Table Of ContentIEE ELECTROMAGNETIC WAVES SERIES 23
Ferrites
at
microwave
Frequencies
A.J. Baden Fuller
Peter Peregrinus Ltd. on behalf of the Institution of Electrical Engineers
IEE ELECTROMAGNETIC WAVES SERIES 23
Series Editors: Professors R J. B. Clarricoats,
E. D. R. Shearman and J. R. Wait
Other volumes in this series
Volume 1 Geometrical theory of diffraction for electromagnetic waves
Graeme L. James
Volume 2 Electromagnetic waves and curved structures
Leonard Lewin, David C. Chang and Edward F. Kuester
Volume 3 Microwave homodyne systems
Ray J. King
Volume 4 Radio direction-finding
R J. D. Gething
Volume 5 ELF communications antennas
Michael L. Burrows
Volume 6 Waveguide tapers, transitions and couplers
F. Sporleder and H. G. Unger
Volume 7 Reflector antenna analysis and design
P. J. Wood
Volume 8 Effects of the troposphere on radio communications
Martin P. M. Hall
Volume 9 Schumann resonances in the earth-ionosphere cavity
P. V. Bliokh, A. P. Nikolaenko and Y. F. Filippov
Volume 10 Aperture antennas and diffraction theory
E. V. Jull
Volume 11 Adaptive array principles
J. E. Hudson
Volume 12 Mlcrostrip antenna theory and design
J. R. James, P. S. Hall and C. Wood
Volume 13 Energy in electromagnetism
H. G. Booker
Volume 14 Leaky feeders and subsurface radio communications
P. Delogne
Volume 15 The handbook of antenna design, volume 1
Editors: A. W. Rudge, K. Milne, A. D. Olver, P. Knight
Volume 16 The handbook of antenna design, volume 2
Editors: A. W. Rudge, K. Milne, A. D. Olver, P. Knight
Volume 17 Surveillance radar performance prediction
P. Rohan
Volume 18 Corrugated horns for microwave antennas
P. J. B. Clarricoats and A. D. Olver
Volume 19 Microwave antenna theory and design
Editor: S. Silver
Volume 20 Advances in radar techniques
Editor: J. Clarke
Volume 21 Waveguide handbook
N. Marcuvitz
Volume 22 Target adaptive matched illumination radar
Dag T. Gjessing
Volume 24 Propagation of short radio waves
Editor: D. E. Kerr
Volume 25 Principles of microwave circuits
Editors: C. G. Montgomery, R. H. Dicke, E. M. Purcell
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11
Peter Peregrinus Ltd. on behalf of the Institution of Electrical Engineers
Published by: Peter Perogrinus Ltd., London, United Kingdom
© 1987: Peter Peregrinus Ltd.
All rights reserved. No part of this publication may be reproduced, stored
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own skill and judgment when making use of it. Neither the author nor the
publishers assume any liability to anyone for any loss or damage caused
by any error or omission in the work, whether such error or omission is the
result of negligence or any other cause. Any and all such liability is
disclaimed.
British Library Cataloguing in Publication Data
Baden-Fuller, A. J.
Ferrites at microwave frequencies.—
(IEE electromagnetic waves series; v.23)
1. Ferrite devices 2. Microwave devices
I. Title II. Series
621.381*3 TK7872.F4
ISBN 0 86341 064 2
Reprinted 2005
Printed in the United Kingdom at the University Press, Cambridge
Contents
Page
Preface ix
1 1ntroduction 1
1.1 Introduction 1
1.2 Historical survey 2
11.3 Magnetism 4
1.4 Ferromagnetism 6
1.5 Spinel ferrites 8
1.6 Magnetic garnets 12
11.7 Permanent magnet ferrites 13
11.8 Dielectric loss mechanisms 14
11.9 Preparation 15
1.10 References 16
2 Planei waves in an infinite ferrite medium 18
2.1 Descriptive introduction 18
2.2 Magnetisation equation 21
2.3 Tensor permeability 22
2.4 Damping 25
2.5 Longitudinal magnetisation 29
2.6 Attenuation 32
2.7 Magnetisation at any angle 34
2.8 Faraday rotation 37
2.9 Transverse magnetisation 40
4l.\0 References 43
Longitudinally magnetised ferrite in circular waveguide 45
2.1 Introduction 45
3.2 Wave equations in the ferrite 48
3.3 Field components 52
3.4 Ferrite-filled circular waveguide 57
vi Contents
3.5 Ferrite rod at centre of circular waveguide 60
3.6 Ferrite tube adjacent to the wall of circular waveguide 66
3.7 More complicated waveguide structures 71
3.8 Approximate methods 74
3.9 Attenuation 75
3.10 References 77
4 Transversely magnetised ferrite in circular waveguide 78
4.1 Introduction 78
4.2 Circumferentially magnetised ferrite tube 79
4.3 Circumferentially magnetised ferrite-filled waveguide 81
4.4 Circumferentially magnetised ferrite tube theory 83
4.5 Transverse magnetisation 88
4.6 Four-pole field 90
4.7 Theoretical analysis 93
4.8 References 96
5 Circular waveguide devices 98
5.1 Longitudinally magnetised rotator 98
5.2 Faraday rotation circulator 102
5.3 Variable attenuation and phase 104
5.4 Isolator and circular polariser 108
5.5 Circumferentially magnetised ferrite tube - latching phase
changer 110
5.6 Birefringence - quarter-wave plate 111
5.7 Birefringence - half-wave plate 113
5.8 References 116
6 Transversely magnetised ferrite in rectangular waveguide 118
6.1 Introduction 118
6.2 Field analysis in the ferrite 120
6.3 Single full-height ferrite slab 122
6.4 Two symmetrical full-height ferrite slabs 126
6.5 Full-height dielectric and ferrite slabs 128
6.6 Field displacement 130
6.7 Parallel plate waveguide 132
6.8 Perturbation theory 133
6.9 Resonance isolation 137
6.10 References 139
7 Rectangular waveguide devices 141
7.1 Introduction 141
7.2 Variable nonreciprocal phase changer 142
7.3 Circulator
Contents vii
1A Variable reciprocal phase changer 152
7.5 Resonance isolator 15 3
7.6 Field-displacement isolator 155
7.7 Longitudinally magnetised ferrite - reciprocal phase changer 156
7.8 References 159
8 Y-junction circulator 161
8.1 Introduction 161
8.2 Scattering matrix theory 162
8.3 Junction cavity 167
8.4 Is-plane junction 170
8.5 Isocirculator 171
8.6 Matching networks 173
8.7 Stripline 174
8.8 References 179
9 Stripline and microstrip devices 181
9.1 Introduction 181
9.2 Microstrip 182
9.3 Ferrite substrate 185
9.4 Slotline and finline 188
9.5 Y-junction circulator 189
9.6 Variable phase changer 191
9.7 Field-displacement isolator 193
9.8 Field-displacement phase changer and circulator 198
9.9 Ferrite resonant cavity 200
9.10 References 203
10 Millimetre wave devices 206
10.1 Introduction 206
10.2 Limitations of ferrite materials 208
10.3 Permanent magnet materials 209
10.4 Faraday rotation devices 211
10.5 Transversely magnetised structures 213
10.6 Waveguide junction circulators 215
10.7 Other Y-junction circulators 216
10.8 References 218
11 High-power and nonlinear effects 220
11.1 Spinwaves and magnetostatic waves 220
11.2 High-power devices 221
11.3 High-peak-power devices 224
11.4 Low-field loss 226
11.5 Power limiting 227
viii Contents
11.6 Frequency doubling 230
11.7 Amplification 232
11.8 References 233
12 Perturbation theory and measurements 235
12.1 Introduction 235
12.2 Perturbation theory for a cavity 236
12.3 Sample shape 240
12.4 Cavity measurement of dielectric properties 244
12.5 Cavity measurement of magnetic properties 246
12.6 Exact methods 250
12.7 Perturbation theory for waveguide 251
12.8 References 254
Appendixes 256
Appendix 1: Physical constants 256
Appendix 2: SI and Gaussian units 256
Appendix 3: Notation 257
Name index 260
Subject index 264
Preface
Between 1950 and 1965, there was a spate of intense activity to investigate the
theory and applications of ferrite materials at microwave frequencies. In the
early 1960s a number of workers wrote textbooks on the microwave applica-
tions of ferrites. Some books have been published subsequently which con-
centrate on particular microwave devices or specialise in one aspect of ferrites
at microwave frequencies, but it is now 20 years since any comprehensive
textbook on ferrites was published. The design of microwave ferrite devices has
become a mature technology and wideband isolators and circulators are readily
available for most microwave frequencies. However, new applications for ferrite
materials in stripline and microstrip and for millimetre wave frequencies are also
being investigated. There is the danger that each new generation of microwave
engineers will not know the very wide range of applications of microwave
ferrites that were investigated in the 1960s. A comprehensive book is needed to
consolidate all the investigations of ferrites for microwave applications in the
1960s, to look back at earlier publications from the view point of a mature
technology, and to bring the story up to date.
This book attempts to give all the structures and applications using ferrites
at microwave frequencies that have been investigated or contemplated. In a new
situation, an unlikely structure may be the one to use, for example, Faraday
rotation circulators and isolators have been used at millimetre wave frequencies
in the 1980s although in the late 1960s they appeared to be obsolescent and
replaced by the much smaller Y-junction circulators and resonant isolators for
use at normal microwave frequencies. Discussion is confined to electromagnetic
wave interaction with ferrite material. There is no attempt to discuss magneto-
static wave or spinwave devices or effects.
The book can be divided into two parts. After an introductory chapter about
the physics of magnetism and the chemistry of ferrites and garnets, the first part
of the book describes low-power ferrite devices in wveguide; the second part
looks at stripline devices and other microwave applications of ferrite material.
For the mature science of ferrite in free space and in waveguide, the exact theory
is given in Chapters 2, 3, 4, 6 and 12, and all likely applications of these
