Title: PCB Design for Real-World
EMI Control
Author: Bruce R. Archambeault with contributions
by James L. Drewniak
Publisher: Springer
ISBN: 978-1-4020-7130-0
When I first read the table of contents for
this book – I saw a number of chapters that seemed interesting
– and then when I saw the title of Chapter 4, “The
Ground Myth”, knew I had to have a copy! I wondered, what
kind of book is this that the author would make this type of statement?
After I received my copy, I then realized that this was not “just
another” EMC book on printed circuit boards (PCB); this
was a PCB book about EMC.
This book is intended for the engineer or designer that has had
a background in the fundamentals of EMC, component and system
design, and it discusses the impact of the “real world”,
where time and schedule pressures are sometimes allocated a higher
priority over EMC. Interestingly, the title itself, with its use
of the phrase “Real-World” seems also to generate
interest from people who do not have a background in EMC, all
they know is that it’s important (for some reason).
The book is comprised of 13 chapters, and one appendix, with each
addressing a different aspect of how to meet EMI requirements.
The content of each chapter and appendix are as follows:
Chapter 1, “Introduction to EMI/EMC Design for Printed Circuit
Boards” gives the “50,000 foot” overview of
the major items that are important when products are identified
to have applicable EMC requirements. This chapter also effectively
“sets the stage” for the detailed discussions in the
remaining chapters.
Chapter 2, “EMC Fundamentals” addresses specific themes
in EMC fundamentals, and relates those themes directly to printed
circuit board design. The key concepts are introduced: signal
spectra, electric and magnetic fields, and why knowledge of PCBs
is important. There is also an overview of what some of the potential
emission sources are and what their causes are.
Chapter 3, “What is Inductance?” seems to be a question
that many people assume they know; for example, they have been
taught to believe a straight piece of wire has some property of
“inductance” – without an understanding of what
this statement really means. This chapter covers the topic in
a manner that working engineers will find valuable and the equations
included illustrate the correct physical principles very well.
This chapter is useful for determination of inductance of long
wires and/or conductors that are not typically thought of to have
inductance – since they don’t “look” like
inductors.
Chapter 4, “The Ground Myth”, in my opinion, even
if the rest of the chapters were blank – this chapter alone
would be worth having the book. If you want to get puzzled looks
from people – show them the title of this chapter! The reader
will find themselves reading this chapter again and again to fully
understand the implications of this MAJOR PARADIGM SHIFT IN THINKING!
Chapter 5, “Return Current Design” is another area
that causes much confusion with the design of PCBs. This chapter,
when coupled with the points from chapter 4, provides insight
into how critical it is to understand that the return current
on a PCB can be unknowingly affected by some the existing “best
practices” that are used for layouts of reference planes
and interconnection of PCBs.
Chapter 6, “Controlling EMI Sources – Intentional
Signals” is an easy to read chapter on the fundamentals
of how the intended signals on a PCB can result in EMI issues.
The items in this chapter give the engineer/designer insight into
the major issues that should be of primary importance when a PCB
is being designed, and can provide guidance on initial design
practices.
Chapter 7, “Controlling EMI Sources – Unintentional
Signals” introduces the concept that the “unintended
signals” on a PCB can have a major effect on the ability
to meet EMI requirements. These unintended signals can be due
to deficiencies in understanding the “grounding” concepts
that apply AND DO NOT APPLY, as well as the phenomenon of crosstalk
on an actual board, and how that condition may cause EMI compliance
issues.
Chapter 8, “Decoupling Power/Ground Planes” addresses
the common practice of the rule-of-thumb for decoupling –
“just use a bunch of 0.1 mF capacitors and everything will
be fine.” This chapter demonstrates how, as a minimum, that
rule of thumb may be misleading, and at a worst case, can actually
result in a degraded performance than if the decoupling capacitors
were not used at all! This chapter clearly shows the author’s
experience in real-world decoupling issues.
Chapter 9 addresses “EMC Filter Design”. With the
advances in digital signal processing, it seems like much of the
fundamentals of filtering techniques have been “put on the
back shelf.” This chapter describes how to design filters
for effective EMI control and also includes the important aspects
of how filter performance is affected by “non-ideal”
component characteristics.
Chapter 10, “Using Signal Integrity Tools for EMC Analysis”
is a useful topic since the operating speeds of today’s
digital devices are ever-increasing, the signal rise/fall times
are decreasing, and it means that the fundamentals of EMI analysis
become applicable for the study of signal integrity. The chapter
contains a number of figures that illustrate how important it
is to understand the actual impedance of high speed circuitry
and how EMI analysis techniques can help to identify how the system
is actually functioning – which may be different from what
the engineer believes!
Chapter 11, “Printed Circuit Board Layout” is a continuation
of some of the topics that were introduced in chapter 8. This
chapter is a “must read” for all who have been taught
to focus on the circuit design (such as component selection only)
and typically are never made aware of the ability of the PCB to
“make or break” the EMI compliance of the design.
There is a good discussion of how to allocate PCB board layers,
from simple one and two layer boards to the more common six layer
designs.
Chapter 12, “Shielding in Enclosures with Apertures”
addresses the fact that, sometimes, despite the best intentions
of designers and engineers, the only method to achieve EMI compliance
may be through the use of shielding. Unfortunately, there seems
to be much confusion with regard to what shielding is and is not
(for example, what is a “good shield”?). This chapter
explains how knowledge of current flow can be used to understand
and determine the correct shielding solution to use, and provides
basic equations to determine the effectiveness of those solutions.
Chapter 13, “What To Do if a Product Fails in the EMC Lab”
should catch the eye of those immersed in the “real world”
of EMC. Key to developing any EMI solution is understanding the
performance of a design. This chapter contains a number of tips
as to what steps to take in identifying the source of the problems
– which at that point will then allow the engineer to re-visit
the other chapters in the book to determine effective solutions.
Appendix A, “Introduction to EMI/EMC Computational Modeling”.
Given Dr. Archambeault’s work in EMC/EMI modeling, it is
not surprising to see an introduction to modeling in this book.
This appendix does an effective job of “de-mystifying”
this complex topic and should serve to help engineers in understanding
what basic approaches are used in modeling and the value of those
techniques.
The positive aspects of this book are:
- Numerous examples in real PCB design to emphasize the points.
- The chapters can be read on an “as needed” basis;
as the engineer/designer is working on a project, they can quickly
go to a specific chapter and topic as a resource.
- Easy to read figures and illustrations.
Items that don’t work as well include:
- Significant variation in the number of chapter references –
some chapters have many references, others very few, and the reader
is left wondering if chapters with few references are based on
other material, or is the author’s opinion.
- Additional background with regard to many of the equations would
provide the reader with a better understanding and insight at
times.
- There are a number of editorial issues (such as typographical
and/or formatting) that seem like they should have been caught
in the proofreading process.
Overall – I have found this book to be a useful addition
to my personal library and have used it both in my EMC product
engineering work and identified some of its key points to my past
students. I would definitely recommend this book!Mark Steffka,
B.S.E., M.S., is with the Electromagnetic Compatibility (EMC)
Engineering Group of General Motors (GM) Powertrain and is a faculty
member of two universities in the Detroit area. He has over 25
years of experience in the design, development, and testing of
military, aerospace and automotive electronics, including power,
control, and radio frequency (RF) systems. As an adjunct lecturer
at the University of Michigan – Dearborn, and an adjunct
professor at the University of Detroit – Mercy, he teaches
both undergraduate and graduate level courses on EMC, communications,
and antennas. He is a member of the Institute of Electrical and
Electronics Engineers (IEEE), has served as an invited session
chair for the IEEE EMC Symposium and is the Technical Program
Co-Chair for the 2008 IEEE International Symposium on EMC. He
has also been a technical session organizer for the Society of
Automotive Engineers (SAE) World Congress and has been an invited
speaker at IEEE and SAE conferences held in the United States
and international locations. His technical publications and presentations
have covered topics on EMC, RFI, and he is a co-author of the
book Automotive Electromagnetic Compatibility. The paper he presented
at the 2007 SAE World Congress titled “Engine Component
Effects on Spark-Ignition Caused Radio Frequency Interference
(RFI)” was “Judged to be among the most outstanding
SAE technical papers of 2007.” He has held an amateur radio
license since 1975, with the call sign WW8MS, is a Life Member
of ARRL, the National Association for Amateur Radio, and serves
on the ARRL EMC Committee. EMC
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