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Ohio大牛批判负折射的书
Munk_Metamaterial_critique and alternatives.pdf
BEN A. MUNK
Professor of Electrical Engineering, Emeritus
The Ohio State University
Life Fellow IEEE
This book is dedicated to true science.
The constant support of the ElectroScience Laboratory and my
family—in particular my wife, Aase—is deeply appreciated.
CONTENTS
Foreword xiii
Preface xv
1 Why Periodic Structures Cannot Synthesize Negative
Indices of Refraction 1
1.1 Introduction 1
1.1.1 Overview 1
1.1.2 Background 2
1.2 Current Assumptions Regarding Veselago’s Medium 2
1.2.1 Negative Index of Refraction 2
1.2.2 Phase Advance when n1 <0 3
1.2.3 Evanescent Waves Grow with Distance for
n1 <0 3
1.2.4 The Field and Phase Vectors Form a Left-Handed
Triplet for n1 <0 3
1.3 Fantastic Designs Could Be Realized if Veselago’s Material
Existed 5
1.4 How Veselago’s Medium Is Envisioned To Be Synthesized
Using Periodic Structures 6
1.5 How Does a Periodic Structure Refract? 9
1.5.1 Infinite Arrays 9
1.5.2 What About Finite Arrays? 15
1.6 On the Field Surrounding an Infinite Periodic Structure
of Arbitrary Wire Elements Located in One or More
Arrays 16
1.6.1 Single Array of Elements with One Segment 16
1.6.2 Single Array of Elements with Two Segments 18
1.6.3 Single Array of Elements with an Arbitrary Number
of Segments 19
1.6.4 On Grating Lobes and Backward-Traveling Waves
20
1.6.5 Two Arrays of Elements with an Arbitrary Number
of Segments 21
vii
viii CONTENTS
1.6.6 Can Arrays of Wires Ever Change the Direction
of the Incident Field? 23
1.7 On Increasing Evanescent Waves: A Fatal Misconception
23
1.8 Preliminary Conclusion: Synthesizing Veselago’s Medium
by a Periodic Structure Is Not Feasible 24
1.9 On Transmission-Line Dispersion: Backward-Traveling
Waves 26
1.9.1 Transmission Lines 26
1.9.2 Periodic Structures 30
1.10 Regarding Veselago’s Conclusion: Are There Deficiencies?
32
1.10.1 Background 32
1.10.2 Veselago’s Argument for a Negative Index
of Refraction 32
1.10.3 Veselago’s Flat Lens: Is It Really Realistic? 34
1.11 Conclusions 35
1.12 Common Misconceptions 38
1.12.1 Artificial Dielectrics: Do They Really Refract?
38
1.12.2 Real Dielectrics: How Do They Refract? 40
1.12.3 On the E- and H-Fields 41
1.12.4 On Concentric Split-Ring Resonators 42
1.12.5 What Would Veselago Have Asked if . . . 42
1.12.6 On “Magic” Structures 43
References 44
2 On Cloaks and Reactive Radomes 47
2.1 Cloaks 47
2.1.1 Concept 47
2.1.2 Prior Art 47
2.1.3 Alternative Explanation 48
2.1.4 Alternative Design 50
2.1.5 What Can You Really Expect from a Cloak? 50
2.2 Reactive Radomes 51
2.2.1 Infinite Planar Array with and Without Reactive
Radome 51
2.2.2 Line Arrays and Single Elements 54
2.3 Common Misconceptions 55
2.3.1 Misinterpretation of Calculated Results 55
CONTENTS ix
2.3.2 Ultimately: What Power Can You Expect from a
Short Dipole Encapsulated in a Small Spherical
Radome? 56
2.4 Concluding Remarks 57
References 58
3 Absorbers with Windows 61
3.1 Introduction 61
3.2 Statement of the Problem 61
3.3 Concept 62
3.4 Conceptual Designs 63
3.5 Extension to Arbitrary Polarization 66
3.6 The High-Frequency Band 66
3.7 Complete Conceptual Rasorber Design 67
3.8 Practical Designs 69
3.9 Other Applications of Traps: Multiband Arrays 69
Reference 70
4 On Designing Absorbers for an Oblique Angle
of Incidence 71
4.1 Lagarkov’s and Classical Designs 71
4.2 Salisbury Screen 74
4.3 Scan Compensation 76
4.4 Frequency Compensation 77
4.5 Circuit Analog Absorbers 80
4.6 Other Designs: Comparison and Discussion 85
4.7 Conclusions 89
References 91
5 The Titan Antenna: An Alternative to Magnetic Ground
Planes 93
5.1 Introduction 93
5.2 Layout of the Antenna 94
5.3 On Double-Band Matching in General 96
5.4 Matching the Sleeve Elements 97
5.5 Further Matching: The Main Distribution Network 101
5.6 The Balun 103
5.7 The Radiation Pattern 104
5.8 Something that Sounds Too Good To Be True Usually Is
106
x CONTENTS
5.9 Efficiency Measurements 108
5.10 A Common Misconception 108
5.11 We Put the Magnetic Ground Plane to Rest 109
5.12 Conclusions 112
References 113
6 Summary and Concluding Remarks 115
6.1 Background 115
6.2 The Features of Veselago’s Material 116
6.3 What Can a Periodic Structure Actually Simulate? 117
6.4 Did Veselago Choose the Wrong Branch Cut? 118
6.5 Could We Ever Have a Negative Index of Refraction?
118
6.6 Could Veselago Have Avoided the Wrong Solution? 120
6.7 So What Came Out of It? 121
6.8 Is Publishing the Ultimate Goal in Scientific Research?
122
6.9 What Excites a Scientist? 122
6.10 How Far Have We Gone in Our Self-Deception? 124
6.11 But Didn’t Anyone Suspect Anything? 124
6.12 How Realistic Are Small Arrays? 125
References 126
Appendix A The Paper Rejected in 2003 129
A.1 Comments Written in 2007 Concerning My Rejected
Paper Submitted in 2003 129
A.2 The Paper Rejected in 2003 131
Appendix B Cavity-Type Broadband Antenna with a
Steerable Cardioid Pattern 149
B.1 Introduction 149
B.2 Design 1 149
B.3 Design 2 151
B.4 Development of Design 2b 154
B.4.1 Push–Push Traps 157
B.4.2 Actual Layout 158
B.4.3 Phase Reversal in the Balun 160
B.4.4 Final Execution of Design 2b 162
B.4.5 Radiation Pattern 162
B.4.6 Impedance 165
CONTENTS xi
B.5 Conclusions 165
References 166
Appendix C How to Measure the Characteristic Impedance
and Attenuation of a Cable 167
C.1 Background 167
C.2 Input Connector Effect 170
C.3 Do the Formulas Hold in the Smith Charts? 171
C.4 How to Measure the Cable Loss 171
Reference 173
Appendix D Can Negative Refraction Be Observed Using
a Wedge of Lossy Material? 175
D.1 Introduction 175
D.2 Refraction for Planar Slabs 175
D.3 Wedge-Shaped Dielectric 179
D.4 Asymmetric Aperture Distributions in General 181
D.5 Conclusions 181
References 184
Index 185
FOREWORD
Science has always been plagued by occasional hype or misdirected work,
witness the N-ray of a previous century that purported to image soft tissues.
Unsupported science has appeared in force in recent years in the area
of negative parameter materials: for example, “perfect lenses” that cannot
produce a usable modulation transfer function and may not even satisfy
the standard lens equations. And electrically small antennas enclosed in
an NIM (negative index material) shell, “produce a larger voltage”—not
a word is said about efficiency, directivity, or bandwidth. These shells
have not been constructed or simulated (except in infinite arrays, using a
waveguide simulator), and probably never will be, due to mutual interactions
inside the shell. Another example is negative refraction through
an NIM wedge, where the output beam amplitude shown is normalized
to equal that of an equivalent dielectric wedge, even though the very
large attenuation (due to the reflection coefficient) might yield new physical
understanding. Good science would make measurements of beam shift
through a slab, where reflection losses are minimized—but no microwave
slab measurements have been made. Much government money is supporting
these NIM projects, but the contract monitors are not exercising the
careful and skeptical overview that good science requires. Unfortunately,
the NIM authors have tried to make NIM synonymous with metamaterials,
the latter term being much broader.
It is important to get a scientific dialogue going; to date the dialogue
has been largely one-sided, due to biased journal editorial boards. Professor
Munk is initiating a dialogue, with an emphasis on a periodic
structure approach, for which he has been a major contributor over many
years. Some of the NIM phenomena observed are probably due to surface
waves and leaky waves. In his book Wave Propagation and Group Velocity,
Brillouin shows that signal velocity and group velocity are different
for a dispersive medium. Munk reports that the signal velocity always
refracts positively, even in an NIM. Almost all of the NIM papers talk
about group velocity, but it is really signal velocity that is critical for any
practical system. Munk has also been a major contributor to various stealth
xiii
xiv FOREWORD
projects, including absorbers and frequency-selective surfaces. Much of
this is explained via Smith charts; he shows that use of these can provide
a physical understanding of many complex phenomena.
It is hoped that those responsible for allocating U.S. government
research money will find this book useful.
R. C. Hansen |
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