Scanned Line-Hydrophone Method of Angle Determination, Miss-Distance Indicator.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK ORDNANCE RESEARCH LAB
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The Miss-Distance Indicator project is an investigation into methods of tracking and plotting the trajectory of tame antisubmarine ordnance near a target submarine. A method for determining the angle of arrival of a sound wave is discussed in detail. A group of independent hydrophone elements, uniformly spaced along a straight line, is used to measure the angle of arrival. The motion of a single hydrophone moving relative to the sound waves is simulated by sampling the outputs of these elements in succession. It was found that the scanned linehydrophone system simulates, almost exactly, the single, moving hydrophone, and the frequency equation is found to hold. The frequencies of both pure-tone signals and narrow-band noise are shifted according to the above equation. Improvements in signal-to-noise ratio of over 14 db have been measured when the signal and the noise arrive from different directions. The angular resolution was found to be equal to the ratio of the wavelength of the sound to the component of the hydrophone length normal to the direction of sound propagation. This method appears to be quite satisfactory for angle determination and should be easily incorporated in a plotting system. Author