Robust Wideband Waveforms for Synthetic Aperture Radar (SAR) and Ground Moving Target Indication (GMTI) Applications

Transcription

1 Robust Wideband Waveforms for Synthetic Aperture Radar (SAR) and Ground Moving Target Indication (GMTI) Applications DARPA SBIR Topic: SB82-2, Phase II Army Contract W31P4Q-11-C-43 Program Summary September 2, 215 Jamie Bergin John Pierro Work funded by the Defense Advanced Research Projects Agency under Army Contract W31P4Q-11- C-43 The views, opinions, and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government 813 Boone Blvd. Suite 5 Vienna, Virginia (73) FAX: (73) These SBIR data are furnished with SBIR rights under Contract No. W31P4Q-11-C-43. For a period of 5 years after acceptance of all items to be delivered under this contract, the Government agrees to use these data for Government purposes only, and they shall not be disclosed outside the Government (including disclosure for procurement purposes) during such period without permission of the Contractor, except that, subject to the foregoing use and disclosure prohibitions, such data may be disclosed for use by support Contractors. After the aforesaid 5-year period the Government has a royalty-free license to use, and to authorize others to use on its behalf, these data for Government purposes, but is relieved of all disclosure prohibitions and assumes no liability for unauthorized use of these data by third parties. This Notice shall be affixed to any reproductions of these data, in whole or in part.

2 Background Data Collection Summary Processing Results Next Phase Outline SB82-2/JSB 9/15-2

3 GMTI and Small UAVs Air Force JSTARS ~2 in. antenna 2 receive channels >5 meter antenna 3 receive channels Telephonics ZPY-4 Fire Scout UAV (unmanned Bell 47) Cost, Size, weight, and power (SWAP) constraints severely limit the antenna size and numbers of instrumented channels Slower UAV platform speeds can potentially help but can lead to sub-optimal endurance SB82-2/JSB 9/15-3

4 Solution: Multiple Input, Multiple Output (MIMO) Radar A unique mode that exploits multiwaveform and spatial diversity to enhance spatial and temporal resolution s 1 ( t) s ( ) s N (t) 2 t Particularly well-suited for small UAV radars with limited aperture h 1 h2 y1,1 y1, hn h 1 h2 y 1, N y 2, 1 y2, hn... h 1 h2 y 2, y N N, 1 y N, hn y N, N Made possible by recent advances in digital RF front ends à in particular digital waveform generators filter h n is matched to transmit signal s n (t) and has low correlation with all other signals SB82-2/JSB 9/15-4

5 MIMO Radar Properties MIMO radar provides a virtual increase in the antenna aperture The virtual array positions are the convolution of the transmit and receiver array element position real receive array real transmit array MIMO virtual array { 1} 1 * { 1} 1 { 1 2 1} Provides longer aperture and additional spatial channels needed for GMTI mode D. Bliss, et al., MIMO Radar: Resolution, Performance, and Waveforms, Proceedings of the 26 ASAP Workshop, MIT Lincoln Laboratory, Lexington, MA SB82-2/JSB 9/15-5

6 Radar Performance Improvement RMS error re. beamwidth Slow-Moving Targets conv. MIMO RMS error re. beamwidth Fast-Moving Targets conv. MIMO SNR (db) MIMO provides >2x improvement in target geolocation accuracy for slow-moving targets SNR (db) MIMO also provides better geolocation for fast-moving targets Better geolocation accuracy, fewer false alarms, robustness to jamming SB82-2/JSB 9/15-6

7 ZPY-4 Based MIMO Demonstration Unit New MIMO Architecture Laboratory Hardware full aperture beams same as Doppler Domain Multi-Access (DDMA) High power RF switches and phase shifters Fabricated by Microwave Applications Group (MAG) subarray 1 subarray 2 fixed phase shifts (time delays) 9 9 switching pulse-topulse Tx waveform (½ power into each path) Final integration and laboratory testing completed 7/14 SB82-2/JSB 9/15-7

8 Background Data Collection Summary Processing Results Next Phase Outline SB82-2/JSB 9/15-8

9 ISL Proprietary/SBIR Data covered by rights statement on cover page of this briefing Data Collection Overview MTS locations and GPS ground truth for test target test site radar passes Good data collected 4/3/15 and 5/4/15 8 radar passes (4 water, 4 land) MIMO and baseline GMTI data Endo-clutter MTS target for most over-land passes Instrumented GPS vehicle (4 door sedan) for half the overland passes Many targets of opportunity SB82-2/JSB 9/15-9

10 Example Clutter Maps MIMO channel Doppler (hz) Doppler (hz) MIMO: Water relative power (db) 12 1 Baseline GMTI: Water 8 6 MIMO channel Doppler (hz) relative power (db) relative power (db) MIMO channel Doppler (hz) Baseline GMTI: Land Doppler (hz) MIMO: Land relative power (db) MIMO channel Doppler (hz) relative power (db) relative power (db) SB82-2/JSB 9/15-1

11 Background Data Collection Summary Processing Results Next Phase Outline SB82-2/JSB 9/15-11

12 MIMO Processing Flow IQ samples Form MIMO channels (forward and aft beams Mocomp apply calibration Range/Doppler process all Rx and Tx Channels MIMO-STAP Multi-bin post Doppler Element space (5 Dop bins, 2 Rx, 2 Tx channels) CACFAR Bearing estimation (MLE) SB82-2/JSB 9/15-12

13 MIMO Tx Beam Patterns relative power (db) model estimated from clutter data Patterns estimated from MIMO over-water clutter data NOTE: Simple motion compensation used to convert Doppler axis to azimuth angle azimuth (deg.) SB82-2/JSB 9/15-13

14 Tx Calibration 8 Tx Channel 1 Tx Channel 2 Tx Beamformed rel. power (db) rel. power (db) rel. power (db) azimuth (deg.) azimuth (deg.) azimuth (deg.) 2 Tx channels were successfully combined (beamformed) to produce a pattern with sidelobes and beamwidth similar to the GMTI mode rel. phase between Tx channels (deg CPI Index 5-5 Antenna broadside SB82-2/JSB 9/15-14

15 Tx Calibration (cont.) relative power (db) noise GMTI - single chan. MIMO - Tx beamformed azimuth (deg.) Two Tx channels combined to form a narrow, low sidelobe beam in the antenna boresight direction Tx pattern formed in the signal processor using the two available Tx channels Beamwidth and sidelobes similar to GMTI transmit pattern SB82-2/JSB 9/15-15

16 ISL Proprietary/SBIR Data covered by rights statement on cover page of this briefing Targets of Opportunity Many targets of opportunity detected.4 Range re. MTS location (nmi).3 Targets on road in test area Note significant micro-doppler Target Doppler (mph) 4 6 Conventional beamforming CFAR normalization Largest targets have SNR order of 3 db SB82-2/JSB 9/15-16

17 Single CPI Bearing Estimates 5.2 Targets on road in test area range (nmi.) detections road Doppler (hz) azimuth (deg.) Bearing estimates of targets of opportunity correlate well with the road We used the road data to compute and error between the estimated bearing and true target bearing SB82-2/JSB 9/15-17

18 Exo-Clutter Geolocation Estimates STAP Conventional road latitude (deg.) Red: MIMO Blue: GMTI latitude (deg.) longitude (deg.) Targets with SNR > 3 db Doppler between 3 Hz and 1 Hz Single pass longitude (deg.) SB82-2/JSB 9/15-18

19 Exo-Clutter Bearing Errors MIMO, STAP MIMO, Conv. GMTI, STAP GMTI, Conv..8 bearing error (deg.) SNR (db) Single pass SB82-2/JSB 9/15-19

20 MTS Conventional w/ CACFAR normalization Doppler (hz) STAP MTS return MTS Doppler: 97 Hz (3 kts) Radar data centered at MTS physical location MTS observed in STAP output Note: Doppler axis is flipped in radar dara Doppler (hz) SB82-2/JSB 9/15-2

21 Endo-Clutter Bearing Errors bearing error (deg.) MIMO GMTI SNR (db) MIMO provides Greater than 2x improvement in bearing accuracy at higher SNRs SB82-2/JSB 9/15-21