Automatic chroma control circuits

Claim 2

Apparatus for use in a color television receiver of the type including circuitry for processing a composite television signal which signal further contains undesirable noise components, said receiver having a gain controllable chrominance amplifier for selectively amplifying chrominance signals and an oscillatory burst signal transmitted with said composite television signal during a color television transmission, comprising: a. narrow band filter means having an input terminal coupled to said chrominance amplifier and responsive to said oscillatory burst signal to provide at an output terminal thereof a signal having a magnitude proportional to said oscillatory burst signal and any of said accompanying undersired noise signals within the bandpass of said filter means, b. color killer means having an input terminal coupled to the output terminal of said filter means to provide at an output terminal thereof a first control voltage during a color transmission relatively independent of certain noise components and indicative of the presence of said burst signal as propagated through said filter means, said color killer means further operating to provide a second control voltage during a monochrome transmission indicative of the absence of said burst signal, said color killer means further capable of being adversely affected by undesired noise components of relatively large amplitudes, c. means coupling the output of said color killer means to said chrominance amplifier for inactivating the same for said second control voltage and for enabling the same for said first control voltage, d. gain control means including a peak detector having an input terminal coupled to the output terminal of said filter means to provide at an output terminal of said gain control means a third control voltage indicative of the peak value of said burst signal as propagated through said filter means including any peak value due to said undesired noise components, e. means coupling the output of said gain control means to said chrominance amplifier for controlling the gain thereof according to said third control voltage to cause the gain of said amplifier to decrease for both large burst signals and undesired noise signals, whereby the decreased gain of said chrominance amplifier under undesired noise conditions tends to prevent said color killer means from falsely providing said first control voltage during a monochrome transmission.

Claim 3

The apparatuS according to claim 1 wherein: said narrow band filter means further includes amplifier means having an output terminal coupled to said input terminal of said filter means and an input terminal coupled to said output terminal of said filter means and selected to have a gain of and phase shift from said amplifier input terminal to said amplifier output terminal sufficient to cause oscillations about a frequency within said narrow band.

Claim 4

The apparatus according to claim 1 wherein said color killer means includes an average detector circuit for providing said first control signal relatively independent of certain noise components.

Claim 5

Apparatus for use in a color television receiver of the type including circuitry for processing a composite television signal which signal further contains undesirable noise components, said receiver having a gain controllable chrominance amplifier for selectively amplifying chrominance signals and an oscillatory burst signal transmitted with said composite television signal during a color television transmission, comprising: a. narrow band filter means having an input terminal coupled to said chrominance amplifier responsive to said oscillatory burst signal to provide at an output terminal thereof a signal having magnitude proportional to said oscillatory burst signal and any of said accompanying noise signals within the bandpass of said filter means, b. average detector means having an input terminal coupled to the output terminal of said filter means to provide at an output terminal thereof, a first control voltage indicative of the average value of said burst signal as propagated through said filter means during a color transmission, said average detector serving to discriminate against certain noise components which are random in nature, said average detector operating to provide a second control voltage for the absence of said burst signals and capable of being adversely affected by noise components of large amplitude, c. peak detector means having an input terminal also coupled to said output terminal of said filter means to provide at an output terminal thereof a third control voltage indicative of the peak value of said burst signal as propagated through said filter means including any peak value due to said noise components, d. first means coupling the output of said average detector means to said chrominance amplifier for activating the same during the presence of said oscillatory burst signal via said first control voltage, and inactivating the same during a monochrome transmission via said second control voltage, e. second means coupling the output of said peak detector to said chrominance amplifier for controlling the gain thereof according to said third control voltage to cause the gain of said chrominance amplifier to decrease when large noise components are propagated through said filter means, whereby the decreased gain of said chrominance amplifier under undesired noise conditions tends to prevent said average detector from falsely providing said first control voltage having a monochrome transmission.

Claim 6

Apparatus for use in a color television receiver of the type including circuitry for processing a composite television signal which signal further contains undesirable noise components, said receiver having a gain controllable chrominance amplifier for selectively amplifying chrominance signals and an oscillatory burst signal transmitted with said composite television signal during a color television transmission, comprising: a. narrow band filter means having an input terminal coupled to said chrominance amplifier responsive to said oscillatory burst signal to provide at an output terminal thereof a signal having magnitude proportional to said oscillatory burst signal and any of said accompanying noise signals within the bandpass of said filter means, b. average detector means having an input terminal coupled to the output terminal of said filter means to provide at an output terminal thereof, a first control voltage indicative of the average value of said burst signal as propagated through said filter means during a color transmission, said average detector serving to discriminate against certain noise components which are random in nature, said average detector operating to provide a second control voltage for the absence of said burst signals and capable of being adversely affected by noise components of large amplitude, c. peak detector means having an input terminal also coupled to said output terminal of said filter means to provide at an output terminal thereof a third control voltage indicative of the peak value of said burst signal as propagated through said filter means including any peak value due to said noise components, d. first means coupling the output of said average detector means to said chrominance amplifier for activating the same during the presence of said oscillatory burst signal via said first control voltage, and inactivating the same during a monochrome transmission via said second control voltage, e. second means coupling the output of said peak detector to said chrominance amplifier for controlling the gain thereof according to said third control voltage to cause the gain of said chrominance amplifier to decrease when large noise components are propagated through said filter means, whereby the decreased gain of said chrominance amplifier under undesired noise conditions tends to prevent said average detector from falsely providing said first control voltage having a monochrome transmission.