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A Thesis Entitled Compact Wire Antenna Array for Dedicated Short A Thesis entitled Compact Wire Antenna Array for Dedicated Short-Range Communications: Vehicle to Vehicle and Vehicle to Infrastructure Communications by Michael A. Westrick Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Electrical Engineering ______________________________________ Vijay Devabhaktuni, Ph.D., Committee Chair ______________________________________ Richard Molyet, Ph.D., Committee Member ______________________________________ Mansoor Alam, Ph. D., Committee Member ______________________________________ Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo December 2012 Copyright 2012 © Michael A. Westrick This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of Compact Wire Antenna Array for Dedicated Short-Range Communications: Vehicle to Vehicle and Vehicle to Infrastructure Communications by Michael A. Westrick Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Electrical Engineering The University of Toledo December 2012 This thesis contributes to the advancement of Dedicated Short Range Communications antenna research for automobile applications. This research is focused on implementing vehicle-to-vehicle and vehicle-to-infrastructure communications to advance both the safety and the quality of the driving experience of modern motorists. This thesis achieves three separate goals. First, a brief literature review details the current state of DSRC antenna research and the drawbacks of antenna designs previously presented. Secondly, several common wire antennas are modeled and simulated in order to assess their potential in DSRC communications. Using an industry standard electromagnetic full-wave simulator, Ansys-HFSS, all of the antenna designs examined are determined to be lacking to some degree. In this way, the need for novel antenna designs in the DSRC frequency band is clearly outlined. The third goal of this thesis is to present a novel wire antenna design with an omni directional radiation pattern for DSRC communications. The novel design is developed based on several of the fundamental wire antennas analyzed for DSRC, but it is a unique antenna that meets all of the criteria specified in the literature review section. Furthermore, it out performs all the currently available antennas in one way or another. iii In order to mount the antenna in an automobile, a double-sided feed board is proposed that utilizes a grounded coplanar waveguide to excite the central monopole of the wire antenna array, and a quarter-wave transformer to improve the overall impedance match of the antenna. Vias are then added to the board around the feed line in order to suppress parallel plate modes within the substrate. Lastly, the feed board is attached with screws to a metallic cavity designed to shield the array from electromagnetic interference from within the vehicle cabin. This increases the robustness of the design in terms of both the structural and signal integrity. The overall antenna system is simulated for operation in the DSRC frequency band. The antenna presented in this thesis is found to fulfill all the necessary criteria for vehicle-to-vehicle communications, and its performance exceeds that of DSRC antennas currently available. iv For my wife Danielle, my parents, my siblings, my nieces, and my nephews. Acknowledgments I would like to express my deepest gratitude to my advisor Dr. Vijay Devabhaktuni for his encouragement and honesty throughout my graduate studies. He has been a steady source of wisdom and guidance, and his abundant energy and enthusiasm has made him an amazing advisor and friend. It has been a pleasure working with the faculty, staff, and my lab mates at the University of Toledo, during my journey through the masters program. I gratefully thank Dr. Richard Molyet and Dr. Mansoor Alam for serving on my thesis committee and for providing me with insightful guidance throughout the years in their respective posts of undergraduate and graduate advisor for the Electrical Engineering and Computer Science department. I appreciate the funding supports offered by the Electrical Engineering and Computer Science (EECS) department, the National Science Foundation (NSF), and Imaging Systems Technology (IST) in giving me the opportunity to pursue my thesis research. I would like to sincerely thank Dr. Mohammad Almalkawi for his overwhelming support in this research, and his constant encouragement. Without his calming, confidant influence this thesis would not have been possible. vi Table of Contents Abstract ............................................................................................................................. iii Acknowledgments ............................................................................................................ vi Table of Contents ............................................................................................................ vii List of Tables .................................................................................................................... ix List of Figures .....................................................................................................................x List of Abbreviations ..................................................................................................... xiv Chapter 1: Introduction ....................................................................................................1 1.1 Motivation ..........................................................................................................2 1.2 Antenna Technology Review .............................................................................4 1.3 Thesis Objectives ...............................................................................................8 1.4 Thesis Overview ................................................................................................9 Chapter 2: Background on Automobile Antennas .......................................................11 2.1 Low Frequency Automobile Antennas ............................................................11 2.2 High Frequency Automobile Antennas ...........................................................14 2.3 Current DSRC Antennas ..................................................................................16 Chapter 3: Overview on Wire Antenna Design ............................................................20 3.1 Fundamental Wire Antennas ............................................................................20 3.1.1 Dipoles and Monopoles ....................................................................21 3.1.2 Loop Antennas ..................................................................................35 vii 3.2 Common Variations on Fundamental Wire Antennas .....................................38 3.2.1 Yagi-Uda Dipole Arrays and Folded Dipoles ...................................39 3.2.2 Helical Antennas ...............................................................................47 Chapter 4: Novel DSRC Antenna Design and Simulation ...........................................51 4.1 Novel Antenna Design .....................................................................................51 4.2 Antenna Simulation .........................................................................................55 4.3 Feed Board Design ...........................................................................................61 4.4 Cavity Design...................................................................................................69 4.5 System Assembly and Simulation ...................................................................72 Chapter 5: Conclusion and Future Work ......................................................................75 5.1 Conclusions ......................................................................................................75 5.2 Future Work .....................................................................................................76 References .........................................................................................................................78 viii List of Tables 3.1 Variables Affecting Helical Antenna Performance ...............................................48 4.1 Parameters of a Monopole Yagi-Uda Antenna Array ............................................53 4.2 Optimized Parameters of a Novel Wire Antenna Array ........................................60 4.3 Feed Network Board Details ..................................................................................68 ix List of Figures 3-1 Ansys – HFSS model of an ideal dipole antenna ...................................................21 3-2 Reflection coefficient(S 11 ) of a 23.9 mm dipole antenna simulated in Ansys-HFSS in decibels (dB) ......................................................................................................23 3-3 VSWR of a 23.9 mm dipole antenna simulated in Ansys-HFSS ...........................24 3-4 Radiation pattern of a 23.9 mm dipole antenna simulated in Ansys-HFSS in the (a) X-Y plane and (b) X-Z plane (in decibels, dB) ................................................25 3-5 Reflection coefficient, S 11 , results for parametrically varying dipole length from 20 mm to 40 mm, simulated in Ansys-HFSS,
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