A new method of controlling the directivity of synthesized directive output in receiving system is described. This method, abbreviated as the TD (time difference) method, is different from the other usual methods in its principle. The information on the time difference between outputs of separated hydrophones was utilized to synthesize the directive output. The signals from hydrophones were transformed into pulse trains, maintaining the initial time difference, and then the controlled relative delay and pulse widths were given. After that, the coincidence of each pulse in pulse trains was discriminated in order to trigger the final output stage. The bearing and the width of receiving beam were controlled by relative delay and pulse widths respectively. Controlling characteristics and the limitation for speed of bearing-scanning were theoretically analysed, and experimentally confirmed. The effects of noise were also discussed. The receivine beam was electronically controlled and high-speed scanning was easily attained. The result of the reduced scale test on the experimental sonar with sector scanning by TD method is shown.
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