Accession Number : ADA294209

Title :   Applications of Sector-Focusing Processing for Stabilized Matched-Field Localization in Shallow Water.

Descriptive Note : Final rept.,

Corporate Author : NAVAL RESEARCH LAB STENNIS SPACE CENTER MS

Personal Author(s) : Feuillade, Christopher ; Chandler, Howard A. ; Smith, George B.

PDF Url : ADA294209

Report Date : 19 APR 1995

Pagination or Media Count : 25

Abstract : The sector-focusing (SF) method has been introduced as a technique for performing high resolution acoustic matched field processing in a waveguide. The SF methodology is highly effective against sensor phase error and geoacoustic mismatch in an environment dominated by modal noise. Sector focusing is a readily adaptable signal processing technique in that specific implementation strategies may be designed for application to individual environmental situations. In this report, the mathematical framework for SF is explored, and the mechanisms of mismatch induced instability described. The technique is then developed to demonstrate how the wide range of parameter options available for its implementation (i.e., variable sector size, shape, and dimensionality) provide flexibility to achieve stabilized localization performance for a broad range of conditions. Using the example of a continuous wave source in a noisy shallow water channel, the SACLANTCEN Normal Mode Acoustic Propagation (SNAP) model was used to generate replica acoustic pressure fields for the water channel with a depth variable sound speed profile. SNAP was also used to simulate a "detected" field due to an acoustic source in the presence of modal noise. These fields were then correlated using SF, which was applied via a "sliding" sector algorithm. The sector parameters were adjusted to optimize peak localization and to eliminate instabilities when mismatch was introduced. It was found that SF can always be made to achieve the stability of the Bartlett processor in the "small" sector limit. In the "large" sector limit, SF is seen to be equivalent to the reduced maximum likelihood processor.

Descriptors :   *SHALLOW WATER, *ACOUSTIC FIELDS, ALGORITHMS, SIGNAL PROCESSING, DETECTORS, SIZES(DIMENSIONS), PARAMETERS, MAXIMUM LIKELIHOOD ESTIMATION, CONTINUOUS WAVES, REDUCTION, ERRORS, SOUND TRANSMISSION, FOCUSING, RANGE(EXTREMES), SOUND PRESSURE, INSTABILITY, ACOUSTIC IMPEDANCE, NOISE(SOUND), IMPEDANCE MATCHING.

Subject Categories : Acoustics
      Physical and Dynamic Oceanography

Distribution Statement : APPROVED FOR PUBLIC RELEASE