| 摘要 |
<p>PURPOSE:To exactly detect a signal, by receiving and amplifying an ultrasonic wave or a radio wave containing a pulse, extracting an AC component, generating a DC voltage corresponding to its mean value, and using it as a threshold level. CONSTITUTION:A signal which is received by a transmitting and receiving part 1 for transmitting and receiving an ultrasonic wave or a radio wave containing a detecting pulse is amplified by an amplifier 2, and an obtained signal (a) which is transmitted to an adder 3, and also is differentiated by a differentiating circuit 4, by which a signal (b) is obtained. The signal (b) is clamped by a DC regenerating circuit 5 of clamp ''0'' volt to obtain a signal (c), furthermore it is integrated by an integral network 6 having a large time constant, by which a DC signal (d) of level V1 volt is obtained. This signal (d) and the signal (a) are added by the adder 3 to make a signal (e), moreover it is sliced by a slicing circuit 7, and a signal (f) is obtained. In this way, a level of white noise only is extracted by utilizing a difference between white noise which occurs in the amplifying circuit 2 and a frequency component of a detecting signal, thus a pulse is detected exactly.</p> |
