Underwater Direction of Arrival Estimation using Wideband Arrays of Opportunity

We present a scheme to estimate the direction of arrival of acoustic signals reflected by underwater targets using wideband hydrophone arrays of opportunity. Such arrays may be obtained by arranging together multiple smaller sub-arrays that were originally designed to work independently. The array of opportunity that results may be subject to practical mounting limitations, hence the typical constraint that closest array elements should not be spaced more than one half-wavelength may not be upheld. In these conditions, the array is affected by spatial ambiguity. Our proposed scheme solves this issue by fusing direction-of-arrival information with side information on the estimated target location (obtained via multilateration). This makes it possible to eliminate most of the ambiguity, and yields accurate direction-of-arrival estimates. Our simulation results show that our scheme achieves satisfactory direction of arrival estimation and localization results. Moreover, even by relying on arrays of opportunity, we can outperform classical direction-of-arrival algorithms applied to larger arrays with half-wavelength spacing design.