Patent
Adaptive echo-canceller with double-talker detection
Kannan P. Vairavan,Mcleod Paul +1 more
TLDR
In this paper, a double-talker detector is used in conjunction with the echo-canceller to detect near-end speech or signal, which is detected if the latter signal exceeds a predetermined function of the former signal.Abstract:
Method and apparatus are disclosed which provide echo-cancellation in subscriber line audio-processing circuits (SLACs) and modulator-demodulators (modems). The echo-canceller provides a response independent of the amplitude of an error signal representing the difference between the desired and generated signal. The convergence of the echo-cancelling is not influenced by the size of the error signal but only by its sign. In a preferred embodiment, a cannonic signed digit filter coefficient updating technique is used for a digital filter (10) implementing the echo-cancellation function. A double-talker detector is advantageously used in conjunction with the echo-canceller. Detection of "double-talker" near-end signals inhibits updating of the echo-canceller filter coefficients. Near-end signals are detected by an energy-averaging filter (26) which selectively samples (28) low-pass filtered signals received by the adaptive filter as received from the far-end talker and low-pass filtered signals received from the near-end talker. Near-end speech or signal is detected if the latter signal exceeds a predetermined function of the former signal.read more
Citations
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References
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Journal ArticleDOI
Digital echo cancellation for baseband data transmission
TL;DR: An integrated circuit realized in 4Φ-dynamic NMOS technology is presented which has been designed especially for echo cancellation in baseband modems and can pave the way to the use of similar circuits in the local area of the future digital telephone.
Patent
Method and apparatus for improved control and time sharing of an echo canceller
TL;DR: In this article, an improved echo cancellation control method utilizes two adaptive level detectors for controlling or inhibiting the updating of coefficients in the echo canceller, where the coefficients are separately stored in association with each channel as is the case in this invention.
Patent
Adaptive low pass filter
TL;DR: In this article, an adaptive low-pass recursive filter adaptively changes its bandwidth filtering characteristics in accordance with the bandwidth of the incoming signal, which results in an input signal w(k) changed into output signal x(k), in according with the equation where k is a sampling interval and a is the adaptive value representing ratio of known noise power to average error between the filter input and output.
Patent
Echo canceller with variable threshold
TL;DR: In this paper, a digital transversal filter with adjustable gain coefficients and an adaptive control loop is used to achieve minimum echo and similar speed of convergence for loud and soft talkers.