Signal subspace beamforming in the presence of coherent interferences and unknown correlated noise fields

Abstract

In a realistic passive sonar scenario, the desired signal will be received in the presence of coherent interferences and spatially correlated noise fields. In this paper beamforming algorithms are developed for this scenario. Two types of signal subspace beamformers based on different optimality criteria, are developed. They are (i) optimum-interference notch beamformer, and (ii) optimum-interference plus noise rejector. The beamformers are first developed for the narrowband data model and then extended to the wideband case. Projection matrices onto the signal subspace are computed by using Q-R decomposition instead of the computationally intensive eigen-decomposition. Expressions for the output-signal to interference-plus-noise ratio are derived and used as a measure to evaluate the performance of the beamformers. Simulation results are also given to support the theory.