SECAM identification circuit

Details SECAM identification circuit SECAM identification circuit

1977-01-07

1978-02-07

Griffin, Robert L.

Facsimile and static presentation processing

Static presentation processing

Attribute control

358 26, H04N 946, H04N 949

Patent

active

040729834

ABSTRACT:
SECAM burst signals, which recur at the line scanning rate and which change on a line-to-line basis between 4.25 MHz (corresponding to a B-Y subcarrier frequency) and 4.40625 MHz (corresponding to an R-Y subcarrier frequency) are utilized to provide line-by-line color identification and color killer signals to associated demodulation apparatus.
Synchronizing burst signals and color information signals are separated from the remainder of a composite video signal by means of a "cloche" filter which, during each active line scanning interval, is characterized by a resonant frequency of 4.286 MHz and a relatively low Q (wide bandwidth). During the burst portion of each line retrace interval, the response of the filter is shifted such that its resonant frequency corresponds to one of the burst frequencies (e.g., the R-Y burst frequency of 4.40625 MHz) and the Q is increased to provide a narrower bandwidth response. Consecutive R-Y and B-Y bursts applied to the filter are thereby respectively reinforced and suppressed. The higher amplitude R-Y bursts (which recur at one-half the line scanning rate) are supplied along with a SECAM switching square wave to a phase comparator. The output of the comparator is filtered to provide a color killer and phase correction signal to activate or inactivate the color circuits and to properly phase the bistable circuit (SECAM flip-flop) which generates the switching square wave.

REFERENCES:
patent: 3860954 (1975-01-01), Tsuchiya
patent: 3984863 (1976-10-01), Fessard
patent: 4009487 (1977-02-01), Derenbecher, Jr.

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