Patent US3922609A successfully refreshed from Google Patents.
US3922609A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Digital automatic frequency control loop for a local oscillator
Assignee: Nokia Deutschland GmbH
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Filing: 1974-06-17
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Granted: 1975-11-25
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Expires: 1994-06-17
Abstract
Abstract The invention provides a method and apparatus for automatically controlling the local-oscillator frequency in a superheterodyne receiving section of a sound reproduction system through the use of a digital a.f.c. circuit. A frequency is derived from the local oscillator frequency and compared with a modulator frequency. The discriminator forms a dc voltage corresponding to the difference between the local oscillator frequency and the discriminator frequency. A varactor in the local oscillator is controlled with the dc voltage such that the local oscillator frequency varies opposite the direction of control of the dc voltage.
Inventors
- 👤 Lothar Grohmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:25
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02; H03J7/04; H03J7/06
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
231 words
A method for automatically controlling the frequency of a local oscillator in the superheterodyne receiving section of an image-and/or sound-reproduction arrangement, which frequency is adjusted with a tuning arrangement, and which superheterodyne receiving section contains an intermediate frequency circuit for transmitting a stable intermediate frequency and an automatic frequency control loop with a frequency discriminator tuned to a stable frequency wherein a frequency is derived from the local oscillator and compared with the discriminator frequency, the discriminator forms a dc voltage corresponding to the difference between the local oscillator frequency and the discriminator frequency, and a varactor in the local oscillator is controlled with the dc voltage such that the frequency derived from the local oscillator varies in a direction opposite to the direction of control of said dc voltage generated by said frequency discriminator, wherein the improvement comprises: injecting the continuous waves of the local oscillator output into the automatic frequency control loop; dividing said continuous waves into an uninterrupted sequence of equally long wave trains whose number of single waves is the difference between the comparative values of the transmitter frequency adjusted to the tuning arrangement and the positive or negative value of the intermediate frequency referenced to a decade value of the transmitter frequency; and forming a single wave for each wave train whereby the discriminator frequency is equal to the decade value of the transmitter frequency adjusted.
Claim 2
Independent Claim
231 words
A method for automatically controlling the frequency of a local oscillator in the superheterodyne receiving section of an image-and/or sound-reproduction arrangement, which frequency is adjusted with a tuning arrangement, and which superheterodyne receiving section contains an intermediate frequency circuit for transmitting a stable intermediate frequency and an automatic frequency control loop with a frequency discriminator tuned to a stable frequency wherein a frequency is derived from the local oscillator and compared with the discriminator frequency, the discriminator forms a dc voltage corresponding to the difference between the local oscillator frequency and the discriminator frequency, and a varactor in the local oscillator is controlled with the dc voltage such that the frequency derived from the local oscillator varies in a direction opposite to the direction of control of said dc voltage generated by said frequency discriminator, wherein the improvement comprises: injecting the continuous waves of the local oscillator output into the automatic frequency control loop; dividing said continuous waves into an uninterrupted sequence of equally long wave trains whose number of single waves is the difference between the comparative values of the transmitter frequency adjusted to the tuning arrangement and the positive or negative value of the intermediate frequency referenced to a decade value of the transmitter frequency; and forming a single wave for each wave train whereby the discriminator frequency is equal to the decade value of the transmitter frequency adjusted.
Claim 3
Dependent Claim
179 words
An improved receiving section of an image-and/or sound reproduction arrangement wherein there is provided at least one radio frequency input circuit, one local oscillator, one mixer, one intermediate frequency circuit having a predetermined intermediate frequency, one demodulator and one tuning arrangement for setting the frequency of the local oscillator and the pass frequency of the radio frequency input circuit and wherein there is provided an automatic frequency control loop having a frequency discriminator between the output and one automatic frequency control input of the local oscillator wherein the improvement comprises: a resettable digital pulse counter having a first reset input and a second input coupled to said local oscillator; an adding arrangement; an adjustable comparator; a constant-value circuit, the outputs of said pulse counter and said constant-value circuit connected to the inputs of said adding arrangement, said reset input coupled to the output of said comparator; a common manual tuning device for adjusting said comparator arrangement and said tuning arrangement; and a wave shaper coupled between the output of said comparator arrangement and the input of said frequency discriminator.
Claim 4
Dependent Claim
179 words
An improved receiving section of an image-and/or sound reproduction arrangement wherein there is provided at least one radio frequency input circuit, one local oscillator, one mixer, one intermediate frequency circuit having a predetermined intermediate frequency, one demodulator and one tuning arrangement for setting the frequency of the local oscillator and the pass frequency of the radio frequency input circuit and wherein there is provided an automatic frequency control loop having a frequency discriminator between the output and one automatic frequency control input of the local oscillator wherein the improvement comprises: a resettable digital pulse counter having a first reset input and a second input coupled to said local oscillator; an adding arrangement; an adjustable comparator; a constant-value circuit, the outputs of said pulse counter and said constant-value circuit connected to the inputs of said adding arrangement, said reset input coupled to the output of said comparator; a common manual tuning device for adjusting said comparator arrangement and said tuning arrangement; and a wave shaper coupled between the output of said comparator arrangement and the input of said frequency discriminator.
Claim 5
Dependent Claim
26 words
A receiving section according to claim 2 wherein the value in said constant-value circuit equals the value of the intermediate frequency of said intermediate frequency circuit.
Claim 6
Dependent Claim
32 words
A receiving section according to claim 3 wherein the value of the frequency of said frequency discriminator is equivalent to the value of the transmitter frequency, preselectable with the manual tuning device.
Claim 7
Dependent Claim
62 words
A method according to claim 1 wherein the continuous waves divided into equally long wave trains are formed from the continuous waves of the output of said local oscillator by frequency division at a ratio of 1:M and that the discriminator frequency is equal to the decade value of the adjusted transmitter frequency, which value is divided at the same 1:M ratio.
Claim 8
Dependent Claim
35 words
A receiving section according to claim 3 further including a frequency divider having a fixed division ratio of 1:M inserted between the output of said local oscillator and the input of said digital pulse counter.
Claim 9
Dependent Claim
19 words
A receiving section according to claim 4 wherein said wave shaper comprises a pulse-shaping stage and a low-pass amplifier.
Claim 10
Dependent Claim
27 words
A receiving section according to claim 4 further including a code converter coupled between the output of said adding arrangement and the input of said comparator arrangement.
Claim 11
Dependent Claim
15 words
A receiving section according to claim 8 wherein said comparator arrangement is a coincidence circuit.
Claim 12
Dependent Claim
25 words
A receiving section according to claim 8 wherein said comparator arrangement comprises the multi-digit switch elements of a multi-decade preselection switch and an AND circuit.
Claim 13
Dependent Claim
53 words
A receiving section according to claim 10 wherein the automatic frequency control loop includes, for each adjustable decade of the transmitter frequency to be received, a divider branch which is coupled in parallel with other divider branches comprising a decade counter, a full-adder, a constant-value block, a code converter and a comparator element.
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) | 1978-11-24 | 1979-05-26 | 1979-11-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-24 | 1983-05-26 | 1983-11-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-24 | 1987-05-26 | 1987-11-25 | $7700.00 | Window Closed / Lapsed |