US4633485A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Adaptive noise suppression for digital modems
Assignee: Xylon LLC
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Filing: 1985-03-08
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Granted: 1986-12-30
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Expires: 2005-03-08
Abstract
Abstract This invention provides a receiver for a QAM modem with a phase tracking loop for eliminating phase errors due to phase jitter and frequency offset. The instantaneous phase error of the received signal is monitored and if it is below a certain preselected value, indicating the presence of white noise, the gain of the phase tracking loop is reduced.
Inventors
- 👤 William L. Betts
- 👤 Edward Zuranski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:23
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/32; H04L27/34; H04L27/38; H04L27/3818
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
150 words
In the receiver section of a modem for receiving quadrature amplitude modulated (QAM) signals, a phase tracking loop comprising: coordinate rotation means for rotating said QAM signals to form rotated QAM signals by an average phase error signal; demodulator and complex reference number selector means for demodulating said rotated QAM signals and for selecting complex reference numbers corresponding to said rotated QAM signals; instantaneous phase error signal generating means for generating an instantaneous phase error signal corresponding to said rotated QAM signals and said complex reference numbers; multiplying means for multiplying said instantaneous phase error signal by a gain signal to produce a multiplied error signal; means for generating a corrected error signal by averaging said multiplied error signal; means for generating said gain signal including a comparator for comparing the corrected phase error signal to a preselected threshold value for varying said gain in accordance with said threshold; and
Claim 2
Dependent Claim
150 words
In the receiver section of a modem for receiving quadrature amplitude modulated (QAM) signals, a phase tracking loop comprising: coordinate rotation means for rotating said QAM signals to form rotated QAM signals by an average phase error signal; demodulator and complex reference number selector means for demodulating said rotated QAM signals and for selecting complex reference numbers corresponding to said rotated QAM signals; instantaneous phase error signal generating means for generating an instantaneous phase error signal corresponding to said rotated QAM signals and said complex reference numbers; multiplying means for multiplying said instantaneous phase error signal by a gain signal to produce a multiplied error signal; means for generating a corrected error signal by averaging said multiplied error signal; means for generating said gain signal including a comparator for comparing the corrected phase error signal to a preselected threshold value for varying said gain in accordance with said threshold; and
Claim 3
Dependent Claim
15 words
averaging means of averaging said corrected error signal to generate said average phase error signal.
Claim 4
Dependent Claim
15 words
averaging means of averaging said corrected error signal to generate said average phase error signal.
Claim 5
Dependent Claim
62 words
The phase tracking loop of claim 1 wherein said multiplying means comprises a first multiplier for multiplying said instantaneous phase error signal with a first preselected constant, a second multiplier for multiplying said instantaneous phase error signal with a second preselected constant and means for selecting one of said first and second multiplier outputs in accordance with the output of said comparator.
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) | 1989-12-29 | 1990-06-30 | 1990-12-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-12-29 | 1994-06-30 | 1994-12-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-12-29 | 1998-06-30 | 1998-12-30 | $7700.00 | Window Closed / Lapsed |