Small Antenna Design

303 Pages·2006·1.91 MB·English

by  Douglas B. Miron

Small Antenna Design
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Small Antenna Design
by Douglas B. Miron, Ph.D.
AMSTERDAM(cid:1) BOSTON(cid:1) HEIDELBERG (cid:1) LONDON
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ISBN-13: 978-0-7506-7861-2
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I dedicate this work to my mother,
Florence Ethel Coolidge.
She gave me love, liberty, and a backbone.
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Contents
Preface........................................................................................xi
About the Author .......................................................................xiii
What’s on the CD-ROM?.............................................................xv
Chapter 1: Introduction.................................................................1
1.1 What Is Small?..................................................................................................1
1.2 What Are the Problems?...................................................................................2
1.3 Some Historical Small Antenna Types and Applications..................................2
1.4 Some Present and Future Small Antennas........................................................5
References...............................................................................................................8
Chapter 2: Antenna Fundamentals I ...............................................9
2.1 Electromagnetic Waves.....................................................................................9
2.1.1 Waves in Space...............................................................................11
2.1.2 Waves in Transmission Lines..........................................................14
2.1.3 Power in Waves...............................................................................18
2.2 Polarization.....................................................................................................20
2.3 The Short Dipole.............................................................................................23
2.3.1 Radiation Pattern.............................................................................24
2.3.2 Circuit Behavior..............................................................................28
2.4 The Small Loop...............................................................................................31
2.4.1 Circuit Behavior..............................................................................32
2.5 Directionality, Efficiency, and Gain................................................................35
References.............................................................................................................37
Chapter 2 Problems...............................................................................................38
Chapter 3: Antenna Fundamentals II ............................................43
3.1 Bandwidth and Quality Factor, Q...................................................................43
3.2 Impedance Matching and System Efficiency..................................................51
3.2.1 Narrow-Band Matching..................................................................52
3.2.2 Wideband Matching........................................................................53
3.2.3 System Efficiency...........................................................................55
3.3 Reception........................................................................................................56
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Contents
3.3.1 Effective Height..............................................................................57
3.3.2 Effective Area.................................................................................58
3.3.3 Reception Pattern............................................................................58
3.4 Ground Effects................................................................................................59
3.4.1 Image Theory..................................................................................59
3.4.2 Vertical Dipole Above a Perfect Ground Plane...............................60
3.4.3 Horizontal Dipole Above a PEC Plane...........................................63
3.4.4 Grounded-Source Antennas............................................................66
3.4.5 Counterpoise...................................................................................67
3.4.6 Summary of Ground Effects...........................................................68
3.5 Improvements.................................................................................................68
References.............................................................................................................69
Chapter 3 Problems...............................................................................................71
Chapter 4: Introduction to Numerical Modeling of Wire Antennas....75
4.1 General Concepts............................................................................................75
4.2 The Mathematical Basics of the Numerical Electromagnetic
Code (NEC)...................................................................................................77
4.2.1 Basis Functions...............................................................................79
4.2.2 Applied Field Models.....................................................................88
4.2.3 Solving the Integral Equation.........................................................91
4.3 Using NEC in the Command Window............................................................92
4.4 Modeling Guidelines.......................................................................................99
4.5 NEC in a Graphical User Interface (GUI)....................................................103
4.6 Examples from Chapters 2 and 3..................................................................105
4.6.1 The Short Dipole...........................................................................105
4.6.2 Small Loop in Free Space.............................................................106
4.6.3 End-Loaded Short Dipole.............................................................108
References...........................................................................................................109
Chapter 4 Problems.............................................................................................110
Chapter 5: Programmed Modeling..............................................113
5.0 Introduction...................................................................................................113
5.1 Using Wire-List Generators in NEC.............................................................113
5.2 Using Code to Generate a Wire List.............................................................118
Chapter 5 Problems.............................................................................................131
Chapter 6: Open-Ended Antennas..............................................133
6.0 Introduction...................................................................................................133
6.1 Thick Monopoles..........................................................................................135
6.1.1 Modeling Thick Monopoles..........................................................136
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Contents
6.2 Top Loading..................................................................................................140
6.2.1 The Inverted-L..............................................................................140
6.2.2 Top-Loading with Radials.............................................................146
6.2.3 Volume Loading............................................................................149
6.3 Coil Loading.................................................................................................152
6.4 Using Resonance...........................................................................................165
6.5 Summary.......................................................................................................172
References...........................................................................................................174
Chapter 6 Problems.............................................................................................175
Chapter 7: Loops and Other Closed-Wire Antennas......................179
7.0 Introduction...................................................................................................179
7.1 Thick Loops..................................................................................................180
7.1.1 The Doughnut...............................................................................180
7.1.2 The Barrel Loop............................................................................185
7.2 Solenoid Antennas........................................................................................194
7.3 The Contrawound Toroidal Helix Antenna (CTHA)....................................198
7.4 The Folded Spherical Helix Monopole.........................................................202
7.5 Final Comments............................................................................................205
References...........................................................................................................206
Chapter 7 Problems.............................................................................................207
Chapter 8: Receiving Antennas...................................................211
8.0 Introduction...................................................................................................211
8.1 External Noise...............................................................................................212
8.2 The Ferrite Rod Antenna...............................................................................213
8.2.1 Antenna Parameters......................................................................214
8.2.2 Circuit Applications......................................................................219
8.3 Active Receiving Antennas...........................................................................223
8.3.1 The Active Whip...........................................................................224
8.3.2 The Active Loop...........................................................................225
8.3.3 General Considerations.................................................................225
References...........................................................................................................230
Chapter 8 Problems.............................................................................................231
Chapter 9: Measurements .........................................................235
9.1 What Are You Measuring?............................................................................235
9.2 Measurements Through a Transmission Line...............................................236
9.2.1 If I Only Have an SWR Meter......................................................237
9.2.2 Impedance Measured Through a Transmission Line....................239
9.3 Ranges and Test Enclosures..........................................................................240
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