Experimental subwavelength localization of scatterers by decomposition of the time reversal operator interpreted as a covariance matrix.

The D.O.R.T. method (French acronym for Decomposition of the Time Reversal Operator) is an active remote sensing technique using arrays of antennas for the detection and localization of scatterers [Prada et at., J. Acoust. Soc. Am. 99, 2067-2076 (1996)]. The analogy between the time reversal operator and the covariance matrix used for classical sources separation in passive remote sensing [Bienvenu et al., IEEE Trans. ASSP 31, 1235-1247 (1983)] is established. Then, an experiment of subwavelength detection and localization of point-like scatterers with a linear array of transducers is presented. Using classical estimators in reception like Maximum-Likelihood and Multiple Signal Characterization (MUSIC), two point-like scatterers separated by lambda/3 and placed at 100lambda from the array of transducers are resolved. In these experiments, the role of multiple scattering and the existence of additional eigenvectors associated with dipolar and monopolar radiation of each scatterer is discussed.

[1]  Arthur B. Baggeroer,et al.  An overview of matched field methods in ocean acoustics , 1993 .

[2]  Margaret Cheney,et al.  The Linear Sampling Method and the MUSIC Algorithm , 2001 .

[3]  R. Lombardi,et al.  Echo-graphic images enhanced through Walsh functions , 1997, 1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118).

[4]  Mathias Fink,et al.  Highly resolved detection and selective focusing in a waveguide using the D.O.R.T. method , 1999 .

[5]  Mathias Fink,et al.  Decomposition of the time reversal operator: Detection and selective focusing on two scatterers , 1996 .

[6]  Mathias Fink,et al.  Characterization of extended objects with the D.O.R.T. method , 1996, 1996 IEEE Ultrasonics Symposium. Proceedings.

[7]  R. O. Schmidt,et al.  Multiple emitter location and signal Parameter estimation , 1986 .

[8]  Mathias Fink,et al.  The iterative time reversal process: Analysis of the convergence , 1995 .

[9]  D H Chambers,et al.  Time reversal for a single spherical scatterer. , 2001, The Journal of the Acoustical Society of America.

[10]  C. Prada,et al.  Detection and imaging in complex media with the D.O.R.T. method , 2000, 2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121).

[11]  Mathias Fink,et al.  Flaw detection in solid with the D.O.R.T. method , 1997, 1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118).

[12]  G. Bienvenu,et al.  Optimality of high resolution array processing using the eigensystem approach , 1983 .

[13]  Marc Saillard,et al.  Decomposition of the Time Reversal Operator for Electromagnetic Scattering , 1999 .

[14]  Mathias Fink,et al.  Eigenmodes of the time reversal operator: a solution to selective focusing in multiple-target media , 1994 .