Acoustic echo cancellation

• US 20030202654A1
• Filed: 04/30/2002
• Published: 10/30/2003
• Est. Priority Date: 04/30/2002
• Status: Active Grant

• Current Assignee: Innomedia Pte Ltd
• Original Assignee: Innomedia Pte Ltd
• Inventors: Xiong, Ying
• Granted Patent: US 6,947,550 B2
• Time in Patent Office: Days
• US Class Current: 379/406.01
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

The invention is an echo canceller for reducing the magnitude of an echo occurring in a return channel of a communication device and a method of implementing the same. The echo canceller includes a processing unit for generating an echo attenuated signal. The processing unit includes a first input, a second input and an output. The first input is for receiving a first signal that is the precursor of the echo. The second input is for receiving a second signal that potentially contains the echo. The output is for outputting the echo attenuated signal. The echo attenuated signal is derived by combining the second signal and an adaptation signal. The adaptation signal is generated by normalizing the echo attenuated signal to produce a normalized adaptation signal, and combining the normalized adaptation signal with the first signal to generate an intermediate signal. Additionally, the intermediate signal is de-normalized to produce the adaptation signal.

Claims

1. An echo canceller for reducing the magnitude of an echo occurring in a return channel of a communication device, said echo canceller comprising:

a processing unit for generating an echo attenuated signal, the processing unit including;

a) a first input for receiving a first signal that is the precursor of the echo;

b) a second input for receiving a second signal that potentially contains the echo, and

c) an output for outputting the echo attenuated signal, wherein the echo attenuated signal is derived by combining the second signal and an adaptation signal, wherein the adaptation signal is generated by normalizing the echo attenuated signal to produce a normalized adaptation signal, and combining the normalized adaptation signal with the first signal to generate an intermediate signal, and the intermediate signal is de-normalized to produce the adaptation signal.

2. The echo canceller according to claim 1, wherein the adaptation signal is an estimate of the echo signal.

3. The echo canceller according to claim 2, wherein the estimate of the echo signal is generated by adapting and weighting the echo attenuated signal.

4. The echo canceller according to claim 1, wherein the processing unit is operative to iteratively reduce a difference between the adaptation signal and the echo in the second signal.

5. The echo canceller according to claim 1, wherein the processing unit includes an adaptive filter which generates the echo attenuated signal, the adaptive filter being characterized by a transfer function and the adaptation signal which estimates the echo in the return channel of the communication device causes the adaptive filter to alter the transfer function to iteratively reduce the difference between the adaptation signal and the second signal.

6. The echo canceller according to claim 1, wherein the processing unit includes an adder, the adder being operative to subtract the adaptation signal from the second signal that potentially contains the echo to generate the error signal.

7. The echo canceller according to claim 5, wherein the processing unit includes an updating unit for periodically updating the transfer function characterizing the adaptive filter to tend to reduce the error signal.

8. The echo canceller according to claim 7, wherein the updating unit updates the transfer function on a basis of the error signal.

9. The echo canceller according to claim 5, wherein the adaptive filter includes a main FIR component.

10. The echo canceller according to claim 9, wherein the main FIR component includes at least two taps.

11. The echo canceller according to claim 10, wherein the at least two taps are separated into segments to represent at least two components of the first signal.

12. The echo canceller according to claim 11, wherein weighting is added to the segments to de-normalize the first signal.

13. The echo canceller according to claim 11, wherein weighting is added to the segments to normalize the echo attenuated signal.

14. A telecommunication device including the echo canceller defined in claim 1.

15. A method for reducing the magnitude of an echo occurring in a return channel of a communication device, said method comprising:

generating an echo attenuated signal, wherein generating an echo attenuated signal includes the steps of;

a) receiving a first signal that is the precursor of the echo through a first input;

b) receiving a second signal that potentially contains the echo from a second input;

c) outputting the echo attenuated signal from an output;

d) combining the second signal and an adaptation signal to derive the echo attenuated signal;

e) generating the normalized adaptation signal; and

f) de-normalizing an intermediate signal to produce the adaptation signal.

16. A method as defined in claim 15, wherein the step of generating the normalized adaptation signal further includes the steps of normalizing the echo attenuated signal to produce a normalized adaptation signal;

and

2) combining the normalized adaptation signal with the first signal to generate the intermediate signal.

17. A method as defined in claim 15, further including the step of subtracting the echo estimate from the second signal that potentially contains echo to generate the error signal.

18. A method as defined in claim 15, further including the step of iteratively reducing a difference between the adaptation signal and the echo in the second signal.

19. A method as defined in claim 15, further including the step of adapting and weighting the echo attenuated signal to generated the estimate of the echo signal.

20. A method as defined in claim 15, further including the steps of:

g) weighting segments of the echo attenuated signal to normalize the echo attenuated signal; and

h) weighting segments of the intermediate signal to produce the adaptation signal.