Adaptive Beamforming for Littoral Waters

This project proposes preliminary investigations to prove the feasibility of four techniques for improving Adaptive Beamforming performance in littoral environments. Emphasis is placed on tradeoffs between algorithm efficiency and performance. The littoral acoustic environment is characterized by near and far field targets and dense dynamic near and far field directional interference at many ranges and levels of stationarity. Unique applications of Sub-Aperture Spatial Processing and Parabolic Near Field Wave Front Approximation techniques are proposed as efficient techniques to reduce target suppression caused by a mismatch between the Adaptive Beamforming constraints and the near field acoustic wave front and sensor array shape estimates. A third technique uses Synthetic (array data) Covariance Estimates made from conventional beam spatial spectra for adaptive beamforming weights computation to provide a fast low throughput weight updating technique in dynamic signal fields. The fourth technique provides an innovative approach for passive target range estimation by using Near Field Adaptive Beamforming Focused Range Zones. Theoretic performance calculations will be made based on spatial covariance data models that will incorporate wave front and array shape uncertainties and dynamic source geometries. When possible limited amounts of real data will be used. Signal processing gains and processing resource requirements will be tabulated with the most promising techniques selected for an extensive real data evaluation in Phase 2.