Automatic phase control apparatus
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorHirofumi Nakagaki
Life of this patent
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Abstract
An automatic phase control apparatus for controlling the frequency of a sine wave produced from a variable frequency oscillator to be equal to that of the carrier wave of the extracted chrominance signal. A phase difference detector 4 detects a phase difference between the sine wave and the carrier wave. The detected phase difference is integrated to obtain an integrated value which is applied to the frequency oscillator for determining the oscillation frequency. A deviation detector is provided for detecting a deviation of the integrated value with respect to an expected frequency control data calculated by a calculator. When the deviation is greater than a predetermined range, the integrated value is replaced with the calculated data.
Claims8
An automatic phase control apparatus comprising:
- a horizontal sync separator for producing a horizontal sync signal separated from a reproduced luminance signal;
- an automatic phase control loop of which a closed loop transfer function takes a secondary loop form, and which comprises:
- (a) a variable frequency oscillator;
- and
- (b) a loop filter comprising an integrating means;
- calculation means for calculating an expected value that would be produced from said integrating means using a unit period determined by said horizontal sync signal, said expected value provided to said integrating means when a detected frequency synchronization state of said automatic phase control loop is out of a predetermined range;
- and
- detection means for detecting said detected frequency synchronization state of said automatic phase control loop.
An automatic phase control apparatus comprising:
- chrominance signal producer means for extracting a chrominance signal from a playback video signal and for producing a carrier signal further modulated by said chrominance signal to produce a modulated chrominance signal;
- variable frequency oscillator means for producing a wave signal having a frequency determined by an input frequency control data;
- calculation means for calculating an expected frequency control data;
- frequency converter means, coupled to said chrominance signal producer means and said variable frequency oscillator means, for demodulating the modulated chrominance signal to remove the carrier signal using said wave signal;
- phase difference detection means, coupled to said frequency converter means, for detecting a phase difference between said wave signal and said carrier signal;
- deviation detection means, coupled to said calculation means and said variable frequency oscillator means, for detecting a deviation of said frequency control data with respect to said expected frequency control data and producing a deviation detection signal;
- frequency control data generating means, coupled to said deviation detection means and said calculation means, for generating said frequency control data in accordance with said deviation detection signal when said deviation is less than a predetermined amount, and in accordance with said expected frequency control data when said deviation is greater than said predetermined amount.
Dependencies are inferred from the claim text.