Accession Number : ADA194288

Title :   Identification of Sources with Unknown Wavefronts.

Descriptive Note : Final rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s) : Mermoz, Henri

PDF Url : ADA194288

Report Date : 31 Mar 1988

Pagination or Media Count : 95

Abstract : This paper concerns techniques for processing sonar array data to obtain information about the spatial distribution of acoustic sources. It presents a method for determining the spectral density and the signal wavefronts of several sources using a minimum of prior assumptions. The passive sonar problem is defined and the traditional approach to a solution using matched filters is presented. Maximization of the directivity factor for known signals with static, nonadaptive filters emerges as the prime goal of traditional processing. Care is then taken to properly introduce the cross spectral density matrix which plays a crucial role in adaptive processing. A realization of adaptive noise cancellation through the use of signal-free references is achieved with the development of a Correlo-Filtre. Adaptive noise cancellation leads to degradation when a supposedly known wavefront deviates from an expected shape. Robustness and the need for a processor which does not require prior knowledge of the wavefront is then discussed. Method of identifying completely unknown wavefronts is proposed. Using the eigenvalues of the cross spectral density matrix allows the number of sources to be determined. The wavefront shapes are then shown be scrambled within the eigenvectors by an unknown unitary matrix. Additional information needed to select a specific unitary matrix is introduced by modeling the sources as a coherent sum of conditional plane waves.

Descriptors :   *SOUND GENERATORS, *SONAR SOUND ANALYZERS, *IDENTIFICATION SYSTEMS, ADAPTIVE SYSTEMS, CANCELLATION, DEGRADATION, EIGENVALUES, EIGENVECTORS, IDENTIFICATION, MATCHED FILTERS, NOISE, PASSIVE SONAR, PLANE WAVES, PROCESSING, SHAPE, SIGNALS, SONAR ARRAYS, SOURCES, SPATIAL DISTRIBUTION, SPECTRAL ENERGY DISTRIBUTION, WAVEFRONTS

Subject Categories : Acoustic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE