GABOR/WIGNER-VILLE PROCESSING FOR CROSSTERM SUPPRESSION, RESOLUTION ENHANCEMENT AND NOISE REDUCTION IN UNDERWATER...

THE WIGNER-VILLE (WV) DISTRIBUTION FINDS FAVOR IN PROCESSING FOR ACOUSTIC TRANSIENT SIGNATURE IDENTIFICATION BECAUSE OF ITS ABILITY TO PORTRAY TIME HISTORY OF THE FREQUENCY DISTRIBUTION OF SIGNAL ENERGY. A KEY ISSUE OF CURRENT RESEARCH ON THE WV DISTRIBUTION IS THE SUPPRESSION OF QUADRATICALLY-INDUCED CROSSTERMS IN THE REPRESENTATION OF SUPERPOSED SIGNALS. WE PROPOSE TO RESEARCH METHODS FOR CROSSTERM SUPPRESSION, RESOLUTION ENHANCEMENT AND NOISE REDUCTION BASED ON INTRODUCTION OF A SIGNAL'S GABOR EXPANSION INTO THE WV DISTRIBUTION. CROSSTERM CONTROL IS EXERCISED BY SIMULTANEOUS MINIMIZATION OF THE NUMBER OF SIGNIFICANT TERMS IN THE EXPANSION AND ELIMINATION OF THE GABOR BASIS CROSSTERMS IN A "CROSSTERM-DELETED" REPRESENTATION. APPROPRIATE CHOICE OF A GABOR WINDOW FUNCTION--ONE WELL MATCHED TO THE DATA CHARACTERISTICS--IN THIS REPRESENTATION WILL BOTH REDUCE THE NUMBER OF CROSSTERMS AND DECREASE OVERLAP (INCREASE RESOLUTION) AMONG THE AUTOTERMS. NONLINEAR PREPROCESSING OF THE GABOR COEFFICIENTS UNDER MATCHED WINDOW CONDITIONS CAN SUBSTANTIALLY ATTENUATE NOISE PRIOR TO COMPUTATION OF THE WV DISTRIBUTION. THE PROPOSED PROGRAM WILL YIELD A TESTBED OF NOVEL METHODS UPON WHICH ADVANCED RESEARCH IN SIGNATURE IDENTIFICATION CAN BE BASED. THE PROPOSED PROJECT HAS POTENTIAL APPLICATION TO CURRENTLY ACTIVE AREAS OF GOVERNMENT RESEARCH, E.G., DEVELOPING AN AUTOMATED SIGNAL PROCESSING FACILITY TO AID IN CLASSIFICATION OF ACOUSTIC EVENTS AT SEA. THE SIGNAL REPRESENTATIONS MADE AVAILABLE BY THE PROPOSED EFFORT WOULD PROVIDE ADDITIONAL TOOLS THAT COULD BE IMPLEMENTED IN FIRMWARE/ HARDWARE AND TRANSFERRED TO A FACILITY SUCH AS THAT SUPPORTED BY DARPA AT ORINCON CORP.