US 4,309,725 AGranted

Signal processor for beam-scan velocity modulation

AssigneeRCA Corporation

InventorWillem H. Groeneweg

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Abstract

In a signal processor for a beam-scan velocity modulation system in a color TV receiver, a video signal derived from the receiver's luminance channel (or from a combination of the color signal inputs to the receiver's kinescope drivers) is applied to a CR differentiator. Differentiator output is applied to the base of a first transistor disposed with a second transistor to form a first differential amplifier, and to the base of a third transistor disposed with a fourth transistor to form a second differential amplifier. Common load circuit for double-ended limiter formed by the two amplifiers is coupled to collectors of third and fourth transistors. Base bias for second transistor is positively offset from common base bias for first and third transistors, while base bias for fourth transistor is negatively offset therefrom. Output stage of processor, responsive to voltage across common load circuit, drives auxiliary deflection coils via coupling capacitor, which exhibits series resonance with coils at frequency in midband of video signal frequency range.

Claims7

Dependent claims

In an image display system, including a source of image-representative signals;

an image display device having a display screen and an electron gun assembly for directing at least one beam of electrons toward said display screen;
means for effecting beam deflection in a manner causing said beam of electrons to repetitively trace a raster of scanning lines on said display screen;
and means for modulating the velocity of scanning of said lines;
apparatus comprising the combination of:
means coupled to said source for differentiating said image-representative signals;
double-ended limiter means, responsive to the differentiated signal output of said differentiating means, for developing a clipped signal output in which output signal excursions in one direction are clipped at a first predetermined level and output signal excursions in the opposite direction are clipped at a second predetermined level;
said limiter means including first threshold establishing means for precluding said limiter means from responding to excursions of said differentiated signal of a first polarity and of a magnitude below a first threshold magnitude, and second threshold establishing means for precluding said limiter means from responding to excursions of said differentiated signal of a second polarity and of a magnitude below a second threshold magnitude;
and
means for supplying said clipped signal output to said scanning velocity modulating means.

6 more elements

Dependencies are inferred from the claim text.