Electromagnetic Compatibility – Methods, Analysis, Circuits, and Measurement, David Weston, CRC Press, 2017 (3rd edition)
While I’ve reviewed many books on EMC, this one by David A. Weston, is the most complete in coverage yet. The 1157-page book covers not only basic and advanced theory of EMC, but includes product design, commercial and military measurement techniques, and mitigation to obtain electromagnetic compatibility. The 12 chapters and six appendices are well-illustrated with numerous charts, graphs, and figures. It also includes ample case studies with solved example equations helping to illustrate the concepts.
According to the preface, 65% of the content is new or revised from the previous edition. The book is oriented towards product designers, system designers, or those performing EMC testing. I’d rate this as an advanced text, but with plenty of practical information on design and analysis methods to satisfy many different levels of experience. One important aspect is that many of the theoretical concepts are backed up by real measurements. Weston also provides free computer programs for various aspects of EMC. These program listings, written in Microsoft QuickBasic 3.0, are distributed throughout the book and are available for download via his web site, http://www.emcconsultinginc.com. It’s possible to modify the code slightly in order to convert these DOS-based programs to run in the Visual Basic Windows environment. A good article on how to perform the conversions may be found from Rowan University (NJ) here.
The book covers the typical sources of EMI with special attention to both radiated and conducted emissions, as well as susceptibility in various environments. There is a stronger focus on military applications, which many similar books lack – a very strong point of the book. Mitigations for these EMI and EMC issues are covered in depth. Many chapters, such as the one
on printed circuit boards have numerous experiments documented, showing the measured effects of various configurations. Each chapter includes detailed references.
Let’s walk through the chapters:
Chapter 1 covers basic EMC theory. It introduces electromagnetic interference, explains the various regulations (both military and commercial), and describes natural and man-made sources of interference in the environment. It then goes on to describe specific product families and environments, such as ISM (industrial, scientific, and medical), common noise sources, intentional emitters, low and high power intentional radiators, and conducted power line noise.
Chapter 2 is an introduction to electromagnetic fields, radiators, receptors (victim electronics), and antennas. Static and quasi-static fields are described, along with electric fields on wires and in free space. This is especially important when considering how electric fields propagate through PC boards. Simple E- and H-field antenna construction is described and finally E-field radiation exposure and limits are discussed.
Chapter 3 focuses in more detail on radiated and conducted emissions. Narrow band (harmonically related) and broadband (example is a DC-DC power supply case study) noise sources are described, along with detailed experimental measurements. Fourier analysis is touched on and the chapter finishes up with harmonic noise from transmitters.
Chapter 4 discusses coupling (crosstalk) between PC boards, cables, and wires. Capacitive and inductive crosstalk is described, along with combining these two concepts as several real examples are discussed.
Chapter 5 describes how electrical components behave at high frequencies and how they may be used to mitigate EMI. Power line and signal filter designs are described, along with emission mitigation techniques. The importance of decoupling capacitors is included. The last section describes the various external noise sources and mitigations (RF and transient, such as ESD and lightning, and others).
Chapter 6 is a lengthy section and covers shielding and gasketing. The classical far field shielding effectiveness (absorption, reflection) theory is described, along with some of the newer shielding techniques, such as conductive plastics, conductive paints and metal-filled cloth. Fortunately, Weston warns how the near field shielding effectiveness can differ from these far-field equations in the form of a warning and several experimental measurements. My own measurements in the near field (using a pair of near field probes transmitting and receiving) confirm this vastly different reading from that calculated with the classic far-field equations – a more realistic application for product shields, if you think about it. I’d refer interested readers to the recent article by George Kunkel in the 2016 EMI Shielding Guide, by Interference Technology. This is an important concept, because most EMC texts fail to mention this. The chapter wraps up with gasketing concepts and the effect of seams and other penetrations in shields.
Chapter 7 covers cable shielding and termination, one of the most common product design errors. It starts out with cable shielding effectiveness, the frequency dependency, and how to measure it. Shield termination is discussed and how poor terminations can affect EMI. Cable emission mitigations are covered, along with alternative cable shield terminations. Again, the emphasis is on military applications.
Chapter 8 covers grounding and bonding. The important difference between safety, signal and power grounds is described, as well as grounding for lightning and facility applications. The bonding section is also heavily military-related.
Chapter 9 is lengthy, as well, and covers EMI measurements, control requirements, and test methods. It starts out with test equipment and how to use to make both conventional EMI measurements and diagnostic (troubleshooting) measurements. Commercial standards for FCC, Canadian, German, Asian, Australia/New Zealand, and the European Union are covered. Not covered in this edition are the most recent updates to the EMC Directive (2014/30/EU) or the transition from the R&TTE Directive (1999/5/EC) to the Radio Equipment Directive (2014/53/EU). A major section covers the military and aerospace standards, MIL-STD 461F and
RTCA/DO-160. The various differences in MIL-STD-461 A through F are described, but the most recent version G is not covered. The latest information on the newest commercial and military EMC standards may be located on the Interference Technology website. Despite the lack of the most recent standards updates, this chapter is still pertinent enough.
Chapter 10 covers system EMC and antenna coupling. This chapter is heavily military-centric and describes both system EMC and antenna-to-antenna coupling of military systems. While some of the basic concepts may be applied to commercial systems and products, those working in the military and aerospace sectors will find the content more useful.
Chapter 11 describes printed circuit boards, why they can radiate, and how to mitigate emissions. Differential and common mode currents are described and how they can create radiated and conducted emissions. There are extensive experimental measurements of test circuit board configurations that’s interesting, with comparisons between microstrip and stripline. A good discussion of how gaps in ground return planes is discussed. Bonding and shielding of PC boards is also covered. The chapter wraps up discussing decoupling capacitors, embedded capacitance, and electrical band-gap techniques for reducing emissions, along with several case studies.
Chapter 12 is an interesting chapter, which includes several case studies on EMC control, prediction techniques, and describes several computer modeling software packages on the market.
There are six appendices, which cover the impedance of wires and cables, units and conversion factors, conversions between E-field, H-field, and power, common formulas, copper wire data, and permittivity of materials.
In summary, I would rank this text right up there with Clayton Paul’s, Introduction to Electromagnetic Compatibility (Wiley, 2006) or Henry Ott’s, Electromagnetic Compatibility Engineering (Wiley, 2009). While it covers the commercial EMC design world quite well, it should be especially useful for those working in the military and aerospace sectors. There’s some dated material included from past editions and I do wish the computer programs were available for download in the more up to date Visual Basic, but I still would give the book a “highly recommended” rating. Well done!
