| 摘要 |
PURPOSE:To prevent an erroneous detection caused by noises by setting a threshold for identifying level in a decision circuit in a proper value and making the decision circuit not transmit a pulse at the time of receiving a random signal such as a noise, etc. CONSTITUTION:A low pass filter (LPF) 5, which is a filter for obtaining a DC component, outputs an output signal to the decision circuit 6, which generates the pulse so as to transmit to a discrimination circuit 9 only when the output signal from the LPF 5 exceeds the previously prescribed threshold. Meanwhile, an absolute value circuit 7 counts the absolute value of the transmission signal of the LPF 1 and transmits it to the decision circuit 8, which generates the pulse to transmit the discrimination circuit 9 only when the absolute value given from the absolute value circuit 7 exceeds the previously prescribed threshold. The discrimination circuit 9 generates and transmits the signals (a-c) of the pulse which shows the arrival of a repeat signal according to the existence of pulses which arrive from the decision circuit 6 and 8. Thus, since in a signal detection circuit the auto-correlation of the signal is small and DC component is substantially zero at the time of receiving the noises, the influence by the noise can be removed by the thresholds set in the decision circuits 6 and 8. |
