title: Comparison of a subrank to a full-rank time-reversal operator in a dynamic ocean.
abstract: This paper investigates the application of time-reversal techniques to the detection and ensonification of a target of interest. The focusing method is based on a generalization of time-reversal operator techniques. A subrank time-reversal operator is derived and implemented using a discrete set of transmission beams to ensonify a region of interest. In a dynamic ocean simulation, target focusing using a subrank matrix is shown to be superior to using a full-rank matrix, specifically when the subrank matrix is captured in a period shorter than the coherence time of the modeled environment. Backscatter from the point target was propagated to a vertical 64-element source-receiver array and processed to form the sub-rank time-reversal operator matrix. The eigenvector corresponding to the strongest eigenvalue of the time-reversal operator was shown to focus energy on the target in simulation. Modeled results will be augmented by a limited at-sea experiment conducted on the New Jersey shelf in April-May 2004 measured low-frequency backscattered signal from an artificial target (echo repeater).
authors.affiliation: Acoustics Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375-5320, USA. geoffrey.edelmann@nrl.navy.mil
authors.forename: Geoffrey F
authors.initials: GF
authors.lastname: Edelmann
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Lingevitch
authors.forename: Charles F
authors.initials: CF
authors.lastname: Gaumond
authors.forename: David M
authors.initials: DM
authors.lastname: Fromm
authors.forename: David C
authors.initials: DC
authors.lastname: Calvo