US4607390A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Squelch arrangement for AM/FM radio receiver
Assignee: US Philips Corp
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Filing: 1984-05-31
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Granted: 1986-08-19
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Expires: 2004-05-31
Abstract
Abstract A radio receiver has an IF amplifier whose output is connected to an AM demodulator and an FM demodulator. The noise level at the output of the FM demodulator is measured and, when it exceeds a predetermined threshold level, the audio output stage of the receiver is disconnected from the circuit. Noise generated when amplitude modulated signals with a high degree of modulation are received may cause unwanted disconnection of the output circuit. This is prevented by a circuit connected to the output of the AM demodulator which detects negative peaks of the modulation signal which exceed a negative threshold. The integrated peak signals form a correction signal which prevents disconnection of the output stage.
Inventors
- 👤 Gabriel Faugeron
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:33
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/344
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
162 words
In a radio receiver having IF amplifier means, AM demodulator means and FM demodulator means connected to said IF amplifier means, a receiver output stage selectively connectable to said AM demodulator means or said FM demodulator means, and muting circuit means coupled to said FM demodulation means and responsive to noise signals received therefrom for disconnecting said receiver output stage from said AM or said FM demodulator means when said noise signals exceed a predetermined threshold level, the improvement comprising correction circuit means connected to said AM demodulator means for generating a correction signal in response to AM demodulator output signals indicative of AM modulation exceeding a predetermined modulation degree; and means for applying said correction signal to said muting circuit means to prevent said disconnection of said receiver output stage, whereby said muting circuit means is inactivated when said noise level at said output of said FM demodulator means is created by high degrees of modulation of a received AM signal.
Claim 2
Dependent Claim
162 words
In a radio receiver having IF amplifier means, AM demodulator means and FM demodulator means connected to said IF amplifier means, a receiver output stage selectively connectable to said AM demodulator means or said FM demodulator means, and muting circuit means coupled to said FM demodulation means and responsive to noise signals received therefrom for disconnecting said receiver output stage from said AM or said FM demodulator means when said noise signals exceed a predetermined threshold level, the improvement comprising correction circuit means connected to said AM demodulator means for generating a correction signal in response to AM demodulator output signals indicative of AM modulation exceeding a predetermined modulation degree; and means for applying said correction signal to said muting circuit means to prevent said disconnection of said receiver output stage, whereby said muting circuit means is inactivated when said noise level at said output of said FM demodulator means is created by high degrees of modulation of a received AM signal.
Claim 3
Dependent Claim
65 words
A radio receiver as claimed in claim 1, wherein said muting circuit means comprises means for furnishing a reference signal, comparator means for comparing said noise signals to said reference signal and generating a disconnect signal when said noise signals exceeds said reference signal, and switch means responsive to said disconnect signal for disconnecting said output stage from said AM or said FM demodulator means.
Claim 4
Dependent Claim
96 words
A radio receiver as claimed in claim 2, further comprising means for furnishing an operating mode selection signal signifying desired AM or FM operation; and wherein said correction circuit means comprises threshold circuit means furnishing a threshold output signal when a negative signal applied thereto exceeds a predetermined negative threshold level, interrupter circuit means interconnected between said AM demodulator means and said threshold means for connecting said AM demodulator means to said threshold means only when said receiver is in said AM mode, and integrator means integrating said threshold output signal to provide said correction signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-08-18 | 1990-02-17 | 1990-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-18 | 1994-02-17 | 1994-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-18 | 1998-02-17 | 1998-08-19 | $7700.00 | Window Closed / Lapsed |