Backpropagation image analysis of broadband decomposition of the time reversal operator (DORT) data from TREX-04

Abstract

Single-frequency DORT is a method of isolating scatterers with a multiple-source/multiple-receiver system [C. Prada et al., J. Acoust. Soc. Am. 99, 2067–2076 (1996)]. Broadband DORT overcomes problems of frequency fading and dispersion by exploiting the response of singular values across the entire signal bandwidth. In spring 2004, the Time Reversal Experiment, TREX-04, collected data for the evaluation of the broadband DORT technique. An 80 m vertical source/receiver array with 64 hydrophones was deployed in 100 m deep water in an area south of Hudson Canyon off the New Jersey coast. Sets of four, five, or six beams were transmitted at small angles from horizontal and the response from an echo repeater was recorded on 64 channels. Data was collected in 500 Hz bands between 500 and 3500 Hz with the echo repeater at ranges from 0.5 to 5.0 km and at mid-water column and near-bottom depths. Applying the broadband DORT algorithm, the isolation of the echo repeater signal in the singular vectors and the robustness of broadband backpropagation images will be presented as a function of frequency band, signal coherence, echo repeater range and depth, noise levels, and receiver aperture. [Work supported by the ONR.]