Resolution enhancement and separation of reverberation from target echo with the time reversal operator decomposition.

Time reversal operator (TRO) decompositions are performed in a model of an ocean wave guide containing a target and having different kinds of bottom. The objective is to study the effects of bottom reverberation and absorption by means of ultrasonic experiments. It is shown experimentally that the echo from a target can be separated from the bottom reverberation. Reverberation eigenvectors are back propagated in the wave guide leading to focus on the bottom. An amplitude correction is applied to both reverberation and signal eigenvectors to compensate for bottom absorption and thus to improve target resolution.

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

[2]  W. Kuperman,et al.  A long-range and variable focus phase-conjugation experiment in shallow water , 1999 .

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

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

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

[6]  J. L. Thomas,et al.  Focusing and steering through absorbing and aberrating layers: application to ultrasonic propagation through the skull. , 1998, The Journal of the Acoustical Society of America.

[7]  W. Kuperman,et al.  Phase conjugation in the ocean: Experimental demonstration of an acoustic time-reversal mirror , 1998 .

[8]  W. Kuperman,et al.  Time reversed reverberation focusing in a waveguide. , 2002, The Journal of the Acoustical Society of America.

[9]  Mathias Fink,et al.  Time-reversal in an ultrasonic waveguide , 1997 .

[10]  D. Jackson,et al.  Phase conjugation in underwater acoustics , 1991 .

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

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

[13]  H C Song,et al.  Adaptive time-reversal mirror. , 2001, The Journal of the Acoustical Society of America.

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