Digital phase error detector for locking to color subcarrier of video signals

A digital phase error detector for locking to a color subcarrier signal in an analog video signal, said digital phase error detector comprising:

• a digitizer, said digitizer being responsive to a sample clock signal and operable to digitize said color subcarrier signal to generate a first digital data stream from said analog video signal;
• a bandpass filter, said bandpass filter operable to generate a second digital data stream by filtering said first digital data stream to substantially eliminate DC offset of said color subcarrier signal digitized by said digitizer;
• a mixer, said mixer operable to generate a third digital data stream from said second digital data stream representing sum and difference frequencies of a product of said color subcarrier signal and a reference clock signal;
• an accumulator, said accumulator operable to accumulate said product of said third digital data stream representing a phase error between said color subcarrier signal and said reference clock signal which is substantially free of DC offset of said color subcarrier signal;
• phase error circuitry, said phase error circuitry operable to convert said phase error to a control voltage;
• and
• a voltage controlled oscillator responsive to said control voltage for generating said sample clock signal.

A method for locking to a color subcarrier signal in an analog video signal, said method comprising the steps of:

• digitizing said color subcarrier signal in said analog video signal to generate a first digital data stream;
• filtering said first digital data stream to substantially eliminate DC offset of said digitized color subcarrier signal to generate a second digital data stream;
• mixing said second digital data stream to generate a third digital data stream representing sum and difference frequencies of a product of said color subcarrier signal and a reference clock signal;
• accumulating said product which is substantially free of DC offset of said color subcarrier signal;
• converting said product to a control voltage;
• and
• controlling a voltage controlled oscillator with said control voltage to generate a sample clock signal.