| 摘要 |
PURPOSE:To eliminate the synchronous noise caused at other apparatus due to the reception signal by giving a comparison between the noise signal obtained only through reception and the reception signal obtained by radiating the sound wave and then detecting the synchronous noise which is common to both signals. CONSTITUTION:Synchronous signal generator 1 generates synchronous pulses t1 and t2 to display unit 17. No ultrasonic wave is radiated from wave transmitter/ receiver 5 at pulse t1, and the signals received at transmitter/receiver 5 feature the synchronous and nonsynchronous noise signals. These noise signals undergo the amplification and detection through reception circuit 6 to be memorized in memory circuit 12. Then pulse t2 received at transmission circuit 4 from generator is sent to transmitter/receiver 5, and transmitter/receiver 5 converts the high frequency signal into the ultrasonic wave to radiate it into the sea. And the reflected signal is sent to the comparator to be read out via the pulse supplied from clock pulse generator 13, and then compared with the memorized waveform in comparator 14. Thus the common synchronous noise is detected. In this way, the synchronous noise can be eliminated. |
