| 摘要 |
PROBLEM TO BE SOLVED: To enhance the S/N by preventing deterioration in the C/N in an input section so as to reduce a bit error rate or to enhance the quality of an audio signal in the case of using a video channel in a cable television CATV so as to receive the audio signal. SOLUTION: A video signal applied to an input terminal Vin is amplified by a 1st low noise amplifier 31 with a small noise figure, an automatic gain control circuit 32 adjusts the level of the amplified signal, and a band pass filter 33 eliminates a noise at the outside of a signal band. Then the signal is amplified by a 2nd low noise amplifier 34 with a small noise figure, converted into an intermediate frequency by a frequency mixer circuit 35, which outputs an intermediate frequency IF with a high C/N.
|
