| 摘要 |
PROBLEM TO BE SOLVED: To allow the filter circuit that uses at least one signal filter with one filter frequency that can adjusts at least an audio carrier in a composite video signal depending on a control signal to filter a signal to adjust in an optimum state the signal filtering frequency independently of external effect, tolerance of manufacturing and temperature fluctuation or the like. SOLUTION: The filter circuit 1 has a reference filter 11 that has a filter frequency (f) adjustable depending on a control signal and shifts the signal frequency (f) by a prescribed value at the moment when the signal frequency is tuned, a phase comparator 14 that receives an output signal and a reference signal, the filter 11 uses an output signal of the control signal comparator 14 to be tuned to a frequency of a reference signal and a PLL 3 is used to demodulate a modulated audio signal on an audio carrier. |
