Method and apparatus for controlling the sampling phase of an an

Details Method and apparatus for controlling the sampling phase of an an Method and apparatus for controlling the sampling phase of an an

1987-04-10

1989-01-10

Britton, Howard W.

Facsimile and static presentation processing

Static presentation processing

Attribute control

358326, H04N 9475

Patent

active

047977302

ABSTRACT:
A composite analog video signal is sampled at precise locations relative to the phase of the unmodulated color subcarrier along each horizontal line of the video signal. This provides a digitized signal with a constant phase relationship relative to the unmodulated subcarrier phase, which relationship may be used to remove sampling clock phase errors. The digitized samples are filtered by a digital bandpass filter to remove DC and second harmonic noise distortion. Two phase error measurements of the actual sampling clock phase are taken by averaging two sets of burst samples at 0.degree. and 180.degree. crossings, respectively, on selected horizontal lines. These phase error measurements are separately stored, and then are updated on selected alternate horizontal lines to cancel sampling nonlinearity errors. The updated signals are differenced to provide a phase error signal indicative of any sampling clock phase errors. The phase error signal is used to correct the phase of the sampling clock which is supplied to the sampling converter.

REFERENCES:
patent: 4212027 (1980-07-01), Lemoine
patent: 4301466 (1981-11-01), Lemoine et al.
patent: 4352121 (1982-09-01), Lilley
patent: 4400720 (1923-08-01), Hinn
patent: 4404583 (1983-09-01), Tatami
patent: 4438451 (1984-03-01), Hinn et al.

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