Automatic frequency control circuit

Details Automatic frequency control circuit Automatic frequency control circuit

1991-10-07

1992-10-06

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358158, H04N 510

Patent

active

051537257

ABSTRACT:
An automatic frequency control circuit includes a phase comparator, a voltage-controlled oscillator, a frequency divider, a decoder, and a discriminating circuit. The phase comparator compares a phase of an input signal of a horizontal sync signal for television with a phase of a signal phase-locked with the horizontal sync signal to generate a control voltage. The VCO outputs a VCO signal having a frequency controlled by the control voltage. The frequency divider divides a frequency of the VCO signal and outputs an intermediate frequency division ratio signal and the phase-locked signal serving as a terminal frequency division ratio output. A decoder logically processes the phase-locked signal, the intermediate frequency division ratio signal, and the VCO signal and outputs a horizontal sync signal phase-locked with the horizontal sync signal. A discriminating circuit triggered at a leading edge of a vertical sync signal for television latches the phase-locked signal and generates an even/odd field discrimination output.

REFERENCES:
patent: 4317133 (1982-02-01), Fernsler et al.
patent: 4631587 (1986-12-01), Turner
patent: 4661798 (1987-04-01), Ohtsu

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