Active Signal Processing Enhancements for Classification of Low Signal-to-Noise Ratio (SNR) Sonar Signals in Doppler Clutter Navy SBIR FY2015.1 Sol No.: Navy SBIR FY2015.1 Topic No.: N151-034 Topic Title: Active Signal Processing Enhancements for Classification of Low Signal-to-Noise Ratio (SNR) Sonar Signals in Doppler Clutter Proposal No.: N151-034-0040 Firm: Adaptive Methods, Inc 5860 Trinity Parkway Suite 200 Centreville, Virginia 20120 Contact: Travis Cuprak Phone: (703) 968-8040 Abstract: The acoustic environment encountered in pulsed active sonar provides some of the most formidable challenges seen in modern signal processing. The confluence of strong bottom clutter, ownship Doppler spreading, and discrete mutual interference results in clutter leakage and sidelobes across beam and Doppler spaces. Platform motion causes clutter returns to be shifted in Doppler, leading to elevated noise "shoulder" near the zero Doppler ridge, impacting the detection and classification of low Doppler contacts. Current adaptive signal processing algorithms suffer from sample support limitations due to the rapidly changing active environment. In order to prevent signal suppression and maintain robust performance, these algorithms must be run conservatively, limiting their ability to null clutter and interference. In this proposal, Adaptive Methods outlines a new and innovative approach to active sonar signal processing. We build upon our experience in rapid adaptation to provide the next generation of active signal processing. Our approach, termed the Robust Active Signal Processing Adaptive Processor (RASAP) enables aggressive robust adaptation in sample starved environments. This approach mitigates the corruptive effects of interference and leakage while minimizing impact on downstream processing, leading to improved detection, tracking, and classification performance. Benefits: The combination of the proposed technologies will enable adaptive processing to be performed without being forced to run conservatively. More aggressive settings, enabled through the innovative HASS concept in conjunction with the other technologies, will mitigate the corruptive effects of interference and leakage on the signal processing surface. Robustness enhancements will minimize impact on downstream processing. Existing classification features will provide better target-clutter separation due to reduced leakage effects; false alert rates will be reduced due to mitigated clutter; and the operator and tracker will be presented with a cleaner surface for detection and tracking. The combined effect will be a significantly improved signal processing surface that enables better contact-clutter separation in downstream processing. Furthermore, the stated goals align with Navy requirements 40(1)A(1) (Active Clutter Reduction and Active Automation Improvements); 82(2)5.a.(2) (Mitigate acoustic interference of loud profile/point noise sources); 41(a)A(1)(a) (Improve Probability of correct classification and false alarm rate). The primary market for our proposed technology is the US Navy. The Navy will benefit from this technology through improved contact detection, localization, and classification as well as other related technology that we develop in the execution of this work. The proposed technology can be applied to a variety of arrays and active/passive systems. US Navy systems employing signal-processing technology include submarine systems for the Sphere, Chin, and LAB array, TB-29, TB-36, TB-16 arrays, SURTASS TwinLine, and tactical surface ship sonar systems for Cruisers and Destroyers (CRUDES) and Littoral Combat Ship (LCS) such as the AN/SQQ89 Multi-Function Towed Array (MFTA) and towed acoustic intercept array (ACI). Minehunting sonars typically have a high number of false alarms due to clutter and could benefit from the RASAP concept of aggressive adaptation and tunable mainlobe with. The secondary market consists of a variety of platforms and systems currently in use by the Commercial sector as well as University and Navy Lab R&D arrays. Commercially available side scan sonar systems used in mapping the ocean bottom and aiding in search/recovery missions must isolate active clutter, sometimes in the presence of heavy interference. Systems designed for use in ocean oil and gas exploration typically employ active sonar transmitters and receivers while in motion, leading to spread clutter. The technologies provided by RASAP can be applied to these systems to provide robust performance and crisp features for analysis. The ability to aggressively reject interfering energy in difficult environments will be sought after to improve performance. Return