| 摘要 |
PROBLEM TO BE SOLVED: To eliminate an undesired audio band signal without the use of an externally mounted filter or an IC built-in filter with many degrees from a composite video signal caused through video IF amplification and video image detection. SOLUTION: An audio band signal elimination filter 5 for 4.5 MHz with a low attenuation factor Q almost eliminates an undesired audio band signal in a composite video signal of an output of a video IF amplification video image detection section 3. A nonlinear circuit 7 consisting of an HPE(high pass filter) 9, a limiter 11, an LPF 13 (low pass filter) 13, an amplifier section 15 and a sbutractor 17 completely eliminates the undesired audio band signal for 4.5 MHz in an output composite video signal of the audio band signal elimination filter 5.
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