In the past two decades, unintentional electromagnetic radiation from modem electronic systems has become increasingly difficult to control. Digital electronic systems are the primary sources of the problem, and their presence is rapidly becoming an omnipresence. And, a growing recognition of the problem of unintentional electromagnetic radiation has resulted in increasingly strict regulations to control it. However, effective control requires extensive understanding, and digital engineers are seldom extensively schooled in electromagnetic radiation. Furthermore, existing texts and references are directed, for the most part, toward increasing and enhancing electromagnetic radiation, rather than reducing it. Therefore, those texts and references do not provide direct access to the understanding of the problem that is needed by digital designers and other engineers. It is the purpose of this book to fill that need—to provide direct access to basic concepts that must be understood to control unintentional electromagnetic radiation effectively.

The book is organized as follows. Chapter 1 is a brief, general introduction to the primary causes of electromagnetic radiation and to other topics discussed in the remainder of the book. Chapter 2 is a basic examination of intentional electromagnetic radiators, which is included as background for better understanding unintentional radiation. Chapter 3 is a basic examination of the electromagnetic radiation of electrical circuits and how it can be modeled. In Chapter 4, a relatively simple method for decomposing many often-used, periodic voltage waveshapes into their sinusoidal components is developed for use in subsequent chapters. In Chapter 5, useful, easily obtainable descriptions of the measured radiations of periodic, time-varying circuit currents are developed. Chapter 6 contains a discussion of basic methods for controlling the unintentional radiations of electrical circuits based on the models developed and observations made in previous chapters. Chapter 7 is an examination of containment of electromagnetic radiations as a secondary method of control. And, Chapter 8 is an examination of the measurement process with which the effectiveness of controlling unintentional radiations is evaluated.

This book has evolved from seminars presented by the author while a member of the technical staff of Hewlett-Packard Company from 1974 until 1990, and, more recently, as a semi-retired lecturer and consultant. Those seminars and this book were developed for general consumption by anyone with a general engineering background. The book is not a detailed catalogue of solutions—it is intended to generate wider understanding and to lead to more effective solutions of a problem that has a definite and growing need for both.


This book consists of generally informative discussions about unintentional electromagnetic radiations and how to control them in the design phase of the manufacture of electronic devices. It is written so that technicians, designers, and managers, or specialists in areas other than electromagnetic compatibility who want basic facts can get them. It is also written for those readers who need a deeper understanding of the underlying physics and the basic mathematics of the problem.

Readers who want basic facts about unintentional electromagnetic radiation and its minimization and control should read Chapter 1; the introductions and summaries of Chapters 2, 3, 4, and 5; and Chapters 6, 7, and 8. Those sections and Chapters 1, 6, 7, and 8 taken alone have been written to form a less mathematically detailed, condensed version of the book.

Those readers who are interested in further background material and foundational discussions should read more of Chapters 2, 3, 4, and 5 than suggested above. And those readers who want to thoroughly absorb its contents should, of course, read the whole book, including the appendices, and any references of interest to them.

Algebra and basic trigonometry are the only mathematics used throughout the book. Other mathematics, when necessary, are either relegated to the appendices, or referenced in the bibliography.


Loveland, Colorado

September 1996

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