MULTICHANNEL ECHO CANCELLATION CIRCUIT AND METHOD AND SMART DEVICE

• US 20190362733A1
• Filed: 12/08/2017
• Published: 11/28/2019
• Est. Priority Date: 06/15/2017
• Status: Active Grant

• Current Assignee: Goertek Incorporated
• Original Assignee: Goertek Incorporated
• Inventors: ZHU, Jian, Zhang, Xiangdong, Yu, Zhenyu, Luo, Zhiping, Yan, Dong
• Granted Patent: US 10,643,634 B2
• Time in Patent Office: Days
• CPC Class Codes: G10L 2021/02082 the noise being echo, reverberation of the speech
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 21/0232 Processing in the frequency domain
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23
• CPC Class Codes: H04R 2227/009 Signal processing in [PA] systems to enhance the speech intelligibility
• CPC Class Codes: H04R 2430/00 Signal processing covered by H04R, not provided for in its groups
• CPC Class Codes: H04R 27/00 Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F
• CPC Class Codes: H04R 3/02 for preventing acoustic reaction , i.e. acoustic oscillatory feedback specially adapted for hearing aids H04R25/453
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S
• CPC Class Codes: H04S 2400/01 Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02

Abstract

The application discloses a multichannel echo cancellation circuit and method and smart device. The multichannel echo cancellation circuit comprises signal extraction circuits, one ends of which are connected to the audio channels of the corresponding loudspeakers, to extract part of the audio signals from the audio channels of the corresponding loudspeakers as echo cancellation reference signals; the other ends of the signal extraction circuits are connected to the isolating circuits; the isolating circuits are interconnected to form one noise channel by which the echo cancellation reference signals extracted by each of the signal extraction circuits are formed into one channel of noise signal and then outputted to the processor; and the processor subtracts the noise signal from the sound signal collected by the microphone according to the noise signal inputted and a sound signal collected by a microphone, to obtain a signal that has been denoised.

Claims

1. A multichannel echo cancellation circuit, comprising a processor, signal extraction circuits and isolating circuits, wherein the number of the signal extraction circuits and the number of the isolating circuits correspond to the number of audio channels of loudspeakers;

one end of each of the signal extraction circuits is connected to the audio channel of the corresponding loudspeaker, and is for extracting part of audio signal from the audio channel of the corresponding loudspeaker as an echo cancellation reference signal;

the other end of each of the signal extraction circuits is connected to each of the isolating circuits, respectively;

the isolating circuits are interconnected to form one noise channel, and by the one noise channel the echo cancellation reference signals that are extracted by each of the signal extraction circuits are formed into one channel of noise signal and then outputted to the processor; and

the processor, according to a noise signal inputted and a sound signal collected by a microphone, subtracts the noise signal from the sound signal that is collected by the microphone, to obtain a signal that has been denoised.

2. The multichannel echo cancellation circuit according to claim 1, wherein each of the isolating circuits comprises a first stage transformer and an output matching network connected to an output end of the first stage transformer, and

each of the signal extraction circuits is an input matching network, the input matching network obtains the echo cancellation reference signal after the audio signal of the corresponding loudspeaker passes through, the echo cancellation reference signal is inputted to the corresponding first stage transformer, and a plurality of the output matching networks are interconnected to form one noise channel by which the echo cancellation reference signals are formed into one channel of noise signal and then outputted to the processor.

3. The multichannel echo cancellation circuit according to claim 2, wherein the isolating circuits further comprise a second stage transformer, and

output ends of each of the output matching networks are connected to input ends of the second stage transformer, and are formed into one noise channel by the second stage transformer, and by the one noise channel the echo cancellation reference signals are formed into one channel of noise signal and then outputted to the processor.

4. The multichannel echo cancellation circuit according to claim 2, wherein the input matching network comprises:

a first input resistor, a first input capacitor and a second input resistor, and

an input end of the first stage transformer is connected in series to the first input capacitor, and then is connected to one end of the second input resistor and one end of the first input resistor, the other end of the second input resistor is connected to a first grounding end of the first stage transformer, the first grounding end is connected to a ground wire of the corresponding loudspeaker, and the other end of the first input resistor is connected to an audio signal wire of the corresponding loudspeaker; and

the output matching network comprises;

a first output resistor, a first output capacitor and a second output resistor, and

an output end of the first stage transformer is connected in series to the first output resistor, and then is connected to one end of the first output capacitor and one end of the second output resistor, the other end of the second output resistor is connected to a second grounding end of the first stage transformer, the second grounding end is connected to a ground wire of the processor, the other end of the first output capacitor is connected to the noise channel, and the noise channel is connected to an audio input end of the processor.

5. The multichannel echo cancellation circuit according to claim 4, wherein the device lectotype of the input matching network satisfies the following condition:

6. The multichannel echo cancellation circuit according to claim 4, wherein

the first input capacitor and the first output capacitor are bridging capacitors;

and

the working frequency range of the first stage transformer is the same as the frequency range of the audio signal outputted to the loudspeaker.

7. The multichannel echo cancellation circuit according to claim 6, wherein

the first stage transformer is a low-frequency transformer, and the working frequency range of the first stage transformer is 10-20000 Hz;

and

capacitance values of the first input capacitor and the first output capacitor are 4.7 μ

F.

8. A multichannel echo cancellation method, comprising the steps of:

extracting, by signal extraction circuits, part of audio signals from audio channels of each of corresponding loudspeakers as echo cancellation reference signals, wherein the number of the signal extraction circuits is the same as the number of the audio channels of the loudspeakers, one end of each of the signal extraction circuits is connected to the audio channel of the corresponding loudspeaker, and the other end of each of the signal extraction circuits is connected to each of isolating circuits, respectively;

interconnecting the isolating circuits that connect to the other ends of the signal extraction circuits to form one noise channel, forming by the noise channel the echo cancellation reference signals into one channel of noise signal and outputting the one channel of noise signal to a processor; and

acquiring by the processor a sound signal that is collected by a microphone, and according to the noise signal inputted and the sound signal collected by the microphone, subtracting the noise signal from the sound signal that is collected by the microphone, to obtain a signal that has been denoised.

9. The multichannel echo cancellation method according to claim 8, wherein the step of interconnecting the isolating circuits connected to the other ends of the signal extraction circuits to form one noise channel comprises:

selecting a first stage transformer, connecting an output matching network to an output end of the first stage transformer to construct the isolating circuit, and interconnecting a plurality of the output matching networks to form one noise channel.

10. The multichannel echo cancellation method according to claim 9, further comprising the step of:

constructing an input matching network and the output matching network by using passive elements, and using the input matching network as the signal extraction circuit, wherein the passive elements comprise resistors and capacitors;

the step of constructing an input matching network by using passive elements comprises;

selecting a first input resistor, a first input capacitor and a second input resistor, and

connecting in series an input end of the first stage transformer to the first input capacitor, then connecting in parallel to the second input resistor, and finally connecting in series to the first input resistor, to construct the input matching network, wherein an input end of the first stage transformer is connected in series to the first input capacitor, and then is connected to one end of the second input resistor and one end of the first input resistor, the other end of the second input resistor is connected to a first grounding end of the first stage transformer, the first grounding end is connected to a ground wire of the corresponding loudspeaker, and the other end of the first input resistor is connected to an audio signal wire of the corresponding loudspeaker; and

the step of constructing by using passive elements an output matching network comprises;

selecting a first output resistor, a first output capacitor and a second output resistor, and

connecting in series an output end of the first stage transformer to the first output resistor, then connecting in parallel to the second output resistor, and finally connecting in series to the first output capacitor, to construct the output matching network, wherein an output end of the first stage transformer is connected in series to the first output resistor, and then is connected to one end of the first output capacitor and one end of the second output resistor, the other end of the second output resistor is connected to a second grounding end of the first stage transformer, the second grounding end is connected to a ground wire of the processor, the other end of the first output capacitor is connected to the noise channel, and the noise channel is connected to an audio input end of the processor.

11. The multichannel echo cancellation method according to claim 10, wherein

the first input capacitor and the first output capacitor are bridging capacitors, and the working frequency range of the first stage transformer is the same as the frequency range of the audio signal outputted to the loudspeaker.

12. The multichannel echo cancellation method according to claim 9, wherein the step of interconnecting the isolating circuits connected to the other ends of the signal extraction circuits to form one noise channel further comprises:

selecting a second stage transformer, connecting output ends of each of the output matching networks to input ends of the second stage transformer to construct the isolating circuit, and forming one noise channel by the second stage transformer.

13. The multichannel echo cancellation method according to claim 10, further comprising the step of:

satisfying the device lectotype of the input matching network the following condition;

14. The multichannel echo cancellation method according to claim 13, further comprising the step of:

selecting the first stage transformer be a low-frequency transformer, and selecting the working frequency range of the first stage transformer to be 10-20000 Hz; and

selecting capacitance values of the first input capacitor and the first output capacitor to be 4.7 μ

F.

15. A smart device, comprising a multichannel echo cancellation circuit, the multichannel echo cancellation circuit comprising a processor, signal extraction circuits and isolating circuits, wherein the number of the signal extraction circuits and the number of the isolating circuits correspond to the number of audio channels of loudspeakers;

one end of each of the signal extraction circuits is connected to the audio channel of the corresponding loudspeaker, and is for extracting part of audio signal from the audio channel of the corresponding loudspeaker as an echo cancellation reference signal;

the other end of each of the signal extraction circuits is connected to each of the isolating circuits, respectively;

the isolating circuits are interconnected to form one noise channel, and by the one noise channel the echo cancellation reference signals that are extracted by each of the signal extraction circuits are formed into one channel of noise signal and then outputted to the processor; and

the processor, according to a noise signal inputted and a sound signal collected by a microphone, subtracts the noise signal from the sound signal that is collected by the microphone, to obtain a signal that has been denoised.

16. The smart device according to claim 15, wherein each of the isolating circuits comprises a first stage transformer and an output matching network connected to an output end of the first stage transformer, and

each of the signal extraction circuits is an input matching network, the input matching network obtains the echo cancellation reference signal after the audio signal of the corresponding loudspeaker passes through, the echo cancellation reference signal is inputted to the corresponding first stage transformer, and a plurality of the output matching networks are interconnected to form one noise channel by which the echo cancellation reference signals are formed into one channel of noise signal and then outputted to the processor.

17. The smart device according to claim 16, wherein the isolating circuits further comprise a second stage transformer, and

output ends of each of the output matching networks are connected to input ends of the second stage transformer, and are formed into one noise channel by the second stage transformer, and by the one noise channel the echo cancellation reference signals are formed into one channel of noise signal and then outputted to the processor.

18. The smart device according to claim 16, wherein the input matching network comprises:

a first input resistor, a first input capacitor and a second input resistor, and

an input end of the first stage transformer is connected in series to the first input capacitor, and then is connected to one end of the second input resistor and one end of the first input resistor, the other end of the second input resistor is connected to a first grounding end of the first stage transformer, the first grounding end is connected to a ground wire of the corresponding loudspeaker, and the other end of the first input resistor is connected to an audio signal wire of the corresponding loudspeaker; and

the output matching network comprises;

a first output resistor, a first output capacitor and a second output resistor, and

an output end of the first stage transformer is connected in series to the first output resistor, and then is connected to one end of the first output capacitor and one end of the second output resistor, the other end of the second output resistor is connected to a second grounding end of the first stage transformer, the second grounding end is connected to a ground wire of the processor, the other end of the first output capacitor is connected to the noise channel, and the noise channel is connected to an audio input end of the processor.

19. The smart device according to claim 18, wherein the device lectotype of the input matching network satisfies the following condition:

20. The smart device according to claim 18, wherein

the first input capacitor and the first output capacitor are bridging capacitors;

the working frequency range of the first stage transformer is the same as the frequency range of the audio signal outputted to the loudspeaker;

the first stage transformer is a low-frequency transformer, and the working frequency range of the first stage transformer is 10-20000 Hz; and

capacitance values of the first input capacitor and the first output capacitor are 4.7 μ

F.