Patent US4426735A successfully refreshed from Google Patents.
US4426735A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radio receiver comprising a frequency locked loop with audio frequency feedback, and a muting circuit
Assignee: US Philips Corp
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Filing: 1980-09-02
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Granted: 1984-01-17
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Expires: 2000-09-02
Abstract
Abstract Radio-receiver having a frequency-locked loop which comprises, arranged one after the other, a tunable voltage-controlled oscillator, a mixer stage, a filtering element, as well as a frequency-voltage converter which is connected to the tunable voltage-controlled oscillator, several stable tunings being possible for each transmitter. An unambiguous selection is made from these stable tunings of a tuning to a desired station by muting the radio receiver in the other stable tuning frequency ranges. To this end the radio receiver according to the invention comprises a muting circuit as well as a control circuit for the muting circuit in which use is made of a further frequency voltage converter comprising an all-pass frequency-dependent 180° phase shifting network, a phase detector and a limiter. By adjusting the muting circuit of the radio receiver to the quiescent condition only in the desired tuning range and by activating it outside this range, a suppression of interstation noise is obtained at the same time.
Inventors
- 👤 Wolfdietrich G. Kasperkovitz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 13:21
CPC Classifications
H; H03; H03D; H03D3/00; H03D3/001; H03D3/003; H03D3/004; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
162 words
A radio receiver having a frequency-locked loop, which includes a voltage-controlled oscillator having an input for a tuning voltage, a mixer stage coupled to the voltage controlled oscillator and connected to an aerial input, a filtering element coupled to the mixer stage and a frequency-voltage converter coupled to the tuning voltage input of the voltage-controlled oscillator, characterized in that an output of the filtering element is coupled to a first input of a phase detector and, via an all-pass frequency-dependent 180° phase shifting network also to a second input of the phase detector, said all-pass frequency-dependent 180° phase shifting network shifting the phase of a signal passing there-through by an amount which depends on the frequency of said signal and is 180° for a predetermined value of said frequency, the phase-detector being coupled, by way of a limiter, to a control input of a muting circuit for blocking an audio signal unless the receiver is substantially correctly tuned to a broadcast transmission.
Claim 2
Dependent Claim
162 words
A radio receiver having a frequency-locked loop, which includes a voltage-controlled oscillator having an input for a tuning voltage, a mixer stage coupled to the voltage controlled oscillator and connected to an aerial input, a filtering element coupled to the mixer stage and a frequency-voltage converter coupled to the tuning voltage input of the voltage-controlled oscillator, characterized in that an output of the filtering element is coupled to a first input of a phase detector and, via an all-pass frequency-dependent 180° phase shifting network also to a second input of the phase detector, said all-pass frequency-dependent 180° phase shifting network shifting the phase of a signal passing there-through by an amount which depends on the frequency of said signal and is 180° for a predetermined value of said frequency, the phase-detector being coupled, by way of a limiter, to a control input of a muting circuit for blocking an audio signal unless the receiver is substantially correctly tuned to a broadcast transmission.
Claim 3
Dependent Claim
117 words
A radio receiver as claimed in claim 1, characterized in that the frequency-voltage converter comprises a further phase detector having first and second inputs, the output of said filtering element being coupled to the first input of said further phase detector and, via a first frequency-dependent 90° phase shifter, to the second input of said further phase detector, and said all-pass frequency-dependent 180° phase shifting network comprises said first frequency-dependent 90°-phase shifter arranged in cascade with a second frequency-dependent 90° phase shifter, each frequency-dependent 90° phase shifter shifting the phase of a signal passing, respectively, therethrough by an amount which depends on the frequency of said signal and is 90° for a predetermined value of said frequency.
Claim 4
Dependent Claim
57 words
A radio receiver as claimed in claim 1 or 2, characterized in that the first input of the phase detector is coupled to the filtering element via a first further limiter and the second input of the phase detector is connected to an output of the all-pass frequency-dependent 180° phase shifting network via a second further limiter.
Claim 5
Dependent Claim
33 words
A radio receiver as claimed in claim 1, characterized in that the phase detector comprises a multiplying stage and a low-pass filter having a bandwidth of the order of magnitude of 1 Hz.
Claim 6
Dependent Claim
24 words
A radio receiver as claimed in claim 1, characterized in that the frequency voltage converter is coupled to the voltage-controlled oscillator via an amplifier-limiter.
Claim 7
Dependent Claim
68 words
A radio receiver as claimed in claim 2, characterized in that the further phase detector comprises a multiplying stage connected to the first and second inputs thereof and a low-pass filter coupled to the multiplying stage, the low-pass filter having a bandwidth of the order of magnitude of the audio frequency range and being connected to a signal processing section of the radio receiver via the muting circuit.
Claim 8
Dependent Claim
60 words
A radio receiver as claimed in claim 2, characterized in that the output of the filtering element is coupled to the first input of the further phase detector via a further amplifier limiter and to the second input of the further phase detector via said further amplifier limiter, a further limiter as well as the first frequency-dependent 90° phase shifter.
Claim 9
Dependent Claim
48 words
A radio receiver as claimed in claim 1, characterized in that an input of the muting circuit is coupled to a noise source circuit for applying a noise signal through said muting circuit to an audio signal processing section of the receiver on activation of the muting circuit.
References Cited (Backward Citations)
US4117410A
Cited
US4283792A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-01-16 | 1987-07-18 | 1988-01-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-01-16 | 1991-07-18 | 1992-01-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-01-16 | 1995-07-18 | 1996-01-17 | $7700.00 | Window Closed / Lapsed |