Video detector employing PLL system

Details Video detector employing PLL system Video detector employing PLL system

1988-05-19

1989-03-07

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358188, 3581931, 331 17, H04N 514, H04N 5455

Patent

active

048110965

ABSTRACT:
A PLL video detector comprises a phase detector circuit receiving a video intermediate frequency signal and an oscillation output of a VCO for phase-detecting the same. The phase of the oscillation output of the VCO is controlled by a signal obtained by smoothing a detection output of the phase detector circuit by a low-pass filter. In addition, a trap circuit having a center frequency of f.sub.H is provided between the phase detector circuit and the VCO, so that an unecessary component having a frequency of f.sub.H is removed from an output signal of the low-pass filter. Consequently, the VCO stably oscillates, so that occurrence of a buzz sound in a sound output and degradation of the picture quality can be prevented.

REFERENCES:
patent: 4461035 (1984-07-01), Sakamoto
patent: 4568888 (1986-02-01), Kimura et al.
patent: 4578706 (1986-03-01), Sakamoto
patent: 4590440 (1986-05-01), Hague et al.
patent: 4660087 (1987-04-01), Rumreich

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