US 6516063

Patent Overview: US 6,516,063 B1

Title: Echo canceller having improved non-linear processor

Patent number: US 6,516,063 B1

Inventors: David S. Farrell; Tianfang Liu

Original assignee: Tellabs Operations Inc. (current assignee listed as Coriant Operations Inc.)

Application number: US09/535,305

Priority date: 1997-11-14

Filing date: 2000-03-24

Publication (grant) date: 2003-02-04

Legal status: Expired – Lifetime (anticipated expiration 2017-11-14)

Classification: H04B3/23 (echo cancellers using a replica of the transmitted signal in the time domain); H04B3/234 (double-talk detection); H04M9/082 (loud-speaking telephone systems using echo cancellers)

Purpose. The patent relates generally to echo cancellation and, more specifically, to an echo canceller including an improved non-linear processor with adaptive thresholding. Echo cancellers monitor the receive channel of a four-wire circuit, generate estimates of expected echoes, and subtract those estimates from the transmit channel. Conventional adaptive cancellers are described as susceptible to sub-optimal performance during "double talk" (both parties speaking concurrently) and to non-linear echo paths. The present inventors recognized that a dual-H architecture — a non-adaptive filter h combined with an adaptive filter — may itself assist in detecting a non-linear echo path.

Plain-language scope. A non-linear processor includes a center-clipping digital filter receiving an echo-compensated signal and producing a center-clipped output with non-linear thresholds at +T_NLP and −T_NLP. The value of T_NLP is dynamically dependent, at least in part, on echo return loss measurements. Dynamic setting of T_NLP is inhibited when double talk is present, and the echo return loss measurement is locked after a predetermined number of consecutive measurements fall within a predetermined range of one another, reducing susceptibility to corruption from double-talk conditions.

Source: https://patents.google.com/patent/US6516063/en

What the excerpt does not establish. The supplied text is excerpted; the detailed description, some drawing descriptions, and the claims are omitted. It therefore does not establish the full claim scope, the complete mathematical formulations (equations appear incomplete), or the specific implementation details of the filters S, M, and L and other figures.