Designing Electronic Systems for EMC

306 Pages·2011·21.93 MB·English

by  William G. Duff

The SCiTeCh SerieS on eleCTromagneTiC CompaTibiliTy
alistair Duffy, phD - editor
DESIGNING ELECTRONIC
SYSTEMS FOR EMC

DESIGNING ELECTRONIC
SYSTEMS FOR EMC
William G. Duff
B Scr
PPUUBBLLIISSHING, INC
PUBLISHlNGrTINC.
Published by SciTech Publishing, Inc.
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Editor: Dudley R. Kay
Editorial Assistant: Katie Janelle
Production Manager: Robert Lawless
Typesetting: J. K. Eckert & Company, Inc.
Cover Design: Brent Beckley
Printer: Sheridan Books, Inc., Chelsea, MI
Printed in the United States of America
10 987654321
ISBN: 978-1-891121-42-5
Library of Congress Cataloging-in-Publication Data
Duff, William G.
Designing electronic systems for EMC / William G. Duff.
p. cm.
Includes bibliographical references.
ISBN 978-1-891121-42-5 (hardcover : alk. paper)
1. Electromagnetic compatibility. 2. Electromagnetic interference. I. Title.
TK7867.2.D84 2011
621.381-dc22
2011004765
This book is dedicated to a very special "lady " in my life—
my wife Sandi Her love and encouragement inspired and
motivated me to start writing this book Her patience and
understanding helped me to complete the task
No one knows better than an authors wife how much time
and effort is required to complete a book such as this.
Thank you, Sandi, for always being there when I needed
encouragement and support.

Contents
Preface ix
Acknowledgment xi
Some EMC-Related and Metric Terms and Acronyms xiii
Common Terms and Abbreviations in EMC Literature xvii
Military EMI/EMC Standards xxiii
Chapter 1—Introduction to Electronic System Design for EMC 1
1.1 Effects of EMI 3
1.2 Sources of EMI 4
1.3 Modes of Coupling 5
1.4 Susceptible Equipments 6
1.5 EMC Design Consideration vs. System Life Cycle 6
1.5.1 System Definition Phase 8
1.5.2 System Design and Development 9
1.5.3 System Operation 10
1.6 Overview of Handbook 10
Suggested Readings: EMI/EMC 11
Chapter 2—Basic Terms and Definitions 13
2.1 Decibels 13
2.2 EMI Conducted Terminology 14
2.3 EMI Radiated Terminology 14
2.4 Representation of Signals in the Time and Frequency Domains.... 14
2.4.1 Fourier Series 15
2.4.2 Fourier Transform 16
2.4.3 Spectral Representation 16
2.5 Transients 18
2.5.1 Transient Sources 19
2.6 Narrowband Emissions 20
2.7 Broadband Emissions 21
2.7.1 Incoherent Broadband Emission 22
2.8 Frequency and Wavelength 22
2.9 Units of Measure for EMI Signals 23
Suggested Readings: Basic Terms and Definitions 24
Vll
viii DESIGNING ELECTRONIC SYSTEMS FOR EMC
Chapter 3—Communication Systems EMC 25
3.1 Communication System EMI Problems 26
3.2 EMI Interactions between Transmitters and Receivers 26
3.3 EMC Design of Communication Systems 28
3.4 Transmitter Emission Characteristics 34
3.4.1 Fundamental Emissions 35
3.4.2 Transmitter Intermodulation 37
3.4.3 Harmonic Emission Levels 39
3.5 Receiver Susceptibility Characteristics 40
3.5.1 Co-channel Interference 41
3.5.2 Receiver Adjacent-Signal Interference 42
3.5.3 Receiver Spurious Responses 47
3.6 Antenna Radiation Characteristics .48
3.6.1 Design Frequency and Polarization 50
3.6.2 Polarization Dependence 50
3.6.3 Nondesign Frequencies 50
3.7 Propagation Effects 51
3.8 Sample EMC Assessment 52
3.8.1 Transmitter Noise 52
3.8.2 Intermodulation 54
3.8.3 Out-of-BandEMI 57
3.9 Computer EMC Analysis 60
Suggested Readings: Communication Systems EMC 60
Chapter 4—Electronic System Design for EMC 61
4.1 Basic Elements of EMI Problems 61
4.1.1 Sources of EMI 63
4.1.2 EMI Modes of Coupling 66
4.1.3 Susceptible Equipments 74
4.2 System-Level EMI Control 76
Suggested Readings: Electronic System Design for EMC 80
Chapter 5—Grounding for the Control of EMI 81
5.1 Definitions 82
5.2 Characteristics of Grounding Systems 83
5.2.1 Impedance Characteristics 83
5.2.2 Antenna Characteristics 90
5.3 Ground-Related Interference 91
5.4 Circuit, Equipment, and System Grounding. 94
5.4.1 Single-Point Grounding Scheme 96
5.4.2 Multipoint Grounding Scheme 97
5.4.3 Selection of a Grounding Scheme 98
5.5 Ground System Configurations 103
CONTENTS ix
5.6 EMI Control Devices and Techniques 109
Suggested Readings: Grounding 110
Chapter 6—Shielding Theory, Materials, and Protection
Techniques Ill
6.1 Field Theory Ill
6.2 Shielding Theory 113
6.2.1 Absorption Loss 116
6.2.2 Reflection Loss 117
6.2.3 Reflection Loss to Plane Waves 118
6.2.4 Reflection Loss to Electric and Magnetic Fields 119
6.2.5 Composite Absorption and Reflection Loss 122
6.3 Shielding Materials 123
6.4 EMI Shield Compartments and Equipments 125
6.5 Shielding Integrity Protection 127
6.5.1 Integrity of Shielding Configurations 128
6.5.2 EMC Gaskets 142
6.5.3 EMC Sealants 155
6.5.4 Conductive Grease 157
Recommended Readings: EMI Shielding 158
Web Addresses for EMI Shielding 159
Chapter 7—Bonding 161
7.1 Effects of Poor Bonds 161
7.2 Bond Equivalent Circuits, Resistance, and Impedance 162
7.3 Direct Bonds 163
7.3.1 Screws and Bolts 163
7.3.2 Soft Solder 164
7.3.3 Brazing 165
7.3.4 Welding 165
7.3.5 Cadweld Joints 165
7.3.6 Conductive Adhesive, Caulking, and Grease 165
7.3.7 Bonding of Composite Materials and Conductive Plastics ... 166
7.4 Indirect Bonds 167
7.4.1 Jumpers and Bond Straps 168
7.5 Corrosion and Its Control 169
7.5.1 Galvanic Corrosion 169
7.5.2 Electrolytic Corrosion 170
7.5.3 Finishes 170
7.5.4 Corrosion Protection 172
7.6 Equipment Bonding Practices 172
7.7 Summary of Bonding Principles 177
Suggested Readings: Bonding 178