Digital signal phase measuring apparatus as for a phase-locked loop
AssigneeRCA Corporation
InventorThomas V. Bolger
Life of this patent
Estimating the term…
Abstract
A phase measuring arrangement for sampled signals changes the phase of the sampling signal in fine phase increments while comparing the magnitudes of the signal samples so produced to determine whether they have magnitudes within a given range of values. The range of values is indicative of a known phase angle. The number of magnitudes falling within the given range is indicative of the phase of the sampled signal relative to the known phase angle. Embodiments are disclosed in which such phase measuring arrangement is employed in a phase-locked loop useful for processing chrominance signals in a television receiver.
Claims21
Measuring apparatus comprising:
- a source of sampled signals developed in accordance with a sampling signal;
- phasing means coupled to said source for changing the phase of said sampling signal in predetermined increments;
- comparing means coupled to said source for developing indications that said sampled signals have magnitudes within a predetermined range of values;
- and
- counting means coupled to said comparing means for counting the number of said indications to produce a measure of the phase of said sampled signals.
Phase locking apparatus comprising:
- oscillator means for generating a clocking signal having a frequency responsive to a control signal;
- phasing means coupled to said oscillator means for changing the phase of said clocking signal in predetermined increments to develop a sampling signal;
- a source of sampled signals developed in accordance with said sampling signal;
- comparing means coupled to said source for developing indications that said sampled signals have magnitudes within a predetermined range of values;
- counting means coupled to said comparing means for counting the number of said indications to produce a measure of the phase of said sampled signals;
- and
- control means coupled to said counting means for developing said control signal for said oscillator means in response to said measure of the phase of said sampled signals.
In a television receiver including a source of analog video signals having color subcarrier reference burst and color information components, apparatus comprising:
- analog-to-digital converting means coupled to said source for developing video samples representing said analog video signals in accordance with a sampling signal;
- phasing means coupled to said analog-to-digital converting means for changing the phase of said sampling signal in predetermined increments when said video samples representing said color subcarrier reference burst component are developed;
- comparing means coupled to said analog-to-digital converting means for developing indications that said video samples representing said color subcarrier reference burst component have magnitudes within a predetermined range of values;
- counting means coupled to said comparing means for counting the number of said indications to produce a measure of the phase of said video samples representing said color subcarrier reference burst component;
- and
- control means coupled to said counting means and responsive to said measure of the phase for controlling the phase of said sampling signal.
A method for measuring the phase of a sampled signal developed in accordance with a sampling signal, comprising the steps of:
- (a) for a first signal sample:
- (1) determining whether said signal sample has a magnitude within a predetermined range of values and, if so, developing an indication thereof;
- (2) counting the indication so developed;
- and
- (3) changing the phase of said sampling signal by a predetermined phase increment;
- and
- (b) for a predetermined number of subsequent signal samples, repeating steps (a)(1), (a)(2) and (a)(3) for each one of said predetermined number of subsequent signal samples;
- (c) producing the counted number of said indications stored in steps (a) and (b) as the measure of said phase.
Dependencies are inferred from the claim text.