Development of Very Low-Profile Ultra-Wideband VHF Antennas

120 Pages·2011·2.84 MB·English

Development of Very Low-Profile Ultra-Wideband
VHF Antennas
A Thesis
Presented in Partial Fulfillment of the Requirements for
the Degree Master of Science in the
Graduate School of The Ohio State University
By
Haksu Moon, B.S.
Graduate Program in Electrical and Computer Engineering
The Ohio State University
2011
Master’s Examination Committee:
Prof. John L. Volakis, Advisor
Dr. Chi-Chih Chen, Co-advisor
c Copyright by
(cid:13)
Haksu Moon
2011
Abstract
Withtherapidgrowthofwirelesscommunicationsandassociateddemandforhigh
data-rates, many future antennas must be ultra-wideband (UWB). A single antenna
is certainly a most attractive solution to handling the large bandwidth requirements.
Designingsuchanantennathatisconcurrentlyoflow-profileisnecessaryformounting
on a variety of grounds and airborne vehicles. This thesis presents a new low-profile
UWB antenna concept. The concept is based on a shorted low-profile patch strategi-
cally fed on the open side to obtain wide bandwidth. For miniaturizing the proposed
antenna and widening its bandwidth, it was loaded with ferrite bars placed between
the patch plate and the ground plane. Much of the design effort for this antenna is fo-
cused on the location and shape of the ferrite bars. Minimization of antenna weight is
also performed. The developed ferrite-loaded shorted-patch concept is compared with
a low-profile monopole to demonstrate its superior bandwidth and gain performance
over the frequency range from 30 MHz to 400 MHz. Prototype versions of various
ferrite-loaded shorted-patch antennas were fabricated and measured for validation. A
version of these was the design that has a planar patch as small as λ/16 in diameter
and a height of only λ/200 at the lowest operational frequency.
We note that the ferrite loading design led to 5 to 14 dB gain improvement in
the low frequency range below 50 MHz. The resulting gain was actually close to the
optimal Fano-Bode limit. An important aspect of the ferrite loading design was the
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useofcommerciallyavailablematerials. Althoughthesewerelossyathighfrequencies,
their strategic placement resulted in minimal gain reduction.
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This thesis is dedicated to my family and friends
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Acknowledgments
First and foremost, I am heartily thankful to my advisor, Prof. John L. Volakis,
whose encouragement, guidance, and support enabled me to complete a Master’s
degree as well as this thesis. Without his endless enthusiasm, the completion of the
degree would not be possible.
Also, I would like to thank my co-advisor, Dr. Chi-Chih Chen, for his continuous
mentoring and patience. His unfailing support has enriched my knowledge and ex-
perience in electromagnetics area, which enabled me to complete the research topic
presented here.
I am also indebted to many of my ESL colleagues to help, advise, and support me,
who are Jing Zhao, Gil Young Lee, Ugur Olgun, Chia-Wei Liu, Ming Chen, Jaeyoung
Chung, Keum Su Song, James Park, Chun-Sik Chae, and William Moulder.
Also, I would like to express my appreciation to Kyungyoung Jung, Young-Seo
Ko, and Daeyoung Choi for their support and encouragement.
Last but not least, I offer my sincerest regards and blessings to my parents and
brother who always trust and support me at any time in my life.
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Vita
January 9, 1982 ............................ Born - Yeosu, Korea
February 22, 2008 ..........................B.S. in Electrical and Computer Eng.,
Hanyang University, Seoul, Korea
October, 2008-present ...................... Graduate Research Associate,
ElectroScience Laboratory,
The Ohio State University, USA
Publications
Conference Publications
Haksu Moon, Chi-Chih Chen, and John L. Volakis, “Quad Split Ultrawideband
Inverted-Hat-Antenna with Pattern and Polarization Diversity”, IEEE APS/URSI-
B, Session 409, Charleston, SC., 2009.
Haksu Moon, Chi-Chih Chen, and John L. Volakis, “Ultra Low Profile Wideband
Antenna with Ferrite Loading”, IEEE APS, Session 309, Toronto, Canada, 2010.
Fields of study
Major Field: Electrical and Computer Engineering
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Studies in:
Theoretical Electromagnetics Prof. Jin-Fa Lee
Prof. Prabhakar Pathak
Prof. Roberto Rojas-Teran
Computational Electromagnetics Prof. Jin-Fa Lee
Prof. Fernando Teixeira
Antennas and Propagation Prof. John L. Volakis
Prof. Joel T. Johnson
Microwave Circuits Prof. Patrick Roblin
Communications Prof. Phil Schniter
Mathematics Prof. Fei-Ran Tian
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Table of Contents
Page
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Vita . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii
Chapters:
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Motivation and Goal . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Organization of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Review of Small Antenna Limitations . . . . . . . . . . . . . . . . . . . . 5
2.1 Size Restriction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Bandwidth Limitation . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 TM and TE Mode Operation . . . . . . . . . . . . . . . . . . . . . 8
3. Monopole Antenna Design Study . . . . . . . . . . . . . . . . . . . . . . 11
3.1 Basic Antenna Properties . . . . . . . . . . . . . . . . . . . . . . . 11
3.2 Modification of Antenna Geometry . . . . . . . . . . . . . . . . . . 14
3.2.1 Various Top Geometries . . . . . . . . . . . . . . . . . . . . 14
3.2.2 Inductive Loading Using Spiraled Arms . . . . . . . . . . . 16
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3.3 Effect of Cavity under Ground Plane . . . . . . . . . . . . . . . . . 20
3.4 Miniaturization via Material Loading . . . . . . . . . . . . . . . . . 23
3.4.1 First Resonant Frequency . . . . . . . . . . . . . . . . . . . 23
3.4.2 Material with Constant Wavenumber and
Different Wave Impedances . . . . . . . . . . . . . . . . . . 26
3.4.3 Material with Constant Wave Impedance and
Different Wavenumbers . . . . . . . . . . . . . . . . . . . . 27
3.4.4 Ferrite Loading . . . . . . . . . . . . . . . . . . . . . . . . . 29
4. Low-Profile UWB VHF Antenna Based on Grounded Loop Antenna . . . 31
4.1 Wideband Grounded Loop Antenna . . . . . . . . . . . . . . . . . 31
4.2 Parametric Studies with Antenna Dimension . . . . . . . . . . . . . 35
4.2.1 Width Study . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.2.2 Length Study . . . . . . . . . . . . . . . . . . . . . . . . . . 37
4.2.3 Height Study . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4.2.4 Feeding Plate Study . . . . . . . . . . . . . . . . . . . . . . 40
4.2.5 Top Geometry Study . . . . . . . . . . . . . . . . . . . . . . 41
4.3 Miniaturization via Uniform Ferrite Loading . . . . . . . . . . . . . 43
4.3.1 Benefit of Ferrite Loading . . . . . . . . . . . . . . . . . . . 43
4.3.2 Comparison of Various Commercial Ferrites . . . . . . . . . 45
4.4 Gain Improvement Using Non-Uniform Ferrite Loading . . . . . . . 47
4.4.1 Width Optimization . . . . . . . . . . . . . . . . . . . . . . 47
4.4.2 Height Optimization . . . . . . . . . . . . . . . . . . . . . . 52
4.4.3 Placement Optimization . . . . . . . . . . . . . . . . . . . . 55
4.4.4 Top Geometry Optimization . . . . . . . . . . . . . . . . . . 56
4.4.5 Optimized Antenna Performance . . . . . . . . . . . . . . . 58
4.5 Ferrite Volume Reduction . . . . . . . . . . . . . . . . . . . . . . . 63
4.5.1 Ferrite Volume Reduction Approach . . . . . . . . . . . . . 63
4.5.2 Parametric Studies . . . . . . . . . . . . . . . . . . . . . . . 65
4.6 Further Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5. Fabrication and Measurements . . . . . . . . . . . . . . . . . . . . . . . 73
5.1 Fabrication Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.2 Measurement Setups . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.2.1 Outdoor Measurement Setup . . . . . . . . . . . . . . . . . 77
5.2.2 Indoor Measurement Setup . . . . . . . . . . . . . . . . . . 82
5.3 Measurement Results and Discussions . . . . . . . . . . . . . . . . 84
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