A new method for passive synthetic aperture array processing

Abstract

A technique for extending the useful aperture of a towed array is presented. Its advantage over previous techniques is that it uses the existing aperture of the physical array to estimate the phase correction factor for the successive measurement. Thus the need for an accurate knowledge of the source frequency is avoided. By using the fact that, at any time, the array overlaps its position at a previous time, a maximum likelihood estimator can be constructed that computes the phase difference between the measurements taken at these two positions. This estimated phase difference is then used to correct the second measurement. An iterative procedure is then used to extend this technique over several measurements. This estimation procedure, along with estimating the kinematic phase correction factor ωτ includes any other phase errors that may be incurred by such effects as array motion, propagation effects, or loss of temporal coherence. Results with both real and synthetic data arc shown that demonstrate th...