| 摘要 |
<p>An underwater detector which quickly detects frequency components contained in echos from all the directions, displays the frequency components, and thus can improve the capability of target identification. Two ultrasonic beams received at a predetermined phase difference angle are rotated and a phase difference between the two ultrasonic signals is detected. The carrier frequency contained in echos from the target is detected from the phase difference, and the speed and the direction of the target are determined from the detected carrier frequency and displayed for each color. The speed of the target is corrected by the speed of a ship, etc, so as to determine the speed of the target itself with respect to the ground.</p> |
