Electromagnetic compatibility describes a state in which the electromagnetic environments produced by natural phenomena and by other electrical and electronic devices do not cause interference in electronic equipment and systems of interest. Of course, in order to reach this state, it is necessary to reduce the emissions from sources that are controllable, or to increase the immunity of equipment that may be affected, or to do both.

It is important to understand that EMC as defined does not absolutely prevent interference from occurring. Emissions from various sources are variable; lightning impulses on power lines, for example, vary with the level of lightning current and its distance from a home or office. In addition, the immunity of a particular piece of equipment can vary; exemplifying this case is the fact that induced voltages on a circuit board are strong functions of the angle of incidence and the polarization of the incident electromagnetic (EM) field. Recognition of this variability has led to a balance being found between immunity and emissions for a particular type of disturbance, sufficient to prevent problems in a large percentage—but not all—of the cases of interest.

To try to eliminate all possibility of interference by decreasing emissions and increasing immunity further could incur a high cost to industry and could prevent new technologies from emerging. For example, a restriction lowering the transmitting power of cellular telephones so that consumers could place their cell phones on top of any electronic equipment might compromise the performance and economic viability of such communication systems. On the other hand, a requirement that all commercial electronic equipment perform without malfunction at ambient levels of 50 V/m would place a financial burden on manufacturers of a large range of equipment. A good compromise is to alert consumers to reasonable use restrictions (although higher immunity levels may be necessary when malfunctions could be a threat to human safety).

The focus of work in the area of EMC today is standardization, especially within international organizations. The requirements of the World Trade Organization and the prevalent desire to reduce global trade barriers have resulted in a strong emphasis on promulgating and implementing international standards. Of course, it is clear that regional developments, such as the European Directive on EMC, have strongly influenced the pace of work.

Regarding international standards bodies, IEC has undertaken most of the EMC standardization work. Significant efforts are also going forward in the International Organization for Standardization (ISO) and International Telecommunications Union (ITU).

IEC and its two principal horizontal EMC committees, the International Special Committee on Radio Interference (CISPR) and Technical Committee 77, have developed, and are continuing to develop, a significant range of basic EMC standards that define the measurement and test methods necessary for reliable technical standards. In the area of emissions, CISPR and Subcommittee 77A also are developing emission limits for high-frequency EM fields and low-frequency power-line disturbances, respectively. ACEC coordinates the EMC work within IEC and also coordinates with other standards bodies to reduce duplication in the marketplace.

ISO and the ITU are endeavoring to develop standards dealing mainly with moving vehicles and communication systems, respectively. In particular, ISO is actively working to create automotive, aircraft, and space EMC standards. The ITU deals with the EMC aspects of emerging telecommunications equipment, including both radio and wired technologies. Both organizations are coordinating their efforts with IEC in the hope of minimizing the number of basic EMC standards developed. The aim is that industry not be required to test and certify the same or similar equipment to conflicting standards.

An important aspect of the international standards being developed is their voluntary nature. However, commercial contracts or regional standards organizations may call for their mandatory application.

IEC has focused its EMC standardization work in four main areas. The commission is concentrating on developing:

As mentioned earlier, ACEC coordinates the EMC activity within IEC. The advisory committee wrote IEC Guide 107 to provide guidance to IEC committees on properly developing EMC standards and reports.¹ To accomplish its work, ACEC meets two or three times a year to consider advances in EMC standardization within and outside of IEC. After every meeting, it offers recommendations to IEC Committee of Action for consideration. ACEC consists of technical experts in the field of EMC and representatives of the major IEC committees that develop basic and product EMC standards.

A major standards-setting challenge involves the translation of emission limits and basic standards into product standards. Although CISPR has made a considerable effort to establish high-frequency emission limits, several cases of product standards in which those limits were ignored or improperly applied are known. Unfortunately, such errors are not always detected before the product standard is published and thus may take years to correct. ACEC is developing a procedure for solving this problem by tracking product standards under development to improve the accuracy of their EMC clauses.

A relatively new area of concern involves the generation of power-frequency harmonics by electronic equipment. Owing to the large number of electronic devices with switched-mode power supplies coming into use, these harmonics can be significant enough to propagate through the power network and cause interference to other consumer-owned equipment. Work is ongoing to develop standards that balance the needs of electronics manufacturers and power utilities.

The need to develop basic test methods that are applicable to test frequencies above 1 GHz also raises concern. This concern has urgency because of the introduction of ever more commercial products operating at higher frequencies than those previously used. New test methods such as the reverberation chamber do offer advantages at higher frequencies, namely, better coverage of angles of incidence and polarization with a concomitant reduction of test time. IEC is working to develop a basic standard, 61000-4-21, that will provide reverberation chamber testing as an option to those interested in an alternative test method.²

Several important current trends in technology are likely to continue well into the future. The most obvious is the increasing density of microprocessors in homes, businesses, factories, and transportation vehicles.

Proliferation of Microprocessors. Fixed microprocessors incorporated into many electrical appliances are making these household machines "smart." It is now possible to buy a refrigerator with a built-in computer. There are plans to develop this appliance to the point that it will know when food items are used up and be able to order replacement supplies through the Internet. Compatibility problems engendered by the development of such smart products may not be apparent at first, but consider that EMC is based, in part, on physical distances between emitting devices and "victimized" devices. That there will in the future be many more emitters and "victims" within a small electronics-rich room raises a concern. Will the consumer know that separating installed equipment can reduce interference problems?

Although the problem of fixed microprocessors may be solvable, what happens when numerous mobile transmitters are introduced into a fixed space? Clearly, the cell phone will continue to develop, and the number of instruments in use will increase. And now the possibility of a new set of transmitters being placed in nearly every piece of electronics arises with Bluetooth technology.

Bluetooth is a specification for a frequency-hopping radio technology that uses the unregulated 2.4 GHz ISM band (for industrial, scientific, and medical equipment) to communicate automatically between electronic devices within a range of approximately 30 m. More than 1200 companies worldwide have accepted the operational specification for Bluetooth. Projections have 400 million devices using Bluetooth by 2004.³

While it is apparent that devices designed to use Bluetooth should work properly when exposed to the incident radio signal, it is unclear whether other devices not designed for Bluetooth will operate in the vicinity without interference. In addition, Bluetooth itself could experience difficulty near microwave ovens. Although the field levels produced by microwave ovens have been considered in the development of Bluetooth, the cooking of different types of foods has the potential to reduce the efficiency of communications.

Higher Operating Frequencies. Another trend is the continual increase in operating frequency of products coming into the market. While cell phone technology has exceeded 1 GHz and Bluetooth will operate at 2.4 GHz, products involving satellite communications operate near 10 GHz and automobile radar systems involve frequencies above 40 GHz. The new frequencies are not in themselves necessarily a concern, but one aspect of the higher frequencies could be a problem. Higher frequencies have smaller wavelengths and are able to penetrate equipment enclosure seams and apertures more easily than lower frequencies. The wavelength of 100 MHz is 3 m, of 1 GHz is 30 cm, and of 10 GHz is 3 cm. For a 2-cm-long, 1-mm-wide seam in a metal enclosure, the attenuation of each of these fields 3 cm behind the aperture can be calculated as 79, 59, and 39 dB, respectively. In addition to the increase in the disturbing environment that comes with higher operating frequency, the development of new microprocessors operating at clock speeds of 1 GHz introduces the possibility of more-direct interference in the operation of electronic systems, in terms of both immunity and emissions.

Large Equipment and Systems. The EMC standardization process has succeeded in producing test methods to evaluate the acceptability of equipment and small systems built by manufacturers. It has been difficult, however, to develop standard methods for evaluating the immunity of large equipment or of systems that are installed together for the first time. Size is a seriously problematic factor: test facilities of large sizes are expensive to build, and immunity testing performed at open-area test sites can threaten other equipment that are not under test. Problems occur even with emissions testing. To establish the level of emissions from a particular piece of equipment can be difficult after the unit has been installed in an operating factory due to simultaneous emissions from other equipment not under test.

Health and EM Fields. Yet another realm of concern involves safety aspects of electromagnetic fields. Alarms have sounded in two principal areas.

The first expresses a concern about the direct effects EM fields may have on human health. The putative health hazard is referred to as EMF, an unfortunate acronym derived from, simply, "electromagnetic fields." Recent EMF activities at the International Commission on Non-Ionizing Radiation Policy and the World Health Organization have resulted in an IEC initiative to support those organizations by developing measurement standards. Georges Goldberg, chairman of an ECEC task force, was instrumental in convincing IEC to establish Technical Committee 106 to examine test methods for EMF.

A related area of interest involves the possibility of electromagnetic disturbances causing electronic systems to malfunction and thus present a safety risk, as, for example, a cell phone in a factory causing an industrial robot to behave so as to injure a worker. Again, IEC is active in this area, which Goldberg discusses in a recent paper.⁴

A third area of concern is referred to as intentional EMI. In such a scenario, high-level EM transients are directed at electronic systems in a commercial building in order to stop the equipment from operating properly. This capability could threaten the safety of people if criminals or terrorists targeted modes of transportation such as airplanes or automobiles. IEC subcommittee 77C is addressing this issue, working to establish the seriousness of the threat and to develop methods to protect equipment and systems from EM disturbances of hostile origin.

Accelerating Product Life Cycles. Several trends pertaining to the structural aspects of EMC standardization warrant mention. In the EMC standardization process, as noted earlier, it is a continual problem to achieve EMC through a balance affecting the emitters (by lowering emission limits) and the potential victims (by increasing immunity levels).

The rapidity of technological change, and the resulting short span of time from product concept and development to production, and even to the end of the product's life, has made standards development more difficult. This technological flux gives EMC standardization bodies very little time to evaluate the impact of new technologies on the preservation of EMC. When product cycles become shorter than the time required to develop a standard to cover the products, instability reigns. Also, when companies developing new electronic products and technologies do not participate in the standardization process, the likelihood of interference between devices increases.

A Paucity of EMC Engineers. Finally, structural problems in the standardization process itself are likely to be the source of difficulties in the near future. The availability of EMC experts in all areas from product development to standards writing is the foremost problem. People involved in the discipline of electromagnetics are seeing that fewer engineers are graduating with the credentials necessary to deal with EMC challenges. The competition and rewards in industry today quite evidently are for computer programmers and Internet experts. Many engineers who have worked in the EMC field are meanwhile nearing retirement, and some of the others do not receive support from their management for work in standardization.

The second problem resides with the standardization bodies themselves. With the digital revolution, everyone wants a digital copy of the latest standard. But for financial reasons, IEC and its national committees need money raised through the sale of standards to keep these organizations operating. How this problem will be solved is not clear.

How can EMC problems be solved in the future? Many approaches have been suggested, and some of them are beginning to be implemented.

Consistency of Standards. One major strategy is to continue and even intensify the focusing of EMC standards within IEC. This effort should involve even closer cooperation with ISO and the ITU in order to put limited EMC expert resources to the most efficient use. The principal goal should be to develop a single set of emission and basic EMC test standards that can be used by all manufacturers. In addition, the application of IEC Guide 107 within ISO and the ITU would improve the consistency of EMC standards generated by all three organizations.

Anticipation of New Technologies. A second approach is for EMC engineers and scientists to evaluate emerging technologies that may have EMC impacts, including reviewing the popular and scientific literature as new ideas are formulated. When necessary, standards-review groups such as IEC's EMC advisory committee should organize meetings or seminars to uncover potential conflicts of operation. And companies pursuing the development of innovative technologies should be encouraged to contact standards bodies for advice on how to minimize interference with other systems that might be caused by their new products.

Standardized Tests for High Frequencies. Another productive area might be the development of standardized test methods for higher-frequency disturbances, i.e., those above 1 GHz. Work to fully develop the reverberation test method, the transverse electromagnetic (TEM) test cell method, and ancillary standards for sensor calibrations should go forward rapidly. Current IEC efforts here need to be accelerated to be responsive to the rapid development of new products.

EM Disturbances and Functional Safety. More attention should be paid to the complex functional problems caused by electromagnetic disturbances that may lead to a loss of safe operation.⁵ Although this may appear to be a classic safety problem, the ability of EM fields to interact, in a complex way, with systems that are exchanging electronic data in real time requires the attention of EMC experts. A key difficulty is that the points of entry of an EM disturbance may be widely distributed throughout a system. For this reason, traditional shielding against external influences and reliance on a strong EMC test program are necessary.

Testing Large Systems. With regard to the challenge of testing large systems and pieces of equipment, IEC and other standards organizations need to expend more resources to develop standardized procedures for the future. Some effort in this direction has already been made by those involved with testing to the high-altitude electromagnetic pulse (HEMP) environment. Because military electronic systems in the past were often very large, TEM and radiating simulators were built (see IEC 61000-4-32 for examples).⁶ Many of these simulators are available worldwide for testing objects that are transportable. Many of them also can be adapted to other waveforms and frequencies. Another option practiced by the HEMP community is to illuminate systems with low-level swept continuous-wave signals to measure transfer functions to potentially vulnerable points within a system. Testing options for HEMP and related radiated disturbances are described in IEC 61000-4-23.⁷

Creating Product EMC Standards. A new strategy is needed to address the translation of emission limits and basic EMC test standards into product EMC standards. IEC is organizing a group of reviewers to check the consistency of product standards with regard to their treatment of EMC. The objective of this approach is to find problems at an early stage of document drafting so that improvements in standards can be made without slowing down their development. Another proposal is to develop additional generic standards that minimize the need for product committees to adapt the EMC basic standards to specific applications. This approach could be successful whenever a product committee believes that a given generic-standard environment is appropriate for its equipment.

EM Protection Guidance. Although most standardization activity in IEC and other standards organizations is focused on test methods, substantial gains could be made if more effort were applied to EM protection methods. Proper EM shielding and cable filtering could go a long way toward solving many electromagnetic interference problems. One strategy would be to develop one general set of EM protection guides and a second set tailored to specific types of equipment. Of course, an obstacle to this approach could be its requirement for a significant contribution by EMC experts who are already in short supply, especially in the standardization arena.

Educational Forums. Another strategy for advancing understanding of the EMC problem is education through technical and standards-oriented workshops and seminars. The EMC Society of the Institute of Electrical and Electronics Engineers has done an excellent job of educating its membership with regard to the complexities of EMC compliance. IEC has recently initiated a series of workshops aimed at educating industry about the status and plans of its EMC standardization effort and hopes to continue them. Also, universities should be encouraged to offer courses in the field of EMC and to include instructors with industry backgrounds.

Industry Involvement. A productive step would be to educate industry about the importance of its participation in the development of international standards. It is clear that international trade will continue to expand in the future. Companies that help create new EMC standards will have an advantage over their competitors that do not, in that they will have a head start in developing compliant products. And without industry participation, the standards that are developed may be impractical with regard to test methods and the compliance costs.

IEC and its national committees continue to inform industry about the advantages of standardization. Incidentally, so-called prestandards can be developed rapidly from industrial specifications.

Finally, new modes must be found for financing standards development so that published standards can be distributed free or at low cost throughout the world. Qualified people clearly are needed to produce consistent and high-quality standards. The national committees of IEC are left to decide, therefore, how funding of standards activities can be revolutionized without sacrificing the quality of the work.

Present trends in the development of electronic products make it clear that devices of the future will produce, and must survive, a more complex electromagnetic environment. EMC engineers and scientists are urged to exert considerable and constant effort to ensure that adequate preparation is made for this electromagnetically dense prospect.