U.S. Philips Corporation

Wilhelm Moring

Antonius H Nillesen

Walter H Demmer

Jurgen Ruprecht

Detlef W Oldach

Gerd Brand

In a circuit arrangement for deriving digital color signals from an analog television signal by means of an A/D converter, which forms a digital television signal from the analog television signal in synchronism with a clock signal which corresponds to a whole multiple of the line frequency of the television signal, and further by means of a demodulator, a first phase detector, a first phase calculator and a signal generator, which are interconnected in a phase-locked loop, interference-free demodulation of the chrominance signal in the composite television signal is guaranteed, even when the frequency of the clock signal fluctuates, in that the first phase calculator is supplied not only with a color phase signal from the first phase detector but also with a reference phase signal from a reference circuit which is a measure of the frequency difference or phase difference between the clock signal and a reference signal of stable frequency.

Circuit arrangement for deriving digital color signals from an analog

In a circuit arrangement for synchronization of the phase of a frequency-divided signal with an edge of finite slope of an essentially periodic synchronizing signal with an oscillator supplying a clock signal, a frequency divider which generates the frequency-divided signal and a phase detector which comprises a first comparator for coarse phase detection, a second comparator for fine phase detection and a selector circuit which derives a resulting phase signal applied to the oscillator to control the frequency of the clock signal and originating from the first comparator in the case of large phase variations and from the second comparator in the case of small phase variations, precise adjustment to the edge is nevertheless achieved in the case of an amplitude-discrete synchronizing signal with limited time resolution because of the fact that the synchronizing signal is applied to the phase detector as a sequence of amplitude-discrete values which is formed by sampling the synchronizing signal with the clock signal, a sufficient number of amplitude stages being provided for the edge in the synchronizing signal.

Circuit arrangement for synchronization of a signal

A circuit arrangement for obtaining a control quantity which is dependent on the phase shift of a color burst signal comprising an amplitude factor with respect to a reference signal, preferably of approximately the same frequency, which is phase-locked to a clock signal with which the amplitude values of the color burst signal are sampled and whose frequency is the 4n-fold of the frequency of the reference signal. n is an integer and the keying occurs in such manner that a first sampled difference signal obtained by the sampling and a second sampled difference signal shifted by a quarter of a cycle of the color burst signal, are obtained which are proportional to the amplitude of the color burst signal. For evaluating as directly as possible the phase error independently of the amplitude factor, at least one sampled difference signal (X and Y, respectively) is divided by the amplitude factor (A) in a conversion stage (55) in such manner that at least one phase-sensitive control quantity is obtained which consists substantially of sin- and/or cos-members of the phase angle (.alpha.), optionally of a sum or a difference or a product thereof which is at least substantially independent of the amplitude factor.

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Hamburg, Germany

Wilhelm Moring