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

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Spatial Beamforming Direction (Angle) of Arrival (DOA)

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Matched Field Processing

Matched Field Processing 3D (Range,depth, bearing) Localization*1

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Matched Field Tomography Modal Information Environmental Info.

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Synthetic Aperture Matched Field Processing

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source at 76 m towed at 2.5 m/s from 9.18 km

Space Time Matched Field Processing

Matched Field Processing

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Space Time Matched Field Processing

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Localization & Doppler (velocity) Discrimination

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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.

Azi

mu

th (

deg

)

0

90

180

Doppler (Hz)-fmax 0 fmax

Doppler (Hz)-fmax 0 fmax

Target

Target

Clutter (Bottom Bounce)

Clu

tter

(Bot

tom

Rev

erbe

ratio

n)

JammerJammer(own-ship)

FW

DA

FT

STAP

Detect the dot Null the Jammer and the slanted clutter

STAMP

Detect/combine/class/localize the dots Null the Jammer and the clutter

PassiveForward-sector processing

Cm ,fm

fm=f0*v/cm

Higher Mode (Path,Angle), Larger cm

Larger cm, Higher Angle (off horizontal), Smaller Doppler

C1 ,f1

Multi-path Doppler/Angle Spread

OUTLINE

• STAMP Processing

• Simulation scenario for forward-sector processing

• Simulation Results

Br(f0)

Beam-space replica

(Selected Beams and Dopplers)

Phone 1Line 1 x11(t)

Phone nLine 1 xn1(t)

Doppler Processing

X1(f)

Conventional Beamforming

B1(f)B(f)

Beam-Space Vector

(selected Beamsand Dopplers)

WB/NBAdaptive

MFP

Doppler Processing

Xr (f)

Conventional Beamforming

Br(f)

Phone 1Line k x1k(t)

Phone nLine k xnk(t)

Doppler Processing

Xk(f)

Conventional Beamforming

Bk(f)

Propagation Code to generate

Replicaxr(t)

OutputAmbiguity

SurfaceR,Zv

Space-Time Adaptive Matched-field Processing (STAMP)

SearchR,Zv

Forming Covariance

Matrix

R = < B(f) B+(f)>f

&Decomposition

B(f) = [B1(f)…. B1(f+mf),…….., Bk(f)…. Bk(f+mf)]

Bk(f) = [bk(f,1)…… bk(f,l)]

AELEnviron.

*Plane-wave ~ STAP

Adaptive Processing

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w.r.t.Minimize

WWRWW

W

S

ARA

ARW

1

1

ARA 11

S

Adaptive Weight Vector

Adaptive Output

**A is the steering vector**R is the measured covariance matrix

ttt )()( xxR

High resolutionSidelobe suppressionSubject to mismatch – Robust Methods(widen the peak)

Wideband-Narrowband (WB/NB) Feedback-Loop White-Noise-Constrained (FLWNC)

Adaptive Processing

Br(f0)

Beam-space replica

(Selected Beams and Dopplers)

Covariance Matrix

R = < B(f) B+(f)>f

&Decomposition

VVλ nn

nnR

BRB

BRBBR

r1

r

r1

r

r1

1S

w

δw 2

1

2

BRB

BRRB

BRBBR

r 1

r

r 11

r

r 1

r

r 1

RS

w

2

δw 2

2

2

Adaptiveweight

W

VVλ

R nn

nn

1- 1

yes= s

yes= s

no

no

WB/NBProcessingS(f)=W+B(f)

* B(f) is “narrowband” (single f) R and W are “broadband” (averaged over band of f)

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

3 kts

towed array

own-ship noise

bottom bounce

10 km

188 m

Single-Line

4-Line-Sequential

4-Line-Vertical

No environmental mismatch

Single-Line BTRs of Each Signal ComponentForward Endfire at 0o

Own-Ship Noise Bottom Bounce

Target

__ Own-ship__ Bottom Bounce__ Target

Responses at 10o Azimuth

Single-Line Doppler/Azimuth Responses integration time =256-sec, Target Range=10 km, Forward Endfire at 0o

Own-Ship Noise Bottom Bounce

Target

__ Own-ship__ Bottom Bounce__ Target

Selected beams (0o-30o) &

Dopplers (6 bins for 6-kt search)

Responses at 10o Azimuth

Single-Line Beam/Cell Spectrograms

Conventional Plane-Wave (10o) Adaptive Plane-Wave (10o)

Adaptive MFP (target track)

__ Adaptive PW__ Adaptive MFP

Peak Level over Dopplers

Adaptive Beam/Cell Spectrograms

Adaptive Plane-Wave (10o) Single Vertical Adaptive MFP

4_Line_Vertical Adaptive MFP

__ PW__ Single Line MFP__ 4_Line_Vert MFP

Peak Level over Dopplers

Single Line, Conventional MFP

4_Line_Sequential, Adaptive MFP 4_Line_Vertical, Adaptive MFP

Single Line, Adaptive MFP

Array Size Dependence of MFP Range Tracking search at target depth and target speed

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

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

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.