The Antenna Design Software

120 Pages·2002·5.84 MB·English

An Innovative Antenna Design Tool:
The Antenna Design Software
BY
Michael Sluter
A Thesis
in
The Department
of
Electrical Engineering
Presented in partial fùlfïUment of the requirements for the degree of
Master of Applied Science
Concordia University, Montreal
Quebec, Canada
May 200 1
O Mi ke S later, 200 1
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An lnnovative Antenna Design Tool:
The Antenna Design Software
Michael David Slater
Antenna design starts with a desired electrical performance, stating the minimum
gain, beamwidth andor other parameters, across a specified bandwidth. An antenna type
is chosen, and then trial-and-error is used to choose the dimensions. An initial set of
dimensions is used to find the antenna's performance, either by cornputer simulation or
by measurement. If the performance fails to meet the specification, the dimensions are
adjusted, and performance again found, the process is repeated until suitable dimensions
are found.
This thesis presents a realization of an antenna design zoo1 created with
MATLAB, called the Anrenna Design Sofiware. The Antenna Design Software cm be
used to study any antenna system that cm be designed using two primary geometrical
design parameters. The ADS effectively reverses the approach of antenna simulation
programs. The ADS accepts the desired electrical performance as the input then
determines al1 the possible combinations of geometrical dimensions that meet this
performance for one antenna type. There may be many possible sets of dimensions, or
conversely there may be no set of dimensions that rneets the required performance. The
thesis illustrates a repertoire of related antenna types, with databases for a simple helix
antenna, a helix tenninated with a matching section and a helix having a ground cup. The
power of the ADS can be greatly increased by developing a library of antenna types that
are then at the design engineer's fingertips.
Dedication
In this dedication 1 would like to acknowledge and thank al1 the people who
helped me to realize this thesis. There are so many people w ho contributed in their own
way that 1 am sure 1 will omit some narnes. To those people 1 apologize.
The first people 1 would like to thank are al1 the people who helped me achieve
my undergraduate degree. Without that, this thesis would never have existed. Thanks to
my schoolmates Ken Deegen, Les Raschkowen, Ted Obuchowicz, Don Davis, Iain
Bryson and al1 my fellow undergraduates from '95.
Thanks to dl my professors, notably Dr. Paknys, Dr. Landsberger, Dr. Ai-Khalili
and al1 the professors who helped me dong the way.
1 heartil y thank Pam Fox and David Gaudine h m t he EMC lab at Loyola for
their invaluable support and patience.
Thanks to my pareants, Jean & Chuck, and sisters, Judy & Adeie, for appreciating
my efforts and understanding my reclusiveness.
Thanks to my children Alexander, Ryan and Madeleine. "Daddy's coming
home!".
Thanks to Dr. Stan Kubina for providing the environment, opportunity and
encouragement for me to pursue a graduate degree.
Thanks to my mentor and partner, Dr. Trueman. Your insight, encouragement and
belief in my abilities have helped us contribute a practical and innovate tool for antenna
designers. We started with a small seed and it blossomed into this thesis. 1 am pteful.
Last but not least 1 thank my wife Lesley, the thesis widow. Your [ove,
encouragement and support have been the foundation this thesis was built on. 1 love you.
.............................................................................................
Table of Contents v
1. The Antenna Design Roblem .................................. .. ......................... 1
1.1 Introduction ...................... ... .......................................................................... 1
............................ .. ..........*....................
1.2 Two-Parameter Anienna Systems 6
1.2.1 The Cylindrical Helix Antenna .......................... .. .............................. 6
1.2.2 The Two Dipole Array ............................................................................ 7
1.3 Antenna Specifications ...................................................................................... 8
.....................................................................................
1.4 Overview of the Thesis 9
................ ....... . ...............................
The Antenna Design Software 11
.....................................................................................................
2.1 Introduction 11
2.2 The Design Window ......................................................... ... ............................ 12
...............................................................................................
2.3 Design Controls 13
................................................................................
2.4 The Operational Controls 14
............................................................................
2.4.1 The Check Pushbutton 14
...............................................................................
2.4.2 The Exit Pushbutton 15
.....................................................................
2.4.3 The Freq-Plots Pushbutton 15
2.5 Display Controls. .............................................................................................1 7
........................................................................
2.5.1 The Contour Pushbutton 17
...........................................................................
2.5.2 The Movie Pushbutton 19
......................................................................................
2.6 Database Controt 2 0
............................................................................................
2.7 Menu Bar Control 20
2.7.1 Resolution Control. .................................................................................2 0
3 . Cylindrical Helix Antemas ................................................................ 22
3.1 Introduction ................................................................................................... 22
..............................................................................
3.2 Simple Cylindrical Helices 23
3.3 Complex Helix Antennas ................................................................................ 30
....................................................................................
3.4 Matching sections 3 1
3.5 Ground Systems .................................................. .. ...................................... 33
..........................................................................
3.5.1 Infinite Ground Plane 3 4
...........................................................................................
3.5.2 GroundDisk 35
............................................................................................
3.5.3 Ground Cup 36
3.5.4 Including a Ground System in the ADS Database ................................. 36
3.6 Helical Antenna Design using Parametric Design Curves ............................. . 37
.........................................................................................................
3.7 Surnrnary 41
. .........................................
4 Building the ADS Database
4.1 Introduction ...................................... ................... 4 2
.-
...............................................
4.2 The Numerical Electromagnetics Code (NEC) 42
4.3 Modelling a Helix Antenna .......................................................................... 46
4.4 Frequency Scaling ........................................................................................ 49
4.5 Creating the Database for the Helix Above Perfect Ground ......................... 52
4.6 Database Structure. ...................................................................................... 5 3
4.7 Sumrnary ......................................................................................................... 54
....................... ... ............. . ................................
How The ADS Works -55
....................................................................................................
5.1 Introduction 5 5
....................................................
5.2 Design Window & Performance Metrics 5 5
5.3 The Database ................... .. .......................................................................... 56
5.4 Interpolation .................................................................................................... 58
5.5 Frequenc y Range .............. .... .................................................................. 5 9
5.6 Finding the Solution Space ............................................................................. 59
................................................................
5.7 Contour Maps and Frequency Plots 61
5.8 Summary .................................... .... ................................................................. 62
6 . Helix Antenna Design Using The ADS ........................... .... ............. -63
6.1 Introduction .................................................................................................. 63
6.2 A Simple Design Exarnple .............................................................................. 64
6.2.1 Gain. Axial Ratio and Bearnwidth Contour Maps ............... .. .............. 65
6.2.2 Frequency Plots ...................................................................................... 67
6.3 Exploring the Limiting Factors ................................................................ 6 9
6.4 Choosing a Specific Design ........................................................................... 71
6.5 A Simple Design Example Revisited .............................................................. 71
6.6 Developing a Performance Specification with the ADS ................................. 73
6.6.1 Applying the ADS .................................................................................. 74
6.7 Design Choices ............... .. ..........................................................................8 0
6.8 Sununary ......................................................................................................... 81
7. User Databases: Helix Antema With A Ground Cup ........................ 82
...................................................................................................
7.1 Introduction 8 2
..............................................................................
7.2 The Standard Ground Cup 8 2
7.3 Creating the Database. ..................................................................................... 83
.........................................................................
7.4 A Simple Design Cornparison 84
7.5 A Compiex Design Cornparison ..................... ....... . ..................................... 86
7.6 Summary .........................................................................................................8 7
8 . The ADS Applied To Another Two-Parameter Antenna Sy stem .......8 8
.....................................................................................................
8.1 Introduction 88
................................................................................
8.2 The Performance Metrics 89
8.3 Creating the Database ............... .... ..................................................... 9 0
.............................................................................................
8.4 An Initial Design 91
...............................................................................................
8.5 The Refinement 93
8.5.1 Bandwidth Refinement .......................................................................... 94
8.5.2 Beamwidth Refinement ......................... .... ..................................... 9 4
...............................................................................
8.5.3 Gain Refinement 9 6
8.6 Final Design .................................................................................................... 98
8.7 Summary ......................................................................................................... 99
9 . Conclusion ......................................................................................... 100
................. ........ ..........................................................................
9.1 Introduction 100
............................................................
9 Recommendations For Further Work 103
......................................................................
9.2.1 Stand Alone Application 103
9.2.2 Database Support ....................................... . .......................................... 103
...................................................................................
9.2.3 Database Library 104
............
9.2.4 Optimizing The Data-Grid Density For The Database Library 104
.................... ... .....
9.2.5 Increasing The Number of Performance Metrics 105
.................................................................
9.2.6 Three Parameter Simulation 105
9.2.7 User Dialogs ...... ................ . ........................................................... 106
9.3 Summary ....................................................................................................... 106
...................................................................................................
References 107
......................................................................................................
Glossary 1 10
List of Figures and Tables
Figure 1. 1 : Traditional Design-Performance Relationship. .......................................... 3
Figure 1-2: The Design Space Region .......................................................................... 5
Figure 1-3: The Simple Cylindrical Helix Geometry. . ................. . ....................... 6
Figure 1-4: Geornetry for a Two-Dipole Array with Reflectors. .................................. 7
Figure 1-5: Subset Relationship for the ADS Input-Otput. ............. .. ................ 8
Figure 2- 1: The Generalized Design Window ........................................................ 13
Figure 2-2: A Design Window for a Genenc Antenna. ..................................... . . . 1 4
Figure 2-3: The Solution Space for a Genenc Antenna. ............................................. 15
Figure 2-4: The Generalized Frequency Plot Window ...................................... . . .1 6
Figure 2-5: Frequency Plot Window for the Genenc Antenna .......................... ......... 17
Figure 2-6: 1000 MHz View Frequency Contour Plots .................... ..........,.... ........ 18
Figure 2-7: 1000 MHz View Frequency Contour Plots & Solution Space ........ .. ....... 18
..........................................
Figure 2-8: Contour Movie Window for a Helix Antenna 19
Figure 2-9: Resolution Control Menu and Pop-Up Window ........................... .. ...... 20
Figure 3-1 : The Simple Cylindrical Helix Geometry. ..................... .. ................. 2 4
Figure 3-2: Axial-Mode Radiation of the Helix Antenna .......................................... 25
........................................
Figure 3-3: Normal-Mode Radiation of the Helix Antenna 26
Figure 3-4: Performance Metrics: Axial Ratio and Beamwidth ........................ ......... 27
........................... .. ..........
Figure 3-5: The Operation Regions for a Helical Antenna 28
Figure 3-6: Cornplex Helix Antennas ......................................................................... 31
........................
Figure 3-7: A Cylindncal Helix with the Standard Matching Section 33
Figure 3-8: Helix Antenna Ground Systems. .............................................................. 34
Figure 3-9: The Design Process Steps. ....................................................................... 38
Figure 4-1 : Procedure used to Create the Helix Database. ........ . ................................ 48
...................................................
Figure 4-2: Directive Gain Scaling Comparison 5 1
Figure 4-3: Axial Ratio Scaling Cornparison ............................................................. 52
Table 4- 1: The ADS Database Fi le Format ................................................................ 5 3
Table 4-2: The Helix Database File Format ................................................................ 53
Figure 5- 1: One Database Frequency Page ............................................................. 5 6
Figure 5-2: The ADS Database of Frequency Pages ................... ... ...................... 57
Figure 6-1: Design Window & Solution Space for Example 1. ......... . .................... .... 65
Figure 6-2: Contour Maps for Exarnple 1. .................................................................. 66
.........................................
Figure 6-3: 12.5" 18-Tum Frequency Plots for Example 1 67
Figure 6-4: 1l .SO1 4-Tum Frequency Plots for Exampie 1. ....................... ... ......... 68
...................
Figure 6-5: Gain Contours at 850 MHz View Frequency for Example 1 69
Figure 6-6: Beamwidth Contours at 11 50 MHz View Frequency for Example 1. ..... 70
viii
Figure 6-7:D esign Window & Solution Space for Exarnple 2 ................................... 72
Figure 6-8:F requency Plots for Example 2 ................................................................ 73
Figure 6-9: Design Window and Solution Space for Example 3. ............................... 75
Figure 6-1 0: Design Window & Solution Space for a Refined Specification. ........... 75
Figure 6-11 : Gain & Bearnwidth Contours for a Refined Specification. .................... 76
Figure 6-12: Solution Space for the Axial Ratio Refinement. .................................... 77
Figure 6-13:B eamwidth Contours with Axial Ratio Refinement. ............... ....... 78
Figure 6-14:D iscrete Gain Contours for the Beamwidth Refinement ....................... 79
Figure 6-15 : Solution Space & Frequency Plots for the Final Design .............. .. ..... 80
Figure 7-i:C ylindrical Helix with the Standard Ground Cup. ................................... 83
Figure 7-2:D atabase Menu in the Design Window .............. .. .................................. 84
Figure 7-3: Solution Space Cornparison 1. ............................................................... 85
Figure 74: Solution Space Cornparison 2 ................................................................. 86
Figure 8-1 : Geometry for a Two-Dipole Array with Reflectors. ................................ 88
Figure 8-2: Design Window for Dipole Array & Reflectors. ................................... 90
.....................
Figure 8-3:D esign Window and Solution Space for the Initial Design 92
Figure 84: Frequency Plot and Solution Space for H = 0.295A, S = 0.17h. .............. 92
Figure 8-5: Frequency Plot and Solution Space for H = 0.291Â, S = 0.195h. ............ 93
Figure 8-6: Contour Plots at 10 MHz ...................................................................... 95
Figure 8-7:B earnwidth Contour at 8 MHz ................................................................. 96
Figure 8-8: Gain Refinement Contour Plots ............................................................... 97
Chapter 1
The Antenna Design Problem
1.1 Introduction
It is not uncommon for an antenna engineer to have a complete vision of the
performance required from an antenna in order to solve a specific transmission problem.
The antenna engineer intuitively knows how the antenna should perfonn over a given
frequency range. That is, the antenna must achieve a certain directive gain andor have a
specific beamwidth. An acceptable range of values for each performance metric, such as
the gain and beamwidth, is fonnulated and defines the b4performan~spee cification"'. The
antenna engineer can visualize this desired performance but may not know of an antenna
type that achieves these goals. The antenna engineer's task is to choose an antenna type
that can meet the desired electrical performance requirements as well as satisQ other
considerations such as physical and cost restrictions. There may be several antenna types
that are able to satisfy the desired performance specification. An experienced engineer
has some insight into antenna charactenstics required to solve the problem and with a
Iittle research the antenna engineer will choose an antenna type. Once an antenna type is
selected the objective is to identify the antenna dimensions, the "design specification",
that achieve the required performance specification. The antenna engineer may use a
"simulation tool", which is a computational software program that calculates the
electrical performance of an antenna, for a given set of dimensions. An alternate method
is to build physical models and mesure their performance to arrive at a design
'
This terrn and others are used in a specid sense and their definitions can be found in the glossary at the end of the
thesis.