Gte Sylvania Incorporated

Kenneth J Burdick

Robert C Wheeler

Wilfred L Hand

Douglas W Constable

Paul G Wolfe

Arthur H Klein

Charles B Neal

A method and circuit for detecting and removing chrominance signal components from the luminance channel of a television receiver is shown. The luminance channel is separated into distinct subchannels, one of which has a filter providing attenuation at the chrominance subcarrier frequency. A detection circuit operates to select the output of the filtered subchannel whenever a chrominance subcarrier signal appears in the luminance channel. The detection circuit is sensitive to the phase relationship between the chrominance signal and a portion of the luminance signal and is therefore substantially immune to signals other than chrominance subcarriers, including high frequency components of the luminance signal.

Signal-dependent chrominance subcarrier filtering circuit

A DC controlled amplifier is used to control the chrominance gain, and hence the color saturation, of a television receiver. The voltage on the wiper of a Color Control variable resistor and the output of an Automatic Color Level (ACL) detector are combined in a summing network to provide a DC voltage to the controlled amplifier. The ACL detector develops an output voltage that tends to maintain the peak-to-peak chrominance signal, and therefore the color saturation, at or below a threshold level. A control tracking circuit varies the threshold level in accordance with the voltage on the wiper of the color control variable resistor, thereby maintaining the dynamic range of the Automatic Color Level Control System relatively independent of the setting of the Color Control.

Automatic color level control system with threshold tracking

A controlled current source circuit using PNP mirror transistors and having wide frequency bandwidth as well as correction for D.C. offset, said circuit comprised of first and second PNP transistors, one of which is connected as a diode, the base terminals of which are commonly connected, the collector terminals of each of which are connected respectively to first and second terminals of a current bias means providing control of emitter-base characteristics and correction for offset caused by base currents, the emitter terminals of which are each connected respectively to first and second resistors, the resistors connected to common potential source, wherein mirror currents are tapped from the connections between the emitter terminals and the resistors and wherein the output mirror current is the collector current of an NPN transistor, the base and collector terminals of which are respectively connected to the collector and emitter terminals of the second PNP transistor.

PNP Current mirror

A video processing system for a television receiver is shown. The video processing system includes a gain controlled stage through which a video signal is coupled. The gain of the stage is controlled to provide contrast control of the video signal. The video signal is also applied to an aperture correction circuit which develops an aperture correction signal including a pre-shoot transient responses. The aperture correction signal is also coupled through the gain controlled stage so that it is amplified or attenuated by the same amount as the video signal. An automatic peaking control circuit receives the pre-shoot and over-shoot signals to generate an automatic control signal to control the gain of the aperture correction circuit. A tracking control circuit causes the automatic peaking control circuit to accurately track the setting of an adjustable control which controls the gain of the aperture correction circuit. The output of the gain controlled stage is coupled to an output stage where the black level of the video signal is controlled by a black level control circuit. The disclosed video processing system is further adapted for fabrication in integrated circuit form.

Growing community of inventors

Wyoming, NY, United States of America

Kenneth J Burdick