Dual phase-control loop horizontal deflection synchronizing circ

Details Dual phase-control loop horizontal deflection synchronizing circ Dual phase-control loop horizontal deflection synchronizing circ

1980-03-13

1982-04-27

Psitos, Aristotelis M.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

307494, 307527, 331 20, 328155, H04N 504, H03K 520, H03B 304, H03K 117

Patent

active

043273769

ABSTRACT:
A television horizontal deflection synchronizing system uses two phase-lock loops. A horizontal oscillator operating at a frequency greater than the horizontal frequency is counted and a bilevel signal near the horizontal frequency is generated. A first phase-lock loop having a relatively long time constant controls the oscillator to maintain the bilevel signal in frequency and phase synchronism with horizontal synchronizing signals. In order to compensate for load-dependent variations in the delay of the horizontal deflection stage, a second phase-lock loop is used. The second phase-lock loop includes a phase detector, one input of which is coupled to an output of the first phase-lock loop and a second input of which is coupled to the deflection circuit for responding to the retrace pulse for enabling the phase detector to produce a current of a first polarity when the bilevel signal has a first value and a current of a second polarity when the bilevel signal has a second value. A loop filter is coupled to an output of the phase detector for filtering the first and second polarity currents to form a control signal. A phase controllable source includes a control input coupled to the loop filter for producing horizontal-rate drive pulses at a time which makes the retrace pulses synchronous with the bilevel signal.

REFERENCES:
patent: 3730989 (1973-05-01), Rhee
patent: 3863080 (1975-01-01), Steckler
patent: 3891800 (1975-06-01), Hanseen et al.
patent: 3924202 (1975-12-01), Craft
patent: 4047223 (1977-09-01), Hofmann
patent: 4068188 (1978-01-01), Yokoyama
patent: 4093963 (1978-06-01), Uchida
patent: 4216396 (1980-08-01), Balaban et al.
patent: 4242602 (1980-12-01), Nakagawa et al.
Mullard Technical Communications, No. 118, Apr. 1973.
U.K. Patent Application GB 2011743 A; published Jul. 11, 1979.

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