US3740462A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic chroma gain control system
Assignee: RCA Licensing Corp
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Filing: 1972-04-10
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Granted: 1973-06-19
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Expires: 1992-04-10
Abstract
Abstract Cascaded first and second gain-controlled amplifiers are used in the chrominance channel of a color television receiver. The gain of the first amplifier is controlled by an ACC loop employing a noise-immune detector to detect color burst information. The gain of the second amplifier is controlled by the output of a peak detector which detects picture-interval information at the output of the second amplifier. An ACC system with improved performance during the reception of noisy signals results.
Inventors
- 👤 L Harwood
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 05:46
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/64; H04N9/70; H04N9/71
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
204 words
In a color television receiver an automatic chroma gain control system for processing input chroma signals having burst information and picture-interval information components, said system comprising, a first amplifier having an input terminal adapted to receive said input chroma signals, having an output terminal to provide intermediate chroma signals responsive to said input chroma signals, and having a gain between its said input and said output terminals which is controllable in response to first control signals; noise-immune detector means having an input terminal and having an output terminal providing said first control signal in response to said burst information component coupled to its said input terminal, a second amplifier having an input terminal coupled to said output terminal of said first amplifier to receive said intermediate chroma signals, having an output terminal providing output chroma signals responsive to said intermediate chroma signals applied to its said input terminal, and having a gain between Its said input and said output terminals which is controllable in response to second control signals, and peak detector means having an input terminal and having an output terminal to provide said second control signals in response to peak excursions of said picture-interval information component coupled to its said input terminal.
Claim 2
Dependent Claim
204 words
In a color television receiver an automatic chroma gain control system for processing input chroma signals having burst information and picture-interval information components, said system comprising, a first amplifier having an input terminal adapted to receive said input chroma signals, having an output terminal to provide intermediate chroma signals responsive to said input chroma signals, and having a gain between its said input and said output terminals which is controllable in response to first control signals; noise-immune detector means having an input terminal and having an output terminal providing said first control signal in response to said burst information component coupled to its said input terminal, a second amplifier having an input terminal coupled to said output terminal of said first amplifier to receive said intermediate chroma signals, having an output terminal providing output chroma signals responsive to said intermediate chroma signals applied to its said input terminal, and having a gain between Its said input and said output terminals which is controllable in response to second control signals, and peak detector means having an input terminal and having an output terminal to provide said second control signals in response to peak excursions of said picture-interval information component coupled to its said input terminal.
Claim 3
Dependent Claim
69 words
In a color television receiver an automatic chroma gain control system as claimed in claim 1 wherein said peak detector is characterized by being: a threshold peak detector having an input terminal coupled to said output terminal of said second amplifier and having an output terminal providing a second control signal responsive only to peak excursions of signals applied to its input terminal which exceed a predetermined threshold level.
Claim 4
Dependent Claim
100 words
In a color television receiver an automatic chroma gain control system as claimed in claim 1 wherein said threshold peak detector comprises: a capacitor across which said second control voltages are to be developed, means including a resistance, said means being coupled to said capacitor to determine its quiescent charge condition, semiconductor means coupled to said capacitor and biased into conduction by said peak excursions of signals which exceed a threshold level to modify said quiescent charge condition, the capacitance of said capacitor being chosen large enough that said modification takes place over a period of at least 1/30 second.
Claim 5
Dependent Claim
47 words
In a color television receiver an automatic gain control system as claimed in claim 3 wherein said resistance is chosen large enough that the return to said quiescent charge condition when said semiconductor means is no longer biased into conduction requires a time longer than said period.
Claim 6
Dependent Claim
76 words
In a color television receiver an automatic chroma gain control system as claimed in claim 1 wherein, manual chroma gain control means is coupled to said second amplifier to control its said gain, said peak detector means acting to reduce the likelihood of peak excursions of said output chroma signals causing oversaturation in said receiver, which otherwise tends to be caused by mis-setting of said manual chroma gain control means for too high second amplifier gain.
Claim 7
Dependent Claim
92 words
In a color television receiver an automatic chroma gain control system as claimed in claim 1 including: a threshold detector having an input terminal coupled to said output terminal of said noise-immune detector and having an output terminal at which a color killer signal is provided in response to signals of less than a threshold amplitude applied to its said input terminal, said output terminal of said threshold detector being coupled to control said second amplifier to reduce its said gain substantially to zero in the presence of said color killer signal.
Claim 8
Dependent Claim
35 words
In a color television receiver an automatic gain control system as claimed in claim 1 including: blanking means coupled to said second amplifier to reduce its said gain substantially to zero during horizontal blanking intervals.
Claim 9
Dependent Claim
202 words
In a color television receiver including 1. a first chroma amplifier providing intermediate chroma signals at its output terminal and having its gain controlled by an automatic chroma gain control responsive to the burst information component of said intermediate chroma signals and 2. chroma demodulators having their input terminal adapted to receive signals to be demodulated, which signals if their peak excursions were excessively large could cause oversaturation to occur in said receiver, in combination therewith the improvement comprising: a second chroma amplifier having an input terminal coupled to said first chroma amplifier output terminal, having an output terminal coupled to said chroma demodulators input terminal for providing output chroma signals in response to said intermediate chroma signals applied to its said input, and being of variable gain between its said input and said output terminals as determined by a control signAl applied to itself and, a peak detector having an input terminal coupled to said second chroma amplifier output terminal and having an output terminal at which at least a portion of said control signal is supplied in response to peak excursions of said output chroma signals which exceed a predetermined threshold level, which said improvement provides protection against said oversaturation.
Claim 10
Dependent Claim
202 words
In a color television receiver including 1. a first chroma amplifier providing intermediate chroma signals at its output terminal and having its gain controlled by an automatic chroma gain control responsive to the burst information component of said intermediate chroma signals and 2. chroma demodulators having their input terminal adapted to receive signals to be demodulated, which signals if their peak excursions were excessively large could cause oversaturation to occur in said receiver, in combination therewith the improvement comprising: a second chroma amplifier having an input terminal coupled to said first chroma amplifier output terminal, having an output terminal coupled to said chroma demodulators input terminal for providing output chroma signals in response to said intermediate chroma signals applied to its said input, and being of variable gain between its said input and said output terminals as determined by a control signAl applied to itself and, a peak detector having an input terminal coupled to said second chroma amplifier output terminal and having an output terminal at which at least a portion of said control signal is supplied in response to peak excursions of said output chroma signals which exceed a predetermined threshold level, which said improvement provides protection against said oversaturation.
Claim 11
Dependent Claim
75 words
In a color television receiver the improvement claimed in claim 8 wherein: manual chroma gain control means is coupled to said second chroma amplifier to control its gain between its said input and said output terminals, said peak detector preventing peak excursions of said output chroma signals which could cause oversaturation and which tend to be caused by mis-setting of said manual chroma gain control means for too high gain of said second chroma amplifier.
Claim 12
Dependent Claim
174 words
In a color television receiver the improvement as claimed in claim 9 wherein said peak detector and said manual chroma gain control means are embodied in circuitry comprising: a potentiometer having a first and a second end terminals respectively connected to an operating potential and to a reference potential and having a slider arm terminal; a capacitor having a first end connected to be referred to said reference potential and having a second end at which potentials corresponding to said control signals are developed; resistive means providing a direct-current path coupling said slider arm terminal and said second end of said capacitor; a transistor having an emitter electrode connected to said reference potential, a collector electrode coupled to said second end of said capacitor, and a base electrode coupled to said second chroma amplifier output terminal and means to provide direct current biasing to the base electrode of said transistor sufficient to place said transistor into conduction only when augmented by sufficiently large signal excursions as coupled thereto from said second chroma amplifier output.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-18 | 1976-12-18 | 1977-06-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-18 | 1980-12-18 | 1981-06-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-18 | 1984-12-18 | 1985-06-19 | $7700.00 | Window Closed / Lapsed |