CONTINUOUS TRANSMISSION SONAR

A STUDY IS PROPOSED WHICH WILL IDENTIFY THE SPECIAL PROBLEMS ASSOCIATED WITH CONSTRUCTING A LONG RANGE, LOW FREQUENCY CONTINUOUS TRANSMISSION SONAR. THE BENEFITS OF THIS CONTINUOUS OPERATION ARE REDUCED SOURCE LEVEL FOR A GIVEN DETECTION RANGE, AND NEARLY CONTINUOUS TRACKING INFORMATION ON THE TARGET. THREE PRINCIPAL PROBLEM AREAS ARE IDENTIFIED: OBTAINING SUFFICIENT TIME-FREQUENCY SPACE IN THE OCEAN MEDIUM TO BE ABLE TO UTILIZE TRANSMISSION WITH ADEQUATE TIME-BANDWIDTH PRODUCT, THE DYNAMIC RANGE PROBLEM ASSOCIATED WITH THE RECEIVER INPUT AND LATER PROCESSING, AND THE LARGE QUANTITY OF DATA TO BE BEAMFORMED, CORRELATED, AND DETECTED. BECAUSE OF PREVIOUS WORK, HYDROACOUSTICS HAS EXAMINED A CLASS OF SIGNALS BASED UPON FM OR FSK WHICH ARE SEMI-ORTHOGONAL AND ADDRESS THE FIRST PROBLEM, AND HYDROACOUSTICS HAS STUDIED DIGITAL DYNAMIC RANGE REQUIREMENTS IN SONAR PROCESSING WHICH YIELD OPTIMISTIC RESULTS IN ADDRESSING THE SECOND PROBLEM. THE FINAL PROBLEM IS ONE OF DEFINING THE HARDWARE/SOFTWARE NECESSARY, AND INITIAL ESTIMATES ALSO A FAVORABLE TOWARD THE FEASIBILITY OF THE SYSTEM.