Electromagnetic Compatibility Engineering. Henry W. Ott Henry Ott Consultants

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3 Electromagnetic Compatibility Engineering Henry W. Ott Henry Ott Consultants

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5 Electromagnetic Compatibility Engineering

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7 Electromagnetic Compatibility Engineering Henry W. Ott Henry Ott Consultants

8 Copyright r 2009 by John Wiley & Sons, Inc. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Daitvers, MA 01923, (978) , fax (978) , or on the web at Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) , fax (201) , or online at Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable fur your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) , outside the United States at (317) or fax (317) Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at Library of Congress Cataloging-in-Publication Data: Ott, Henry W., Electromagnetic compatibility engineering / Henry W. Ott. Rev. ed. p. cm. Earlier ed. published under title: Noise reduction techniques in electronic systems, Includes bibliographical references and index. ISBN Electronic circuits Noise. 2. Electromagnetic compatibility. I. Ott, Henry W., Noise reduction techniques in electronic systems. II. Title. TK O u24 dc Printed in the United States of America

9 To my parents, the late Henry and Virginia Ott. The values they instilled in me as a child have served me well throughout my life.

10 Everything should be made as simple as possible, but no simpler. Albert Einstein,

11 CONTENTS Preface xxiii PART 1 EMC THEORY 1 1. Electromagnetic Compatibility Introduction Noise and Interference Designing for Electromagnetic Compatibility Engineering Documentation and EMC United States EMC Regulations FCC Regulations FCC Part 15, Subpart B Emissions Administrative Procedures Susceptibility Medical Equipment Telecom Automotive Canadian EMC Requirements European Union s EMC Requirements Emission Requirements Harmonics and Flicker Immunity Requirements Directives and Standards International Harmonization Military Standards 27 vii

12 viii CONTENTS 1.10 Avionics The Regulatory Process Typical Noise Path Methods of Noise Coupling Conductively Coupled Noise Common Impedance Coupling Electric and Magnetic Field Coupling Miscellaneous Noise Sources Galvanic Action Electrolytic Action Triboelectric Effect Conductor Motion Use of Network Theory 36 Summary 38 Problems 39 References 41 Further Reading Cabling Capacitive Coupling Effect of Shield on Capacitive Coupling Inductive Coupling Mutual Inductance Calculations Effect of Shield on Magnetic Coupling Magnetic Coupling Between Shield and Inner Conductor Magnetic Coupling Open Wire to Shielded Conductor Shielding to Prevent Magnetic Radiation Shielding a Receptor Against Magnetic Fields Common Impedance Shield Coupling Experimental Data Example of Selective Shielding Shield Transfer Impedance Coaxial Cable Versus Twisted Pair 75

13 CONTENTS ix 2.13 Braided Shields Spiral Shields Shield Terminations Pigtails Grounding of Cable Shields Ribbon Cables Electrically Long Cables 96 Summary 96 Problems 98 References 103 Further Reading Grounding AC Power Distribution and Safety Grounds Service Entrance Branch Circuits Noise Control Earth Grounds Isolated Grounds Separately Derived Systems Grounding Myths Signal Grounds Single-Point Ground Systems Multipoint Ground Systems Common Impedance Coupling Hybrid Grounds Chassis Grounds Equipment/System Grounding Isolated Systems Clustered Systems Distributed Systems Ground Loops Low-Frequency Analysis of Common-Mode Choke High-Frequency Analysis of Common-Mode Choke Single Ground Reference for a Circuit 154

14 x CONTENTS Summary 155 Problems 156 References 157 Further Reading Balancing and Filtering Balancing Common-Mode Rejection Ratio Cable Balance System Balance Balanced Loads Filtering Common-Mode Filters Parasitic Effects in Filters Power Supply Decoupling Low-Frequency Analog Circuit Decoupling Amplifier Decoupling Driving Capacitive Loads System Bandwidth Modulation and Coding 190 Summary 190 Problems 191 References 192 Further Reading Passive Components Capacitors Electrolytic Capacitors Film Capacitors Mica and Ceramic Capacitors Feed-Through Capacitors Paralleling Capacitors Inductors Transformers Resistors Noise in Resistors 207

15 CONTENTS xi 5.5 Conductors Inductance of Round Conductors Inductance of Rectangular Conductors Resistance of Round Conductors Resistance of Rectangular Conductors Transmission Lines Characteristic Impedance Propagation Constant High-Frequency Loss Relationship Among C, L and e r Final Thoughts Ferrites 225 Summary 233 Problems 234 References 237 Further Reading Shielding Near Fields and Far Fields Characteristic and Wave Impedances Shielding Effectiveness Absorption Loss Reflection Loss Reflection Loss to Plane Waves Reflection Loss in the Near Field Electric Field Reflection Loss Magnetic Field Reflection Loss General Equations for Reflection Loss Multiple Reflections in Thin Shields Composite Absorption and Reflection Loss Plane Waves Electric Fields Magnetic Fields Summary of Shielding Equations Shielding with Magnetic Materials Experimental Data 265

16 xii CONTENTS 6.10 Apertures Multiple Apertures Seams Transfer Impedance Waveguide Below Cutoff Conductive Gaskets Joints of Dissimilar Metals Mounting of Conductive Gaskets The IDEAL Shield Conductive Windows Transparent Conductive Coatings Wire Mesh Screens Mounting of Windows Conductive Coatings Conductive Paints Flame/Arc Spray Vacuum Metalizing Electroless Plating Metal Foil Linings Filled Plastic Internal Shields Cavity Resonance Grounding of Shields 296 Summary 296 Problems 297 References 299 Further Reading Contact Protection Glow Discharges Metal-Vapor or Arc Discharges AC Versus DC Circuits Contact Material Contact Rating Loads with High Inrush Currents 307

17 CONTENTS xiii 7.7 Inductive Loads Contact Protection Fundamentals Transient Suppression for Inductive Loads Contact Protection Networks for Inductive Loads C Network R C Network R C D Network Inductive Loads Controlled by a Transistor Switch Resistive Load Contact Protection Contact Protection Selection Guide Examples 324 Summary 325 Problems 326 References 327 Further Reading Intrinsic Noise Sources Thermal Noise Characteristics of Thermal Noise Equivalent Noise Bandwidth Shot Noise Contact Noise Popcorn Noise Addition of Noise Voltages Measuring Random Noise 341 Summary 342 Problems 343 References 345 Further Reading Active Device Noise Noise Factor Measurement of Noise Factor 349

18 xiv CONTENTS Single-Frequency Method Noise Diode Method Calculating S/N Ratio and Input Noise Voltage from Noise Factor Noise Voltage and Current Model Measurment of V n and I n Calculating Noise Factor and S/N Ratio from V n I n Optimum Source Resistance Noise Factor of Cascaded Stages Noise Temperature Bipolar Transistor Noise Transistor Noise Factor V n I n for Transistors Field-Effect Transistor Noise FET Noise Factor V n I n Representation of FET Noise Noise in Operational Amplifiers Methods of Specifying Op-Amp Noise Op-Amp Noise Factor 375 Summary 375 Problems 376 References 377 Further Reading Digital Circuit Grounding Frequency Versus Time Domain Analog Versus Digital Circuits Digital Logic Noise Internal Noise Sources Digital Circuit Ground Noise Minimizing Inductance Mutual Inductance Practical Digital Circuit Ground Systems Loop Area 390

19 CONTENTS xv 10.6 Ground Plane Current Distribution and Impedance Reference Plane Current Distribution Ground Plane Impedance Ground Plane Voltage End Effects Digital Logic Current Flow Microstrip Line Stripline Digital Circuit Current Flow Summary 418 Summary 419 Problems 420 References 421 Further Reading 422 PART 2 EMC APPLICATIONS Digital Circuit Power Distribution Power Supply Decoupling Transient Power Supply Currents Transient Load Current Dynamic Internal Current Fourier Spectrum of the Transient Current Total Transient Current Decoupling Capacitors Effective Decoupling Strategies Multiple Decoupling Capacitors Multiple Capacitors of the Same Value Multiple Capacitors of Two Different Values Multiple Capacitors of Many Different Values Target Impedance Embedded PCB Capacitance Power Supply Isolation The Effect of Decoupling on Radiated Emissions Decoupling Capacitor Type and Value Decoupling Capacitor Placement and Mounting Bulk Decoupling Capacitors 459

20 xvi CONTENTS 11.9 Power Entry Filters 460 Summary 461 Problems 461 References 463 Further Reading Digital Circuit Radiation Differential-Mode Radiation Loop Area Loop Current Fourier Series Radiated Emission Envelope Controlling Differential-Mode Radiation Board Layout Canceling Loops Dithered Clocks Common-Mode Radiation Controlling Common-Mode Radiation Common-Mode Voltage Cable Filtering and Shielding Separate I/O Grounds Dealing With Common-Mode Radiation Issues 488 Summary 488 Problems 489 References 490 Further Reading Conducted Emissions Power Line Impedance Line Impedance Stabilization Network Switched-Mode Power Supplies Common-Mode Emissions Differential-Mode Emissions DC-to-DC Converters Rectifier Diode Noise 509

21 CONTENTS xvii 13.3 Power-Line Filters Common-Mode Filtering Differential-Mode Filtering Leakage Inductance Filter Mounting Power Supplies with Integral Power-Line Filters High-Frequency Noise Primary-to-Secondary Common-Mode Coupling Frequency Dithering Power Supply Instability Magnetic Field Emissions Variable Speed Motor Drives Harmonic Suppression Inductive Input Filters Active Power Factor Correction AC Line Reactors 539 Summary 541 Problems 542 References 544 Further Reading RF and Transient Immunity Performance Criteria RF Immunity The RF Environment Audio Rectification RFI Mitigation Techniques Transient Immunity Electrostatic Discharge Electrical Fast Transient Lightning Surge Transient Suppression Networks Signal Line Suppression Protection of High-Speed Signal Lines Power Line Transient Suppression Hybrid Protection Network 570

22 xviii CONTENTS 14.4 Power Line Disturbances Power Line Immunity Curve 573 Summary 575 Problems 576 References 578 Further Reading Electrostatic Discharge Static Generation Inductive Charging Energy Storage Human Body Model Static Discharge Decay Time ESD Protection in Equipment Design Preventing ESD Entry Metallic Enclosures Input/Output Cable Treatment Insulated Enclosures Keyboards and Control Panels Hardening Sensitive Circuits ESD Grounding Nongrounded Products Field-Induced Upset Inductive Coupling Capacitive Coupling Transient Hardened Software Design Detecting Errors in Program Flow Detecting Errors in Input/Output Detecting Errors in Memory Time Windows 617 Summary 617 Problems 619

23 CONTENTS xix References 620 Further Reading PCB Layout and Stackup General PCB Layout Considerations Partitioning Keep Out Zones Critical Signals System Clocks PCB-to-Chassis Ground Connection Return Path Discontinuities Slots in Ground/Power Planes Split Ground/Power Planes Changing Reference Planes Referencing the Top and Bottom of the Same Plane Connectors Ground Fill PCB Layer Stackup One- and Two-Layer Boards Multilayer Boards General PCB Design Procedure 653 Summary 655 Problems 657 References 658 Further Reading Mixed-Signal PCB Layout Split Ground Planes Microstrip Ground Plane Current Distribution Analog and Digital Ground Pins When Should Split Ground Planes Be Used? Mixed Signal ICs Multi-Board Systems High-Resolution A/D and D/A Converters Stripline 673

24 xx CONTENTS Asymmetric Stripline Isolated Analog and Digital Ground Planes A/D and D/A Converter Support Circuitry Sampling Clocks Mixed-Signal Support Circuitry Vertical Isolation Mixed-Signal Power Distribution Power Distribution Decoupling The IPC Problem 684 Summary 685 Problems 686 References 687 Further Reading Precompliance EMC Measurements Test Environment Antennas Versus Probes Common-Mode Currents on Cables Test Procedure Cautions Near Field Measurements Test Procedure Cautions Seams and Apertures in Enclosures Noise Voltage Measurements Balanced Differential Probe DC to 1-GHz Probe Cautions Conducted Emission Testing Test Procedure Cautions Separating C-M from D-M Noise Spectrum Analyzers 707

25 CONTENTS xxi Detector Functions General Test Procedure EMC Crash Cart Mitigation Parts List One-Meter Radiated Emission Measurements Test Environment Limits for 1-m Testing Antennas for 1-m Testing Precompliance Immunity Testing Radiated Immunity Conducted Immunity Transient Immunity Precompliance Power Quality Tests Harmonics Flicker Margin Radiated Emission Margin Electrostatic Discharge Margin 727 Summary 728 Problems 729 References 730 Further Reading 731 APPENDIX 733 A. The Decibel 733 A.1 Properties of Logarithms 733 A.2 Using the Decibel for Other than Power Measurements 734 A.3 Power Loss or Negative Power Gain 736 A.4 Absolute Power Level 736 A.5 Summing Powers Expressed in Decibels 738 B. The Ten Best Ways to Maximize the Emission from Your Product 740 C. Multiple Reflections of Magnetic Fields in Thin Shields 743

26 xxii CONTENTS D. Dipoles for Dummies 746 D.1 Basic Dipoles for Dummies 746 D.2 Intermediate Dipoles for Dummies 751 D.3 Advanced Dipoles for Dummies 756 D.3.1 Impedance of a Dipole 756 D.3.2 Dipole Resonance 756 D.3.3 Receiving Dipole 759 D.3.4 Theory of Images 759 D.3.5 Dipole Arrays 761 D.3.6 Very High-Frequency Dipoles 763 Summary 763 Further Reading 764 E. Partial Inductance 765 E.1 Inductance 765 E.2 Loop Inductance 767 E.2.1 Inductance of a Rectangular Loop 768 E.3 Partial Inductance 770 E.3.1 Partial Self-Inductance 771 E.3.2 Partial Mutual Inductance 773 E.3.3 Net Partial-Inductance 776 E.3.4 Partial Inductance Applications 776 E.3.5 Transmission Line Example 778 E.4 Ground Plane Inductance Measurement Test Setup 780 E.5 Inductance Notation 785 Summary 788 References 788 Further Reading 789 F. Answers to Problems 790 Index 825

27 PREFACE Electromagnetic Compatibility Engineering started out being a third edition to my previous book Noise Reduction Techniques in Electronic Systems, but it turned out to be much more than that, hence, the title change. Nine of the original twelve chapters were completely rewritten. In addition, there are six new chapters, plus two new appendices, with over 600 pages of new and revised material (including 342 new figures). Most of the new material relates to the practical application of the theory of electromagnetic compatibility (EMC) engineering, and it is based on experience gained from my EMC consulting work, and teaching of EMC training seminars over the last 20 plus years. Some of the more difficult and frustrating problems faced by design engineers concerns electromagnetic compatibility and regulatory compliance issues. Most engineers are not well equipped to handle these problems because the subject is not normally taught in engineering schools. Solutions to EMC problems are often found by trial and error with little or no understanding of the theory involved. Such efforts are very time consuming, and the solutions are often unsatisfactory. This situation is unfortunate, because most of the principles involved are simple and can be explained by elementary physics. This book is intended to remedy that situation. This book is intended primarily for the practicing engineer who is involved in the design of electronic equipment or systems and is faced with EMC and regulatory compliance issues. It addresses the practical aspects of electromagnetic compatibility engineering, covering both emission and immunity. The concepts presented in this book are applicable to both analog and digital circuits operating from below audio frequencies up to the GHz range. Emphasis is on cost-effective EMC designs, with the amount and complexity of the mathematics kept to a minimum. The reader should obtain the knowledge necessary to design electronic equipment that is compatible with the electromagnetic environment and compliant with national and international EMC regulations. The book is written in such a way that it can easily be used as a textbook for teaching a senior level or continuing education course in electromagnetic compatibility. To this end, the book contains 251 problems for the student to work out, the answers to which are included in Appendix F. xxiii

28 xxiv PREFACE The book is divided into two parts: Part 1, EMC Theory and includes Chapters 1 to 10. Part 2, EMC Applications, includes Chapters 11 to 18. In addition, the book contains six appendices with supplemental information. The organization of the material is as follows. Chapter 1 is an introduction to electromagnetic compatibility and covers national and international EMC regulations, including the European Union, FCC, and U.S. Military. Chapter 2 covers both electric and magnetic field cable coupling and crosstalk, as well as cable shielding and grounding. Chapter 3 covers safety, power, signal, and hardware/systems grounding. Chapter 4 discusses balancing and filtering as well as differential amplifiers, and low-frequency analog circuit decoupling. Chapter 5 is on passive components and covers the nonideal characteristics of components that affect their performance. In addition to resistors, capacitors, and inductors ferrite beads, conductors and transmission lines are also included. Chapter 6 is a detailed analysis of the shielding effectiveness of metallic sheets as well as conductive coatings on plastic, and the effect of apertures on the shielding effectiveness. Chapter 7 covers contact protection for relays and switches. Chapters 8 and 9 discuss internal noise sources in components and active devices. Chapter 8 covers intrinsic noise sources, such as thermal and shot noise. Chapter 9 covers noise sources in active devices. Chapters 10, 11, and 12 cover electromagnetic compatibility issues associated with digital circuits. Chapter 10 examines digital circuit grounding, including ground plane impedance and a discussion on how digital logic currents flow. Chapter 11 is on digital circuit power distribution and decoupling, and Chapter 12 covers digital circuit radiation mechanisms, both common mode and differential mode. Chapter 13 covers conducted emissions on alternating current (ac) and direct current (dc) power lines, as well as EMC issues associated with switching power supplies and variable-speed motor drives. Chapter 14 covers radio frequency(rf) and transient immunity, as well as a discussion of the electromagnetic environment. Chapter 15 covers electrostatic discharge protection in the design of electronic products. It focuses on the importance of a three-prong approach, which includes mechanical, electrical, and software design. Chapter 16 covers printed circuit board layout and stackup, a subject not often discussed. Chapter 17 addresses the difficult problem of partitioning, grounding, and layout of mixed-signal printed circuit boards. The final chapter (Chapter 18) is on precompliance EMC measurements, that is, measurements that can be performed in the product development laboratory, using simple and inexpensive test equipment, which relate to the EMC performance of the product. At the end of each chapter, there is a summary of the most important points discussed as well as many problems for the reader to work out. For those desiring additional information on the subjects covered, each chapter has an extensive reference, and further reading section.

29 PREFACE xxv Supplemental information is provided in six appendices. Appendix A is on the decibel. Appendix B covers the 10 best ways to maximize the emission from your product. Appendix C derives the equations for multiple reflections of magnetic fields in thin shields. Appendix D, Dipoles for Dummies, is a simple, insightful, and intuitive discussion of how a dipole antenna works. If a product picks up or radiates electromagnetic energy, then it is an antenna, therefore, an understanding of some basic antenna theory would be helpful for all engineers, especially EMC engineers. Appendix E explains the important, and not well understood, theory of partial inductance, and Appendix F provides answers to the problems contained at the end of each chapter. I would like to express my gratitude and appreciation to all those who took the time to comment on Noise Reduction Techniques in Electronic Systems and to all those who encouraged me to write Electromagnetic Compatibility Engineering. In particular, I would especially like to thank John Celli, Bob German, Dr. Clayton Paul, Mark Steffka, and Jim Brown for their insightful review of major portions of the manuscript, as well as for their encouragement and the many fruitful discussions we had on the subject of EMC. Electromagnetic Compatibility Engineering is a better book because of them. Portions of the manuscript were also used for an electromagnetic compatibility class taught by Mark Steffka at the University of Michigan Dearborn, during the 2007 and 2008 semesters. My heartfelt thanks go out to the students in those two classes for the large number of comments and suggestions that I received (many of which have been incorporated into this book), in particular their suggestions for additional problems to be included in the book. I would also like to express my appreciation to James Styles who, Mark Steffka and I both agreed, submitted the most useful comments. Finally, I would like to thank all my colleagues who took the time to review various portions of this manuscript and make useful comments and suggestions. Additional technical information, updated information on EMC regulations, as well as an errata sheet for this book are on the Henry Ott Consultants website at Livingston, New Jersey January 2009 HENRY W. OTT

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