The Beacon Locator Project A Passive Direction Finding System for Locating Pulsed Emitter Signals Presented By: WPI Advisors: -Ted Clancy -Germano Iannacchione Christopher Massa Erik Silva Samantha O Connor October 12, 2011 Staff: -Chris Strus -Scott Bailie -Lisa Basile DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 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. Beacon Locator-1
Outline Project Overview Modeling Hardware Design Summary Beacon Locator-2
Problem Statement and Project Objectives Passively locate direction of pulsed emitter signals Objectives Analyze 3 methods of passive direction finding Time Difference of Arrival Phase Difference Amplitude Comparison θ Design hardware prototype using one direction finding method Beacon Locator-3
Project Specifications and Requirements ±2.5 accuracy 40 db dynamic range 90 field of view Airborne system Real-time Restricted to azimuth plane Operate on 100 MHz bandwidth IF signal Secondary Track 3 beacons simultaneously Beacon Locator-4
Outline Project Overview Modeling Hardware Design Summary Beacon Locator-5
Direction Finding Methods Amplitude = gain pattern Phase & Time Difference Of Arrival Incoming signals cross the beam pattern at different gain levels Path length difference from sources to separated antennas results in a phase shift or TDOA between antennas Beacon Locator-6
Time Difference of Arrival Source Emitter Receiver Array b 2m a 6m d Calculated Error Using TDOA with 250 MHz Sampling Frequency and Simulated Noise 2 10 c = does not meet requirements = meets requirements Signal Strength = 10 dbm Noise Level = -50 dbm SNR = 60 db.. Calculated Error (degrees) 10 1 10 0 10-1 10-2 5.1 o -5.1 o -40-30 -20-10 0 10 20 30 40 Angle of Arrival (degrees) Beacon Locator-7
Phase Comparison Direction Finding Calculate angle of arrival based on phase difference between signals at 2 antennas High accuracy but ambiguous solutions Tx θ R2 d R1 R2 d R1 Beacon Locator-8
Phase Comparison Ambiguity Possible Solutions Calculated Using Phase Comparison with Antennas Separated by 10 cm 40 30 Calculated Solution (degrees) 20 10 0-10 -20-30 -40-40 -30-20 -10 0 10 20 30 40 Angle of Arrival (degrees) Beacon Locator-9
Phase Comparison Accuracy Error in Calculation Using Phase Comparison with Antennas Separated by 10 cm and Simulated Noise 10 2 10 1 Calculated Error (degrees) 10 0 10-1 10-2 10-3 10-4 10-5 Incorrect Ambiguous Solutions 10-6 10-7 -40-30 -20-10 0 10 20 30 40 Angle of Arrival (degrees) Beacon Locator-10
Amplitude Comparison 3.5 Ratio of Voltage Magnitudes Angle of Arrival -45 45 x x Magnitude 3 2.5 2 1.5 Ratio of Magnitudes Antenna 1 Magnitude in Volts 1 0.5 Antenna 2 Magnitude in Volts 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 Time (s) x 10-5 An angle that is detected at each antenna will intersect the antenna radiation beams at different gain values, inducing different voltages at the antennas. Beacon Locator-11
Amplitude Comparison Error Calculated Using Amplitude Comparison Method with 1.8-degree LUT Resolution and Simulated Noise 2 1.8 1.6 Calculated Error (degrees) 1.4 1.2 1 0.8 0.6 0.4 0.2 0-40 -30-20 -10 0 10 20 30 40 Angle of Arrival (degrees) Beacon Locator-12
Amplitude Comparison Dynamic Range Angle of Arrival vs. Dynamic Range for ±2.5 o Accuracy 10 effective ADC bits 60 50 Achievable Dynamic Range with ±2.5 of Accuracy Dynamic Range (db) 40 30 20 40dB Spec. 10 0-40 -30-20 -10 0 10 20 30 40 Angle of Arrival (degrees) Beacon Locator-13
Outline Project Overview Modeling Hardware Design Summary Beacon Locator-14
Hardware Hardware Direction Finding Device Amplitude comparison IF signal processor Implemented on FPGA Desired System Specifications 100MHz bandwidth IF signals ±2.5 accuracy 40 db dynamic range 90 azimuth extent Beacon Locator-15
Signal Processing Platform Hardware Innovative DSP X5-400M Xilinx Virtex 5 SX95T 2 x 14 bit ADC @ 250 MHz 10 effective bits resolution Support Infrastructure Existing PCI-Express Control Hardware PCIE Interface Program Beacon Locator-16
Block Diagram Hardware Data Processing Ethernet Signal Emulator ADC ADC Hilbert Filters Power Power Index Search Lookup Table GUI Measure signal power for two antennas Calculate power ratio Determine angle of arrival Output to GUI Beacon Locator-17
Java Display FPGA Host PC LAN Router Beacon Locator System PC with Java Display Receives AOAs via TCP/IP Displays AOAs in graphical format 10 Hz refresh rate Beacon Locator-18
Testing and Results Input signals generated to test system over desired azimuth extent Most results meet ±2.5 accuracy Errors due to ADC bias and LUT clipping Input Angle Calculated Angle Error -44.6-42.5 2.2-40.5-40.8-0.4-30.4-31.0-0.7-20.3-22.1-1.8-10.2-10.2-0.1 0.1 0.1 0.0 10.2 10.3 0.1 20.3 20.3 0.0 30.4 30.8 0.5 40.5 39.1-1.4 44.6 40.7-3.9 All values in degrees. Full scale (+10dBm) input power Beacon Locator-19
Outline Project Overview Modeling Hardware Design Summary Beacon Locator-20
Summary Passively locate pulsed emitter signals Specification Simulation Hardware ±2.5 accuracy Between +40 and -45 40 db dynamic range Between +25 and -25 N/A 90 field of view Airborne system N/A Real-time N/A Azimuth plane 100 MHz IF input Track 3 beacons Beacon Locator-21
Recommendations Improve System Performance Higher quality ADC Hybrid Amplitude/Phase System Resolve phase difference ambiguities Much higher accuracy Multiple Emitter Tracking Currently handles single beacon Calculated Solution (degrees) 40 30 20 10 0-10 -20-30 -40 Elimination of Ambiguity through Combination of Amplitude and Phase Methods -40-30 -20-10 0 10 20 30 40 Angle of Arrival (degrees) Beacon Locator-22
Acknowledgements Chris Strus Scott Bailie Lisa Basile Ted Clancy Germano Iannacchione Emily Anesta David Hunter Beacon Locator-23
-45 45 Difference in Gain for Received Signals over 90 o Azimuth Extent 8 6 Difference in Gain, G (db) 4 2 0-2 -4-6 -8-40 -30-20 -10 0 10 20 30 40 Angle of Arrival (degrees) Beacon Locator-24