Physics-Based Improvements for Continuous Active Sonar (CAS)

Signal Systems Corporation proposes to develop and evaluate a novel motion-adaptive matched filter, tuning standard replicas to account for time-varying delays observed in received continuous active sonar (CAS) echoes. The method directly incorporates detailed physics models of the time-varying delays of linear frequency modulation (LFM) sweeps into the estimation algorithms, accounting for unknown or unmeasured motions of the surface ship hull sonar, towed array, and target. Arbitrarily long replicas are then constructed by distorting the transmitted LFM waveform to follow the estimated delays, thereby reducing signal mismatch loss by sharpening and increasing the SNR of target echoes after coherent (matched filter or heterodyne) processing. A successful Phase II effort will lead to a software only upgrade to the AN/SQQ-89A(V)15 surface ship sonar system that improves CAS anti-submarine warfare missions by mitigating signal mismatch loss, decreasing range uncertainty, reducing false alarm rates, and improving target tracking performance.