Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1988-08-29
1990-07-31
Chin, Tommy P.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
331 25, 455192, 455251, H04N 550, H04B 118
Patent
active
049454153
ABSTRACT:
A circuit for providing rapid charge and discharge of a capacitive load is utilized in conjunction with a phase detector error signal output generated in a television video demodulator system for controlling the operating frequency of the local oscillator. The circuit comprises a pair of comparators each biased to a respective threshold level whereby the first comparator provides an output signal when the error signal supplied thereto from the phase detector exceeds its threshold level and the second comparator provides an output signal when the error signal is less than its threshold level. An additional circuit is coupled to the outputs of the pair of comparators and is responsive to the first comparator for sourcing current to the capacitive load while being responsive to the second comparator for sinking current from the load. The capacitive load may be the AFC filter of an AFC loop of a television receiver wherein the local oscillator frequency is controlled by the voltage developed across the filter.
REFERENCES:
patent: 4796102 (1989-01-01), McGinn
patent: 4853641 (1989-08-01), McGinn
Bingham Michael D.
Chin Tommy P.
Motorola Inc.
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