Phase locked loop system incorporating automatic gain control

Details Phase locked loop system incorporating automatic gain control Phase locked loop system incorporating automatic gain control

1984-12-03

1987-01-06

Shepperd, John W.

Facsimile and static presentation processing

Static presentation processing

Attribute control

H04N 968

Patent

active

046351035

ABSTRACT:
An automatic gain control (AGC) circuit is described in the context of a phase locking system in a digital television receiver. The signal produced by the phase locking system is used to develop a sampling clock signal that is locked in frequency and phase to the color reference burst signal component of a color television signal. An AGC detector develops a gain control signal by averaging only those samples which would correspond to the peaks of the burst signal if the sampling clock signal were locked to the burst signal. The gain control signal is applied to a multiplier which increases or decreases the magnitude of the television signal samples to bring the calculated peak amplitude value of the burst signal within a predetermined range. The AGC circuitry interacts with the phase locking system to decrease the lock-up time when there is a relatively large difference in phase between the burst signal and the sampling clock signal.

REFERENCES:
patent: 4130831 (1978-12-01), Isono et al.
patent: 4170023 (1979-10-01), Yamakoshi et al.
patent: 4523223 (1985-06-01), Luder et al.
patent: 4527145 (1985-07-01), Haussmann et al.
patent: 4539583 (1985-09-01), Flamm et al.
patent: 4556900 (1985-12-01), Willis
T. Fischer, "Digital VLSI Breeds Next-Generation TV Receivers", Electronics, Aug. 11, 1981, pp. 97-103.

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