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Digital adaptive filter and acoustic echo canceller using the same

An adaptive filter, filter technology, applied in the direction of adaptive network, digital technology network, two-way sound reinforcement telephone system, etc.

Inactive Publication Date: 2005-03-16
TELEFON AB LM ERICSSON (PUBL)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

therefore, figure 2 The usual approach shown in , achieves only limited convergence of the adaptive filter with an associated negative impact on communication quality

Method used

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  • Digital adaptive filter and acoustic echo canceller using the same
  • Digital adaptive filter and acoustic echo canceller using the same
  • Digital adaptive filter and acoustic echo canceller using the same

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Experimental program
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Embodiment Construction

[0042] image 3 The basic concepts for implementing different embodiments of the invention are shown, namely, for example, asymmetric estimation of input signal power levels. exist image 3 Only the loudspeaker 10 and the microphone 12 are shown, for example, for use in a hands-free duplex communication device.

[0043] image 3 The transmission conditions along the path between loudspeaker 10 and microphone 12 are shown. If the loudspeaker outputs a short period signal 14 propagating along the echo path 16, the associated signal received by the microphone 12 will be a longer duration echo signal. The same holds true for the envelope 20 of the loudspeaker output signal 14 and the envelope 22 of the echo signal 18 .

[0044] Such as image 3 As shown in , typically the envelope 20 of the loudspeaker signal 14 has approximately the same duration as the rise and fall of the power level. In contrast, with respect to the echo signal 18, it should be noted that initially the p...

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PUM

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Abstract

In order to achieve improved convergence for, for example, echo cancellation, there is provided a digital adaptive filter comprising: filter coefficient updating means (52; 78) for depending on an input signal (X), the input signal The estimated power (PI) of , and the error signal between the input signal filtered in the digital adaptive filter and the input signal propagating along the external path (16) simulated by the digital adaptive filter constantly updates the filter coefficients . Here, input signal power estimating means (50, 84-92) are adapted to perform recursive smoothing with different smoothing factors in an asymmetric manner for increasing input power and decreasing input power. If the estimation is done in the frequency domain, the step size for updating the filter coefficients can be selectively adapted to the frequency band.

Description

technical field [0001] This invention relates to digital adaptive filters and acoustic echo cancellers utilizing such devices. [0002] In particular, the invention relates to digital adaptive filters, wherein the adaptation process is carried out according to the normalized least squares error algorithm NLMS of the error signal. Background technique [0003] In particular, the increasing demand for hands-free type communication systems has led to continuous efforts to develop acoustic echo cancellers. Such acoustic echo cancellers require efficient filtering techniques with low contention load and delay. [0004] As is generally known, for example, the use of a mobile phone in a vehicle during driving greatly reduces the driver's concentration and increases the risk of accidents. Here, the hands-free device allows the driver to concentrate on the traffic and increases safety. One reason why such hands-free devices are not widely used is due to the poor quality of the sys...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H21/00H04B3/23H04M9/08
CPCH04B3/23H03H2021/0041H04M9/082Y02D30/70H03H17/0227
Inventor W·阿姆布吕斯特尔
Owner TELEFON AB LM ERICSSON (PUBL)