| 摘要 |
PURPOSE:To enable the bottom quality discrimination of the sea bottom, by a method wherein an amplifier is saturated with respect to the rise part of a received pulse due to reflected ultrasonic waves from the sea bottom and the gain of the amplifier is sharply reduced directly after saturation. CONSTITUTION:A counter 8 is set to a predetermined initial value by a pulse corresponding to the ultrasonic transmission trigger from a transmission triger generating circuit 1 due to a pulse generating circuit 9 and the gain of an amplifier 3 is still held to a predetermined value through a D/A converter 4. In this state, the amplifier 3 is saturated by reflected received ultrasonic waves higher in a level as compared to that to a school of fish or the like and the sea bottom is detected while the saturation output from the amplifier 3 corresponding to the rising of the received waves opens an AND gate 7 through a slice circuit 5. By this method, the pulse from a pulse generating circuit 6 is subtracted by the counter 8 while the gain of the amplifier 3 is reduced and the bottom quality of the sea bottom is discriminated by the non-saturation output from the amplifier 3. |
