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US4843469A
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US
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Rapid signal acquisition and phase averaged horizontal timing from composite sync
Assignee: Grass Valley USA LLC
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Filing: 1987-04-13
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Granted: 1989-06-27
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Expires: 2007-04-13
Abstract
Abstract A circuit for extracting phase averaged horizontal timing with high noise immunity and for rapidly acquiring a video signal from a composite synchronizing signal generates an output signal at the horizontal sync rate, the output signal having leading edges occurring at the leading edges of the horizontal sync pulses of the composite synchronizing signal. The rate of the output signal is phase averaged by comparing the respective leading edges of the output signal and the composite synchronizing signal within a window centered about the leading edges of the output signal. Difference in the phases of the respective leading edges result in an error signal which is used to adjust the rate of the output signal to obtain coincidence of the respective leading edges. The occurrence of the leading edges of the composite synchronizing signal within the window is used to lock the circuit. Failure of the leading edges of the composite synchronizing signal to occur within the window due to a change in video source results in unlocking the circuit and resetting the output signal to a new composite synchronizing signal.
Inventors
- 👤 Rory W. Boyce
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:40
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/04; H04N5/06; H04N5/067; H04N5/073; H03; H03L; H03L7/00; H03L7/06; H03L7/08; H03L7/085; H03L7/095; H03L7/10; H03L7/16; H03L7/18; H03L7/183; H03L7/191; H03L7/197; H03L7/199
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
106 words
A circuit for locking to an input video signal from a source, the input video signal having a composite sync component, comprising: means for generating an output signal at a rate corresponding to the sync rate of the composite sync component; means for phase averaging the output signal with respect to the composite sync component to adjust for variations in the sync rate of the composite sync component; and means for rapidly locking to the composite sync component of a new input video signal having a phase difference greater than a predetermined value from the output signal when the source of the input video signal changes.
Claim 2
Dependent Claim
106 words
A circuit for locking to an input video signal from a source, the input video signal having a composite sync component, comprising: means for generating an output signal at a rate corresponding to the sync rate of the composite sync component; means for phase averaging the output signal with respect to the composite sync component to adjust for variations in the sync rate of the composite sync component; and means for rapidly locking to the composite sync component of a new input video signal having a phase difference greater than a predetermined value from the output signal when the source of the input video signal changes.
Claim 3
Dependent Claim
32 words
A circuit as recited in claim 1 wherein the generating means comprises: an oscillator generating a first frequency signal; and means for dividing the first frequency signal to produce the output signal.
Claim 4
Dependent Claim
35 words
A circuit as recited in claim 2 wherein the dividing means comprises a counter which increments for each cycle of the first frequency signal, the counter automatically resetting at the rate of the output signal.
Claim 5
Dependent Claim
72 words
A circuit as recited in claim 1 wherein the phase averaging means comprises: means for comparing leading edges of the output signal with leading edges of the composite sync component to generate an error signal representative of the time difference between the respective leading edges; and means for applying the error signal to the generating means to adjust the rate of the output signal to bring the respective leading edges into coincidence.
Claim 6
Dependent Claim
104 words
A circuit as recited in claim 4 wherein the comparing means comprises: means for defining a window centered on the leading edges of the output signal; means for generating a first voltage level when the leading edges of the output signal occur prior to the leading edges of the composite sync component within the window; means for generating a second voltage level when the leading edges of the composite sync component occur prior to the leading edges of the output signal within the window; and means for combining the first and second voltage levels with a nominal voltage level to generate the error signal.
Claim 7
Dependent Claim
46 words
A circuit as recited in claim 4 wherein the applying means comprises means for converting the error signal into a voltage level, the voltage level being input to the generating means to adjust the rate of the output signal as a function of the voltage level.
Claim 8
Dependent Claim
62 words
A circuit as recited in claim 1 wherein the acquiring means comprises: means for defining a window centered on the leading edges of the output signal; means for detecting when the leading edges of the composite sync component occur within the window; and means for restarting the generating means when the leading edges of the composite sync component occur outside the window.
References Cited (Backward Citations)
US4092672A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-06-26 | 1992-12-26 | 1993-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-06-26 | 1996-12-26 | 1997-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-06-26 | 2000-12-26 | 2001-06-27 | $7700.00 | Window Closed / Lapsed |