APPLIED ELECTROMAGNETICS AND ELECTROMAGNETIC COMPATIBILITY

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1 APPLIED ELECTROMAGNETICS AND ELECTROMAGNETIC COMPATIBILITY

3 APPLIED ELECTROMAGNETICS AND ELECTROMAGNETIC C 0 M PATI B I L ITY Dipak L. Sengupta The University of Michigan and The University of Detroit Mercy Valdis V. Liepa The University of Michigan WILEY- INTERSCIENCE A JOHN WILEY & SONS, INC:., PUBLICATION

4 Copyright 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 I08 ofthe 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, Danvers, 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., 11 1 River Street, Hoboken, NJ 07030, (201) I, fax (201) , or online at Limit of LiabilitylDisclaimer 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 for 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 is available. ISBN-I ISBN-I Printed in the United States of America. I

5 This book is dedicated to Sujata Basu Sengupta and Austra Liepa

7 CONTENTS Preface Acknowledgments 1 General Considerations 1.1 Introduction 1.2 Definitions 1.3 Interference mechanisms 1.4 Examples 1.S Discussion xvii xxi The Electromagnetic Environment 2.1 Introduction 2.2 Natural Noise 2.3 Man-Made Noise vii

8 Viii CONTENTS 2.4 CW and Transient Sources Characteristic Parameters of Authorized Radiators Noise Emission Intensity 2.7 Home Environment 2.8 Discussion of Noise Sources 2.9 Subject Matter of the Book 3 Fundamentals of Fields and Waves 3.1 Introduction 3.2 Basic Parameters 3.3 Time Dependent Relations Continuity of Current and Conservation of Charge Faraday s Law Ampere s Circuital Law Lorentz Force Law Maxwell s Equations Historical Comments on Maxwell s Equations Media Considerations Boundary Conditions Energy Flow and Poynting s Theorem Uniqueness Theorem 3.4 Harmonically Oscillating Fields Introduction Phasors Time Harmonic Relations Complex Permittivity Boundary Conditions Again Notes on the Solution The Complex Poynting Theorem 3.5 The Wave Equation Time Dependent Case Time Harmonic Case 3.6 Uniform Plane Waves General Considerations Energy Considerations

9 CONTENTS ix Group Velocity Summary General Representation of TEM Waves Plane Waves in Lossy Media Skin Effect Polarization of Plane Waves Reflection and Refraction (Transmission) of Plane Waves Normal Incidence on a Plane Interface Oblique Incidence Problems Signal Waveform and Spectral Analysis Introduction Classification of Signals Energy Signals Definitions A Rectangular Pulse Power Signals Periodic Signals Trapezoidal Waveform Examples of Some Signals Problems 5 Transmission Lines 5.1 Introduction 5.2 Basic Discussion Transverse Electromagnetic (TEM) Transmission Lines Telegrapher s Equations: Quasi-Lumped Circuit Model Wave Equations 5.6 Frequency Domain Analysis General Solution Further Discussion of Propagation Constant and Characteristic Impedance Voltage, Current, and Impedance Relations I8 1 I

10 X CONTENTS 5.7 Line Parameters Coaxial Line Parallel Wire Line Parallel Plate Line Circular Wire above a Ground Plane Microstrip Line Stripline Comments 5.8 Transients on Transmission Lines Initial and Final (,Steady State) Values Transient Values 5.9 Measurements Slotted Line Measurements Network Analyzer Measurement Problems 6 Antennas and Radiation 6.1 Introduction 6.2 Potential Functions 6.3 Radiation from a Short Current Element Complete Fields Near Zone and Far Zone Considerations Near Zone and Far Zone Fields Radiated Power and Radiation Pattern Wave Impedance 6.4 Radiation from a Small Loop of Current Complete Fields Far Zone Fields Radiated Power Wave Impedance 6.5 Fundamental Antenna Parameters Radiation lntensity Directivity and Gain 6.6 Far Fields of Arbitrary Current Distributions The Radiation Vector and the Far Fields

11 CONTENTS xi Vector Effective Length of an Antenna Summary 6.7 Linear Antennas Center-Fed Linear Antenna Far Fields of a Dipole of Length f Radiated Power and Directivity Cosine, Sine, and Modified Cosine Integrals The Half-Wave Dipole 6.8 Near Field and Far Field Regions Basic Assumptions Point or Small Sources Extended Sources Definitions of Various Regions Specific Values of the Region Boundaries 6.9 Equivalent Circuits of Antennas Transmitting Antenna Receiving Antennas Equivalent Area 6.10 Antenna Arrays General Considerations A Two-Element Array Antennas Above Ground Ground and Ground Plane Image Theory Images of Electric Current Elements above Perfect Ground Dipoles above Ground Monopole Antennas 6.12 Biconical Antenna Biconical Transmission Line Finite Biconical Antenna Problems 7 Behavior of Circuit Components 7.1 Introduction 7.2 The Series RLC Circuit

12 Xii CONTENTS 7.3 Definitions of Lumped Circuit Parameters R, L, and c Circuit Theory Description Field Theory Description 7.4 Round Wires Resistance Internal Inductance 7.5 External Inductance of Round Wire Configurations General Relations Circular Loops 7.6 Inductance of Straight Wires Partial Inductance Inductance of a Closed Rectangular Loop 7.7 Other Configurations Printed Circuit Board (PCB) Lines Microstrip, Strip, and Coplanar Lines 7.8 Behavior of Circuit Elements Bode Plots Resistors Capacitors Inductors Problems 8 Radiated Emissions and Susceptibility 8.1 Introduction 8.2 Main Requirements 8.3 Emissions from Linear Elements 8.4 Two Parallel Currents Introduction Two Parallel Currents 8.5 Transmission Line Models for Susceptibility Introduction Voltage Induced on the Two-Wire Transmission Line I Electromagnetic Shielding 351

13 CONTENTS xiii Introduction Definitions Shielding Effectiveness 9.3. I Introduction SE Expressions for Computation Shielding Effectiveness: Near Field Illumination Electric and Magnetic Sources SE Expressions: Near Zone Considerations Discussion Far Zone Fields Near Zone Fields Coupling between Devices 10.1 Introduction 10.2 Capacitive (Electric) Coupling [I, Magnetic (Inductive) Coupling Some Basic Concepts Shielding of the Receptor Conductor 11 Electrostatic Discharge (ESD) Introduction Accumulation of Static Charge on Bodies Charging and Charge Separation Human Body as Source of ESD 11.5 ESD Waveforms Human Body Circuit Model 1 I.7 ESD Generator and ESD Test 12 EMC Standards 12.1 Introduction 12.2 Current US Standards Introduction FCC Radiated Emission Limits for Digital Devices

14 XiV CONTENTS FCC Conducted Emission Limits for Digital Devices 12.3 EMI/EMC Standards: Non-US Countries CISPR Standards European Norms 13 Measurements of Emission 13.1 Introduction 13.2 General 13.3 Radiated Emissions Introduction Receiver Antennas Some Results 13.4 Conducted Emissions Introduction Noise on Power Supply Lines Transients on Power Supply Lines Conducted Emissions from a DUT Some Results Appendix A: Vectors and Vector Analysis A. 1 Introduction A.2 Definitions of Scalar and Vector Fields A.2.1 Scalar Fields A.2.2 Vector Fields A.3 Vector Algebra A.3.1 Definitions A.3.2 A.3.3 A.3.4 Addition and Subtraction of Vectors Multiplication of a Vector by a Scalar Quantity Unit Vectors A.3.5 Vector Displacement and Components of a Vector A.4 Vector Surface Element AS Product of Vectors AS. 1 Dot Product of Two Vectors

15 CONTENTS XV A.5.2 The Cross Product of Two Vectors A.5.3 Product of Three Vectors A.6 Coordinate Systems A.6.1 Three Basic Coordinate Systems A.6.2 Space Variables and Base Vectors A.7 Elementary Differential Relations A.7.1 Rectangular System A.7.2 Cylindrical and Spherical Systems A.8 Transformation of Unit Vectors A.9 Vector Calculus A.9.1 A.9.2 A.9.3 Time Derivative of Vector A Space Derivatives of a Vector A Gradient of a Scalar Function A.9.4 Flux of a Vector A.9.5 A.9.6 Divergence of a Vector A Curl of a Vector Function A.10 The Laplacian V2 = V. V A. 1 1 Comments on Notation A. 12 Some Useful Relations A.12.1 Vector Algebra A Vector Identities A Integral Relations Problems Appendix B: Frequency Band Designations Appendix C: Constitutive Relations Index

17 PREFACE Over the past two decades the electromagnetic compatibility (EMC) considerations in the design of digital electronic devices or components have grown in importance throughout the world. This is because the United States and other industrial nations do not allow electronic devices to be marketed in their countries unless their electromagnetic noise emissions have been tested and certified to meet certain limits. As a result the electronic industries are showing increasing interest in electrical engineering (EE) graduates with an EMC background. Currently, except for a handful of schools, the undergraduate EE programs in the United States do not address the EMC issues directly, although most of them require at least one 3- or 4-credit course in electromagnetics. Students specializing in fields and waves are probably equipped to investigate certain fundamental problems of EMC. A few well-known schools with strong programs in electromagnetics often express the opinion that a good training in fields and waves prepares the students sufficiently to meet the challenges of EMC in their professional life. Nevertheless, to meet the growing demand from industries, the IEEE is actively encouraging schools to include EMC as a course topic in their curricula. xvii

xviii PREFACE During the summer of 1994 the first named author (DLS) introduced a seniodgraduate level course in EMC: at the Electrical Engineering and Physics Department of the University of Detroit

18 xviii PREFACE During the summer of 1994 the first named author (DLS) introduced a seniodgraduate level course in EMC: at the Electrical Engineering and Physics Department of the University of Detroit Mercy. It was taken mostly by practicing engineers from the Detroit metropolitan area s Big Three automobile manufacturing and other related industries. Our own attending EE students had varied levels of background in electromagnetics but none had the expected familiarity with Maxwell s equations and plane electromagnetic waves. Because of this we faced difficulties in the planning of the course. In addition at that time we had a very limited selection of textbooks on EMC. We chose Introduction to Electromagnetic Compatibility by C. R. Paul supplemented by Noise Reduction Techniques ifil Electronic Systems by H. R. Ott, but found them not completely suitable for our students needs. It was therefore necessary to develop lecture notes specialized to the class. The initial lectures were devoted to bringing the students background level in electromagnetics up to a uniform level of familiarity with Maxwell s equations. After this, plane waves and related topics, transmission lines, antennas, and radiation were introduced. Overall, knowledge of these topics was deemed to be a necessary minimum background for an EMC course. The rest of the lectures were on selected topics in EMC. The course was so well received that it was repeated the next year (1995). Because of continued demand it is still being offered every alternate year. Our experience motivated us to write a textbook combining the fundamentals of fields and waves, a few selected topics of applied electromagnetics, and a variety of topics typical of EMC. The descriptions of electromagnetics are placed in the context of EMC, and those of EMC are presented where they help in the analysis of EMC phenomena as well as in planning the measurements needed for compliance with EMC specifications. The book is also an outgrowth of classroom lecture notes for a number of undergraduate/graduate level courses in electromagnetic theory and applied electromagnetics given by the first author over many years at the electrical engineering departments of the University of Michigan, Ann Arbor and the University of Detroit Mercy. A brief outline of the book follows. Chapter 1 introduces electromagnetic interference in general, and describes the evolution of EMC in the digital electronics era. It also defines various acronyms that are used alternatively, and often erroneously, to describe interference effects. The electromagnetic environment consists of a variety of natural and human-made noise sources in which electronic devices are expected to operate. These noise sources are described in Chapter 2. Chapter 3 is about the fundamental concepts and relations of electromagnetic fields and waves. Basic laws of electricity and magnetism, their generalizations, and their mathematical descriptions by Maxwell are described. Boundary conditions, the Poynting theorem, and energy transfer are then discussed. The time harmonic formulation of Maxwell s equations are introduced next and their applications to general problems are described. Fi-

$PREFACE xix nally, uniform plane waves in lossless and lossy media, skin effect phenomena, and reflection and refraction of plane waves are discussed.$

19 PREFACE xix nally, uniform plane waves in lossless and lossy media, skin effect phenomena, and reflection and refraction of plane waves are discussed. Chapter 4 describes the frequency spectra of known electromagnetic sources to the extent necessary for the characterization of their electromagnetic emissions as functions of frequency from the viewpoint of EMC. Basic characteristics and applications of TEM transmission lines and, in particular, the two-wire, coaxial, microstrip, stripline, and parallel plate lines are briefly described in Chapter 5. The time dependent or the transient solutions for a two-wire line are also briefly mentioned here. Chapter 6 discusses the fundamentals of antennas and radiation, including the equivalent circuits for receiving and transmitting antennas. The radiation from basic antennas, such as the electric and magnetic dipoles, is described in detail; these descriptions are then utilized in the discussion of certain general characteristics of radiation. In addition the half-wave dipole and the biconical antenna are described. The behavior of the lumped circuit parameters R, L and C are described in Chapter 7. The field theory definitions of these parameters are introduced at first; they are then used to analyze performance as functions of frequency. Chapter 8 gives analytical descriptions of the radiated emissions from certain components of an electronic device and their susceptibility to outside noise. Simple wire and transmission-line models are used to estimate these emissions and susceptibility of the components when illuminated by incident plane waves from outside sources. Principles of electromagnetic shielding are briefly described in Chapter 9. The inductive and capacitive coupling effects in selected circuit configurations are outlined in Chapter 10. Chapter 11 deals with the electrostatic discharge (ESD) phenomenon and its impact on the design of electronic systems from the viewpoint of EMC. Chapter 12 gives the typical standards for EMC prescribed by the FCC for both Class A and Class B types of electronic devices. Some European standards are also mentioned. Chapter 13 describes briefly the measurement procedures that are followed to test the compliance of a device to the emission limits required by the enforcing agency. Appendix A gives a rather complete description of the vectors and vector calculus that are essential background knowledge for any course in electromagnetics. Problems, and answers to many of them, are provided at the end of some chapters. The book is intended to serve as a textbook for courses on applied electromagnetics and electromagnetic compatibility at the seniodgraduate level in EE. The prerequisites for such a course are completion of basic undergraduate EE and physics courses in electricity and magnetism, analog and digital electronic circuits, and advanced calculus. The description of fields and waves starts at the basic level and then proceeds to a fairly high level. Topics in EMC are described such that the electromagnetic interference effects associated with them can be better understood.

20 XX PREFACE Depending on the electromagnetic background of the class, the instructor may apply hidher discretion to adjust the emphasis on specific course materials. For a class with a sufficient background in electromagnetic fields, the book can be used by the instructor to delve into the discussed EMC topics in more detail and also to put forward additional EMC topics. For example, one could include designs for EMC that are not considered here and extend the discussion of EMC measurements. The appropriate materials for taking this direction are in Chapters 1,2, and 7 through 13. This book is also designed to serve as a textbook for coursework on applied electromagnetics. The appropriate chapters are 3 through 6 (and perhaps 7) and Appendix A. The instructor may choose to include more discussion of these topics as well as more materials on antennas, for example. Such a course might even be followed by the course on EMC described earlier. Finally, practicing engineers in industry interested in exploring EMC may find the book useful for self-study. The topics and descriptions are such that engineers involved in the design of electronic devices for EMC will find the book useful as a reference tool. Anii Arbor: Michigan D. L. SENGUPTA V. V. LIEPA

21 ACKNOWLEDGMENTS We gratefully acknowledge the support received from the Department of Electrical Engineering and Computer Science of the University of Michigan and the Department of Electrical Engineering and Physics of the University of Detroit Mercy, where virtually all the material presented in this book was taught over many years. The suggestions and comments received from our students helped us in the organization and presentation of the material. We thank our students for their critical comments. The final preparation of the manuscript was accomplished at the University of Michigan Radiation Laboratory. We thank the Director of the Radiation Laboratory for generously providing the Laboratory facilities for this purpose. The tedious task of transforming the handwritten manuscript to its final form was accomplished by a team of people. We are especially grateful to Joseph Brunett who supervised and actively carried out the electronic formatting and graphic design. He was assisted by Richard Cames, Bradley Koski, and Sanita Liopa. Our grateful thanks to all of them for performing an excellent job. We are grateful to the staff of John Wiley & Sons, Inc., especially to George Telecki, Associate Publisher, Wiley-Interscience, for his interest, support, cooperation, and production of the book; Danielle Lacourciere, Senior Production Editor, for the production xxi

22 xxii of the book; and Rachel Witmer, Editorial Program Coordinator, for managing the production schedule and the cover design. The writing of this book has been a long and arduous task. It would not have been completed without the pistience and continuous support of our wives and children.

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