Switched AFPC loop filter with offset voltage cancellation

Details Switched AFPC loop filter with offset voltage cancellation Switched AFPC loop filter with offset voltage cancellation

1979-05-17

1980-10-14

Martin, John C.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

331 20, H04N 505, H03B 304

Patent

active

042284635

ABSTRACT:
A television horizontal AFPC loop includes a filter, the time constant of which can be switched at the vertical rate for improved operation from standard broadcast signals and from video tape recorders. A transistor switch introduces a voltage offset which perturbs the AFPC filtered oscillator control voltage. The perturbation is reduced by introducing a second offset voltage for reducing the perturbation and improving the synchronization of the oscillator with the synchronizing signals.

REFERENCES:
patent: 3740489 (1973-06-01), Willis
patent: 3846584 (1974-11-01), Itoh et al.
patent: 3931467 (1976-01-01), Kulkens
patent: 4093963 (1978-06-01), Uchida
patent: 4144544 (1979-03-01), Fernsler

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