Experimental detection and focusing in shallow water by decomposition of the time reversal operator

Prada, Claire; Rosny, Julien de; Clorennec, Dominique; Minonzio, Jean‐Gabriel; Aubry, Alexandre; Fink, Mathias; Berniere, L.; Billand, Philippe; Hibral, Sidonie; Folégot, Thomas

doi:10.1121/1.2749442

Cited by 57 publications

(33 citation statements)

References 14 publications

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“…Indeed, the SVD permits the decomposition into orthogonal signal and noise subspaces. It has been shown that the SNR increases as the square-root of the number of antennas for a given power emitted by the Tx array [9]. Furthermore, the use of the MUSIC estimator, unlike classical time reversal, allows the resolution of two close scatterers.…”

Section: Discussionmentioning

confidence: 99%

“…The method was first developed for ultrasonic applications with arrays of piezo-electric transceivers [6][7][8]. It has shown its efficiency in several domains like non-destructive evaluation [8], detection in shallow water [9] and medical imaging [10]. The DORT method can be applied to all types of linear waves and has been employed in electromagnetism since 2001 [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

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Detection and Imaging of Human Beings Behind a Wall Using the Dort Method

Davy¹,

Lepetit²,

Rosny³

et al. 2010

PIER

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Abstract-In recent years, through the wall imaging has become a topic of intense research due to its promising applications in police, fire and rescue or emergency relief operations. In this paper, we propose to use the DORT method (French acronym for Decomposition of the Time Reversal Operator) to detect and localize a moving target behind a wall. One of the DORT method major strengths is that detection remains possible through a distorting medium. In this paper, the DORT method is successfully applied to detect and track moving human beings behind a thick concrete wall. The smallest detectable displacement is also investigated.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Detection and Imaging of Human Beings Behind a Wall Using the Dort Method

Davy¹,

Lepetit²,

Rosny³

et al. 2010

PIER

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“…It was shown that the number of nonzero singular values (SVs) of the MDM provides the number of point-like targets and the corresponding singular vectors give the monochromatic Green function from the array to the targets associated. 10,13,14 Indeed at pulsation frequency , the singular vector u p is related to the Green's function G p connecting the array to the pth target's position r p by…”

Section: Phase Synchronization Of the Eigenvectors Of Tro: Theorymentioning

confidence: 99%

Construction of the temporal invariants of the time-reversal operator

Philippe¹,

Prada²,

Clorennec³

et al. 2009

The Journal of the Acoustical Society of America

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This paper proposes a method to construct the temporal Green's function from a scatterer to an array of transducers in a waveguide using freespace back propagation of the eigenvectors of the time-reversal operator (TRO). The monostatic Green's function is obtained as an eigenvector of the TRO which is known with an arbitrary phase; thus the impulse response cannot be obtained by a simple inverse Fourier transform. Assuming that the monochromatic fields obtained by the back propagation of the eigenvectors are in phase at the focal point, the phase correction is determined. Simulations and laboratory experiments are presented.

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“…To solve the above problem, an echo-to-reverberation enhancement method based on decomposition of the time reversal operator (DORT) [12][13][14][15][16] with forward and backward reverberation nulling has been proposed [17]. This method can focus sound energy at the target while nulling the energy at the bottom near the target range simultaneously, substantially enhancing the echo-to-reverberation ratio without a probe source and prior knowledge about the relative scattering intensity of target and bottom.…”

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Reverberation nulling and echo enhancement at low frequency using waveguide invariance

2011

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Based on the fact that the transfer function vector between a source receiver array and the dominant scatterer of boundary reverberation at a range can be obtained from the corresponding reverberations scattered from this range cell, a reverberation nulling concept using time reversal processing has been proposed. However, current reverberation nulling methods have certain limitations when applied into practice, which would null boundary reverberation and target echo simultaneously. As a solution, a passive reverberation nulling and echo enhancement method at low frequency using waveguide invariance is proposed in this paper. In this method, the reverberation subspace for the target range cell is not obtained directly from the return signals scattered by the target range cell but from the return signals scattered by a range cell located before the target using waveguide invariance, so as to suppress the reverberation embodied in the target echo by passive reverberation nulling. Besides, a range-dependent optimal weighting vector rather than conventional projector matrix is deduced to null the reverberation component meanwhile maximizing the target echo, thereby enhancing the echo-to-reverberation ratio furthest. Numerical simulations in typical range-independent shallow water environment demonstrate the efficacy and the improved performance of the proposed method for echo-to-reverberation enhancement.reverberation nulling, echo-to-reverberation enhancement, waveguide invariance, time reversal

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Experimental detection and focusing in shallow water by decomposition of the time reversal operator

Cited by 57 publications

References 14 publications

Detection and Imaging of Human Beings Behind a Wall Using the Dort Method

Detection and Imaging of Human Beings Behind a Wall Using the Dort Method

Construction of the temporal invariants of the time-reversal operator

Reverberation nulling and echo enhancement at low frequency using waveguide invariance

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