Multichannel echo cancellation circuit and method and smart device

• US 10,643,634 B2
• Filed: 12/08/2017
• Issued: 05/05/2020
• 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
• Primary Examiner(s): Zhang, Leshui
• Application Number:
  US15/780,156
• Publication Number:
  US 20190362733A1
• Time in Patent Office: 879 Days
• Field of Search: 381 17, 381 18, 381 19, 381 20, 381 21, 381300, 381301, 381302, 381303, 381307, 381119, 381 66, 381 27, 381 711- 716, 381 719, 381 7111, 381 7112, 381 26, 381318, 381 86, 381 92, 381 941, 381 93, 381 95, 381 96, 381122, 381123, 37940601-40616, 4555691, 455570, 704E19014, 704E21002, 704E21004, 704E21007
• 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;

a number of signal extraction circuits, and one end of each of the signal extraction circuits is connected to one of a number of audio channels corresponding to a number of loudspeakers, and wherein the number of the signal extraction circuits corresponds to the number of the audio channels of the loudspeakers, and each of the signal extraction circuits extracts part of each of audio signals as each of echo cancellation reference signals, from each of the audio channels corresponding to the number of the loudspeakers; and

a number of isolating circuits, and one end of each of the isolating circuits is connected to other end of each of the signal extraction circuits, and wherein the number of the isolating circuits corresponds to the number of audio channels of the loudspeakers, and the isolating circuits are interconnected to combine the echo cancellation reference signals that are extracted by each of the signal extraction circuits into one noise signal at one noise channel, and the one noise signal at the one noise channel is further outputted to the processor, and

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

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, each of the audio signals of the loudspeakers passes through the input matching network to obtain each of the echo cancellation reference signals, each of the echo cancellation reference signals is inputted to the corresponding first stage transformer and then inputted to the corresponding output matching networks, and a plurality of the output matching networks are interconnected to form the one noise channel, the echo cancellation reference signals are combined into the one noise signal at the one noise channel; and

wherein the function of the input matching network is to realize the matching between an output impedance of the loudspeakers and an input impedance of the first stage transformer, the function of the output matching network is to ensure the matching between an output impedance of the first stage transformer and an input impedance of the processor.

2. The multichannel echo cancellation circuit according to claim 1, 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 the first input capacitor 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 the first output resistor 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.

3. The multichannel echo cancellation circuit according to claim 2, wherein a device lectotype of the input matching network satisfies the following condition:

4. The multichannel echo cancellation circuit according to claim 2, 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.

5. The multichannel echo cancellation circuit according to claim 4, 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.

6. A multichannel echo cancellation method, comprising:

extracting part of each of audio signals, by each of a number of signal extraction circuits, as each of echo cancellation reference signals, from each of a number of audio channels corresponding to a number of loudspeakers, wherein the number of the signal extraction circuits corresponds to the number of audio channels of the loudspeakers, and one end of each of the signal extraction circuits is connected to one of the audio channels corresponding to the number of the loudspeakers;

interconnecting a number of isolating circuits to combine the echo cancellation reference signals that are extracted by each of the signal extraction circuits into one noise signal at one noise channel, wherein one end of each of the isolating circuits is connected to other end of each of the signal extraction circuits and the number of the isolating circuits corresponds to the number of audio channels of the loudspeakers;

outputting the one noise signal at the one noise channel to a processor;

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

wherein each of the signal extraction circuits is an input matching network;

wherein interconnecting a number of isolating circuits to combine the echo cancellation reference signals that are extracted by each of the signal extraction circuits into one noise signal at one noise channel comprises;

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

wherein the function of the input matching network is to realize the matching between an output impedance of the loudspeakers and an input impedance of the first stage transformer, the function of the output matching network is to ensure the matching between an output impedance of the first stage transformer and an input impedance of the processor.

7. The multichannel echo cancellation method according to claim 6, further comprising:

constructing the input matching network and the output matching network by using passive elements, wherein the passive elements comprise resistors and capacitors;

wherein constructing the 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 the first input capacitor 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

wherein constructing by using passive elements the 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 the first output resistor 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.

8. The multichannel echo cancellation method according to claim 7, 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.

9. The multichannel echo cancellation method according to claim 7, further comprising:

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

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

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.

11. A smart device, comprising a multichannel echo cancellation circuit, the multichannel echo cancellation circuit comprising:

a processor;

a number of signal extraction circuits, and one end of each of the signal extraction circuits is connected to one of a number of audio channels corresponding to a number of loudspeakers, and wherein the number of the signal extraction circuits corresponds to the number of the audio channels of the loudspeakers, and each of the signal extraction circuits extracts part of each of audio signals as each of echo cancellation reference signals, from each of the audio channels corresponding to the number of the loudspeakers; and

a number of isolating circuits, and one end of each of the isolating circuits is connected to other end of each of the signal extraction circuits, and wherein the number of the isolating circuits corresponds to the number of audio channels of the loudspeakers, and the isolating circuits are interconnected to combine the echo cancellation reference signals that are extracted by each of the signal extraction circuits into one noise signal at one noise channel, and the one noise signal at the one noise channel is further outputted to the processor, and

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

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, each of the audio signals of the loudspeakers passes through the input matching network to obtain each of the echo cancellation reference signals, each of the echo cancellation reference signals is inputted to the corresponding first stage transformer and then inputted to the corresponding output matching networks, and a plurality of the output matching networks are interconnected to form the one noise channel, the echo cancellation reference signals are combined into the one noise signal at the one noise channel;

and wherein the function of the input matching network is to realize the matching between an output impedance of the loudspeakers and an input impedance of the first stage transformer, the function of the output matching network is to ensure the matching between an output impedance of the first stage transformer and an input impedance of the processor.

12. The smart device according to claim 11, 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 the first input capacitor 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 the first output resistor 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.

13. The smart device according to claim 12, wherein a device lectotype of the input matching network satisfies the following condition:

14. The smart device according to claim 12, 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.