Software Defined Radar Group 33 Ranges and Test Beds MQP Final Presentation Shahil Kantesaria Nathan Olivarez Thursday, February 13, 2020 This work is sponsored by the Department of the Air Force under Air Force Contract #FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the author and not necessarily endorsed by the United States Government WPI/LL MQP 1 02/13/2020 Overview Project Introduction & Deliverables Radar Background Radar System Design Time Synchronization Radar Processing Summary WPI/LL MQP
2 02/13/2020 Project Introduction Project objective: build an inexpensive multistatic radar receive system using Ettus Universal Software Radio Peripheral (USRP2) Deliverables: Time Synchronization Radar Processing Range Doppler Direction Software Defined Radio Radio whose typical hardware components are
implemented in software Digital filters & mixers, modulators/demodulators http://cwnlab.ece.okstate.edu/images/facilitiesimg/usrp2.jpg WPI/LL MQP 3 02/13/2020 Radar Background Radar, short for Radio Detection and Ranging, is a method of detecting targets using electromagnetic waves Two different types of Radar: Pulse Radar Continuous Wave Radar
Over the Horizon Radar: Continuous Wave 3-30 MHz Frequency Multistatic configuration Large antenna arrays (~2-3 km) http://www.raytheon.com/capabilities/products/stellent/groups/public/documents/legacy_site/cms01_049201.pdf 1 WPI/LL MQP 4 02/13/2020 Multistatic Radar System Transmitter
WPI/LL MQP 5 02/13/2020 Receiver Clock Synchronization Sampling rate of the system is 100 MHz Our radar system operates in HF (3-30 MHz) Tolerance of 5 ns minimizes the error to less than 15% for the HF band WPI/LL MQP 6 02/13/2020 Clock Stability WPI/LL MQP 7
02/13/2020 Current Performance Target Performance 3 Synchronized, 1 Not 4 Synchronized Radios USRP2 Clock Synchronization Synchronizing USRP2 ADC Clock 100 MHz Internal Oscillator controlled by a Phased Locked Loop Inputs to Phase Locked Loop 10 MHz Reference Clock 1 pulse per second (PPS ) Input Power/Level Requirements 10 MHz Ref. Clock Power: 5-15 dBm 1 PPS: 5V Peak-to-Peak 10 MHz CLK
GPS Clock WPI/LL MQP 8 02/13/2020 1 PPS Signal Amplifier / Splitters /6 Signal Amplifier / Splitters /6 USRP2 Radios Receiver System Design Software
Defined Radio SDR Signal Splitters Network Switch SDR Ref Clock Computer SDR Signal Splitters SDR Legend
10 MHz Reference Clock SDR Antenna WPI/LL MQP 9 02/13/2020 /6 1 PPS Ethernet Cable RF input Radar System Design Selected the following Components: Jackson Labs GPS Disciplined Oscillator
10 MHz output 1 PPS output Pulse Research Labs 1:4 Fanout Buffer Clock/PPS Signal Distribution Freq < 100 MHz Four in-phase 50 TTL Outputs http://media.marketwire.com/attachments/200706/MOD-346700_Fury_bezel_small.jpg http://www.pulseresearchlab.com/products/fanout/prl-414B/images/PRL-414B_small.jpg 1 2 WPI/LL MQP 10 02/13/2020 Our Implementation Pulse Research Labs TTL Line Driver (1:4)
Network Switch /6 Legend 10 MHz Reference Clock 1 PPS Ethernet Cable RF input Synchronization Testing WPI/LL MQP 12 02/13/2020 We used an oscilloscope and the USRP2 clock debug pins to record the ADC clock drift PPS Trigger Test
The purpose of this test was to determine whether the radios could consistently trigger off the 1 PPS 30 Minute Persistence Plot Channels 1-3 were connected to USRP2s and Channel 4 was connected to the GPSDO PPS output The PPS signal served as a reference for measuring drift WPI/LL MQP
13 02/13/2020 Voltage < 2ns Time (ns) Radar Receiver GNU Radio provides the means to interface the USRP2 array and record data Radar processing implemented in Matlab Range Doppler Direction WPI/LL MQP 14
02/13/2020 Range Processing Range is determined by the time delay between the transmitted and the received signals Assuming the transmitter and receiver are synchronized, the delay equals the travel time R R c /2 Tx Rx t=0 WPI/LL MQP 16 02/13/2020
Time delay t= Range Processing (cont.) The delay can be computed by determining when the chirp was received via correlation Correlating the received signal with the transmitted chirp is known as pulse compression Amplitude Received Chirp CORR Time WPI/LL MQP 17
02/13/2020 Single Sweep Peak index denotes delay Transmitted Chirp Amplitude Range bins Range Plot Multiple sweeps over time Range vs. Time Time
WPI/LL MQP 18 02/13/2020 Doppler Processing Used to identify target velocity Doppler is a phase progression from sweep to sweep The Fourier Transform of a periodic function produces an impulse function at the center frequency Taking the FFT of the range cells creates a peak at the intersection of the targets range and Doppler Frequency Range vs. Time Range vs. Speed FFT FFT
Range (km) Range (km) FFT FFT Time WPI/LL MQP 20 02/13/2020 Velocity (km/hr) Direction Finding Direction finding requires a vector of the complex samples from each channels Range-Doppler plot Assuming a flat wave front (far field transmission), each sample has magnitude M and phase :
WPI/LL MQP 22 02/13/2020 Direction Finding (cont.) Each point is multiplied by a candidate zeroing vector defined for different theta values The value theta that optimizes the sum is the incident angle Complex samples from receivers at one Range-Doppler cell
Optimum 180 0 x1 x2 x3 Maximum magnitude sum WPI/LL MQP 23 02/13/2020 Our Receive Array
WPI/LL MQP 24 02/13/2020 Six, 10 ft antennas arranged in a linear array outside Katahdin Hill Direction Finding Demonstration WPI/LL MQP 25 02/13/2020 Summary Purpose: Develop an inexpensive phased receive array using the USRP2 SDR Deliverables: Synchronized array
Array form factor Radar processing code Future Works Setup larger line array Improve synchronization by modifying FPGA firmware Implement Real-time Processing WPI/LL MQP 26 02/13/2020 Acknowledgements Vito Mecca Kyle Pearson Matthew Morris James Montgomery Jeffrey McHarg Walter Dicarlo Robert Piccola Special Thanks to:
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