Abstract: An underwater sonar measuring method using synthetic aperture technique which radiates an ultrasonic signal to targets by a transmission transducer unit (1B), receives echo signals reflected by the targets by moving reception transducer units (1A, 1B, 1C) at a plurality of points, adjusts a plurality of signals received in phase and combines the resultant phase-shifted signals. The reception transducer units are moved over a distance less than the length "L" of the transmission transducer unit during a period for an ultrasonic signal going to and returning from a target. The signals received and phase-combined during this period are multiplyed by the radiated signals so that there are eliminated grating lobes appearing on both sides of the main lobe when an aperture synthesis is performed, and thus a high resolution measurement is made.

Abstract: The present invention relates to a beam forming device for forming a uniform radiation beam and/or a reception beam. In radiation, the transducer is vibrated in such a way that the pressure of a sound wave produced from each point of the vibrating surface of the transducer is determined based on a weight function, thereby forming a radiation beam. In reception, electric signals are derived based on the sound energy received in a manner that the amplitude level of an electric signal produced based on the sound energy received by each point of the vibrating surface of the transducer is determined based on a weight function, and the derived signals are combined with one another to form a reception beam.

Abstract: The present invention is directed to a detection system which forms reception beams successively in a series of angular directions. The detection system comprises receiving means for receiving incoming signals in such a manner that the frequency of the incoming signals is varied in accordance with the Doppler effect, and a matched filter for pulse-compressing output signals from said receiving means, with output signals from said matched filter being displayed in an indicator.