Agilent AN 1302

Making Radiated and ConductedCompliance Measurements withEMI Receivers Application Note

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Table of Contents

3 1.0 Introduction to compliance measurements3 2.0 The compliance measurements process5 3.0 Compliance EMI receiver requirements6 3.1 Requirements above 1 GHz6 4.0 Preparing for conducted emissions measurements6 4.1 Conducted test setup6 4.2 Configuring the receiver7 4.3 Performing conducted emissions measurements9 5.0 Preparing for radiated emissions measurements

10 5.1 Open site requirements10 5.2 Radiated emissions test setup11 5.3 Measuring radiated emissions12 5.4 Ambient signal measurements12 5.5 Placement of EUT for maximum signals13 5.6 Ambient plus EUT measurements14 5.7 Evaluating measurement results15 6.0 Report development15 6.1 Using the Agilent 85878A report generator software16 7.0 Using software to improve radiated EMI test throughput

18 Appendix ALine impedance stabilization networks

19 Appendix B Antenna factors

20 Appendix CBasic electrical relationships

21 Appendix D Detectors used in EMI measurements

23 Appendix EEMC regulatory agencies

25 Glossary of acronyms and definitions

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1.0 Introduction to compliance measurementsNote: In this application note, detailed measure-ment procedures are provided for AgilentTechnologies 8542E and 8546A EMI receivers.

Any product that uses the public power grid or haselectronic circuitry must pass EMC (electromagnet-ic compatibility) requirements. These requirementsfall into four broad types of testing: radiated andconducted emissions testing, and radiated and con-ducted immunity testing.

Conducted emissions testing focuses on signalspresent on the AC mains that are generated by theequipment under test (EUT). The frequency rangeof these measurements is typically 9 kHz to 30 MHz.

Radiated emissions testing looks for signals beingemitted from the EUT through space. The typicalfrequency range for these measurements is 30 MHzto 1 GHz, although FCC regulations require testingup to 200 GHz for an intentional radiator (such asa wireless transmitter) operating at a center fre-quency above 30 GHz.

Figure 1 illustrates the difference between radiatedemissions, radiated immunity, conducted emis-sions, and conducted immunity. Radiated immunityis the ability of a device or product to withstandradiated electromagnetic fields. Conducted immuni-ty is the ability of a device or product to withstandelectrical disturbances on power or data lines.Immunity testing will not be covered in this docu-ment.

For an electromagnetic compatibility problem tooccur (such as when an electric drill interfereswith TV reception), there must be a generator orsource, a coupling path and a receptor. Untilrecently, most efforts to remove EMC problemshave focused on reducing the emissions of thesource to an acceptable level.

Figure 1. Two types of EMC measurements

2.0 The compliance measurements processBefore compliance measurements can be per-formed on a product, some preliminary questionsmust be answered:

1. Where will the product be sold (i.e., the UnitedStates, Europe, Japan)?

2. What is the classification of the product (i.e.information technology equipment (ITE); indus-trial, scientific or medical (ISM); automotive andcommunications)?

3. Where will the product be used (i.e., home, com-mercial, light industry or heavy industry)?

With the answers to the above questions, you candetermine which testing requirements apply toyour product by referring to Tables 1a and 1bbelow. For example, if you have determined thatyour product is an information technology (ITE)device and you will sell it in the U.S. then you needto test the product to FCC part 15 regulations.

International regulations summary (Emissions)

CISPR FCC EN’s Description

11 Part 18 EN 55011 Industrial, scientific and medical12 (SAE) automotives13 Part 15 EN 55013 Broadcast receivers14 EN 55014 Household appliances/tools15 EN 55015 Fluorescent lights/luminaries16 Measurement apparatus/methods22 Part 15 EN 55022 Information technology equipment

EN 50081-1,2 Generic emissions standards

Table 1a. Comparison of regulatory agency requirements.

Emission Immunity = Susceptibility

ConductedRadiated

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European norms

Equipment type Emissions

Generic equipment EN 50081-1ResidentialLight industrial

Industrial EN 50081-2Information technology equipment (ITE) EN 55022Industrial, scientific, medical products (ISM) EN 55011

Table 1b. Major European requirements

European normsEN55011 (CISPR 11)Industrial, scientific, and medical productsClass A: Used in establishments other than domestic areasClass B: Suitable for use in domestic establishments

Group 1: Laboratory, medical, and scientific equip-ment. (For example, signal generators, measuringreceivers, frequency counters, spectrum analyzers,switching mode power supplies, weighingmachines, and electronic microscopes.)

Group 2: Industrial induction heating equipment,dielectric heating equipment, industrial microwaveheating equipment, domestic microwave ovens,medical apparatus, spark erosion equipment, andspot welders. (For example, metal melting, billetheating, component heating, soldering and brazing,wood gluing, plastic welding, food processing, foodthawing, paper drying, and microwave therapyequipment.)

EN55014 (CISPR 14)Electric motor-operated and thermal appliances forhousehold and similar purposes, electric tools, andelectric apparatus. Depending on the power ratingof the item being tested, use one of the limitsshown here:

DOS disk file names

Household and similar appliances (conducted) EN014-HLHousehold and similar appliances (radiated) EN014-HHMotors < 700W (conducted) EN014-P1Motors < 700W (radiated) EN014-P4Motors < 1000W (conducted) EN014-P2Motors < 1000W (radiated) EN014-P5Motors > 1000W (conducted) EN014-P3Motors > 1000W (radiated) EN014-P6

Note: The conducted range is 150 kHz to 30 MHz and the radiated range is30 MHz to 300 MHz.

EN55022 (CISPR 22)Information technology equipmentEquipment with the primary function of dataentry, storage, displaying, retrieval, transmission,processing, switching or controlling. (For example,data processing equipment, office machines, elec-tronic business equipment, and telecommunica-tions equipment.)

Class A ITE: Not intended for domestic use.Class B ITE: Intended for domestic use.

FCC (Federal Communications Commission)

Equipment FCC

Broadcast receivers Part 15Household appliances/toolsFluorescent lights/luminariesInformation technology equipment (ITE)Industrial, scientific, medical products (ISM) Part 18Conducted measurements: 450 kHz - 30 MHzRadiated measurements: 30 MHz - 1000 MHz, 40 GHz

Table 1c. FCC regulations

Federal Communications CommissionFCC Part 15Radio frequency devices-unintentional radiators (For example, TV broadcast receivers, FM broad-cast receivers, CB receivers, scanning receivers, TVinterface device, cable system terminal device,Class B personal computers and peripherals, ClassB digital devices, Class A digital devices andperipherals, and external switching power sup-plies).

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Class A digital devices are marketed for use in acommercial, industrial or business environment.

Class B digital devices are marketed for use in aresidential environment.

For assistance, call the agency for conformation ofthe applicable requirement. (A list of phone num-bers is included in Appendix E).

3.0 Compliance EMI receiver requirementsThere are several requirements for making compli-ance EMI measurements. The first is an EMIreceiver that meets CISPR 16.1

A CISPR 16 receiver must have the following func-tionality in the range 9 kHz - 1000 MHz:

• Amplitude accuracy: Nominally a ±2 dB absolute amplitude accuracyis required

• Specified bandwidths: CISPR specifies the following bandwidths (16 dB):

Bandwidth Frequency range

200 Hz 9 kHz - 150 kHz9 kHz 150 kHz - 30 MHz120 kHz 30 MHz - 1000 MHz

The frequency response of the filters must also fallwithin a “mask” defined by CISPR 16.

• Specified detectors: Peak, quasi-peak, and aver-age (see Appendix D for a description of thesedetectors). The charge, discharge time andmeter constants of the quasi-peak detector arespecified.

• Specified input impedance, nominal value of 50ohms; deviations specified as VSWR.

• Pass product immunity in a 3 V/m field.• Ability to pass the “CISPR pulse test.”• Other specific harmonic and intermodulation

requirements.

The CISPR pulse test consists of broadband pulsesof a defined spectral intensity of varying repetitionfrequency presented to the EMI receiver. Thequasi-peak detector must measure these pulses ata specific level within a specified accuracy. Inorder to meet this pulse test, it is implied, but notspecified, that the receiver must have:

• Preselection: Preselection is achieved by inputfilters that track the receiver tuning to reducebroadband noise overload at the front endmixer.

• Sensitivity and dynamic range. The EMI receivermust have a noise floor low enough to measuresignals at low PRFs.

Note: Although high sensitivity and dynamicrange capabilities are implied to meet the CISPRpulse test, actual numbers for these parametersare not specified.

A recommended feature for ensuring accuratemeasurements is overload detection. To make anaccurate measurement, the receiver must be in lin-ear operating mode and not be in saturation at thefront-end mixer because of large narrowband sig-nals or broadband emissions. A useful overloaddetection scheme will alert the user to overloadconditions in all frequency ranges and in all modesof operation. An advanced overload detection andmeasurement scheme will “autorange”, or automat-ically put in enough attenuation prior to the firstmixer to measure the signal in non-overload condi-tions.

The Agilent 8542E and 8546A were independentlycertified to meet these CISPR-16 requirements bythe German BZT.2 These receivers also containautoranging capabilities and overload detection inall frequency ranges and modes of operation.

1. Comite International Special des Perturbations Radioelectriques2. Bundesamt für Zulassungen der Telekommunikution, the German Appeals Office

for Telecommunications

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3.1 Requirements above 1 GHz:FCC regulations and proposed CISPR regulationsrequire a 1 MHz bandwidth for measurementsabove 1 GHz. The Agilent 8542E and 8546Areceivers also meet these requirements.

In addition, no quasi-peak detector is required formeasurements above 1 GHz. The CISPR pulse testis not required above 1 GHz, but high sensitivity inthe measuring system is important to achieve suffi-cient dynamic range to perform the measurements.

According to current FCC regulations, the maxi-mum test frequency is the fifth harmonic of thehighest clock frequency for an “unintentional radi-ator” (for example, a computer) and the tenth har-monic for an intentional radiator (such as a cellu-lar phone or wireless LAN).

4.0 Preparing conducted emissions measurementsEmissions testing is divided into conducted emis-sions and radiated emissions testing. Follow thesesteps to set up the equipment and the equipmentunder test.

4.1 Conducted test setupANSI C63.4 describes a specific test setup for con-ducted emissions. FCC Part 15 details the limitsfor these tests. Figure 2 shows a setup for a per-sonal computer, requiring a test to CISPR 22 orFCC part 15 (Class B):

Figure 2: Side view of conducted test setup. The LISN out-put connects to the receiver.

Figure 3: Top view of conducted test setup. The LISN out-put connects to the receiver.

CISPR 22 shows a similar conducted test setup forEuroNorms (ENs).

Interconnect the EMI receiver, LISN and EUT asshown in Figure 3. The function of a LISN isdetailed in Appendix A.

Note: The setup does not include a separate tran-sient limiter for transient protection. The 8542Eand 8546A have built-in transient limiters.

4.2 Configuring the receiverNote: The following sequence of steps for making acompliant measurement with the EMI receiverassumes that the measurement setup and measur-ing receiver are compliant with the applicablestandard.

1. Disconnect the input to the receiver. Power upthe EMI receiver.

2. Set up the correct frequency range by pressing[SETUP], <150 kHz - 30 MHz>. The 8542E or8546A automatically selects the correct CISPRbandwidth.

3. Based on the type of equipment and the regula-tory agency requirements, select the limit lineon the EMI receiver. Selecting and loading limitlines is accomplished as follows:

Press [SETUP], <More>, <Limit Lines>,<RECALL LIMITS>.

ANSI C63.4 conducted emissionstest layout

Keyboard (flush withfront of table top)

1 meter

10 cm

Mouse flush withback of keyboard

Monitor

EUTPeripheral 2Peripheral 1 Monitor

cable

LISNLISN40 cm

TerminatedI/O

Peripheral powercords

ACMains

ACMains

Rear of EUT andperipherals flush withrear of table top

Vertical conductingsurface (for conducted only)

I/O cables draped andbundled if necessary

(CISPR 22 describes layout for EN's)(top view)

1.5 meters

10cm

10cm

ANSI C63.4 conducted emissionstest layout for desktop equipment

0.8 m

Keyboard

Non-conducting table

PeripheralComputer

Monitor

Excess length of all power cordsto floor outlets is draped on floor

Metal floor (or ground plane) surfacedwith 0.3 cm of insulating material

LISNJunction box

Shielded powercable to line filter

LISN and junction boxes bonded to ground plane

All peripherals fed from floor outlets;monitor connected to outlet on computer.

(side view)

(CISPR 22 describes layout for ENs)

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Scroll down and highlight the required limit line(for example, EN022_BC is the conducted limit forclass B products for EN55022). Press <LOADFILE>. (See Figure 4). The EN022_BC containsboth the EN55022 quasi-peak and average limits.

Figure 4: Loading limit lines for an EN55022 conducted test

4. Next, correct the LISN by pressing the followingkeys:

[SETUP], <More>, <Correctn factors>, <AntennaFactors>, <RECALL ANTENNA>.

Scroll down to LISN or LISN10A, depending onthe LISN you are using. These files can be editedfor your custom use.

Press <LOAD FILE> (see Figure 5).

Figure 5: Loading correction factors for a LISN

After loading the LISN correction factors and limitlines, your display should look like Figure 6:

Figure 6: Display corrected for a LISN and limit lines on(no input connected to the receiver). The top limit is thequasi-peak limit and the bottom limit is the average limit.

4.3 Performing conducted emissions measurementsAt this point the EMI receiver is set up with all thecorrect parameters, including bandwidth, frequen-cy range, LISN compensation and limit line. Thereis one more thing to consider before starting con-ducted measurements, which is the effect of theambient environment on the results. The powercable between the LISN and the EUT can act as anantenna, which can cause false EUT responses onthe display. To test that this phenomenon is notoccurring, switch the EUT off and check the dis-play to insure that the noise floor is at least 6 dBbelow the limit line. (See Figure 7).

Figure 7: A conducted test in an ambient environment

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Switch the power to the EUT on and observe thedisplay. If there are no signals above the limit line,then your job is done and your product passes theconducted emissions limit. Data and signals closeto the limit may need to be collected for yourreport. Remember that line and neutral must betested. If there are signals above the limit, closeranalysis is needed.

Figure 8: Conducted failure

Conducted emissions usually occur in the lowerend of the band. One of the ways to take a closerlook at the lower end of the band is to switch to logfrequency sweep. Log sweep expands the lowerdecades.

Press [FREQUENCY], <SWEEP LOG>.

In Figure 9, the display is in a log frequency for-mat. Since log frequency sweep expands the lowerdecades, the signals at the lower frequencies aremore clearly shown than in the linear frequencymode.

Figure 9: Log sweep for conducted test

The next step is to perform a quasi-peak measure-ment on signals above the limit line. One method isto use the “measure at mark” function.

Before measuring, make sure you have enabled thecorrect detectors. Press [SETUP], <More>, <Inst Setup>, <Measure Detector>.

Press <Measure Detector> until the correct detec-tors are underlined; i.e., peak (PK), quasi-peak(QP) and average (AVG).

To measure the peak, quasi-peak and average levelof a signal, perform the following:

1. Press [CTRL] in the Windows section then use<ZONE CENTER> and <ZONE SPAN> to zoom inon the signals of interest in the active trace.(See Figure 7).

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Figure 10: “Windows” function, zooming in on signals

2. Press [TEST].

3. Use the knob or the up/down keys to place themarker on a signal of interest.

4. Press <MEASURE AT MKR>. After the measure-ment is completed, the signal frequency andamplitude will appear in the box above the dis-play.

5. Press <ADD TO LIST> to add your signal to thereceiver internal signal list.

Repeat the measurement procedure until all thesignals above the limit line have been measured.

The Agilent 8542E and 8546A can automaticallymeasure all signals above the limit or margin withthe “automeasure” function. Press [TEST], <More>,<More>, <AUTOMEASURE>. These signals will bestored in the signal list.

At this point, all the measured signal values are inthe internal list of the EMI receiver. To view thelist and determine which signal’s quasi-peak levelsare above the limit:

Press [TEST],<More>, <SIGNAL LIST ON>.

Press <VIEW ∆ > until QP ∆ limit 1 is shown. (SeeFigure 11).

Figure 11: Signal list

The product passes its test if:

no measured quasi-peak values are above thequasi-peak limit, and no measured average val-ues are above the average limit,

or

no measured quasi-peak values are above theaverage limit.

Remember that all lines (i.e. line and neutral) mustbe tested.

If some of the values are above the quasi-peak levelusing the quasi-peak detector and also above theaverage limit with the average detector, then sometroubleshooting and redesign is required.

5.0 Preparing for radiated emissions measure-mentsPerforming radiated emissions measurements isnot as straight-forward as performing conductedEMI measurements. There is the added complexityof the open air ambient environment, which caninterfere with the emissions from the device undertest. Fortunately, there are methods to differenti-ate between signals in the ambient environment(for example, TV, FM and cellular radio).

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5.1 Open site requirementsEUTs are measured in an open area test site(OATS). ANSI C63.4 and CISPR 16 specify therequirements for an OATS, including:

• Preferred measurement distances of 3, 10 and30 meters.

• Antenna positioning at 1 to 4 meter heights.• An area called the “CISPR ellipse” of major

diameter 2X and minor diameter √3 • X, whereX is the measurement distance. The ellipse mustbe free of any reflecting objects.

• A metal ground plane for the measurement area.

Figure 12: The CISPR ellipse

• The OATS must pass a “normalized site attenua-tion” test, or NSA. The NSA is a test that deter-mines what value a wave from a transmittingantenna (the EUT) is attenuated by the receivingantenna located on the antenna tower, refer-enced to a signal directly transmitted (viacable). Note that what is received at the receiv-ing antenna is a combination of direct wavesand reflected waves. The wave attenuation ofthe OATS must fall within a specified accuracyband. The test is performed at a distance wherethe compliance tests will be performed.

Figure 13: NSA procedure schematic, horizontal polarization

For complete details on OATS requirements, seeCISPR 16 and ANSI C63.4., and ANSI C63.7. ANSIC63.7 describes OATS construction.

Note: 10 meter anechoic chambers and GTEM cellscan also be used for radiated compliance meas-urements.

5.2 Radiated emissions test setupNote: The following sequence of steps for making a compliant measurement with the analyzerassumes that the measurement setup is compli-ant with the applicable standard.

1. Arrange the antenna, EUT and EMI receiver asshown in Figure 14. Separate the antenna andthe EUT by 3 meters (10 meters if the regulationcalls it out). CISPR and ANSI require your EUTto be in worst case mode of operation (i.e.attached cables, monitor, scrolling Hs across themonitor, etc.)

Figure 14: Radiated test setup

CISPR radiated EMI test setup

Equipmentunder test

Antenna

EMI

receiver

Ground plane

1-4 meters aboveground plane

Table is 80 cm high,non-conductive

360°8546A8546A

EMI RECEIVEREMI RECEIVER

DEMODDEMOD

EMCEMC

WINDOWSWINDOWS

STATE

EMC FUNCTION

MARKERMARKER CONTROL

DATA

INPUT 2INPUT 1INPUT 1

TGTG

OUTPUTOUTPUT

TGTG 300 MHz300 MHz ALC PROBE

POWER

TGTG 300 MHz300 MHz ALC

OVERLOAD BYPASS

RF FILTERRF FILTERSECTIONSECTION

Site attenuation test(Horizontal polarization shown)(ANSI C63.4, 1992)

1 m*

Signalgenerator

EMIreceiver

Ground plane

Maximumreceived

signal

4 meters

1 meter

Broadbandantenna

R = 3, 10, or 30 meters

Signal source ofknown amplitude

*(1.5 m for vertical)

Broadbandantenna

Major diameter = 2X

Antenna EUTX

Minor diameter = 3 • X

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2. Use Table 1 (page 4) to determine the regulationthat your product must be tested to.

3. Set up the EMI receiver for the correct span,antenna correction factors, and limit line with amargin. In this case, we are testing to the FCCpart 15, class B 3 meter limit. Load in theappropriate limit line using the following steps:

Press [SETUP], <More>, <Limit Lines>, and<RECALL LIMIT>.

Scroll down to the radiated emissions limitdetermined in Table 1 (i.e., FCC15B3M).

Figure 15: Loading FCC 3-meter class B limit

4. Press <LOAD FILE>.

5. Load the appropriate antenna correction fac-tors. The Agilent 8542E/8546A series have twopreset radiated emissions test bands, 30 MHz to300 MHz and 300 MHz to 1 GHz. The 30 MHz to300 MHz band uses a biconical antenna and the300 MHz to 1 GHz band uses a log periodicantenna. There is also a broadband antenna(11966P), which covers 30 MHz to 1 GHz.

Press [SETUP], <More>, <Correctn Factor>,<Antenna Factors>, <RECALL ANTENNA>.

Scroll down to the antenna you wish to use withthe knob or the up/down arrows.

Figure 16: Loading correction factors for a biconicalantenna

Press <LOAD FILE>.

Typical antenna factors are now loaded into theEMI receiver. The display is now corrected for theloss of the antenna and the level is measured indBµV/m, which is a field strength measurement.(See Appendix B for more information on fieldstrength.) So far, you have arranged the equipmentwith the EUT 3 meters from the antenna, chosenthe appropriate limit line and corrected the displayfor antenna loss.

5.3 Measuring radiated emissionsThe next step is to evaluate the radiated emissionsfrom your product. With the EUT off, sweep thefrequency range of interest. This gives you a goodidea of the ambient signal levels. The ideal situa-tion is to have all the ambient signals below thelimit line. In many cases they are not, so it’s a goodidea to measure them and place the results in theinternal list of the EMI receiver.

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Figure 17: An ambient environment for radiated emis-sions. Ambients can often be above your limit line.

5.4 Ambient signal measurementsThe process for measuring the ambient signals isas follows:

1. Perform a maximum hold on the signals in theband by pressing [TRACE], <MAX HOLD A>.(This function captures most signals, includinglow PRF signals)

2. Turn on the “WINDOW” function on by pressing[CTRL] under the WINDOWS area.

3. Adjust the <ZONE SPAN> with the knob to dis-play no more than 20 signals above the limit lineon the bottom active trace.

4. Use the “automeasure” function to automaticallymeasure the signals above the limit line (abovethe margin if it was initiated). To enable a mar-gin on the limit line, perform the following:

Press [SETUP], <More>,<Limit Lines>, <Limit1>, <Margin 1 ON>, then enter your margin,which typically is 6 dB. Margins are useful whenconsidering the entire measurement uncertaintyof your test setup (including antennas, cables,preamplifiers and the receiver.)

Press [TEST], <More>, <More>, <AUTOMEA-SURE> to perform the automeasure.

At this point, the EMI receiver is performing apeak, quasi-peak and average measurement on allsignals above the limit line or margin (if thesedetectors were enabled). The signals measured arethe ambients (signals produced by other sources)with the EUT off. These signals are placed in theinternal list.

Move the zone marker to the next group of signalson the top trace using the <ZONE CENTER> func-tion and repeat the automatic measurements instep 4 above. Make sure that all the signals that areabove the limit on the broad trace are measured.Press [CTRL] under the WINDOW area to view themenu containing <ZONE CENTER>. Press <ZONECENTER> and use the knob to move the zonemarker to the next group of signals.

5.5 Placement of EUT for maximum signals (manualmeasurement process) Radiated emissions from electronic devices are notuniform. The strongest emissions may be from therear panel or front panel or slots in the shielding.To insure that you are measuring the worst caseemissions from your device, do the following:

1. With the EMI receiver adjusted to view the spanof interest, move the EUT through a 360-degreerotation in 45-degree increments.

2. At each 45-degree step, note the amplitude ofthe largest signals. With a printer connected tothe I/O port, press [COPY] to obtain a screendump at each step.

3. On each screen dump, mark the position of the EUT.

After all the screen dumps have been captured,compare them to find the position of the worst-case emissions. In some cases, you may find thatthere are worst-case emissions for different fre-quencies at different positions. For example, youmay find worst-case for 100 MHz emissions at 90-degrees and at 270 degrees for 200 MHz. In thiscase, the emissions tests must be performed atboth positions. If you are not sure whether the sig-nal you are looking at is an ambient or EUT signal,switch the EUT off. An ambient signal will notchange. Worst case emissions must be found forboth horizontal and vertical polarizations.

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5.6 Ambient plus EUT measurementsWith the EUT turned on and oriented to the worstcase position, perform automated tests again asfollows:

1. Press [NEXT] under [WINDOW]. This activatesthe upper trace to capture the additional emis-sions from the EUT. Press [NEXT] again to acti-vate the lower window.

2. Adjust the <ZONE SPAN> with the knob to dis-play no more than 20 signals above the limit lineon the bottom active trace. This gives the bestfrequency accuracy.

3. Use the “automeasure” function to automaticallymeasure the signals above the limit line (orabove the margin if it was initiated): Press[TEST], <More>, <More>, <AUTOMEASURE>.

To capture the signals over the rest of the band,repeat the signal measurement process (5.5) tocapture all the signals above the limit. At thispoint, the EMI receiver is performing a peak,quasi-peak and average on all signals above thelimit line or margin within the zone span area. Ifnecessary, move the zone span to the next group ofsignals above the limit or margin and performanother automeasure. The signals measured arethe ambients plus the EUT signals. These signalsare also placed in the internal list. Now that youhave the ambient signals from the first test and theambient signals plus the EUT signals from the sec-ond group of tests you can perform a sort on thelist, looking for duplicates (the ambient signals). Toremove the ambient signals, perform the following:

Press [TEST], <More>, <EDIT LIST>, <SignalMarking>, <Selectv Mark>, <MARK ALL DUPLI-CAT>, and <DELETE MARKED>.

Figure 18: Marking and deleting ambients from your list

At this point, most of the ambient signals havebeen deleted from your list. Some ambients mayhave been present for one of the automatic meas-urements but not for the other measurement. Itwould not have duplicate signals and would not bedeleted. The signals in the list are the peak, quasi-peak and average values of the EUT emissions andremaining ambient signals.

Next, find signals that are above the limit. To dothis, sort the list by quasi-peak values, with thehighest levels at the top of the list:

Press [TEST], <More>, <EDIT LIST>, <Sort Signals>,<SORT BY QP AMP>.

Next, switch on the column that indicates the valueof the quasi-peak measurement versus the limitline.

Press [TEST], <More>, <SIG LIST ON>

Press <VIEW ∆> until VIEW QP ∆ LIM 1 is indicat-ed at the top of the right column (see Figure 19).

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Figure 19: Final EUT signal list

5.7 Evaluating measurement resultsIf all the values in the right hand column are nega-tive, then the product emissions are below thelimit and your product passes the radiated emis-sions requirements. If some of the values are posi-tive, then the quasi-peak measurements are abovethe QP limit and the product fails the radiatedemissions measurements. To be sure that a signalis not ambient, it should be remeasured and thedemodulation function used to listen to the signal.AM/FM demodulation is a good tool for determin-ing whether or not a signal is an ambient.

To listen to a signal, do the following:

Press [TEST], <More>, <SIG LIST ON>.

With the signal list on, highlight the signal of inter-est with the up/down keys.

Press [SELECT] in the DEMOD section.

Press <DEMOD ON>, <FM>.

Adjust the volume to listen to the signal. If the sig-nal is a local AM, FM, TV or cellular phone trans-mission, the demodulation function will enable theoperator to hear the audio part of the transmissionby dwelling at the marker for a specified length oftime (usually 500 msec).

If there is any doubt about the signal being anambient or an EUT signal, remove the power to theEUT and observe the signal. If the signal remains,it is an ambient.

Note: It may not be convenient to remove thepower from the EUT. In this case using the demod-ulation function may be the preferred method ofidentifying ambients.

If you have determined that a signal is an ambient,then you need to delete the signal.

Press [TEST], <More>, <EDIT LIST>, <Delete Signals>,highlight the ambient signal to be deleted and press<DELETE MARKED>.

After the ambient signals have been deleted fromthe list, a report can be developed.

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6.0 Report developmentThe end result of the above testing is a report. The report is used by the design engineer to cor-rect any problems that are found during the testprocess. You can assemble a report using the [OUTPUT] functions. The report can include a listof signals, a graphical representation of the signalsand up to two pages of text, which can be generat-ed using a common PC keyboard that connects tothe rear of the EMI receiver.

6.1 Using the Agilent 85878A EMI report generator softwareThe 85878A report generator software comes witheach 8546A or 8542E EMI receiver purchase. The85878A can be used to capture data from yourreceiver and automatically generate reports.

Figure 20: Capture the data you want with a few mouseclicks using the Agilent 85878A.

The 85878A uses object linking and embedding(OLE) technology, so you can easily drag and dropyour captured data in Microsoft Word®. Each datasession you perform is stored in a database forsearch and retrieval.

Figure 21: Data icons can be dragged and dropped toMicrosoft Word.

Using Microsoft Word and macros, you can auto-matically generate large reports. Your data iconsare “bookmarked” and automatically inserted intoyour report.

Figure 22: Custom report templates allow fast generationof reports to compliance authorities and for engineeringarchives.

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7.0 Using software to improve radiated EMI testthroughputSoftware packages that automatically control themovements of towers and turntables, capture emis-sions and find worst-case emissions are available.In addition to generating compatible reports, the85876B commercial radiated EMI software alsoperforms these functions.

For example, the 85876B has an icon set that canbe used to set up your equipment path and auto-matically import your correction factors.

Figure 24: The 85876B can set up your equipment andimport correction factors to correct for your measurementpath.

Predefined, editable test procedures enable you toautomate your test process.

Figure 25: Test procedures and control

The software enables you to control your receiverand add additional signals to your signal list with amarker “add to active list” function.

Figure 26: Software receiver control

Other signal maximization and control tools assistyou in finding your worst case emissions. The soft-ware enhances repeatability, and improvesthroughput.

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Figure 27: Tower control panel

Below is a polar plot and a height/azimuth plot ofa measured signal. The near-omnidirectional radia-tion pattern of the signal could signify that it is anambient.

Figure 28: Maximization and graphical tools assist you inperforming your final measurement.

The 85876B allows you to save files as *.rtf (richtext files) for easy import into popular word pro-cessing programs. Graphics can be saved as *.wmf(Windows Metafile) for quick pasting into manyWindows-based applications.

Figure 29: Agilent 85876B reporting capabilities

18

Line impedance stabilization networksA1.0 Purpose of a LISNA line impedance stabilization network servesthree purposes:

1. The LISN isolates the power mains from theequipment under test. The power supplied tothe EUT must be as clean as possible. Any noiseon the line will be coupled to the EMC analyzerand interpreted as noise generated by the EUT.

2. The LISN isolates any noise generated by theEUT from being coupled to the power mains.Excess noise on the power mains can causeinterference with the proper operation of otherdevices on the line.

3. The signals generated by the EUT are coupled tothe EMC analyzer using a high pass filter whichis part of the LISN. Signals which are in thepass band of the high pass filter see a 50 Ω loadwhich is the input to the EMC analyzer.

A1.1 LISN operationThe diagram in Figure A-1 below shows the circuitfor one side of the line relative to earth ground.

Figure A-1. Typical LISN circuit diagram

The 1 µF capacitor in combination with the 50 µHinductor is the filter that isolates the mains fromthe EUT. The 50 µH inductor isolates the noise gen-erated by the EUT from the mains. The 0.1 µF

couples the noise generated by the EUT to the EMC analyzer or receiver. At frequencies above 150 kHz, the EUT signals are presented with a 50 Ω impedance.

The chart in Figure A-1 represents the impedanceof the EUT port versus frequency.

A1.2 Types of LISNs

Figure A-2. Three different types of LISNs

The most common type of LISN is the V-LISN. Itmeasures the asymmetric voltage between line andground. This is done for both the hot and the neu-tral lines or for a three-phase circuit in a “Y” con-figuration, between each line and ground. Thereare some other specialized types of LISNs. A deltaLISN measures the line to line or symmetric emis-sions voltage. The T-LISN, sometimes used fortelecommunications equipment, measures theasymmetrical voltage, which is the potential differ-ence between the midpoint potential between twolines and ground.

A2.0 Transient limiter operationThe purpose of the limiter is to protect the input ofthe EMC analyzer from large transients when con-nected to a LISN. Switching EUT power on or offcan cause large spikes generated in the LISN.

The Agilent 11947A transient limiter incorporatesa limiter, high pass filter, and an attenuator. It canwithstand 10 kW for 10 µsec and has a frequencyrange of 9 kHz to 200 MHz. The high pass filterreduces the line frequencies coupled to the EMCanalyzer.

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 NV unsym

metric

1

V2 unsy

mmetric

1/2 V symmetric 1/2 V symmetric

V unsymm

etric

1

V unsymmetric2V asymmetric

Line impedance stabilization network (LISN)

605040302010

.01 .1 1 10 100

impedance(ohms)

frequency (MHz)

0.1 µF

1000W

From powersource

To EUT

ToReceiver or EMC Analyzer

(50 Ω)

50 µH

1 µF

Appendix A

19

Antenna factorsB1.0 Field strength unitsRadiated EMI emissions measurements measurethe electric field. The field strength is calibrated indBµV/m. Field strength in dBµV/m is derived fromthe following:

Pt = total power radiated from an isotropic radia-tor

PD = the power density at a distance r from theisotropic radiator (far field)

PD = Pt /4πr2 R = 120πΩ

PD = E2/R

E2/R = Pt /4πr2

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

Far field* is considered to be >λ/2π

* Far field is the minimum distance from a radiator where the field becomes a planar wave.

B1.1 Antenna factorsThe definition of antenna factors is the ratio of theelectric field in volts per meter present at theplane of the antenna versus the voltage out of theantenna connector. Note: Antenna factors are notthe same as antenna gain.

Figure B-1. Typical antenna factor shapes

B1.2 Types of antennas used for commercial radiatedmeasurements

Figure B-2. Antennas used in EMI emissions measure-ments

There are three types of antennas used for com-mercial radiated emissions measurements.

Biconical antenna: 30 MHz to 300 MHz

Log periodic antenna: 200 MHz to 1 GHz (The biconical and log peri-odic overlap frequency)

Broadband antenna: 30 MHz to 1 GHz (Larger format than the bicon-ical or log periodic antennas)

Blah

Log Periodic Antenna

Biconical Antenna

Broadband Antenna

(30 - 300 MHz)

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

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 Field Strength (V/m) V = Voltage Output from Antenna (V)

Log Units: AF(dB/m) = E(dBµV/m) - V(dBµV) E(dBµV/m) = V(dBµV) + AF(dB/m)

AF = EinV out

30

Appendix B

20

Basic electrical relationshipsThe decibel is used extensively in electromagneticmeasurements. It is the log of the ratio of twoamplitudes. The amplitudes are in power, voltage,amps, electric field units, and magnetic field units.

decibel = dB = 10 log (P2/P1)

Data is sometimes expressed in volts or fieldstrength units.

In this case, replace P with V2/R.

If the impedances are equal, the equation becomes:

dB = 20 log(V2/V1)

A unit of measure used in EMI measurements isdBµV or dBµA. The relationship of dBµV and dBmis as follows:

dBmV = 107 + PdBm

This is true for an impedance of 50 Ω.

Wave length (l) is determined using the followingrelationship:

λ = 3x108 / f (Hz) or λ = 300/f (MHz)

Appendix C

21

Detectors used in EMI measurements-peak,quasi-peak, and averageD1.0 Peak detectorInitial EMI measurements are made using the peakdetector.

This mode is much faster than quasi-peak, or aver-age modes of detection. Signals are normally dis-played on spectrum analyzers or EMC analyzers inpeak mode. Since signals measured in peak detec-tion mode always have amplitude values equal toor higher than quasi-peak or average detectionmodes, it is a very easy process to take a sweepand compare the results to a limit line. If all sig-nals fall below the limit, then the product passesand no further testing is needed.

D1.2 Peak detector operationThe EMC analyzer has an envelope or peak detec-tor in the IF chain which has a time constant suchthat the voltage at the detector output follows thepeak value of the IF signal at all times. In otherwords, the detector can follow the fastest possiblechanges in the envelope of the IF signal, but notthe instantaneous value of the IF sine wave (seeFigure D-1).

Figure D-1. Peak detector diagram

D2.0 Quasi-peak detectorMost radiated and conducted limits are based onquasi-peak detection mode. Quasi-peak detectorsweigh signals according to their repetition rate,which is a way of measuring their annoyance fac-tor. As the repetition rate increases, the quasi-peakdetector does not have time to discharge as muchresulting in a higher voltage output. (See Figure D-2 below.) For continuous wave (CW) signals thepeak and the quasi-peak are the same.

Since the quasi-peak detector always gives a read-ing less than or equal to peak detection, why notuse quasi-peak detection all the time? Won’t thatmake it easier to pass EMI tests? Its true that youcan pass the tests easier, however, quasi-peakmeasurements are much slower by 2 or 3 orders ofmagnitude compared to using the peak detector.

Figure D-2. Quasi-peak detector response diagram

D2.1 Quasi-peak detector operationThe quasi-peak detector has a charge rate muchfaster than the discharge rate; therefore the higherthe repetition rate of the signal the higher the out-put of the quasi-peak detector. The quasi-peakdetector also responds to different amplitude sig-nals in a linear fashion. High amplitude low repeti-tion rate signals could produce the same output aslow amplitude high repetition rate signals.

Quasi-peak detector output varies with impulse rate

t

Peak responseQuasi-peak

detector readingQuasi-peak

detector response

t

Test Limit

Test Limit

Output of the envelope detector follows the peaks of the IF signal

Appendix D

22

D3.0 Average detectorThe average detector is required for some conduct-ed emissions tests in conjunction with using thequasi-peak detector. Also, radiated emissionsmeasurements above 1 GHz are performed usingaverage detection. The average detector output isalways less than or equal to peak detection.

D3.1 Average detector operationAverage detection is similar in many respects topeak detection. Figure D-3 below shows a signalthat has just passed through the IF and is about tobe detected. The output of the envelope detector isthe modulation envelope. Peak detection occurswhen the post detection bandwidth is wider thanthe resolution bandwidth. For average detection totake place, the peak detected signal must passthrough a filter whose bandwidth is much lessthan the resolution bandwidth. The filter averagesthe higher frequency components, such as noise, atthe output of the envelope detector.

Figure D-3. Average detection response diagram

Average Detection

A

t

Envelope Detector

Filters

Average Detector

23

EMC regulatory agenciesThe following is a listing of address and phonenumbers for obtaining EMC regulation informa-tion.

IECCISPRSales Department of the Central Office of the IECPO Box 1313, Rue de Verembe1121 Geneva 20, Switzerland

CCIRITU, General Secretariat, Sales ServicePlace de Nation1211 Geneva, Switzerland

AustraliaAustralia Electromechanical CommitteeStandards Association of AustraliaPO Box 458North Sydney N.S.W. 2060Telephone: +61 2 963 41 11Fax: +61 2 963 3896

BelgiumComite Electrotechnique Belge3 Galerie Ravenstein, Boite 11B-1000 BruxellesTelephone: +32 2 512 00 28Fax: +32 2 511 29 38

CanadaStandards Council of CanadaStandards Sales Division350 Sparks Street, Suite 1200Ottawa, Ontario K1P 6N7Telephone: 613 238 3222Fax: 613 995 4564

Canadians Standards Association (CSA)178 Rexdale BoulevardRexdale (Toronto), Ontario MSW 1R3Telephone: 416 747 4044Fax: 416 747 2475

DenmarkDansk Elektroteknisk Komite Strandgade 36 stDK-1401 Kobenhavn KTelephone: +45 31 57 50 50Fax: +45 31 57 63 50

FranceComite Electrotechnique FrancaisUTE CEdex 64F-92052 Paris la DefenseTelephone: +33 1 47 68 50 20Fax: +33 1 47 89 47 75

GermanyVDE CERLAG GmbHAustieferungsstelleMerianstrasse 29D-6050 OFFENBACH a.M.Telephone: + 49 69 8306-1Fax: + 49 69 83 10 81

IndiaBureau of Indian Standards, Sales DepartmentManak Bhavan9 Bahadur Shah Zafar Marg.New Delhi 110002Telephone: + 91 11 331 01 31Fax: + 91 11 331 40 62

ItalyCometato Eletrotecnico ItalianoViale Monza 2591-20126 Milano MITelephone: + 39 2 25 77 31Fax: + 39 2 25 773 222

JapanJapanese Standards Association1-24 Akasaka 4Minato-KuTokyo 107Telephone: + 81 3 583 8001Fax: + 81 3 580 14 18

NetherlandsNederlands Normalisatie-InstituutAfd. Verdoop en InformatieKalfjeslaan 2, PO Box 50592600 GB DelftNLTelephone: + 31 15 69 03 90Fax: + 31 15 69 01 90

NorwayNorsk Elektroteknisk KomiteHarbizalleen 2APostboks 280 SkoyenN-0212 Oslo 2Telephone: + 47 2 52 69 50Fax: + 47 2 52 69 61

Appendix E

24

South AfricaSouth African Bureau of StandardsElectronic Engineering DepartmentPrivate Bag X191Pretoria0001 Republic of South Africa

SpainComite Nacional Espanol de la CEIFrancisco Gervas 3E-28020 MadridTelephone: + 34 1 270 44 00Fax: + 34 1 270 28 55

SwedenSvenka Elecktriska KommissionenPO Box 1284S-164 28 Kista-StockholmTelephone: + 48 8 750 78 20Fax: + 46 8 751 84 70

SwitzerlandSwiss Electromechanical CommitteeSwiss Electromechanical AssociationSeefeldstrasse 301CH-8008 ZurichTelephone: + 41 1 384 91 11Fax: + 41 1 55 14 26

United KingdomBritish Standards InstitutionBSI Sales DepartmentLinford WoodMilton Keynes MK14 GLETelephone: +44 908 22 00 22Fax: +44 908 32 08 56

British Defence StandardsDEF STANMinistry of DefenceNorthumberland HouseNorthumberland AveLondon WC2N 5 BPTelephone: + 01 218 9000

United States of AmericaAmerica National Standards Institute Inc.Sales Dept.1430 Broadway New York, NY 10018Telephone: 212 642 4900Fax: 212 302 1286

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

FCC Equipment Authorization Branch7435 Oakland Mills RoadMS 1300-B2Columbia, MD 21046Telephone: 301 725 1585

25

Ambient level1. The values of radiated and conducted signal and

noise existing at a specified test location andtime when the test sample is not activated.

2. Those levels of radiated and conducted signaland noise existing at a specified test locationand time when the test sample is inoperative.Atmospherics, interference from other sources,and circuit noise, or other interference generat-ed within the measuring set compose the ambi-ent level.

Amplitude modulation1. In a signal transmission system, the process, or

the result of the process, where the amplitude ofone electrical quantity is varied in accordancewith some selected characteristic of a secondquantity, which need not be electrical in nature.

2. The process by which the amplitude of a carrierwave is varied following a specified law.

Anechoic chamber1. A shielded room which is lined with radio

absorbing material to reduce reflections from allinternal surfaces. Fully lined anechoic chambershave such material on all internal surfaces: wallceiling and floor. Its also called a “fully anechoicchamber.” A semi-anechoic chamber is a shield-ed room which has absorbing material on allsurfaces except the floor.

Antenna (aerial)1. A means for radiated or receiving radio waves.2. A transducer which either emits radio frequency

power into space from a signal source or inter-cepts an arriving electromagnetic field, convert-ing it into an electrical signal.

Antenna factorThe factor which, when properly applied to thevoltage at the input terminals of the measuringinstrument, yields the electric field strength involts per meter and a magnetic field strength inamperes per meter.

Antenna induced voltageThe voltage which is measured or calculated toexist across the open circuited antenna terminals.

Antenna terminal conducted interferenceAny undesired voltage or current generated withina receiver, transmitter, or their associated equip-ment appearing at the antenna terminals.

Auxiliary equipmentEquipment not under test that is neverthelessindispensable for setting up all the functions andassessing the correct performance of the EUT dur-ing its exposure to the disturbance.

BalunA balun is an antenna balancing device, whichfacilitates use of coaxial feeds with symmetricalantennae such as a dipole.

Broadband emissionBroadband is the definition for an interferenceamplitude when several spectral lines are withinthe RFI receivers specified bandwidth.

Broadband interference (measurements)A disturbance that has a spectral energy distribu-tion sufficiently brad, so that the response of themeasuring receiver in use does not vary signifi-cantly when tuned over a specified number ofreceiver bandwidths.

Conducted interferenceInterference resulting from conducted radio noiseor unwanted signals entering a transducer (receiv-er) by direct coupling.

Cross coupling The coupling of a signal from one channel, circuit,or conductor to another, where it becomes anundesired signal.

Decoupling networkA decoupling network is an electrical circuit forpreventing test-signals which are applied to theEUT from affecting other devices, equipment, orsystems that are not under test. IEC 801-6 statesthat the coupling and decoupling network systemscan be integrated in one box or they can be in sep-arate networks.

Glossary of acronyms and definitions

26

Dipole1. An antenna consisting of a straight conductor

usually not more than a half-wavelength long,divided at its electrical center for connection toa transmission line.

2. Any one of a class of antennas producing a radi-ation pattern approximating that of an elemen-tary electric dipole.

Electromagnetic compatibility (EMC)1. The capability of electronic equipment of sys-

tems to be operated within a defined margins inof safety in the intended operational environ-ment at designed levels of efficiency withoutdegradation due to interference.

2. EMC is the ability of equipment to function sat-isfactorily in its electromagnetic environmentwithout introducing intolerable disturbancesinto that environment or into other equipment.

Electromagnetic interferenceElectromagnetic interference is the impairment ofa wanted electromagnetic signal by an electromag-netic disturbance.

Electromagnetic waveThe radiant energy produced by the oscillation ofan electric charge characterized by oscillation ofthe electric and magnetic fields.

EmissionElectromagnetic energy propagated from a sourceby radiation or conduction.

Far field The region where the power flux density from anantenna approximately obeys an inverse squareslaw of the distance. For a dipole this correspondsto distances greater than l/2 where l is the wavelength of the radiation.

Ground plane1. A conducting surface of plate used as a common

reference point for circuit returns and electricor signal potentials.

2. A metal sheet or plate used as a common refer-ence point for circuit returns and electrical orsignal potentials.

Immunity1. The property of a receiver or any other equip-

ment or system enabling it to reject a radio dis-turbance.

2. The ability of electronic equipment to withstandradiated electromagnetic fields without produc-ing undesirable responses.

Intermodulation Mixing of two or more signals in a nonlinear ele-ment, producing signals at frequencies equal to thesums and differences of integral multiples of theoriginal signals.

IsotropicIsotropic means having properties of equal valuesin all directions.

MonopoleAn antenna consisting of a straight conductor, usually not more than one-quarter wave lengthlong, mounted immediately above, and normal to, a ground plane. It is connected to a transmissionsline at its base and behaves, with its image, like adipole.

Narrowband emissionThat which has its principal spectral energy lyingwithin the bandpass of the measuring receiver inuse.

Open areaA site for radiated electromagnetic interferencemeasurements which is open flat terrain at a dis-tance far enough away from buildings, electriclines, fences, trees, underground cables, and pipelines so that effects due to such are negligible. Thissite should have a sufficiently low level of ambientinterference to permit testing to the required limits.

PolarizationA term used to describe the orientation of the fieldvector of a radiated field.

Radiated interferenceRadio interference resulting from radiated noise ofunwanted signals. Compare radio frequency inter-ference below.

27

RadiationThe emission of energy in the form of electromag-netic waves.

Radio frequency interferenceRFI is the high frequency interference with radioreception. This occurs when undesired electromag-netic oscillations find entrance to the high frequen-cy input of a receiver or antenna system.

RFI sourcesSources are equipment and systems as well astheir components which can cause RFI.

Shielded enclosureA screened or solid metal housing designedexpressly for the purpose of isolating the internalfrom the external electromagnetic environment.The purpose is to prevent outside ambient electro-magnetic fields from causing performance degrada-tion and to prevent emissions from causing inter-ference to outside activities.

StriplineParallel plate transmission line to generate an elec-tromagnetic field for testing purposes.

SusceptibilitySusceptibility is the characteristic of electronicequipment that permits undesirable responseswhen subjected to electromagnetic energy.

By internet, phone, or fax, get assistance with all your test and measurement needs.

Online Assistancewww.agilent.com/find/assistPhone or FaxUnited States:(tel) 1 800 452 4844

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Product specifications and descriptions in this document subject to change without notice.

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