| 摘要 |
PURPOSE:To prevent the error from being generated in the movement speed of a school of fish even when a ship is turned, by converting the frequency of reflected waves from the radiation direction of ultrasonic waves from the coordinate system of he beam radiation direction to the coordinate system with due north as the reference and calculating the movement speed of the school of fish on a basis of the speed of the ship relative to the sea bottom and the speed of the ship relative to the school of fish and performing the averaging processing. CONSTITUTION:Pulses generated in a transmitter 1 are supplied to an ultrasonic transmitter and receiver 3 through a transmission/reception switching circuit 2. The transmitter and receiver 3 radiates ultrasonic pulses into water downward obliquely and receives reflected waves and converts them to an electric signal, and this electric signal is supplied to a receiver 4. The received signal is amplified and frequency-divided in a frequency divider 5. This divided signal turns on an AND gate 7 only in the time of the high level, and the oscillation frequency of an oscillator 6 is counted in a counter 8 and is supplied to a calculator 9 and is converted to a ship speed. The detected Doppler frequency is a measured value without the averaging processing. Coordinate conversion is performed on a basis of this measured value, and the movement speed of a school of fish is calculated and is subjected to the averaging processing. |
