Single Antenna Null-Steering for GPS & GNSS Aerial Applications

178 Pages·2016·38.05 MB·English

SINGLE ANTENNA NULL-STEERING
FOR GPS & GNSS AERIAL APPLICATIONS
A DISSERTATION
SUBMITTED TO THE DEPARTMENT OF ELECTRICAL
ENGINEERING
AND THE COMMITTEE ON GRADUATE STUDIES
OF STANFORD UNIVERSITY
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
Emily McMilin
March 2016
© 2016 by Emily Beth McMilin. All Rights Reserved.

Re-distributed by Stanford University under license with the author.

This work is licensed under a Creative Commons Attribution-

Noncommercial 3.0 United States License.
http://creativecommons.org/licenses/by-nc/3.0/us/

This dissertation is online at: http://purl.stanford.edu/cf484ht3939

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I certify that I have read this dissertation and that, in my opinion, it is fully adequate
in scope and quality as a dissertation for the degree of Doctor of Philosophy.
Per Enge, Primary Adviser
I certify that I have read this dissertation and that, in my opinion, it is fully adequate
in scope and quality as a dissertation for the degree of Doctor of Philosophy.
Thomas Lee
I certify that I have read this dissertation and that, in my opinion, it is fully adequate
in scope and quality as a dissertation for the degree of Doctor of Philosophy.
Todd Walter
Approved for the Stanford University Committee on Graduate Studies.
Patricia J. Gumport, Vice Provost for Graduate Education
This signature page was generated electronically upon submission of this dissertation in
electronic format. An original signed hard copy of the signature page is on file in
University Archives.
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Abstract
As the utility of the Global Positioning System (GPS) and other Global Navigation
Satellite Systems (GNSS) continue to pervade -and upgrade- our daily activities, our
increased reliance makes us more vulnerable to the inherent weaknesses of GPS. The
incredible faintness and unencrypted nature of the GNSS signal exposes it to both
unintentional and intentional overwhelming, via mechanisms such as interference,
jamming and spoofing (the broadcast of counterfeit GNSS signals intended to deceive
aGNSSreceiver). Howeversomemayarguethatdespitethegreatrisk,theprobability
of a jamming or spoofing event is thankfully low. The argument may continue, that
correspondinglyfewresourcesshouldbededicatedtoprotectagainstalowprobability
event. I attempt to resolve the tension between these high risk yet low probability
scenarios by establishing antenna designs that provide protection while exploiting
existing infrastructure and equipment, thus requiring minimal additional resource
dedication.
This thesis will start with an introduction of a low complexity mechanism for
generating radiation pattern nulls and beams with a singleantenna, without requiring
any additional hardware or signal processing blocks beyond those already inherent to
GNSS receiver systems. I will describe the basic mathematical model that underlies
this mechanism and share simulation results. I will then introduce two applications
of this mechanism: single antenna interference/jam suppression and single antenna
spoof detection. Results from simulations and two field trials will be presented: one
with a software implementation using a software defined radio, and the other with a
hardware prototype implemented in o↵-the-shelf components using a standard GPS
receiver. Results show about 15 dB of interference/jam suppression and robust spoof
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detection, when the threatening signals originate from below the horizon of the GNSS
antenna, making aerial platforms an ideal application.
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Acknowledgements
I would like to express my immense gratitude to my advisor Professor Per Enge, who
has so generously provided me support, mentorship and intellectual guidance while
helping me navigate the sometimes turbulent PhD waters. My most sincere thanks
goes to my dissertation committee: Professor Tom Lee who has mastered wireless
power transfer when he shares his intellectual energy with those lucky enough to be
in the room, and Dr. Todd Walter who kept my ideas well grounded in practice and
measurement, despite our aerial application. My great appreciation goes out to my
oral exam committee members Professor Leo Hollberg and Professor Dan Boneh for
their generous advice and guidance both before and after the examination.
I also want to thank my friends and colleagues in the GPS Lab, who fostered a
stimulating, productive and fun lab environment. My most warm appreciation goes
to Dr. Yu-Hsuan Chen and Dr. Dave De Lorenzo for their essential contributions in
the lab, on the roof, and in the field, often under the hot, hot sun. Professor Dennis
Akos kindly provided numerous sanity checks (and perhaps the occasional not-sane
check) despite the last-minute nature of my requests.
My great appreciation goes out to Chris Hoeber and the antenna team at Space
Systems Loral, for the kind access to their anechoic chamber and antenna lab re-
sources. Our field test results would never have been possible without the support
of Abiud Jimenez, David Rohret, and their colleagues at JVAB who provided the
jamming and spoofing signals.
My heart-felt appreciation to John and Judy Doyle who generously supported
me during my first year of research and continue to o↵er kind words of support,
encouragement and friendship.
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Finally I am honored to thank my family for their unconditional and unending
supportofallmypursuits. Iamsoincrediblyluckytospeakwithbothmymotherand
father almost daily, as they accommodate their schedule and sometimes dinner, to my
availability. My grandma Florence’s exuberance for live and adventure continues to
motivate me, and my grandma Barbara’s perseverance lives on in my memory. Never
ending thanks to my Uncle Lloyd who opened his home and life to me during my
Masters degree and to my aunt Natalie and cousin Rachel who open their minds to
me and my research ideas. My sister and her family have and will drop everything to
support me when I need them, and this warm safety-net always embraces me. Finally
my husband whose dedication, selflessness, and intellectual creativity has inspired me
to try and become the best person that I can be.
This research is in loving memory of our daughter, Zoe Lee Schlub McMilin, who
was stillborn on Saturday July 11th 2015 at 28 weeks old. She was only 2 lbs 3 oz
and 15 inches tall, but she leaves a much larger hole in our souls. She also leaves
our hearts full of love and hope that we may continue to grow and learn from all she
taught us during her short beautiful life.
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Contents
Abstract iv
Acknowledgements vi
1 Introduction 1
1.1 Global Navigation Satellite Systems . . . . . . . . . . . . . . . . . . . 1
1.1.1 The Nature of the GNSS Signal . . . . . . . . . . . . . . . . . 2
1.1.2 Modern-Day Threats to GNSS . . . . . . . . . . . . . . . . . . 6
1.2 Prior Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.1 Antenna Techniques . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 Research in this Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.3.1 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.3.2 Outline of Remainder of Thesis . . . . . . . . . . . . . . . . . 17
2 Antenna Fundamentals 18
2.1 Important Metrics and Definitions . . . . . . . . . . . . . . . . . . . . 18
2.1.1 Cross Polarization Discrimination (XPD) Ratio . . . . . . . . 18
2.1.2 Multi-path Rejection (MPR) Ratio . . . . . . . . . . . . . . . 20
2.1.3 Coordinate System . . . . . . . . . . . . . . . . . . . . . . . . 21
2.2 Standard GNSS Antennas . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.1 Typical Radiation Patterns . . . . . . . . . . . . . . . . . . . 25
2.2.2 Typical Radiation Patterns on Large Ground-planes . . . . . . 27
2.2.3 Typical Schematic Diagram . . . . . . . . . . . . . . . . . . . 28
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3 Antenna Measurements and Simulations 32
3.1 Patch Antenna in Free-space . . . . . . . . . . . . . . . . . . . . . . . 32
3.1.1 Prototype Construction . . . . . . . . . . . . . . . . . . . . . 33
3.1.2 Magnitude Response . . . . . . . . . . . . . . . . . . . . . . . 33
3.2 Patch Antenna on Ground-plane . . . . . . . . . . . . . . . . . . . . . 37
3.2.1 Simulation Set-up . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2.2 Magnitude Response . . . . . . . . . . . . . . . . . . . . . . . 39
3.2.3 Phase Response . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2.4 Even Larger Ground-planes . . . . . . . . . . . . . . . . . . . 44
4 Theoretical Models 46
4.1 Single Element Dynamic Antenna . . . . . . . . . . . . . . . . . . . . 47
4.1.1 Dynamic Antenna Schematic Diagram . . . . . . . . . . . . . 47
4.2 S-parameters Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.2.1 Right Hand Circularly Polarized (RHCP) signals . . . . . . . 50
4.2.2 Left Hand Circularly Polarized (LHCP) signals . . . . . . . . 53
4.2.3 Linearly Polarized (LP) signals . . . . . . . . . . . . . . . . . 54
4.3 Null-Steering Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.4 Angle Dependency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.4.1 Azimuth Angle Dependency . . . . . . . . . . . . . . . . . . . 63
4.4.2 Elevation Angle Dependency . . . . . . . . . . . . . . . . . . . 64
4.5 Building Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5 Implementation 71
5.1 Software Implementation (SWI) . . . . . . . . . . . . . . . . . . . . . 73
5.1.1 SWI Antenna Subsystem . . . . . . . . . . . . . . . . . . . . . 73
5.1.2 SWI Circuit Subsystem . . . . . . . . . . . . . . . . . . . . . . 73
5.2 Hybrid Implementation (HyI) . . . . . . . . . . . . . . . . . . . . . . 76
5.2.1 HyI Antenna Subsystem . . . . . . . . . . . . . . . . . . . . . 77
5.2.2 HyI Circuit Subsystem . . . . . . . . . . . . . . . . . . . . . . 78
5.3 Hardware Implementation (HWI) . . . . . . . . . . . . . . . . . . . . 81
5.3.1 HWI Antenna Subsystem . . . . . . . . . . . . . . . . . . . . 82
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5.3.2 HWI Circuit Subsystem . . . . . . . . . . . . . . . . . . . . . 82
6 Single Antenna Anti-jam 87
6.1 Jam Suppression Mechanism . . . . . . . . . . . . . . . . . . . . . . . 87
6.2 SWI Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
6.2.1 SWI Simulation Results and Analysis . . . . . . . . . . . . . . 90
6.2.2 SWI Model Agreement . . . . . . . . . . . . . . . . . . . . . . 92
6.2.3 SWI Phase Shift Determination . . . . . . . . . . . . . . . . . 93
6.3 HyI Field Trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
6.3.1 HyI Field Trial Setup . . . . . . . . . . . . . . . . . . . . . . . 95
6.3.2 HyI Field Trial Measurement . . . . . . . . . . . . . . . . . . 96
6.3.3 HyI Field Trial Post-processing . . . . . . . . . . . . . . . . . 100
6.3.4 HyI Field Trial Results and Analysis . . . . . . . . . . . . . . 101
6.4 HWI Field Trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6.4.1 HWI Field Trial Setup and Measurement . . . . . . . . . . . . 107
6.4.2 HWI Field Trial Post-processing . . . . . . . . . . . . . . . . . 108
6.4.3 HWI Field Trial Results and Analysis . . . . . . . . . . . . . . 108
7 Single Antenna Spoof Detection 113
7.1 Spoof Detection Mechanism . . . . . . . . . . . . . . . . . . . . . . . 114
7.2 HyI Field Trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
7.2.1 HyI Field Trial Setup . . . . . . . . . . . . . . . . . . . . . . . 118
7.2.2 HyI Field Trial Measurement . . . . . . . . . . . . . . . . . . 118
7.2.3 HyI Field Trial Post-processing . . . . . . . . . . . . . . . . . 120
7.2.4 HyI Field Trial Results and Analysis . . . . . . . . . . . . . . 122
7.3 HWI Rooftop Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
7.3.1 HWI Rooftop Test Setup and Measurement . . . . . . . . . . 126
7.3.2 HWI Rooftop Test Post-processing . . . . . . . . . . . . . . . 126
7.3.3 HWI Rooftop Test Results and Analysis . . . . . . . . . . . . 129
7.4 HWI Field Trial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
7.4.1 HWI Field Trial Setup and Measurement . . . . . . . . . . . . 133
7.4.2 HWI Field Trial Post-processing . . . . . . . . . . . . . . . . . 134
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