US4453256A
Expired / Lapsed
US
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Adaptive equalizer system for quadrature amplitude modulation
Assignee: NEC Corp
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Filing: 1981-12-22
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Granted: 1984-06-05
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Expires: 2001-12-22
Abstract
Abstract An adaptive equalizer system for quadrature amplitude modulated waves is disclosed herein. The equalizer system comprises a circuit for equalizing the received signal as a function of a composite control signal; a circuit for generating a first control signal as a function of the deviation of the equalized signal from a zero-forced waveform; a circuit for generating a second control signal as a function of the asynchronization of the equalizer system; and an output circuit for processing both of said first control signal and said second control signal, producing the composite control signal which controls the equalizing means of the equalizer system.
Inventors
- 👤 Toshihiko Ryu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 14:56
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/01; G; G06; G06G; G06G7/00; G06G7/12; G06G7/18; G06G7/184; G06G7/186; G06G7/1865
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
84 words
An adaptive equalizer system having a control loop comprising; first means for equalizing a modulated carrier wave in response to a first control signal; second means including analogue integrator means for generating said first control signal from the output of said first means, said analogue integrator means forming a self-feedback loop in response to a second control signal and setting said first control signal at a fixed level; and third means for detecting asynchronization in said control loop and providing said second control signal.
Claim 2
Dependent Claim
84 words
An adaptive equalizer system having a control loop comprising; first means for equalizing a modulated carrier wave in response to a first control signal; second means including analogue integrator means for generating said first control signal from the output of said first means, said analogue integrator means forming a self-feedback loop in response to a second control signal and setting said first control signal at a fixed level; and third means for detecting asynchronization in said control loop and providing said second control signal.
Claim 3
Dependent Claim
32 words
The adaptive equalizer system of claim 1, wherein said first means comprises a transversal filter including a delay circuit, a main tap and another tap, which operates in the intermediate frequency band.
Claim 4
Dependent Claim
45 words
The adaptive equalizer system of claim 2, wherein said transversal filter is controlled by means of zero-forcing equalizing algorithm so that the phase difference in said modulated carrier wave between said main tap and said another tap is in the range of -90° to +90°.
Claim 5
Dependent Claim
41 words
The adaptive equalizer system of claim 2, wherein the delay time of said delay circuit is neither the inverse of the modulation rate of said modulated carrier wave nor the inverse of twice the modulation rate of said modulated carrier wave.
Claim 6
Dependent Claim
29 words
The adaptive equalizer system of claim 1, wherein said second means comprises a decision circuit/error signal generator including a DC coupling decision circuit and an AC coupling decision circuit.
Claim 7
Dependent Claim
19 words
The adaptive equalizer system of claim 1, wherein said modulated carrier wave comprises a quadrature amplitude modulated carrier wave.
Claim 8
Dependent Claim
17 words
The adaptive equalizer system of claim 1, wherein said self-feedback loop comprises a plurality of logic circuits.
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) | 1987-06-05 | 1987-12-05 | 1988-06-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-06-05 | 1991-12-05 | 1992-06-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-06-05 | 1995-12-05 | 1996-06-05 | $7700.00 | Window Closed / Lapsed |