| 摘要 |
PURPOSE:To generate no howling even if target strength is large, by delaying a receiving signal by a pulse width corresponding portion of said signal, amplifying it to target strength, and transmitting it as a transmitting signal into the water from a transducer. CONSTITUTION:A receiving acoustic signal A of normal pulse width, which is transmitted is received by a receiver 15 and is converted to an electric signal C. The signal C is amplified by an amplifier 23, its noise is eliminated by a band pass filter 24, it is detected by a detector 25, and as for its output D, its level is detected by a pulse level detector 26. This detected level is extended by a pulse width corresponding portion by a pulse level delaying circuit 27 and is outputted. The signal D is inputted to a level comparing circuit 30 through a pulse width delaying circuit 28, pulse shaping circuit 29. An output of a gate circuit 33 is amplified in order to become desired target strength by a power amplifier 35 through a level variable device 34. |
