| 摘要 |
<P>PROBLEM TO BE SOLVED: To enhance noise tolerance of a receiving device in a center for a CATV transmission system. <P>SOLUTION: A noise level of an up-band at an input side of a gate switch device 16 is detected by a bandpass filter 26 and an integration circuit 28, and a receiving level of a data signal carrier wave is detected by a bandpass filter 32 and an integration circuit 34. A level generator 30 outputs a predefined level which increases with height of the noise level detected, and a comparator 36 compares the receiving level of the carrier wave with the predefined level. The gate switch device is in a signal-pass status when the receiving level of the carrier wave is higher than the predefined level, and the gate switch device is in a signal-cutoff status when the receiving level of the carrier wave is lower than the predefined level. When the noise is reduced, a margin of the pass status for the gate switch device is larger. When the noise is increased, a probability of the incorrect demodulation of the noise is smaller. <P>COPYRIGHT: (C)2004,JPO |
