Forward Scattering Observation With Partially Coherent Spatial Processing of Vertical Array Signals in Shallow Water

Abstract

In this paper, we address the problem of detecting an inhomogeneity in shallow water by observing changes in the acoustic field as the inhomogeneity passes between an acoustic source and vertical line array of receivers. A signal processing scheme is developed to detect the perturbed field in the presence of the much stronger primary source signal, and to estimate such parameters as the time when the inhomogeneity crosses the source-receiver path, its velocity, and its size. The effectiveness of incoherent, coherent, and partially coherent spatial processing of the array signals is evaluated using models and data obtained from experiments in a lake. The effect of different bottom types is also considered, and it is shown that partially coherent processing can have a significant advantage depending on the bottom type. Estimates of the minimum input signal-to-noise ratios (SNRs) for which the diffracted signal can be observed are presented.

Experimental Study of Acoustic Forward Scattering on a Marine Shelf

“…Although relatively simple, this model has been useful for constructing algorithms for matched signal processing [4], and is the basis for the development of more refined models. Analytical calculations using the scattering matrix for a shallow sea, numerical simulations [2,3], and work by Kuz'kin et al as summarized in [9], have confirmed the validity of the proposed approach.…”

“…This processing yielded the best performance for detection and parameter estimation. Parameters include the length and cross-section area of inhomogeneity, its velocity and range, and the intersection instant [6][7][8][9]. Coherent spatial-temporal processing for horizontal receiving arrays and the methods of observation of a scattered signal outside of a main lobe of the diagram of scattering, i.e.…”

“…Joint use of two vertical arrays is considered in [8]. Recent work is summarized in [9]. Results reported in [6][7][8] are from a series of lake experiments conducted in 1997-1999.…”

Forward acoustic scattering by moving objects: Theory and experiment

“…Forward scattering from an intrusive object could cause aberration in the waveguide response, providing an advantage in quietobject detection [5][6][7][8]. Transient aberration results from interference between the incident and scattered fields from an object [9], and its features can be actually difficult to be predicted in a multipath environment.…”

“…Over the past few years, a detection method using forward scattering techniques was proposed for moving underwater targets, and a successful lake experiment was conducted with a foam plastic target [5,6]. A detection and localization algorithm based on the same techniques was described and evaluated based upon the experiment in a harbor environment [7].…”