Furuno Electric Company Limited

Yasuo Ito

Yasushi Nishimori

Akira Okunishi

Shinji Ishihara

Itsuo Fukuoka

Hiroshi Iino

Tatsuo Hayashi

Nobuharu Yamashina

While keeping a propeller located in a negative direction of a y-axis turning, transmission of acoustic waves from vibrating elements of a transducer unit is interrupted. Reference signals 'A' and 'B' which are receiving beam signals having principal acoustic axes oriented in a propeller direction are generated from received signals obtained by &#x201c;A&#x201d; and &#x201c;B&#x201d; group vibrating elements, respectively. Next, adjustment factors used for removing propeller noise from received signals obtained by vibrating elements on positive and negative sides of an x-axis are calculated by performing arithmetic operation on time-series data on the received signals obtained by the positive and negative sides vibrating elements and on time-series data on the reference signals &#x201c;A&#x201d; and &#x201c;B&#x201d;, respectively. When performing underwater sounding operation by transmitting acoustic waves, a product of the reference signal &#x201c;A&#x201d; or &#x201c;B&#x201d; and the adjustment factor is subtracted from the received signal obtained by each of the positive and negative sides vibrating elements, respectively.

Underwater sounding apparatus

An automatically tracking scanning sonar alternately performs horizontal scanning and vertical scanning and a target lock processor calculates a predicted position of a target based on an echo signal previously received from the target when the echo signal from the target is interrupted. A selector sets a range, tilt angle and sounding direction and outputs them to a transmit-receive controller such that the scanning sonar can scan the predicted target position. As the depth of the target is determined by performing the vertical scanning, the tilt angle of an umbrellalike beam pattern produced by the horizontal scanning can be varied to follow the target by controlling the tilt angle based on target depth information even when the target moves in vertical directions. It is therefore possible to automatically track the target in a reliable fashion.

Automatically tracking scanning sonar

A transducer is constructed of a plurality of transducer elements which are arranged in multiple layers and columns forming as a whole a generally cylindrical shape. A scanning sonar employing the transducer thus constructed can be switched between horizontal scan mode in which a vertically focused beam having a narrow horizontal beam angle (high horizontal directivity) is steered around the transducer using all the transducer elements and vertical scan mode in which a horizontally focused beam having a narrow vertical beam angle (high vertical directivity) is steered in a vertical plane directed in a specified scan azimuth to find out the angle of incidence of a received signal. The horizontally focused beam is formed by using the transducer elements of specific columns centered on the specified scan azimuth. A vertical scan signal obtained in the vertical scan mode is multiplied by a chirp signal. A correlator provided in a succeeding stage converts the amount of Doppler shift into time data and determines the angle of incidence of the received signal.

Device for and a method of determining the angle of incidence of a received signal and a scanning sonar

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Nishinomiya, Japan

Yasuo Ito