ACOUSTIC IMAGING IN TURBULENT MEDIA WITH THE SPATIAL BISPECTRUM

A new array processing system that performs high-resolution imaging in turbulent ocean media is introduced. It exploits information containe d in higher-order spatial spectra and images to a resolution which is limited by the array aperture rather than the medium. Precise a priori knowledge of the turbulence's spatial coherence structure is not need ed. Furthermore, the signal processing is straightforward to implement , the system is self-calibrating, and the computational demands are re asonable. Initial tests of the imager have been conducted and several representative examples are presented. It is found that precise bispec trum estimates are required for good image quality. Since this require s large data sets, in essence this algorithm trades data requirements for resolution. In addition; the direction of arrival information, con tained in phase terms that are processed with the bispectrum is lost i n the averaging process. Nevertheless, the system provides very good q uality images, even in severe environments. (C) 1995 Acoustical Societ y of America.