Making Conducted and Radiated Emissions Measurements

8/3/2019 Making Conducted and Radiated Emissions Measurements

1/24

Making Conducted and RadiatedEmissions Measurements

Application Note


2/24

2

1.0 Introduction to Radiated and Conducted Emissions Measurements ........... 31.1 Precompliance versus full compliance EMI measurements ...............................41.2 Systems for performing precompliance measurements ......................................4

2.0 Precompliance Measurements Process........................................................... 52.1 European norms descriptions ...................................................................................62.1.1 EN55011 (CISPR 11) ISM ..................................................................................62.1.2 EN55014 (CISPR 14) ...........................................................................................62.1.3 EN55022 (CISPR 22) ...........................................................................................6

2.2 Federal Communications Commission ....................................................................62.2.1 FCC requirements summary .............................................................................6

3.0 Emissions Testing ................................................................................................ 73.1 Introduction ..................................................................................................................73.2 Conducted emissions testing....................................................................................73.3 Radiated emissions measurements preparation ................................................ 103.4 Setting up the equipment for radiated emissions measurements ................. 10

3.5 Performing radiated emissions measurements .................................................. 11

4.0 Problem Solving and Troubleshooting ............................................................ 134.1 Diagnostics testing setup ....................................................................................... 134.2 Problem isolation ..................................................................................................... 14

Appendix: A Line Impedance Stabilization Networks (LISN) ................................15A1.0 Purpose of a LISN ................................................................................................. 15

A1.1 LISN operation ................................................................................................ 15A1.2 Types of LISNs .................................................................................................. 16

A2.0 Transient limiter operation ................................................................................... 16

Appendix B: Antenna Factors ................................................................................ 17B1.0 Field strength units ............................................................................................... 17

B1.1 Antenna factors .............................................................................................. 17B1.2 Types of antennas used for commercial radiated measurements ........ 17

Appendix C: Basic Electrical Relationships ......................................................... 18

Appendix D: Detectors Used in EMI Measurements .......................................... 18D1.0 Peak detector ......................................................................................................... 18

D1.1 Peak detector operation ................................................................................. 18D2.0 Quasi-peak detector .............................................................................................. 19

D2.1 Quasi-peak detector operation ...................................................................... 19D3.0 Average detector ................................................................................................... 19

D3.1 Average detector operation ........................................................................... 19

Appendix E: EMC Regulatory Agencies ................................................................ 20

Glossary of Acronyms and Definitions ................................................................. 22

Table of Contents


3/24

3

The concept of getting a product tomarket on time and within budget isnothing new. Recently, companieshave realized that electromagnetic

interference (EMI) compliance testingcan be a bottleneck in the productdevelopment process. To ensure suc-cessful EMI compliance testing, pre-compliance testing has been addedto the development cycle. In precom-pliance testing, the electromagneticcompatibility EMC performance isevaluated from design through pro-duction units. Figure 1 illustrates atypical product development cycle.

Many manufacturers use (EMI)

measurement systems to performconducted and radiated EMI emis-sions evaluation prior to sending theirproduct to a test facility for full com-pliance testing. Conducted emissionstesting focuses on unwanted signalsthat are on the AC mains generatedby the equipment under test (EUT).

The frequency range for these com-mercial measurements is from 9 kHzto 30 MHz, depending on the regula-tion. Radiated emissions testing looks

for signals broadcast for the EUTthrough space. The frequency rangefor these measurements is between30 MHz and 1 GHz, and based on theregulation, can go up to 6 GHz andhigher. These higher test frequenciesare based on the highest internalclock frequency of the EUT. Thispreliminary testing is called precompli-ance testing.

Figure 2 illustrates the relationshipbetween radiated emissions, radi-

ated immunity, conducted emissionsand conducted immunity. Radiatedimmunity is the ability of a device orproduct to withstand radiated electro-magnetic fields. Conducted immunityis the ability of a device or productto withstand electrical disturbanceson AC mains or data lines. In order to

experience an electromagnetic com-patibility problem, such as when anelectric drill interferes with TV recep-tion, there must be a source or gen-

erator, coupling path and receptor. AnEMC problem can be eliminated byremoving one of these components.

With the advent of the Europeanrequirements, there is an additionalfocus on product immunity. The levelof electric field that a receptor canwithstand before failure is known asproduct immunity. The terms immu-nity and susceptibility are used inter-changeably. This document will notcover immunity testing.

1.0 Introduction to Radiated and Conducted Emissions Measurements

Figure 1. A typical product development cycle

Product development cycle

Initialinvestigation

Designbreadboard

Labprototype

Productionprototype

Productionunit

R E D E S I G N Production

Yespass pass pass passviable

NoNoNoNoNo

Yes

Emission Immunity = Susceptibility

ConductedRadiated

Figure 2. Electromagnetic compatibility between products


4/24

4

1.1 Precompliance versus fullcompliance EMI measurementsFull compliance measurementsrequire the use of a receiver that

meets the requirements set forthin CISPR16-1-1, a qualified openarea test site or semi anechoicchamber and an antenna tower andturntable to maximize EUT signals.Great effort is taken to get the bestaccuracy and repeatability. Thesefacilities can be quite expensive. Insome specific cases, the full com-pliance receiver can be replaced bya signal analyzer with the correctbandwidths and detectors as longas the signal analyzer has the sen-sitivity required.

Precompliance measurements areintended to give an approximationof the EMI performance of the EUT.The cost of performing precompli-

ance tests is a fraction of the costof full compliance testing using anexpensive facility.

The more attention to detail in themeasurement area, such as goodground plane and a minimal numberreflective objects, the better theaccuracy of the measurement.

1.2 Systems for performingprecompliance measurementsThe components used in systems forprecompliance measurements are as

follows: signal analyzer with N6141AEMI measurement application, lineimpedance stabilization network(LISN), transient limiter and anten-nas. To isolate problems after theyhave been identified, the close fieldprobes (11945A) are used.

The environment for precompliancetesting is usually less controlledthan full compliance testingenvironments. See Figure 3 for thecomponents used for precompli-ance testing.

EMI precompliance measurement system

A g i l e n t 1 1 9 4 7 A

X-Series analyzer with N6141AEMC measurement application

LISN

Log periodicantenna

Transient

limiter

Biconicalantenna

Tripod

MONITOR

POWER OUTPUT

CAUTION

HIGHVOLTAGE GND Close-eld probe set

HP 1194 0 A

H P 119 41A

Diagnostics

Figure 3. Components of a preproduction evaluation system


5/24

5

The precompliance measurementprocess is fairly straightforward.However, before making measure-ments on your product, some prelim-

inary questions must be answered.1. Where will the product be sold

(for example, Europe, UnitedStates, Japan)?

2. What is the classification of the prod-uct?a. Information technology

equipment (ITE)b. Industrial, scientific or

medical equipment (ISM)c. Automotive or communication

d. Generic (equipment not foundin other standards)

3. Where will the product be used(for example home, commercial,light industry or heavy industry)?

With the answers to these questions,you can determine which standardyour product must be tested against.For example, if you determined that

your product is an information tech-nology equipment (ITE) device, andyou are going to sell it in the U.S.,then you need to test your product tothe FCC 15 standard. Table 1 belowwill help you choose the requirementfor your product.

2.0 Precompliance Measurements Process

Emissions regulations (summary)

FCC CISPR

18 1112

15 13

14

15

15 22

EN 55011

EN 55013

EN 55014

EN 55015

EN 55022

EN61000-6-3,4

EN 55025

EN's Description

Industrial, scientic and medical equipmentAutomotive

Broadcast receivers

Household appliances/tools

Fluorescent lights/luminaries

16 Measurement apparatus/methods

16 Automotive component test

Information technology equipment

Generic emissions standards

Table 1. Comparison of regulatory agency requirements


6/24

6

2.1 European normsdescriptions

2.1.1 EN55011 (CISPR 11) ISM

Class A: Products used in establish-ments other than domestic areas.

Class B: Products suitable for use indomestic establishments.

Group 1: Laboratory, medical andscientific equipment. (For example:signal generators, measuringreceivers, frequency counters,spectrum analyzers, switching modepower supplies, weighing machinesand electron microscopes.)

Group 2: Industrial induction heatingequipment, dielectric heating equip-ment, industrial microwave heatingequipment, domestic microwaveovens, medical apparatus, spark ero-sion equipment and spot welders. (Forexample: metal melting, billet heating,component heating, soldering andbrazing, wood gluing, plastic welding,food processing, food thawing, paperdrying and microwave therapy equip-ment.)

2.1.2 EN55014 (CISPR 14)This standard applies to electricmotor-operated and thermal appli-ances for household and similarpurposes, electric tools and electricapparatus. Limit line use dependsupon the power rating of the item.EN55014 distinguishes betweenhousehold appliances, motors lessthan 700W, less than 1000W andgreater than 1000W. Limits forconducted emissions are 150 kHz to30 MHz, and limits for radiated emis-sions are 30 MHz to 300 MHz.

2.1.3 EN55022 (CISPR 22)Equipment with the primary functionof data entry, storage, displaying,retrieval, transmission, processing,

switching or controlling is consideredITE. For example, data processingequipment, office machines, elec-tronic equipment, business equipmentor telecommunications equipmentwould be considered ITE.

There are two classes of ITE, ClassA which is not intended for domesticuse and Class B which is intended fordomestic use.

2.2 Federal CommunicationsCommissionThe FCC has divided products to betested in two parts, Part 15 and Part

18. Part 15 is further divided intointentional radiators and unintentionalradiators.

Unintentional radiators include TVbroadcast receivers, FM receivers,cable system terminal devices, per-sonal computers and peripherals andexternal switching power supplies.Unintentional radiators are then againdivided into Class A devices that areused in industrial, commercial orbusiness environments and Class Bdevices that are marketed for use in aresidential environment.

Part 18 devices are ISM.

2.2.1 FCC requirements summaryThe frequency range of conductedemissions measurements is 450 kHzto 30 MHz and the frequency rangeof radiated emissions measurementsis 30 MHz to 1 GHz and up to 40 GHz,based on the device clock frequency.

Table 2. FCC requirements summary

FCC requirements (summary)

Equipment type FCC partBroadcast receivers Part 15Household appliances Part 15Fluorescent lights/luminaries Part 15Information technology equipment Part 15Equipment classication

Class A Industrial Part 15Class B Residential Part 15

Industrial, scientic and medical equipment Part 18


7/24

7

3.1 IntroductionAfter the appropriate regulationshave been identified, the next stepis to set up the test equipment and

perform radiated and conductedemissions tests. The first group oftests is conducted emissions. Thetypical process is to interconnect theappropriate equipment, load the limitline or lines, add the correction fac-tors for the LISN and transient limit.

3.2 Conducted emissions testing1. Interconnect the signal analyzer

to the limiter, LISN and EUT asshown in Figure 4. Operation of

the LISN and limiter is coveredin Appendix A. Ensure that thepower cord between the deviceunder test (DUT) and the LISN isas short as possible. The powercord can become an antennaif allowed to be longer thannecessary. Measure the signals onthe power line with the DUT off.If you see the signal approachingthe established limit lines, thensome additional shielding may berequired. Do not use ferrites on

the power cord because commonmode signals from the DUT may besuppressed causing a lower valuemeasurement.

2. Next, be sure you are measuringwithin the appropriate frequencyrange for conducted emissionsmeasurements, 150 kHz to 30 MHz.Agilents EMI measurementapplication uses a scan tableto make it easy to select theappropriate frequency range asshown in Figure 5. Deselect anyother ranges that are selected.

3.0 Emissions Testing

Figure 4. Conducted measurements interconnection


Limiter

Agilent 11967D LISN

Conducted emissions measurementsare easier than ever!

11947A

Deviceunder test

Figure 5. Scan table


8/24

88

3. Load limit lines and correctionfactors. In this case, the twolimit lines used for conductedemissions are EN55022 Class A

quasi-peak and EN55022 Class AEMI average. To compensate formeasurement errors, add a marginto both limit lines.

4. Correct for the LISN and thetransient limiter which is used toprotect the input mixer. The cor-rection factors for the LISN andtransient limiter are usually storedin the signal analyzer and they canbe easily recalled. View the ambi-ent emissions (with the DUT off).

If emissions above the limit arenoted, the power cord betweenthe LISN and the DUT may beacting as an antenna. Shortenthe power cord to reduce theresponse to ambient signals. SeeFigure 7.

5. Switch on the DUT to find sig-nals above the limit lines. Thisis a good time to check to makesure that the input of the signalanalyzer is not overloaded. To dothis, step the input attenuator upin value, if the display levels donot change, then there is no over-load condition. If the display doeschange, then additional attenuationis required. The margin is alsoset so signals above the marginwill also be listed. To identify thesignals above the margin of eitherlimit line, select scan and searchto get the peak amplitude andfrequency. The amplitude and fre-

quency of the signals is displayed.In this case, 14 signals were cap-tured.

Figure 6. Conducted emissions display with limit lines and margin

Figure 7. Conducted ambient emissions


9/24

99

6. Finally, the Quasi-peak and aver-age of the signals need to bemeasured and compared to theirrespective limits. There are three

detectors: Detector 1 will be setto peak, Detector 2 to Quasi-peakand Detector 3 to EMI average.

7. Review the measurement results.The QPD delta to Limit Line 1 andEAVE delta to Limit Line 2 shouldall have negative values. If someof the measurements are positive,then there is a problem with con-ducted emissions from the DUT.Check to be sure there is propergrounding if there are conducted

emissions problems. Long groundleads can look inductive at higherconducted frequencies generatedby switcher power supplies. Ifpower line filtering is used, makesure that it is well grounded.

Here are some additional hints whenmaking conducted measurements. Ifthe signals you are looking at are inthe lower frequency range of the con-ducted band (2 MHz or lower), youcan reduce the stop frequency to geta closer look. You may also note thatthere are fewer data points to view.You can add more data points bychanging the scan table. The defaultin the scan table is two data pointsper BW or 4.5 kHz per point. To getmore data points, change the pointsper bandwidth to 2.25 or 1.125 to givefour or eight points per BW.

Figure 8. Scan and search for signals above the limit

Figure 9. Quasi-peak and average delta to limit


10/24

10

3.3 Radiated emissionsmeasurements preparationPerforming radiated emissions mea-surements is not as straightforward

as performing conducted emissionsmeasurements. There is the addedcomplexity of the ambient environ-ment which could interfere withmeasuring the emissions from a DUT.There are some methods that can beused to discriminate between ambi-ent environment and signals from theDUT. In more populated metropolitanareas, ambient environments couldbe extremely dense, overpoweringemissions from a DUT. Testing in asemi-anechoic chamber can sim-plify and accelerate measurementsbecause the ambient signals are nolonger present. Chambers are anexpensive alternative to open areatesting. Following are some methodsfor determining if a signal is ambient:

1. The simplest method is to turnoff the DUT to see if the signalremains. However, some DUTs arenot easily powered down and up.

2. Use the tune and listen feature ofthe signal analyzer to determine if

the signal is a local radio station.This method is useful for AM, FMor phase modulated signals.

3. If your device is placed on aturntable, rotate the device whileobserving a signal in question. Ifthe signal amplitude remains con-stant during device rotation, thenthe signal is more likely to be anambient signal. Signals from a DUTusually vary in amplitude based onits position.

4. A more sophisticated method ofambient discrimination is the twoantenna method. Place one anten-

na at the prescribed distance ascalled out by the regulatory body,and a second antenna at twicethe distance of the first antenna.Connect the two antennas to aswitch, which is then connected tothe signal analyzer. If the signal isthe same amplitude at both anten-nas, then the signal is likely to bean ambient signal. If the signal atthe second antenna is 6 dB lower,then the signal originates from theDUT.

3.4 Setting up the equipmentfor radiated emissionsmeasurements 1. Arrange the antenna, DUT and

signal analyzer as shown in Figure10. Separate the antenna and theEUT as specified by the regulatoragency requirements. If space islimited, then the antenna can bemoved closer to the DUT and youcan edit the limits to reflect thenew position. For example, if theantenna is moved from 10 metersto 3 meters, then the amplitudemust be adjusted by 10.45 dB. Itis important that the antenna isnot placed in the near field of theradiating device which is /2 or15.9 MHz for 3 meters. Most com-mercial radiated emissions start at30 MHz.

2. Set up the signal analyzer for thecorrect span, bandwidths and limitlines with margin included. Afterthe signal analyzer has been pow-ered up and completed its calibra-tion, use the scan table to selectRange 3, and deselect all others.

This gives a frequency range of30 MHz to 300 MHz, bandwidthof 120 kHz and two data pointsper bandwidth. Load limit lines forEN55022 Class A. To get the bestsensitivity, switch on the signalanalyzers preamplifier and set theattenuator to 0 dB.

Figure 10. Radiated emissions test setup

Deviceunder test

BiconicalAntenna

Tripod

Precompliance Radiated Measurements



11/24

11

3.5 Performing radiatedemissions measurementsThe goal of radiated emissions test-ing is to identify and measure signals

emitting from the DUT. If the signalsmeasured using the correct detec-tor are below the margin set at thebeginning of the measurement, thenthe DUT passes. These measure-ments must be repeated for each faceof the DUT. The orientation changeof the DUT is achieved using a turn-table. The test sequence follows:

1. With the DUT off, perform a scanand search of the signals over theband of interest, and store the list

of frequency amplitude pairs to afile you may want to mark ambient.

2. With the DUT on and oriented atthe 0 degree position, perform ascan and search.

3. A second group of signals will beadded to the existing ambient sig-nals in the list.

4. Search for duplicates using themark all duplicates.

5. Delete the marked signal, whichnow leaves only the DUT signals(and those that were not presentduring the ambient scan).

Figure 11. Ambient radiated emissions signals

Figure 12. Duplicate ambient signals marked


12/24

Figure 13. Duplicate signals deleted

12

6. Perform measurements using theQP detector and compare to deltalimit.

7. If the signals are below the limit,then the DUT passes. If not, thensome work needs to be done toimprove emissions.

Store the signals shown in Figure 14for future reference when trouble-shooting problems.

Repeat the process, Step 1-7, foranother position of the turntable,such as 90 degrees. If you havestored the ambient signal in the previ-ous measurement, then you recall thelist and process with Step 2, which iswhere the DUT is switched on.

After you have observed the DUT onall four sides you will have a list ofsignals for each side. If you note asignal that is the same amplitude forall four sides of the DUT, it could bean ambient signal that was missedduring the ambient scan.

Figure 14. DUT signals with quasi-peak measurement compared to limit


13/24

After the product is tested and theresults are recorded and saved, yourproduct is either ready for full com-pliance testing and production, or it

must go back to the bench for furtherdiagnosis and repair.

If your product needs further rede-sign, the following process is recom-mended:

1. Connect the diagnostics tools asshown in Figure 15.

2. From your previous radiated tests,identify the problem frequencies.

3. Use the probe to locate the sourceor sources of the problem signals.

4. With the probe placed to give themaximum signal on the analyzer,save the trace to internal memory.

5. Make circuit changes as neces-sary to reduce the emissions.

6. Measure the circuit again usingthe same setting as before, andsave the results in another trace.

7. Recall the previously saved traceand compare the results to thecurrent measurement.

4.1 Diagnostics testing setupIt is recommended that the spectrumanalyzer mode be used for diagnosis.Correction factors for the probe

should be loaded from the internalmemory. The Agilent 11945A probekit contains two probes, one for 9 kHzto 30 MHz and another for 30 MHzto 1 GHz frequency range. Place thesignal analyzer into the spectrumanalyzer mode. Connect the probefor the appropriate frequency rangeand recall the correction factors frominternal memory.

13

4.0 Problem Solving and Troubleshooting

Figure 15. Diagnostics setup interconnection

Diagnostic measurement set-up: emissions

Close-eld probe

Device under test

Circuit under test

H P11940 A



14/24

1414

4.2 Problem isolationUsing information stored earlier fromthe conducted and radiated tests,tune the signal analyzer to one of the

problem frequencies with a narrowenough span to give adequate dif-ferentiation between signals. Movethe close field probe slowly over theDUT. Observe the display for maxi-mum emissions as you isolate thesource of the emissions. After youhave isolated the source of the emis-sions, record the location and storethe display to an internal register.See Figure 16 .

The next step is to make designchanges to reduce emissions. Thiscan be accomplished by addingor changing circuit components,redesigning the problem circuit oradding shielding. After the redesign,compare the results again to thepreviously recorded trace.

With your probe on the trouble spot,compare the emissions before andafter repairing the problem. As youcan see from the difference between

the two traces in Figure 17, there hasbeen about a 10 dB improvement inthe emissions. There is a one-to-onecorrelation between changes inclose field probe measurements andchanges in far field measurements.For example, if you note a 10 dBchange in measurements made by aclose field probe, you will also note a10 dB change when you perform a farfield measurement using an antennaand a signal analyzer.

Figure 16. Preliminary diagnostics trace

Figure 17. Diagnostics traces before and after redesign


15/24

15

A1.0 Purpose of a LISNA line impedance stabilization net-work serves three purposes:

1. The LISN isolates the powermains from the equipment undertest. The power supplied to theEUT must be as clean as pos-sible. Any noise on the line willbe coupled to the X-Series signalanalyzer and interpreted as noisegenerated by the EUT.

2. The LISN isolates any noisegenerated by the EUT from beingcoupled to the power mains.Excess noise on the power mainscan cause interference with theproper operation of other deviceson the line.

3. The signals generated by theEUT are coupled to the X-Seriesanalyzer using a high-pass fil-ter, which is part of the LISN.Signals that are in the pass bandof the high-pass filter see a 50-load, which is the input to theX-Series signal analyzer.

A1.1 LISN operationThe diagram in Figure A-1 belowshows the circuit for one side of theline relative to earth ground.

The 1 F in combination with the 50H inductor is the filter that isolatesthe mains from the EUT. The 50 Hinductor isolates the noise generatedby the EUT from the mains. The0.1 F couples the noise generatedby the EUT to the X-Series signal

analyzer or receiver. At frequenciesabove 150 kHz, the EUT signals arepresented with a 50- impedance.

The chart in Figure A-1 representsthe impedance of the EUT port ver-sus frequency.

Figure A-1. Typical LISN circuit diagram

Appendix A: Line Impedance Stabilization Networks (LISN)

Line Impedance Stabilization Network (LISN)

605040302010

.01 .1 1 10 100

Impedance(ohms)

Frequency (MHz)

0.1 F1000

From power source To EUT

To Receiver or EMC analyzer (50 )

50 H

1 F


16/24

16

A1.2 Types of LISNsThe most common type of LISN isthe V-LISN. It measures the unsym-metric voltage between line and

ground. This is done for both the hotand the neutral lines or for a three-phase circuit in a Y configuration,between each line and ground. Thereare other specialized types of LISNs.A delta LISN measures the line-to-line or symmetric emissions voltage.The T-LISN, sometimes used for tele-communications equipment, mea-sures the asymmetric voltage, whichis the potential difference betweenthe midpoint potential between twolines and ground.

A2.0 Transient limiter operationThe purpose of the limiter is to pro-tect the input of the EMC analyzerfrom large transients when connect-

ed to a LISN. Switching EUT poweron or off can cause large spikesgenerated in the LISN.

The Agilent 11947A transient limiterincorporates a limiter, high-passfilter, and an attenuator. It can with-stand 10 kW for 10 sec and hasa frequency range of 9 kHz to 200MHz. The high-pass filter reducesthe line frequencies coupled to theEMC analyzer.

Figure A-2. Three different types of LISNs

Types of LISNs

V-LISN:-LISN:

T-LISN:

Unsymmetric emissions (line-to-ground)Symmetric emissions (line-to-line)Asymmetric emissions (mid point line-to-line)

V-LISN Vector Diagram

V symmetric

Ground

H N

V u n s y m m e t r i c

1

V 2 u n

s y m m

e t r i c

1 / 2 V s y m m e t r i c 1 / 2 V s y m m e t r i c

V u n s y m m e t r i c

1

V unsymmetric2V asymmetric


17/24

17

B1.0 Field strength unitsRadiated EMI emissions measure-ments measure the electric field.The field strength is calibrated in

dBV/m. Field strength in dBV/mis derived from the following:

Pt = total power radiated from anisotropicradiator

PD = the power density at a dis-tance r from the isotropicradiator (far field)

PD = P t /4r 2

R = 120

PD = E2

/RE2/R = P t /4r 2

E = (Pt x 30)1/ 2 /r (V/m)

Far field1 is considered to be >/2

B1.1 Antenna factorsThe definition of antenna factorsis the ratio of the electric field involts per meter present at the plane

of the antenna versus the voltageout of the antenna connector. Note:Antenna factors are not the same asantenna gain.

B1.2 Types of antennas used forcommercial radiated measurementsThere are three types of antennasused for commercial radiated emis-

sions measurements.Biconical antenna: 30 MHz to300 MHz

Log periodic antenna: 200 MHz to1 GHz (the biconical and log periodicoverlap frequency)

Broadband antenna: 30 MHz to1 GHz (larger format than the biconi-cal or log periodic antennas)

Antenna factors

Linear units:

dB/m

Frequency, MHz

5

10

15

20

25

0 200 400 600 800 1000

Biconical@ 10m

Log Periodic@ 1m

AF = Antenna factor (1/m)E = Electric eld strength (V/m)V = Voltage output from antenna (V)

Log units: AF(dB/m) = E(dBV/m) - V(dBV)E(dBV/m) = V(dBV) + AF(dB/m)

AF = EinV out

30

Log Periodic Antenna

Biconical Antenna

Broadband Antenna

(30 - 300 MHz)

(30 - 1000 MHz)(200 - 1000 MHz)

Figure B-2. Antennas used in EMI emissions measurements

Figure B-1. Typical antenna factor shapes

Appendix B: Antenna Factors

1. Far eld is the minimum distance from a radiator where the eldbecomes a planar wave.


18/24

18

The decibel is used extensively inelectromagnetic measurements. Itis the log of the ratio of two ampli-tudes. The amplitudes are in power,voltage, amps, electric field unitsand magnetic field units.

decibel = dB = 10 log (P 2/P 1)

Data is sometimes expressed involts or field strength units. In thiscase, replace P with V2/R.

If the impedances are equal, the

equation becomes:dB = 20 log (V2/V 1)

A unit of measure used in EMI mea-surements is dBV or dBA. Therelationship of dBV and dBm is asfollows:

dBV = 107 + PdBm

This is true for an impedance of 50.

Wave length (l) is determined using

the following relationship: = 3x108/f (Hz) or =300/f (MHz)

D1.0 Peak detectorInitial EMI measurements are madeusing the peak detector. This modeis much faster than quasi-peak, oraverage modes of detection. Signalsare normally displayed on spectrumanalyzers or EMC analyzers in peakmode. Since signals measured inpeak detection mode always haveamplitude values equal to or higherthan quasi-peak or average detec-tion modes, it is a very easy processto take a sweep and compare theresults to a limit line. If all signalsfall below the limit, then the prod-uct passes and no further testing isneeded.

D1.1 Peak detector operationThe EMC analyzer has an envelopeor peak detector in the IF chain thathas a time constant, such that thevoltage at the detector output fol-lows the peak value of the IF signalat all times. In other words, thedetector can follow the fastest pos-sible changes in the envelope of theIF signal, but not the instantaneousvalue of the IF sine wave.(See Figure D-1.)

Figure D-1. Peak detector diagram

Output of the envelope detector followsthe peaks of the IF signal

Appendix C:Basic ElectricalRelationships

Appendix D: Detectors Used in EMI Measurements


19/24

19

D2.0 Quasi-peak detectorMost radiated and conducted limitsare based on quasi-peak detectionmode. Quasi-peak detectors weigh

signals according to their repetitionrate, which is a way of measuring theirannoyance factor. As the repetitionrate increases, the quasi-peak detec-tor does not have time to dischargeas much, resulting in a higher voltageoutput. (See Figure D-2.) For continu-ous wave (CW) signals, the peak andthe quasi-peak are the same.

Since the quasi-peak detector alwaysgives a reading less than or equal topeak detection, why not use quasi-peak detection all the time? Wontthat make it easier to pass EMI tests?Its true that you can pass the testsmore easily; however, quasi-peak mea-surements are much slower by two orthree orders of magnitude comparedto using the peak detector.

D2.1 Quasi-peak detector operationThe quasi-peak detector has a chargerate much faster than the dischargerate; therefore, the higher the repeti-

tion rate of the signal, the higher theoutput of the quasi-peak detector.The quasi-peak detector also respondsto different amplitude signals in alinear fashion. High-amplitude, low-repetition-rate signals could producethe same output as low-amplitude,high-repetition-rate signals.

D3.0 Average detectorThe average detector is required forsome conducted emissions tests inconjunction with using the quasi-peakdetector. Also, radiated emissionsmeasurements above 1 GHz are per-formed using average detection. Theaverage detector output is always lessthan or equal to peak detection.

D3.1 Average detector operationAverage detection is similar in manyrespects to peak detection. Figure D-3shows a signal that has just passed

through the IF and is about to bedetected. The output of the envelopedetector is the modulation envelope.Peak detection occurs when the postdetection bandwidth is wider thanthe resolution bandwidth. For aver-age detection to take place, the peakdetected signal must pass through afilter whose bandwidth is much lessthan the resolution bandwidth. Thefilter averages the higher frequencycomponents, such as noise at the out-put of the envelope detector.

Figure D-2. Quasi-peak detector response diagram Figure D-3. Average detection response diagram

Quasi-peak detector output varieswith impulse rate

t

Peak response detector reading detector response

t

Test limit

Test limit

Quasi-peakQuasi-peak

Average detection

A

t

Envelope detector

Filters

Average detector


20/24

20

Appendix E

EMC regulatory agenciesThe following is a list of address andphone numbers for obtaining EMCregulation information.

IECCISPRSales Department of the Central Office of the IEC PO Box 1313, Rue de Verembe1121 Geneva 20, SwitzerlandIEC www.iec.chCISPR (http://www.iec.ch/zone/emc/emc_cis.htm#guide)

ITU-R (CCIR)ITU, General Secretariat, Sales ServicePlace de Nation1211 Geneva, SwitzerlandTelephone: +41 22 730 5111

(ITU Switchboard)Fax: +41 22 733 7256http://www.itu.int/ITU-R

Australia Australia Electromechanical Committee Standards Associationof AustraliaPO Box 458North Sydney N.S.W. 2060Telephone: +61 2 963 41 11Fax: +61 2 963 3896AustraliaElecto-technical Committee(http://www.ihs.com.au/stan-dards/iec/)

BelgiumComite Electrotechnique BelgeBoulevard A. Reyerslaan, 80B-1030 BRUSSELSTelephone: Int +32 2 706 85 70

Fax: Int +32 2 706 85 80http://www.bec-ceb.be

CanadaStandards Council of CanadaStandards Sales Division270 Albert Street, Suite 200Ottawa, Ontario K1P 6N7Telephone: 613 238 3222Fax: 613 569 7808http://www.scc.ca

Canadians Standards Association(CSA)5060 Spectrum WayMississauga, Ontario

L4W 5N6CANADATelephone: 416 747 4000

800 463 6727Fax: 416 747 2473http://www.csa.ca

DenmarkDansk Elektroteknisk KomiteStrandgade 36 stDK-1401 Kobenhavn KTelephone: +45 72 24 59 00Fax: +45 72 24 59 02

http://www.en.ds.dk

FranceComite Electrotechnique FrancaisUTE CEdex 64F-92052 Paris la DefenseTelephone: +33 1 49 07 62 00Fax: +33 1 47 78 71 98http://www.ute-fr.com/FR

GermanyVDE VERLAG GmbH Bismarckstr. 3310625 BerlinTelephone: + 49 30 34 80 01 - 0

(switchboard)Fax: + 49 30 341 70 93email: [email protected]

IndiaBureau of Indian Standards, SalesDepartment Manak Bhavan9 Bahadur Shah Zafar Marg.New Delhi 110002

Telephone: + 91 11 331 01 31Fax: + 91 11 331 40 62http://www.bis.org.in

ItalyCEI-Comitato Elettrotecnico ItalianoSede di MilanoVia Saccardo, 9

20134 MilanoTelephone: 02 21006.226Fax: 02 21006.222http://www.ceiweb.it

JapanJapanese Standards Association1-24 Akasaka 4Minato-KuTokyo 107Telephone: + 81 3 583 8001Fax: + 81 3 580 14 18(http://www.jsa.or.jp/default_eng-

lish.asp)

NetherlandsNederlands Normalisatie-Instituut Afd. Verdoop en InformatieKalfjeslaan 2, PO Box 50592600 GB DelftNLTelephone: (015) 2 690 390Fax: (015) 2 690 190www.nni.nl

NorwayNorsk Elektroteknisk KomiteHarbizalleen 2APostboks 280 SkoyenN-0212 Oslo 2Telephone: 67 83 87 00Fax: 67 83 87 01(http://www.standard.no/imaker.exe?id=4170)


21/24

21

South AfricaSouth African Bureau of StandardsElectronic Engineering DepartmentPrivate Bag X191

Pretoria0001 Republic of South Africa(https://www.sabs.co.za/Sectors/Electrotechnical/index.aspx)

SpainComite Nacional Espanol de la CEI Francisco Gervas 3E-28020 MadridTelephone: + 34 91 432 60 00Fax: + 34 91 310 45 96http://www.aenor.es

SwedenSvenska Elektriska KommissionenPO Box 1284S-164 28 Kista-StockholmTelephone: 08 444 14 00Fax: 08 444 14 30(http://www.elstandard.se/stan-darder/emc_standarder.asp)

SwitzerlandSwiss Electrotechnical CommitteeSwiss Electromechanical AssociationLuppmenstrasse 1CH-8320 FehraltorfTelephone: + 41 44 956 11 11Fax: + 41 44 956 11 22http://www.electrosuisse.ch/

United KingdomBSI Standards389 Chiswick High RoadLondonW4 4ALUnited KingdomTelephone: +44 (0)20 8996 9001

Fax: +44 (0)20 8996 7001www.bsi-global.com

British Defence StandardsDStan Helpdesk UKDefence StandardizationRoom 1138

Kentigern House65 Brown StreetGlasgowG2 8EXTelephone: +44 (0) 141 224 2531Fax: +44 (0) 141 224 2503http://www.dstan.mod.uk

United States of America America National Standards InstituteInc.Sales Dept.1430 Broadway

New York, NY 10018Telephone: 212 642 4900Fax: 212 302 1286(http://webstore.ansi.org/ansidocs-tore/default.asp)

FCC Rules and RegulationsTechnical Standards Branch2025 M Street N.W.MS 1300 B4Washington DC 20554Telephone: 202 653 6288http://www.fcc.gov

FCC Equipment Authorization Branch7435 Oakland Mills RoadMS 1300-B2Columbia, MD 21046Telephone: 301 725 1585http://www.fcc.gov


22/24

22

Ambient level1. The values of radiated and

conducted signal and noiseexisting at a specified test

location and time when thetest sample is not activated.2. Those levels of radiated and

conducted signal and noiseexisting at a specified testlocation and time when thetest sample is inoperative.Atmospherics, interferencefrom other sources, and circuitnoise, or other interferencegenerated within the measuringset compose the ambient level.

Amplitude modulation1. In a signal transmission system,

the process, or the result of theprocess, where the amplitude ofone electrical quantity is varied inaccordance with some selectedcharacteristic of a secondquantity, which need not beelectrical in nature.

2. The process by which theamplitude of a carrier wave isvaried following a specified law.

Anechoic chamber1. A shielded room which is lined

with radio absorbing material toreduce reflections from all internalsurfaces. Fully lined anechoicchambers have such material onall internal surfaces, wall, ceilingand floor. Its also called a fullyanechoic chamber. A semi-anechoic chamber is a shieldedroom which has absorbingmaterial on all surfaces except

the floor.

Antenna (aerial)1. A means for radiated or receiving

radio waves.2. A transducer which either emits

radio frequency power into spacefrom a signal source or intercepts anarriving electromagnetic field,converting it into an electrical signal.

Antenna factorThe factor which, when properlyapplied to the voltage at the inputterminals of the measuring instru-

ment, yields the electric fieldstrength in volts per meter and amagnetic field strength in amperesper meter.

Antenna induced voltageThe voltage which is measured orcalculated to exist across the opencircuited antenna terminals.

Antenna terminal conducted inter-ferenceAny undesired voltage or current

generated within a receiver, trans-mitter, or their associated equipmentappearing at the antenna terminals.

Auxiliary equipmentEquipment not under test that isnevertheless indispensable for settingup all the functions and assessingthe correct performance of the EUTduring its exposure to thedisturbance.

BalunA balun is an antenna balancingdevice, which facilitates use of coax-ial feeds with symmetrical antennaesuch as a dipole.

Broadband emissionBroadband is the definition for aninterference amplitude when severalspectral lines are within the RFIreceivers specified bandwidth.

Broadband interference

(measurements)A disturbance that has a spectralenergy distribution sufficiently broad,so that the response of the measuringreceiver in use does not vary signifi-cantly when tuned over a specifiednumber of receiver bandwidths.

Conducted interferenceInterference resulting from conductedradio noise or unwanted signalsentering a transducer (receiver) by

direct coupling.

Cross couplingThe coupling of a signal from onechannel, circuit, or conductor toanother, where it becomes anundesired signal.

Decoupling networkA decoupling network is an electri-cal circuit for preventing test signalswhich are applied to the EUT fromaffecting other devices, equipment,

or systems that are not under test.IEC 801-6 states that the couplingand decoupling network systemscan be integrated in one box or theycan be in separate networks.

Dipole1. An antenna consisting of a straight

conductor usually not more than ahalf-wavelength long, divided atits electrical center for connectionto a transmission line.

2. Any one of a class of antennasproducing a radiation patternapproximating that of anelementary electric dipole.

Electromagnetic compatibility(EMC)1. The capability of electronic

equipment of systems to beoperated within defined marginsof safety in the intendedoperating environment atdesigned levels of efficiency

without degradation due tointerference.2. EMC is the ability of equipment

to function satisfactorily inits electromagnetic environmentwithout introducing intolerabledisturbances into thatenvironment or into otherequipment.

Glossary of Acronyms and Definitions


23/24

23

Electromagnetic interferenceElectromagnetic interference is theimpairment of a wanted electromag-netic signal by an electromagnetic

disturbance.

Electromagnetic waveThe radiant energy produced by theoscillation of an electric charge char-acterized by oscillation of the electricand magnetic fields.

EmissionElectromagnetic energy propagatedfrom a source by radiation or conduc-tion.

Far fieldThe region where the power fluxdensity from an antenna approxi-mately obeys an inverse squares lawof the distance. For a dipole this cor-responds to distances greater thanl/2 where l is the wave length of theradiation.

Ground plane1. A conducting surface or plate

used as a common referencepoint for circuit returns andelectric or signal potentials.

2. A metal sheet or plate used asa common reference point forcircuit returns and electrical orsignal potentials.

Immunity1. The property of a receiver or any

other equipment or systemenabling it to reject a radiodisturbance.

2. The ability of electronic

equipment to withstand radiatedelectromagnetic fields withoutproducing undesirable responses.

IntermodulationMixing of two or more signals in anonlinear element, producing signalsat frequencies equal to the sums anddifferences of integral multiples ofthe original signals.

IsotropicIsotropic means having properties ofequal values in all directions.

MonopoleAn antenna consisting of a straightconductor, usually not more thanone-quarter wave length long, mount-ed immediately above, and normalto, a ground plane. It is connected toa transmission line at its base andbehaves, with its image, like a dipole.

Narrowband emissionThat which has its principal spectralenergy lying within the bandpass ofthe measuring receiver in use.

Open areaA site for radiated electromagneticinterference measurements whichis open flat terrain at a distancefar enough away from buildings, elec-tric lines, fences, trees, undergroundcables, and pipe lines so that effectsdue to such are negligible. This siteshould have asufficiently low level of ambientinterference to permit testing to therequired limits.

PolarizationA term used to describe the orienta-tion of the field vector of a radiatedfield.

Radiated interferenceRadio interference resulting fromradiated noise of unwanted signals.Compare radio frequency interfer-ence below.

RadiationThe emission of energy in the form ofelectromagnetic waves.

Radio frequency interferenceRFI is the high frequency interferencewith radio reception. This occurswhen undesired electromagneticoscillations find entrance to thehigh frequency input of a receiveror antenna system.

RFI sourcesSources are equipment and systemsas well as their components whichcan cause RFI.

Shielded enclosureA screened or solid metal housingdesigned expressly for the purpose ofisolating the internal from the exter-nal electromagnetic environment.The purpose is to prevent outsideambient electromagnetic fields fromcausing performance degradation andto prevent emissions from causinginterference to outside activities.

Stripline

Parallel plate transmission line to gen-erate an electromagnetic field for test-ing purposes.

SusceptibilitySusceptibility is the characteristicof electronic equipment that permitsundesirable responses when sub-jected to electromagnetic energy.


24/24

For more information on Agilent Technologiesproducts, applications or services, pleasecontact your local Agilent office. The completelist is available at:

www.agilent.com/nd/contactus

AmericasCanada (877) 894 4414Brazil (11) 4197 3500Latin America 305 269 7500Mexico 01800 5064 800United States (800) 829 4444

Asia PacicAustralia 1 800 629 485China 800 810 0189Hong Kong 800 938 693India 1 800 112 929Japan 0120 (421) 345Korea 080 769 0800Malaysia 1 800 888 848Singapore 1 800 375 8100Taiwan 0800 047 866Thailand 1 800 226 008

Europe & Middle EastAustria 43 (0) 1 360 277 1571Belgium 32 (0) 2 404 93 40Denmark 45 70 13 15 15Finland 358 (0) 10 855 2100France 0825 010 700*

*0.125 /minuteGermany 49 (0) 7031 464 6333Ireland 1890 924 204Israel 972-3-9288-504/544Italy 39 02 92 60 8484Netherlands 31 (0) 20 547 2111Spain 34 (91) 631 3300Sweden 0200-88 22 55Switzerland 0800 80 53 53United Kingdom 44 (0) 118 9276201Other European Countries:www.agilent.com/nd/contactusRevised: July 8, 2010

Product specifications and descriptionsin this document subject to changewithout notice.

Agilent Technologies, Inc. 2010Printed in USA, July 12, 20105990-6152EN

www.agilent.comwww.agilent.com/find/emc

Agilent Advantage Services is com-mitted to your success throughoutyour equipments lifetime. We sharemeasurement and service expertiseto help you create the products thatchange our world. To keep you com-petitive, we continually invest in toolsand processes that speed up calibra-tion and repair, reduce your cost ofownership, and move us ahead ofyour development curve.

www.agilent.com/find/advantageservices

Agilent Email Updates

www.agilent.com/find/emailupdatesGet the latest information on the

products and applications you select.

www.lxistandard.orgLXI is the LAN-based successor toGPIB, providing faster, more efficientconnectivity. Agilent is a foundingmember of the LXI consortium.

Agilent Channel Partnerswww.agilent.com/find/channelpartnersGet the best of both worlds: Agilentsmeasurement expertise and productbreadth, combined with channelpartner convenience.

www.agilent.com/quality

Quality Management SystemQuality Management SysISO 9001:2008

AgilentElectronic MeasurementGroup

KEMA Certied

Making Conducted and Radiated Emissions Measurements

Documents

Transcript of Making Conducted and Radiated Emissions Measurements