An adaptive echo cancellation circuit

Abstract

The utility model relates to a kind of self-adaptive echo cancellation circuit, including mixed audio signal processing module, loudspeaker audio signal processing module and echo cancellation module, wherein the mixed audio signal processing module and loudspeaker audio signal processing module are connected with the echo cancellation module;The mixed audio signal processing module, including opposite-phase mixed audio signal output module and in-phase mixed audio signal output module;The opposite-phase mixed audio signal output module is used to obtain mixed audio signal, and to in-phase mixed audio signal output module, echo cancellation module exports opposite-phase mixed audio signal;The in-phase mixed audio signal output module is used to export in-phase mixed audio signal to echo cancellation module according to opposite-phase mixed audio signal;The loudspeaker audio signal processing module is used to obtain loudspeaker audio signal, and exports a set of differential audio signal to echo cancellation module. The utility model can solve the problem of echo generated by the speaker of the existing intercom equipment, improve the sound clarity and the user experience.

Description

Technical Field

[0001] This utility model relates to the field of audio signal processing technology, and in particular to an adaptive echo cancellation circuit. Background Technology

[0002] In some two-way voice communication terminals, such as bank teller intercoms, subway platform emergency intercoms, rugged mobile phones / tablets with intercom functions, and satellite phones, users need to perform "speaking" and "listening" operations simultaneously, which places extremely high demands on the real-time performance, clarity, and echo-free experience of the voice.

[0003] Existing intercom systems typically consist of five main parts: a microphone, a speaker, an audio amplification / conversion circuit, a network transmission module, and a power supply. The microphone picks up local voice, which is then amplified and sent to the network transmission module. The network transmission module digitizes the analog signal and transmits it to the remote device via a local area network (LAN) or wide area network (WAN). Upon receiving the data, the remote device converts it back to analog audio via a DAC, which then powers the speaker. Since this link is physically located within the same acoustic space, the sound emitted by the speaker can easily be picked up again by the microphone.

[0004] Because a closed acoustic loop is formed between the speaker and the microphone, when the system gain is large enough or the sound field coupling is strong, the voice from the far end is sent back to the far end after round-trip delay, forming a perceptible echo or even howling. Existing technologies rely only on simple gain limiting or fixed filtering, which cannot adaptively adjust according to the environment, resulting in poor echo suppression and reduced speech clarity, which seriously affects the user experience. Utility Model Content

[0005] Therefore, the purpose of this utility model is to overcome the defects or deficiencies of the prior art and provide an adaptive echo cancellation circuit.

[0006] An adaptive echo cancellation circuit includes a mixed audio signal processing module, a speaker audio signal processing module, and an echo cancellation module, wherein the mixed audio signal processing module and the speaker audio signal processing module are both connected to the echo cancellation module. The mixed audio signal processing module includes an inverted mixed audio signal output module and a non-inverted mixed audio signal output module. The inverted mixed audio signal output module is used to acquire a mixed audio signal and output an inverted mixed audio signal to the non-inverted mixed audio signal output module and the echo cancellation module. The non-inverted mixed audio signal output module is used to output a non-inverted mixed audio signal to the echo cancellation module based on the inverted mixed audio signal. The speaker audio signal processing module is used to acquire a speaker audio signal and output a set of return differential mixed audio signals to the echo cancellation module.

[0007] Compared with existing technologies, the adaptive echo cancellation circuit provided by this utility model can solve the problem of echo generation when speaking in existing intercom devices, which leads to poor user experience and improves sound clarity.

[0008] In one embodiment, the inverted mixed audio signal output module includes an operational amplifier U1A, resistors R1, R2, and R3, capacitor C1, resistor R4, capacitor C2, and resistor R6.

[0009] The positive input terminal of the operational amplifier U1A is connected to resistor R1, the other end of resistor R1 is connected to resistor R2, and the other end of resistor R2 is connected to a +12V power supply. The negative input terminal of the operational amplifier U1A is connected to resistor R3, the other end of resistor R3 is connected to capacitor C1, and the other end of capacitor C1 is connected to the input terminal of the mixed audio signal. The two power supply terminals of the operational amplifier U1A are connected to a +12V power supply and ground, respectively. A resistor R4 is connected in parallel between the negative input terminal and the output terminal of the operational amplifier U1A, and a capacitor C2 is also connected in parallel across the two ends of resistor R4. The output terminal of the operational amplifier U1A is connected in sequence to ferrite bead LB1 and capacitor C3, the other end of capacitor C3 is connected to the echo cancellation module. The output terminal of the operational amplifier U1A is also connected to resistor R6, the other end of which is grounded.

[0010] In one embodiment, a capacitor C4 is also connected between the resistors R1 and R2, with the other end of the capacitor C4 grounded; the positive power supply terminal of the operational amplifier U1A is also connected to a capacitor C5, with the other end of the capacitor C5 grounded.

[0011] In one embodiment, a mixed audio signal input circuit is also included, which includes resistor R7, resistor R8, capacitor C6, and capacitor C7;

[0012] The input terminal of the mixed audio signal is connected to the resistor R7, the other end of the resistor R7 is connected to the resistor R8, the other end of the resistor R8 is connected to the +3.3V power supply, the other end of the resistor R7 is also connected to the capacitor C6, the other end of the capacitor C6 is grounded, and the two ends of the capacitor C6 are also connected in parallel with the capacitor C7.

[0013] The input terminal of the mixed audio signal is also connected to resistor R5, the other end of which is grounded.

[0014] In one embodiment, the in-phase mixed audio signal output module includes an operational amplifier U1B, resistors R9 and R10, capacitor C8, resistors R11 and R12, capacitor C9, a ferrite bead LB2, and capacitor C10; the positive input terminal of the operational amplifier U1B is connected to resistor R9, the other end of resistor R9 is connected to resistor R10, and the other end of resistor R10 is connected to a +12V power supply; the inverting input terminal of the operational amplifier U1B is connected to the output terminal of the operational amplifier U1A, and... A capacitor C8 and a resistor R11 are connected sequentially from the output terminal of operational amplifier U1A to the inverting input terminal of operational amplifier U1B; the two power supply terminals of operational amplifier U1B are connected to a +12V power supply and ground, respectively; a resistor R12 is connected between the inverting input terminal and the output terminal of operational amplifier U1B, and a capacitor C9 is connected in parallel across the two ends of the resistor R12; the output terminal of operational amplifier U1B is connected sequentially to a ferrite bead LB2 and a capacitor C10, and the other end of the capacitor C10 is connected to the echo cancellation module;

[0015] A capacitor C11 is connected between resistors R10 and R9, with the other end of capacitor C11 grounded; the positive power supply terminal of operational amplifier U1B is also connected to capacitor C16, with the other end of capacitor C16 grounded; the output terminal of operational amplifier U1B is also connected to resistor R13, with the other end of resistor R13 grounded.

[0016] In one embodiment, the speaker audio signal processing module includes a ferrite bead LB3, a resistor R14, a capacitor C12, a resistor R15, a capacitor C13, a capacitor C14, a resistor R16, a resistor R17, and a capacitor C15. One end of the ferrite bead LB3 is connected to the input terminal of the speaker audio signal, and its other end is connected sequentially to the resistor R14, the capacitor C12, and the resistor R15. The other end of the resistor R15 is connected to the echo cancellation module. The capacitor C13 is connected between the ferrite bead LB3 and the resistor R14. The other end of the capacitor C13 is connected sequentially to the capacitor C14 and the resistor R16. The other end of the resistor R16 is connected to the echo cancellation module. One end of the resistor R17 is connected between the resistor R14 and the capacitor C12, and its other end is connected between the capacitor C13 and the capacitor C14. The capacitor C15 is connected in parallel across the two ends of the resistor R17. The capacitors C13 and C14 are grounded.

[0017] In one embodiment, the echo cancellation module is an FM1388 chip, which includes pins IN1N, IN1P, IN2N, and IN2P.

[0018] In one embodiment, the inverting mixed audio signal output module is connected to the IN1P pin of the FM1388 chip;

[0019] The in-phase mixed audio signal output module is connected to the IN1N pin of the FM1388 chip;

[0020] The output terminal of resistor R15 is connected to the IN2N pin of the FM1388 chip;

[0021] The output terminal of resistor R16 is connected to the IN2P pin of the FM1388 chip.

[0022] In one embodiment, the resistance values ​​of resistors R1, R9, R10, R14, R15, R16, and R17 are 1KΩ; the resistance values ​​of resistors R2, R3, R4, R9, R11, and R12 are 10KΩ; the resistance value of resistor R5 is 4.7KΩ; the resistance values ​​of resistors R6 and R13 are 47KΩ; and the resistance value of resistor R7 is 2.2KΩ. The capacitance values ​​of capacitors C1, C3, C8, C10, C12, and C14 are 4.7μF; the capacitance values ​​of capacitors C2 and C9 are 56pF; the capacitance values ​​of capacitors C4, C6, and C11 are 10μF; the capacitance values ​​of capacitors C5, C7, and C16 are 0.1μF; and the capacitance values ​​of capacitors C13 and C15 are 2.2nF. The impedance of the magnetic beads LB1, LB2, and LB3 at 100MHz is 150Ω.

[0023] In one embodiment, the system further includes a main control module connected to the echo cancellation module. The main control module is composed of a microprocessor and is used to transmit data and instructions via an I2C bus.

[0024] The data transmission module is connected to the echo cancellation module and is used to convert the analog audio received from the echo cancellation module 30 into digital audio and output it.

[0025] The power amplifier module is connected to the data transmission module and is used to receive the low-level analog mixed audio signal output from the data transmission module and amplify it to drive the speaker to emit a sound of sufficient volume.

[0026] The power module includes a DC adapter or PoE that can output 12V power and can output 1.8V and 3.3V power through a step-down chip.

[0027] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the module structure of this utility model;

[0029] Figure 2 This is a schematic diagram of the circuit structure of the hybrid audio signal processing module of this utility model;

[0030] Figure 3 This is a schematic diagram of the circuit structure of the speaker audio signal processing module of this utility model;

[0031] Figure 4 This is a pin diagram of the FM1388 chip in this utility model. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings.

[0033] like Figure 1 As shown, an adaptive echo cancellation circuit of the present invention includes a hybrid audio signal processing module 10, a speaker audio signal processing module 20, and an echo cancellation module 30, wherein the hybrid audio signal processing module 10 and the speaker audio signal processing module 20 are both connected to the echo cancellation module 30.

[0034] The echo cancellation module 30 is used to compare and process the mixed audio signal with the speaker audio signal to achieve the effect of echo cancellation; in this application, the FM1388 chip is used to implement echo cancellation.

[0035] Specifically, the mixed audio signal is the output signal from the microphone, which is a mixture of live human voices and loudspeaker echoes; the loudspeaker audio signal is the output signal from the loudspeaker, which will serve as a reference signal for loudspeaker echo cancellation.

[0036] Specifically, such as Figure 2 As shown, the mixed audio signal is input to pins IN1N and IN1P of the FM1388 chip, and the speaker audio signal is input to pins IN2N and IN2P of the FM1388 chip. The FM1388 chip compares and processes the acquired mixed audio signal and speaker audio signal, and uses the speaker audio signal to remove the signal returned by the speaker from the mixed audio signal, finally obtaining the live human voice signal.

[0037] The mixed audio signal processing module 10 is used to convert the input unbalanced mixed audio signal into a balanced mixed audio signal. It includes an inverted mixed audio signal output module 11 and a non-inverted mixed audio signal output module 12. The inverted mixed audio signal output module 11 is used to acquire the mixed audio signal and output the inverted mixed audio signal to the non-inverted mixed audio signal output module 12 and the echo cancellation module 30. The non-inverted mixed audio signal output module 12 is used to output the non-inverted mixed audio signal to the echo cancellation module 30 based on the inverted mixed audio signal.

[0038] The inverting mixed audio signal output module 11 includes an operational amplifier U1A, resistors R1, R2, and R3, and capacitors C1, R4, and C2. The positive input terminal of operational amplifier U1A is connected to resistor R1, the other end of resistor R1 is connected to resistor R2, and the other end of resistor R2 is connected to a +12V power supply. The inverting input terminal of operational amplifier U1A is connected to resistor R3, the other end of resistor R3 is connected to capacitor C1, and the other end of capacitor C1 is connected to the input terminal of the mixed audio signal. The two power supply terminals of operational amplifier U1A are connected to a +12V power supply and ground, respectively. A resistor R4 is connected in parallel between the inverting input terminal and the output terminal of operational amplifier U1A, and a capacitor C2 is also connected in parallel across resistor R4. The output terminal of operational amplifier U1A is connected sequentially to a ferrite bead LB1 and capacitor C3, and the other end of capacitor C3 is connected to the IN1P pin of the FM1388 chip.

[0039] Furthermore, a capacitor C4 is connected between resistor R1 and resistor R2, with the other end of capacitor C4 grounded; the positive power supply terminal of operational amplifier U1A is also connected to capacitor C5, with the other end of capacitor C5 grounded.

[0040] Furthermore, the input terminal of the mixed audio signal is also connected to resistor R5, the other end of which is grounded.

[0041] Furthermore, the output terminal of the operational amplifier U1A is also connected to resistor R6, and the other end of resistor R6 is grounded.

[0042] Specifically, it also includes a microphone 13 for outputting an unbalanced mixed audio signal and outputting the unbalanced mixed audio signal to the phase-inverting mixed audio signal output module 11.

[0043] To provide power to the microphone 13, a mixed audio signal input circuit 14 is also included for outputting a mixed audio signal. This circuit includes resistors R7 and R8, and capacitors C6 and C7. The input terminal of the mixed audio signal is connected to resistor R7, the other end of resistor R7 is connected to resistor R8, the other end of resistor R8 is connected to a +3.3V power supply, the other end of resistor R7 is also connected to capacitor C6, the other end of capacitor C6 is grounded, and capacitor C7 is connected in parallel across capacitor C6.

[0044] The in-phase mixed audio signal output module 12 includes an operational amplifier U1B, resistors R9 and R10, capacitor C8, resistors R11 and R12, capacitor C9, a ferrite bead LB2, and capacitor C10. The positive input terminal of the operational amplifier U1B is connected to resistor R9, the other end of resistor R9 is connected to resistor R10, and the other end of resistor R10 is connected to a +12V power supply. The inverting input terminal of the operational amplifier U1B is connected to the output terminal of the operational amplifier U1A, and the signal output from the operational amplifier... A capacitor C8 and a resistor R11 are connected in sequence between the output terminal of amplifier U1A and the inverting input terminal of operational amplifier U1B; the two power supply terminals of operational amplifier U1B are connected to a +12V power supply and ground, respectively; a resistor R12 is connected between the inverting input terminal and the output terminal of operational amplifier U1B, and a capacitor C9 is connected in parallel across the two ends of the resistor R12; the output terminal of operational amplifier U1B is connected in sequence to a ferrite bead LB2 and a capacitor C10, and the other end of the capacitor C10 is connected to the IN1N pin of the FM1388 chip.

[0045] Furthermore, a capacitor C11 is connected between the resistor R10 and the resistor R9, and the other end of the capacitor C11 is grounded; the positive power supply terminal of the operational amplifier U1B is also connected to a capacitor C16, and the other end of the capacitor C16 is grounded.

[0046] Furthermore, the output terminal of the operational amplifier U1B is also connected to a resistor R13, and the other end of the resistor R13 is grounded.

[0047] The speaker audio signal processing module 20 is used to acquire speaker audio signals and output a set of return differential mixed audio signals to the echo cancellation module 30.

[0048] Specifically, it also includes a speaker 21 for outputting speaker audio signals and outputting the speaker audio signals to the speaker audio signal processing module 20.

[0049] The speaker audio signal processing module 20 includes a ferrite bead LB3, a resistor R14, a capacitor C12, a resistor R15, a capacitor C13, a capacitor C14, a resistor R16, a resistor R17, and a capacitor C15. One end of the ferrite bead LB3 is connected to the input terminal of the speaker audio signal, and the other end is connected sequentially to the resistor R14, the capacitor C12, and the resistor R15. The other end of the resistor R15 is connected to the IN2N pin of the FM1388 chip. The capacitor C13 is connected between the ferrite bead LB3 and the resistor R14. The other end of the capacitor C13 is connected sequentially to the capacitor C14 and the resistor R16. The other end of the resistor R16 is connected to the IN2P pin of the FM1388 chip. One end of the resistor R17 is connected between the resistor R14 and the capacitor C12, and the other end is connected between the capacitor C13 and the capacitor C14. The capacitor C15 is connected in parallel across the two ends of the resistor R17. The capacitors C13 and C14 are grounded.

[0050] Furthermore, it also includes a main control module, which is connected to the echo cancellation module 30. This main control module consists of a microprocessor and is used to control the echo cancellation module via I... 2 The C bus transmits data and commands.

[0051] Furthermore, it also includes a data transmission module, which is connected to the echo cancellation module 30 and is used to convert the analog audio received from the echo cancellation module 30 into digital audio and output it.

[0052] Furthermore, it also includes a power amplifier module, which is connected to the data transmission module. The power amplifier module is used to receive the low-level analog mixed audio signal output from the data transmission module and amplify it to drive the speaker to emit a sound of sufficient volume.

[0053] Furthermore, it also includes a power module (not shown), which includes a DC adapter or PoE that can output 12V power and can output 1.8V and 3.3V power through a step-down chip.

[0054] Specifically, the resistance values ​​of resistors R1, R9, R10, R14, R15, R16, and R17 are 1KΩ; the resistance values ​​of resistors R2, R3, R4, R9, R11, and R12 are 10KΩ; the resistance value of resistor R5 is 4.7KΩ; the resistance values ​​of resistors R6 and R13 are 47KΩ; and the resistance value of resistor R7 is 2.2KΩ.

[0055] Specifically, the capacitance values ​​of capacitors C1, C3, C8, C10, C12, and C14 are 4.7 μF; the capacitance values ​​of capacitors C2 and C9 are 56 pF; the capacitance values ​​of capacitors C4, C6, and C11 are 10 μF; the capacitance values ​​of capacitors C5, C7, and C16 are 0.1 μF; and the capacitance values ​​of capacitors C13 and C15 are 2.2 nF.

[0056] Specifically, the impedance of the magnetic beads LB1, LB2, and LB3 at 100MHz is 150Ω.

[0057] Compared with existing technologies, the adaptive echo cancellation circuit provided by this utility model can solve the problem of echo generation when speaking in existing intercom devices, which leads to poor user experience and improves sound clarity.

[0058] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments and claims of this application are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, “a plurality” means two or more; the terms “first,” “second,” “third,” etc., are used only to distinguish and not to describe a particular order or sequence, nor should they be construed as indicating or implying relative importance. The term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items. When the above description relates to drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of this application, those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0059] The embodiments described above are merely examples of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these modifications and improvements all fall within the protection scope of this utility model.

Claims

1. An adaptive echo cancellation circuit, characterized in that: It includes a mixed audio signal processing module, a speaker audio signal processing module, and an echo cancellation module, wherein the mixed audio signal processing module and the speaker audio signal processing module are both connected to the echo cancellation module; The hybrid audio signal processing module includes an inverted hybrid audio signal output module and an in-phase hybrid audio signal output module; The inverted mixed audio signal output module is used to acquire the mixed audio signal and output the inverted mixed audio signal to the in-phase mixed audio signal output module and the echo cancellation module; The in-phase mixed audio signal output module is used to output an in-phase mixed audio signal to the echo cancellation module based on the out-of-phase mixed audio signal; The speaker audio signal processing module is used to acquire the speaker audio signal and output a set of return differential mixed audio signals to the echo cancellation module.

2. The adaptive echo cancellation circuit according to claim 1, characterized in that: The inverted mixed audio signal output module includes an operational amplifier U1A, resistors R1, R2, and R3, capacitor C1, resistor R4, capacitor C2, and resistor R6. The positive input terminal of the operational amplifier U1A is connected to resistor R1, the other end of resistor R1 is connected to resistor R2, and the other end of resistor R2 is connected to a +12V power supply. The negative input terminal of the operational amplifier U1A is connected to resistor R3, the other end of resistor R3 is connected to capacitor C1, and the other end of capacitor C1 is connected to the input terminal of the mixed audio signal. The two power supply terminals of the operational amplifier U1A are connected to a +12V power supply and ground, respectively. A resistor R4 is connected in parallel between the negative input terminal and the output terminal of the operational amplifier U1A, and a capacitor C2 is also connected in parallel across the two ends of resistor R4. The output terminal of the operational amplifier U1A is connected in sequence to ferrite bead LB1 and capacitor C3, the other end of capacitor C3 is connected to the echo cancellation module. The output terminal of the operational amplifier U1A is also connected to resistor R6, the other end of which is grounded.

3. The adaptive echo cancellation circuit according to claim 2, characterized in that: A capacitor C4 is connected between resistors R1 and R2, with the other end of capacitor C4 grounded; the positive power supply terminal of operational amplifier U1A is also connected to capacitor C5, with the other end of capacitor C5 grounded.

4. The adaptive echo cancellation circuit according to claim 3, characterized in that: It also includes a mixed audio signal input circuit for outputting a mixed audio signal, which includes resistor R7, resistor R8, capacitor C6 and capacitor C7; The input terminal of the mixed audio signal is connected to the resistor R7, the other end of the resistor R7 is connected to the resistor R8, the other end of the resistor R8 is connected to the +3.3V power supply, the other end of the resistor R7 is also connected to the capacitor C6, the other end of the capacitor C6 is grounded, and the two ends of the capacitor C6 are also connected in parallel with the capacitor C7. The input terminal of the mixed audio signal is also connected to resistor R5, the other end of which is grounded.

5. The adaptive echo cancellation circuit according to claim 4, characterized in that: The in-phase mixed audio signal output module includes an operational amplifier U1B, resistors R9 and R10, capacitor C8, resistors R11 and R12, capacitor C9, a ferrite bead LB2, and capacitor C10. The positive input terminal of the operational amplifier U1B is connected to resistor R9, the other end of resistor R9 is connected to resistor R10, and the other end of resistor R10 is connected to a +12V power supply. The inverting input terminal of the operational amplifier U1B is connected to the output terminal of the operational amplifier U1A, and... A capacitor C8 and a resistor R11 are connected sequentially between the output terminal of operational amplifier U1A and the inverting input terminal of operational amplifier U1B; the two power supply terminals of operational amplifier U1B are connected to a +12V power supply and ground, respectively; a resistor R12 is connected between the inverting input terminal and the output terminal of operational amplifier U1B, and a capacitor C9 is connected in parallel across the two ends of the resistor R12; the output terminal of operational amplifier U1B is connected sequentially to a ferrite bead LB2 and a capacitor C10, and the other end of the capacitor C10 is connected to the echo cancellation module; A capacitor C11 is also connected between the resistor R10 and the resistor R9, and the other end of the capacitor C11 is grounded. The positive power supply terminal of the operational amplifier U1B is also connected to capacitor C16, and the other end of capacitor C16 is grounded. The output terminal of the operational amplifier U1B is also connected to a resistor R13, and the other end of the resistor R13 is grounded.

6. The adaptive echo cancellation circuit according to claim 5, characterized in that: The speaker audio signal processing module includes a ferrite bead LB3, a resistor R14, a capacitor C12, a resistor R15, a capacitor C13, a capacitor C14, a resistor R16, a resistor R17, and a capacitor C18. One end of the ferrite bead LB3 is connected to the input terminal of the speaker audio signal, and the other end is connected sequentially to the resistor R14, capacitor C12, and resistor R15. The other end of the resistor R15 is connected to the echo cancellation module. The capacitor C13 is connected between the ferrite bead LB3 and the resistor R14. The other end of the capacitor C13 is connected sequentially to the capacitor C14 and the resistor R16. The other end of the resistor R16 is connected to the echo cancellation module. One end of the resistor R17 is connected between the resistor R14 and the capacitor C12, and the other end is connected between the capacitor C13 and the capacitor C14. A capacitor C15 is connected in parallel across the two ends of the resistor R17. The capacitors C13 and C14 are grounded.

7. The adaptive echo cancellation circuit according to claim 6, characterized in that: The echo cancellation module is an FM1388 chip, which includes pins IN1N, IN1P, IN2N, and IN2P.

8. The adaptive echo cancellation circuit according to claim 7, characterized in that: The inverted mixed audio signal output module is connected to the IN1P pin of the FM1388 chip; The in-phase mixed audio signal output module is connected to the IN1N pin of the FM1388 chip; The output terminal of resistor R15 is connected to the IN2N pin of the FM1388 chip; The output terminal of resistor R16 is connected to the IN2P pin of the FM1388 chip.

9. The adaptive echo cancellation circuit according to claim 8, characterized in that: The resistance values ​​of resistors R1, R9, R10, R14, R15, R16, and R17 are 1KΩ; the resistance values ​​of resistors R2, R3, R4, R9, R11, and R12 are 10KΩ; the resistance value of resistor R5 is 4.7KΩ; the resistance values ​​of resistors R6 and R13 are 47KΩ; and the resistance value of resistor R7 is 2.2KΩ. The capacitance values ​​of capacitors C1, C3, C8, C10, C12, and C14 are 4.7 μF; the capacitance values ​​of capacitors C2 and C9 are 56 pF; the capacitance values ​​of capacitors C4, C6, and C11 are 10 μF; the capacitance values ​​of capacitors C5, C7, and C16 are 0.1 μF; and the capacitance values ​​of capacitors C13 and C15 are 2.2 nF. The impedance of the magnetic beads LB1, LB2, and LB3 at 100MHz is 150Ω.

10. The adaptive echo cancellation circuit according to claim 9, characterized in that: It also includes a main control module, which is connected to the echo cancellation module. The main control module is composed of a microprocessor and is used to transmit data and instructions via the I2C bus. and a data transmission module, wherein the data transmission module is connected to the echo cancellation module; The power amplifier module is connected to the data transmission module and is used to receive the low-level analog mixed audio signal output from the data transmission module and amplify it to drive the speaker to emit a sound of sufficient volume. The power module includes a DC adapter or PoE that can output 12V power and can output 1.8V and 3.3V power through a step-down chip.

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