US3591716A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic frequency control circuit
Assignee: Zenith Electronics LLC
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Filing: 1968-08-01
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Granted: 1971-07-06
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Expires: 1988-08-01
Abstract
Abstract An automatic frequency control circuit for an oscillator having a frequency determining circuit includes a capacitor which is coupled across the frequency determining circuit by a switching device. The operating period of the switching device is controlled by a constant current source. A control signal, developed by a phase detector, is coupled to an input terminal of the constant current source to adjust the operating period of the switching device.
Inventors
- 👤 Howard F Jirka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:50
CPC Classifications
H; H03; H03L; H03L7/00; H03L7/06; H03L7/08; H03L7/099; H04; H04N; H04N5/00; H04N5/04; H04N5/12; H04N5/126
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
180 words
An automatic frequency control circuit for a signal generator having a frequency determining circuit, comprising: a capacitor having a first electrode coupled to one terminal of said frequency determining circuit and also having a second electrode; means, including a single switching device having a controllable operating period fully adjustable over a range from 0* to 360* conduction during each cycle of said signal generator, for coupling said second capacitor electrode to a second terminal of said frequency determining circuit during the operating period of said device; a constant current source having an input terminal and also having a pair of output terminals coupled across said switching device; means independent of said signal generator for energizing said constant current source; means for developing a control signal indicative of the deviation in frequency of the output signal of said signal generator from that of a reference signal; and means for coupling said control signal to said input terminal of said constant current source for controlling the operating period of said switching device to alter the resonant frequency of said frequency determining circuit.
Claim 2
Dependent Claim
180 words
An automatic frequency control circuit for a signal generator having a frequency determining circuit, comprising: a capacitor having a first electrode coupled to one terminal of said frequency determining circuit and also having a second electrode; means, including a single switching device having a controllable operating period fully adjustable over a range from 0* to 360* conduction during each cycle of said signal generator, for coupling said second capacitor electrode to a second terminal of said frequency determining circuit during the operating period of said device; a constant current source having an input terminal and also having a pair of output terminals coupled across said switching device; means independent of said signal generator for energizing said constant current source; means for developing a control signal indicative of the deviation in frequency of the output signal of said signal generator from that of a reference signal; and means for coupling said control signal to said input terminal of said constant current source for controlling the operating period of said switching device to alter the resonant frequency of said frequency determining circuit.
Claim 3
Dependent Claim
21 words
An automatic frequency control circuit as set forth in claim 1 in which said switching device comprises a unilatErally conductive device.
Claim 4
Dependent Claim
42 words
An automatic frequency control circuit as set forth in claim 2 in which said unilaterally conductive device comprises a diode having a cathode coupled to said second capacitor electrode and an anode coupled to said second terminal of said frequency determining circuit.
Claim 5
Dependent Claim
30 words
An automatic frequency control circuit as set forth in claim 1 in which said constant current source comprises a transistor having emitter and collector electrodes coupled across said switching device.
Claim 6
Dependent Claim
45 words
An automatic frequency control circuit as set forth in claim 1 which further comprises a source of reference signals and in which said means for developing a control signal comprises a phase detector coupled to said source of reference signals and to said signal generator.
Claim 7
Dependent Claim
34 words
An automatic frequency control circuit as set forth in claim 1 in which said signal generator comprises the horizontal oscillator of a television receiver and said frequency determining circuit comprises a tuned resonant circuit.
Claim 8
Dependent Claim
26 words
An automatic frequency control circuit as set forth in claim 1 in which said signal generator comprises the color reference oscillator of a color television receiver.
References Cited (Backward Citations)
US2708739A
Cited
US3319179A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-07-05 | 1975-01-04 | 1975-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-07-05 | 1979-01-04 | 1979-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-07-05 | 1983-01-04 | 1983-07-06 | $7700.00 | Window Closed / Lapsed |