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AUTOMOTIVE EMCAutomotive Component EMC Testing:CISPR 25, ISO 11452-2 and Equivalent StandardsVicente RodriguezETS-Lindgren L.P.Email: Vince.Rodriguez@ets-lindgren.comAbstract: This paper presents compiles some information about EMC standards. In particular, the paper concentrates on EMC standardsdedicated to testing automotive components. The paper presents an introduction of the primary automotive component standards. Based onthis introduction, the CISPR 25 and the ISO 11452-2 automotive EMC standards are analysed since they are the basis for most otherstandards. The anechoic chamber requirements are studied in detail.Keywords: EMC measurements, automotive, chamber requirementsIntroductionCISPR and ISO documents for guidance on how to performthe test and where to perform it.Finally, each manufacturer has internal standards thatspecify the levels and testing that components used in theirvehicles must meet. As with the government standards,these documents usually refer to the CISPR and ISO documents. For U.S. based manufacturers, SAE documents arealso a guide. The following tables provide an overview ofthe most common component EMC standards [1].Automotive standards for EMC are developed mainly bya few organizations. CISPR, SAE and the ISO are thoseorganizations. CISPR and ISO are internationalorganizations. SAE is mainly a United States basedorganization. As with other areas of EMC, there exist somegovernment organizations that also regulate the testing ofcomponents. In most cases their standards refer to theTable 1SAEJ1113/126Some of the main SAE automotive component standardsTitleTypeEquivalentElectromagnetic Compatibility measurement proceduresand limits for vehicle components (except aircraft),60 Hz耀18 GHzN/AISO 11452-1Test SetupChamberRequirementDefinitionsN/AConducted immunity test covering30 Hz to 250 kHzShielded room2Electromagnetic Compatibility measurement proceduresand limits for vehicle components (except aircraft) con原ducted immunity, 30 Hz to 250 kHz all leadsCI3Conducted immunity, 250 kHz to 500 MHz direct in原jection of radio frequency (RF) powerCIISO 11452-7Conducted immunity test 250 kHzto 500 MHzShielded room4Immunity to radiated electromagnetic fields—bulkcurrent injection (BCI) methodRIISO 11452-4Radiated immunity using the BCImethodShielded room11Immunity to conducted transients on power leadsCIISO 7637-2Conducted immunity to transientsShielded room12Electrical interference by conduction and coupling—coupling clampCIISO 7637-3Conducted immunity to differentcoupling mechanismsShielded room13Electromagnetic compatibility procedure for vehiclecomponents-immunity to electrostatic dischargeESDISO 10605ESDShielded roomSAFETY & EMC 2011
AUTOMOTIVE EMC(Continued)An absorber lined chamber isre quired. Antennas and field gener原ator to cover the range are required.No need to scan antenna; a testbench is required.Absorber linedchamber with aspecificarrangementISO 11452-8Helmholtz coils are usedShielded roomRIISO 11452-5Radiated immunity with a TEMdeviceImmunity to radiated electromagnetic fields 10 kHz to200 MHz—Crawford TEM cell, and 10 kHz to 5 GHzwideband TEM cellShielded room,open sidesdevicesRIISO 11452-3Shielded TEM devicesN/A27Immunity to radiated electromagnetic fields reverbera原tion methodRI41Limits and methods of measurement of radio distur原bance characteristics of components and modules forthe protection of receivers used on board vehicles21Electromagnetic compatibility procedure for vehiclecomponents—immunity to electromagnetic fields 10 kHzto 18 GHz absorber lined chambersRI22Electromagnetic compatibility measurement procedurefor vehicle components—immunity to radiated magnet原ic fields from power linesRI23Electromagnetic compatibility measurement procedurefor vehicle components—immunity to radiated electro原magnetic fields,10 kHz to 200 MHz stripline method24REISO 11452-2ECE 10-CISPR 25Reverberation chamber design isbased on the SAE J1113/27 -1995Standard (or equivalently, berGM9114P -1997, GM9120P -1993),the draft GM Worldwide Engineer原ing Standard GMW3100GSAn absorber lined chamber is re原quired. Antennas and field generator Absorbed linedto cover the range are required. No chamber or TEMneed to scan antenna; a test bench cellis requiredTable 2 ISO 11452 and some of its Test SetupN/ASAE J1113/21An absorber lined chamber is required.Antennas and field generator to coverthe range are required. No need to scanAbsorber linedchamber1Part 1: General and definition2Part 2: Absorber lined chamberRISAE J1113/21An absorber lined chamber is required.Antennas and field generator to coverthe range are required. No need to scanAbsorber linedchamber3Part 3: Transverse electromagnetic (TEM) cellRISAE J1113/24TEM cellN/A4Part 4: Bulk current injectionRISAE J1113/45Part 5: StriplineRISAE J1113/237Part 7RITable 1 does not show all the EMC standards related toautomotive published by the SAE, but it gives an overviewof some of them plus it cross-references them to theequivalent ISO standard or CISPR documents.SAE J1113/3RadiatedmethodimmunityusingtheRadiated immunity using a stripline-BCIShielded roomShielded roomShielded roomAs with Table 1, Table 2 is not intended to show all thedifferent parts of the standard, but to show the complexityof the standard documents and the many parts and methodsthat are covered under them. Not shown in Table 2 areSAFETY & EMC 201127
AUTOMOTIVE EMCparts such as Part 8 that deals with magnetic field immunityand that is equivalent to SAE J1113/22. ISO 11542-8 wasintroduced in 2007 and it takes some methodology fromMIL-STD-461 [2].As mentioned above, government standards and directives in many cases refer to the CISPR or ISO methods.2004/144EC, which surpassed 95/54 EC, is a Europeandirective for vehicle EMC. Its sections related to automotivecomponents follow the directions given in the CISPR 25document.standard. The standard states that the electromagneticnoise level in the test area has to be 6 dB lower than thelowest level being measured. If CISPR 25 is consulted, wefind that levels as low as 18 dB (μV/m) this means that theambient noise must be 12 dB (μV/m) minimum. This callsfor a shielded room to be used. The shielded room will keepall the noise from the environment out of the test area sothat the EUT will be the main source of noise.CISPR 25Most people tend to think of CISPR 25 as a vehiclecomponent emissions testing. The truth is that CISPR 25 isa far more complex standard. The title of the standard isself-describing; it suggests that CISPR 25 deals with "radiodisturbance characteristics for the protection of receiversused on board vehicles, boats and on devices" [3].Figure 2Figure 1CISPR 25 EUTsHence CISPR 25 deals with to what level electric andelectronic systems affect receivers mounted on automobilespowered by internal combustion engines, boats powered byinternal combustion engines, and devices also powered byinternal combustion engines, but not for the transport ofpeople. This last category includes compressors, chainsaws,garden equipment, etc. Furthermore, the standard has twoparts. One part deals with a full vehicle or system test inwhich the antennas mounted on the vehicle are used tosense the noise generated by the different electric andelectronic systems mounted on the same vehicle. A sort of aself-immunity test is performed. The other section of thestandard deals with measurement of component andmodules. We are going to concentrate on this particularsection in this paper. More specifically, this paper is goingto concentrate on the chamber requirements for the28SAFETY & EMC 2011A shielded room blocks the noise from outdoor sourcesof EM interferenceWhile at low frequencies the shielded room is too smallto support resonant modes, it is very possible for thesemodes to exist as frequency increases. When these resonant modes appear, they can cause significant error on themeasurements. To avoid these errors, the shielded room iscovered with absorber on its interior walls. CISPR 25covers a frequency range of 150 kHz to 2 GHz. Unfortunately, absorber technology is unable to provide absorptionat levels down in the 150 kHz range. On the other side, aswe will see the chamber sizes are small generally so noresonant behaviour appears down at those low frequencies.The standard thus concentrates on 70 MHz and above. Thestandard requires that the absorber used must have betterthan -6 dB absorption at normal incidence. To achievethese levels, there are two types of technology on themarket today. Polyurethane absorbers usually 36 inches(1 m) in depth can be used and hybrid absorbers usingferrite materials and polyurethane foams are also a goodchoice. Figures 3 and 4 show the typical performance ofthese materials compared to the CISPR 25 limit.The typical CISPR 25 anechoic chamber is guided bythe standard. Several guidelines must be followed when
AUTOMOTIVE EMCFigure 3 Typical performance of 36" materialFigure 4 Typical performance of hybrid materialsizing the chamber and the starting point is going to bethe EUT, which is going to determine the size of the testbench. Figure 5 shows a typical test bench used in aCISPR 25 chamber and an ISO 11452-2 type chamber.Figure 5and to send signals to that device. Thecables are put together in a cableharness that is placed in the front ofthe bench. It is the cable harness thatis illuminated since at lower frequencies(frequencies for which the device undertest is electrically small) the maincoupling to radiated fields will occurthrough the cables feeding the device.This same process is used inMIL-STD-461 and in ISO 11452 [2]. Aline impedance stabilization network isused to bring power to the device.Figure 6 shows how the size of thebench is determined. The bench mustextend all the way to the shield. Inmost cases, it is grounded to the wall ofthe shielded room. But it can begrounded to the floor as well.Once the size of the bench has beendetermined based on the largest EUT,the next step is to determine the widthof the chamber. For the present exercisewe will assume that hybrid absorberwith a depth of 60 cm is used to linethe walls and ceiling of the chamber.Figure 4 has shown that this type of absorber is sufficientto meet the CISPR 25 requirements. Figure 7 shows thewidth of the chamber. The width is based on the thicknessof the absorber material and a one meter space is then leftbetween the bench and the tips of the absorbing material.The bench of course must fit inside the chamber and it isthe dominant factor.A typical conductive test benchAs Figure 5 shows, the bench must accommodate thelargest EUT and all the cables that are needed to powerFigure 6Sizing the benchSAFETY & EMC 201129
AUTOMOTIVE EMCleft. The largest antenna is going to be the active rodmonopole. The monopole is used with an extremelyelectrically small ground plane. Per the standard, themonopole rod is about 80 cm in length and it is positionedsuch that the ground plane is at the same level as thebench which as Figure 5 suggests is 90 cm in height. The1 m rule for the separation between antenna and absorbertip will determine the size of the chamber as shown inFigure 9.Figure 7Width of the CISPR 25 chamberAt this point, only the height and the length of thechamber are yet to be determined. CISPR 25 has somerules that are going to determine the necessary space.The first and most important rule is the test distance. PerCISPR 25, the emissions are measured at a distance of 1 mfrom the cable harness to the antenna. Since CISPR is adocument prepared by the CISPR organization, its rules onantennas and receivers are given by the CISPR 16document [4]. The recommended antennas are listed in thestandard. For low frequencies, an active rod monopoleantenna is preferred. At frequencies between 30 MHz and200 MHz, a typical biconical antenna is the recommendedantenna. From 200 MHz to 1 GHz, the antenna of choice isa log periodic dipole array (LPDA) and finally from 1 to2 GHz, the author recommends a dual ridge horn antenna.The other rule stated in CISPR 25 is that no part of theantenna can be closer than 1 m away from the tips of theabsorbing material. These rules and recommended antennasdefine the length and height of the chamber. The 1 mdistance to the cable harness is measured from the axis ofthe antenna elements for the monopole rod and the biconicalantenna. For the LPDA, the distance is measured from thetip of the antenna. Finally, for the horn antennas thedistance is measured from the front or aperture plane ofthe antenna. The longest antenna is the LPDA. TypicalLPDAs for the 200 MHz to 2 GHz range are about 1 m inlength. In addition to the 1 m test distance and the 1 m forthe antenna size, we have 1 m from the back of the antennato the tips of the absorber.Figure 8 shows the antenna (an LPDA) in the chamberfor the CISPR 25 set up. The height is the only dimension30SAFETY & EMC 2011Figure 8Determining the length of the chamber for CISPR 25Figure 9Height of the CISPR 25 chamberHence, from what we've seen above, a chamber linedwith hybrid absorber with a size of 5.2 m wide by 6.2 mlong and 3 . 6 m high will meet the requirements forperforming CISPR 25 tests. But as the tables abovesuggest, such a chamber will also be usable for SAEJ1113/41 and, as we will see in the next section of thispaper, this chamber will also meet the requirements of
AUTOMOTIVE EMCISO 11452-2. Furthermore, since this is a shielded environment, most of the standards requiring a shielded roomcan be performed inside the chamber designed in thepresent section.CISPR 25 does not have a mandatory test to validate thechamber. The latest versions call for a comparison betweenthe performance in the chamber and the OATS. One mustbe very careful in this comparison. Especially at lowfrequencies (below 30 MHz or below 100 MHz if no hybridabsorber is used) the grounding of the bench is going tohave a large effect. It is important to perform the measurement on the OATS using a bench that it is grounded in thesame way as the bench is grounded in the chamber. Sinceit is easier to ground the bench at the OATS to the groundplane, it is recommended that the same grounding is usedin the chamber during the comparison measurements.Additionally, damped resonant behaviours related to thechamber size will not be seen on the OATS. Some manufacturers prefer to do an inter-comparison betweenchambers using a golden unit or a reference radiator.magnetic energy to be generated to make electronic systemsfail. In addition, most countries forbid the indiscriminateradiation of energy across wide frequency bands withoutlicenses. Since the test is conducted at frequencies above200 MHz, the chances of resonant behaviours beingdeveloped inside the shield room is increased. Hence, theuse of absorber is required. The chamber is treated suchthat the reflectivity in the area of the EUT is -10 dB.Figures 3 and 4 show that for the 200 MHz to 18 GHzrange, the -10 dB level is higher than the typical reflectivity of the recommended materials. This means that thesame absorber used in the CISPR 25 chamber can be usedin the ISO 11452-2 chamber. ISO 11452-2 does not haveany specifications on the chambers. It is recommendedthat a dual ridge horn antenna be used for the 200 MHz to2 GHz range. Above that, octave horns and standard gainhorns with high gain are the preferred choice.ISO 11452-2To conclude this paper, we shall talk a bit about theantennas. Specifically, we are going to concentrate on thetypical biconical antenna, LPDA and DRHA recommendedfor CISPR 25 and the DRHA recommended for ISO11452-2. Recently it has become important to understandthe radiation characteristics of these antennas. The typicalbiconical antenna, shown in Figure 10, is an omnidirectional radiator.The ISO 11452-2 standard applies to the 200 MHz to18 GHz range. This is an immunity standard and likemany automotive, military and aerospace standards, it callsfor very high fields to be generated. Table 3 shows theseverity levels. At frequencies below 200 MHz, antennasget physically large and also they tend to be less efficient.For frequencies below 200 MHz, the standard recommends the methods stated in Parts 4, 3, and 5 of theISO 11452 standard. Those sections describe the bulkcurrent injection, TEM and stripline methods. These othermethods are far more efficient and economical to test forimmunity to high fields.Table 3Field/(V/m)II50IIIIVVPatterns and GroundedISO 11452-2 severity levelsSeverity LevelIOn Antennas,Benches2575100(open to the users of the standard)The nature of the immunity test calls for a shieldedroom. After all, the test calls for high levels of electro-Figure 10Typical biconical antennaSAFETY & EMC 201131
AUTOMOTIVE EMCIts pattern shown in Figure 11 at 100 MHz is typical ofthe radiation pattern across the entire range. From thesepatterns we can extract the High Power Beam Width(HPBW). For the H-plane, it is clear that the HPBW islarger than 180毅, there is no main beam. For the E-plane,the beamwidth ranges between 40 毅 and 90毅 . On themeasured data we can see the effects of the stem and balunholder on the pattern. The stem is oriented to the 180 毅mark. We can see how on the H-plane the balun holderreduces by 2 to 3 dB the intensity of the radiation. Thebeamwidth of the measured data and the computed datatracks each other nicely.In Figures 13 to 14, we see the measured and modelledperformance of the LPDA antenna. There are clearly somedifferences between the measured data and the computedresults. Close examination reveals that the error is under3 dB. There are several sources of error in the measurement. Using the measured values for the HPBW , the EMCengineer will err on the side of safety.Figure 13 LPDA measured and computed pattern at 400 MHzFigure 11Measured and computed patterns at 100 MHzFigure 12 shows a picture of the LPDA antenna and thenumerical model created in MW Studio TM. This is the othertypical antenna recommended by CISPR.Figure 14 LPDA measured and computed pattern at 1 GHzFigure 1232A picture of the measured LPDA and the numericalmodel geometry in MW StudioTMSAFETY & EMC 2011Figure 13 shows the data at 400 MHz; there is verygood agreement between the measured and the computedresults. The data for 1 GHz (shown in Figure 14) showsgood agreement between measured and computed data forthe main beam.The HPBW of the LPDA antennas is usually fairly flat.This is especially the case for the center of the frequencyband that the antenna covers. From about 200 to 1 000 MHzthe antenna being measured exhibits a HPBW rangingfrom 100毅 to about 60毅 for both planes.Dual ridge horn antennas are the antenna of choice forhigher frequencies. This family of antennas have beendescribed numerous times in the literature. Their radiationpattern has been described starting with [5]. Reference [5]
AUTOMOTIVE EMCdescribed issues with the radiation pattern of these antennasat frequencies above 12 GHz for models operating in the 1to 18 GHz range. References [6] and [7] introduced a newdesign for the 1 to 18 GHz range that has a better behavedpattern where the main beam does not split into multiplebeams. Figure 15 shows the measured radiation patternsfor the horn analyzed in [5] and the one introduced in [6]and [7]. The data on the left shows a better behaved patternwithout the narrow beams and the split main lobe of thepattern from the antenna on the right.In references [8] and [9] several improvements weremade to the radiation patterns of dual ridge horn antennasoperating in the 200 MHz to 2 GHz range. These are thehorns recommended by the author for ISO 11452-2. Thesemodifications corrected the nulls in the middle on the mainbeam.The new (left) and traditional (right) dual ridge horn antenna for the 10 18 GHz range are shown.Figure 15Figure 16H-plane radiation patterns from 10 18 GHzComparison of pattern at 2 GHz for the traditional and improved 200 MHz to 2 GHz D
AUTOMOTIVEEMC SAFETY&EMC2011 Table3ISO11452-2severitylevels SeverityLevel Field/(V/m) I25 II50 III75 IV100 V(opentotheusersofthestandard) Figure10Typicalbiconicalantenna
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