Handbook for EMC Testing and Measurement

225 Pages·2007·22.445 MB·English

by  Morgan, David

A Handbook for

EMC
Testing and Measurement
David Morgan
Published by The Institution of Engineering and Technology, London, United Kingdom
First edition 0 1994 Peter Peregrinus Ltd
Paperback edition 0 2007The Institution of Engineering and Technology
First published 1994 (0 86341 262 9)
Reprinted 1996
Paperback edition 2007
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Convention. All rights reserved. Apart from any fair dealing for the purposes of research
or private study, or criticism or review, as permitted under the Copyright, Designs and
Patents Act, 1988, this publication may be reproduced, stored or transmitted, in any
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terms should be sent to the publishers at the undermentioned address:
The Institution of Engineering and Technology
Michael Faraday House
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Herts, SCl 2AY, United Kingdom
www.theiet.org
While the author and the publishers believe that the information and guidance given
in this work are correct, all parties must rely upon their own skill and judgement when
making use of them. Neither the author nor the publishers assume any liability to
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such error or omission is the result of negligence or any other cause. Any and all such
liability is disclaimed.
The moral rights of the author to be identified as author of this work have been
asserted by him in accordance with the Copyright, Designs and Patents Act 1988.
British Library Cataloguing in Publication Data
A catalogue record for this product is available from the British Library
ISBN 978-0-86341-756-6
Printed in the UK by Lightning Source UKLtd, Milton Keynes
Contents
Foreword XUl
1 Natureand origins ofelectrom.agnetic com.patibility 1
1.1 Definitions ofelectromagnetic compatibility 1
1.2 Visualising the EMI problem 1
1.2.1 Sources ofEMI 1
1.2.2 EMI coupling to victim equipments 5
1.2.3 Intersystem and intrasystem EMI 7
1.3 Historical background 7
1.3.1 Early EMC problems 7
1.3.2 Early EMC problems with military equipment 8
1.3.3 The costofEMC 9
1.3.4 Serious EMI problems 10
1.4 Technical disciplines and knowledge areas within EMC 10
1.4.1 Electrical engineering 10
1.4.2 Physics 11
1.4.3 Mathematical modelling 11
1.4.4 Limited chemical knowledge 11
1.4.5 Systems engineering 11
1.4.6 Legal aspects ofEMC 11
1.4.7 Test laboratories 11
1.4.8 Quality assurance: total quality management 12
1.4.9 Practicalskills 12
1.5 Philosophy ofEMC 12
1.6 References 12
2 EMC standards and specifications 14
2.1 The need for standards and specifications 14
2.1.1 Background 14
2.1.2 Contents ofstandards 14
2.1.3 The need to meet EMC standards 14
2.2 Civil and military standards 15
2.2.1 Range ofEMC standards in use 15
2.2.2 Derivation ofmilitary standards 15
2.2.3 Derivation ofcommercialstandards 17
2.2.4 Generation ofCENELEC EMC standards 18
2.3 UK/European commercial standards 18
2.3.1 UK standards relating to commercial equipment 18
2.3.2 Comparing tests 19
2.3.3 European commercialstandards 20
2.3.4 German standards 21
2.4 US commercial standards 23
2.4.1 US organisations involved with EMC 23
2.4.2 FCC requirements 23
2.4.3 Other US commercial standards 24
2.5 Commercial EMC standards inJapan and Canada 24
2.5.1 Japanese EMC standards 24
2.5.2 Canadian EMC standards 25
2.6 Product safety 25
2.6.1 Safety ofelectrical devices 25
2.6.2 Productsafety 26
2.6.3 Radiation hazards to humans 26
2.6.4 Hazards ofelectromagnetic radiation to ordnance 27
2.7 ESD and transients 27
2.7.1 ESD (electrostatic discharge) 27
2.7.2 Transients and power line disturbances 28
2.8 US military EMC standards 28
2.8.1 MIL STD 461/462/463 28
2.8.2 MIL-E-6051D 31
2.8.3 Other US military standards 31
v
VI A HANDBOOK FOR EMC TESTINGAND MEASUREMENT
2.9 UK military standards 31
2.9.1 Service and establishment-specific standards 31
2.9.2 Project-specificstandards 33
2.9.3 DEF STAN 59-41 (1.988) 34
2.10 Following chapters 36
2.11 References 36
3 Outline ofEMC testing 38
3.1 Types ofEMC testing 38
3.1.1 Development testing 38
3.1.2 Measurement to verify modelling results 38
3.1.3 Preconformance test measurements 39·
3.1.4 Conformance testing 39
3.1.5 Conforrnance test plan 40
3.2 Repeatability in EMC testing 41
3.2.1 Need for repeatability and accuracy 41
3.2.2 Accuracy ofEMC measurements 42
3.2.3 Implications ofrepeatability ofEMC measurements 44
3.3 Introduction to EMC test sensors, couplers and antennas 44
3.3.1 EMC sensorgroups 44
3.3.2 Conduction and induction couplers 44
3.3.3 Radiative coupling EMC antennas 45
3.4 References 46
4 Measurem.entdevices for conductedEMI 48
4.1 Introduction 48
4.2 Measurement by direct connection 48
4.2.1 Line impedance stabilisation network 49
4.2.2 10flF feedthrough capacitor 51
4.2.3 RF coupling capacitors 52
4.2.4 Distributed capacitance couplers 55
4.2.5 High-impedance RF voltage probes 56
4.2.6 Directly connected transformers 60
4.3 Inductively coupled devices 61
4.3.1 Cable current probes 61
4.3.2 Current injection probes 65
4.3.3 Close magnetic field probes 66
4.3.4 Surface current probes 66
4.3.5 Cable RF current clamps 68
4.3.6 Magnetic induction tests 70
4.4 References 70
5 Introductionto antennas 72
5.1 EMC antennas 72
5.2 EMC antenna basics 72
5.2.1 Arbitrary antennas 72
5.2.2 EMC antennas 73
5.3 Basic antenna parameters 73
5.3.1 Gain 73
5.3.2 Aperture 74
5.3.3 Transmitting antenna factor 74
5.3.4 Receiving antenna factor 74
5.3.5 Antenna phase centre 75
5.3.6 Mutual antenna coupling 75
5.3.7 Wavefield impedance 76
5.3.8 Near-field/far-field boundary 76
5.3.9 Beamwidth 79
5.3.10 Spotsize 81
5.3.11 Effective length 82
5.3.12 Polarisation 82
5.3.13 Bandwidth 83
5.3.14 Input impedance 84
5.4 References 84
CONTENTS VB
6 Antennas for radiated emissiontesting 86
6.1 Passive monopoles 86
6.1.1 Construction 86
6.1.2 Performance 87
6.2 Active monopoles 88
6.2.1 Advantages 88
6.2.2 Disadvantages 88
6.3 Tuned dipoles 89
6.3.1 Introduction 89
6.3.2 Practical tuned dipoles 90
6.3.3 Commercial EMC tuned dipoles 91
6.3.4 Radiated emission testing 91
6.4 Electricallyshort dipoles 92
6.4.1 Specialshort calibration dipoles 92
6.4.2 Roberts dipoles 92
6.4.3 Small nonresonant dipoles 93
6.4.4 Microscopic dipole probes 93
6.5 Biconic dipoles 94
6.5.1 Introduction 94
6.5.2 Commercial biconic antennas 94
6.5.3 Use ofbiconic antennas 95
6.6 Wideband antennas 96
6.6.1 Introduction 96
6.6.2 Log-periodic antenna 96
6.7 Log-periodic dipole antenna 96
6.8 Conical log-spiral antenna 98
6.9 Horn antennas 100
6.10 Ridged guide horn antennas 102
6.11 Reflector antennas 103
6.12 Magnetic field antennas 105
6.12.1 Introduction' 105
6.12.2 Passive loops 105
6.12.3 Active loops 106
6.12.4 Loop calibration 106
6.12.5 Magnetic field susceptibility tests 107
6.13 References 108
7 Use ofantennas for radiated susceptibilitytesting 110
7.1 Introduction 110
7.1.1 Types ofantennas used in susceptibility testing 110
7.1.2 Standards requiring immunity tests 110
Free-field antennas
7.2 Tuned halfwave dipoles III
7.3 Biconic dipoles III
7.4 Log-periodic dipoles 112
7.5 Conical log-spiral antennas 113
7.6 Horn antennas 113
7.7 Parabolic reflector antennas 114
7.8 Radiated immunity field strength requirements 114
7.8.1 Requirements for commercial products 114
7.8.2 Requirements for civil aircraft 114
7.8.3 Military requirements 115
7.9 E-field generators 115
7.9.1 Construction 115
7.9.2 Practical devices 116
7.10 Long wire lines 118
7.10.1 Advantages 118
7.10.2 Use in testing military equipment 118
Bounded-wave devices
7.11 Parallel-plate line 119
7.11.1 Properties 119
7.11.2 Lineimpedance 119
7.11.3 Construction 119
VUI A HANDBOOK FOR EMC TESTINGAND MEASUREMENT
7.11.4 Complex lines 121
7.11.5 Field uniformity and VSWR 121
7.11.6 Use in screened room 122
7.12 TEM cells 123
7.12.1 Basicconstruction 123
7.12.2 Crawford cell performance 123
7.12.3 Wave impedanceinTEM cell 124
7.12.4 Field distortions in TEM cell 124
7.12.5 Other uses ofTEM cells 125
7.12.6 Asymmetric TEM cells 126
7.13 GTEM cells 126
7.13.1 Description 126
7.13.2 Typical construction 126
7.13.3 Power requirements 127
7.13.4 GTEM cells used for emission testing 127
7.13.5 Pulse testing 128
7.14· References 128
8 Receivers, analysers and measurementequipment 130
8.1 Introduction 130
8.1.1 Outline ofequipment 130
8.1.2 Groups ofequipment 130
Instrumentation for emission testing 130
8.2 EMI receivers 130
8:2.1 Design requirements 130
8.2.2 Selectivity and sensitivity 132
8.2.3 Detectors 133
8.2.4 Commercially available EMI receivers 134
8.3 Spectrum analysers 134
8.3.1 Introduction 134
8.3.2 Analyser types 134
8.3.3 Analyseroperation 135
8.4 Preselectors and filters 136
8.4.1 Preselectors 136
8.4.2 Bandlimitingfilters 136
8.5 Impulse generators 137
8.5.1 Description 137
8.5.2 Design 137
8.5.3 Use ofimpulse generators 138
8.6 Digital storage oscilloscopes 139
8.6.1 Advantages ofdigital oscilloscopes 139
8.6.2 Typical waveforms to be measured 139
8.6.3 Recording injected pulses for immunity testing 140
8.6.4 Digital transient recorder architecture 140
8.7 AFIRF voltmeters 141
8.8 RF power meters 141
8.9 Frequency meters 142
Instrumentation for susceptibility testing 142
8.10 Signalsources 142
8.10.1 Signalsynthesisers 142
8.10.2 Signal sweepers 143
8.10.3 Trackinggenerators 143
8.11 RF power amplifiers 144
8.11.1 Introduction 144
8.11.2 Specifying an amplifier 145
8.11.3 RF amplifiers- conclusions 147
8.12 Signal modulators 147
8.12.1 Modulation requirements 147
8.12.2 Built-in modulators 147
8.12.3 Arbitrary waveform generators 148
8.13 Directional couplers, circulators and isolators 148
8.13.1 Amplifier protection devices 148
CONTENTS IX
8.13.2 Directional couplers 148
8.13.3 Hybrid rings, circulators and isolators 150
8.13.4 Protection devices conclusion 151
8.14 Automatic EMC testing 151
8.14.1 Introduction 151
8.14.2 Automated emission testing 152
8.14.3 Automated susceptibility testing 152
8.14.4 In the future? 152
8.15 References 152
9 EMC test regitnes andfacilities 154
9.1 Introduction 154
9.1.1 Main test regimes 154
9.1.2 Special testing 154
9.2 EMC testing in screened chambers 154
9.2.1 Enclosed test chambers 154
9.2.2 Standard shielded enclosures 155
9.2.3 RF anechoic screened chambers 159
9.2.4 Mode-stirred chambers 163
9.2.5 Novel facilities 164
9.3 Open-range testing 165
9.3.1 Introduction 165
9.3.2 Testsite 165
9.3.3 Testing procedures 165
9.3.4 Site calibration 167
9.3.5 Measurement repeatability 168
9.3.6 Comments on open-site testing 171
9.4 Low-level swept coupling and bulk current injection testing 171
9.4.1 Introduction 171
9.4.2 Low-level swept coupling 172
9.4.3 Bulk current injection 175
9.5 References 176
10 Electrotnagnetic transient testing 179
10.1 Introduction 179
10.1.1 Transient types 179
10.1.2 Continuous and transient signals 179
10.2 Fourier transforms 180
10.2.1 Introduction 180
10.2.2 The transform 180
10.2.3 Introducing phase 181
10.2.4 Fourier transform expressions 182
10.2.5 Impulse response 182
10.2.6 Convolution 184
10.2.7 Advantages oftime-domain manipulation 184
10.3 ESD-electrostatic discharge 185
10.3.1 Introduction 185
10.3.2 The ESD event 185
10.3.3 Types ofESD 187
10.3.4 ESD-induced latentdefects 188
10.3.5 Types ofESD test 188
10.3.6 Numberofdischarges per test 191
10.3.7 ESD test voltage levels 191
10.3.8 Assessing EDT performance 192
10.4 Nuclear electromagnetic pulse 192
10.4.1 Introduction 192
10.4.2 Types ofNEMP 193
10.4.3 Exoatmospheric pulse generation 193
10.4.4 NEMP induced currents 194
10.4.5 NEMP testing 195
10.5 Lightning impulses 201
x A HANDBOOKFOREMC TESTINGAND MEASUREMENT
10.5.1 Lightning environment 201
10.5.2 Defining the discharge 202
10.5.3 Effects on equipment 204
10.6 Transients and general powerdisturbances 205
10.6.1 Importance ofpower transients 205
10.6~2 Examples ofpowersupply immunity standards 205
10.6.3 Summary 206
10.7 References 207
11 Uncertaintyanalysis: quality controland testfacility certification 209
11.1 Introduction 209
11.2 Some definitions 209
11.3 Measurement factors 210
11.4 Random variables 211
11.4.1 Student's t-distribution 213
11.5 Systematic uncertainty 213
11.6 Combining random and systematic uncertainties 214
11.7 Uncertainties in EMC measurements 214
11.7.1 Contributions to measurement uncertainty 214
11.7.2 Identification ofuncertainty factors 215
11.7.3 Estimation ofuncertainty values 216
11.7.4 Estimate oftotal uncertainty 218
11.8 Test laboratory measurement uncertainty 218
11.8.1 NAMAS 218
11.8.2 NAMAS and measurement uncertainty 218
11.8.3 Limits and production testing 219
11.9 NAMAS requirements for laboratory accreditation 219
11.9.1 Requirements for accreditation 219
11.9.2 Advantages oflaboratory accreditation 220
11.10 References 221
12 Designingto avoidEMC problem.s 223
12.1 Intrasystem and intersystem EMC 223
12.1.1 Intrasystem EMC 223
12.1.2 Design for formal EMC compliance 224
12.2 System-level EMC requirements 228
12.2.1 Top-level requirements 228
12.2.2 Determining EMC hardening requirement 228
12.2.3 Simple coupling models 229
12.2.4 Susceptibility hardening case study 231
12.2.5 Emission suppression requirement 233
12.2.6 System hardening flow diagram 233
12.2.7 Subsystem apportionment and balanced hardening 233
12.2.8 Staffsupport for EMC 235
12.3 Specific EMC design techniques 236
12.4 References 236
13 AchievingproductEMC:checklistsforproductdeveloptnentandtesting238
13.1 Introduction 238
13.1.1 Chapterstructure 238
13.1.2 Example adopted 238
13.1.3 Personal computers and information technology 238
13.2 Information about EMC 238
13.2.1 Customersources 238
13.2.2 Regulatory authorities 239
13.2.3 Industry sources 240
13.2.4 Equipment, component and subsystem suppliers 240
13.2.5 Professional bodies and conferences 240
13.2.6 EMC consultants and training 241
13.2.7 Electronics and EMC technical press 241
CONTENTS Xl
13.3 Determining an EMC requirement 241
13.4 Developing an approach to EMC design 242
13.4.1 Process flow chart 242
13.4.2 EMC strategy 242
13.4.3 Immunity first? 243
13.4.4 Example ofEMC design process 243
13.5 Technical construction file 244
13.5.1 Routes to compliance options 244
13.5.2 Circumstances requiring the generation ofa technical file 245
13.5.3 Contents ofa technical file 245
13.5.4 Report from a competent body 246
13.5.5 Testing or technical file? 246
13.6 Selfcertification 246
13.6.1 Need for an in-house facility 246
13.6.2 Gradual development 247
13.6.3 Estimates offacility cost 248
13.6.4 Turnkey facilities 248
13.7 Conclusion 248
13.8 References 249
Appendix 1 250
1.1 Signal bandwidth definitions 250
1.2 UK EMC legislation (up to 1January 1996) 252
1.3 European EMC standards 254
1.4 German decrees and standards 259
1.5 US EMC regulations and standards 261
1.6 German, North American andJapanese EMC standards 262
1.7 Electrical safety and electromagnetic radiation 264
1.8 Military EMC standards 266
1.9 Compendium ofEMC and related standards 271
Appendix 2 277
2.1 Modulation rules 277
Appendix 3 278
3.1 NAMAS-accredited laboratories 278
3.2 Competent bodies 280
3.3 EMC consultancy and training 282
3.4 Useful publications on EMC 283
Index 285
Chapter 1
Nature and origins of
electrom.agnetic com.patibility
1.1 Definitions ofelectroIllagnetic the costs which are associated with achieving elec
cOIllpatibility tromagnetic compatibility (EMC) need not be
borne. Some of these wider issues are explored
The formal definition ofelectromagnetic compat later, but for now another definition of this
ibility, as given in the International fascinating and wide ranging concept is examined.
Electrotechnical Vocabulary (IEC 50) is: 'the Keiser [3J defines EMC in this way: 'electrical
ability of a device, equipment or system to and electronic devices can be said to be electro
function satisfactorily in its electromagnetic magnetically compatible when the electrical noise
environment without introducing intolerable elec generated by each does not interfere with the
tromagnetic disturbances to anything in that normal performance ofany ofthe others. EMC is
environment' [1J. A similar definition cited by that happy situation in which systems work as
Duff [2J is given as: 'the ability of equipments intended, both within themselves and in their
and systems to function as intended, without environment'.
degradation or malfunction in their intended Electromagnetic interference induces
operational electromagnetic environments. undesirable voltages and currents in the circuits of
Further, the equipment or system should not the victim equipment. This can cause audible
adversely affect the operation of~ or be affected noise in radio receivers and spots, snow or loss of
by, any other equipment or system'. frame synchronisation on TV pictures. When
Electromagnetic interference (EMI) can be vital communications links, computer installations
viewed as a kind of environmental pollution or computer driven industrial process control
which can have consequences that are equipment is the victim equipment, more serious
comparable to toxic chemical pollution, vehicle consequences can occur.
exhaust emissions or other discharges into the Interference can reach the victim system by two
environment. The electromagnetic spectrum is a basic routes: conduction along cables, and electro
natural resource which has been progressively magnetic radiation. This chapter examines typical
tapped by man over the last 100 years. Most of sources ofEMI and discusses the technical basis of
the development has taken place in the last 50 electromagnetic compatibility within an
years with the advent of public service broad equipment, and between the equipment and its
casting, point-to-point and mobile communica environment in terms of conducted and radiated
tions etc. which has brought great economic and interference paths.
social benefits. The spectrum is now almost full
and it is proving difficult to satisfy the pressures
for new uses of this resource. Modern life has
1.2 Visualising the EMI probletn
come to depend heavily on systems that use the
electromagnetic spectrum and its protection is in
1.2.1 Sources ofEMI
the interests ofus all. For this reason unwarranted
electromagnetic interference represents a real Any electrical or electronic device that has
economic and social threat which can even result changing voltages and currents can be a source of
in injury or death. EM!. If the culprit equipment has no cables
Unfortunately, electromagnetic interference connecting it to the outside world, for example a
cannot be smelled, tasted or seen by either the lay battery powered electric shaver, then the
person who purchases electronic products or by interfering energy generated by sparking within
the corporate technical manager who has to the electric motor can only travel as an electro
supervise the design of the latest electronic magnetic wave. If the shaver is mains powered,
product and get it to the marketplace as fast as both radiated noise and interference conducted
possible, for the lowest possible cost. There has, along the cable into the mains wiring are possible.
therefore, been a tendency to deny that EMI is a This is illustrated in Figure 1.1 where a mains
problem in the modern world and to argue that powered shaver and a washing machine are both