Echo canceller

Claim 2

An echo canceller comprising: echo replica generating means for generating an echo replica signal based on a received signal and including filter having tap coefficients; subtracting means coupled to said echo replica generating means for obtaining a transmitting side output signal by subtracting the echo replica signal generated by said echo replica generating means from a transmitting side input signal; divergence detecting means coupled to said echo replica generating means and said subtracting means for detecting a divergence of the echo canceller based on the transmitting side input signal and the echo replica signal, the detecting being based on a comparison between a first power of the transmitting side input signal and a second power of the echo replica signal and for outputting a detection signal when the divergence is detected; and resetting means coupled to said divergence detecting means for automatically resetting said echo replica generating means in response to the detection signal from said divergence detecting means.

Claim 3

The echo canceller as claimed in claim 1, wherein said filter in said echo replica generating means comprises an adaptive filter including a storage for storing the received signal as tap values, and for storing tap coefficients corresponding to the tap values, an echo replica generator for generating the echo replica signal based on the tap values and the tap coefficients corresponding to the tap values, and a tap coefficient updating circuit for updating the tap coefficients based on the received signal and the transmitting side output signal so that the tap coefficients converge, said divergence of the echo canceller being a divergence of the tap coefficients of said adaptive filter.

Claim 4

The echo canceller as claimed in claim 2, wherein said resetting means resets data stored in said storage to zero in response to the detection signal from said divergence detecting means.

Claim 5

The echo canceller as claimed in claim 1, wherein said divergence detecting means includes a divergence detector coupled to said echo replica generating means and said subtracting means for detecting the divergence of the echo canceller and outputting the detection signal when a ratio of the echo replica signal to the transmitting side input signal becomes greater than a predetermined ratio.

Claim 6

The echo canceller as claimed in claim 1, wherein said divergence detecting means includes a divergence detector for detecting the divergence of the echo canceller only when a ratio of the echo replica signal to the transmitting side input signal becomes greater than a predetermined ratio and no correlation exists between the transmitting side input signal and the transmitting side output signal.

Claim 7

An echo canceller comprising: echo replica generating means for generating an echo replica signal based on a received signal and including a filter having tap coefficients; subtracting means coupled to said echo replica generating means for obtaining a transmitting side output signal by subtracting the echo replica signal generated by said echo replica generating means from a transmitting side input signal; divergence detecting means coupled to said echo replica generating means and said subtracting means for detecting a divergence of the echo canceller based on the transmitting side output signal and the echo replica signal, the detecting being based on a comparison between a predetermined threshold value and at least one of a first power of the transmitting side output signal and a second power of the echo replica signal and for outputting a detection signal when the divergence is detected; and resetting means coupled to said divergence detecting means for automatically resetting said echo replica generating means in response to the detection signal from said divergence detecting means.

Claim 8

An echo canceller comprising: echo replica generating means for generating an echo replica signal based on a received signal and including a filter having tap coefficients; subtracting means coupled to said echo replica generating means for obtaining a transmitting side output signal by subtracting the echo replica signal generated by said echo replica generating means from a transmitting side input signal; divergence detecting means coupled to said echo replica generating means and said subtracting means for detecting a divergence of the echo canceller based on the transmitting side output signal and the echo replica signal, the detecting being based on a comparison between a predetermined threshold value and at least one of a first power of the transmitting side output signal and a second power of the echo replica signal and for outputting a detection signal when the divergence is detected; and resetting means coupled to said divergence detecting means for automatically resetting said echo replica generating means in response to the detection signal from said divergence detecting means.

Claim 9

The echo canceller as claimed in claim 6, wherein said filter in said echo replica generating means comprises an adaptive filter including a storage for storing the received signal as tap values, and for storing tap coefficients corresponding to the tap values, an echo replica generator for generating the echo replica signal based on one of the tap values and a corresponding one of the tap coefficients, and a tap coefficient updating circuit for updating the tap coefficients based on the received signal and the transmitting side output signal so that the tap coefficients converge, said divergence of the echo canceller being a divergence of the tap coefficients of said adaptive filter.

Claim 10

The echo canceller as claimed in claim 7, wherein said resetting means resets data stored in said storage to zero in response to the detection signal from said divergence detecting means.

Claim 11

The echo canceller as claimed in claim 6, wherein said divergence detecting means includes a divergence detector coupled to said echo replica generating means and said subtracting means for detecting the divergence of the echo canceller and outputting the detection signal when one of the echo replica signal and the transmitting side output signal exceeds the predetermined threshold value.

Claim 12

The echo canceller as claimed in claim 6, wherein said divergence detecting means includes a divergence detector coupled to said echo replica generating means and said subtracting means for detecting the divergence of the echo canceller and outputting the detection signal when both the echo replica signal and the transmitting side output signal exceed the predetermined threshold value.

Claim 13

The echo canceller as claimed in claim 6, wherein said divergence detecting means includes first means for outputting a first detection signal when the transmitting side output signal exceeds the predetermined threshold value, second means for outputting a second detection signal when the echo replica signal exceeds the predetermined threshold value, and an OR circuit supplied with the first and second detection signals of said first and second means for outputting the detection signal.

Claim 14

The echo canceller as claimed in claim 11, wherein the predetermined threshold value is set to a maximum output value of a PCM coder/decoder which is coupled to a line via the echo canceller.

Claim 15

The echo canceller as claimed in claim 6, wherein said divergence detecting means includes first means for outputting a first detection signal when the transmitting side output signal exceeds the predetermined threshold value, second means for outputting a second detection signal when the echo replica signal exceed the predetermined threshold value, and an AND circuit supplied with first and second detection signals of said first and second means for outputting the detection signal.

Claim 16

The echo canceller as claimed in claim 13, wherein the predetermined threshold value is set to a maximum output value of a PCM coder/decoder which is coupled to a line via the echo canceller.

Claim 17

The echo canceller as claimed in claim 6, wherein said divergence detecting means includes a divergence detector for detecting the divergence of the echo canceller only when at least one of the echo replica signal and the transmitting side output signal exceeds the predetermined threshold value and no correlation exists between the transmitting side input signal and the transmitting side output signal.

Claim 18

An echo canceller comprising: echo replica generating means for generating an echo replica signal based on a received signal and including a filter having tap coefficients; subtracting means coupled to said echo replica generating means for obtaining a transmitting side output signal by subtracting the echo replica signal generated by said echo replica generating means from a transmitting side input signal; divergence detecting means coupled to said echo replica generating means and said subtracting means for detecting a divergence of the echo canceller based on the transmitting side input signal and the echo replica signal, the detecting being based on a first comparison between a first power of the transmitting side input signal and a second power of the transmitting side output signal and a second comparison between a predetermined value and the first power of the transmitting side output signal and for outputting a detection signal when the divergence is detected; and resetting means coupled to said divergence detecting means for automatically resetting said echo replica generating means in response to the detection signal from said divergence detecting means.

Claim 19

An echo canceller comprising: echo replica generating means for generating an echo replica signal based on a received signal and including a filter having tap coefficients; subtracting means coupled to said echo replica generating means for obtaining a transmitting side output signal by subtracting the echo replica signal generated by said echo replica generating means from a transmitting side input signal; divergence detecting means coupled to said echo replica generating means and said subtracting means for detecting a divergence of the echo canceller based on the transmitting side input signal and the echo replica signal, the detecting being based on a first comparison between a first power of the transmitting side input signal and a second power of the transmitting side output signal and a second comparison between a predetermined value and the first power of the transmitting side output signal and for outputting a detection signal when the divergence is detected; and resetting means coupled to said divergence detecting means for automatically resetting said echo replica generating means in response to the detection signal from said divergence detecting means.

Claim 20

The echo canceller as claimed in claim 16, wherein said echo replica generating means comprises an adaptive filter including a storage for storing the received signal as tap values, and for storing tap coefficients corresponding to the tap values, an echo replica generator for generating the echo replica signal based on the tap values and the tap coefficients corresponding to the tap values, and a tap coefficient updating circuit for updating the tap coefficients based on the received signal and the transmitting side output signal so that the tap coefficients converge, said divergence of the echo canceller being a divergence of the tap coefficients of said adaptive filter.

Claim 21

The echo canceller as claimed in claim 17, wherein said resetting means resets data stored in said storage to zero in response to the detection signal from said divergence detecting means.

Claim 22

The echo canceller as claimed in claim 16, wherein said divergence detecting means includes a divergence detector coupled to said echo replica generating means for detecting the divergence of the echo canceller and outputting the detection signal when a ratio of the first power of the transmitting side input signal to the second power of the transmitting side output signal becomes greater than a predetermined ratio and the first power of the transmitting side output signal becomes greater than the predetermined value.

Claim 23

The echo canceller as claimed in claim 16, wherein said divergence detecting means includes a divergence detector for detecting the divergence of the echo canceller only when a ratio of the transmitting side input signal to the transmitting side output signal becomes greater than a predetermined ratio and no correlation exists between the transmitting side input signal and the transmitting side output signal.

Claim 24

An echo canceller comprising: echo replica generating means for generating an echo replica signal based on a received signal and including a filter having tap coefficients; subtracting means coupled to said echo replica generating means for obtaining a transmitting side output signal by subtracting the echo replica signal generated by said echo replica generating means from a transmitting side input signal; divergence detecting means coupled to said subtracting means for detecting a divergence of the echo canceller based on the transmitting side input signal and the echo replica signal, the detecting being based on a comparison between a first power of the transmitting side output signal and a second power of a receiving side input signal and a correlation between the transmitting side input signal and the transmitting side output signal, and for outputting a detection signal when the divergence is detected; and resetting means coupled to said divergence detecting means for automatically resetting said echo replica generating means in response to the detection signal from said divergence detecting means.

Claim 25

An echo canceller comprising: echo replica generating means for generating an echo replica signal based on a received signal and including a filter having tap coefficients; subtracting means coupled to said echo replica generating means for obtaining a transmitting side output signal by subtracting the echo replica signal generated by said echo replica generating means from a transmitting side input signal; divergence detecting means coupled to said subtracting means for detecting a divergence of the echo canceller based on the transmitting side input signal and the echo replica signal, the detecting being based on a comparison between a first power of the transmitting side output signal and a second power of a receiving side input signal and a correlation between the transmitting side input signal and the transmitting side output signal, and for outputting a detection signal when the divergence is detected; and resetting means coupled to said divergence detecting means for automatically resetting said echo replica generating means in response to the detection signal from said divergence detecting means.

Claim 26

The echo canceller as claimed in claim 21, wherein said divergence detecting means includes a divergence detector for detecting the divergence of the echo canceller only when the first power of the transmitting side output signal and the second power of the receiving side input signal are approximately the same and no correlation exists between the transmitting side input signal and the transmitting side output signal.

Claim 27

The echo canceller as claimed in claim 22, wherein said divergence detecting means includes a signal power calculating part for calculating the first and second powers forming calculated first and second powers of the transmitting side output signal and the receiving side input signal, a correlation calculating part for calculating the correlation between the transmitting side input signal and the transmitting side output signal, and a judgement part for determining the divergence and outputting the detection signal only when the first and second calculated powers are approximately the same and the correlation between the transmitting side input signal and the transmitting side output signal is less than a predetermined threshold value.