Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1987-07-13
1989-01-31
Chin, Tommy P.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358140, 358159, 375120, 331 25, H04N 506
Patent
active
048020095
ABSTRACT:
A phase locked loop system for generating a line-locked clock signal for a television signal processing system includes an analog phase-locked loop nested within a digital phase locked loop. The analog phase-locked loop is synchronized to a reference signal which is derived from the most significant bit of a digital oscillator signal generated by a clocked digital oscillator. To reduce instability in this reference signal, the ratio of the frequency of the clock signal to the frequency of the digital oscillatory signal is chosen to be a noninteger value greater than two. In one embodiment of the invention the stability of the reference signal is further enhanced by adaptively delaying transitions in the reference signal by amounts of time that are inversely proportional to the value of the less significant bits of the samples corresponding to the transitions.
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Nillesen, A. H. H. J., "Line-Locked Digital Colour Decoding" Electronic Components and Applications, vol. 7, No. 4, 1986, pp. 239-245.
Gruen, W. I., "Theory of AFC Synchronization Proceedings of the IRE", Aug., 1953, pp. 1043-1048.
Chin Tommy P.
Herrmann Eric P.
Rasmussen Paul J.
RCA Licensing Corporation
Whitacre Eugene M.
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