US3697885A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic frequency control circuits
Assignee: RCA Licensing Corp
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Filing: 1970-12-04
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Granted: 1972-10-10
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Expires: 1990-12-04
Abstract
Abstract A circuit used in an automatic frequency control (AFC) scheme employs a voltage divider having a variable arm coupled to a varactor diode to vary the reactance of the diode to enable tuning of a receiver. An AFC error signal is converted into a current and injected into the divider to equalize the loop gain of the AFC system over the tuning range of the receiver.
Inventors
- 👤 Jack Avins
- 👤 Jack Craft
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 03:05
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02; H03J7/04; H03J7/08; H03J7/10
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
293 words
In an apparatus employing an oscillator whose frequency is varied to perform tuning of such apparatus over a range of frequencies, said apparatus including an IF amplifier for responding to an intermediate frequency signal produced by heterodyning a wave from said oscillator with a signal having a frequency in said range, and a discriminator circuit for producing an automatic frequency, control signal proportional to said intermediate frequency signal being different from a desired frequency, in combination therewith, apparatus for providing both tuning and automatic frequency control of said oscillator comprising: a. a variable reactance device coupled to said oscillator and having a voltage responsive reactance which controls the frequency of said oscillator. b. a voltage divider having an adjustable slider coupled to sAid variable reactance device to change the voltage applied thereto when said slider is adjusted. c. first and second transistors of opposite conductivity types each having base, emitter and collector electrodes, said emitter electrode of said first transistor and said emitter electrode of said second transistor being connected to different potential points, d. a first diode connected between the base and emitter electrodes of said first transistor and poled for easy current conduction in the same direction as the base-to-emitter junction of said first transistor, e. a second diode connected between the base and emitter electrodes of said second transistor and poled for easy current conduction in the same direction as the base-to-emitter junction of said second transistor, f. means coupled between said base electrodes of said first and second transistors for applying said automatic frequency control signal thereto, g. means coupling said collectors to said voltage divider at spaced points on opposite sides of said slider selected to provide substantially constant gain fro the loop circuit including said discriminator circuit.
Claim 2
Dependent Claim
293 words
In an apparatus employing an oscillator whose frequency is varied to perform tuning of such apparatus over a range of frequencies, said apparatus including an IF amplifier for responding to an intermediate frequency signal produced by heterodyning a wave from said oscillator with a signal having a frequency in said range, and a discriminator circuit for producing an automatic frequency, control signal proportional to said intermediate frequency signal being different from a desired frequency, in combination therewith, apparatus for providing both tuning and automatic frequency control of said oscillator comprising: a. a variable reactance device coupled to said oscillator and having a voltage responsive reactance which controls the frequency of said oscillator. b. a voltage divider having an adjustable slider coupled to sAid variable reactance device to change the voltage applied thereto when said slider is adjusted. c. first and second transistors of opposite conductivity types each having base, emitter and collector electrodes, said emitter electrode of said first transistor and said emitter electrode of said second transistor being connected to different potential points, d. a first diode connected between the base and emitter electrodes of said first transistor and poled for easy current conduction in the same direction as the base-to-emitter junction of said first transistor, e. a second diode connected between the base and emitter electrodes of said second transistor and poled for easy current conduction in the same direction as the base-to-emitter junction of said second transistor, f. means coupled between said base electrodes of said first and second transistors for applying said automatic frequency control signal thereto, g. means coupling said collectors to said voltage divider at spaced points on opposite sides of said slider selected to provide substantially constant gain fro the loop circuit including said discriminator circuit.
Claim 3
Dependent Claim
76 words
The apparatus according to claim 1 wherein said discriminator circuit provides a first and a second output signal in a push-pull relation, each having a fixed quiescent current io associated therewith, said first signal being applied to the base electrode of said first transistor, said second signal being applied to the base electrode of said second transistor, said first and second transistors operating to provide cancellation of said quiescent current io at said collector electrode connection.
Claim 4
Dependent Claim
78 words
The apparatus according to claim 1 further comprising: a. a switch having a common terminal, and first and second associated terminals which can be selectively connected to said common terminal via a moveable arm associated with said switch, said common terminal being connected to said collector connection of said first and second transistors and said first terminal being coupled to said voltage divider, and b. a source of operating potential connected to said second terminal of said switch.
Claim 5
Dependent Claim
267 words
Control circuitry for tuning the frequency of a variable oscillator responsive to a voltage applied to a variable reactance device coupled to said oscillator, comprising: a. discriminator circuit means having an input terminal responsive to an applied signal frequency to provide at an output terminal a control voltage of a magnitude dependent upon said frequency being different from a desired value, b. first and second transistors each having an emitter, collector and base electrode, each transistor being of opposite conductivity and connected in a series DC path, with the emitter electrode of said first transistor connected to a first point of potential, said collector electrode of said first transistor connected to said collector electrode of said second transistor and said emitter electrode of said second transistor returned to a different point of potential with respect to said first point, c. means coupled to said base electrodes for applying said control voltage thereto to provide at said collector connection a control current proportional thereto, d. an adjustable voltage divider having an output terminal connected to said variable reactance device for tuning said oscillator in accordance with the applied voltage, e. a first resistor coupled between said collector electrode connection of said transistors and a point on said divider, f. a second resistor coupled between said collector electrode connection of said transistors and a second different point on said divider, said first and second resistors serving to inject a portion of said control current into said divider so that said dependency of said control voltage magnitude upon said frequency difference is substantially unaffected by the adjustment of said divider.
Claim 6
Dependent Claim
267 words
Control circuitry for tuning the frequency of a variable oscillator responsive to a voltage applied to a variable reactance device coupled to said oscillator, comprising: a. discriminator circuit means having an input terminal responsive to an applied signal frequency to provide at an output terminal a control voltage of a magnitude dependent upon said frequency being different from a desired value, b. first and second transistors each having an emitter, collector and base electrode, each transistor being of opposite conductivity and connected in a series DC path, with the emitter electrode of said first transistor connected to a first point of potential, said collector electrode of said first transistor connected to said collector electrode of said second transistor and said emitter electrode of said second transistor returned to a different point of potential with respect to said first point, c. means coupled to said base electrodes for applying said control voltage thereto to provide at said collector connection a control current proportional thereto, d. an adjustable voltage divider having an output terminal connected to said variable reactance device for tuning said oscillator in accordance with the applied voltage, e. a first resistor coupled between said collector electrode connection of said transistors and a point on said divider, f. a second resistor coupled between said collector electrode connection of said transistors and a second different point on said divider, said first and second resistors serving to inject a portion of said control current into said divider so that said dependency of said control voltage magnitude upon said frequency difference is substantially unaffected by the adjustment of said divider.
Claim 7
Dependent Claim
75 words
The control circuitry according to clAim 4 further including: a. a first diode connected between the base electrode and emitter electrode of said first transistor and polarized to conduct current in the same direction as said base-to-emitter junction of said first transistor, b. a second diode connected between the base electrode and emitter electrode of said second transistor and polarized to conduct current in the same direction as said base-to-emitter junction of said second transistor.
Claim 8
Dependent Claim
46 words
The control circuit according to claim 4 further including: a. a third resistor coupled between the junction of said second resistor and said collector connection, and a point of reference potential for preventing saturation of said first transistor upon the application of said control voltage thereto.
Claim 9
Dependent Claim
183 words
A circuit for controlling the frequency of an oscillator in a heterodyne receiver by controlling the reactance of a variable reactance device coupled to the frequency determining network of said oscillator, comprising: a. means providing a potential supply source having a pair of terminals; b. first, second, third, fourth, and fifth resistive elements, said first, second and third resistive elements being connected in series between said pair of terminals, said fourth and said fifth resistive elements being connected in series across said second resistive element, and said second resistive element having an adjustable slider connected to said variable reactance device to change the voltage applied thereto to tune said oscillator over a predetermined frequency range; c. automatic frequency control system responsive to deviations of said oscillator frequency from that established by said adjustable slider to produce an error signal; and d. means connecting said automatic frequency control system to the junction of said third and fourth resistive elements, the resistance values of said resistive elements proportioned to equalize the gain of said automatic frequency control system over the tuning range of said oscillator.
Claim 10
Dependent Claim
183 words
A circuit for controlling the frequency of an oscillator in a heterodyne receiver by controlling the reactance of a variable reactance device coupled to the frequency determining network of said oscillator, comprising: a. means providing a potential supply source having a pair of terminals; b. first, second, third, fourth, and fifth resistive elements, said first, second and third resistive elements being connected in series between said pair of terminals, said fourth and said fifth resistive elements being connected in series across said second resistive element, and said second resistive element having an adjustable slider connected to said variable reactance device to change the voltage applied thereto to tune said oscillator over a predetermined frequency range; c. automatic frequency control system responsive to deviations of said oscillator frequency from that established by said adjustable slider to produce an error signal; and d. means connecting said automatic frequency control system to the junction of said third and fourth resistive elements, the resistance values of said resistive elements proportioned to equalize the gain of said automatic frequency control system over the tuning range of said oscillator.
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) | 1975-10-10 | 1976-04-10 | 1976-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-10 | 1980-04-10 | 1980-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-10 | 1984-04-10 | 1984-10-10 | $7700.00 | Window Closed / Lapsed |