| 摘要 |
PROBLEM TO BE SOLVED: To provide an offset beat canceller capable of being easily attached by omitting time and labor for manually switching band pass filters of a carrier reproducing part. SOLUTION: A video medium frequency signal including an interference wave obtained by applying a prescribed frequency offset to a transmission frequency with respect to a desired wave is inputted to a carrier reproducing part 77. A first filter 92 has a characteristic for allowing only a component corresponding to a frequency smaller for an offset frequency (10.01kHz) to pass through from a reference frequency (58.75MHz) of a video carrier, a second filter 93 has a characteristic for allowing a component corresponding to the reference frequency to pass through, and a third filter 94 has a characteristic for allowing a component corresponding to a frequency larger for an offset frequency to pass through from the reference frequency. A control part 50 detects output signal levels from the first to third filters 92 to 94 and controls the opening/closing of switches 104 to 106 so as to input an output signal including a video carrier of the desired wave to a PLL (phase locked loop) circuit 107 on the basis of the detection result. COPYRIGHT: (C)2005,JPO&NCIPI
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