Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1979-08-29
1981-04-21
Martin, John C.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358 25, 3581951, H04N 950, H04N 550
Patent
active
042636116
ABSTRACT:
A selectivity network is provided for a synchronous detector, a reference signal circuit, and an AFT circuit. The selectivity network comprises a first tuned circuit coupled across two terminals of the reference signal circuit and tuned to the desired frequency of the I.F. picture carrier. A second tuned circuit is lightly coupled to the first tuned circuit and is coupled across two inputs of the AFT circuit to provide a frequency dependent phase-sifted reference signal to the AFT circuit. The first tuned circuit includes a trap circuit tuned to provide attenuation about a frequency intermediate the frequency of a sound carrier and that picture signal sideband frequency which, upon detection, results in a video signal corresponding to the intercarrier sound second subharmonic frequency. The trap in the reference signal tuned circuit minimizes quadrature distortion in the reference channel and the resultant harmonic distortion in the video signals, which causes sound buzz. The frequency notched reference signal is applied to the AFT tuned circuit, which causes a balancing of the pull-in range of the AFT circuit about the desired picture carrier frequency, thereby immunizing the AFT circuit against noise-pulling. The frequency notch in the AFT circuit at the indicated frequency also minimizes AFT effects of a frequency offset co-channel sound carrier, allowing the automatic acquisition of signals which are offset in frequency toward the lower adjacent channel.
REFERENCES:
patent: 3697685 (1972-10-01), Lunn
patent: 3968325 (1976-07-01), Beriere
patent: 4159482 (1979-06-01), Apeldoorn
patent: 4188639 (1980-02-01), Murakami et al.
Toshiba Television Schematic, No. 13P30E.
Philips Technical Information Pamphlet 034 For Circuits TDA 2540 and TDA 2541, 1977.
Buergerhausen, "TV IF Amplifier With Improved Synchronous Detection", IEEE Transactions BTR, Nov. 1974, pp.279-284.
Gibson Walter G.
Liu Frank C.
Muterspaugh Max W.
Martin John C.
Meagher W. H.
Rasmussen P. J.
RCA Corporation
Yorks, Jr. W. B.
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