During the 1980s the worldwide interest in electromagnetic compatibility (EMC) grew rapidly with the introduction of legislation to control the growing interference problems generated by the increased use of electronic equipment in industry and in the home. The European directive harmonising EMC measurements gave particular impetus to manufacturers and importers of electrical and electronic equipment in Europe to understand EMC design techniques and verification procedures. This book explains how equipment can be verified by testing. It discusses the nature of EMC standards world wide and describes in detail testing methods and their conduct and accuracy. In addition to standard EMC testing, topics including electrostatic discharge, nuclear electromagnetic pulse and lightning are also discussed. In the broad span of its subject matter, the interests of equipment manufacturers, EMC test engineers, project managers and company administrators are addressed. The testing of both military and commercial electronic equipment is covered. Particular emphasis is placed on the nature of EMC test equipment and how to use it to make reliable measurements.
Inspec keywords: electromagnetic compatibility; product development; antenna testing
Other keywords: radiated emission testing; EMC testing; radiated susceptibility testing; antenna; electromagnetic compatibility; EMC standard; measurement equipment; uncertainty analysis
Subjects: Antennas; Project and production engineering; Electromagnetic compatibility and interference
Electromagnetic interference (EMI) can be viewed as a kind of environmental pollution which can have consequences that are comparable to toxic chemical pollution, vehicle exhaust emissions or other discharges into the environment. The electromagnetic spectrum is a natural resource which has been progressively tapped by man over the last 100 years. Most of the development has taken place in the last 50 years with the advent of public service broad casting, point-to-point and mobile communica tions etc. which has brought great economic and social benefits. The spectrum is now almost full and it is proving difficult to satisfy the pressures for new uses of this resource. Modern life has come to depend heavily on systems that use the electromagnetic spectrum and its protection is in the interests of us all. For this reason unwarranted electromagnetic interference represents a real economic and social threat which can even result in injury or death.
The task of developing standards for the control of EMC can be said to have begun in 1934 with the formation of CISPR [1]. The name CISPR is derived directly from the French, Comite International Special des Perturbations Radioelectriques, and was formed by several inter national organisations coming together to institute a joint committee to specify measurement methods and limits of radio frequency interference. Since 1950 CISPR has been a special committee under the sponsorship of the IEC (International Electrotechnical Committee) whose role is to issue international standards.
A key element in cost-effective EMC design and certification of a civil or military equipment or product is careful programme planning. The EMC aspects of the project must be considered at all stages and may require some design and cost compromises to be made. The particular solutions arrived at will of course be determined by specific project conditions, but it is vital that the existence and timing of decisions involving electromagnetic compatibility are known and as far as possible planned for.
This chapter concentrates on coupling devices used in conducted EMC testing, all the groups of sensors discussed in this book, including radiated emission and susceptibility antennas, are listed in this chapter to show the number of groups and to illustrate the range of sensors considered.
An overview of the important basic characteristics of antennas is presented to establish a framework of simple equations within which specific antenna types may be discussed further. Electromagnetic antenna theory is complex and rather mathematical and much has been written on the basic theory of antennas and the design of many specific antennas for communications use from HF to millimetric wavelengths. Emphasis of the chapter is on the practical aspects of antenna characteristics which EMC engineers and test technicians can use with a view to minimising potential measurement errors.
Antennas for radiation emission measurement are treated separately from antennas for radiated susceptibility testing to show the importance of different antenna parameters in the two cases. With antennas for emission measurements the key parameters are bandwidth, sensitivity, dynamic range and absence of cross or intermodulation products in the case of active antennas with built in amplifiers. Important parameters for antennas used in susceptibility measurements include bandwidth, gain/power requirement, beamwidth/ spot size, power dissipation, size and mass. Such topics arc discussed in the following chapter. This one looks in detail at the types of receiving antennas that are widely used for radiated emission testing. They are discussed in sequence, beginning with the passive monopole which has the least complicated construction.
The types of antenna commonly used for RF radiated susceptibility testing are treated separately from antennas used in emission measurements as the antenna parameters relating to reception and transmission are different.
This chapter discusses the types of electronic test equipment commonly used in EMC emission and immunity testing over the frequency range from a few hertz to tens of gigahertz.
This chapter examines the three principal test regimes and facilities in which these devices and equipments are used to conduct EMC tests: testing in screened chambers, open-range testing, and 'low-level swept' and bulk current injection testing. The majority of standard EMC test work carried out on commercial and military electronic equipment falls into one of these three regimes.
In this brief introduction to the nature of transients and disturbance to power distribution systems it has only been possible to acquaint the reader with the broad categories of effects and show some examples of applicable standards and specifications. With the fast growing implementation of digital microprocessors into industrial, commercial and domestic equipment this area of electromagnetic compatibility is becoming very much more important than it has been in the past. Consequently, EMC design and test engineers must be aware of this somewhat overlooked aspect of electromagnetic interference engineering, and not allow an otherwise compatible equipment to be compromised by these conducted transients and other power line phenomena.
This chapter is concerned with the EMC testing. The repeatability of EMC testing depends on many factors that affect the measurement result. Some factors are not well understood or not documented in terms of the nature and magnitude of their contributions to the total uncertainty. The treatment of measurement uncertainty involves the use of statistics to estimate the probable uncertainty and associated confidence level with regard to a particular measurement or set of measurements. Statistics and probability theory is a considerable subject in its own right and far too large to deal with adequately in a book such as this, which is primarily concerned with the varied aspects of EMC testing.
This chapter is concerned primarily with EMC testing; the higher level aspects of product or system design to meet EMC requirements have been discussed in some detail so that the reader can appreciate the nature of the overall EMC design task. This clearly involves more than specifying a mains filter connector, fitting a few chip capacitors on a PC board, or spraying the inside of the plastic equipment case with metal. It is not the intention to detail all the techniques mentioned for achieving good EMC or to give the basic formulas that would be needed to enable a design.
Electromagnetic compatibility is a fascinating and rapidly developing field of electrical engineering. It poses important, interesting and wide ranging multidisciplinary challenges to equipment designers. It affords many technical challenges which must be met by engineers, to make consistent and meaningful measurements of complex EMI quantities. The management and quality aspects of EMC work are equally important if the technical effort expended is to be realised in terms of added value to the products being developed.
This appendix to the book covers signal bandwidth, UK EMC legislation, European EMC standards, US EMC regulations, electrical safety, electromagnetic radiation safety, military EMC standards, NAMAS-accredited laboratories, and EMC consultancy.
This appendix gives the MIL STD 462 (N3) and DEF STAN 59-41 modulation rules.
The appendix to the book covers signal bandwidth, UK EMC legislation, European EMC standards, US EMC regulations, electrical safety, electromagnetic radiation safety, NAMAS-accredited laboratory, and EMC consultancy.