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US3828147A
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Echo canceller arrangement comprising quasi-static echo cancellers and a smaller number of self-adaptive echo cancellers
Assignee: NEC Corp
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Filing: 1973-02-20
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Granted: 1974-08-06
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Expires: 1993-02-20
Abstract
Abstract An echo canceller arrangement for a plurality of channels comprises an equal plurality of quasi-static echo cancellers for the respective channels and a smaller number of self-adaptive echo cancellers which are coupled with a group of quasi-static echo cancellers for an equal smaller number of selected channels. Channel selection is successively varied in such a manner that various groups of all quasi-static echo cancellers are successively coupled with the self-adaptive echo cancellers. One of the echo path models retained by each self-adaptive echo canceller and by the quasi-static echo canceller coupled with the last-mentioned self-adaptive echo canceller is rewritten with reference to the other when the above-mentioned other model gives a significantly worse approximation of the characteristics of the concerned actual echo path than the above-mentioned one model.
Inventors
- 👤 K Ochiai
- 👤 T Araseki
- 👤 Y Kato
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 09:43
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
217 words
An echo canceller arrangement comprising: a self-adaptive echo canceller; a plurality of quasi-static echo cancellers each operatively associated with an equal plurality of channels, each channel having an echo path, each of said quasi-static echo cancellers having means for storing a first echo path model giving an approximation of the characteristics of the echo path of the associated channel, first means for selecting one of said channels and for operatively coupling said self-adaptive echo canceller with the quasi-static echo canceller associated with the selected channel, said self-adaptive echo canceller having means for storing a second echo path model giving an approximation of the characteristics of the echo path of said selected channel and further comprising means for self-adaptively improving the approximation stored in said second echo path model storing means with reference to the last-mentioned characteristics, and second means for comparing the residual echo signal approximations developed as a result of the echo path models stored in said self-adaptive echo canceller and said quasistatic echo canceller associated with said selected channel and for placing the echo path model in said self-adaptive echo canceller storing means into said quasi-static echo canceller storing Means only when the residual echo signal developed by said self-adaptive echo canceller is smaller than the residual echo signal developed by said quasi-static echo canceller.
Claim 2
Dependent Claim
217 words
An echo canceller arrangement comprising: a self-adaptive echo canceller; a plurality of quasi-static echo cancellers each operatively associated with an equal plurality of channels, each channel having an echo path, each of said quasi-static echo cancellers having means for storing a first echo path model giving an approximation of the characteristics of the echo path of the associated channel, first means for selecting one of said channels and for operatively coupling said self-adaptive echo canceller with the quasi-static echo canceller associated with the selected channel, said self-adaptive echo canceller having means for storing a second echo path model giving an approximation of the characteristics of the echo path of said selected channel and further comprising means for self-adaptively improving the approximation stored in said second echo path model storing means with reference to the last-mentioned characteristics, and second means for comparing the residual echo signal approximations developed as a result of the echo path models stored in said self-adaptive echo canceller and said quasistatic echo canceller associated with said selected channel and for placing the echo path model in said self-adaptive echo canceller storing means into said quasi-static echo canceller storing Means only when the residual echo signal developed by said self-adaptive echo canceller is smaller than the residual echo signal developed by said quasi-static echo canceller.
Claim 3
Dependent Claim
39 words
An echo canceller arrangement as claimed in claim 1, wherein said one of the echo path models is one of the first echo path models and said other of said echo path models is said second echo path model.
Claim 4
Dependent Claim
59 words
An echo canceller arrangement as claimed in claim 1, wherein said second means comprises non-logic means responsive to the coupling effected by said first means between one of said quasi-static echo cancellers and said self-adaptive echo canceller for substituting said second echo path model for said first echo path model retained by said one of said quasi-static echo cancellers.
Claim 5
Dependent Claim
102 words
An echo canceller arrangement as claimed in claim 1, wherein said second means comprises logic means responsive to the coupling effected by said first means between one of said quasi-static echo cancellers and said self-adaptive echo canceller and responsive to the echo path models retained by said one quasi-static echo canceller and by said self-adaptive echo canceller for replacing the first echo path model retained by said one quasi-static echo canceller with said second echo path model only when said second echo path model generates a smaller residual echo signal for the concerned actual echo path than said first echo path model.
Claim 6
Dependent Claim
43 words
An echo canceller arrangement as claimed in claim 1, wherein said first means comprises means for detecting presence and absence of double talk in each of said channels and means for selecting the channel in which absence of the double talk is detected.
Claim 7
Dependent Claim
88 words
An echo canceller arrangement as claimed in claim 1, said echo paths producing send-in signals, asid quasi-static echo cancellers producing residual echo signals, wherein said first means comprises monitoring means for monitoring the ratio of the level of the send-in signal in each of said channels to the level of the residual echo signal in said each channel to produce a modification request signal when said ratio is less than a predetermined threshold value and means for selecting the channel for which the modification request signal is produced.
Claim 8
Dependent Claim
68 words
An echo canceller arrangement as claimed in claim 6, wherein said monitoring means comprises comparator means responsive to a first short-time average of said send-in signal and a second short-time average of said residual echo signal of said each channel for producing said modification request signal when said first short-time average is greater than said second short-time average by a factor equal to the reciprocal of said ratio.
References Cited (Backward Citations)
US3754105A
Cited
US3647992A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-08-05 | 1978-02-04 | 1978-08-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-08-05 | 1982-02-04 | 1982-08-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-08-05 | 1986-02-04 | 1986-08-06 | $7700.00 | Window Closed / Lapsed |