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Patent US4449102A successfully refreshed from Google Patents.
US4449102A
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Adaptive threshold circuit
Assignee: AT&T Inc
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Filing: 1982-03-15
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Granted: 1984-05-15
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Expires: 2002-03-15
Abstract
Abstract The adaptive threshold circuit (FIG. 1) senses the amplitude of a digital signal relative to a threshold and generates a corresponding output signal therefrom. Feedback circuitry generates a correction signal which drives the threshold toward a predetermined level in the signal-eye pattern. This predetermined level passes only through the region of intersymbol interferene in the signal-eye pattern.
Inventors
- 👤 Gerald L. Frazer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 02:33
CPC Classifications
H; H04; H04L; H04L25/00; H04L25/02; H04L25/06; H04L25/061; H04L25/063; H04L1/00; H04L1/20; H04L25/066
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
97 words
Apparatus for use in a digital transmission system wherein the digital signal forms at least one reoccurring signal-eye surrounded by a region of intersymbol interference in the voltage-time domain, said apparatus being characterized by means (e.g., 102, 105) for sensing the amplitude of the digital signal relative to a threshold at discrete times which coincide with said signal-eye; and means (e.g., 108, 110, 114) responsive to the sensed amplitude for generating a correction signal which drives said threshold solely toward a predetermined level relative to said signal-eye, said level passing only through said region of intersymbol interference.
Claim 2
Dependent Claim
97 words
Apparatus for use in a digital transmission system wherein the digital signal forms at least one reoccurring signal-eye surrounded by a region of intersymbol interference in the voltage-time domain, said apparatus being characterized by means (e.g., 102, 105) for sensing the amplitude of the digital signal relative to a threshold at discrete times which coincide with said signal-eye; and means (e.g., 108, 110, 114) responsive to the sensed amplitude for generating a correction signal which drives said threshold solely toward a predetermined level relative to said signal-eye, said level passing only through said region of intersymbol interference.
Claim 3
Dependent Claim
31 words
The apparatus of claim 1 wherein said predetermined level passes through a location (e.g., 404, 405, 406, or 407) in said region of intersymbol interference corresponding to a point of convergence.
Claim 4
Independent Claim
19 words
The apparatus of claims 1 or 2 wherein the discrete times coincide with the times of maximum signal-eye opening.
Claim 5
Dependent Claim
31 words
The apparatus of claim 1 wherein said sensing means generates an output signal having either a first (e.g., logic "1") or a second (e.g., logic "0") state at said discrete times.
Claim 6
Dependent Claim
56 words
The apparatus of claim 4 wherein said correction signal generating means divides the number of said first states by qx+p and divides the discrete times by qn where x is the number of signal levels above said predetermined level, n is the total number of digital signal levels and p/q is a rational fraction where 0<p/q<1.
Claim 7
Dependent Claim
9 words
The apparatus of claim 5 wherein p/q equals 1/2.
Claim 8
Dependent Claim
17 words
The apparatus of claim 6 wherein the discrete times coincide with the times of maximum signal-eye opening.
Claim 9
Dependent Claim
56 words
The apparatus of claim 4 wherein said correction signal generating means divides the number of said second states by qx+p and divides the discrete times by qn where x is the number of signal levels below said predetermined level, n is the total number of digital signal levels and p/q is a rational fraction where 0<p/q<1.
Claim 10
Dependent Claim
9 words
The apparatus of claim 8 wherein p/q equals 1/2.
Claim 11
Dependent Claim
17 words
The apparatus of claim 9 wherein the discrete times coincide with the times of maximum signal-eye opening.
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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) | 1987-05-15 | 1987-11-14 | 1988-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-15 | 1991-11-14 | 1992-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-15 | 1995-11-14 | 1996-05-15 | $7700.00 | Window Closed / Lapsed |