The ability to design and achieve electromagnetic compatibility is becoming more challenging with the rapid development of new electronic products and technologies.  This paper reviews the definition and status of EMC today, discusses the near term trends that have appeared, and proposes strategies to solve the EMC problems of the future.

1. INTRODUCTION

 

This paper addresses four questions of importance today and in the future with respect to the problem of Electromagnetic Compatibility (EMC) of electronic systems:

 

--     What is EMC?

--     What is the status of EMC today?

--    What are the EMC problems of the (near) future?

--    What is our strategy to solve these EMC problems?

 

As the author is the Chairman of the International Electrotechnical Commission (IEC) advisory committee on electromagnetic compatibility (ACEC), most of this paper will focus on the activities of the IEC.  The IEC has been very active in developing new and improved EMC standards over the past 10 years.

 

 

2. What is Electromagnetic Compatibility (EMC)?

 

As most workers in the field understand, electromagnetic compatibility describes a state when the electromagnetic environments produced by natural phenomena and other electrical and electronic devices do not cause interference in electronic equipment and systems.  Of course to reach this state, it is necessary to reduce the emissions from sources that are controllable, 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.  Rather, it is recognized that emissions from various sources are variable (e.g. lightning impulses on power lines 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 (e.g. induced voltages on a circuit board are strong functions of the angle of incidence and polarization of the incident EM field).  This variability results in a situation where a balance is found between immunity and emissions for a particular type of disturbance to prevent problems in a large percentage (but not all) of the cases of interest.  To try to eliminate all problems (by decreasing emissions and increasing immunity further) could create a high cost to industry and could prevent new technologies from emerging.

 

For example a restriction to lower the transmitting power of cell phones so that consumers could lay their cell phones on top of any piece of electronic equipment could compromise the performance and economic viability of cell phone systems.  On the other hand, a requirement that all commercial electronic equipment perform without malfunction at levels of 50 V/m, would place a financial burden on a large range of equipment.  A good compromise is to warn consumers of reasonable restrictions, although special actions may be necessary when malfunctions could cause a threat to human safety.

 

 

3. What is the status of EMC today?

 

3.1. Overview

 

The focus of today's work in EMC is clearly on standardization -- especially in international organizations.  The requirements of the World Trade Organization and the desire to reduce worldwide trade barriers have resulted in a strong emphasis on international standards.  Of course it is clear that regional developments, such as the European Directive on EMC, has had a strong influence on the pace of work.

 

In terms of the international standards bodies, the majority of the EMC standardization work is occurring in the International Electrotechnical Commission (IEC), while significant segments of work are also occurring in the International Standards Organization (ISO), and the International Telecommunications Union (ITU).

 

The IEC and its two principal horizontal EMC committees, CISPR and TC 77, have developed, and are continuing to develop, a significant range of basic EMC standards that define the measurement and test methods necessary for repeatable standards.  In the area of emissions, CISPR and SC 77A are also developing emission limits for high–frequency electromagnetic fields and low-frequency power line disturbances, respectively.  Within the IEC, ACEC coordinates the EMC work and also coordinates with other standards bodies to reduce duplication in the marketplace.

 

The ISO and the ITU are working in their respective areas to develop standards dealing mainly with moving vehicles and communication systems, respectively.  In particular, the ISO is actively working with automotive, aircraft and space EMC standards.  ITU deals with the EMC aspects of emerging telecommunications equipment including both radio and "wired" technologies.  Both organizations are coordinating their work with the IEC in the hopes of minimizing the number of basic EMC standards that are developed so that industry will not be required to test and certify their equipment to conflicting standards.

 

One important aspect of the development of international standards is that they are voluntary in nature, although they may be applied in commercial contracts or by regional standards organizations in a mandatory fashion.

 

3.2. The IEC EMC Approach

 

As alluded to above, the IEC has focused its EMC standardization work into four main categories.  These include the development of:

 

--     emission limits for all products;

--    basic EMC standards that include test and measurement methods for emissions and immunity;

--    generic EMC standards that specify a set of "essential" disturbances, test methods and test levels appropriate for an environment class (e.g. residential) for both emissions and immunity; and

--    product EMC standards that are tailored either to a class of equipment in a product family standard or to a specific type of equipment in a product standard (these standards usually include both emissions and immunity clauses).

 

Within the IEC, the EMC work is coordinated in the Advisory Committee on Electromagnetic Compatibility (ACEC).  In addition, IEC Guide 107 [1], which has been developed by ACEC, provides guidance to IEC committees on how to properly develop EMC standards and reports.  To accomplish its work, ACEC meets two to three times a year to consider new developments in EMC standardization within and outside of the IEC.  The committee consists of technical experts in the field of EMC and representatives of the major participants in the development of basic and product EMC standards.  ACEC provides its recommendations to the IEC Committee of Action for their consideration after every meeting.

 

3.3. Status of Important EMC Issues

 

One of the major problems today within the standardization process is the translation of emission limits and basic standards into product standards.  Although considerable effort has been made to establish high–frequency emission limits by CISPR, there have been several cases in product standards were the limits were ignored or improperly applied.  Unfortunately these errors are not always found until after a product standard is published, and it may take years to correct the error.  ACEC is developing a new procedure to solve this problem by tracking the development of product standards to try to improve the accuracy of EMC clauses.

 

A relatively new area of concern involves the generation of power frequency harmonics by electronic equipment.  Due to the large number of new electronic equipment with switched-mode power supplies, these harmonics can be significant enough to propagate within the power network and cause interference to other consumer-owned equipment.  Work is ongoing to develop standards that balance the needs of electronic manufacturers and the power utilities; however, progress has been slow.

 

Another area of concern involves the need to develop basic test methods that are applicable to test frequencies above 1 GHz.  This is a real concern due to the development of more and more commercial products operating at higher frequencies.  New test methods such as the reverberation chamber have advantages at higher frequencies in terms of better coverage of angles of incidence and polarization while reducing test time.  The IEC is working to develop a basic standard, 61000-4-21 [2], that will provide an option to those interested in an alternative test method.

 

 

4. What are the EMC problems of the (near) future?

 

Several important trends in technology are underway today that are likely to continue in the future.  The most obvious is the increase in the density of microprocessors in homes, businesses, factories and vehicles.  For the sake of clarity, this discussion will be separated into two parts -- fixed and mobile microprocessors.

 

In the area of fixed microprocessors, it is clear that many of our electrical appliances are becoming "smart" with the addition of microprocessors.  It is now possible to buy a refrigerator that has a built in computer.  There are plans to develop this appliance to the point that it will know when the last bottle of mustard has been used, and it will order a replacement for you through the Internet.  Although this may not seem to be a problem, if one considers that EMC is based, in part, on physical distances between emitters and "victims", the fact that there will be many more emitters and "victims" in the same space, 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 a large number of mobile transmitters are introduced into a fixed space?  Of course there is the cell phone which will continue to develop as it passes from one generation to the next.  However, there is now the possibility of a new set of transmitters that could be placed in nearly every piece of electronics -- Bluetooth technology.  Bluetooth is a specification for a frequency-hopping radio technology that uses the unregulated 2.4 GHz ISM band to communicate automatically between electronic devices within a range of approximately 30 meters.  The operational specification for Bluetooth has now been accepted by over 1200 companies worldwide, and it is projected that 400 million devices will be 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 without interference.

 

Another aspect of future problems is the continual increase in the frequency of operation of new products.  While cell phone technology has extended above 1 GHz and Bluetooth will operate at 2.4 GHz, there are other products involving satellite communication near 10 GHz and automobile radars operating above 40 GHz.  While new frequencies in themselves are not necessarily a concern, one particular aspect of this increase could be a problem.  In particular, higher frequencies have smaller wavelengths and are able to penetrate equipment enclosure seams and apertures more easily than lower frequencies.  For instance, the wavelength of 100 MHz is 3 meters, 1 GHz is 30 cm and 10 GHz is 3 cm.  For a 2-cm long seam 1-mm wide in a metal enclosure, the attenuation of each these fields 3 cm behind the aperture is 79, 59, and 39 dB, respectively.  In addition to this increase in the disturbing environment with increasing frequency, the development of new microprocessors operating at clock speeds of 1 GHz today allows the possibility of more direct interference in the operation of electronic systems from both an immunity and an emissions point of view.

 

The EMC standardization process has been very good in producing test methods to evaluate the acceptability of equipment and small systems built by manufacturers.  On the other hand, it has been difficult to develop standard methods to evaluate the immunity of large equipment or systems that are installed together for the first time.  Size is a very important factor since test facilities are expensive to build, and immunity testing in the open field requires large test generators and produces "threats" to other equipment that are not under test.  Even in the case of emissions testing, it can be difficult to establish the level of emissions from a particular piece of equipment after it has been installed in an operating factory.

 

Another new area of concern deals with safety aspects of electromagnetic fields; there are at least two areas in which this applies.  The first is the so-called area of EMF (a very poor acronym for electromagnetic fields, which in this case implies the concern of EM fields on the health of humans).  Most recently, EMF activities at ICNIRP (International Commission on Non-Ionizing Radiation Policy) and the WHO (World Health Organization) have resulted in an initiative in the IEC to support those organizations by developing measurement standards.  Mr. Goldberg was the chairman of these IEC coordination activities and will review this work in this conference and proceedings [4].  A second related area of interest is the possibility of electromagnetic disturbances causing electronic systems to malfunction and cause a safety risk (for example a cell phone in a factory causing an industrial robot to injure a worker).  Again the IEC is active in this area, and Mr. Goldberg also treats this subject in his paper [4].

 

In terms of the "structural" aspects of EMC standardization, several issues warrant mention.  In the EMC standardization process, as noted earlier in this paper, the balancing of the work to obtain EMC between the emitters (by reducing the emission limits) and the potential victims (by increasing the immunity levels), is a continual problem.  This process has been made more difficult due to the rapid change of technology and the very short time from product concept, to development, to production, and to the end of the product lifetime.  This results in a very short period of time for EMC standardization bodies to evaluate the impact of new technologies in order to maintain EMC.  When product cycles become shorter than the time required to develop a standard, a problem may occur.  In addition, when companies developing new electronic products and technologies do not participate in the standardization process, there is an increased likelihood of EMC conflict.

 

Finally, there are structural problems in the standardization process itself that are likely to create difficulties in the near future.  First there is the problem of the availability of EMC experts in all areas from product development to standardization.  Those involved in the discipline of electromagnetics know that fewer engineers are graduating with these credentials.  The competition and rewards in industry are for computer programmers and Internet experts.  Many who have worked in the field are nearing retirement, and some do not have the support of their management to work in the standardization field.  The second problem lies with the standardization bodies themselves.  With the digital revolution, everyone wants a digital copy of the latest standard.  Because of financial considerations, the IEC and their national committees need the funds from the sale of standards to keep their organizations operating.  The alternative is to charge the national committees a higher annual fee for the operation, but there is significant resistance to this idea.  In fact in the United States, reviewers of standards were recently asked to pay an annual fee to participate in the USNC; this resulted in a loss of participants who were volunteering their personal time to review EMC standards that are under development.

 

 

5. What is our strategy to solve these EMC problems?

 

One major strategy to solve the EMC problems of the future is to continue and even expand the focus of EMC standards within the IEC.  This effort should involve even closer cooperation with the ISO and the ITU in order to utilize limited EMC expert resources in the most efficient manner.  The major effort should be to develop a single set of emission and basic EMC test standards that can be used by manufacturers.  In addition, the application of the IEC Guide 107 within the ISO and ITU would improve the consistency of EMC standards in all three organizations.

 

A second strategy is for EMC engineers and scientists to evaluate emerging technologies that may have EMC impacts.  This includes the review of popular and scientific literature as new ideas are formulated.  When necessary, review groups such as ACEC in the IEC or other standardization bodies should organize meetings or seminars to learn of potential conflicts of operation.  Also companies involved in the development of new technologies should be encouraged to contact standards bodies for advice on how to minimize interference to other systems.

 

Another area for active work is the development of standardized test methods for higher frequency disturbances (above 1 GHz).  Work should proceed rapidly to fully develop the reverberation test method, the TEM test cell method and ancillary standards for sensor calibrations.  The current work in the IEC needs to be accelerated to respond to the rapid development in new products.

 

More attention should be focused on the complex functional problems caused by EM disturbances that may lead to a loss of safe operation.  While this may appear to be a classical safety problem, the ability of electromagnetic fields to interact in a complex way, with systems that are exchanging electronic data in real time, requires the attention of EMC experts.  One of the difficulties is that the points of entry of an EM disturbance may be widely distributed throughout a system.  For this reason a classical approach of shielding external influences and a reliance on a strong EMC test program are necessary.  Mr. Goldberg is the working group convenor on the IEC draft specification 61000–1–2 [5] that addresses many of these issues.

 

With regard to the problem of testing large systems and pieces of equipment, the IEC and other standards organizations need to expend more resources to develop standardized procedures for the future.  There has been some effort in this direction by those working with testing to the high-altitude electromagnetic pulse (HEMP) environment.  Because many military systems in the past were often very large, big TEM and radiating simulators were built (see the draft IEC 61000-4-32 [6] for examples).  Many of these simulators throughout the world are available for testing objects that are transportable.  Also many of these simulators can be adapted to other waveforms and frequencies.  Another option used by the HEMP community is to illuminate systems with low-level swept CW signals in order to measure transfer functions to potentially vulnerable points within a system.  These types of testing options are described in IEC 61000–4–23 [7].

 

Another strategy is needed with regard to the translation of emission limits and basic EMC test standards into product EMC standards.  One approach being planned within the IEC is to organize a group of reviewers to check the consistency of all product standards with regard to their treatment of EMC.  The objective is to find problems at an early stage in the document development so that improvements can be made without slowing down the development of the standards.  Another proposal is to develop additional generic standards that will minimize the need for product committees to translate the EMC basic standards to specific applications.  This approach could be successful if the product committees feel that the generic standard environments are appropriate for their equipment.

 

While most of the standardization effort in the IEC and other standard organizations is focused on test methods, substantial gains could be made if more effort was applied to EM protection methods.  Proper EM shielding and cable filtering could go a long way to solving many EMI problems.  One strategy would be to develop a general set of EM protection guides and a second set that is tailored to specific types of equipment.  Of course one difficulty  is that this approach would require significant effort by EMC experts who are already in short supply, especially in the standardization arena.

 

Another strategy for advancing understanding of this problem is through technical and standards workshops and seminars.  The IEEE EMC society is very active in this area and has done an excellent job in educating its membership with regard to the complexity of EMC compliance.  The IEC has recently initiated a series of workshops aimed at educating industry regarding the status and plans of EMC standardization within the IEC.  It is hoped that these workshops will continue in the future.  Also universities should be encouraged to offer courses in the EMC discipline, to include instructors from industry.

 

Another strategy of importance is to educate industry of the importance of participating in the development of international standards.  It is clear that international trade is here to stay and will continue to expand in the future.  Companies that are able to help develop new EMC standards will have an advantage with regard to their competition in that they will have a "head start" to develop compliant products.  Without the participation of industry, there is a possibility that the standards developed will not be practical with regard to the test methods and the costs of compliance.  The IEC and its national committees are always trying to educate industry to the advantages of standardization.  There are also new ways to develop "pre–standards" in a rapid way beginning with industry specifications.

 

Finally, new approaches must be found to finance the development of standards that will allow the low-cost (or free) distribution of standards throughout the world.  It is clear that a qualified staff is needed to produce consistent and high-quality standards.  It is therefore left to the national committees of the IEC to decide how these changes can be accomplished without sacrificing the quality of the work.

 

 

Back to library