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Yung P. Lee (ASAP 2001, March 14, 2001) Science Applications International Corporation 1710 SAIC Drive McLean, VA 22102 Yung@osg.saic.com Space-Time Adaptive Matched-field Processing (STAMP)
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Fourier Transform Spectral (Frequency) Content Sonar Signal Processing Background Spatial Beamforming Direction (Angle) of Arrival (DOA)
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Matched Field Processing Matched Field Processing 3D (Range,depth, bearing) Localization Matched Field Tomography Modal Information Environmental Info.
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Synthetic Aperture Matched Field Processing source at 76 m towed at 2.5 m/s from 9.18 km
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Space Time Matched Field Processing Matched Field Processing Space Time Matched Field Processing Localization & Doppler (velocity) Discrimination Phone-Doppler Space Beam-Doppler Space
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BACKGROUND/OBJECTIVE Space-Time Adaptive Processing (STAP) coherently combines signals from the elements of an array and the multiple snapshots of signals, to achieve large spatial/temporal signal gain, to suppress interference, and to provide target detection in azimuth and velocity. Matched-field processing (MFP) coherently combines complex multi-path arrivals, to recover signal multi-path spreading loss and to provide range/depth localization. STAMP combines STAP and MFP to improve detection and localization performance for the mobile multi-line-towed-array sonar systems.
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Azimuth (deg) 0 90 180 Doppler (Hz) - f max 0 f max Doppler (Hz) - f max 0 f max Target Clutter (Bottom Bounce) Clutter (Bottom Reverberation) Jammer (own-ship) FWD AFT STAP Detect the dot Null the Jammer and the slanted clutter STAMP Detect/combine/class/localize the dots Null the Jammer and the clutter Passive Forward-sector processing
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C m, f m f m =f 0 *v/c m Higher Mode (Path,Angle), Larger c m Larger c m, Higher Angle (off horizontal), Smaller Doppler C 1, f 1 Multi-path Doppler/Angle Spread
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OUTLINE STAMP Processing Simulation scenario for forward-sector processing Simulation Results
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B r (f 0 ) Beam-space replica (Selected Beams and Dopplers) Phone 1 Line 1 x 11 (t) Phone n Line 1 x n1 (t) Doppler Processing X 1 (f) Conventional Beamforming B 1 (f) B(f) Beam-Space Vector (selected Beams and Dopplers) WB/NB Adaptive MFP Doppler Processing X r (f) Conventional Beamforming B r (f) Phone 1 Line k x 1k (t) Phone n Line k x nk (t) Doppler Processing X k (f) Conventional Beamforming B k (f) Propagation Code to generate Replica x r (t) Output Ambiguity Surface R,Z v Space-Time Adaptive Matched-field Processing (STAMP) Search R,Z v Forming Covariance Matrix R = f & Decomposition B(f) = [B 1 (f)…. B 1 (f+m f),…….., B k (f)…. B k (f+m f)] B k (f) = [b k (f, 1 )…… b k (f, l )] AEL Environ. *Plane-wave ~ STAP
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Adaptive Processing Adaptive Weight Vector Adaptive Output **A is the steering vector **R is the measured covariance matrix High resolution Sidelobe suppression Subject to mismatch – Robust Methods (widen the peak)
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Wideband-Narrowband (WB/NB) Feedback-Loop White-Noise-Constrained (FLWNC) Adaptive Processing B r (f 0 ) Beam-space replica (Selected Beams and Dopplers) Covariance Matrix R = f & Decomposition Adaptive weight W yes = s yes = s no WB/NB Processing S(f)=W + B(f) * B(f) is “narrowband” (single f) R and W are “broadband” (averaged over band of f)
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Simulation Geometry (F=200 Hz) target(NB)=120 dB, own-ship(BB)=120 dB, bottom bounce(BB)=115 dB WNL=70 dB, 0.1 random phase error 3 kts towed array own-ship noise bottom bounce 10 km 188 m Single-Line 4-Line-Sequential 4-Line-Vertical No environmental mismatch
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Single-Line BTRs of Each Signal Component Forward Endfire at 0 o Own-Ship NoiseBottom Bounce Target __ Own-ship __ Bottom Bounce __ Target Responses at 10 o Azimuth
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Single-Line Doppler/Azimuth Responses integration time =256-sec, Target Range=10 km, Forward Endfire at 0 o Own-Ship NoiseBottom Bounce Target __ Own-ship __ Bottom Bounce __ Target Selected beams (0 o -30 o ) & Dopplers (6 bins for 6-kt search) Responses at 10 o Azimuth
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Single-Line Beam/Cell Spectrograms Conventional Plane-Wave (10 o )Adaptive Plane-Wave (10 o ) Adaptive MFP (target track) __ Adaptive PW __ Adaptive MFP Peak Level over Dopplers
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Adaptive Beam/Cell Spectrograms Adaptive Plane-Wave (10 o )Single Vertical Adaptive MFP 4_Line_Vertical Adaptive MFP __ PW __ Single Line MFP __ 4_Line_Vert MFP Peak Level over Dopplers
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Single Line, Conventional MFP 4_Line_Sequential, Adaptive MFP4_Line_Vertical, Adaptive MFP Single Line, Adaptive MFP Array Size Dependence of MFP Range Tracking search at target depth and target speed
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Depth Discrimination of Adaptive MFP Range Tracking 4_Line_Vertical Array search at target speed Depth=10 m Depth=180 mDepth=90 m Depth=60 m
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Speed= 3 m/s Speed= -3 m/sSpeed= -1 m/s Speed= 1 m/s Speed Discrimination of Adaptive MFP Range Tracking 4_Line_Vertical Array search at target depth
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SUMMARY STAMP processing that combines STAP and MFP has been developed. Simulations show that STAMP coherently combines signal multi- path spread in azimuth and Doppler and greatly enhances target detection as well as providing target range and depth classification and localization.
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