Bioelectric potential acquisition system circuit and its signal processing method

Abstract

The present invention provides a bioelectric potential acquisition system circuit and a signal processing method thereof, which can enable the bioelectric potential acquisition system to have a smaller chip area and lower power consumption. A bioelectric potential acquisition system circuit provided by the present invention includes: an input node, wherein the input node is coupled to an electrode of the bioelectric potential acquisition system, and the electrode is used for contacting a human body; an electrode-tissue impedance (ETI) transmitter configured to generate a transmitter signal to the input node; and an analog front-end circuit coupled to the input node and configured to process an input signal from the input node to generate a digital signal, wherein each of the input signal and the digital signal includes an electrocardiogram (ECG) signal component and an ETI signal component.

Description

Technical Field

[0001] The present invention relates to the field of medical devices, and particularly to a bio-potential acquisition system circuit and a signal processing method thereof. Background Art

[0002] Traditional medical devices usually use large dry electrodes or wet electrodes to measure physiological signals to obtain physiological characteristics, such as bio-impedance or electrocardiography (ECG). In recent years, personal biosensors such as portable / wearable medical devices have become popular because they can provide physiological information at any time for users to refer to. Considering the use and design of these portable medical devices, smaller dry electrodes are more suitable. However, smaller dry electrodes mean poorer electrode impedance, and poorer electrode impedance (i.e., larger electrode impedance) may lead to detection errors of ECG signals. In addition, due to contact factors or motion artifacts, the Electrode-Tissue Impedance (ETI) may change greatly, thus increasing the difficulty of measuring ECG signals.

[0003] To solve the problems of ECG signals in the application of dry electrodes, the ETI is detected to reduce motion artifacts in the ECG signals. In the prior art, a current for ETI measurement is injected into the electrode, and the ETI receiver detects the voltage at the electrode to determine the ETI. Specifically, the ETI receiver may include a mixer, a low-pass filter, and an analog-to-digital converter (ADC), and the signal from the electrode is processed by the mixer, the low-pass filter, and the ADC in sequence to obtain ETI information. However, since the ETI receiver is an analog circuit, the chip area of the ETI receiver is large, the power consumption is high, and the mixer harmonics are poor. Therefore, the ETI receiver is not friendly to process scaling. Summary of the Invention

[0004] The present invention provides a bio-potential acquisition system circuit and a signal processing method thereof, which can make the bio-potential acquisition system have a smaller chip area and lower power consumption.

[0005] A bio-potential acquisition system circuit provided by the present invention includes: an input node, wherein the input node is coupled to an electrode of the bio-potential acquisition system, and the electrode is used for contacting a human body; an Electrode-Tissue Impedance (ETI) transmitter configured to generate a transmitter signal to the input node; and an analog front-end circuit coupled to the input node and configured to process an input signal from the input node to generate a digital signal, wherein each of the input signal and the digital signal includes an electrocardiogram (ECG) signal component and an ETI signal component.

[0006] A signal processing method for a biopotential acquisition system provided by the present invention includes: generating a transmitter signal to an input node for electrode-tissue impedance (ETI) measurement, where the input node is coupled to an electrode of the biopotential acquisition system, and the electrode is used to contact a human body; and using an analog front-end circuit to process an input signal from the input node to generate a digital signal, where each of the input signal and the digital signal includes an electrocardiogram (ECG) signal component and an ETI signal component.

[0007] Implementing the embodiments of the present invention can enable the biopotential acquisition system to have a smaller chip area and lower power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. is a diagram illustrating a biopotential acquisition system 100 according to an embodiment of the present invention.

[0009] Figure 2 FIG. is a schematic diagram of an analog front-end circuit 200 according to an embodiment of the present invention.

[0010] Figure 3 FIG. is a schematic diagram of an analog front-end circuit 300 according to another embodiment of the present invention.

[0011] Figure 4 FIG. is a flowchart of a signal processing method of a biopotential acquisition system 100 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] In the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in names as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. The terms "comprising" and "including" mentioned throughout the specification and claims are open-ended terms, and should be interpreted as "including but not limited to". "Substantially" or "about" means within an acceptable error range, and those skilled in the art can solve the technical problems within a certain error range and basically achieve the technical effects. In addition, the term "coupled" or "coupling" herein includes any direct and indirect electrical connection means. Therefore, if it is described in the text that a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means. The following describes the preferred embodiments of the present invention, aiming to illustrate the spirit of the present invention rather than to limit the protection scope of the present invention. The protection scope of the present invention shall be subject to what is defined by the claims.

[0013] The following description is the optimal embodiment expected by the present invention. These descriptions are used to illustrate the general principles of the present invention and are not used to limit the present invention. The protection scope of the present invention should be determined based on referring to the claims of the present invention.

[0014] Figure 1 FIG. is a diagram illustrating a biopotential acquisition system 100 according to an embodiment of the present invention. As Figure 1 shown, the biopotential acquisition system 100 is a two - electrode biopotential acquisition system having electrodes 102 and 104, and the electrodes 102 and 104 are respectively used to connect to the right body (such as the right hand) and the left body (such as the left hand) to acquire the biopotential signal of the human body. The biopotential acquisition system 100 can process and analyze the biopotential signal to determine physiological signals such as electrocardiogram signals, and display physiological characteristics on the screen of the biopotential acquisition system 100. In this embodiment, the biopotential acquisition system 100 can be built into any portable electronic device or wearable electronic device.

[0015] The biopotential acquisition system 100 includes input nodes N1 and N2, an ETI transmitter (in this embodiment, a digital - to - analog converter (DAC) 110 is used as the ETI transmitter), an analog front - end circuit 120, digital mixers 130 and digital filters 140, 150 and 160, where the analog front - end circuit 120 includes a low - noise amplifier 122, a low - pass filter 124, and an ADC 126; the DAC 110 can be implemented by any suitable DAC, such as a current DAC, a capacitor DAC, or a resistor DAC. When the electrodes 102 and 104 are connected to the human body, an ETI is formed, such that the biopotential acquisition system 100 may have a large input impedance, and the input impedance may change significantly due to contact factors or motion artifacts. In Figure 1 the illustrated embodiment, the ETI with the impedance of the electrodes 102 / 104 is modeled as a circuit in which a resistor R EL and a capacitor C EL are connected in parallel. In the operation of the biopotential acquisition system 100, when the electrodes 102 and 104 are in contact with the human body and the biopotential acquisition system 100 starts to measure the electrocardiogram signal, the digital - to - analog converter 110 receives a digital input signal Din to generate a transmitter signal to the electrodes 102 and 104. Then, the analog front - end circuit 120 receives input signals V IP and V IN (biopotential signals) from input nodes N1 and N2 respectively coupled to the electrodes 102 and 104 to generate information including an ECG signal and an ETI signal. Specifically, the low - noise amplifier 122 starts to receive input signals V IP and V IN(Bioelectric potential signals) are used to generate an amplified signal, where the input signals V IP and V IN include ECG signal and ETI signal information / components. Then, the low-pass filter 124 filters the amplified signal to generate a filtered signal. In one embodiment, the frequency of the transmitter signal generated by the DAC 110 is higher than the frequency of the ECG signal. For example, the frequency of the ECG signal may be lower than a few hundred Hertz, while the transmitter signal generated by the DAC 110 may be a few thousand Hertz. Therefore, the low-pass filter 124 can filter out components above a few thousand Hertz and retain the ECG signal components and ETI signal components within the amplified signal. Then, the ADC 126 performs an analog-to-digital conversion operation on the filtered signal to generate a digital signal.

[0016] The digital mixer 130 has an in-phase path and a quadrature path. The mixer in the in-phase path mixes the in-phase signal of the digital signal with mixer data having the same phase as the digital signal to generate an in-phase mixed signal, and the mixer in the quadrature path mixes the quadrature signal of the digital signal with mixer data having a phase orthogonal to the digital signal to generate a quadrature mixed signal. In this embodiment, the frequency of the mixer data is close to the frequency of the transmitter signal, such that the frequencies of the in-phase mixed signal and the quadrature mixed signal are lower. In addition, the digital mixer 130 can be a multi-bit digital mixer with good harmonics.

[0017] Furthermore, the phase lead and lag of the signal communication and processing from the DAC 110 to the input of the digital mixer 130 can be compensated by internal phase shift compensation at the analog front-end circuit 120 and the digital mixer 130 to obtain useful in-phase mixed signal and quadrature mixed signal.

[0018] The digital filter 140 filters the in-phase mixed signal generated by the digital mixer 130 to output an in-phase ETI signal ETI_I, and the digital filter 150 filters the quadrature mixed signal generated by the digital mixer 130 to output a quadrature ETI signal ETI_Q.

[0019] Meanwhile, since the ECG signal has a lower frequency, such as a few hundred Hertz, the digital filter 160 can directly receive the digital signal output by the ADC 126, that is, the digital signal has not undergone any mixer processing. The digital filter 160 filters out components above a few hundred Hertz to obtain an electrocardiogram signal.

[0020] Finally, the subsequent processing circuit (not shown) within the bioelectric potential acquisition system 100 can notify the user about the motion artifact problem or adjust / compensate the ECG signal generated by the ECG receiver 120 by using the ETI signal.

[0021] In the above embodiments, since the ECG signal and the ETI signal are processed simultaneously by the same analog front-end circuit 120, the ECG signal and the ETI signal do not need to be mixed first and then converted into digital signals, and the biopotential acquisition system 100 can have a smaller chip area and lower power consumption. In addition, since the digital mixer 130 is used for the mixing operation of digital signals, the mixer harmonics can be improved. In addition, the use of digital filters 140, 150, and 160 in the biopotential acquisition system 100 can reduce the chip area and the data rate.

[0022] In Figure 1 the illustrated embodiment, the analog front-end circuit 120 includes a low-noise amplifier 122, a low-pass filter 124, and an ADC 126, but the present invention is not limited thereto. Figure 2 is a schematic diagram of an analog front-end circuit 200 according to an embodiment of the present invention, where the analog front-end circuit 200 can be used to replace Figure 1 the illustrated analog front-end circuit 120. As Figure 2 shown, the analog front-end circuit 200 includes a low-noise amplifier 210 and an ADC 220, where the low-noise amplifier 210 is configured to receive input signals V IP and V IN (biopotential signals) from electrodes 102 and 104 to generate amplified signals, where the input signals V IP and V IN include information of the ECG signal and the ETI signal; the ADC 220 performs an analog-to-digital conversion operation on the amplified signal to generate a digital signal. Figure 3 is a schematic diagram of an analog front-end circuit 300 according to another embodiment of the present invention, where the analog front-end circuit 300 can be used to replace Figure 1 the illustrated analog front-end circuit 120. As Figure 3 shown, the analog front-end circuit 300 includes a low-pass filter 310 and an ADC 320, where the low-pass filter 310 filters the input signals V IP and V IN (biopotential signals) from electrodes 102 and 104 to generate a filtered signal. For example, the low-pass filter 310 can filter out components above several kilohertz and retain the ECG signal components and the ETI signal components in the input signals V IP and V IN ; the ADC 320 performs an analog-to-digital conversion operation on the filtered signal to generate a digital signal.

[0023] Figure 4 is a flowchart of a signal processing method of the biopotential acquisition system 100 according to an embodiment of the present invention. Referring simultaneously to Figure 1 andFigure 4 , the flowchart of the signal processing method is described as follows:

[0024] Step 400: The process starts.

[0025] Step 402: Generate a transmitter signal for ETI measurement to an input node, where the input node is coupled to an electrode of a biopotential acquisition system for contact with the human body.

[0026] Step 404: Process the input signal from the input node using an analog front-end circuit to generate a digital signal, where both the input signal and the digital signal include an ECG signal component and an ETI signal component.

[0027] Step 406: Mix the digital signal with mixer data to generate an in-phase mixed signal and a quadrature mixed signal, where the mixer data corresponds to the frequency of the transmitter signal, and the in-phase mixed signal and the quadrature mixed signal include an ETI signal component.

[0028] Step 408: Filter the in-phase mixed signal to generate an in-phase ETI signal, filter the quadrature mixed signal to generate a quadrature ETI signal, and filter the digital signal to generate an ECG signal.

[0029] In short, in the biopotential acquisition system of the present invention, only one analog front-end circuit is used to process two input signals, generate a digital signal including an ECG signal component and an ETI signal component, and the mixing operation and filtering operation for obtaining the ETI signal are performed in the digital domain. Therefore, the biopotential acquisition system has a smaller chip area and lower power consumption.

[0030] Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the scope of the present invention. Any person skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope defined by the claims.

Claims

1. A bioelectric potential acquisition system circuit, characterized in that, Comprising: An input node, wherein the input node is coupled to an electrode of the biopotential acquisition system, and the electrode is for contacting a human body; An electrode-tissue impedance transmitter configured to generate a transmitter signal to the input node; An analog front-end circuit coupled to the input node and configured to process an input signal from the input node to generate a digital signal, wherein each of the input signal and the digital signal includes an electrocardiogram signal component and an electrode-tissue impedance signal component; A digital filter configured to filter the digital signal to generate the electrocardiogram signal; And A digital mixer configured to mix the digital signal with mixer data to generate an in-phase mixed signal and a quadrature mixed signal, wherein the mixer data corresponds to the frequency of the transmitter signal, and the in-phase mixed signal and the quadrature mixed signal include electrode-tissue impedance signal components.

2. The bioelectric potential acquisition system circuit according to claim 1, characterized in that, The analog front-end circuit includes: An amplifier, wherein the amplifier amplifies the input signal to generate an amplified signal; A low-pass filter coupled to the amplifier and configured to filter the amplified signal to generate a filtered signal; and An analog-to-digital converter coupled to the low-pass filter for performing an analog-to-digital conversion operation on the filtered signal to generate the digital signal.

3. The bioelectric potential acquisition system circuit according to claim 1, characterized in that, The analog front-end circuit includes: An amplifier, wherein the amplifier amplifies the input signal to generate an amplified signal; and An analog-to-digital converter coupled to the amplifier and configured to perform analog-to-digital conversion on the amplified signal to generate the digital signal.

4. The bioelectric potential acquisition system circuit according to claim 1, wherein The analog front-end circuit includes: A low-pass filter configured to filter the input signal to generate a filtered signal; and An analog-to-digital converter coupled to the low-pass filter and configured to perform an analog-to-digital conversion operation on the filtered signal to generate a digital signal.

5. The bioelectric potential acquisition system circuit according to claim 1, characterized in that The digital filter is a first digital filter, and the biopotential acquisition system circuit further includes: A second digital filter coupled to the digital mixer and configured to filter the in-phase mixed signal to generate an in-phase electrode-tissue impedance signal; and A third digital filter coupled to the digital mixer and configured to filter the quadrature mixed signal to generate a quadrature electrode-tissue impedance signal.

6. A signal processing method for a biological potential acquisition system, characterized in that, Comprising: Generating a transmitter signal to the input node for electrode-tissue impedance measurement, wherein the input node is coupled to an electrode of the biopotential acquisition system, and the electrode is for contacting a human body; Using an analog front-end circuit to process an input signal from the input node to generate a digital signal, wherein each of the input signal and the digital signal includes an electrocardiogram signal component and an electrode-tissue impedance signal component; Filtering the digital signal to generate the electrocardiogram signal; And Mixing the digital signal with mixer data to generate an in-phase mixed signal and a quadrature mixed signal, wherein the mixer data corresponds to the frequency of the transmitter signal, and the in-phase mixed signal and the quadrature mixed signal include electrode-tissue impedance signal components.

7. The signal processing method of the biopotential acquisition system according to claim 6, characterized in that, The step of using an analog front-end circuit to process an input signal from the input node to generate a digital signal includes: Amplifying the input signal to generate an amplified signal; Filter the amplified signal to generate a filtered signal; and Perform an analog-to-digital conversion operation on the filtered signal to generate the digital signal.

8. The signal processing method of the biopotential acquisition system according to claim 6, characterized in that, The step of using the analog front-end circuit to process the input signal from the input node to generate a digital signal includes: Amplify the input signal to generate an amplified signal; and Perform an analog-to-digital conversion operation on the amplified signal to generate the digital signal.

9. The signal processing method of the biopotential acquisition system according to claim 6, characterized in that, The step of using the analog front-end circuit to process the input signal from the input node to generate a digital signal includes: Filter the input signal to generate a filtered signal; and Perform an analog-to-digital conversion operation on the filtered signal to generate the digital signal.

10. The signal processing method of the biopotential acquisition system according to claim 6, wherein, Further includes: Filter the in-phase mixed signal to generate an in-phase electrode-tissue impedance signal; and Filter the quadrature mixed signal to generate a quadrature electrode-tissue impedance signal.

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