Appendix A: Line Impedance Stabilization Networks (LISN) - SGLabs

Sistema professionale per misurazioni EMCTutto ciò che necessita per le misurazioni di emissioniradiate e condotteSistema praticamente nuovo con meno di 10 ore difunzionamento, valore di listino 35.000€Accessori inclusi nell’offerta:- E7402A EMC standard analyzer, 30 Hz to 3.0 GHz- 11945A Close field probe set- 11968C Antenna tripod- 11966L 10m type N cable- E7415A EMI measurement software- 11947A Transient Limiter with high-pass filter- 11940A Close field probe 30 MHZ 1 GHz- 11941A Close field probe 9 kHz 30 MHZ- 11967D Line Impedance Stabilization Network, NEMA- 11956A BiConiLog broadband antenna, 26 MHz to 2 GHz- 11955A Biconical Antenna, 30 to 300 MHz

- 11967D-001 Line Impedance Stabilization Network, SCHUKO- KIT FERRISHIELD INC. (EK28B0032)Seguono alcune foto del sistema

SgLabsStrada S. Giovanni Torre 3Q06132 Pila - PerugiaItalyTel. +390755149360Tel. +390757827575Mob. +393470903531Fax: +390757823560Mail: m.sev@sglabs.itWebsite: www.sglabs.itNegozio Ebay: SgLabs

Agilent AN 1328Making PrecomplianceConducted and RadiatedEmissions Measurementswith EMC AnalyzersApplication NoteAgilent E7400A Series

1.0 Introduction to Precompliance MeasurementsThe concept of getting a product to market on timeand within budget is nothing new. However, companieshave added some new steps to the introductionprocess to achieve those goals. One of thosesteps in the process is the addition of an EMC(electro-magnetic compatibility) strategy. Manufacturershave realized that in order to sell their electronicproducts on the commercial market, theymust pass EMC requirements. Waiting until theend of the development cycle to find out whetheror not a product passes regulatory agency requirementscan be an expensive gamble. Failing to passcan result in costly redesign. Because of this, developersare concerned about the EMC performanceof a new product from design investigation throughpreproduction units. Figure 1 below shows a typicalproduct development cycle.Many manufacturers use EMI precompliancemeasurement systems to perform conducted andradiated EMI emissions tests prior to sendingthe product to a test facility for full compliancetesting. Conducted emissions testing focuseson signals, present on the AC mains, that are generatedby the EUT (equipment under test). Thetest range for these measurements is from 9 kHzto 30 MHz, depending on the regulation.Radiated emissions testing looks for signals broadcastedfrom the EUT through space. The frequencyrange for these measurements is between 30 MHzand 1 GHz, depending on the regulation. Testingto higher frequencies may be required dependingon the device and the internal clock frequency.This preliminary testing is called precompliancetesting. Figure 2 illustrates the relationshipbetween radiated emissions, radiated immunity,conducted emissions, and conducted immunity.Radiated immunity is the ability of a device orproduct to withstand radiated electromagneticfields. Conducted immunity is the ability of adevice or product to withstand electrical disturbanceson power or data lines. In order to experiencean electromagnetic compatibility problem,such as when an electric drill interferes with TVreception, there must be a generator or source, acoupling path, and a receptor. An EMC problemcan be eliminated by removing one of the components:generator, coupling path, or receptor.Until recently, most of the concentration has beento reduce the generator emissions to remove anEMC problem (that is, reduce the emissions fromthe source to an acceptable level).InitialinvestigationYesviableDesignbreadboardProduct development cycleLabprototypeProductionprototypeProductionunitpass pass pass passYesNoNoNoNoNoR E D E S I G N ProductionFigure 1. A typical product development cycle3

With the advent of the European requirements,there is additional focus on product immunity. Thelevel of electrical field that a receptor can withstandbefore failure is known as the product immunity.The term immunity and susceptibility areused interchangeably. Immunity testing will notbe covered in this document.EmissionConductedRadiatedImmunity = Susceptibility1.1 Precompliance measurements versus fullcompliance measurementsFull compliance measurements require the useof a receiver that meets the requirements set forthin the CISPR 1 part 16 document, a qualified openarea test site, and an antenna tower and turntableto maximize the signals from the EUT. Great effortis taken to get the best accuracy and repeatability.This can be very expensive. The photograph belowshows a full compliance test facility.Precompliance measurements are intended to givean approximation of the EMI performance of theEUT. The cost of performing precompliance testsis a fraction of full compliance measurements. Themore attention to detail, such as a good groundplane and minimizing the number of reflectiveobjects in the measurement area, the better theaccuracy of the measurements.Figure 2. Electromagnetic compatibility between products41. Comite International Special des Perturbations Radioelectriques

MONITORPOWER OUTPUTCAUTIONHIGH VOLTAGEGNDHP 1941AHP 1940A2.0 EMI Precompliance SystemsThe components of a precompliance test system(the Agilent Technologies 84115EM preproductionevaluation system, for example) include an EMCanalyzer, a line impedance stabilization network(LISN), antennas, close field probes, and interconnectioncables (Figure 3). The test environment forprecompliance testing is usually less controlledthan full compliance testing, which is performedon an open area test site (OATS).EMI precompliance systemLog periodicantennaEMC analyzer(with optionalpreselectors)BiconicalantennaLISNEMIsoftwareAgilent 11947ATransientlimiterClose-field probe setDiagnosticsTripodFigure 3. Components of a preproduction evaluation system5

3.0 Precompliance Measurements ProcessThe precompliance measurement process is fairlystraightforward. However, before measurementscan be performed on a product, some preliminaryquestions must be answered.1. Where is the product to be sold (in other words,United States, Europe, Japan, etc.)?2. What is the classification of the product (thatis, information technology equipment [ITE]devices; industrial, scientific, medical [ISM]devices; automotive or communications)?3. Where is the product to be used (i.e., home,commercial, light industry, or heavy industry)?With the answers to the above questions, you canthen determine to which requirements your productmust be tested. For example, if you have determinedthat your product is an ITE device and youare going to sell it in the United States, then youneed to test the product to the FCC part 15 regulation.See Tables 1a and 1b to choose the requirementfor your product. When in doubt, call theappropriate agency for final conformation with theapplicable requirement. (A list of phone numbersis included in Appendix E.)European norms detail descriptionEN55011 (CISPR 11)Industrial, Scientific, and Medical ProductsClass A: Used in establishments other than domesticareas.Class B: Suitable for use in domestic establishments.Group 1: Laboratory, medical, and scientific equipment.(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, medicalapparatus, spark erosion equipment, and spotwelders. (For example: metal melting, billet heating,component heating, soldering and brazing, woodgluing, plastic welding, food processing, food thawing,paper drying, microwave therapy equipment.)Table 1a. Comparison of regulatory agency requirementsEmissions regulations (summary)FCCCISPREN'sDescription18 11EN 55011Industrial, scientific and medical––12––Automotive15 131415EN 55013EN 55014EN 55015Broadcast receiversHousehold appliances/toolsFluorescent lights/luminaries15 22––16EN 55022EN 50081––Information technology equipmentGeneric emissions standardsMeasurement apparatus/methods16 EN 55025Automotive component test6

EN55014 (CISPR 14)Electric motor-operated and thermal appliancesfor household and similar purposes, electric tools,and electric apparatus. Depending on the powerrating of the item being tested, use one of the limitsshown in the table on the following page.Household and similar appliances(conducted)(Disk file names)(replace with newfile names on all)Household and similar appliances (radiated)Motors < 700 W (conducted)Motors < 700 W (radiated)Motors 1000 W (radiated)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, electronicbusiness equipment, telecommunicationsequipment.)Class A ITE: Not intended for domestic use.Class B ITE: Intended for domestic use.Note: The conducted range is 150 kHz to 30 MHzand the radiated range is 30 MHz to 300 MHz.7

Table 1b. FCC requirements summaryFederal Communications CommissionEquipment TypeFCC• Broadcast receivers• Household appliances• Fluorescent lights / luminaries• Information technology / equipment (ITE)• Industrial, scientific, and medical (ISM)Part 15Class A IndustrialClass B ResidentialPart 18• Conducted measurements: 450 kHz - 30 MHz• Radiated measurements: 30 MHz - 1000 MHz, 40 GHzFederal Communications Commission EquipmentDetailed DescriptionFCC Part 15Radio frequency devices—Unintentional radiatorsFor example, TV broadcast receivers, FM broadcastreceivers, CB receivers, scanning receivers, TVinterface devices, cable system terminal devices,Class B personal computers and peripherals,Class B digital devices, Class A digital devicesand peripherals, and external switching powersupplies.Class A digital devices: Marketed for use in acommercial, industrial, or business environment.Class B digital devices: Marketed for use in aresidential environment.8

4.0 Emissions Testing4.1 IntroductionAfter the appropriate regulations have been identified,the next step is to set up the test equipmentand perform radiated and conducted emissionstests. The first group of tests to perform is conductedemissions tests. The process we will followwill be to interconnect the equipment, load in theappropriate limit line from the ROM card, correctfor the LISN and transient limiter (see AppendixA), and perform the tests.4.2 Conducted emissions measurementspreparationEmissions testing is divided into conducted emissionsand radiated emissions testing. Conductedemissions testing is the easiest to perform. Followthese steps to set up the equipment and the equipmentunder test.1. Interconnect the EMC analyzer, limiter, LISN,and EUT as shown in Figure 4 (printer isoptional).(Operation of the LISN and the limiter is coveredin Appendix A.)2. Power up the EMC analyzer.3. Set up the correct frequency range. Press[MEAS SETUP], .Note: The disk drive is in path “A.” If the path is in“C” when attempting to load from “A,” use [↓], [↑]to highlight “A.” Then press .Conducted emissions measurementsare easier than ever!Agilent E7400A series EMI analyzerSelect fromimpulse, 6 dB,or 3 dB BWwith resolutionBW of 1 MHz.Device under test11947AAgilent 11967D LISNLimiterStore measurement results to disk2000 second sweep time (max)Quasi-peak measurements over broad spansCorrect for limiter and LISNFigure 4. Conducted measurements interconnection9

4. Select and load the limit line from the disk supplied,based on the type of equipment and theregulatory agency requirements. Selecting andloading limit lines is accomplished by pressingthe following buttons on the EMC analyzer:[FILE], , , , scrolldown and highlight the required limit line(in other words, EN22BCQP, which is theconducted limits for Class B products). Press[ENTER]. (See Figures 5a and 5b.)5. Switch on limit test to indicate whether or notsignals pass the requirement. Press [Meas. Setup],, , , .Figure 5a. Partial list of regulatory limitsFigure 5b. Regulatory limits displayed10

6. Correct for the LISN. The disk contains typicalcorrection factors. To correct the display for theLISN, press the following buttons:7. Enable corrections for LISN. Press [MEASSETUP], , , ,, , .[FILE], , . Scroll downto the LISN you are using. Press [ENTER].Agilent offers two LISNs, 11967E (25 amps)and 11967D (10 amps). (See Figures 6a and 6b.)Figure 6a. List of typical transducersFigure 6b. Display corrected for LISN factors11

8. Correct the display for the Agilent 11947A transientlimiter by pressing the following buttons:[FILE], , , select 11947Aand [ENTER]. (See Figures 7a and 7b.)9. To enable the correction factors for the limiter,press [MEAS SETUP], , ,, , , .Figure 7a. List including limiterFigure 7b. Display corrected for limiter losses12

4.3 Performing conducted emissionsmeasurementsAt this point the EMC analyzer is set up withall the correct parameters, including bandwidth,frequency range, LISN and limiter compensation,and limit line. There is one more thing to considerbefore starting conducted measurements: theeffect of the ambient environment on the results.The power cable between the LISN and the EUTcan act as an antenna, which can cause false EUTresponses on the display. To test that this phenomenonis not occurring, switch the power of theEUT off and check the display to ensure that thenoise floor and ambient signals are at least 6 dBbelow the limit line (see Figure 8).If signals appear above the limit line on the display,the interconnecting power cord may need tobe shortened or a shield may be needed around thecord. Do not use a ferrite core around the powercord because the common mode signals comingfrom the EUT can also be attenuated, giving falseindications.4.4 Starting the conducted measurementsprocessTurn on the EUT power and observe the display.If no signals appear above the limit line, the productpasses the conducted emissions limit and yourjob is done. Most of the time, testers are not solucky. There are usually signals above the limitthat need closer analysis.Conducted emissions usually occur in the lowerend of the band.4.4.1 Overload testBefore starting the measurements, you should testto ensure that the EMC analyzer is not in overload.An overload condition occurs when the energylevel at the input mixer of the EMC analyzer isvery high, causing errors in amplitude measurements.To test for this condition, do the following:Press [AMPLITUDE], , ,which increases the attenuation before the inputmixer of the EMC analyzer. If the signal does notchange position on the display, then the mixer isnot overloaded. If the amplitude of the signal doesincrease, then the input is overloaded and additionalattenuation must be added.Figure 8. Noise picked up by power cord with EUT off13

4.4.2 Signal measurementsThe next step is to perform a quasi-peak measurementon signals above the limit line. One method isto use the “measure at mark” function.To measure the peak and quasi-peak level of a signal(see Appendix D), perform the following:Press [MEAS SETUP], , ,, . Press [SPAN],, ; use and to show the signals of interestin the active trace. (See Figure 9.)To measure the peak and quasi-peak level of a signalof interest, press [MEASURE] , ,then use the knob or the up/down keys to placethe marker on the signal.Press . After the measurementis completed, the signal frequency, peak,and quasi-peak amplitudes will appear in thebox above the display. Press .Repeat the measurement procedure until all thesignals above the limit line have been measured.Figure 9. Conducted emissions from EUT14

At this point, all the measured signal values are inthe internal list of the EMC analyzer. To view thelist and determine which signal’s quasi-peak levelsare above the limit, do the following:Press [MEASURE], , ,.Press then .(See Figure 10.)If there are no quasi-peak values above the limitline (positive values), then your job is done and theproduct passes conducted emissions tests.If some of the quasi-peak values are above the limitline, troubleshooting and redesign are required.4.5 Radiated emissions measurementspreparationPerforming radiated emissions measurements isnot as straightforward as performing conductedEMI measurements. There is the added complexityof the ambient environment, which could interferewith the emissions from the EUT. There are methodsto differential between ambient environmentsignals (TV, FM, and cellular radio).1. Arrange the antenna, EUT, and the EMC analyzeras shown in Figure 11. Separate the antennaand the EUT by 3 meters. (Use 10 meters if it iscalled out in the regulation. If space is limited,correct the results for the difference in distancefrom 3 to 10 meters, which is 10.45 dB.) It isimportant that the antenna not be placed in the“near field” which is 2 away from the EUT orcloser. The Agilent E7400A series has a built-inamplifier with 20 dB gain and 7 dB noise figure.For increased gain, use the Agilent 11909Aamplifier with 32 dB gain and 1.8 dB noise figure.Figure 10. List of measured signals15

Precompliance Radiated MeasurementsAgilent E7400A series EMI AnalyzerBiconicalAntennaE1799ABattery Pack(Optional)Automated measurements(No computer needed)Built-in preamplifier(No external amplifier needed)Limit Line Correction Factors(For direct data comparison)TripodDevice Under TestFigure 11. Radiated emissions test setup2. Set up the EMC analyzer for the correct span,antenna correction factors, and limit line with amargin. Load in the appropriate limit line usingthe following steps:Press [Meas Setup], .Press [FILE], , , and .Scroll down to the radiated emissions limitdetermined in Table 1 (for instance, FCC15B3).Press [ENTER].3. To load the appropriate antenna correction factor,first determine the test frequency band. TheAgilent E7400A series has two preset radiatedemissions test bands, 30 MHz to 300 MHz and200 MHz to 1 GHz. The 30 MHz to 300 MHz banduses a biconical antenna (Agilent 11955A or11966C) and the 200 MHz to 1 GHz uses a logperiodic antenna (Agilent 11966D or 11956A).There is also a broadband antenna (11966P)that covers both bands.Press [FILE], , .Scroll down to the antenna you wish to use,using the knob or the up/down arrows.Press [ENTER].16

4. After file is loaded, switch on corrections bypressing [Meas Setup], , ,, . To display the correctamplitude units, press ,.Typical antenna factors are now loaded intothe EMC analyzer. The display is now correctedfor the loss of the antenna and the level is measuredin dBuV/m, which is a field strength measurement.(See Appendix B for more informationon field strength.)4.6 Measuring radiated emissionsNow you can start evaluating the radiated emissionsyour product produces.With the EUT off, sweep the frequency range ofinterest to survey ambient environment levels. Theideal situation would be to have all the ambientsignals below the limit line. In many cases, ambientsignals will be above the limit, so you should measurethem and place the results in the internal listof the EMC analyzer.5. If an external amplifier is used between theantenna and the EMC analyzer to improve sensitivity,correction factor for the amplifier alsomust be loaded in to the analyzer. To do this,press:[FILE], , .Scroll to 11909A and press [ENTER].6. If the internal preamplifier is used, press[AMPLITUDE], , .Your display should look similar to Figure 12.Figure 12. Display with limit line and correction factors17

4.7 Ambient signal measurementsThe process for measuring the ambient signals isas follows:1. Perform a maximum hold on the signals in theband by pressing the following:[VIEW/TRACE], .(This function captures most signals, including lowPRF signals.)2. Turn “WINDOW” function on by pressing[SPAN], , .3. Adjust the and with the knob to display no more than 20 signalsabove the limit line on the bottom activetrace.4. Use the “automeasure” function to automaticallymeasure the signals above the limit line:Press [Measure], , ,.At this point, the EMC analyzer is performing peakand quasi-peak measurements on all signals abovethe limit line. The signals measured are the ambients(signals produced by other sources) with EUToff. These signals are placed in the internal list.Move the zone marker to the next group of signalson the top trace using the functionand repeat the automatic measurements inStep 4 above. Make sure that all the signals thatare above the limit on the upper broad span traceare measured. Press [SPAN], , to view the menu with . Press and use the knob to move thezone marker to the next group of signals andrepeat Step 4 above.4.8 Placement of EUT for maximum signalsRadiated emissions from electronic devices are notuniform. The strongest emissions may be from therear panel or front panel or slots in the shielding.To ensure that you are measuring the worst caseemissions from your device, do the following:1. Press [MEAS SETUP] and the frequency band ofyour antenna (for instance, fora biconical antenna).2. At each 45-degree step, note the amplitude ofthe largest signals. (A screen output to a printercan be very useful.) With a printer connected tothe IO port, press [PRINT].3. On each screen output, mark the position ofthe EUT.After all the screens have been captured, comparethem to find the position of the worst-case emissions.In some cases, you may find that there areworst-case emissions for different frequencies atdifferent positions. For example, 100 MHz may beworst-case emissions at 90 degrees and 200 MHzmay be worst-case emissions at 270 degrees. Inthis case, the emissions tests must be performedat both positions. A typical screen output is shownin Figure 13.If you are not sure whether the signal you arelooking at is an ambient or EUT signal, switch thepower off on the EUT. If the signal remains, thenit is an ambient signal. Repeat this process for theother polarization of the antenna (that is, verticalor horizontal).18

Figure 13. Radiated emissions display4.9 Ambient plus EUT measurementsWith the EUT turned on and oriented to the worstcaseposition, perform automated tests again asshown below.1. Press [NEXT WINDOW]. (This activates theupper trace to capture the additional emissionsfrom the EUT.) Press [NEXT WINDOW] againto activate the lower window.2. Adjust the with the knob to displayno 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 (abovethe margin if it was initiated).Press [MEASURE], , ,, , ,.At this point, the EMC analyzer is performing apeak and quasi-peak on all signals above the limitline or margin, which is within the zone span area.If necessary, move the zone span to the next groupof signals above the limit or margin and performanother automeasure as in Step 2 above.The signals measured are the ambients and theEUT signals. These signals are also placed inthe internal list. Now that you have the ambientsignals from the first test and the ambient signalsplus the EUT signals from the second group oftests, you can perform a sort on the list lookingfor duplicates (which will be the ambient signals).To remove the ambient signals from the measurementresults, perform the following:Press [MEASURE], , ,, , , , [RETURN], [RETURN],, , .19

At this point, most of the ambient signals havebeen deleted from your list. Some ambients maystill be present in the internal list because theyappeared during only one of the automatic measurements,which means that they would not havehad duplicate signals and thus would not havebeen deleted.The signals in the list are the peak and quasi-peakvalues of the EUT emissions and remaining ambientsignals. Next, find signals that are above thelimit. To do this, first sort the list by quasi-peakvalues with the highest levels at the top of the list:Press [MEASURE], , ,, , .Next, switch the column on that indicates the valueof the quasi-peak measurement versus the limit line.Press [MEASURE], , .Press , until is indicatedat the top of the column. (See Figure 14.)4.10 Evaluating measurement resultsIf all the values in the QP LL1 column of theinternal list are negative, the product emissionsare below the limit, and your product passes theradiated emissions requirements and your jobis completed.If some of the values are positive, then the quasipeakmeasurements are above the quasi-peak limitand the product fails radiated emissions measurements.To be sure that signals are not ambients,each signal should be remeasured. Use the demodulationfunction to listen to the signal. AM/FMdemodulation is a good tool to use to determinewhether or not a signal is an ambient.To listen to a signal do the following:Press [MEASURE], , .With the signal list on, highlight the signalof interest with the up/down keys.Press [DET/DEMOD], , ,.Figure 14. Measurements list compared to limit20

Adjust the volume to listen to the signal. If the signalis a local AM, FM, TV, or cellular phone, youshould be able to demodulate and listen to the signal.For improved FM demodulation performance,move the signal to within the three top graticules.To do this, press [AMPLITUDE], , [↓]until the signal is in the three top graticules. Thedemodulation function will enable the operatorto hear the audio part of the transmission bydwelling 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 toremove the power to the EUT, so using the demodulationfunction may be the preferred method ofidentifying ambients.) If you have determined thata signal is an ambient, the next step is to deletethe signal.Press [MEASURE], , ,, , highlightthe ambient signal to be deleted and press.After the ambient signals have been deleted fromthe list, the next step is to develop a report.4.11 Report developmentThe end result of all the above testing is a report.The report is used by the design engineer tocorrect any problems that are found during thetest process. You can assemble a report using the[MEAS SETUP], functions. Thecontents of the report can include a list of signals,and graphical representation of the signals.To define the report content, press ,then choose the items you would like to have in thereport. Your report can include screen, instrumentsettings, and signal list information. Examples ofscreens and lists are shown in Figure 15.List definition is a separate category. To definethe list, press and choose the itemsto be included in the list, such as detector results,limit comparisons, correction factors used, andshow marked signals. With the printer attached,press [MEAS SETUP], , ,, [PRINT]. All the items selected under reportdefinition will be printed sequentially.The report can be saved as an .htm file. Press[File], , , . Use the alphaeditor to change name and press [Enter].21

Figure 15: Example of a printed report22

HP 1940A5.0 Problem Solving and TroubleshootingAt this point, after the product is tested and theresults are recorded and printed, your productis either ready for full compliance testing andproduction or it must go back to the bench forfurther diagnosis and repair.If the product needs further redesign, the followingprocess is recommended.1. Connect the diagnostic tools as shown in Figure16 below.2. From the report, locate the problem frequencies.3. Use the probe to locate the source or sourcesof the problem frequencies.4. With the probe placed to give the maximumamplitudes, record the results to disk.5. Make circuit changes as necessary to reducethe emissions.6. Remeasure the circuit using the same settingsas before.7. Recall the previous measurement stored todisk and compare the results to the currentmeasurement.5.1 Diagnostics testing setupAs with emissions testing, the EMC analyzer mustbe set up to perform diagnostics testing. Correctionsfor the probe and amplifier must first be loadedinto the EMC analyzer. The Agilent 1945A probe kitcontains two probes: one for the 9 kHz to 30 MHzfrequency range and one for the 30 MHz to 1 GHzfrequency range. Connect the probe for the appropriatefrequency range and load in the correctionfactors by pressing the following:[FILE], , . Scroll to11940A or 11941A and press [ENTER].Switch on the corrections by pressing[Meas Setup], , ,, , ,.The next step is to load in the correction factorsfor the amplifier by pressing the following:[FILE], , . Scroll downto the 11909A and press [ENTER]. Selectthe correct units by [Meas Setup], ,, , ,The EMC analyzer is now calibrated in dBA/m,which is magnetic field strength units.Diagnostic measurement set-up:emissionsEMC analyzerPotential conclusion: radiation localizedto loop of pcb track, laid out parallelreduces emissions > 10 dB.Correction factorslimit linesDevice under testClose-field probeCircuit under testFigure 16. Diagnostics setup interconnectionNote: The Agilent E7401A has a built-in preamp.If it is found that additional gain is needed, theAgilent 11909A is recommended.23

5.2 Problem isolationUsing the report generated from the conductedand radiated emissions test, tune the EMC analyzerto one of the problem frequencies with narrowenough span to give adequate differentiationbetween signals.Move the close field probe slowly over the deviceunder test. Observe the display for maximumemissions as you isolate the source of the emissions.After you have isolated the source of theemissions, record the location and store the displayto disk. To store the display, insert a formatteddisk into Drive A and press the following:[FILE], 1 , , , .Use the alpha editor to name the trace, andpress [ENTER].Figure 17 shows the trace saved onto disk.Figure 17. Isolated signal source display241. Insure that the path is “A.”

The next step is to make design changes to reducethe emissions. This can be accomplished by addingor changing circuit components, redesigning theproblem circuit, or adding shielding.After the redesign, remeasure the results, comparingthe old trace before redesign to the new traceby recalling the saved trace off the card. To recallthe trace, press the following:[FILE], , .Scroll down to the trace you previously storedand press [ENTER].The trace is recalled into the Trace 1 area in theVIEW mode.Press [VIEW/TRACE], , .With your probe on the trouble spot, compareemissions before and after repairing the problem.(See Figure 18.)As you can see from the delta marker measurement,the new trace after the product redesign is10 dB below the previously stored trace. There isa one-to-one correlation between changes in closefield measurements and changes in far field measurements.For example, if you note a 10 dB changein measurements made by a close field probe, youwill note a 10 dB change when you perform a farfield measurement using an antenna and an EMCanalyzer.Conversely, if you find that the radiated emissionsfrom your EUT are failing a limit by 10 dB, thenyou will need to do some redesign to reduce theemissions by at least 10 dB. A good indication thatyou have accomplished your goal is to make a 10 dBchange with close field measurements.Figure 18. Emissions reduction comparison display25

Appendix A: Line Impedance Stabilization Networks (LISN)A1.0 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 coupledto the EMC analyzer using a high-pass filter,which is part of the LISN. Signals that are inthe pass band of the high-pass filter see a 50-Ωload, which 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.From powersourceLine Impedance StabilizationNetwork (LISN)1 µF50 µH0.1 mF1000WImpedance(ohms) 605040302010Frequency (MHz).01 .1 1 10 100Figure A-1. Typical LISN circuit diagramToEUTToReceiver or EMC analyzer(50 Ω)The 1 µF in combination with the 50 µH inductoris the filter that isolates the mains from the EUT.The 50 µH inductor isolates the noise generatedby the EUT from the mains. The 0.1 µF couples thenoise generated by the EUT to the EMC analyzeror receiver. At frequencies above 150 kHz, the EUTsignals are presented with a 50-Ω impedance.The chart in Figure A-1 represents the impedanceof the EUT port versus frequency.26

A1.2 Types of LISNsThe most common type of LISN is the V-LISN. Itmeasures the unsymmetric voltage between lineand ground. This is done for both the hot and theneutral lines or for a three-phase circuit in a “Y”configuration, between each line and ground. Thereare other specialized types of LISNs. A delta LISNmeasures the line-to-line or symmetric emissionsvoltage. The T-LISN, sometimes used for telecommunicationsequipment, measures the asymmetricvoltage, which is the potential difference betweenthe midpoint potential between two lines and ground.A2.0 Transient limiter operationThe purpose of the limiter is to protect the inputof the EMC analyzer from large transients whenconnected to a LISN. Switching EUT power on oroff can 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.HV symmetricTypes of LISNsNV unsymmetric1GroundV-LISNV2 unsymmetricV unsymmetric11/2 V symmetric 1/2 V symmetricV asymmetricV unsymmetric2Vector DiagramV-LISN:-LISN:T-LISN:Unsymmetric emissions (line-to-ground)Symmetric emissions (line-to-line)Asymmetric emissions (mid point line-to-line)Figure A-2. Three different types of LISNs27

Appendix B: Antenna FactorsB1.0 Field strength unitsRadiated EMI emissions measurements measurethe electric field. The field strength is calibratedin dBV/m. Field strength in dBV/m is derivedfrom the following :Biconical Antenna(30 - 300 MHz)P t =P D =total power radiated from an isotropicradiatorthe power density at a distance r from theisotropic radiator (far field)Broadband AntennaLog Periodic Antenna(30 - 1000 MHz) (200 - 1000 MHz)P D = P t /4r 2 R = 120ΩP D = E 2 /RE 2 /R = P t /4r 2E =(P t x 30) 1/2 /r (V/m)Far field 1 is considered to be >/2B1.1 Antenna factorsThe definition of antenna factors is the ratio ofthe electric 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-2. Antennas used in EMI emissions measurementsB1.2 Types of antennas used for commercial radiatedmeasurementsThere are three types of antennas used for commercialradiated emissions measurements.Biconical antenna: 30 MHz to 300 MHzLog periodic antenna: 200 MHz to 1 GHz(The biconical and log periodic overlap frequency)dB/m3025201510Antenna factorsBiconical@ 10mLog Periodic@ 1mBroadband antenna: 30 MHz to 1 GHz (Largerformat than the biconical or log periodic antennas)5Linear units:Log units:0 200 400 600 800 1000Frequency, MHzAF = Antenna factor (1/m) AF = EinE = Electric field strength (V/m) V outV = Voltage output from antenna (V)AF(dB/m) = E(dBµV/m) - V(dBµV)E(dBµV/m) = V(dBµV) + AF(dB/m)Figure B-1. Typical antenna factor shapes281. Far field is the minimum distance from a radiator where the field becomesa planar wave.

Appendix C: Basic ElectricalRelationshipsAppendix D: Detectors Used inEMI MeasurementsThe 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 (P 2 /P 1 )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 (V 2 /V 1 )A unit of measure used in EMI measurementsis dBV or dBA. The relationship of dBV anddBm is as follows:dBµV = 107 + P dBmThis is true for an impedance of 50 Ω.Wave length (l) is determined using the followingrelationship: = 3x10 8 / f (Hz) or = 300/f (MHz)D1.0 Peak detectorInitial EMI measurements are made using thepeak detector. This mode is much faster thanquasi-peak, or average modes of detection. Signalsare normally displayed on spectrum analyzers orEMC analyzers in peak mode. Since signals measuredin peak detection mode always have amplitudevalues equal to or higher than quasi-peak oraverage detection modes, it is a very easy processto take a sweep and compare the results to a limitline. If all signals fall below the limit, then theproduct passes and no further testing is needed.D1.1 Peak detector operationThe EMC analyzer has an envelope or peak detectorin the IF chain that 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.)Output of the envelope detectorfollows the peaks of the IF signalFigure D-1. Peak detector diagram29

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 annoyancefactor. As the repetition rate increases, the quasipeakdetector does not have time to dischargeas much, resulting in a higher voltage output.(See Figure D-2.) For continuous wave (CW) signals,the peak and the quasi-peak are the same.Since the quasi-peak detector always gives a readingless than or equal to peak detection, why notuse quasi-peak detection all the time? Won’t thatmake it easier to pass EMI tests? It’s true thatyou can pass the tests more easily; however, quasipeakmeasurements are much slower by two orthree orders of magnitude compared to using thepeak detector.Quasi-peak detector outputvaries with impulse rateQuasi-peakQuasi-peakPeak response detector reading detector responseTest limittTest limitD2.1 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 theoutput of the quasi-peak detector. The quasi-peakdetector also responds to different amplitudesignals in a linear fashion. High-amplitude, lowrepetition-ratesignals could produce the sameoutput as low-amplitude, high-repetition-ratesignals.D3.0 Average detectorThe average detector is required for some conductedemissions tests in conjunction with using the quasipeakdetector. Also, radiated emissions measurementsabove 1 GHz are performed using averagedetection. The average detector output is alwaysless than or equal to peak detection.D3.1 Average detector operationAverage detection is similar in many respects topeak detection. Figure D-3 shows a signal thathas just passed through the IF and is about to bedetected. The output of the envelope detector isthe modulation envelope. Peak detection occurswhen the post detection bandwidth is wider thanthe resolution bandwidth. For average detectionto take 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 noiseat the output of the envelope detector.tAAverage detectionFigure D-2. Quasi-peak detector response diagramtEnvelope detectorFiltersAverage detector30Figure D-3. Average detection response diagram

Appendix E: EMC Regulatory AgenciesThe following is a listing of addresses and phonenumbers for obtaining EMC regulation information.IECCISPRSales Department of the Central Office of the IECPO Box 1313, Rue de Verembe1121 Geneva 20, SwitzerlandCCIRITU, General Secretariat, Sales ServicePlace de Nation1211 Geneva, SwitzerlandAustraliaAustralia Electromechanical CommitteeStandards Association of AustraliaPO Box 458North Sydney N.S.W. 2060Telephone: +61 2 963 41 11Fax: +61 2 963 3896BelgiumComite Electrotechnique Belge3 Galerie Ravenstein, Boite 11B-1000 BruxellesTelephone: +32 2 512 00 28Fax: +32 2 511 29 38CanadaStandards Council of CanadaStandards Sales Division350 Sparks Street, Suite 1200Ottawa, Ontario K1P 6N7Telephone: 613 238 3222Fax: 613 995 4564Canadian Standards Association (CSA)178 Rexdale BoulevardRexdale (Toronto), Ontario MSW 1R3Telephone: 416 747 4044Fax: 416 747 2475DenmarkDansk Elektroteknisk KomiteStrandgade 36 stDK-1401 Kobenhavn KTelephone: +45 31 57 50 50Fax: +45 31 57 63 50FranceComite Electrotechnique FrancaisUTE CEdex 64F-92052 Paris la DefenseTelephone: +33 1 47 68 50 20Fax: +33 1 47 89 47 75GermanyVDE CERLAG GmbHAustieferungsstelleMerianstrasse 29D-6050 OFFENBACH a.M.Telephone: +49 69 8306-1Fax: +49 69 83 10 81IndiaBureau of Indian Standards, Sales DepartmentManak Bhavan9 Bahadur Shah Zafar Marg.New Delhi 110002Telephone: +91 11 331 01 31Fax: +91 11 331 40 62ItalyCometato Eletrotecnico ItalianoViale Monza 2591-20126 Milano MITelephone: +39 2 25 77 31Fax: +39 2 25 773 222JapanJapanese Standards Association1-24 Akasaka 4Minato-KuTokyo 107Telephone: +81 3 583 8001Fax: +81 3 580 14 1831

Appendix E: EMC Regulatory Agencies, continuedNetherlandsNederlands Normalisatie-InstituutAfd. Verdoop en InformatieKalfjeslaan 2, PO Box 50592600 GB DelftNLTelephone: +31 15 69 03 90Fax: +31 15 69 01 90NorwayNorsk Elektroteknisk KomiteHarbizalleen 2APostboks 280 SkoyenN-0212 Oslo 2Telephone: +47 2 52 69 50Fax: +47 2 52 69 61South AfricaSouth African Bureau of StandardsElectronic Engineering DepartmentPrivate Bag X191Pretoria0001 Republic of South AfricaSpainComite Nacional Espanol de la CEIFrancisco Gervas 3E-28020 MadridTelephone: +34 1 270 44 00Fax: +34 1 270 28 55SwedenSvenka Elecktriska KommissionenPO Bow 1284S-164 28 Kista-StockholmTelephone: +48 8 750 78 20Fax: +46 8 751 84 70United KingdomBritish Standards InstitutionBSI Sales DepartmentLinford WoodMilton Keynes MK14 GLETelephone: +44 908 22 00 22Fax: +44 908 32 08 56British Defence StandardsDEF STANMinistry of DefenceNorthumberland HouseNorthumberland AveLondon WC2N 5 BPTelephone: +01 218 9000United States of AmericaAmerica National Standards Institute Inc.Sales Dept.1430 BroadwayNew York, NY 10018Telephone: 212 642 4900Fax: 212 302 1286FCC Rules and RegulationsTechnical Standards Branch2025 M Street N.W.MS 1300 B4Washington DC 20554Telephone: 202 653 6288FCC Equipment Authorization Branch7435 Oakland Mills RoadMS 1300-B2Columbia, MD 21046Telephone: 301 725 1585SwitzerlandSwiss Electromechanical CommitteeSwiss Electromechanical AssociationSeefeldstrasse 301CH-8008 ZurichTelephone: +41 1 384 91 11Fax: +41 1 55 14 2632

Glossary of Acronyms and DefinitionsAmbient level1. The values of radiated and conducted signaland noise existing at a specified test location,and time 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,circuit noise, or other interference generatedwithin the measuring set compose the ambientlevel.Amplitude modulation1. In a signal transmission system, the process, orthe result of the process, where the amplitudeof one 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 chamberA shielded room that is lined with radio-absorbingmaterial to reduce reflections from all internalsurfaces. Fully lined anechoic chambers have suchmaterial on all internal surfaces—walls, ceiling,and floor. It’s also called a “fully anechoic chamber.”A semi-anechoic chamber is a shielded roomthat has absorbing material on all surfaces exceptthe floor.Antenna (Aerial)1. A means for radiated or receiving radio waves.2. A transducer that either emits radio frequencypower into space from a signal source or interceptsan arriving electromagnetic field, convertingit into an electrical signal.Antenna factorThe factor that, when properly applied to the voltageat the input terminals of the measuring instrument,yields the electric field strength in volts permeter and a magnetic field strength in amperesper meter.Antenna-induced voltageThe voltage that is measured or calculated to existacross the open-circuited antenna terminals.Antenna terminal conducted interferenceAny undesired voltage or current generated withina receiver, transmitter, or their associated equipmentappearing at the antenna terminals.Auxiliary equipmentEquipment not under test that is neverthelessindispensable for setting up all the functions andassessing the correct performance of the EUTduring its exposure to the disturbance.BalunAn antenna-balancing device that facilitates useof coaxial feeds with a symmetrical antenna suchas a dipole.Broadband emissionBroadband is the definition for an interferenceamplitude when several spectral lines are withinthe RFI receiver’s specified bandwidth.Broadband interference (measurements)A disturbance that has a spectral energy distributionsufficiently broad, so that the response ofthe measuring receiver in use does not vary significantlywhen tuned over a specified number ofreceiver bandwidths.Conducted interferenceInterference resulting from conducted radio noiseor unwanted signals entering a transducer (receiver)by direct coupling.33

Cross couplingThe coupling of a signal from one channel, circuit,or conductor to another, where it becomes anundesired signal.Decoupling networkAn electrical circuit for preventing test signalsthat are applied to the EUT from affecting otherdevices, equipment, or systems that are not undertest. IEC 801-6 states that the coupling and decouplingnetwork systems can be integrated in onebox or they can be in separate networks.Dipole1. An antenna consisting of a straight conductor,usually not more than a half-wavelength long,divided at its electrical center for connectionto a transmission line.2. Any one of a class of antennas producing aradiation pattern approximating that of anelementary electric dipole.Electromagnetic Compatibility (EMC)1. The capability of electronic equipment of systemsto be operated within a defined margin ofsafety in the intended operational environment,at designed levels of efficiency, without degradationdue to interference.2. The ability of equipment to function satisfactorilyin its electromagnetic environment withoutintroducing intolerable disturbances into thatenvironment or into other equipment.Electromagnetic interferenceThe impairment of a wanted electromagnetic signalby an electromagnetic disturbance.Electromagnetic waveThe radiant energy produced by the oscillationof an electric charge, characterized by oscillationof the electric and magnetic fields.EmissionElectromagnetic energy propagated from a sourceby radiation or conduction.Far fieldThe region where the power flux density from anantenna approximately obeys an inverse squareslaw of the distance. For a dipole, this correspondsto distances greater than one-half—where l is thewavelength of the radiation.Ground plane1. A conducting surface of plate used as a commonreference point for circuit returns and electricor signal potentials.2. A metal sheet or plate used as a common referencepoint for circuit returns and electrical orsignal potentials.Immunity1. The property of a receiver or any other equipmentor system enabling it to reject a radiodisturbance.2. The ability of electronic equipment to withstandradiated electromagnetic fields without producingundesirable responses.IntermodulationMixing of two or more signals in a nonlinear element,producing signals at frequencies equal tothe sums and differences of integral multiplesof the original signals.IsotropicHaving properties of equal values in all directions.MonopoleAn antenna consisting of a straight conductor,usually not more than one-quarter wavelengthlong, mounted immediately above, and normal to,a ground plane. It is connected to a transmissionline at its base and behaves, with its image, likea dipole.34

Narrowband emissionThat which has its principal spectral energy lyingwithin the bandpass of the measuring receiverin use.Open areaA site for radiated electromagnetic interferencemeasurements that is open, flat terrain at a distancefar enough away from buildings, electriclines, fences, trees, underground cables, and pipelinesso that effects due to such are negligible.This site should have a sufficiently low level ofambient interference to permit testing to therequired limits.StriplineParallel plate transmission line to generate anelectromagnetic field for testing purposes.SusceptibilityThe characteristic of electronic equipment thatpermits undesirable responses when subjectedto electromagnetic energy.PolarizationA term used to describe the orientation of the fieldvector of a radiated field.Radiated interferenceRadio interference resulting from radiated noiseof unwanted signals. Compare radio frequencyinterference below.RadiationThe emission of energy in the form of electromagneticwaves.Radio frequency interferenceRFI is the high-frequency interference with radioreception. This occurs when undesired electromagneticoscillations find entrance to the high-frequencyinput of a receiver or antenna system.RFI sourcesSources are equipment and systems—as well astheir components—that 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 electromagneticfields from causing performance degradationand to prevent emissions from causing interferenceto outside activities.35

By internet, phone, or fax, get assistance with all yourtest and measurement needs.Online Assistancewww.agilent.com/find/assistPhone or FaxUnited States:(tel) 1 800 452 4844Canada:(tel) 1 877 894 4414(fax) (905) 206 4120Europe:(tel) (31 20) 547 2323(fax) (31 20) 547 2390Japan:(tel) (81) 426 56 7832(fax) (81) 426 56 7840Latin America:(tel) (305) 269 7500(fax) (305) 269 7599Australia:(tel) 1 800 629 485(fax) (61 3) 9272 0749New Zealand:(tel) 0 800 738 378(fax) (64 4) 495 8950Asia Pacific:(tel) (852) 3197 7777(fax) (852) 2506 9284Product specifications and descriptions in thisdocument subject to change without notice.Copyright © 1999, 2000 Agilent TechnologiesPrinted in U.S.A. 6/005968-3661E