Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1981-06-03
1983-01-04
Chin, Tommy P.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
455214, 455333, H04N 544
Patent
active
043674917
ABSTRACT:
Sync-positive and sync-negative video signals appearing across load resistors of synchronous video detector employing array of NPN transistors are coupled via respective voltage dividers to complementary inputs of differential amplifier employing NPN transistors. Signals appearing across load resistor of amplifier are coupled via an active filter to video signal output terminal. Detector load circuits, amplifier load circuit, and active filter each provide high frequency roll off with break point lying between desired video passband and second subharmonic of picture carrier intermediate frequency. Active filter provides response boost within high end of video passband, and response null in vicinity of picture carrier intermediate frequency. Level shift circuit utilizes series resistance of active filter. Differential amplifier has current source responsive to amplifier output to avoid cut off of amplifier transistor receiving sync-negative drive.
REFERENCES:
patent: 3577008 (1971-05-01), Craft
patent: 3914704 (1975-10-01), Craft
patent: 4052673 (1977-10-01), Herzog
patent: 4253118 (1981-02-01), Flasza
Philips Technical Information Brochure (No. 034; 1977), Entitled "TDA 2540 and TDA 2541-New Vision IF ICs".
"Active Filter Cookbook," by D. Lancaster, published in 1975 by Howard W. Sams & Co., Inc., pp. 124-125.
Chin Tommy P.
Meagher William H.
Rasmussen Paul J.
RCA Corporation
Whitacre Eugene M.
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