US6687723B1
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Tri-mode adaptive filter and method
Assignee: Ciena Luxembourg SARL
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Filing: 2000-11-24
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Granted: 2004-02-03
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Expires: 2020-11-24
Abstract
Abstract An adaptive filter having a hybrid structure and capable of operating in a tri-mode regime is disclosed. The tri-mode adaptive filter includes three sub-filters which operate in a fast convergence mode, a slow convergence mode, and a freezing mode respectively. The adaptive filter further comprises a quality detector which measures non-convergence and a near-end signal of the tri-mode filter and generates a feedback signal which is sent to a switching means. In response to the feedback signal, the switching means provides switching between the sub-filters so that one of the sub-filters operates at a time, providing adaptive filtering in accordance with its corresponding filtering method. In the embodiment of the invention the sub-filters operating in fast, slow and freezing mode are represented by Conjugate Gradient Fast Affine Projection (CGFAP) adaptive filter, Normalized Least Mean Square (NLMS) adaptive filter and Freezing adaptive filter respectively, wherein the Freezing filter operates with constant adaptive filter coefficients, i.e. without updating the filter coefficients, thereby providing convolution without adaptation. Corresponding method of adaptive filtering is also provided.
Inventors
- 👤 Heping Ding
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 11:25
CPC Classifications
H; H03; H03H; H03H21/00; H03H21/0012; H03H2021/0085; H03H2021/0089
Claims Analysis
Total Claims: 37
Claim 1
Independent Claim
69 words
A method of adaptive filtering, comprising the steps of: providing operation of an adaptive filter in one of three modes, the modes being a fast converging mode, a slow converging mode and a freezing mode; measuring non-convergence of the filter and a near-end signal, and generating a feedback signal based on the measurements; and switching between the modes of operation of the filter in response to the feedback signal.
Claim 2
Independent Claim
69 words
A method of adaptive filtering, comprising the steps of: providing operation of an adaptive filter in one of three modes, the modes being a fast converging mode, a slow converging mode and a freezing mode; measuring non-convergence of the filter and a near-end signal, and generating a feedback signal based on the measurements; and switching between the modes of operation of the filter in response to the feedback signal.
Claim 3
Dependent Claim
26 words
A method as defined in claim 1 , wherein the step of measuring non-convergence and near-end signal comprises comparing the measured values with pre-determined threshold values.
Claim 4
Dependent Claim
50 words
A method as defined in claim 2 , wherein the step of switching between the modes of operation of the filter comprises providing operation of the adaptive filter in the freezing mode when the near-end signal is above the corresponding threshold value and non-convergence is below the corresponding threshold value.
Claim 5
Dependent Claim
51 words
A method as defined in claim 2 , wherein the step of switching between the modes of operation of the filter comprises providing operation of the adaptive filter in the fast converging mode when non-convergence is above a corresponding threshold value and the near-end signal is below a corresponding threshold value.
Claim 6
Dependent Claim
44 words
A method as defined in claim 2 , wherein the step of switching between the modes of operation of the filter comprises providing operation of the adaptive filter in the slow converging mode when non-convergence and near-end signal are both below corresponding threshold values.
Claim 7
Dependent Claim
44 words
A method as defined in claim 2 , wherein the step of switching between the modes of operation of the filter comprises providing operation of the adaptive filter in the fast converging mode when non-convergence and near-end signal are both above corresponding threshold values.
Claim 8
Dependent Claim
44 words
A method as defined in claim 2 , wherein the step of switching between the mode of operation of the filter comprises providing operation of the adaptive filter in the slow converging mode when non-convergence and near-end signal are both above corresponding threshold values.
Claim 9
Dependent Claim
43 words
A method as defined in claim 2 , wherein the step of switching between the modes of operation of the filter comprises providing operation of the adaptive filter in the freezing mode when non-convergence and near-end signal are both above corresponding threshold values.
Claim 10
Independent Claim
38 words
A method as defined in claims 1 to 8 , wherein the step of providing operation of the filter in the slow converging mode comprises providing adaptive filtering in accordance with a normalized least mean square (NLMS) method.
Claim 11
Independent Claim
37 words
A method as defined in claims 1 to 8 , wherein the step of providing operation of the filter in the fast converging mode comprises providing adaptive filtering in accordance with a fast affine projection (FAP) method.
Claim 12
Independent Claim
38 words
A method as defined in claims 1 to 8 , wherein the step of providing operation of the filter in the fast converging mode comprises providing adaptive filtering in accordance with a stable fast affine projection (SFAP) method.
Claim 13
Dependent Claim
24 words
A method as defined in claim 11 , wherein the adaptive filtering in accordance with the SFAP method comprises using a steepest descent method.
Claim 14
Dependent Claim
24 words
A method as defined in claim 11 , wherein the adaptive filtering in accordance with the SFAP method comprises using a conjugate gradient method.
Claim 15
Independent Claim
146 words
A method of adaptive filtering, comprising the steps of: (a) providing initial adaptive filtering for an incoming signal, by one of a fast convering mode, a slow converging mode and a freezing mode; (b) measuring non-convergence and a near-end signal; (c) comparing the measured values of non-convergence and near-end signal with pre-determined threshold values; (d) when the near-end signal is above the corresponding threshold value and the non-convergence is below the corresponding threshold value, freezing coefficients in the currently used adaptive filtering mode; (e) when non-convergence is above the corresponding threshold value and the near-end signal is below the corresponding threshold value, providing adaptive filtering in accordance with a fast converging adaptive filtering mode; (f) when non-convergence and near-end signal are both below the corresponding threshold values, providing adaptive filtering in accordance with a slow converging adaptive filtering mode; and (g) repeating steps (b) to (f).
Claim 16
Independent Claim
146 words
A method of adaptive filtering, comprising the steps of: (a) providing initial adaptive filtering for an incoming signal, by one of a fast convering mode, a slow converging mode and a freezing mode; (b) measuring non-convergence and a near-end signal; (c) comparing the measured values of non-convergence and near-end signal with pre-determined threshold values; (d) when the near-end signal is above the corresponding threshold value and the non-convergence is below the corresponding threshold value, freezing coefficients in the currently used adaptive filtering mode; (e) when non-convergence is above the corresponding threshold value and the near-end signal is below the corresponding threshold value, providing adaptive filtering in accordance with a fast converging adaptive filtering mode; (f) when non-convergence and near-end signal are both below the corresponding threshold values, providing adaptive filtering in accordance with a slow converging adaptive filtering mode; and (g) repeating steps (b) to (f).
Claim 17
Dependent Claim
43 words
A method as defined in claim 14 , comprising the additional step of providing adaptive filtering in accordance with a fast converging mode when non-convergence and near-end signal are both above the corresponding threshold values, the step being performed before the step (g).
Claim 18
Dependent Claim
43 words
A method as defined in claim 14 , comprising the additional step of providing adaptive filtering in accordance with a slow converging mode when non-convergence and near-end signal are both above the corresponding threshold values, the step being performed before the step (g).
Claim 19
Dependent Claim
42 words
A method as defined in claim 14 , comprising the additional step of freezing coefficients in the currently used adaptive filtering mode when non-convergence and near-end signal are both above the corresponding threshold values, the step being performed before the step (g).
Claim 20
Independent Claim
39 words
A method as defined in claims 14 to 17 wherein the step of providing adaptive filtering in accordance with the slow converging adaptive filtering mode comprises providing adaptive filtering in accordance with a normalized least mean square (NLS) method.
Claim 21
Independent Claim
38 words
A method as defined in claims 14 to 17 wherein the step of providing adaptive filtering in accordance with the fast converging adaptive filtering mode comprises providing adaptive filtering in accordance with a fast affine projection (FAP) method.
Claim 22
Independent Claim
39 words
A method as defined in claims 14 to 17 wherein the step of providing adaptive filtering in accordance with the fast converging adaptive filtering mode comprises providing adaptive filtering in accordance with a stable fast affine projection (SFAP) method.
Claim 23
Dependent Claim
23 words
A method as defined in claim 20 wherein the adaptive filtering in accordance with the SFAP method comprises using a steepest descent method.
Claim 24
Dependent Claim
23 words
A method as defined in claim 20 wherein the adaptive filtering in accordance with the SFAP method comprises using a conjugate gradient method.
Claim 25
Dependent Claim
65 words
An adaptive filter, comprising: means for providing operation of the adaptive filter in one of the three modes, the modes including fast converging mode, slow converging mode, and a freezing mode; means for measuring non-convergence of the filter and a near-end signal, and generating a feedback signal; and means for switching between the modes of operation of the filter in response to the feedback signal.
Claim 26
Dependent Claim
65 words
An adaptive filter, comprising: means for providing operation of the adaptive filter in one of the three modes, the modes including fast converging mode, slow converging mode, and a freezing mode; means for measuring non-convergence of the filter and a near-end signal, and generating a feedback signal; and means for switching between the modes of operation of the filter in response to the feedback signal.
Claim 27
Dependent Claim
44 words
An adaptive filter as defined in claim 23 , wherein the means for providing operation of the adaptive filter in one of the three modes comprises first, second and third sub-filters which operate in fast converging mode, slow converging mode and freezing mode respectively.
Claim 28
Dependent Claim
21 words
An adaptive filter as defined in claim 24 , wherein the first sub filter comprises a fast affine projection (FAP) filter.
Claim 29
Dependent Claim
21 words
An adaptive filter as defined in claim 24 , wherein the first sub-filter comprises a stable fast affine projection (SFAP) filter.
Claim 30
Dependent Claim
18 words
An adaptive filter as defined in claim 26 , wherein the SFAP filter comprises a steepest descent calculator.
Claim 31
Dependent Claim
18 words
An adaptive filter as defined in claim 26 , wherein the SFAP filter comprises a conjugate gradient calculator.
Claim 32
Dependent Claim
21 words
An adaptive filter as defined in claim 24 , wherein the second sub-filter comprises a normalized least mean square (NLMS) filter.
Claim 33
Dependent Claim
27 words
An adaptive filter as defined in claim 24 , wherein the third sub-filter comprises a filter which operates without updating the filter coefficients, thereby providing convolution only.
Claim 34
Dependent Claim
28 words
An adaptive filter as defined in claim 23 , wherein the means for measuring non-convergence and near-end signal comprises means for comparing measured values with pre-determined threshold values.
Claim 35
Dependent Claim
55 words
An adaptive filter according to claim 23 wherein the means for measuring non-convergence and near end signal comprises a quality detector which identifies presence of non-convergence (NC) and near end signal (NS), distinguishes between them, and compares the measured values with pre-determined threshold values, NC threshold and NS threshold, respectively, to generate the feedback signal.
Claim 36
Dependent Claim
176 words
An adaptive filter, comprising: first, second and third sub-filters, operable respectively in a fast convergence mode, a slow convergence mode, and a freezing mode; a quality detector for measuring non-convergence and a near end signal, comparing the non-convergence to a non-convergence threshold value and comparing the near end signal to a near end signal threshold value, and generating a feedback signal; a switching means responsive to the feedback signal to provide switching between sub-filters; when the non-convergence is above the corresponding threshold value and the near end signal is below the corresponding threshold value, switching to the fast converging mode; when the near end signal is above the corresponding threshold value and the non convergence is below the corresponding threshold value switching to the freezing mode; when the non-convergence and near end signal are both below the corresponding threshold values, switching to the slow converging mode; and when both the non-convergence and the near end signal are above the corresponding threshold values, operating the filter in any one of the sub-filters modes according to system requirements.
Claim 37
Dependent Claim
176 words
An adaptive filter, comprising: first, second and third sub-filters, operable respectively in a fast convergence mode, a slow convergence mode, and a freezing mode; a quality detector for measuring non-convergence and a near end signal, comparing the non-convergence to a non-convergence threshold value and comparing the near end signal to a near end signal threshold value, and generating a feedback signal; a switching means responsive to the feedback signal to provide switching between sub-filters; when the non-convergence is above the corresponding threshold value and the near end signal is below the corresponding threshold value, switching to the fast converging mode; when the near end signal is above the corresponding threshold value and the non convergence is below the corresponding threshold value switching to the freezing mode; when the non-convergence and near end signal are both below the corresponding threshold values, switching to the slow converging mode; and when both the non-convergence and the near end signal are above the corresponding threshold values, operating the filter in any one of the sub-filters modes according to system requirements.
References Cited (Backward Citations)
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