Patent US3604844A successfully refreshed from Google Patents.
US3604844A
Expired / Lapsed
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Video signal processing amplifier with automatic gain control
Assignee: Central Dynamics Ltd
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Filing: 1969-05-28
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Granted: 1971-09-14
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Expires: 1989-05-28
Abstract
Abstract Automatic gain control circuitry is disclosed for maintaining the chrominance and luminance levels of a composite color television signal at a constant value. First and second test signals are respectively inserted in the 17th and 18th lines of the vertical blanking interval of each television field. The first test signal is typically a 100 IRE unit white pulse while the second is a high frequency burst signal, the frequency of which may correspond to that of the color burst. In order to maintain the level of the chrominance component of the composite color signal at a constant value, the composite color signal is applied to a signal amplifying channel where the chrominance component is extracted and the amplitude thereof is adjusted by a DC control signal which is derived as follows: The composite color signal is also applied to a pulse generator which produces a first sampling pulse during the 18th line of the vertical blanking interval so as to coincide with the approximate center of the second test signal, this sampling pulse being applied to a first sample and hold circuit. After the chrominance level has been adjusted, the adjusted composite color signal is also applied to the first sample and hold circuit. In particular, the high frequency burst test signal is filtered and rectified and the center portion thereof is sampled by the above-mentioned first sampling pulse to thereby derive the above-mentioned DC control pulse for adjusting the level of the chrominance component. The first test signal has its level sampled by a second sampling pulse generated by the pulse generator to thereby derive a second DC control signal which controls the level of the entire composite color television signal.
Inventors
- 👤 John D Ross
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:18
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/52; H04N5/53; H04N17/00; H04N17/02
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
271 words
Circuitry for providing automatic level control of the luminance and chrominance components of a composite color television signal, said circuitry comprising: means for providing said composite color signal, said signal including a first test signal extending in the white direction and indicative of the amplitude of the luminance component of the composite color signal and a second test signal indicative of the amplitude of the chrominance component of said composite color signal, said first and second test signals being respectively disposed in predetermined lines of the vertical blanking interval of said composite color signal; first signal adjusting means responsive to a first control signal and the chrominance component of said composite color signal for adjusting the amplitude of said chrominance component whenever the amplitude of said first control signal deviates from a predetermined amplitude established therefor; second signal adjustment means responsive to a second control signal and the output signal from said first signal adjusting means for adjusting the amplitude of the luminance component of said composite color signal whenever the amplitude of said second control signal deviates from a predetermined amplitude established therefor; means responsive to the second test signal in the output signal from said second signal adjusting means and said composite color signal for generating said first control signal and applying it to said first signal adjusting means; and means responsive to the first test signal in the output signal from said second signal adjusting means and said composite color signal for genErating said second control signal and applying it to said second signal adjusting means; whereby the luminance and chrominance components are automatically maintained at constant levels.
Claim 2
Dependent Claim
271 words
Circuitry for providing automatic level control of the luminance and chrominance components of a composite color television signal, said circuitry comprising: means for providing said composite color signal, said signal including a first test signal extending in the white direction and indicative of the amplitude of the luminance component of the composite color signal and a second test signal indicative of the amplitude of the chrominance component of said composite color signal, said first and second test signals being respectively disposed in predetermined lines of the vertical blanking interval of said composite color signal; first signal adjusting means responsive to a first control signal and the chrominance component of said composite color signal for adjusting the amplitude of said chrominance component whenever the amplitude of said first control signal deviates from a predetermined amplitude established therefor; second signal adjustment means responsive to a second control signal and the output signal from said first signal adjusting means for adjusting the amplitude of the luminance component of said composite color signal whenever the amplitude of said second control signal deviates from a predetermined amplitude established therefor; means responsive to the second test signal in the output signal from said second signal adjusting means and said composite color signal for generating said first control signal and applying it to said first signal adjusting means; and means responsive to the first test signal in the output signal from said second signal adjusting means and said composite color signal for genErating said second control signal and applying it to said second signal adjusting means; whereby the luminance and chrominance components are automatically maintained at constant levels.
Claim 3
Dependent Claim
23 words
Circuitry as in claim 1 where said second signal adjusting means includes means for adjusting the amplitude of the entire composite color signal.
Claim 4
Dependent Claim
33 words
Circuitry as in claim 1 where said second test signal is a high frequency burst signal having a frequency substantially higher than the frequencies of the luminance components of said composite color signal.
Claim 5
Dependent Claim
93 words
Circuitry as in claim 3 where said means for generating said first control signal includes means for rectifying the positive peaks of said second test signal; means responsive to said color composite signal for generating a first sampling pulse occurring in approximate time coincidence with the center of the rectified second test signal; and circuitry responsive to said rectified second test signal and said first sampling pulse to generate said first control signal, the amplitude of which is a function of the amplitude of said rectified second test signal at said center thereof.
Claim 6
Dependent Claim
70 words
Circuitry as in claim 1 where said means for generating said first control signal includes sample pulse generating means responsive to said composite color signal for generating a first sampling pulse occurring in approximate time coincidence with said second test signal; and means responsive to said first sampling pulse and said second test signal for sampling the level of said second test signal and generating said first control signal therefrom.
Claim 7
Dependent Claim
18 words
Circuitry as in claim 5 where said first test signal is a pulse having a substantially constant amplitude.
Claim 8
Dependent Claim
19 words
Circuitry as in claim 6 where the amplitude of said first test signal pulse approximately corresponds to level white.
Claim 9
Dependent Claim
18 words
Circuitry as in claim 7 where said amplitude of said first test signal is approximately 100 IRE units.
Claim 10
Dependent Claim
77 words
Circuitry as in claim 6 where said sample pulse generating means is responsive to said composite color signal for generating a second sampling pulse occurring in approximate time coincidence with said first test signal; and means responsive to said first test signal and said second sampling pulse for sampling the level of said first test signal to generate said second control signal the amplitude of which is a function of the amplitude of said first test signal.
Claim 11
Dependent Claim
25 words
Circuitry as in claim 9 where said first and second test signals respectively occur during the 17th and 18th lines of the vertical blanking interval.
Claim 12
Dependent Claim
36 words
Circuitry as in claim 10 where said sample pulse generating means is responsive to the beginning of said vertical blanking interval to generate said second and first sampling pulses during the 17th and 18th lines, respectively.
References Cited (Backward Citations)
US2798900A
Cited
DE1197498B
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-13 | 1975-03-15 | 1975-09-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-13 | 1979-03-15 | 1979-09-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-13 | 1983-03-15 | 1983-09-14 | $7700.00 | Window Closed / Lapsed |