Telephonic communications – Echo cancellation or suppression – Residual echo cancellation
Reexamination Certificate
2006-03-28
2006-03-28
Harold, Jefferey (Department: 2646)
Telephonic communications
Echo cancellation or suppression
Residual echo cancellation
C379S406010, C379S406040, C379S406080
Reexamination Certificate
active
07020278
ABSTRACT:
A non-linear processor for use in an echo canceller is set forth. The non-linear processor includes a center clipping digital filter receiving an echo compensated signal. The non-linear processor provides a center clipped output signal having non-linear thresholds at values of +TNLPand −TNLP. The value of TNLPis dynamically dependent, at least in part, on echo return loss measurements. To limit the processor's susceptibility to corruption from double-talk conditions, the non-linear processor inhibits the dynamic setting of the TNLPvalue when a double-talk condition is present. Additionally, or in the alternative, the non-linear processor locks the value of the echo return loss measurement after a predetermined number of consecutive echo return loss measurements have values falling within a predetermined range of one another. Such locking further reduces the susceptibility of the non-linear processor to corruption from double-talk conditions.
REFERENCES:
patent: 4679230 (1987-07-01), Lassaux et al.
patent: 6466666 (2002-10-01), Eriksson
patent: 6516063 (2003-02-01), Farrell et al.
Farrell David S.
Liu Tianfang
Fernandez Cheryl M.
Harold Jefferey
Tellabs Law Department
Tellabs Operations Inc.
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