WO2019085029A1

WO2019085029A1 - Dual-microphone noise reduction and echo cancellation circuit

Info

Publication number: WO2019085029A1
Application number: PCT/CN2017/111067
Authority: WO
Inventors: 伍泽良
Original assignee: 深圳市浩博高科技有限公司
Priority date: 2017-10-30
Filing date: 2017-11-15
Publication date: 2019-05-09
Also published as: CN107734429A; CN107734429B

Abstract

A dual-microphone noise reduction and echo cancellation circuit comprises a first microphone (MK1), a second microphone (MK2) and a signal superposition circuit. The circuit uses two microphones (MK1, MK2) having the same sensitivity and impedance to form two completely identical circuits, and when the two microphones (MK1, MK2) receive the same acoustic wave, the two sampling signals have opposite phases and the same amplitude, and the two signals can cancel each other out by means of the superposing of the signal superposition circuit, being equivalent to an operational amplifier subtracting circuit. The circuit cancels the operational amplifier, so that the working voltage of the whole circuit is reduced, and the overall current consumption is reduced, thereby achieving the purposes of reducing the cost and simplifying the circuit, and miniaturizing the product as the number of the components is reduced.

Description

Double microphone noise reduction echo circuit

Technical field

The present invention relates to the field of electronic circuit technologies, and in particular, to a dual microphone noise reduction echo circuit.

Background technique

The microphone is microphone and Mic.

At present, there are two main methods for noise reduction or echo cancellation. One is through multi-channel MIC sampling and processed by software algorithms. This kind of CPU requires a relatively high computing power, high cost, and large power consumption, and is not suitable for use in consumer electronics products for dry batteries. The other is the hardware circuit implementation, using dual-micron sampling, after subtracting the circuit composed of op amps, the signals of the two MICs are subtracted. The operating voltage of the op amp on the market is mostly above 3V, with two dry batteries. Powered products can only work with new batteries, or add booster chips, and the overall power consumption is large. There are many circuit devices, which is inconvenient for miniaturization of products and high cost.

Summary of the invention

In order to solve the above technical problems, an object of the present invention is to provide a dual-microphone noise reduction echo circuit having a simple structure and low cost.

The technical solution adopted by the present invention is: a dual microphone noise reduction echo circuit comprising a first microphone, a second microphone and a signal superposition circuit, wherein a positive pole of the first microphone is connected to an input end of the signal superposition circuit The negative terminal of the second microphone is connected to the input end of the signal superposition circuit.

Further, the signal superimposing circuit includes a fifth resistor and a thirteenth resistor, and a positive pole of the first microphone is connected to one end of the thirteenth resistor through the fifth resistor, and the other end of the thirteenth resistor Connected to the negative pole of the second microphone.

Further, the signal superimposing circuit further includes a fourth resistor and a fourteenth resistor, one end of the fourth resistor is connected to the power source, and the other end of the fourth resistor is connected to the anode of the first microphone, and one end of the fourteenth resistor Connected to the ground, the other end of which is connected to the negative pole of the second microphone.

Further, it further includes a sixth capacitor and a tenth capacitor, wherein a cathode of the first microphone is connected to an input end of the signal superposition circuit through a sixth capacitor, and a cathode of the second microphone passes through a tenth capacitor and the signal The input terminals of the superposition circuit are connected.

Further, it further includes a low pass filter circuit, the input of which is connected to the output of the signal superimposing circuit.

Further, the low pass filter circuit includes a sixth resistor and an eleventh capacitor, one end of the sixth resistor is connected to an output end of the signal superposition circuit, and the other end is used as an output end and passes through the eleventh capacitor Connected to the ground.

Further, it further includes an amplifying circuit, and an output end of the low pass filter circuit is connected to an input end of the amplifying circuit.

Further, the amplifying circuit includes a MOS transistor and its peripheral circuits.

The invention has the beneficial effects that the invention adopts two microphones with the same sensitivity and impedance, and is connected into two identical circuits. One way is used for sound source collection, and the other is used for ambient sound collection. One way to collect the signal from the positive side of the microphone, the other way to take the signal from the negative side of the microphone. When the two microphones receive the same sound wave, the two sampling signals are opposite in phase and have the same amplitude. By superimposing these two signals through the signal superposition circuit, they can cancel each other, which is equivalent to the effect of the op amp subtraction circuit. Because this circuit cancels the op amp, and the working voltage of the microphone only needs to be above 1V, the working voltage of the whole circuit is also reduced. It only needs 1.5V power supply to work normally, because the power consumption of the op amp is reduced, the overall current Consumption is also reduced. Thus, the cost is reduced, the purpose of the circuit is simplified, and the power supply and power consumption problems of the products powered by the dry battery are solved. Due to the reduction in devices, the product can be further miniaturized.

DRAWINGS

The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings:

Figure 1 is a circuit diagram of the present invention;

Figure 2 is a circuit schematic of the present invention.

Detailed ways

It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict.

As shown in FIG. 1 , a dual microphone noise reduction echo circuit includes a first microphone, a second microphone, and a signal superposition circuit, and a positive pole of the first microphone is connected to an input end of the signal superposition circuit. The negative electrode of the second microphone is connected to the input terminal of the signal superposition circuit.

The invention uses two microphones with the same sensitivity and impedance to be connected into two identical circuits. One way is used for sound source collection, and the other is used for ambient sound collection. The first signal collects a signal from the positive side of the first microphone, and the second signal collects a signal from the negative side of the second microphone. When the two microphones receive the same sound wave, the two sampling signals are opposite in phase and have the same amplitude. By superimposing these two signals through the signal superposition circuit, they can cancel each other, which is equivalent to the effect of the op amp subtraction circuit.

Further as a preferred embodiment, the circuit further includes a low pass filter circuit, and an input end of the low pass filter circuit is connected to an output end of the signal superposition circuit.

The vocal frequency is within 1KHZ, and the ambient noise frequency is 20HZ~20KHZ. The sound transmission speed is 340 m / sec. In practical applications, two MIC placements are more elegant, when two MICs When the distance is 34cm, the received ambient noise time differs by 1ms. When the two MICs are separated by 3.4CM, the received ambient noise time differs by 100us. That is to say, if the two MICs are separated by 3.4CM, the two electrical signals sampled by the noise of 10KHZ will be completely misaligned. In order to solve this problem, a low-pass wave circuit is added to the circuit to take the noise frequency above 1KHZ into consideration. In addition, in the MIC layout, one MIC can be placed at the same position on the front and back of the device. The distance between the two MICs is about 1CM, and the time difference between the two MICs receiving the sound is only 29us, and the sound with the frequency below 1KHZ can be ignored.

Because the ambient noise source is far from the MIC, the sounds received by the two MICs are basically the same, and will be offset or over-considered. Because the MIC direction is opposite to the device casing, when the MIC of the sound source is close to the sound source being recorded, the sound intensity of the MIC of the sound source is much stronger than the MIC of the ambient noise, so that the sound can be recorded normally. Can be offset or over-considered.

Further as a preferred embodiment, the method further includes an amplifying circuit, and an output end of the low pass filter circuit is connected to the signal output port through an amplifying circuit. The amplifying circuit includes a MOS transistor and its peripheral circuits. The effective signal after passing through the low-pass filter circuit is amplified by the amplifying circuit.

Example 1

As shown in FIG. 2, a circuit schematic diagram of a specific embodiment of the present invention is shown. Hereinafter, various portions of each circuit will be described in detail.

The positive pole of the first microphone MK1 passes through the resistor R3 and the power supply MIC BIAS connection, the negative pole of which is connected to the ground through the resistor R2; the anode of the second microphone MK2 passes the resistor R12 and the power supply MIC The BIAS is connected, and the negative electrode thereof is connected to the ground through a resistor R11. In this embodiment, the first microphone MK1 and the second microphone MK2 are both electret microphones.

The signal superimposing circuit includes a fifth resistor R5 and a thirteenth resistor R13. The anode of the first microphone MK1 is connected to the fifth resistor R5 through the sixth capacitor C6, and the other end of the fifth resistor R5 is connected to the sixth resistor R6. The negative terminal of the second microphone MK2 is connected to one end of the thirteenth resistor R13 through the tenth capacitor C10, and the other end of the thirteenth resistor R13 is connected to the sixth resistor R6.

The signal superimposing circuit further includes a fourth resistor R4 and a fourteenth resistor R14, and one end of the fourth resistor R4 and the power source MIC The other end of the BIAS is connected to the fifth resistor R5, one end of which is connected to the ground, and the other end of which is connected to the thirteenth resistor R13.

The low pass filter circuit includes a sixth resistor R6 and an eleventh capacitor C11, one end of the sixth resistor R6 is connected to an output end of the signal superposition circuit, and the other end is used as an output end and passes the eleventh Capacitor C11 is connected to ground.

Use two microphones with the same sensitivity and impedance (MK1 MK2), the positive and negative poles of the microphone are connected in series with a resistor of the same resistance (resistor R3, resistor R2, resistor R12, resistor) R11), and then separately connected to the power supply and ground, connected to two identical circuits. One way is used for sound source collection, and the other is used for environmental noise collection. The signal is collected from the anode of the first microphone MK1 through the sixth capacitor C6, and the signal is taken from the cathode of the second microphone MK2 through the tenth capacitor C10. When the two microphones receive the same sound wave, the two sampling signals are opposite in phase and have the same amplitude. When the two microphones receive the same ambient noise, points E and F get a signal with the opposite phase and the same amplitude, and point A is the output point of the two signals in equal proportions, and there is no change signal output. When the sound source signal is input from the first microphone MK1, the E point has a stronger sound source signal, and the second microphone MK2 receives a weaker sound source signal, while the F point sound source signal is weaker, two ways. The signals do not cancel each other at point A, so the sound source signal is output.

The above is a detailed description of the preferred embodiments of the present invention, but the present invention is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the invention. Such equivalent modifications or alternatives are intended to be included within the scope of the claims.

Claims

A dual microphone noise reduction echo circuit, comprising: a first microphone, a second microphone and a signal superposition circuit, wherein a positive pole of the first microphone is connected to an input end of the signal superposition circuit, and the second A negative pole of the microphone is coupled to an input of the signal superposition circuit.
The dual microphone noise reduction echo circuit according to claim 1, wherein said signal superimposing circuit comprises a fifth resistor and a thirteenth resistor, and said anode of said first microphone passes said fifth resistor and said One end of the thirteenth resistor is connected, and the other end of the thirteenth resistor is connected to a cathode of the second microphone.
The dual-microphone noise reduction and cancellation circuit according to claim 2, wherein the signal superimposing circuit further comprises a fourth resistor and a fourteenth resistor, wherein one end of the fourth resistor is connected to the power source, and the other end is connected to The anode of the first microphone is connected, one end of the fourteenth resistor is connected to the ground, and the other end of the fourteenth resistor is connected to the cathode of the second microphone.
The dual microphone noise reduction echo circuit according to any one of claims 1 to 3, further comprising a sixth capacitor and a tenth capacitor, wherein a positive pole of the first microphone passes through the sixth capacitor and the signal An input terminal of the superposition circuit is connected, and a cathode of the second microphone is connected to an input end of the signal superposition circuit through a tenth capacitor.
The dual microphone noise reduction echo circuit according to claim 4, further comprising a low pass filter circuit, wherein an input end of the low pass filter circuit is connected to an output end of the signal superposition circuit.
The dual-microphone noise reduction echo circuit according to claim 5, wherein said low-pass filter circuit comprises a sixth resistor and an eleventh capacitor, and one end of said sixth resistor and an output of said signal superimposing circuit The other end is connected as an output terminal and connected to the ground through the eleventh capacitor.
The dual microphone noise reduction echo circuit according to claim 6, further comprising an amplification circuit, an output end of said low pass filter circuit being coupled to an input end of said amplification circuit.
The dual microphone noise reduction echo circuit according to claim 7, wherein said amplifying circuit comprises a MOS transistor and a peripheral circuit thereof.