Method and device for analysis of a return signal and adaptive echo canceller including application thereof

Claim 3

The method as claimed in claim 1, further comprising the step of recursively adapting the value of the detection threshold on the basis of the calculated values of said energy ratio, the adapting of the detection threshold being interrupted when it is determined that the return signal contains components other than the echo components of the forward signal.

Claim 4

The method as claimed in claim 2, wherein the adapting of the detection threshold is interrupted when presence of useful components is detected in the forward signal.

Claim 5

The method as claimed in claim 2, wherein, during each period of adapting of the detection threshold, the following steps are performed: calculating an average ρ av of the successively calculated energy ratios ρ by a recursive formula of the form ρ.sub.av =λρ.sub.av +(1-λ)ρ where λ designates a coefficient lying between 0 and 1; calculating a maximum value ρ max of the energy ratios ρ calculated during the periods of adapting of the detection threshold; and calculating the value of the detection threshold ρ s by a formula of the form ρ.sub.s =ρ.sub.av +α(ρ.sub.max -ρ.sub.av) where α designates a coefficient lying between 0 and 1.

Claim 6

The method as claimed in claim 4, wherein the coefficients λ and α lie between 0.8 and 0.9.

Claim 7

The method as claimed in claim 1, wherein the order of the linear-prediction filter lies between 5 and 10.

Claim 10

The device as claimed in claim 7, further comprising means for recursive adapting of the value of the detection threshold depending on the calculated values of the energy ratio, the operation of which is interrupted when the comparison means reveal that the return signal contains components other than the echo components from the forward signal.

Claim 11

The device as claimed in claim 8, wherein the operation of the adapting means is interrupted when useful components are detected in the forward signal.

Claim 12

The device as claimed in claim 8, wherein the adapting means are configured to determine the value of the detection threshold according to a formula of the type ρ.sub.s =ρ.sub.av +α(ρ.sub.max -ρ.sub.av) where ρ av is an average of the energy ratios ρ calculated during the operating periods of the adapting means, obtained by a recursive formula of the form ρ.sub.av =λρ.sub.av +(1-λ)ρ ρ max is the maximum value of the energy ratios ρ calculated during the operating periods of the adapting means, and α and λ are two coefficients lying between 0 and 1.

Claim 13

The device as claimed in claim 10, wherein the coefficients α and λ lie between 0.8 and 0.9.

Claim 14

The device as claimed in claim 7, wherein the order of the linear-prediction filter lies between 5 and 10.

Claim 15

An adaptive echo canceller, for attenuating, in a return signal, echo components from a forward signal, comprising an adaptive filter for modeling echo paths, to which the forward signal is addressed and the output of which is subtracted from the return signal, and a detection device for detecting the presence in the return signal of components other than echo components from the forward signal, the coefficients of the adaptive modeling filter being fixed when said detection device reveals the presence in the return signal of components other than echo components from the forward signal, wherein said detection device comprises: a first finite-impulse-response linear-prediction filter receiving the forward signal and producing a first residual signal of minimal energy; a second finite-impulse-response filter having the same coefficients as the first finite-impulse-response filter, receiving the return signal and producing a second residual signal; means for calculating the ratio of the energies contained in the first and second residual signals; and means for comparing the calculated energy ratio to a detection threshold in order to determine whether the return signal contains components other than echo components from the forward signal.

Claim 16

An adaptive echo canceller, for attenuating, in a return signal, echo components from a forward signal, comprising an adaptive filter for modeling echo paths, to which the forward signal is addressed and the output of which is subtracted from the return signal, and a detection device for detecting the presence in the return signal of components other than echo components from the forward signal, the coefficients of the adaptive modeling filter being fixed when said detection device reveals the presence in the return signal of components other than echo components from the forward signal, wherein said detection device comprises: a first finite-impulse-response linear-prediction filter receiving the forward signal and producing a first residual signal of minimal energy; a second finite-impulse-response filter having the same coefficients as the first finite-impulse-response filter, receiving the return signal and producing a second residual signal; means for calculating the ratio of the energies contained in the first and second residual signals; and means for comparing the calculated energy ratio to a detection threshold in order to determine whether the return signal contains components other than echo components from the forward signal.

Claim 17

The adaptative echo canceller as claimed in claim 13, wherein said detection device further comprises means for recursive adapting of the value of the detection threshold depending on the calculated values of the energy ratio, the operation of which is interrupted when the comparison means reveal that the return signal contains components other than the echo components from the forward signal.

Claim 18

The adaptative echo canceller as claimed in claim 14, wherein the operation of the adapting means is interrupted when useful components are detected in the forward signal.

Claim 19

The adaptative echo canceller as claimed in claim 14, wherein the adapting means are configured to determine the value of the detection threshold according to a formula of the type ρ s =ρ av +α(ρ max -ρ av ), where ρ av is an average of the energy ratios ρ calculated during the operating periods of the adapting means, obtained by a recursive formula of the form ρ av =λρ av +(1-λ)ρ, ρ max is the maximum value of the energy ratios ρ calculated during the operating periods of the adapting means, and α and λ are two coefficients lying between 0 and 1.

Claim 20

The adaptative echo canceller as claimed in claim 16, wherein the coefficients α and λ lie between 0.8 and 0.9.

Claim 21

The adaptative echo canceller as claimed in claim 13, wherein the order of the linear-prediction filter lies between 5 and 10.