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Direction Finding Spread Spectrum Signals Electrical Engineering Capstone Design II 2015-2016 ENS Ben Morseth and ENS Lê Nelson Project Advisors: Dr. Paul Crilly Dr. Richard Hartnett Sponsors: CG-761 – Mr. Ed Thiedeman CG-SAR – CAPT Peter Martin

Transcript of Direction Finding Spread Spectrum Signals › BMW 2016_files › BMW Presentation_… · Direction...

Page 1: Direction Finding Spread Spectrum Signals › BMW 2016_files › BMW Presentation_… · Direction Finding Spread Spectrum Signals . Electrical Engineering Capstone Design II . 2015-2016

Direction Finding Spread Spectrum Signals

Electrical Engineering Capstone Design II

2015-2016

ENS Ben Morseth and ENS Lê Nelson

Project Advisors: Dr. Paul Crilly

Dr. Richard Hartnett Sponsors:

CG-761 – Mr. Ed Thiedeman CG-SAR – CAPT Peter Martin

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Outline

• Introduction

• Background

• Needs and Objectives

• Requirements

• Results to Date

• System Description

• Challenges

• Future Direction

• Conclusions

• Questions

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Introduction

• U.S. Coast Guard is a multi-mission service • Search and Rescue (SAR) is a primary mission • SAR leverages technology to reduce searching • Mariners in distress use EPIRBs

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Background • Emergency Position Indicating Radio Beacon • EPIRBs responsible for 39,000+ people rescued

since 1982 • Current EPIRB

• Narrow band signals • Broadcasts signal to

satellite on 406 MHz • Homing signal operates

on 121.5 MHz

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COSPAS-SARSAT Update

Current system:

• LEOSAR – Low Earth Orbiting SAR • GEOSAR – Geostationary Earth Orbiting SAR

New addition:

• MEOSAR – Medium Earth Orbiting SAR

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EPIRB System Upgrade • Direct Sequence Spread Spectrum (DSSS)

• Greater immunity to interference/jamming

• Potential for greater quantity of beacons (different spreading codes)

• Smaller and lower cost

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Needs and Objectives • Problem: Search and Rescue assets will lose the

capability to home in on EPIRB satellite signals. • Goal: Develop proof of concept architecture for

direction finding on DSSS signals.

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System Requirements •User friendly GUI •DF a wide band (WB) and narrow band (NB) signals within ± 5° •Test under realistic conditions set by the Second Generation Beacon (SGB) systems

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Results to Date • Began with two element phased array antenna • Incorporated and successfully built 4 element

antenna/4 USRP system • Successful DF on WB signals

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System Overview • Host computer OS: Ubuntu 14.04 LTS • GnuRadio Companion (GRC) and MATLAB • USRP: specific Software-Defined Radio • Phased array antenna

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MUSIC Algorithm •Greatest strength of the system •Uses differences in phase to locate signal •Based on Eigen vectors and values of covariance matrix •Implemented in MATLAB

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MUSIC Algorithm

θ θ

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4x4 Direction Finding System

4x4 = 4 antennas + 4 USRPs

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Function Design Overview

USRP 1

USRP 4

USRP 3

USRP 2

Host Computer

Ethernet Switch

OctoClock

Ethe

rnet

Cab

les

PPS in REF in

Antennas

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4x4 System Field Tests

(degrees)

-100 -80 -60 -40 -20 0 20 40 60 80 100

Angle of Incoming Signal

• First tested with NB transmitted source • Successful tests with repeatable, reliable results • Next step: WB signal

Highest Peak: 0.1°

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4x4 System Field Tests • Test with wide band signal • Bandwidth = 100 kHz

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4x4 System Field Tests • Successful DF on wide band signal • Tested at 30°, 45°, and 60° Expected Angle Mean Bearing Standard Deviation

30.0° 35.7° 1.2°

45.0° 44.3° 1.9°

60.0° 51.9° 3°

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Repeatability Illustration

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Software Challenges

• Difficult to acclimate to Linux • GRC easy to learn, hard to master • User block creation • Misleading block (e.g. ‘valve’ block)

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Hardware Challenges

• Familiarization with USRPs • Hardware malfunctions • Receiver synchronization • Undocumented functionality

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Field Test Challenges

•Testing 4x4 DF system •Battery failure •GRC crashing •Antenna sensitivity to nearby objects

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Future Direction

• Shift from GRC to National Instruments LabVIEW • DF on actual SGB prototype • Real time data acquisition • DF on cell phone and Wi-Fi signals

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Conclusions

• Demonstrated capability to DF on both traditional narrow and new wide band beacon signals

• Results are accurate and repeatable • Technology exists to bring wide band DF to SAR

Response Units

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Questions?

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4x4 GnuRadio Model

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4x4 GnuRadio Model