High Resolution Beamforming on Large Aperture Vertical Line Arrays: Processing Synthetic Data.

摘要

This technical memorandum studies the beamforming of large aperture line arrays deployed vertically in the water column. The work concentrates on the use of high resolution techniques. Two processing strategies are envisioned: full aperture coherent processing which offers in theory the best processing gain, and subaperture processing which consists in extracting subapertures from the array and recombining the angular spectra estimated from these subarrays. The conventional beamformer, the Minimum Variance Distortionless Response (MVDR) processor, the MUltiple Signal Classification (MUSIC) algorithm and the Minimum Norm method are used in this study. To validate the various processing techniques, the ATLAS normal mode program is used to generate synthetic data which constitute a realistic signals environment. A deep-water, range-independent sound velocity profile environment, characteristic of the North-East Pacific, is being studied for two different 128 sensor arrays, a very long one cut for 30 Hz and operating at 20 Hz, and a shorter one cut for 107 Hz and operating at 100 Hz. The simulated sound source is 5 m deep. The full aperture and subaperture processing are being implemented with curved and plane wavefront replica vectors. The beamforming results are examined and compared to the ray-theory results produced by the Generic Sonar Model.