| 摘要 |
PURPOSE:To achieve the prevention of misdetection along with a easier detection, by performing a detection of a target signal from received sound waves coming through water depending upon a modulation pattern of a transmitting signal. CONSTITUTION:A received signal (a) is inputted into a delay circuit 11 and a frequency measuring circuit 13 and the circuit 11 sends out a delay signal a' to a gate circuit 12. On the other hand, the circuit 13 measures the cycle of all vibration components of the signal (a) and sends a measured value (b) to a frequency correction circuit 14, which subtracts a difference value between the cycle of the transmitted signal stored and an average cycle from the measured value (b) to calculate a frequency correction value c and a frequency dispersion calculating circuit 15 determines a frequency dispersion value (d). A comparator circuit 16 compares the dispersion value (d) with a specified threshold inputted from a terminal 2 and send a time range output level to the circuit 12 as gate signal when it is below the threshold. The circuit 12 extracts a target signal (e) from the gate signal and the signal a' to be outputted to a terminal 3. This facilitates the detection of a target signal thereby preventing misdetection.
|
