Undisturbed weak signal acquisition circuit

Abstract

The invention discloses an undisturbed weak signal acquisition circuit, which comprises a power supply management unit, and an analog front-end acquisition unit, an electrostatic protection unit, an analog front-end amplification and filtering unit and a digital circuit unit which are connected in sequence, carrying out isolation processing on the physiological signals; the electrostatic protection unit is used for realizing electrostatic protection in a signal acquisition process; the analog front end amplifying and filtering unit is used for performing amplifying, filtering and analog-to-digital conversion processing on the collected physiological signals so as to reduce noise interference; the digital circuit unit is used for carrying out artifact removal processing on the digitized physiological signals to obtain pure physiological signals; the power management unit is used for providing working voltage for other units. The method can greatly improve the quality of weak physiological signals in the time domain and the frequency domain, and has great advantages in the aspects of system anti-noise, common-mode rejection ratio, power supply stability, filtering effect and the like.

Description

Technical Field

[0001] The invention relates to the field of signal acquisition, and in particular to a non-intrusive weak signal acquisition circuit. Background Art

[0002] Information technology is related to the lifeblood of a country. Brain-computer interface is one of the key development directions in the future fields of warfare, medical treatment, and control. How to more accurately collect weak signals from the human body's front end is one of the main problems currently faced.

[0003] In recent years, certain achievements have been made in the collection of weak human signals (electroencephalogram, electrocardiogram, cardiac shock, breathing, transcranial magnetic resonance imaging, etc.). However, these achievements usually only collect a single signal for research, without taking into account the complementarity between multiple signals, and it is impossible to collect multiple signals simultaneously without interference. Summary of the invention

[0004] The purpose of the present invention is to provide a non-intrusive weak signal acquisition circuit to overcome the problems existing in existing signal acquisition solutions in terms of complementarity and anti-interference.

[0005] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0006] A non-intrusive weak signal acquisition circuit comprises a power management unit and an analog front-end acquisition unit, an electrostatic protection unit, an analog front-end amplification and filtering unit and a digital circuit unit connected in sequence, wherein:

[0007] The analog front-end acquisition unit is used to collect human physiological signals and isolate the physiological signals; the electrostatic protection unit is used to implement electrostatic protection in the signal acquisition process; the analog front-end amplification and filtering unit is used to amplify, filter and perform analog-to-digital conversion on the collected physiological signals to reduce noise interference; the digital circuit unit is used to remove artifacts from the digitized physiological signals to obtain pure physiological signals; the power management unit is used to provide working voltage for other units.

[0008] Furthermore, the analog front-end acquisition unit includes an acquisition electrode and a signal isolation unit, wherein the acquisition electrode is arranged at a part to be collected on the human body to collect physiological signals, and the signal isolation unit is arranged on each acquisition electrode, and the signal isolation unit adopts an optical coupling isolation method to achieve isolation between physiological signals.

[0009] Furthermore, the electrostatic protection unit is connected to the collection electrode and the power management unit, and the electrostatic protection unit uses an ESD device to perform electrostatic protection on the physiological signal collection process.

[0010] Furthermore, the analog front-end amplification and filtering unit includes an instrument amplifier circuit, a common-mode suppression circuit, a DC servo circuit, a low-pass filter circuit, a double-T notch filter, and an analog-to-digital converter.

[0011] Furthermore, the instrument amplifier circuit includes an operational amplifier A 1 and A 2 , Differential Amplifier A 3 , resistor RG, resistor R 1 To R 6 ,in:

[0012] Operational Amplifier A 1 The positive input terminal V IN1 Access the physiological signals collected by each collection electrode, A 2 The positive input terminal V IN2 Access the reference ground signal; A 1 The output end is connected to the resistor R 1 , R 2 And output the unamplified signal V S , A 2 The output end is connected to the resistor R 3 , R 4 And output reference signal V B ; R 5 Connect in A 1 The negative input terminal and A 1 Between the output terminals, R 6 Connect in A 2 The negative input terminal and A 2 Between the output terminals, the resistor R G Set the resistor R 5 , resistor R 6 Between; differential amplifier A 3 The negative input terminal is connected to the resistor R 1 , R 2 Between 3 The positive input terminal is connected to the resistor R 3 , R 4 Between; A 3 The output signal V is obtained at the output end A .

[0013] Furthermore, the common mode suppression circuit comprises: an operational amplifier A 4 , A 5 , A 6 , resistor R 7 To R 17 , capacitor C 1 To C 5 ,in:

[0014] A 4The negative input terminal is connected through the resistor R 7 , R 10 Access the input signal V A , A 4 The positive input terminal is connected through the resistor R 8 , R 9 Access the reference signal V B , A 4 The output terminal is connected through the capacitor C 4 Output signal V after removing common mode signal C ; Resistance R 11 , R 12 After connecting in series, R 13 At both ends, R 13 Connect both ends of A 4 Positive and negative output terminals; A 5 The positive input terminal is connected to R 11 , R 12 Between 5 The negative input terminal is connected to A 5 The output terminal, A 5 The output terminal is connected through the resistor R 17 Connect to A 6 The negative input terminal, A 6 The positive input terminal of A is grounded. 6 The output terminal is connected through the resistor R 15 , R 16 Then use electrodes to connect to the human body; resistor R 14 Connect in A 6 Between the negative input and output terminals, capacitor C 5 In parallel with R 14 Two ends; capacitor C 2 One end is connected to R 7 and A 4 Connect capacitor C between the negative input terminals 1 One end, C 1 The other end of the capacitor C 2 The other end is connected to R 8 and A 4 Connect capacitor C between the positive input terminals 3 One end, C 3 The other end is grounded.

[0015] Furthermore, the DC servo circuit includes an operational amplifier A 7 and A 8 , resistor R 18 To R 23 , capacitor C 6 , C 7 , where: A 7 The positive input terminal is connected to the signal V after the common mode signal is removed.C , the output terminal passes through the resistor R 20 Then the output signal V is obtained after the DC component is removed. D ; A 7 The negative input terminal is connected through the resistor R 22 Connect in A 8 The output terminal, A 7 The output terminal is connected through the resistor R 21 Connect in A 8 The positive input terminal is connected to the capacitor C 6 One end, C 6 The other end of the resistor R 23 One end is grounded and the other end is connected to A 8 The negative input terminal, capacitor C 7 Connect in A 8 The negative input terminal and A 8 Between the output terminals; resistor R 18 One end is grounded and the other end is connected to the resistor R 19 Connect the resistor R 21 and A 7 between the output terminals.

[0016] Furthermore, the low-pass filter circuit includes an operational amplifier A 9 and A 10 , resistor R 24 To R 29 , feedback resistor R f1 and R f2 , capacitor C 8 To C 11 ,in:

[0017] A 9 The negative input terminal is connected through the resistor R 26 grounded and through the feedback resistor R f1 Connection A 9 The output terminal of A 9 The positive input terminal is connected through the resistor R 25 , R 24 Then access the output signal V to remove the DC component D , capacitor C 8 One end is connected to A 9 The positive input terminal of the capacitor C 9 One end is connected to R 24 , R 25 The other end is connected to A 9 The output terminal of A 9 The output terminal passes through the resistor R 27 , R 28 After connecting A 10 The positive input terminal, capacitor C 10 One end is connected to A10 The positive input terminal of the capacitor C 11 One end is connected to R 27 , R 28 The other end is connected to A 10 The output terminal of A 10 The negative input terminal is connected through the resistor R 29 grounded and through the feedback resistor R f2 Connection A 10 The output terminal, A 10 The output terminal outputs the physiological signal V after low-pass filtering. E .

[0018] Furthermore, the double-T type notch filter comprises an operational amplifier A 11 and A 12 , resistor R 30 To R 34 , capacitor C 12 To C 14 ,in:

[0019] The signal after low-pass filtering V E Through capacitor C 12 , C 13 Then connect to A 11 The positive input terminal, A 11 The negative input terminal is connected to A 11 The output terminal, A 11 The output terminal outputs the physiological signal V after filtering out the power frequency interference out ; A 11 The output terminal passes through the resistor R 33 , R 34 Rear grounding, A 12 The positive input terminal is connected to R 33 , R 34 Between 12 The negative input terminal is connected to A 12 The output terminal; the resistor R 30 , capacitor C 14 And the resistor R 32 After connecting in series, connect in parallel at C 12 Both ends of R 31 One end is connected to R 30 , the other end is connected to A 11 The positive input terminal; A 12 The output terminal is connected to C 14 With R 32 between.

[0020] Furthermore, the digital circuit unit includes a microcontroller, a data transmission unit and a terminal host computer, wherein:

[0021] The microcontroller sends the digitized physiological signal after analog-to-digital conversion to the data transmission unit according to the specified frame protocol, and the data transmission unit wirelessly sends the physiological signal to the terminal host computer for artifact removal processing, including:

[0022] The area with artifacts in the physiological signal is screened out, and the wavelet decomposition is performed on this area to reconstruct the artifacts in this area. The Kalman filter is then used to predict and correct the artifacts in this area. Finally, the calibrated artifacts are subtracted from this area to obtain the final pure physiological signal.

[0023] Furthermore, first, a detection threshold is set, each sampling point of the physiological signal is compared with the detection threshold, and the part exceeding the threshold is marked, and all marked sampling points constitute the area where the artifact exists;

[0024] Secondly, wavelet multi-scale decomposition is performed on the area with artifacts to reconstruct the signal; in the wavelet multi-scale decomposition, db4 wavelet is selected as the mother wavelet to decompose the signal into 4 layers;

[0025] Finally, the AR model is used to represent the artifacts in the artifact area, and then the spatial state equation is established and the Kalman filter algorithm is used to predict the artifacts to obtain pure artifacts; the pure artifacts are subtracted from the area where the physiological signal has artifacts to obtain a pure physiological signal.

[0026] Compared with the prior art, the present invention has the following technical features:

[0027] Compared with the prior art, the present invention has made relevant targeted designs for weak signal acquisition, which can greatly improve the quality of weak signals in the time domain and frequency domain. It is expected to have great advantages in system noise resistance, common mode rejection ratio, power supply stability and filtering effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A circuit diagram of a data acquisition circuit of the present invention;

[0029] Figure 2 The circuit diagram of the instrument amplifier circuit;

[0030] Figure 3 This is a circuit diagram of a common mode rejection circuit;

[0031] Figure 4 is a circuit diagram of a DC servo circuit;

[0032] Figure 5 is the circuit diagram of the low-pass filter circuit;

[0033] Figure 6 It is the circuit diagram of the double-T trap;

[0034] Figure 7 This is a schematic diagram of the design of the power management unit;

[0035] Figure 8 Schematic diagram of the signal artifact removal process. DETAILED DESCRIPTION

[0036] Referring to the accompanying drawings, the present invention provides a non-intrusive weak signal acquisition circuit, comprising a power management unit and an analog front-end acquisition unit, an electrostatic protection unit, an analog front-end amplification and filtering unit and a digital circuit unit connected in sequence, wherein:

[0037] The analog front-end acquisition unit is used to collect human physiological signals and isolate the physiological signals; the electrostatic protection unit is used to implement electrostatic protection in the signal acquisition process; the analog front-end amplification and filtering unit is used to amplify, filter and perform analog-to-digital conversion on the collected physiological signals to reduce noise interference; the digital circuit unit is used to remove artifacts from the digitized physiological signals to obtain pure physiological signals; the power management unit is used to provide working voltage for other units.

[0038] 1. Analog front-end acquisition unit

[0039] The analog front-end acquisition unit includes acquisition electrodes and a signal isolation unit, wherein the acquisition electrodes are arranged at the part to be collected on the human body to collect physiological signals, for example, they are arranged on the human frontal lobe to collect three-lead EEG signals, or they are arranged on the chest to collect two-lead ECG signals.

[0040] The signal isolation unit is arranged on each acquisition electrode, and the signal isolation unit adopts an optical coupling isolation method to achieve isolation between physiological signals, so as to increase the anti-interference ability of the entire acquisition circuit.

[0041] 2. Electrostatic protection unit

[0042] The electrostatic protection unit is connected to the collection electrode and the power management unit. The electrostatic protection unit adopts ESD devices to perform electrostatic protection on the physiological signal collection process.

[0043] The human body can generate static electricity with a voltage of tens to tens of thousands of volts in daily activities and production operations. The discharge process is extremely short, and the energy released during the discharge process can reach tens of watts. This static electricity can damage any commonly used semiconductor device, so an electrostatic protection unit must be added to the front-end design. This solution adds ESD devices to the front end of the collection electrode and the power management unit. When the instantaneous voltage exceeds a certain range due to static interference, it can effectively filter out the static interference in the signal.

[0044] 3. Analog front-end amplifier and filter unit

[0045] According to the characteristics of weak, low-frequency and unstable human physiological signals, the present invention designs an analog front-end amplification and filtering unit, including an instrument amplifier circuit, a common-mode suppression circuit, a DC servo circuit, a low-pass filter circuit, a double-T notch filter, and an analog-to-digital converter, wherein:

[0046] (1) Instrument amplifier circuit

[0047] All weak physiological signals collected by the collection electrodes can be equivalent to the differential signal input between two points. Physiological signals have the characteristics of small amplitude, high input impedance, and large common-mode signal. It is necessary to design an instrument amplifier circuit with ultra-high input impedance as the input stage. According to the impedance matching principle, in order to avoid signal attenuation, the impedance of the operational amplifier should be as high as possible. The instrument amplifier circuit can suppress common-mode signals and increase input impedance. The circuit is as follows: Figure 2 shown.

[0048] The instrument amplifier circuit includes an operational amplifier A 1 and A 2 , Differential Amplifier A 3 , resistor RG, resistor R 1 To R 6 ,in:

[0049] Operational Amplifier A 1 The positive input terminal V IN1 Access the physiological signals collected by each collection electrode, A 2 The positive input terminal V IN2 Access the reference ground signal; A 1 The output end is connected to the resistor R 1 , R 2 And output the unamplified signal V S , A 2 The output end is connected to the resistor R 3 , R 4 And output reference signal V B ; R 5 Connect in A 1 The negative input terminal and A 1 Between the output terminals, R 6 Connect in A 2 The negative input terminal and A 2 Between the output terminals, the resistor R G Set the resistor R 5 , resistor R 6 Between; differential amplifier A 3 The negative input terminal is connected to the resistor R 1 , R 2 Between 3 The positive input terminal is connected to the resistor R 3 , R 4 Between; A3 The output signal V is obtained at the output end A .

[0050] In this circuit, the input stage adopts the same-direction input mode, which is composed of operational amplifier A 1 and A 2 According to the "virtual short" and "virtual open" principles of ideal op amps, the current I flowing into the same direction end IN1 and I IN2 Both are approximately equal to 0A, so the input impedance of the two amplifiers R = V IN1 / I IN1 =V IN1 / I IN1 , meeting the impedance matching requirements. And when the input stage adopts the differential input method, it has a good suppression ability for common mode signals, so it can effectively increase the common mode rejection ratio. Output stage A 3 It is a differential amplifier used to realize differential amplification of signals; the output signal V A That is the signal output to the next stage, V B is the reference signal; the unamplified signal V S It can be regarded as the original physiological signal, which is not needed in the subsequent circuit of this scheme; but in actual application, the microcontroller can send the signal to the terminal host computer for signal analysis and verification.

[0051] (2) Common mode suppression circuit

[0052] In order to further process the common-mode signal, a common-mode suppression circuit is designed in this solution, such as Figure 3 As shown, it includes: operational amplifier A 4 , A 5 , A 6 , resistor R 7 To R 17 , capacitor C 1 To C 5 ,in:

[0053] A 4 The negative input terminal is connected through the resistor R 7 , R 10 Access the input signal V A , A 4 The positive input terminal is connected through the resistor R 8 , R 9 Access the reference signal V B , A 4 The output terminal is connected through capacitor C 4 Output signal V after removing common mode signal C ; Resistance R 11 , R 12 After connecting in series, R 13 At both ends, R13 Connect both ends of A 4 Positive and negative output terminals; A 5 The positive input terminal is connected to R 11 , R 12 Between 5 The negative input terminal is connected to A 5 The output terminal, A 5 The output terminal is connected through the resistor R 17 Connect to A 6 The negative input terminal, A 6 The positive input terminal of A is grounded. 6 The output terminal is connected through the resistor R 15 , R 16 Then use electrodes to connect to the human body; resistor R 14 Connect in A 6 Between the negative input and output terminals, capacitor C 5 In parallel with R 14 Two ends; capacitor C 2 One end is connected to R 7 and A 4 Connect capacitor C between the negative input terminals 1 One end, C 1 The other end of the capacitor C 2 The other end is connected to R 8 and A 4 Connect capacitor C between the positive input terminals 3 One end, C 3 The other end is grounded.

[0054] The common-mode rejection circuit is equivalent to a closed-loop feedback excitation link. At the midpoint of the gain setting resistor R 11 , R 12 , the common mode signal collected in the middle of the driving circuit design is transmitted through the follower A 5 After inversion and passing through A 6 After being amplified by a certain multiple, it is fed back to the human body through electrodes to offset the common-mode signal. After removing the common-mode signal, V C The signal is output to the next stage.

[0055] (3) DC servo circuit

[0056] In order to further filter the DC signal, the DC servo circuit adds a low-pass filter and a co-directional amplifier circuit on the basis of the traditional reverse integration circuit. The connection between the control current formed by the servo loop and the amplifier loop needs to have an appropriate phase relationship to achieve the effect of correcting the offset, otherwise it will be counterproductive.

[0057] like Figure 4 As shown, the DC servo circuit includes an operational amplifier A7 and A 8 , resistor R 18 To R 23 , capacitor C 6 , C 7 , where: A 7 The positive input terminal is connected to the signal V after the common mode signal is removed. C , the output terminal passes through the resistor R 20 Then the output signal V is obtained after the DC component is removed. D ; A 7 The negative input terminal is connected through the resistor R 22 Connect in A 8 The output terminal, A 7 The output terminal is connected through the resistor R 21 Connect in A 8 The positive input terminal is connected to the capacitor C 6 One end, C 6 The other end of the resistor R 23 One end is grounded and the other end is connected to A 8 The negative input terminal, capacitor C 7 Connect in A 8 The negative input terminal and A 8 Between the output terminals; resistor R 18 One end is grounded and the other end is connected to the resistor R 19 Connect the resistor R 21 and A 7 between the output terminals.

[0058] In this circuit, A 7 , R 18 , R 19 The same-direction amplifier is formed, C 6 , R 21 A forms a low-pass filter. 8 , C 7 , R 23 Constitute a reverse integration circuit; input signal V C First pass through op amp A 7 The DC signal is amplified in the same direction through R 21 Later enter op amp A 8 The same-direction input terminal, and then through the integration circuit C 7 , R 22 Return to Op Amp A 7 The inverting input terminal, input signal V C After the difference between the DC component and the 7 Amplify the output and reach dynamic balance after a period of time; the output signal V D Output to the next stage, V D The DC component is no longer included.

[0059] (4) Low-pass filter circuit

[0060] In the process of low-pass filtering of signals, group delay is a priority indicator for designing the corresponding filter. In the process of data transmission, if the signals of various frequencies can maintain the same delay, the frequency components of the useful signal will eventually produce the same output delay, and all frequency components will not be output distorted.

[0061] like Figure 5 As shown, the low-pass filter circuit of the present invention includes an operational amplifier A 9 and A 10 , resistor R 24 To R 29 , feedback resistor R f1 and R f2 , capacitor C 8 To C 11 ,in:

[0062] A 9 The negative input terminal is connected through the resistor R 26 grounded and through the feedback resistor R f1 Connection A 9 The output terminal of A 9 The positive input terminal is connected through the resistor R 25 , R 24 Then access the output signal V to remove the DC component D , capacitor C 8 One end is connected to A 9 The positive input terminal of the capacitor C 9 One end is connected to R 24 , R 25 The other end is connected to A 9 The output terminal of A 9 The output terminal passes through the resistor R 27 , R 28 After connecting A 10 The positive input terminal, capacitor C 10 One end is connected to A 10 The positive input terminal of the capacitor C 11 One end is connected to R 27 , R 28 The other end is connected to A 10 The output terminal of A 10 The negative input terminal is connected through the resistor R 29 grounded and through the feedback resistor R f2 Connection A 10 The output terminal, A 10 The output terminal outputs the physiological signal V after low-pass filtering. E .

[0063] (5) Double T notch filter

[0064] Power frequency signals can greatly interfere with the acquisition and processing of electrical signals. Therefore, it is far from enough to simply design a low-pass filter. It is also necessary to further filter out the power frequency interference that exists in large quantities in life. Power frequency interference is generally only a specific 50Hz or 60Hz. In my country, it is mainly 49.5Hz-50.5Hz power frequency interference. In the time domain, it is manifested as a superposition of useful signals and sine waves. If the power frequency interference is not filtered out before entering the ADC, the mixed signal will exceed the dynamic range of the ADC, resulting in signal distortion. Therefore, before the physiological signal enters the analog-to-digital converter, the 50Hz power frequency must be further removed in a targeted manner.

[0065] The present invention adopts a double T-type notch filter for power frequency interference, such as Figure 6 As shown, including operational amplifier A 11 and A 12 , resistor R 30 To R 34 , capacitor C 12 To C 14 ,in:

[0066] The signal after low-pass filtering V E Through capacitor C 12 , C 13 Then connect to A 11 The positive input terminal, A 11 The negative input terminal is connected to A 11 The output terminal, A 11 The output terminal outputs the physiological signal V after filtering out the power frequency interference out ; A 11 The output terminal passes through the resistor R 33 , R 34 Rear grounding, A 12 The positive input terminal is connected to R 33 , R 34 Between 12 The negative input terminal is connected to A 12 The output terminal; the resistor R 30 , capacitor C 14 And the resistor R 32 After connecting in series, connect in parallel at C 12 Both ends of R 31 One end is connected to R 30 , the other end is connected to A 11 The positive input terminal; A 12 The output terminal is connected to C 14 With R 32 between.

[0067] The basic principle of this circuit is to eliminate the power frequency interference by passing the input signal through the frequency selection network, feedback circuit and operational amplifier. 11 Used as a voltage amplifier, A 12 Used as a voltage follower, A 12 Increase the quality factor of the entire circuit, making the system closer to the center frequency f 0 When it is closer, it starts to decay. 33 , R 34 The frequency selection network is formed by adjusting R 33 , R 34 The resistance value sets the bandwidth BW and quality factor Q. The larger the Q value, the narrower the band stop and the better the filtering effect. However, the Q value cannot be too large, otherwise it will cause unstable oscillation of the circuit. out That is the final physiological signal after signal processing.

[0068] (5) Analog-to-digital converter

[0069] The analog-to-digital converter is used to convert the physiological signal V after filtering out the power frequency interference out Converted into a digital signal and input into a digital circuit unit for subsequent processing; the analog-to-digital converter in this embodiment uses the ADS1299 chip.

[0070] 4. Power Management Unit

[0071] like Figure 7 As shown in the figure, power management is related to whether the entire acquisition circuit can work normally; considering the wearability of the entire system, the power management unit is powered by a lightweight lithium battery. After analysis, the entire system requires 5 DC powers of different amplitudes: 5V for charging the lithium battery; 3.3V for powering digital circuit units, Bluetooth, ADC, etc.; -3.7V with polarity reversal; ±2.5V to provide a reference voltage for operational amplifiers and analog-to-digital converters; and the lithium battery discharge voltage is a variable value, so appropriate voltage conversion is required to ensure the entire unit.

[0072] 5. Digital circuit unit

[0073] The digital circuit unit includes a microcontroller, a data transmission unit and a terminal host computer, wherein:

[0074] The microcontroller uses the STM32F407 series chip, which is mainly responsible for signal transmission control; the microcontroller converts the digitized physiological signal V out According to the specified frame protocol, the data transmission unit sends the physiological signal V out The signal is sent wirelessly to the terminal host computer for subsequent signal processing.

[0075] In this embodiment, the microcontroller and the analog-to-digital converter are connected in the form of a four-wire SPI bus, and data transmission and control are performed between the microcontroller and the data transmission unit via a serial port; the data transmission unit uses a BT200 Bluetooth module.

[0076] The physiological signals collected and processed by the signal acquisition circuit and transmitted to the terminal host computer through wireless contain a lot of redundant information. The physiological signals mainly contain other signal artifacts, so it is necessary to further remove the corresponding artifact interference. Other signal artifacts are received during the acquisition process. At the same time, since the artifacts do not appear regularly, when designing the artifact removal algorithm, it is not necessary to remove the artifacts of all channels to reduce the complexity of the algorithm.

[0077] See also Figure 8 In the terminal host computer, the physiological signal V received from the digital circuit unit out Perform the following processing:

[0078] The region with artifacts in the physiological signal is screened out, and the region is decomposed by wavelet to reconstruct the artifacts in the region. Then, the Kalman filter is used to predict and correct the artifacts in the region. Finally, the calibrated artifacts are subtracted from the region to obtain the final pure physiological signal. The specific instructions are as follows:

[0079] First, a detection threshold is set, and each sampling point of the physiological signal is compared with the detection threshold. The part exceeding the threshold is marked, and all marked sampling points constitute the area where the artifact exists. This area can be extended forward and backward in the time domain to a certain length so that the area can cover the entire signal with artifacts.

[0080] Secondly, wavelet multi-scale decomposition is performed on the areas where artifacts exist to reconstruct the signal; in the wavelet multi-scale decomposition, db4 wavelet is selected as the mother wavelet; since the sampling rate in the hardware design is 250HZ, the bandwidth of different components is selected according to the sampling rate and wavelet decomposition scale. When the signal is decomposed into 4 layers, the approximate layer basically contains all the rough artifacts.

[0081] Finally, after the 4-layer wavelet decomposition, the reconstructed artifacts also contain useful signal components with lower frequencies. Therefore, the AR model is used to represent the artifacts in the artifact area. Then, the spatial state equation is established and the Kalman filter algorithm is used to predict the artifacts to obtain pure artifacts. The pure artifacts are subtracted from the area where the physiological signal has artifacts to obtain a pure physiological signal.

[0082] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A non-intrusive weak signal acquisition circuit, characterized in that: It includes a power management unit and an analog front-end acquisition unit, an electrostatic protection unit, an analog front-end amplification and filtering unit, and a digital circuit unit connected in sequence, wherein: The analog front-end acquisition unit is used to collect human physiological signals and isolate the physiological signals; the electrostatic protection unit is used to implement electrostatic protection in the signal acquisition process; the analog front-end amplification and filtering unit is used to amplify, filter and perform analog-to-digital conversion on the collected physiological signals to reduce noise interference; the digital circuit unit is used to remove artifacts from the digitized physiological signals to obtain pure physiological signals; the power management unit is used to provide working voltage for other units.

2. The non-intrusive weak signal acquisition circuit according to claim 1, characterized in that: The analog front-end acquisition unit includes an acquisition electrode and a signal isolation unit, wherein the acquisition electrode is arranged at a part of the human body to be collected for physiological signal acquisition, and the signal isolation unit is arranged on each acquisition electrode. The signal isolation unit uses an optical coupling isolation method to achieve isolation between physiological signals.

3. The non-intrusive weak signal acquisition circuit according to claim 1, characterized in that: The analog front-end amplification and filtering unit includes an instrument amplifier circuit, a common-mode suppression circuit, a DC servo circuit, a low-pass filtering circuit, a double-T notch filter, and an analog-to-digital converter.

4. The non-intrusive weak signal acquisition circuit according to claim 3, characterized in that: The instrument amplifier circuit includes operational amplifiers A1 and A2, a differential amplifier A3, a resistor RG, and resistors R1 to R6, wherein: The positive input terminal of operational amplifier A1 is V IN1 The positive input terminal V of A2 is connected to the physiological signals collected by each collection electrode. IN2 Connect the reference ground signal; the output end of A1 is connected to resistors R1 and R2 in sequence and outputs the unamplified signal V S , the output end of A2 is connected to resistors R3 and R4 in sequence and outputs the reference signal V B ; R5 is connected between the negative input terminal of A1 and the output terminal of A1, R6 is connected between the negative input terminal of A2 and the output terminal of A2, and the resistor R G Set between resistors R5 and R6; the negative input terminal of the differential amplifier A3 is connected between resistors R1 and R2, and the positive input terminal of A3 is connected between resistors R3 and R4; the output terminal of A3 obtains the output signal V A .

5. The non-intrusive weak signal acquisition circuit according to claim 3, characterized in that: The common mode suppression circuit includes: operational amplifiers A4, A5, A6, resistors R7 to R 17 , capacitors C1 to C5, where: The negative input of A4 is connected through resistors R7 and R 10 Access the input signal V A The positive input of A4 is connected to the reference signal V through resistors R8 and R9. B The output of A4 outputs the signal V after removing the common mode signal through capacitor C4. C ; Resistance R 11 , R 12 After connecting in series, R 13 At both ends, R 13 The two ends of A4 are connected to the positive and negative output terminals; the positive input terminal of A5 is connected to R 11 , R 12 The negative input of A5 is connected to the output of A5, and the output of A5 is connected to the output of A5 through the resistor R 17 Connected to the negative input of A6, the positive input of A6 is grounded, and the output of A6 is connected to the negative input of A6 through the resistor R 15 , R 16 Then use electrodes to connect to the human body; resistor R 14 Connected between the negative input terminal and the output terminal of A6, capacitor C5 is connected in parallel with R 14 Two ends; one end of capacitor C2 is connected between R7 and the negative input terminal of A4 and connected to one end of capacitor C1, and the other end of C1 is grounded; the other end of capacitor C2 is connected between R8 and the positive input terminal of A4 and connected to one end of capacitor C3, and the other end of C3 is grounded.

6. The non-intrusive weak signal acquisition circuit according to claim 1, characterized in that: The DC servo circuit includes operational amplifiers A7 and A8, resistor R 18 To R 23 , capacitors C6 and C7, where the positive input of A7 is connected to the signal V after the common mode signal is removed. C , the output terminal passes through the resistor R 20 Then the output signal V is obtained after the DC component is removed. D ; The negative input of A7 is connected through resistor R 22 Connected to the output of A8, the output of A7 is connected through the resistor R 21 Connected to the positive input terminal of A8 and connected to one end of capacitor C6, the other end of C6 is grounded; resistor R 23 One end of is grounded, and the other end is connected to the negative input terminal of A8. Capacitor C7 is connected between the negative input terminal of A8 and the output terminal of A8. Resistor R 18 One end is grounded and the other end is connected to the resistor R 19 Connect the resistor R 21 and the output of A7.

7. The non-intrusive weak signal acquisition circuit according to claim 3, characterized in that: The low-pass filter circuit includes operational amplifiers A9 and A 10 , resistor R 24 To R 29 , feedback resistor R f1 and R f2 , capacitors C8 to C 11 ,in: The negative input of A9 is connected through resistor R 26 grounded and through the feedback resistor R f1 Connect the output of A9; the positive input of A9 is connected through the resistor R 25 , R 24 Then access the output signal V to remove the DC component D , one end of capacitor C8 is connected to the positive input terminal of A9, and the other end is grounded; one end of capacitor C9 is connected to R 24 , R 25 The other end is connected to the output of A9; the output of A9 is connected through the resistor R 27 , R 28 After connecting A 10 The positive input terminal, capacitor C 10 One end is connected to A 10 The positive input terminal of the capacitor C 11 One end is connected to R 27 , R 28 The other end is connected to A 10 The output terminal of A 10 The negative input terminal is connected through the resistor R 29 grounded and through the feedback resistor R f2 Connection A 10 The output terminal, A 10 The output terminal outputs the physiological signal V after low-pass filtering. E .

8. The non-intrusive weak signal acquisition circuit according to claim 3, characterized in that: The double-T notch filter includes an operational amplifier A 11 and A 12 , resistor R 30 To R 34 , capacitor C 12 To C 14 ,in: The signal after low-pass filtering V E Through capacitor C 12 , C 13 Then connect to A 11 The positive input terminal, A 11 The negative input terminal is connected to A 11 The output terminal, A 11 The output terminal outputs the physiological signal V after filtering out the power frequency interference out ; A 11 The output terminal passes through the resistor R 33 , R 34 Rear grounding, A 12 The positive input terminal is connected to R 33 , R 34 Between 12 The negative input terminal is connected to A 12 The output terminal; resistor R 30 , capacitor C 14 And the resistor R 32 After connecting in series, connect in parallel at C 12 Both ends of R 31 One end is connected to R 30 , the other end is connected to A 11 The positive input terminal; A 12 The output terminal is connected to C 14 With R 32 between.

9. The non-intrusive weak signal acquisition circuit according to claim 1, characterized in that: The digital circuit unit includes a microcontroller, a data transmission unit and a terminal host computer, wherein: The microcontroller sends the digitized physiological signal after analog-to-digital conversion to the data transmission unit according to the specified frame protocol, and the data transmission unit wirelessly sends the physiological signal to the terminal host computer for artifact removal processing, including: The area with artifacts in the physiological signal is screened out, and the wavelet decomposition is performed on this area to reconstruct the artifacts in this area. The Kalman filter is then used to predict and correct the artifacts in this area. Finally, the calibrated artifacts are subtracted from this area to obtain the final pure physiological signal.

10. The non-intrusive weak signal acquisition circuit according to claim 1, characterized in that: First, a detection threshold is set, and each sampling point of the physiological signal is compared with the detection threshold. The part exceeding the threshold is marked, and all marked sampling points constitute the area where the artifact exists; Secondly, wavelet multi-scale decomposition is performed on the area with artifacts to reconstruct the signal; in the wavelet multi-scale decomposition, db4 wavelet is selected as the mother wavelet to decompose the signal into 4 layers; Finally, the AR model is used to represent the artifacts in the artifact area, and then the spatial state equation is established and the Kalman filter algorithm is used to predict the artifacts to obtain pure artifacts; the pure artifacts are subtracted from the area where the physiological signal has artifacts to obtain a pure physiological signal.

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