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

3 GMTI and Small UAVs Air Force JSTARS ~27 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 ISL Proprietary/SBIR Data covered by rights statement on cover page of this briefing Aircraft Integration 2- channel GMTI array in lab test fixture GMTI array installed on Telephonics King Air 2 SB82-2/JSB 9/15-8

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

10 Phase Shifter Insertion Loss ~.4 db Fabricated by Microwave Applications Group (MAG) New Test First Test MAG modified the phase shifter with new Garnet material Eliminated large insertion loss at high power SB82-2/JSB 9/15-1

11 RDR 17B - Two Channel Antenna Feed Network RDR-17B Two Channel Antenna Feed Network J3 A ½ Height WR-9 Coupling Phase Shifter Phase Shifter Coupling J2 A ½ Height WR-9 Left Right J3 B ½ Height WR-9 J7 P9 P1 J6 J2 B ½ Height WR-9 J5 to GMTI Rcvr J1 WR-9 Tx J8 to GMTI Rcvr Cable Noise Source Phase Trimmer Cable J4 Note: Yellow J Numbers = Reassigned Number SB82-2/JSB 9/15-11

12 MIMO MIMO Test Setup Antenna Pedestal #2 (Rotating) 28VDC AP Interface 28VDC 28VDC 2VDC (+/-2VDC, 4Hz, AP Control) Signal Processor Receiver Transmitter Right Channel Rx Antenna Pedestal #1 (Stationary) SPORT Interface GMTI Switch Ctrl Noise Source Ctrl MIMO Enable Fiber Interface Left Phase Shift Ctrl Right Phase Shift Ctrl Left Channel Rx Load J5 J3-A MIMO Array J8 J2-A Load J3-B J1 J2-B ODL #1 ODL #2 RF Out RF Power Control SB82-2/JSB 9/15-12

13 High Power Testing (no antenna) Tx input (high power) termination loads optical delay line Phase shifters Rx signals (to ZPY-4) Phase shifter power and control Final integration and laboratory testing completed 7/14 SB82-2/JSB 9/15-13

14 Phase Shifter Results Measured phase difference between two Rx channels is 9 degrees as expected The phase difference errors are small SB82-2/JSB 9/15-14

15 SBIR Data covered by rights statement on cover page of this briefing ISL Proprietary/SBIR Data covered by rights statement on cover page of this briefing Fire Scout Two-Channel GMTI Antenna with MIMO Mode Modifications SB82-2/JSB 9/15-15

16 Background Hardware Summary Data Collection Summary Processing Results Next Phase Outline SB82-2/JSB 9/15-16

17 Test Goals Goal #1: Measured Tx antenna patterns match patterns measured in the chamber (see slide 1) Goal #2: Demonstrate that MIMO system provides better than 5:1 beamsplit ratio for endo-clutter targets (see slide 17) Goal #3: Demonstrate that MIMO and GMTI systems provide the same probability of detection for exo-clutter targets (no data available to test this, although qualitative results using targets of opportunity indicate we are meeting this goal) Demonstrate the MIMO provides 2.5x reduction in bearing errors relative to GMTI for 2 db endo-clutter targets (see slide 19) SB82-2/JSB 9/15-17

18 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 9/15-18

19 Data Summary Date Flt # Time (EDT) Mode Clutter comments 12/11/14 1 AM GMTI MIMO land water No valid data. Was not able to pulse compress and Doppler process data to for valid clutter maps 2 PM GMTI MIMO land water 4/3/ : GMTI land water 2 17: MIMO land water Limited valid MIMO data. Clutter maps useful for qualitative assessment of MIMO Tx patterns. No GPS/INS Good data. Antenna not scanning for over-land pass. Limited CPIs with MTS Good data. 5/4/15 1 9:3 MIMO GMTI land water Good data. 2 11:3 MIMO land water Good data. ~8 GB of data collected SB82-2/JSB 9/15-19

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

21 Background Hardware Summary Data Collection Summary Processing Results Next Phase Outline SB82-2/JSB 9/15-21

22 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 9/15-22

23 8 Rx Calibration Single Rx Channel Beamformed (no cal) Beamformed (w/ cal) range (nmi) rel. power (db) range (nmi) rel. power (db) range (nmi) rel. power (db) azimuth (deg.) azimuth (deg.) azimuth (deg.) -7 Over water GMTI data used to calibrate the two-channel Rx antenna Eigen-analysis based cal-on-clutter algorithm chan. -to-chan.phase error (deg.) Over-water calibration errors used to process the over-land data GMTI data set 21543_2117 (over water) used to calibrate the array CPI index SB82-2/JSB 9/15-23

24 Rx Calibration (cont.) relative power (db) Tx pattern 1 chan. BF w/o cal. BF w/ cal azimuth (deg.) Single over-land GMTI data set averaged over all ranges Rx calibration results in desired narrow two-way antenna pattern for beamformer ( BF ) results Cal errors estimated using water-only data and applied to over-land data set SB82-2/JSB 9/15-24

25 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 9/15-25

26 Tx Calibration 8 Tx Channel 1 Tx Channel 2 Tx Beamformed range (nmi) rel. power (db) range (nmi) rel. power (db) range (nmi) 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 9/15-26

27 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 9/15-27

28 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 9/15-28

29 Single CPI Bearing Estimates 5.2 Targets on road in test area range (nmi) 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 9/15-29

30 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 9/15-3

31 Exo-Clutter Bearing Errors MIMO, STAP MIMO, Conv. GMTI, STAP GMTI, Conv..8 bearing error (deg.) SNR (db) Single pass SB82-2/JSB 9/15-31

32 MTS Conventional w/ CACFAR normalization -.2 range (nmi) 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 range (nmi) Doppler (hz) SB82-2/JSB 9/15-32

33 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 9/15-33

34 Background Hardware Summary Data Collection Summary Processing Results Next Phase Outline SB82-2/JSB 9/15-34