Frequency scanning automatic phase control system

Details Frequency scanning automatic phase control system Frequency scanning automatic phase control system

1976-01-16

1977-09-06

Martin, John C.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358159, 331 4, 331 20, H04N 505, H01S 100, H03F 368

Patent

active

040472230

ABSTRACT:
A frequency scanning automatic phase control includes a phase detector, a local oscillator and an APC filter. A coincidence detector includes an AND gate responsive to the horizontal retrace and reference synchronizing pulses. A lock detector also responsive to the retrace and reference sync pulses produces an output signal when a predetermined interval of non-coincidence has existed. An AND gate responsive to both the lock detector and coincidence detector gates a current sink which unbalances the phase detector producing a ramp-like error voltage across the APC filter. A threshold detector coupled to the APC filter activates a discharge circuit also coupled to the filter when the filter voltage exceeds the threshold. The oscillator responds to the variations of error voltage and changes frequency accordingly. Once coincidence occurs frequency variation ceases and is resumed only if non-coincidence returns.

REFERENCES:
patent: 2833923 (1958-05-01), Gruen
patent: 3370252 (1968-02-01), Zoerner
patent: 3715499 (1973-02-01), Steckler

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