Design of Nonplanar Microstrip Antennas and Transmission Lines

385 Pages·1999·22.31 MB·English

by  Kin-Lu Wong

Design of Nonplanar
Microstrip Antennas
and Transmission Lines
Design of Nonplanar
Microstrip Antennas
and Transmission lines
KIN-LU WONG
National Sun Yat-Sen University
A WILEY-INTERSCIENCE PUBLICATION
JOHN WILEY & SONS, INC.
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LibraryofCongressCataloging-in-PublicationData:
Wong,Kin-Lu.
Designofnonplanarmicrostripantennasandtransmissionlines/
Kin-LuWong.
p. cm.—(Wileyseriesinmicrowaveandopticalengineering)
“AWiley-Intersciencepublication.”
Includesbibliographicalreferencesandindex.
ISBN0-471-18244-3(cloth:alk.paper)
1.Striptransmissionlines–Designandconstruction.
2.Microstripantennas–Designandconstruction. I.Title.
II.Series.
TK7876.W65 1999
621.3810331—dc21 98-35003
PrintedintheUnitedStatesofAmerica.
10 9 8 7 6 5 4 3 2 1
Contents
ix
PREFACE
1
1 Introduction and Overview
1
1.1 Introduction
1.2 Cylindrical Microstrip Antennas 2
5
1.2.1 Full-Wave Analysis
1.2.2 Cavity-Model Analysis 6
1.2.3 Generalized Transmission-Line Model Theory 7
1.3 Spherical Microstrip Antennas 8
1.4 Conical Microstrip Antennas 10
1S Conformal Microstrip Arrays 11
1.6 Conformal Microstrip Transmission Lines 12
References 14
2 Resonance Problem of Cylindrical Microstrip Patches 16
2.1 Introduction 16
2.2 Cylindrical Rectangular Microstrip Patch with a Superstrate 17
2.2.1 Theoretical Formulation 17
2.2.2 Galerkin’s Moment-Method Formulation 24
2.2.3 Complex Resonant Frequency Results 26
2.3 Cylindrical Rectangular Microstrip Patch with a Spaced
Superstrate 30
2.3.1 Theoretical Formulation 30
2.3.2 Resonance and Radiation Characteristics 32
2.4 Cylindrical Rectangular Microstrip Patch with an Air Gap 35
2.4.1 Complex Resonant Frequency Results 36
vi CONTENTS
2.5 Cylindrical Rectangular Microstrip Patch with a Coupling Slot 37
2.5.1 Theoretical Formulation 39
2.5.2 Resonance Characteristics 43
2.6 Cylindrical Triangular Microstrip Patch 44
2.6.1 Theoretical Formulation 44
2.6.2 Complex Resonant Frequency Results 48
2.7 Cylindrical Wraparound Microstrip Patch 50
2.7.1 Theoretical Formulation 51
2.7.2 Complex Resonant Frequency Results 54
References 54
3 Resonance Problem of Spherical Microstrip Patches 56
3.1 Introduction 56
3.2 Spherical Circular Microstrip Patch on a Uniaxial Substrate 56
3.2.1 Fundamental Wave Equations in a Uniaxial Medium 57
3.2.2 Spherical Wave Functions in a Uniaxial Medium 59
3.2.3 Full-Wave Formulation for a Spherical Circular
Microstrip Structure 64
3.2.4 Galerkin’s Moment-Method Formulation 68
3.2.5 Basis Functions for Excited Patch Surface Current 69
3.2.6 Resonance Characteristics 70
3.2.7 Radiation Characteristics 73
3.2.8 Scattering Characteristics 75
3.3 Spherical Annular-Ring Microstrip Patch 77
3.3.1 Theoretical Formulation 78
3.3.2 Complex Resonant Frequency Results 83
3.4 Spherical Microstrip Patch with a Superstrate 83
3.4.1 Circular Microstrip Patch 83
3.4.2 Annular-Ring Microstrip Patch 89
3.5 Spherical Microstrip Patch with an Air Gap 94
3.5.1 Circular Microstrip Patch 94
3.5.2 Annular-Ring Microstrip Patch 96
References 101
4 Characteristics of Cylindrical Microstrip Antennas 103
4.1 Introduction 103
4.2 Probe-Fed Case: Full-Wave Solution 103
4.2.1 Rectangular Patch 108
4.2.2 Triangular Patch 112
CONTENTS vii
4.3 Probe-Fed Case: Cavity-Model Solution 113
4.3.1 Rectangular Patch 118
4.3.2 Triangular Patch 121
4.3.3 Circular Patch 124
4.3.4 Annular-Ring Patch 129
4.4 Probe-Fed Case: Generalized Transmission-Line Model
Solution 133
4.4.1 Rectangular Patch 133
4.4.2 Circular Patch 144
4.4.3 Annular-Ring Patch 147
4.5 Slot-Coupled Case: Full-Wave Solution 153
4.5.1 Printed Slot as a Radiator 155
4.5.2 Rectangular Patch with a Coupling Slot 165
4.6 Slot-Coupled Case: Cavity-Model Solution 168
4.6.1 Rectangular Patch 170
4.6.2 Circular Patch 176
4.7 Slot-Coupled Case: GTLM Solution 180
4.7.1 Rectangular Patch 180
4.7.2 Circular Patch 183
4.8 Microstrip-Line-Fed Case 184
4.9 Cylindrical Wraparound Patch Antenna 189
4.10 Circular Polarization Characteristics 191
4.11 Cross-Polarization Characteristics 196
4.11.1 Rectangular Patch 196
4.11.2 Triangular Patch 199
References 202
5 Characteristics of Spherical and Conical Microstrip Antennas 205
5.1 Introduction 205
5.2 Spherical Microstrip Antennas 205
5.2.1 Full-Wave Solution 206
5.2.2 Cavity-Model Solution 219
5.2.3 GTLM Solution 230
5.3 Conical Microstrip Antennas 234
References 239
6 Coupling between Conformal Microstrip Antennas 241
6.1 Introduction 241
6.2 Mutual Coupling of Cylindrical Microstrip Antennas 241
6.2.1 Full-Wave Solution of Rectangular Patches 241
6.2.2 Full-Wave Solution of Triangular Patches 246
. . .
VIII CONTENTS
6.2.3 Cavity-Model Solution of Rectangular Patches 251
6.2.4 Cavity-Model Solution of Circular Patches 257
6.25 GTLM Solution of Rectangular Patches 264
6.2.6 GTLM Solution of Circular Patches 268
6.3 Cylindrical Microstrip Antennas with Parasitic Patches 272
6.4 Coupling between Concentric Spherical Microstrip Antennas 280
6.4.1 Annular-Ring Patch as a Parasitic Patch 280
6.4.2 Circular Patch as a Parasitic Patch 283
References 284
7 Conformal Microstrip Arrays 286
7.1 Introduction 286
7.2 Cylindrical Microstrip Arrays 286
7.3 Spherical and Conical Microstrip Arrays 290
References 293
8 Cylindrical Microstrip lines and Coplanar Waveguides 294
8.1 Introduction 294
8.2 Cylindrical Microstrip Lines 294
8.2.1 Quasistatic Solution 295
8.2.2 Full-Wave Solution 299
8.3 Coupled Cylindrical Microstrip Lines 308
8.4 Slot-Coupled Double-Sided Cylindrical Microstrip Lines 315
8.5 Cylindrical Microstrip Discontinuities 324
8.5.1 Microstrip Open-End Discontinuity 324
8.5.2 Microstrip Gap Discontinuity 330
8.6 Cylindrical Coplanar Waveguides 335
8.6.1 Quasistatic Solution 336
8.6.2 Full-Wave Solution 342
References 353
Appendix A Curve-Fitting Formula for Complex Resonant
Frequencies of a Rectangular Microstrip Patch with
a Superstrate 356
Appendix B Modified Spherical Bessel Function 361
Appendix C Curve-Fitting Formula for Complex Resonant
Frequencies of a Circular Microstrip Patch with a
Superstrate 363
Index 369
Preface
Due to their conformal capability, research on nonplanar microstrip antennas and
transmission lines has received much attention. Many studies have been reported
in the last decade in which canonical nonplanar structures such as cylindrical,
spherical, and conical microstrip antennas and cylindrical microstrip transmission
lines have been analyzed extensively using various theoretical techniques. These
results are of great importance because from the research results of such curved
microstrip structures, the characteristics of general nonplanar microstrip antennas
and circuits can be deduced. The information can provide a useful reference for
working engineers and scientists in the design and analysis of microstrip antennas
and circuits to be installed on curved surfaces. Since the results are scattered in
papers in many technical journals, it is our intention in this book to organize the
research results on nonplanar microstrip antennas and circuits and provide an
up-to-date overview of this area of technology.
The book is organized in eight chapters. In Chapter 1 we present an
introduction and overview of recent progress in research on nonplanar microstrip
antennas and transmission lines and give readers a quick guided tour of subjects
treated in subsequent chapters.
In Chapters 2 and 3 we discuss, respectively, resonance problems inherent in
cylindrical and spherical microstrip patches. In addition to study of single-layer
microstrip patches of various shapes, structures related to microstrip patches with
an air gap for bandwidth enhancement or a spaced superstrate for gain improve-
ment are analyzed based on a full-wave formulation incorporating moment-method
calculations. From the formulation, the complex resonant frequencies of a curved
microstrip patches are solved whose real and imaginary parts give, respectively,
information on resonant frequency and radiation loss of a curved microstrip
structure. By comparison with results calculated from curve-fitting formulas for
complex resonant frequencies of planar rectangular and circular microstrip
patches, basic curvature effects on the characteristics of curved microstrip
structures can be characterized. In addition to the resonance problems discussed,
ix
X PREFACE
electromagnetic scattering from spherical circular microstrip patches is formulated
and analyzed. Uniaxial anisotropy in the substrate of a spherical microstrip
structure is included in the investigation.
Practical cylindrical microstrip patch antennas fed by coax or through a
coupling slot in the ground plane of a cylindrical microstrip feed line are analyzed
in Chapter 4. Various theoretical techniques, including the full-wave approach,
cavity-model analysis, and generalized transmission-line model (GTLM) theory,
are discussed in detail, and expressions of the input impedance and far-zone
radiated fields are presented and numerical results are shown. Experiments are also
conducted and measured data are shown for comparison. Circular polarization and
cross-polarization characteristics of microstrip antennas due to curvature variation
are also analyzed.
The results for microstrip antennas mounted on spherical or conical surfaces are
discussed in Chapter 5. For spherical microstrip antennas, formulations using the
different theoretical approaches of full-wave analysis, the cavity-model method,
and GTLM theory are described in detail. Both input impedance and radiation
characteristics due to the curvature variation are characterized. For conical
microstrip antennas, available studies are based primarily on the cavity-model
method. Related published results for nearly rectangular and circular wraparound
patches on conical surfaces are described and summarized.
Chapter 6 is devoted to coupling problems with cylindrical and spherical
microstrip array antennas. Mutual coupling coefficients between two microstrip
antennas mounted on cylindrical or spherical surfaces are formulated and
calculated. Bandwidth-enhancement problems of cylindrical and spherical micro-
strip antennas using gap-coupled parasitic patches are also discussed in this
chapter.
Conformal microstrip arrays are discussed in Chapter 7. A one-dimensional or
wraparound microstrip array mounted on a cylindrical body for use in omnidirec-
tional radiation is studied first. The curvature effect on the radiation patterns of
two-dimensional microstrip arrays is then formulated and investigated. A design in
the feed network to compensate for curvature effects on radiation patterns is also
shown. Several specific applications of spherical and conical microstrip arrays are
described.
Finally, in Chapter 8, characteristics of cylindrical microstrip lines are
discussed. Both quasistatic and full-wave solutions of the effective relative
permittivity and characteristic impedance of inside and outside cylindrical
microstrip lines are shown. Coupled coplanar cylindrical microstrip lines and
slot-coupled double-sided cylindrical microstrip lines are also studied. Cylindrical
microstrip open-end and gap discontinuities are formulated, and equivalent circuits
describing the microstrip discontinuities are presented. The characteristics of
cylindrical coplanar waveguides (CPWs) are solved using a quasistatic method
based on conformal mapping and a dynamic model based on a full-wave
formulation. Inside CPWs, outside CPWs, and CPWs in substrate-superstrate
structures are investigated.
The information contained in this book is largely the result of many years of