerator.Configureitto
generateasquarewavesignalat1MHz.Observetheshapeofthesignalonthedigital
oscilloscope.Isolateasingle“square”.
Usenowa50ohmsT-terminationanddescribethechangeintheobservedsignal.
Connecta“bananacable”tothesignalgenerator.
Place the PCB [5.1] above the banana cable (using a polystyrene stand), observe the
signalonthedigitaloscilloscopeandmemorizethetrace.Trytoexplainthedeviations
fromaperfectsquareform.
Repeatthepreviousstepforcards[5.2],[5.3]and[5.4].
Comparethefourtracesonthedigitaloscilloscope.
Whyisabananacableusedhere,insteadofacoaxialone?
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Experiment2:Decouplingcapacitorsandresonancefrequency
Requires:
-PCB[12]:twolooptrackswithseriescapacitorsandoneswitchbuttonusedto
selecteitherthesmallorthelargeloop,
-PCB[5.1]:singlelooptracktoa50ohmcharge,
-adigitaloscilloscope,
-asignalgenerator.
Steps:
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ConnecttheBNCconnectorofPCB[12]totheoutputofthesignalgeneratorwitha
squarewaveof2MHz(15V).
UsingPCB[5.1]connectedtothedigitaloscilloscopeasacrudemagneticfieldsensor
(justify?),observeandexplainthechangeofthesignalbehaviorwhentheswitchison0
(largeloop)oron1(smallloop).
Consideringthatbothcapacitorshavea100nFcapacitanceandthatasingleconductor
hasaninductanceof1µH/m1,canyouestimatetheresonancefrequencyofboth
circuits?
Experiment3:Couplingbycommonimpedance
Requires:
-PCB[X(top)],
-adigitaloscilloscope,
-aDCvoltagesource.
Steps:
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Twocomponents:aN555anda7400mustbeconnectedtotheground,usingthefirst
switchyoucanconnectthemusingindependentgroundlinesoracommongroundline.
Thecommongroundlinecanbeselectedusingthesecondswitchtobeeithershortand
largeorlongandthin.ObservethesignalfromtheVoutconnectorontheoscilloscopein
thethreeconfigurations.
Comparethethreetracesandexplain.
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Source:«Electromagneticcompatibilityandprintedcircuitboard(PCB)constraints”,PhilippsSemiconductors,
applicationnote,June1989.
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Experiment4:Influenceofslotsinthegroundplane
Requires:
-PCB[13/7]:singletrackwithcompletegroundplane,
-PCB[13/5]:singletrack,groundplanewithaslot,
-PCB[13/6]:singletrackgoingaroundthegroundplaneslot,
-aspectrumanalyzerwithtrackinggenerator,
-amagneticfieldprobe.
Steps:
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ConnecttheBNCconnectorofPCB[13/7]tothetrackinggeneratoroutput.Connectthe
magneticfieldprobe(usingthepreampmodule)totheinputofthespectrumanalyzer.
PlacetheprobeafewcentimetersabovethePCBandrecordthetracetomemory.
RepeatthepreviousstepforPCB[13/5]and[13/6],placetheprobeabovetheslotand
aboveintactgroundplaneforcomparison.
Comparetheresultsandexplain.
Experiment5:Impedancematchingoftransmissionlines
Requires:
-PCB[4],8BNCconnectorsfor8differentterminations:fourresistors(10,50,
100 and 680 kohms), one open, one Zener diode and two capacitors (100nF
and1nF).
-avectornetworkanalyzer.
Steps:
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CalibratetheVNAusingtheopen,shortandmatchstandards(fullfrequencysweep),
Connect the open termination of the PCB [4] to the VNA and display the reflection
parameter S11 using the Smith chart option. Explain the differences between the
measuredsignalandatheoretically‘perfect’open.Copythetracetomemory.
Repeat the previous step for both capacitors and compare those traces with the open
terminationcase.Comparethemalsousingthemagnitudeandphaseformats.
Delete the previous traces except the one corresponding to the open termination.
Connectthe680-ohmresistorandcomparetheresultswiththeopen.
Connectthe50-ohmresistor,observethesignalontheSmithchartbutalsointheSWR
(standingwaveration)format,explain.Copythetracetomemory.
ConnecttheotherresistorterminationsandcomparetheirtracesintheSWRdisplay.
ConnectthecapacitorterminationsandcomparetheSWRwiththeresistorsresults.
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Experiment6:Influenceofthechoiceofthelogicfamilyofthecomponents:
Requires:
- PCB [1]: four identical circuits using different logic family for the 74002
component:(7400,74LS00,74HC00and74HCT00)withfilteredandnon-filtered
outputforeachcomponent.
-anoscilloscope,
-aspectrumanalyzer,
-asignalgenerator.
Steps:
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ConnectclockinputofPCB[12]totheoutputofthesignalgeneratorwithasquarewaveof
1MHz(5V).Verifythesignalshapeusingtheoscilloscope,measuretheriseandfalltimes.
ConnectthefirstoutputofthePCBtothespectrumanalyzer(150kHz-80MHzsweepanda
referencelevelof87dBµV).Adjustthespectrumparameterstoobtainanoptimumsignal.
Measurethevalueofthefirstpeak(1MHz).
Repeat the previous step for each BNC connector. For each logic family, compare the
filteredandnon-filteredoutputsignalandthevaluesofthe1MHzpeak.
Comparetheoutputsignalsofthefourcircuitsanddrawconclusionsaboutthelogicfamily
used.
Usingtheoscilloscope,measureforeachoutputtheriseandfalltimesoftheoutputsquare
wave. What can you conclude from those measurements, about the different technology
used?
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Theyincludefourtwo-inputNANDgatesusingTTLordifferenttechnologiesbutinaTTL-compatibleformat;7400
isstandardTTLtechnology,74LS00standsfor‘Low-powerSchottky’,implementedusingthesametechnologyas
74Sbutwithreducedpowerconsumptionandswitchingspeed,74HC00:High-speedCMOS,similarperformance
toLSand74HCT00:HighspeedCMOS,compatiblelogiclevelstobipolarparts.
(source:http://en.wikipedia.org/wiki/7400_series).
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