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Embracing a New Outlook for the Future of EMC
Peter J. Kerry |
The chairman of CISPR shares his views on how and why the criteria
for EMC of the last
century is not sufficient for the new one.
Q. Why do you believe that
the EMC criteria of the last century are not sufficient for the
future?
A. CISPR has its origins in the 1930s when the
major concern was the protection of AM radio broadcast services.
This early work has served us well, and has successfully evolved
to cope with the protection of FM radio and traditional television
broadcasting services. However, the more recent technological
developments are in a different category. In particular, digital
radio and television services need different protection criteria,
and new standards need to be developed to account for these changes.
Equally important, digital technology uses switching rates
in the radio frequency range, which leads to new compatibility
issues that will need to be considered. For example, the challenge
of ensuring that high-speed data networks are protected from amateur
radio transmissions has been highlighted in a recent European
Telecommunications Standards Institute (ETSI) report.
In addition, the frequency range of radio services needing
protection is increasing. Testing at frequencies above 1 GHz can
be time consuming, and the open-area test site (OATS) was not
designed for this. A further difficulty is that the radio spectrum
is being used more intensively; consequently, it is becoming difficult
to find quiet areas for the traditional OATS emission measurements.
Hence, there is a need for the development of new measuring techniques.
A further example is the use of the quasi-peak (QP) detector
for emission measurements. It was developed to simulate the audible
impact of interference to AM broadcast services. We are now in
an age of automatic testing, where not only are QP measurements
slowing the process, but AM broadcasting is now only a small part
of the services we need to protect. There is a need to review
the use of the QP detector, not only for the benefit of radio
users, but also to try to reduce the cost burden to industry.
These are the major issues that indicate that while our
predecessors have done good work that has stood the test of time,
now is a time to look afresh at what is really needed for the
coming years.
Q. What do you view as
the most significant milestone in the history of EMC?
A. The banning of the spark transmitter was probably
the first significant step in improving EMC; however, the impact
of the EMC Directive has been much wider than this.
One of the driving factors behind the EMC Directive was
the removal of technical barriers to trade within the European
Union so that there were common requirements throughout the member
countries. This has created a very large trading block with common
EMC requirements. Many other countries have done something similar.
Consequently, the IEC standards for EMC are increasingly being
used for regulatory purposes throughout the world.
The EMC Directive was also unique in recognizing that immunity
requirements were as important as emission. I recognize that this
was a controversial decision, but it has raised the profile of
EMC immunity and should reduce the number of interference complaints
being recorded. Interference complaints are attributable most
often either to poor immunity performance or to poor installation
quality. While the immunity issue has been addressed, the issue
of installation quality is one of the major challenges yet to
be resolved.
The time available to develop the necessary standards for
the directive was limited, and in order to meet the deadlines,
the four generic standards were developed. These now serve as
reference standards against which new EMC standards are compared,
changing the focus from "what the product can easily meet" to
"what is needed to protect radio services and the power network."
Q. How can industry designers
take into account the new and evolving radio services?
A. This question occupied my mind for a long
time when I first took over as chair of CISPR. CISPR is unique
in the International Electrotechnical Commission (IEC) in that
it comprises not only national committees, but also key radio
organizations such as the International Telecommunication Union
Radiocommunication Sector (ITU-R), Civil Aviation Authority (CAA),
European Broadcasting Union (EBU), and more recently ETSI. However,
the CISPR structure was ineffective in allowing these organizations
to be heard, and they had long ceased shouting when I came on
the scene. Consequently the standards being developed were not
taking into account new radio services.
Peter J. Kerry has been with the Radiocommunications Agency
and its predecessors for some 30 years. During this period, he
has been involved with a wide range of radio systems. For the
past decade, he has been responsible for EMC standardization and
is currently the chairman of the international EMC standardization
committee (CISPR). The Radiocommunications Agency is an executive
agency of the UK's Department of Trade and Industry and is responsible
for the radio spectrum in the UK. Kerry spoke with senior editor
Sherrie Steward about his perspectives on EMC and the new challenges
for CISPR and the industry.
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