Time-domain beam signals for adaptive beamforming UDT 2019, - - PowerPoint PPT Presentation

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Time-domain beam signals for adaptive beamforming UDT 2019, - - PowerPoint PPT Presentation

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Time-domain beam signals for adaptive beamforming UDT 2019, Stockholm - 13th May a sound decision a sound decsion The ATLAS ELEKTRONIK Group/ 1 Table of contents Motivation For adaptive beamforming ATLAS Approach

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SLIDE 1

The ATLAS ELEKTRONIK Group/ 1

… a sound decsion … a sound decision

Time-domain beam signals for adaptive beamforming UDT 2019, Stockholm - 13th May

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SLIDE 2

The ATLAS ELEKTRONIK Group/ 2

Table of contents

  • Motivation
  • For adaptive beamforming
  • ATLAS Approach
  • Robust MPDR (Minimum Power Distortionless Response)
  • Robust MPDR with time-domain signals
  • Simulated data
  • Sea trial data
  • Summary
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SLIDE 3

The ATLAS ELEKTRONIK Group/ 3

Table of contents

  • Motivation
  • For adaptive beamforming
  • ATLAS Approach
  • Robust MPDR (Minimum Power Distortionless Response)
  • Robust MPDR with time-domain signals
  • Simulated data
  • Sea trial data
  • Summary
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SLIDE 4

The ATLAS ELEKTRONIK Group/ 4

Motivation Basics of Beamforming

∑ Δ𝜐1 Δ𝜐2 Δ𝜐𝑂

…

time delay beam time series beamformer

  • Joint processing of array outputs:
  • Enhanced detection of weak signals
  • Spatial discrimination of wave fronts
  • Spatial sensitivity depends on:
  • Array geometry
  • Frequency
  • Desired look-direction
  • Beamformer (BF)
  • Example: „Delay & Sum“ Beamformer
  • BF coefficients = time delays Δ𝜐𝑜
  • Choice of Δ𝜐𝑜 according to desired look-direction
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SLIDE 5

The ATLAS ELEKTRONIK Group/ 5

Motivation Beamforming Characteristics  Beampattern

beam time series Ƹ 𝑡(𝑢) Desired look-direction = 90° Incoming wave front

  • Bearing = 90°
  • modulated by signal 𝑡(𝑢)
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SLIDE 6

The ATLAS ELEKTRONIK Group/ 6

Motivation Beampattern – Mainlobe

beam time series Ƹ 𝑡(𝑢) Mainlobe width  target separation Mainlobe gain  target detection

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SLIDE 7

The ATLAS ELEKTRONIK Group/ 7

Motivation Beampattern – Sidelobes

Contains all acoustic signatures „collected“ with the beampattern! beam time series Ƹ 𝑡(𝑢)

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The ATLAS ELEKTRONIK Group/ 8

Motivation Disadvantage of non-adaptive Beamformers

beam time series Ƹ 𝑡(𝑢) Silent target Loud target Contributions of loud target received via sidelobe @ 60°… …mask contributions of silent target in Ƹ 𝑡(𝑢)  silent target might not be detected! …are erroneously assigned to bearing of 45°  incorrect bearing for loud target! silent target + loud target + noise

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The ATLAS ELEKTRONIK Group/ 9

Motivation Idea of adaptive Beamforming (ABF)

beam time series Ƹ 𝑡(𝑢)

  • Adapt beamformer coefficients such that directional zeros are formed in

directions of interferers.

  • Derive information about interferers from data itself.
  • Perform adaptation of BF coefficients for each desired look-direction.

silent target + noise Silent target Loud target

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SLIDE 10

The ATLAS ELEKTRONIK Group/ 10

Table of contents

  • Motivation
  • For adaptive beamforming
  • ATLAS Approach
  • Robust MPDR
  • Robust MPDR with time-domain signals
  • Simulated data
  • Sea trial data
  • Summary
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SLIDE 11

The ATLAS ELEKTRONIK Group/ 11

Basic idea of MPDR

  • Select BF coefficients such that:
  • Signal from look-direction remains undistorted
  • Total power of beam time series is minimized
  • Required information:
  • Covariance matrix of stave data (correlation of stave outputs)
  • Robust design of processing:
  • Introduce tolerance regions such that signals from a sector around look-

direction remain undistorted  prohibits suppression of targets between two look-directions

  • Calculate output power directly from steering vectors:
  • Matrix with dimension #beams x #frequency bands
  • Low time resolution (~ 1 Hz)

ATLAS Approach Robust Minimum Power Distortionless Response (MPDR)

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SLIDE 12

The ATLAS ELEKTRONIK Group/ 12

ABF Current Version

  • ABF for BDT processing
  • Conventional beamforming for BDT processing and others

ATLAS Approach Robust Minimum Power Distortionless Response (MPDR)

Covariance matrix Adaptive steering vectors Conventional beamforming BDT BDT e.g. LOFAR Antenna-Lan Power ABF

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SLIDE 13

The ATLAS ELEKTRONIK Group/ 13

ABF New design

  • ABF for BDT processing
  • Adaptive time-domain beamforming for BDT processing and others

ATLAS Approach Robust Minimum Power Distortionless Response (MPDR)

Covariance matrix Adaptive steering vectors Adaptive time-domain beamforming BDT BDT e.g. LOFAR Antenna-Lan Power ABF

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SLIDE 14

The ATLAS ELEKTRONIK Group/ 14

Table of contents

  • Motivation
  • For adaptive beamforming
  • ATLAS Approach
  • Robust MPDR
  • Robust MPDR with time-domain signals
  • Simulated data
  • Simple scenario
  • LOFAR / DEMON results
  • Sea trial data
  • Summary
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SLIDE 15

The ATLAS ELEKTRONIK Group/ 15

Scenario:

  • 4 broadband targets
  • Each has a strong frequency line

Conventional Beamforming:

  • Target width depends on frequency
  • Sidelobes due to broadband signature
  • Strong sidelobe structure due to

frequency lines

Simulated data Simple scenario for a flank array sonar

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SLIDE 16

The ATLAS ELEKTRONIK Group/ 16

Scenario:

  • 4 broadband targets
  • Each has a strong frequency line

ABF Beamforming:

  • Constant power width for broad

frequency range

  • No sidelobes for broadband structure
  • No sidelobes for frequency lines
  • Improved performance
  • No time signals

Simulated data Simple scenario for a flank array sonar

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SLIDE 17

The ATLAS ELEKTRONIK Group/ 17

Scenario:

  • 4 broadband targets
  • Each has a strong frequency line

ABF Beamforming with time signals:

  • Constant power width for broad

frequency range

  • No sidelobes for broadband structure
  • No sidelobes for frequency lines
  • Nearly same performance as before
  • Time Signals are available

Simulated data Simple scenario for a flank array sonar

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The ATLAS ELEKTRONIK Group/ 18

Simulated data Low Frequency Analysis and Recording (LOFAR)

Intention: Analysis of frequency lines

  • Engines
  • Generators
  • Pumps

Signal Processing: LOFAR

Decimation Frequency analysis Normalization

𝑔

CFR: Cylinder firing rate

𝑔

EFR: Engine firing rate

𝑂C: Number of cylinders

𝑔

CFR

𝑔

EFR = 𝑔 CFR ∙ 𝑂C

𝑔 PD

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The ATLAS ELEKTRONIK Group/ 19

Simulated data LOFAR (bearing information)

5 simulated targets

  • Flank Array Sonar
  • Multiple target crossings

Delay-and-Sum

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SLIDE 20

The ATLAS ELEKTRONIK Group/ 20

Simulated data LOFAR (bearing information)

5 simulated targets

  • Flank Array Sonar
  • Multiple target crossings

Improved detection performance:

  • Improved target separation

Delay-and-Sum ABF

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SLIDE 21

The ATLAS ELEKTRONIK Group/ 21

Simulated data LOFAR (frequency information)

Simulation of frequency lines

  • Different SNR
  • Stable / unstable lines

Delay-and-Sum

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SLIDE 22

The ATLAS ELEKTRONIK Group/ 22

Simulated data LOFAR (frequency information)

Simulation of frequency lines

  • Different SNR
  • Stable / unstable lines

Improved detection performance:

  • Higher signal-to-noise-plus-interference ratio
  • Detection of more frequency lines possible

Delay-and-Sum ABF

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SLIDE 23

The ATLAS ELEKTRONIK Group/ 23

Simulated data Detection of Envelope Modulation on Noise (DEMON)

𝑔

PSR: Propeller shaft rate

𝑔

BR: Blade rate

𝑂B: Number of blades

𝑔

PSR

𝑔

BR = 𝑔 PSR ∙ 𝑂B

𝑔 PD DEMON

LOFAR Absolute value

Intention: Analysis of frequency lines from modulation

  • Cavitation

Signal processing:

Bubbles generated by propeller

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The ATLAS ELEKTRONIK Group/ 24

Simulated data DEMON

5 simulated targets

  • Flank Array Sonar
  • Multiple target crossings

Delay-and-Sum

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The ATLAS ELEKTRONIK Group/ 25

Simulated data DEMON

5 simulated targets

  • Flank Array Sonar
  • Multiple target crossings

Improved detection performance:

  • Superior target separation

Delay-and-Sum ABF

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SLIDE 26

The ATLAS ELEKTRONIK Group/ 26

Table of contents

  • Motivation
  • For adaptive beamforming
  • ATLAS Approach
  • Robust MPDR
  • Robust MPDR with time-domain signals
  • Simulated data
  • Sea trial data
  • Summary
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SLIDE 27

The ATLAS ELEKTRONIK Group/ 27

Sea trial data Broadband Detection (BDT)

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire

Delay-and-Sum

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SLIDE 28

The ATLAS ELEKTRONIK Group/ 28

Sea trial data Broadband Detection (BDT)

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire

Endfire

Delay-and-Sum

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SLIDE 29

The ATLAS ELEKTRONIK Group/ 29

Sea trial data Broadband Detection (BDT)

ABF

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire

Endfire Improved detection performance:

  • Higher signal-to-noise-plus-interference ratio
  • Improved target separation

Delay-and-Sum

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The ATLAS ELEKTRONIK Group/ 30

Sea trial data Broadband Detection (BDT)

ABF

Endfire

Delay-and-Sum

Improved detection performance:

  • Higher signal-to-noise-plus-interference ratio
  • Improved target separation

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire
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SLIDE 31

The ATLAS ELEKTRONIK Group/ 31

Sea trial data Low Frequency Analysis and Recording (LOFAR) (Maximum from frequeny domain)

Delay-and-Sum

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire
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SLIDE 32

The ATLAS ELEKTRONIK Group/ 32

Sea trial data Low Frequency Analysis and Recording (LOFAR) (Maximum from frequeny domain)

ABF Delay-and-Sum

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire

Improved detection performance:

  • Higher signal-to-noise-plus-interference ratio
  • Improved target separation
  • Detection of more target traces possible
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SLIDE 33

The ATLAS ELEKTRONIK Group/ 33

Sea trial data Low Frequency Analysis and Recording (LOFAR) (Maximum from frequeny domain)

ABF Delay-and-Sum

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire

Improved detection performance:

  • Higher signal-to-noise-plus-interference ratio
  • Improved target separation
  • Detection of more target traces possible
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SLIDE 34

The ATLAS ELEKTRONIK Group/ 34

Sea trial data Low Frequency Analysis and Recording (LOFAR) (Maximum from frequeny domain)

ABF Delay-and-Sum

≥ 14 target traces

  • Flank Array Sonar
  • 360°turn of the submarine
  • Reduced performance in endfire

Targets of interest Improved detection performance:

  • Higher signal-to-noise-plus-interference ratio
  • Improved target separation
  • Detection of more target traces possible
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The ATLAS ELEKTRONIK Group/ 35

Sea trial data LOFAR (Frequency detections)

Delay-and-Sum

frequency*

+ ∆

  • Frequency information removed

Frame number

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SLIDE 36

The ATLAS ELEKTRONIK Group/ 36

Sea trial data LOFAR (Frequency detections)

Delay-and-Sum ABF

frequency* frequency*

+ ∆ + ∆

  • Frequency information removed

Frame number Frame number Improved detection performance:

  • More frequency lines
  • Higher signal-to-noise-plus-interference ratio
  • Longer frequency lines
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The ATLAS ELEKTRONIK Group/ 37

Sea trial data LOFAR (Frequency detections)

Delay-and-Sum ABF

frequency* frequency*

+ ∆ + ∆

  • Frequency information removed

Interferences (different target) Frame number Frame number Improved detection performance:

  • More frequency lines
  • Higher signal-to-noise-plus-interference ratio
  • Longer frequency lines
  • Suppression of interferences
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SLIDE 38

The ATLAS ELEKTRONIK Group/ 38

Table of contents

  • Motivation
  • For adaptive beamforming
  • ATLAS Approach
  • Robust MPDR
  • Robust MPDR with time-domain signals
  • Simulated data
  • Sea trial data
  • Summary
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SLIDE 39

The ATLAS ELEKTRONIK Group/ 39

  • ATLAS Elektronik GmbH uses an approach to calculate time-domain signals with ABF
  • Design is based on existing ABF for BDT
  • Advantages of adaptive beamforming with time-domain signals:
  • Sonar operator can listen to the noise of targets only detected in BDT with ABF
  • Superior signal quality for DEMON + LOFAR and other signal processing chains

Summary

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The ATLAS ELEKTRONIK Group/ 40

ATLAS ELEKTRONIK GmbH Sebaldsbruecker Heerstrasse 235 28309 Bremen | Germany Phone: +49 421 457-02 Telefax: +49 421 457-3699 www.atlas-elektronik.com

Contact … a sound decision