Digital adaptive filter and acoustic echo canceller using the same
Digital adaptive filter and acoustic echo canceller using the same
 CN 100,531,274 C
 Filed: 07/01/1999
 Issued: 08/19/2009
 Est. Priority Date: 07/13/1998
 Status: Active Grant
First Claim
1. digital adaptive filter, it is used for simulating the signal path between handsfree type communication equipment loud speaker and the microphone, and this filter comprises:
 The filter coefficient update device, in order to by the estimative power of input signal, this input signal and in this digital adaptive filter filtered input signal and bring in constant renewal in filter coefficient along the error signal between the input signal of propagating by the external path of this digital adaptive filter simulation;
WithThe input signal power estimation unit, be used for by the input signal power level of the input signal power level that increases and minimizing is come that with different weighting factors the input power of the input power that increases and/or minimizing is carried out asymmetric recursion smoothly, wherein to press following formula level and smooth to input power implementation recursion for this input signal power estimation unit;
PI _{t}＝
β
·
Pin _{t}+(1β
)·
PI _{t1}
Chinese PRB Reexamination
Abstract
To achieve an improved convergence behaviour for, e.g., echo cancellation there is provided a digital adaptive filter comprising a filter coefficient update means (52;78) to successively update filter coefficience in accordance with an input signal (x), an estimated power (PI) of the input signal, and an error signal between the input signal filtered in the digital adaptive filter and the input signal propagated along an external path (16) being modelled by the digital adaptive filter. Here, an input signal power estimation means (50,84 to 92) is adapted to perform recursive smoothing for an increasing input power and a decreasing input power in an asymmetric fashion with different smoothing factors. In case the estimation is carried out in the frequency domain the step size for the update of filter coefficients may be adapted frequency band selectively.
8 Claims

1. digital adaptive filter, it is used for simulating the signal path between handsfree type communication equipment loud speaker and the microphone, and this filter comprises:

The filter coefficient update device, in order to by the estimative power of input signal, this input signal and in this digital adaptive filter filtered input signal and bring in constant renewal in filter coefficient along the error signal between the input signal of propagating by the external path of this digital adaptive filter simulation;
WithThe input signal power estimation unit, be used for by the input signal power level of the input signal power level that increases and minimizing is come that with different weighting factors the input power of the input power that increases and/or minimizing is carried out asymmetric recursion smoothly, wherein to press following formula level and smooth to input power implementation recursion for this input signal power estimation unit; PI _{t}＝
β
·
Pin _{t}+(1β
)·
PI _{t1}


2. according to the digital adaptive filter of claim 1, it is level and smooth to it is characterized in that the input signal power estimation unit is carried out recursion to input power by following formula in timedomain:
PX _{n}＝
β
·
x(n)·
x(n)+(1β
)·
PX _{n1}

3. according to the digital adaptive filter of claim 1, it is level and smooth to it is characterized in that the input signal power estimation unit is carried out recursion to input power by following formula in frequency domain:

4. according to the digital adaptive filter of claim 3, it is characterized in that the filter coefficient update device is adapted to the backgroundnoise level according to frequency band, calculates step pitch individually at least one frequency band.

5. digital adaptation filtering method, it is used for simulating the signal path between handsfree type communication equipment loud speaker and the microphone, and this method may further comprise the steps:

By the estimative power of input signal, this input signal and in this digital adaptive filter filtered input signal and bring in constant renewal in filter coefficient along the error signal between the input signal of propagating by the external path of this digital adaptive filter simulation;
WithLevel and smooth by the input signal power level of the input signal power level that increases and minimizing is come that with different weighting factors the input power of the input power that increases and/or minimizing is carried out asymmetric recursion, it is level and smooth to input power implementation recursion wherein to press following formula; PI _{t}＝
β
·
Pin _{t}+(1β
)·
PI _{t1}


6. according to the digital adaptation filtering method of claim 5, it is level and smooth to it is characterized in that in timedomain input power being carried out recursion by following formula:
PX _{n}＝
β
·
x(n)·
x(n)+(1β
)·
PX _{n1}

7. according to the digital adaptation filtering method of claim 5, it is level and smooth to it is characterized in that in frequency domain input power being carried out recursion by following formula:

8. according to the digital adaptation filtering method of claim 7, it is characterized in that backgroundnoise level, calculate step pitch individually at least one frequency band according to frequency band.
Specification(s)