| 摘要 |
PURPOSE:To make it possible to detect a defective period even when a remarkable disturbance signal is mixed into the defective period of an input carrier, by obtaining the sum output of signals detected by level detection circuits for positive and negative half-wave rectified waves. CONSTITUTION:An input signal with its amplitude limited by limiter 9 is inputted to half-wave rectifier 10, whose output is applied to LPF11 and level detection circuit 12, thereby detecting the amplitude variation of a positive half wave. Some of the output of limiter 9, after being inverted by inversional amplifier circit 13, is supplied via half-wave rectifier circuit 14 and LPF15 to level detector 16, where the amplitude variation of a negative half wave is detected. Then, detection signals obtained by circuits 12 and 16 are added logically by adder circuit 17. This output allows the perfect detection of the defective period of an input carrier even when a remarkable disturbance signal is mixed in the defective period. |
