| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem wherein color slippage and color unevenness are caused in a video image after demodulation, unless a phase difference between modulation carrier signals is kept constant. SOLUTION: The modulation carrier generator is provided with: a phase comparator for applying phase comparison to a reference signal and a signal from a 1/n frequency divider; a filter for filtering an output signal from the phase comparator into a DC signal; a voltage-controlled oscillator for receiving the DC signal to control its oscillated frequency; an n-multiple circuit for receiving an oscillated output signal and generating a signal with the frequency being a multiple of n of the frequency of the output signal; and a carrier generating circuit for using an output signal of the voltage-controlled oscillator for a reference input signal, using the reference clock to shift the phase, and generating divided carrier signals. The modulation carrier generator uses a PLL circuit that uses an output signal from the carrier generating circuit for a modulation carrier signal and a color burst of a color difference signal to produce a chroma signal, receives an output signal of the n-multiple circuit, and feeds back an output of the 1/n frequency divider circuit as a comparison signal of the phase comparator so as to generate each modulation carrier in a way of accurately making the phase difference between the modulation carriers at a constant interval. COPYRIGHT: (C)2005,JPO&NCIPI
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