Invalidity dossier
US 5668865
Added 9/23/2026, 12:38:49 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,668,865
Title: Echo canceler E-side speech detector
Patent number: US5668865A
Application number: US08/606,934
Inventors: Donald Lars Duttweiler, Cheng Kim, Ying Get Tao
Original assignee: Lucent Technologies Inc.
Current assignee (as listed): Nokia of America Corp
Priority/filing date: 1996-02-26 (application filed and priority claimed)
Publication/grant date: 1997-09-16
Legal status (as listed): Expired – Lifetime; anticipated expiration 2016-02-26
Classification: H04B3/23 (echo cancellers using a replica of the transmitted signal in the time domain)
Purpose and plain-language scope
Echoes arise from impedance mismatches, such as at a four-wire/two-wire hybrid junction, and annoy the originating talker when echo-path delay is significant. An echo canceler synthesizes an estimate of the echo and subtracts it from the outgoing signal. A Near End Speech (NES) detector decides whether the incoming signal is echo or actual near-end speech, and inhibits filter adaptation when near-end speech is present so the filter is not mis-trained.
The invention improves this by using two NES determinations. A coarse detector indicates whether the near-end signal y(k) contains speech. An E-side detector then processes x(k) and e(k)—using a representation of far-end speech level (the buffered maximum magnitude, x_max(k)) and a threshold value—to identify more accurately when the near-end signal is pure echo. If the near-end magnitude exceeds echo-only expectations and no near-end speech is indicated, the threshold is adjusted in one direction; otherwise, in the other, "finely tuning" echo detection. The final E-side NES indication, held for a hangover interval, inhibits adaptive filter 206-1 adaptation.
Source: https://patents.google.com/patent/US5668865/en
What the excerpt does not establish: The supplied text is incomplete (it truncates in the FIG. 3 program description) and contains OCR artifacts, including malformed equations; the full claims are not reproduced. It therefore does not establish complete claim language, all numerical parameters, or the full implementation details.
Generated 10/1/2026, 9:53:31 PM
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Assignment history
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Prior art
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