US4005256A
Expired / Lapsed
US
⏱️ 0.0 years remaining
AFC circuit
Assignee: GTE Sylvania Inc
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Filing: 1975-11-03
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Granted: 1977-01-25
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Expires: 1995-11-03
Abstract
Abstract A signal combining circuit for combining a tuning bias voltage and an automatic frequency control error voltage for application to a voltage controlled radio frequency tuning means for a television receiver is shown. The voltage controlled radio frequency tuning means has a non-linear frequency versus voltage characteristic and the signal combining circuit includes a resistance means for coupling the error voltage to the tuning means input in a manner that compensates for the non-linearity of the frequency versus voltage characteristic of the tuning means to provide a substantially constant automatic frequency control pull-in range throughout the frequency range of interest.
Inventors
- 👤 Rangaswamy Arumugham
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:19
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02; H03J7/04; H03J7/08; H03J7/10
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
172 words
In a television receiver having a voltage controlled radio frequency tuning means, bias means for providing one of a plurality of bias voltages each of which correspond to a particular television channel to be received, and automatic frequency control means for providing an error voltage, a signal combining circuit comprising: first resistance means connecting said bias means to an input of said tuning means for coupling the bias voltage to said input; second resistance means connecting said automatic frequency control means to said input of said tuning means for coupling a predetermined portion of the error voltage to said input; and third resistance means connected in parallel with said second resistance means, said third resistance means including a threshold device which is nonconductive for bias voltages below a predetermined threshold and which has a dynamic resistance characteristic for bias voltages above said predetermined threshold, for coupling a portion of the error voltage to said input which portion increases with the bias voltage provided by said bias means beyond said predetermined bias voltage.
Claim 2
Dependent Claim
172 words
In a television receiver having a voltage controlled radio frequency tuning means, bias means for providing one of a plurality of bias voltages each of which correspond to a particular television channel to be received, and automatic frequency control means for providing an error voltage, a signal combining circuit comprising: first resistance means connecting said bias means to an input of said tuning means for coupling the bias voltage to said input; second resistance means connecting said automatic frequency control means to said input of said tuning means for coupling a predetermined portion of the error voltage to said input; and third resistance means connected in parallel with said second resistance means, said third resistance means including a threshold device which is nonconductive for bias voltages below a predetermined threshold and which has a dynamic resistance characteristic for bias voltages above said predetermined threshold, for coupling a portion of the error voltage to said input which portion increases with the bias voltage provided by said bias means beyond said predetermined bias voltage.
Claim 3
Dependent Claim
28 words
A signal combining circuit as defined in claim 1 wherein said threshold device is a zener diode and said third resistance means includes a resistor in series therewith.
Claim 4
Dependent Claim
19 words
A signal combining circuit as defined in claim 2 wherein said first and second resistance means are each resistors.
Claim 5
Dependent Claim
28 words
A signal combining circuit as defined in claim 3 wherein said third resistance means includes a diode in series with said zener diode for preventing forward conduction thereof.
Claim 6
Dependent Claim
175 words
In a television receiver having a voltage controlled radio frequency tuning means, bias means for providing one of a plurality of bias voltages each of which correspond to a particular television channel to be received, and automatic frequency control means for providing an error voltage, a signal combining circuit comprising: first resistance means connecting said bias means to an input of said tuning means for coupling the bias voltage to said input; and non-linear second resistance means connecting said automatic frequency control means to said input of said tuning means, said non-linear second resistance means including a first resistor for coupling a predetermined portion of said error voltage to said input over a first frequency range below a predetermined frequency and third resistance means connected in parallel with said first resistor for coupling an increasing portion of said error voltage to said input over a second frequency range above said predetermined frequency, said third resistance means including a zener diode which is nonconductive over said first frequency range and a second resistor in series therewith.
Claim 7
Dependent Claim
175 words
In a television receiver having a voltage controlled radio frequency tuning means, bias means for providing one of a plurality of bias voltages each of which correspond to a particular television channel to be received, and automatic frequency control means for providing an error voltage, a signal combining circuit comprising: first resistance means connecting said bias means to an input of said tuning means for coupling the bias voltage to said input; and non-linear second resistance means connecting said automatic frequency control means to said input of said tuning means, said non-linear second resistance means including a first resistor for coupling a predetermined portion of said error voltage to said input over a first frequency range below a predetermined frequency and third resistance means connected in parallel with said first resistor for coupling an increasing portion of said error voltage to said input over a second frequency range above said predetermined frequency, said third resistance means including a zener diode which is nonconductive over said first frequency range and a second resistor in series therewith.
Claim 8
Dependent Claim
36 words
A signal combining circuit as defined in claim 5 wherein said first resistance means is a resistor and said third resistance means includes a diode in series with said zener diode for preventing forward conduction thereof.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-01-25 | 1980-07-26 | 1981-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-01-25 | 1984-07-26 | 1985-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-01-25 | 1988-07-26 | 1989-01-25 | $7700.00 | Window Closed / Lapsed |