Video IF signal detector

Details Video IF signal detector Video IF signal detector

1989-12-18

1991-01-08

Shepperd, John W.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358188, H04N 514, H04N 544

Patent

active

049840800

ABSTRACT:
A video IF signal detector includes a first phase detector detecting a phase difference between an input video IF a signal and a first reference signal. A low pass filter acts on an output signal from the first phase detector. A VCO generates the first reference signal and a second reference signal in response to an output signal from the low pass filter. The first reference signal and the second reference signal have a fixed phase relation with each other. The first phase detector, the low pass filter, and the VCO compose a PLL. A second phase detector detects a phase difference between the input vido IF signal and the second reference signal and extracts a baseband video signal from the input video IF signal. The PLL is enabled during a first period where the input video IF signal is independent of display information. The PLL is disabled during a second period where the input video IF signal represents the display information.

REFERENCES:
patent: 4253118 (1981-02-01), Flasza
patent: 4323924 (1982-04-01), Flasza
patent: 4524389 (1985-06-01), Isobe et al.
patent: 4811096 (1989-03-01), Gakumura
patent: 4933767 (1990-06-01), Hyakutake

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