Passive sonar limits upon nulling multiple moving ships with large aperture arrays

Large aperture sonar arrays have small resolution cells which (i) limit the number of "snapshots" available for accumulating sample covariance matrices and (ii) resolve the multipath propagation between each source and the array. Moving ships with high bearing rates transit resolution cells quickly setting limits upon short term stationarity assumptions. Usually, this leads to "snapshot deficient" processing which must be "patched" with techniques such as diagonal loading or subspace methods. Moreover, in most sonar environments there are several paths connecting a source to a receiver. The resulting interference pattern can be resolved with large aperture sonar arrays operated off "broadside". We examine the problems associated with large aperture sonar arrays here, particularly in the context of nulling multiple strong discretes from moving ships.