Yung P. Lee Charles W. Spofford
Sci. Appl. Intl. Corp., 1710 Goodridge Dr., MS T1-3-5, McLean, VA 22102
A shallow water experiment was conducted to examine the directionality and spectral spread of cw signals after multiple interactions with the sea surface. Bottomed sources with frequencies between 200 and 300 Hz and two bottomed arrays with apertures up to 250 m were employed allowing source--receiver distances of 6--15 km under a variety of sea conditions and angles of paths with respect to the seas. High-resolution adaptive beamforming techniques were used to suppress grating lobes and compensate for array distortions from linear. Directional beam spectra of the signals were observed illustrating dependences on wind speed and direction with respect to the signal path. The results are interpreted in terms of Bragg scatter from the surface wave.