| 摘要 |
PURPOSE:To detect a shoal of fish and a ship speed to water by the same sensor by giving respective vibrators tilt angles and discriminating the received signals of the vibrators. CONSTITUTION:Reflected signals of ultrasonic wave pulses of frequencies f1 and f2 sent by vibrators T1 and T2 are passed through trap circuits 6 and 7, 1st and 2nd mixing circuits 10 and 11, and 14 and 15, etc., and detected 13 and 17. Then the output signals of the circuits 13 and 17 are summed up 18 and led out as a fish shoal display signal. the difference between the frequencies f1 and f2 is about 2-5kHz, so BPFs 12 and 16 can identify signals from the vibrators T1 and T2. A Doppler component is generated sufficiently by the tilt angle of a sent beam. A gate 20 opens a gate for the generation period of a short-width pulse from a gate pulse generating circuit 19 to pass a reflected signal which contains the Doppler component from the water and inputs it to a differential amplifier 23 through frequency-voltage converting circuits 21 and 22. Then a difference voltage from an amplifier 23 is supplied to an arithmetic circuit 24 to calculate the ship speed to the water from the tilt angle and a Doppler shift quantity, etc.
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