US 4,291,332 AGranted

Phase-locked circuit

AssigneeTokyo Shibaura Denki Kabushiki Kaisha

InventorsMasaaki Kato, Keisuke Ogi

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Abstract

Disclosed is a phase-locked circuit which includes a voltage controlled oscillator to supply a sampling clock signal to an analog-digital converter for converting a composite color television signal into a digital signal, and a control signal generator circuit to apply a control signal to the voltage controlled oscillator in response to the composite color television signal. The control signal generator circuit includes a burst separator for extracting a digital signal component corresponding to a color burst signal from a digital output signal from the analog-digital converter, a phase signal generator producing a reference phase signal, and a digital phase error detector circuit receiving the output signals from the burst separator and phase signal generator and supplying the voltage controlled oscillator with an output signal corresponding to the phase difference between both these input signals.

Claims30

Dependent claims

A phase-locked circuit comprising:

voltage controlled oscillation means;
analog-digital converter means converting an analog input signal containing a reference phase signal component into a digital signal in response to a clock signal from said voltage controlled oscillation means;
reference phase signal separator means for extracting a digital reference phase signal corresponding to said reference phase signal component from a digital output signal supplied from said analog-digital converter means;
and
operation means digitally calculating an error signal corresponding to the difference between a predetermined reference phase difference and a phase difference between said analog reference phase signal component and said clock signal on the basis of the digital reference phase signal from said reference phase signal separator means, and supplying said voltage controlled oscillation means with an analog output signal corresponding to said error signal as a control signal, thereby causing the phase difference between the output signal from said voltage controlled oscillation means and said analog reference phase signal component to be made equal to said predetermined reference phase difference.

2 more elements

Dependencies are inferred from the claim text.