| 摘要 |
PURPOSE:To make it possible to treat noises which have been mixed in the front and rear parts of a received signal and to prevent any erroneous action particularly when noises of a large peak value are supplied by constituting the subject circuit from a level comparator, a pulse width enlarging circuit, a reference pulse generating circuit and a pulse width comparison circuit. CONSTITUTION:An ultrasonic pulse received by a wave receiver 1 is amplified 2 to a desired level, and the output thereof is supplied to one input terminal of a level comparator 3. A reference voltage is applied from a reference voltage source 4 to the other input terminal. From the comparator 3 there are produced positive pulses with a period equivalent to the repetitive period of the received signal at every time the received signal exceeds the reference voltage, and further with the peaks arranged. Furthermore, positive pulses of the comparator 3 is supplied to a pulse width expanding circuit 5, and further supplied to a reference pulse generating circuit 5, and further supplied to a reference pulse generating circuit 6 and a pulse width comparison circuit 7. In this manner, the received signal is detected in the repetitive pulses of several period parts, whereas the noise is detected almost in a single pulse, and therefore both can be discriminated from the difference. |
