New frequency reconfigurable antennas for wide frequency range tuning

236 Pages·2017·39.69 MB·English

UNIVERSITY COLLEGE LONDON
New frequency reconfigurable antennas
for wide frequency range tuning
by
Cristina Borda Fortuny
A thesis submitted for the degree of
Doctor of Philosophy
in the
Faculty of Engineering Science
University College London
Supervised by Dr Kenneth Tong and Dr Kevin Chetty
March 2017
Declaration of Authorship
I, Cristina Borda Fortuny, declare that this thesis titled, ‘New frequency reconfigurable
antennasforwidefrequencyrangetuning’andtheworkpresentedinitaremyownorigi-
nalworkandthatallsourcematerialusedhasbeenclearlyidentifiedandacknowledged.
No part of this dissertation contains material previously submitted to the examiners of
this or any other university, or any material previously submitted for any other exami-
nation.
Signed:
Date:
1
“All truths are easy to understand once they are discovered;
the point is to discover them”
- Galileo Galilei
UNIVERSITY COLLEGE LONDON
Abstract
by Cristina Borda Fortuny
Frequency reconfigurable antennas are becoming a compelling solution for the increas-
ing demand of higher antenna capabilities, since they can operate at tunable narrow
frequency bands while rejecting the undesirable signals from other bands. The aim of
thisprojectistodevelopnewdesignsforfrequencyreconfigurableantennasthatcanwork
acrossawidefrequencyrange(from1GHzupto6GHz)whilemaintainingstableradia-
tionpatternandpolarisationasrequiredbytheindustrysponsors. AVivaldiantennais
consideredasthebasisforafrequencyreconfigurabledesignasitmaintainstheradiation
characteristics in its operating band. Dual-band, tri-band and quad-band switched re-
configurabledesignsareproposedandanalysed. Theseantennasareelectronically-tuned
using RF switches which adjust the impedance to reconfigure the operating band of the
antenna. A prototype is tested in an anechoic chamber obtaining good performance.
However, as the switches lead to several challenges, such as the e↵ect of bias lines and
the excessive insertion losses, a new approach is taken. State-of-the-art technologies
are studied and fluid antennas are introduced. Current developments show that liquid
antennas can have radiation e�ciencies up to 90 % and conductivities close to copper,
which makes them a good candidate to fulfil the requirements of this project. A hybrid
Vivaldi antenna with an ionised water switch is proposed and a prototype tested. By
introducing ionised water into a specific point of the feed line the operating frequency
oftheantennaisadjusted. ThereplacementofRFswitchesforelectronically-controlled
fluids brings high flexibility, suppression of the bias lines impact, dynamic adjustment
and continuous frequency tuning compared to conventional antenna systems.
Acknowledgements
I would like to express my sincere gratitude to my first supervisor Dr Kenneth Tong
and my second supervisor Dr Kevin Chetty for their constant support, guidance and
motivation.
I cannot forget the valuable help and motivations of the Radar Group colleagues and
the professors in the Friday seminars and co↵ee breaks.
Thanks to the funding bodies of this research project: EPSRC UK and L-3 TRL Tech-
nology.
I am very grateful for the support and good times given by my family and friends even
fromfaraway. ParticularlytoJordi,Anna,SandraandJianling. ToPaula,agoodfriend
who never stops amazing me. And to Joan, my mentor, who convincingly conveyed a
spirit of adventure in regard to research.
Finally, a special thanks to Xavi for his love, encouragement and support that were
essential to carry out this thesis.
4
List of publications
A list of relevant publications that were produced by the work described in this thesis
is presented here:
(1) C. Borda Fortuny, K. F. Tong, K. Chetty, D. M. Benton, “High-gain frequency
reconfigurable Vivaldi antenna”, IEEE International Symposium on Antennas and
Propagation 2014, Memphis (USA)
(2) C. Borda Fortuny, K. F. Tong, K. Chetty, P. Brittan, “High-gain triple-band
reconfigurable Vivaldi antenna”, IEEE-APS Topical Conference on Antennas and
Propagation in Wireless Communications 2014, Aruba
(3) A.Amiri, C. Borda Fortuny, K.F.Tong, “Reconfigurableantennasforverywide
spectrum monitoring”, 2014 IEEE International Workshop on Electromagnetics,
Sapporo (Japan)
(4) C. Borda Fortuny, A. Amiri, K. F. Tong, “Development of reconfigurable mul-
tiple wideband antenna for radar and monitoring applications”, The 9th European
Conference on Antennas and Propagation, EuCAP 2015, Lisbon (Portugal)
(5) K. F. Tong, C. Borda Fortuny, J.Bai, “Low cost 3D-printed monopole fluid an-
tenna”,InternationalSymposiumonAntennasandPropagation,ISAP2015,Hobart
(Australia)
(6) H. Li, C. Borda Fortuny, K. F. Tong, K. K. Wong, “Coupling-fed frequency
agile monopole fluid antenna”, 2016 IEEE International Conference on Antenna
Measurements & Applications Focus on Antenna Systems, Syracuse (USA)
(7) C. Borda Fortuny, K. F. Tong, K. Chetty, K. K. Wong, “Comparison between
a Novel Liquid Switch and a GaAs MMIC Switch for Reconfiguring the Operating
Frequency of a Vivaldi Antenna”, 2017 IEEE International Workshop on Electro-
magnetics, London (UK)
(8) C. Borda Fortuny, K. F. Tong, K. Chetty, “A low-cost mechanism to reconfigure
the operating frequency band of a Vivaldi antenna for cognitive radio and spec-
trum monitoring applications”, IEEE Transactions on Antennas and Propagation,
(Submitted on 13th March 2017)
5
6
(9) C. Borda Fortuny, K. F. Tong, K. Chetty, “A novel liquid-switched to reconfig-
ure the operating frequency of a Vivaldi antenna”, IEEE Antennas and Wireless
Propagation Letters, (In preparation)
(10) C. Borda Fortuny, H. Li, K. F. Tong, K. K. Wong, “A low-cost fluid monopole
antennaforcontinuousfrequencytuning”,IEEEAntennasandWirelessPropagation
Letters, (In preparation)
Contents
Declaration of Authorship 1
Abstract 3
Acknowledgements 4
List of publications 5
List of Figures 13
List of Tables 24
Abbreviations 26
Symbols 29
1 Introduction 35
1.1 Aim and objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1.3 Research contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
1.4 The scientific method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
7
Contents 8
1.5 Thesis Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2 Background theory 44
2.1 Antenna parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.1.1 Field regions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.1.1.1 Reactive Near-field. . . . . . . . . . . . . . . . . . . . . . 45
2.1.1.2 Radiating Near-field (Fresnel) . . . . . . . . . . . . . . . 46
2.1.1.3 Far-field (Fraunhofer) . . . . . . . . . . . . . . . . . . . . 46
2.1.2 Reflection coe�cient . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.1.3 Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.1.4 E�ciency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.1.5 Directivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
2.1.6 Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
2.1.7 Radiation pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.1.8 Polarisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
2.1.9 Phase Centre . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
2.2 Operating frequency against size . . . . . . . . . . . . . . . . . . . . . . . 60
2.3 Classification by geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
2.3.1 Wire antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
2.3.2 Aperture antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
2.4 Resonant antennas and travelling wave antennas . . . . . . . . . . . . . . 62
2.4.1 Resonant antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
2.4.2 Travelling wave antennas . . . . . . . . . . . . . . . . . . . . . . . 64
2.5 UWB antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Contents 9
2.5.1 Advantages and disadvantages . . . . . . . . . . . . . . . . . . . . 65
2.5.2 UWB antenna parameters . . . . . . . . . . . . . . . . . . . . . . . 66
2.5.3 Vivaldi antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
2.6 Reconfigurable antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
2.6.1 Importance of reconfigurable antennas . . . . . . . . . . . . . . . . 70
2.6.2 Applications of reconfigurable antennas . . . . . . . . . . . . . . . 71
2.7 Summary of chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
3 Literature review 73
3.1 Frequency reconfigurable antennas . . . . . . . . . . . . . . . . . . . . . . 74
3.1.1 Discrete tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
3.1.1.1 Bias lines . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
3.1.2 Continuous tuning . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
3.1.3 Reconfiguration combining switching and continuous tuning . . . . 81
3.2 Antennas with reconfigurable polarisation . . . . . . . . . . . . . . . . . . 82
3.3 Radiation pattern reconfigurable antennas . . . . . . . . . . . . . . . . . . 85
3.4 RF switches comparison summary . . . . . . . . . . . . . . . . . . . . . . 89
3.5 Reconfigurable Vivaldi antennas . . . . . . . . . . . . . . . . . . . . . . . 89
3.6 New technologies on reconfigurable antennas . . . . . . . . . . . . . . . . 93
3.7 Summary of chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
4 Frequency-reconfigurable switched Vivaldi antennas 100
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4.2 Design of a Vivaldi antenna . . . . . . . . . . . . . . . . . . . . . . . . . . 101
4.2.1 Basic Vivaldi antenna . . . . . . . . . . . . . . . . . . . . . . . . . 101