US6327709B1
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for filtering interference and nonlinear distortions
Assignee: Arris Enterprises LLC
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Filing: 1998-12-22
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Granted: 2001-12-04
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Expires: 2018-12-22
Abstract
Abstract Interference and/or nonlinear distortions are reduced in a signal communicated from a transmitter to a receiver. To reduce interference, the transmitter is momentarily disrupted, during which time the receiver analyzes interference on the communication path to determine the frequency of at least one peak thereof. Information is communicated from the receiver to the transmitter identifying the frequencies of the interference peaks. Based on this information, the transmitter pre-distorts the signal to accentuate the signal magnitude at the identified frequencies. The pre-distorted signal is then communicated to the receiver, where it is filtered to attenuate the signal magnitude at the identified frequencies. An adaptive scheme periodically determines the interference peak frequencies. For nonlinear distortion cancellation (e.g., CSO/CTB), there is no need to disrupt the transmitter since the frequencies of the distortion are already known. Pre-distortion at the transmitter and filtering at the receiver are performed at the known, fixed frequencies.
Inventors
- 👤 Shlomo Ovadia
- 👤 Qin Zhang
- 👤 Mark Kolber
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 19:42
CPC Classifications
H; H04; H04N; H04N21/00; H04N21/20; H04N21/23; H04N21/238; H04N21/2383; H04L; H04L25/00; H04L25/02; H04L25/03; H04L25/03006; H04L25/03343; H04N21/40; H04N21/43; H04N21/438; H04N21/4382; H04N7/00; H04N7/10; H04N7/102; H04L2025/0335; H04L2025/03375; H04L2025/0342; H04L2025/03592; H04L2025/03745; H04L2025/03764; H04L2025/03777; H04L2025/03802; H04L2025/03808
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
114 words
A method for filtering a signal communicated from a transmitter to a receiver via a communication path to reduce interference, comprising the steps of: momentarily disrupting said transmitter from transmitting over said communication path; analyzing interference on said communication path at the receiver during the momentary disruption to determine the frequency of at least one interference peak; communicating information from the receiver to the transmitter identifying the frequency of the at least one interference peak; pre-distorting said signal at the transmitter to accentuate the signal magnitude at the identified frequency; communicating the pre-distorted signal to said receiver; and filtering the pre-distorted signal at said receiver to attenuate the signal magnitude at the identified frequency.
Claim 2
Independent Claim
114 words
A method for filtering a signal communicated from a transmitter to a receiver via a communication path to reduce interference, comprising the steps of: momentarily disrupting said transmitter from transmitting over said communication path; analyzing interference on said communication path at the receiver during the momentary disruption to determine the frequency of at least one interference peak; communicating information from the receiver to the transmitter identifying the frequency of the at least one interference peak; pre-distorting said signal at the transmitter to accentuate the signal magnitude at the identified frequency; communicating the pre-distorted signal to said receiver; and filtering the pre-distorted signal at said receiver to attenuate the signal magnitude at the identified frequency.
Claim 3
Dependent Claim
28 words
A method in accordance with claim 1 wherein said analyzing step performs a real or complex signal frequency analysis on the interference to determine the frequency peak(s) thereof.
Claim 4
Dependent Claim
33 words
A method in accordance with claim 1 wherein said filtering at the receiver uses a transfer function that is the inverse of the transfer function used to pre-distort the signal at the transmitter.
Claim 5
Dependent Claim
79 words
A method in accordance with claim 1 wherein said filtering at the receiver uses the Z-transform transfer function: H ( z ) = 1 + 2 Re ( α ) z - 1 + z - 2 1 - 2 Re ( α ) R · z - 1 + R 2 · z - 2 where α=exp(2jπφ), φ is the normalized center frequency of the filter, and R is a constant.
Claim 6
Dependent Claim
21 words
A method in accordance with claim 4 wherein said pre-distortion at the transmitter implements the inverse transfer function H(z) −1 .
Claim 7
Dependent Claim
73 words
A method in accordance with claim 1 wherein: said transmitter is periodically disrupted from transmitting over said communication path; interference on said communication path is analyzed at the receiver during the periodic disruptions; information is communicated from the receiver to the transmitter identifying changes in the interference peak(s) determined during the periodic disruptions; and the transmitter pre-distorts the signal to accentuate the signal magnitude in accordance with the changes of the interference peaks.
Claim 8
Dependent Claim
26 words
A method in accordance with claim 1 wherein said analysis step identifies the frequency location(s) of the interference peak(s) in accordance with a power threshold level.
Claim 9
Dependent Claim
116 words
Apparatus for filtering interference in a signal communicated from a transmitter to a receiver via a communication path, said receiver comprising: a real or complex signal frequency analyzer adapted to analyze interference on the communication path during momentary disruptions of said signal to determine the frequency of at least one interference peak, and means for communicating information from the receiver to the transmitter identifying the frequency of the at least one interference peak; said transmitter comprising: a filter adapted to pre-distort said signal at the transmitter to accentuate the signal magnitude at the identified frequency; and said receiver further comprising: a filter adapted to attenuate the signal magnitude of the pre-distorted signal at the identified frequency.
Claim 10
Dependent Claim
116 words
Apparatus for filtering interference in a signal communicated from a transmitter to a receiver via a communication path, said receiver comprising: a real or complex signal frequency analyzer adapted to analyze interference on the communication path during momentary disruptions of said signal to determine the frequency of at least one interference peak, and means for communicating information from the receiver to the transmitter identifying the frequency of the at least one interference peak; said transmitter comprising: a filter adapted to pre-distort said signal at the transmitter to accentuate the signal magnitude at the identified frequency; and said receiver further comprising: a filter adapted to attenuate the signal magnitude of the pre-distorted signal at the identified frequency.
Claim 11
Dependent Claim
51 words
Apparatus in accordance with claim 8 wherein: said communication path comprises a cable television system return path coupling a subscriber location to a cable television system headend, said transmitter is provided at the subscriber location; said receiver is provided at the cable television system headend; and said interference comprises ingress noise.
Claim 12
Dependent Claim
19 words
Apparatus in accordance with claim 8 wherein: said transmitter communicates the pre-distorted signal to the receiver using digital modulation.
Claim 13
Dependent Claim
16 words
Apparatus in accordance with claim 8 wherein the filter at said receiver comprises a notch filter.
Claim 14
Dependent Claim
78 words
Apparatus in accordance with claim 11 wherein said notch filter has a Z-transform transfer function described by: H ( z ) = 1 + 2 Re ( α ) z - 1 + z - 2 1 - 2 Re ( α ) R · z - 1 + R 2 · z - 2 where α=exp(2jπφ), φ is the normalized center frequency of the filter, and R is a constant.
Claim 15
Dependent Claim
21 words
Apparatus in accordance with claim 12 wherein the pre-distortion filter at the transmitter implements the inverse transfer function H(z) −1 .
Claim 16
Dependent Claim
63 words
Apparatus in accordance with claim 13 wherein: said complex signal frequency analyzer periodically analyzes interference on the communication path during momentary disruptions of said signal to determine changes in the interference peak(s) over time, and said notch and pre-distortion filters are programmable to provide said signal attenuation and accentuation, respectively, at the interference peak(s) as the frequency of the peak(s) changes over time.
Claim 17
Dependent Claim
31 words
Apparatus in accordance with claim 8 wherein said complex signal frequency analyzer includes a threshold power level detector for use in determining the frequency of said at least one interference peak.
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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) | 2004-12-03 | 2005-06-04 | 2005-12-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-12-03 | 2009-06-04 | 2009-12-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-12-03 | 2013-06-04 | 2013-12-04 | $7700.00 | Window Closed / Lapsed |