| 摘要 |
PURPOSE:To attain a stable chrominance synchronizing circuit quick in response by providing a means to generate the second signal for conversion that has the same phase variation as that of a reproducing chrominance signal. CONSTITUTION:A burst phase comparator 17 extracts a burst signal from a reproducing chrominance signal output, and compares the phase of it with that of the output signal from a 3.58MHz reference oscillator 22. The output of this phase-comparison is supplied as a control input to a 3.58MHz VCO 19 through an LPF 18. Thus, from the VCO 19, a 3.58MHz signal whose phase variation is the same as that of the reproducing chrominance signal is outputted. This output is frequency-converted by a frequency converter 20 using the signal from the oscillator 22 in order to obtain a signal whose frequency is 2fsc which is two times of the 3.58MHz. In the last stage, the said signal of frequency 2fsc is taken out by a BPF 21, to be the second signal for conversion.
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