US3678393A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic gain control having a fast broadband attack mode and a slow narrow band receive mode
Assignee: AT&T Inc
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Filing: 1970-09-30
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Granted: 1972-07-18
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Expires: 1990-09-30
Abstract
Abstract An Automatic Gain Control (AGC) circuit having a fast broadband attack mode and a slow narrow band receive mode. A CODAN-like circuit is employed to judge the quality of the received signal. If the quality is poor, the AGC circuit responds to the total received energy. If the quality is good, a narrow band filter along with suitable damping is switched into the AGC loop so that it responds in a stable mode only to the received carrier energy.
Inventors
- 👤 John Anthony Newell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:54
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3052; H03G3/32
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
86 words
AN automatic gain control circuit for an amplifier in a radio frequency receiver comprising a negative feedback path responsive to the output of the amplifier for controlling the gain of said amplifier, means for determining the carrier-to-noise ratio in said output, and means for simultaneously decreasing the band width and increasing the time constant of said path when said ratio exceeds a predetermined value and for simultaneously increasing the band width and decreasing the time constant of said path when said ratio is below said value.
Claim 2
Dependent Claim
86 words
AN automatic gain control circuit for an amplifier in a radio frequency receiver comprising a negative feedback path responsive to the output of the amplifier for controlling the gain of said amplifier, means for determining the carrier-to-noise ratio in said output, and means for simultaneously decreasing the band width and increasing the time constant of said path when said ratio exceeds a predetermined value and for simultaneously increasing the band width and decreasing the time constant of said path when said ratio is below said value.
Claim 3
Dependent Claim
80 words
The combination according to claim 1 in which said means for determining the carrier-to-noise ratio in said output comprises, a voltage controlled oscillator and a phase detector in a phase locked loop configuration such that the output of said detector provides the control signal to said oscillator, means for driving said loop with a portion of said amplifier output, and means responsive to the alternating current component in said detector output for varying said band width and said time constant.
Claim 4
Dependent Claim
94 words
An automatic gain control circuit for an amplifier in a radio frequency receiver comprising a feedback path responsive to the output of the amplifier for controlling inversely the gain of said amplifier, means for determining the carrier-to-noise ratio in said output, a narrow pass band filter tuned to the carrier of said radio frequency, a low pass filter, and means for inserting said band pass filter and said low pass filter in said path when said carrier-to-noise ratio exceeds a predetermined value and for removing said filters when said ratio is below said value.
Claim 5
Dependent Claim
94 words
An automatic gain control circuit for an amplifier in a radio frequency receiver comprising a feedback path responsive to the output of the amplifier for controlling inversely the gain of said amplifier, means for determining the carrier-to-noise ratio in said output, a narrow pass band filter tuned to the carrier of said radio frequency, a low pass filter, and means for inserting said band pass filter and said low pass filter in said path when said carrier-to-noise ratio exceeds a predetermined value and for removing said filters when said ratio is below said value.
Claim 6
Dependent Claim
43 words
The combination according to claim 3 wherein said low pass filter is proportioned relative to said high band pass filter to reduce the gain of said feedback loop to below unity for frequencies at the upper band limits of said band pass filter.
Claim 7
Dependent Claim
59 words
The combination according to claim 4 including means in said path for converting the output of said amplifier into a direct current control signal and wherein said band pass filter is included in the portion of said loop containing said output and wherein said low pass filter is included in the portion of said loop containing said control signal.
Claim 8
Dependent Claim
90 words
An automatic gain control circuit for an amplifier in a radio frequency receiver comprising a feedback path responsive to the output of the amplifier for controlling inversely the gain of said amplifier, a narrow pass band filter tuned to the carrier of said radio frequency in said output, means for determining the carrier-to-noise ratio in the signal passing said filter, and means for inserting said filter in said feedback path when said signal-to-noise ratio exceeds a predetermined value and for removing said filter when said ratio is below said value.
Claim 9
Dependent Claim
90 words
An automatic gain control circuit for an amplifier in a radio frequency receiver comprising a feedback path responsive to the output of the amplifier for controlling inversely the gain of said amplifier, a narrow pass band filter tuned to the carrier of said radio frequency in said output, means for determining the carrier-to-noise ratio in the signal passing said filter, and means for inserting said filter in said feedback path when said signal-to-noise ratio exceeds a predetermined value and for removing said filter when said ratio is below said value.
Claim 10
Dependent Claim
42 words
The combination according to claim 6 including a switching matrix associated with said filter such that the output of said filter is delivered to said means for determining the carrier-to-noise ratio regardless of whether said filter is included in said feedback path.
References Cited (Backward Citations)
US3230458A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-18 | 1976-01-17 | 1976-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-18 | 1980-01-17 | 1980-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-18 | 1984-01-17 | 1984-07-18 | $7700.00 | Window Closed / Lapsed |