Telephonic communications – Echo cancellation or suppression – Using digital signal processing
Reexamination Certificate
2005-08-02
2005-08-02
Mei, Xu (Department: 2644)
Telephonic communications
Echo cancellation or suppression
Using digital signal processing
C379S406080, C379S390020, C370S286000
Reexamination Certificate
active
06925177
ABSTRACT:
An echo canceler having a predictive filter that generates an echo replica signal and an adder that subtracts the echo replica signal from a send input signal also has a receive input amplifier and a clipping circuit. The clipping circuit clips the input to the predictive filter at a threshold level determined by increasing the receive input amplifier gain until distortion of the echo component causes echo cancellation performance to degrade. Alternatively, the echo canceler may have a send input amplifier, a send output amplifier, and an echo replica amplifier that amplifies the predicted echo replica signal. The gain of the send input amplifier is increased to determine the gain at which echo cancellation performance begins to deteriorate due to echo amplification, and the gain of the echo replica amplifier is set to compensate for the echo amplification.
REFERENCES:
patent: 4600815 (1986-07-01), Horna
patent: 5636323 (1997-06-01), Umemoto et al.
patent: 5796818 (1998-08-01), McClennon et al.
patent: 6173056 (2001-01-01), Romesburg et al.
Mei Xu
Oki Electric Industry Co. Ltd.
Rabin & Berdo P.C.
Swerdlow Daniel
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