US4143331A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Summing amplifier for developing a squelch and meter voltage in a radio receiver
Assignee: National Semiconductor Corp
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Filing: 1977-12-16
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Granted: 1979-03-06
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Expires: 1997-12-16
Abstract
Abstract In a radio receiver IF amplifier, a high gain AGC circuit produces a constant signal output regardless of input signal levels in excess of a threshold value. A summing amplifier responds to the AGC voltage and the IF amplifier current to develop a d - c potential directly proportional to the signal input to the amplifier both above and below the AGC threshold. This voltage is useful in the squelch and signal strength meter circuits.
Inventors
- 👤 Ronald W. Page
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 10:01
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/34; H03G3/341; H03G3/3052
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
197 words
An integrated circuit for generating a direct current potential proportional to the signal applied to an alternating current signal amplifier, wherein said signal amplifier includes delayed automatic gain control, said circuit comprising: signal amplifying means having a variable gain characteristic with the gain being controlled to be proportional to the current flowing in said amplifying means and a current control terminal detector means coupled to said signal amplifying means to demodulate said signal and to produce a d-c potential proportional to the output of said signal amplifying means; automatic gain control means responsive to said d-c potential, including a current control means coupled to said terminal and operative to reduce the gain of said signal amplifying means in proportion to said d-c potential, said current control means further including a differential amplifier with a reference input to provide threshold means to delay the onset of automatic gain control until said d-c potential exceeds a predetermined value, and summing amplifier means coupled to said d-c potential and to said signal amplifying means to be responsive to said current flowing in said signal amplifying means to produce a signal input level related current directly proportional to said applied signal.
Claim 2
Dependent Claim
197 words
An integrated circuit for generating a direct current potential proportional to the signal applied to an alternating current signal amplifier, wherein said signal amplifier includes delayed automatic gain control, said circuit comprising: signal amplifying means having a variable gain characteristic with the gain being controlled to be proportional to the current flowing in said amplifying means and a current control terminal detector means coupled to said signal amplifying means to demodulate said signal and to produce a d-c potential proportional to the output of said signal amplifying means; automatic gain control means responsive to said d-c potential, including a current control means coupled to said terminal and operative to reduce the gain of said signal amplifying means in proportion to said d-c potential, said current control means further including a differential amplifier with a reference input to provide threshold means to delay the onset of automatic gain control until said d-c potential exceeds a predetermined value, and summing amplifier means coupled to said d-c potential and to said signal amplifying means to be responsive to said current flowing in said signal amplifying means to produce a signal input level related current directly proportional to said applied signal.
Claim 3
Dependent Claim
32 words
The circuit of claim 1 further including indicator means coupled to said summing amplifier means to produce a visual indication of the strength of said applied signal independent of said threshold means.
Claim 4
Dependent Claim
61 words
The circuit of claim 1 further including an audio amplifier coupled to said detector and a comparator having an output coupled to said audio amplifier to control the operation thereof, a first input coupled to a control for setting a response level, and a second input coupled to the output of said summing amplifier means whereby a variable squelch is achieved.
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) | 1982-03-05 | 1982-09-04 | 1983-03-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-03-05 | 1986-09-04 | 1987-03-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-03-05 | 1990-09-04 | 1991-03-06 | $7700.00 | Window Closed / Lapsed |