Patent ID: 6567129
Filing Date: 2003-05-20
Classification: H04N

Abstract:
A color demodulation apparatus color-demodulating a chrominance subcarrier signal separated from a composite television video signal through digital processing, comprising:frequency divider means for generating a predetermined load clock (hereinafter referred to as RCLK) using a system clock (hereinafter referred to as SCLK) which is an operational reference for the apparatus; band-pass filter means, supplied with said chrominance subcarrier signal, for eliminating signal components of an unnecessary frequency band from the chrominance subcarrier signal; first multiplier means, supplied with said chrominance subcarrier signal from said band-pass filter means, for controlling the chrominance subcarrier signal to be outputted therefrom to keep constant amplitude according to gain controlled by comparator means; second multiplier means, supplied with said chrominance subcarrier signal after amplitude control outputted from said first multiplier means and a phase alternate SIN wave signal outputted from SIN data generator means, for multiplying the signals together for multiplex demodulation of an R-Y signal and a B-Y signal; first low-pass filter means, supplied with a multiplex-demodulated signal from said second multiplier means, for passing frequency bands of the R-Y signal and the B-Y signal and eliminating predetermined high frequency band components; first load hold means, supplied with said multiplex-demodulated signal with the high frequency band components eliminated outputted from said first low-pass filter means, for separating the multiplex-demodulated signal into the R-Y signal and the B-Y signal and outputting the R-Y and B-Y signals according to said RCLK; accumulator means, supplied with said multiplex-demodulated signal with the high frequency band components eliminated outputted from said first low-pass filter means, for accumulating burst signal in the R-Y signal and burst signal in the B-Y signal based on a burst gate pulse (hereinafter referred to as BGP) which provides a burst signal period and outputting each of the accumulated burst signal only once during each horizontal period; second low-pass filter means, supplied with each burst signal outputted from said accumulator means, for passing the frequency bands of the R-Y signal and the B-Y signal and eliminating predetermined high frequency band components; second load hold means, supplied with each of said burst signal with the high frequency band components eliminated outputted from said second low-pass filter means, for separating the burst signal into burst signal in the R-Y signal and burst signal in the B-Y signal and outputting each of the burst signal according to said RCLK; VCO means, supplied with the burst signal in the R-Y signal outputted from said second load hold means, for varying and outputting a period of a ramp wave according to a level of the burst signal in the R-Y signal; switching means, supplied with data corresponding to an R-Y demodulation axis and data corresponding to a B-Y demodulation axis in the ramp wave outputted from said VCO means, for alternately switching between the data for output according to said RCLK; adder means for adding data outputted from said switching means to data on the ramp wave outputted from said VCO means and outputting a ramp wave; said SIN data generator means for generating and outputting said phase alternate SIN wave signal in synchronization with the ramp wave outputted from said adder means; and said comparator means, supplied with the burst signal in the B-Y signal outputted from said second load hold means, for comparing a value of the burst signal with a predetermined reference value and controlling the gain of said first multiplier means so that the value of the burst signal matches the reference value.