Automatic color burst magnitude control for a digital television receiver

摘要

An automatic color burst magnitude control (ACC) for a digital television receiver is compatible with and is unaffected by variation of the phase of the color subcarrier signal introduced in demodulating the color subcarrier to effect control of tint. ACC is effectuated by digital gain control for scaling the digital words representing the sampled magnitudes of the color subcarrier burst signal. Quadrature demodulation of the color subcarrier signal produces color signal digital words I and Q which are each sampled and latched during the color subcarrier burst. The averages of the sampled I and Q digital words are applied as respective portions of the address of a read only memory (ROM). The ROM provides error words indicating whether the chroma burst amplitude is too large or too small. A control device responds to the error word to scale the color subcarrier digital words, and therefore scale the chroma burst amplitude to a predetermined magnitude.