US5465406A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic gain control overshoot limiter for AM receiver
Assignee: Visteon Global Technologies Inc
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Filing: 1994-09-06
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Granted: 1995-11-07
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Expires: 2014-09-06
Abstract
Abstract A digital radio receiver avoids overshoot or undershoot of an AGC control loop by isolating a carrier signal using an adaptive narrow bandpass filter. The carrier strength signal is used to control either a full AGC loop or an AGC overshoot limiter to avoid sudden changes in the audio output level.
Inventors
- 👤 John E. Whitecar
- 👤 Robert D. Plowdrey
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:41
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3052
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
107 words
A method of processing an AM IF signal including a carrier signal and a modulating signal, said method comprising the steps of: recovering said carrier signal from said AM IF signal substantially without modulation sidebands; integrating said recovered carrier signal to generate a carrier strength signal; forming a reciprocal of said carrier strength signal; multiplying said recovered carrier signal and said reciprocal to generate a normalized mixing signal; mixing said normalized mixing signal and said AM IF signal to recover said modulating signal; comparing said carrier strength signal with a comparison signal; and modifying said AM IF signal by a gain factor in response to said comparison.
Claim 2
Independent Claim
107 words
A method of processing an AM IF signal including a carrier signal and a modulating signal, said method comprising the steps of: recovering said carrier signal from said AM IF signal substantially without modulation sidebands; integrating said recovered carrier signal to generate a carrier strength signal; forming a reciprocal of said carrier strength signal; multiplying said recovered carrier signal and said reciprocal to generate a normalized mixing signal; mixing said normalized mixing signal and said AM IF signal to recover said modulating signal; comparing said carrier strength signal with a comparison signal; and modifying said AM IF signal by a gain factor in response to said comparison.
Claim 3
Dependent Claim
28 words
The method of claim 1 wherein said carrier signal is recovered using an adaptive narrowband filter substantially eliminating the modulation sidebands at frequencies greater than about 20 Hertz.
Claim 4
Dependent Claim
16 words
The method of claim 1 wherein said comparison signal is proportional to said normalized mixing signal.
Claim 5
Dependent Claim
29 words
The method of claim 3 further comprising the step of reducing said gain factor when said comparison signal exceeds said carrier strength signal, according to a predetermined attack time.
Claim 6
Dependent Claim
30 words
The method of claim 4 further comprising the step of increasing said gain factor when said comparison signal falls below said carrier strength signal, according to a predetermined decay time.
Claim 7
Dependent Claim
15 words
The method of claim 1 wherein said comparison signal is comprised of a predetermined constant.
Claim 8
Dependent Claim
30 words
The method of claim 6 wherein said gain factor for modifying said AM IF signal is selected to minimize a difference between said carrier strength signal and said predetermined constant.
Claim 9
Dependent Claim
95 words
A radio receiver processing an AM IF signal including a carrier signal and a modulating signal, comprising: a variable gain section amplifying said AM IF signal in response to a gain factor, for producing a modified AM IF signal; an adaptive narrow bandpass filter receiving said modified AM IF signal, for producing said carrier signal substantially without modulation sidebands; an averager coupled to said adaptive narrow bandpass filter receiving said carrier signal for producing a carrier strength signal; and a comparer comparing said carrier strength signal with a comparison signal to determine said gain factor.
Claim 10
Dependent Claim
95 words
A radio receiver processing an AM IF signal including a carrier signal and a modulating signal, comprising: a variable gain section amplifying said AM IF signal in response to a gain factor, for producing a modified AM IF signal; an adaptive narrow bandpass filter receiving said modified AM IF signal, for producing said carrier signal substantially without modulation sidebands; an averager coupled to said adaptive narrow bandpass filter receiving said carrier signal for producing a carrier strength signal; and a comparer comparing said carrier strength signal with a comparison signal to determine said gain factor.
Claim 11
Dependent Claim
28 words
The receiver of claim 8 further comprising a least-mean-square (LMS) controller for controlling said gain factor so as to maintain said carrier strength signal at a predetermined value.
Claim 12
Dependent Claim
32 words
The receiver of claim 8 further comprising a normalizer coupled to said averager for producing a normalized mixing signal by multiplying said carrier signal by the reciprocal of said carrier strength signal.
Claim 13
Dependent Claim
16 words
The receiver of claim 10 wherein said comparison signal is proportional to said normalized mixing signal.
References Cited (Backward Citations)
US2602885A
Cited
US3002088A
Cited
US3665321A
Cited
US3714622A
Cited
US3872387A
Cited
US4087756A
Cited
US4371981A
Cited
US4600890A
Cited
US4792992A
Cited
US4839905A
Cited
US4811423A
Cited
US4955078A
Cited
US4955077A
Cited
US4989074A
Cited
US5086437A
Cited
US5175883A
Cited
US5204977A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-11-06 | 1999-05-08 | 1999-11-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-11-06 | 2003-05-08 | 2003-11-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-11-06 | 2007-05-08 | 2007-11-07 | $7700.00 | Window Closed / Lapsed |