Chroma demodulation apparatus for use with skew corrected clock signal
AssigneeRCA Corporation
InventorsRussell T. Fling, Eric D. Romesburg
Life of this patent
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Abstract
An apparatus is disclosed for generating a burst-locked, color subcarrier representative signal .phi..sub.sc from a skew-corrected clock signal MCS (which is reset once every horizontal line) and a skew error signal SES (indicative of the once-a-line phase adjustment of the skew-corrected clock signal). In accordance with another feature of the invention, a chroma demodulation apparatus is provided for generating a pair of color difference signals R-Y and B-Y in response to the internally-generated .phi..sub.sc signal.
Claims13
An apparatus for generating a color subcarrier representative signal .phi..sub.sc from a skew corrected clock signal MCS;
- said skew corrected clock signal having its phase adjusted periodically and having a constant frequency L.times.F.sub.sc (where L is a constant and F.sub.sc is the frequency of said color subcarrier signal) between successive phase adjustments;
- said apparatus being additionally responsive to a q-bit skew error signal SES indicative of said periodic phase adjustments;
- said apparatus comprising:
- a discrete time oscillator (DTO), having a capacity for p bits and responsive to said skew corrected clock signal MCS, for adding at each clock period an incremental value to the modulo (2.sup.p) previous sum;
- the p-bit output of said DTO being representative of said .phi..sub.sc signal;
- means for providing a fixed digital value (2.sup.p /L) representative of said color subcarrier frequency F.sub.sc ;
- means for providing (a) a normalized digital value (SES.times.(2.sup.p-q /L)) of said skew error signal SES once every phase adjustment period by multiplying said skew error signal by a normalizing factor (NF=2.sup.p-q /L), (b) and a zero value otherwise;
- and
- means for generating said incremental value by additively combining said color subcarrier frequency representative value with said normalized value of said skew error signal SES once every phase adjustment period.
In a digital TV receiver having an analog-to-digital (A/D) converter for converting an incoming composite video signal CVS into digital representations thereof in response to a skew corrected clock signal MCS;
- said composite video signal CVS including horizontal and vertical synchronizing components and a color subcarrier burst signal component;
- said skew corrected clock signal having its phase adjusted once every horizontal line, and having a constant frequency L.times.F.sub.sc (where L is a constant and F.sub.sc is the frequency of said burst signal) between successive phase adjustments;
- said TV receiver additionally including means for generating a skew error signal SES indicative of said once-a-line phase adjustments;
- said TV receiver further having a chroma demodulation apparatus comprising:
- means, responsive to said skew corrected clock signal MCS and said skew error signal SES, for internally generating a non-discontinuous, color subcarrier representative signal .phi..sub.sc locked in phase with said burst signal component of said composite video signal CVS;
- and
- means coupled for receiving said digital representations of said composite video signal CVS and responsive to said internally-generated color subcarrier representative signal .phi..sub.sc for generating at least one color difference component of said composite video signal.
Dependencies are inferred from the claim text.