Anti-interference ADC biopotential sampling system and sampling method

Abstract

The invention relates to an anti-interference ADC (Analog to Digital Converter) biopotential sampling system, which solves the contradiction that a small-dynamic-range ADC is easy to saturate and a large-dynamic-range ADC is high in cost through time division multiplexing of a high-range ADC and a low-range ADC in combination with a signal compensation technology, and realizes the unification of a wide dynamic range and high-frequency signal fidelity. The first ADC processing branch firstly measures main components of signals and generates compensation signals, the second ADC processing branch carries out fine measurement on residual signals, after the two branches are superposed, the overall dynamic range of the system is expanded, and signal saturation or detail loss caused by range limitation of a single ADC is effectively avoided; on the premise that the real-time performance of signals is guaranteed, high signal-to-noise ratio and wide-range compatible accurate sampling is achieved with low hardware cost, and the invention further provides an anti-interference ADC biopotential sampling method.

Description

Technical Field

[0001] The present invention relates to the technical field of brain-computer interface bioelectric signal acquisition, and in particular to an interference-resistant ADC bioelectrical potential sampling system and sampling method. Background Art

[0002] When collecting bioelectric signals from a brain-computer interface, there are various noises in the environment, among which the most common is power frequency noise (around 50HZ or 60HZ).

[0003] When using an ADC (analog-to-digital converter) with a large dynamic range, digital filtering can be used to remove noise. However, large dynamic range ADCs are expensive and slow to acquire data. When using an ADC with a small dynamic range and an operational amplifier (OPA) for data acquisition, various environmental noises are likely to cause the ADC range to saturate. Simply adding an analog filter also fails to meet the requirements in complex noisy environments.

[0004] Therefore, it is necessary to propose an acquisition system and method for complex noise environments that uses a small dynamic range ADC to expand the dynamic range while only caring about frequency domain signals without affecting measurement accuracy. Summary of the Invention

[0005] Based on the above description, the present invention provides a method to solve the technical problems in the prior art.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] An anti-interference ADC biopotential sampling system includes a signal amplification unit, a first ADC processing branch, a second ADC processing branch, a DAC, and a switch;

[0008] The signal amplification unit is used to amplify and perform impedance conversion on the initial bioelectric signal to generate an initial amplified signal. The first ADC processing branch is provided with a first ADC, and the second ADC processing branch is provided with a second ADC. The range of the first ADC is greater than the range of the second ADC. The output end of the signal amplification unit is connected to the switching switch, and the switching switch is used to alternately connect the output end of the signal amplification unit to the first ADC processing branch and the second ADC processing branch.

[0009] When the switch connects the output end of the signal amplifying unit to the first ADC processing branch, the initial amplified signal is input to the first ADC processing branch and processed by the first ADC to obtain a first voltage.

[0010] The DAC generates a compensation signal according to the first voltage;

[0011] When the switching switch connects the output end of the signal amplifying unit to the second ADC processing branch, the initial amplified signal and the compensation signal are input into the second ADC processing branch and processed by the second ADC, and a second voltage is measured. The sum of the first voltage and the second voltage is the total voltage.

[0012] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0013] The ADC biopotential sampling system provided in this application solves the contradiction between the easy saturation of small dynamic range ADCs and the high cost of large dynamic range ADCs by time-sharing multiplexing high and low range ADCs and combining signal compensation technology, and realizes the unity of wide dynamic range and high-frequency signal fidelity. The first ADC processing branch first measures the main components of the signal and generates a compensation signal, and the second ADC processing branch performs a fine measurement of the residual signal. The superposition of the two expands the overall dynamic range of the system, effectively avoiding signal saturation or detail loss caused by the range limitation of a single ADC; under the premise of ensuring the real-time performance of the signal, accurate sampling with high signal-to-noise ratio and wide range compatibility is achieved at a low hardware cost.

[0014] On the basis of the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, the signal amplification unit includes at least one of a programmable gain amplifier, a voltage-controlled gain amplifier, a digital-to-analog converter combined with a fixed gain amplifier, and a digital potentiometer combined with an operational amplifier.

[0016] Furthermore, the signal amplification unit is a programmable gain amplifier, and the gain coefficient of the programmable gain amplifier is dynamically adjusted through an automatic gain control technology to adapt to the amplitude range of the input signal.

[0017] Furthermore, the switching switch includes at least one of a signal range switching switch, a multiplexer, and a discrete relay.

[0018] Furthermore, the first ADC processing branch includes a first operational amplifier and a first ADC connected in sequence.

[0019] Furthermore, the second ADC processing branch includes a DAC, a differential operational amplifier, a second operational amplifier and a second ADC, the differential operational amplifier having a first input terminal and a second input terminal, the output terminal of the DAC is connected to the first input terminal, and the second input terminal is used to be connected to the switching switch, the differential operational amplifier, the second operational amplifier and the second ADC are connected in sequence, and the amplification factor of the second operational amplifier is greater than the amplification factor of the first operational amplifier.

[0020] Furthermore, the dynamic range of the DAC is the same as the dynamic range of the first ADC, and is used to form a compensation signal.

[0021] Furthermore, the measurement range of the second ADC is greater than the quantization accuracy of the first ADC.

[0022] The present application also provides an anti-interference ADC biopotential sampling method, which includes the following steps:

[0023] S1, amplifying and impedance converting the initial bioelectric signal to generate an initial amplified signal;

[0024] S2, measuring the initial amplified signal after performing a first analog-to-digital conversion to obtain a first voltage;

[0025] S3, generating a compensation signal according to the first voltage through digital-to-analog conversion, and performing a second analog-to-digital conversion on the initial amplified signal and the compensation signal to obtain a second voltage by measurement;

[0026] S4. Add the first voltage and the second measurement result to obtain a large dynamic range voltage of the initial bioelectric signal.

[0027] Furthermore, the method further comprises:

[0028] S5. Filtering out the offset voltage and temperature drift of the large dynamic range voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic structural diagram of an anti-interference ADC biopotential sampling system provided by an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of the steps of an interference-resistant ADC biopotential sampling method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0031] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings provide embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present application more thorough and comprehensive.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0033] It will be understood that spatial relational terms such as "under", "beneath", "below", "under", "above", "above", etc., may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It will be understood that in addition to the orientations shown in the figures, spatial relational terms also include different orientations of the device in use and operation. For example, if the device in the drawings is turned over, the element or feature described as "under the other elements" or "under it" or "below it" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include alternative orientations (e.g., rotated 90° or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0034] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediate element. In the following embodiments, "connection" should be understood as "electrical connection", "communication connection", etc., if the connected circuits, modules, units, etc. can transmit electrical signals or data to each other.

[0035] When used herein, the singular forms "a", "an", and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0036] In order to have a correct and comprehensive understanding of the technical solution of the present invention, the relevant principles of the technical solution of this application are first explained as follows:

[0037] We all know that in biopotential acquisition, bioelectric signals (such as electrocardiogram and electroencephalogram) appear as weak voltage changes, and noise appears as random voltage changes such as voltage fluctuations. When a small bioelectric signal is superimposed on noise with a large dynamic range, an initial amplified signal with a large dynamic range is formed. The noise can currently be filtered out through various digital filtering methods, but it should not exceed the dynamic range of the ADC during ADC analog-to-digital conversion.

[0038] Then we can assume that the voltage of a certain initial amplified signal with a large dynamic range at a certain moment is V0. This voltage V0 can be regarded as the sum of a larger voltage V1 and a smaller voltage V2, that is, V0 = V1 + V2. Then, two ADCs with a dynamic range lower than the dynamic range of the initial amplified signal are used to measure these two voltages V1 and V2 respectively, and then the two are added together to obtain the true voltage of the initial amplified signal. Subsequently, the noise is removed by filtering to obtain the true bioelectric signal.

[0039] Therefore, the technical solution of this application is implemented as follows:

[0040] An anti-interference ADC biopotential sampling system includes a signal amplification unit 10, a first ADC processing branch 20, a second ADC processing branch 30, a DAC 40 and a switch 50;

[0041] The signal amplification unit is used for amplifying the initial bioelectric signal and performing impedance transformation to generate an initial amplified signal.

[0042] In an optional embodiment of the present application, the signal amplification unit that can be used to amplify and impedance transform the initial bioelectric signal to generate the initial amplified signal can be a programmable gain amplifier PGA, a voltage-controlled gain amplifier VGA, a digital-to-analog converter DAC combined with a fixed gain amplifier, a digital potentiometer combined with an operational amplifier, etc. In this embodiment, the signal amplification unit 10 is a programmable gain amplifier PGA.

[0043] The gain coefficient of the programmable gain amplifier (PGA) is dynamically adjusted to match the input signal's amplitude range via automatic gain control (AGC). AGC is a closed-loop control technique that dynamically adjusts the amplifier's gain to maintain a stable output signal amplitude. Its core purpose is to ensure the output signal remains within the target range when the input signal amplitude varies significantly, avoiding saturation due to excessively strong signals or signal-to-noise ratio degradation due to excessively weak signals. This technology is a mature technique for adjusting the gain coefficient of programmable gain amplifiers (PGAs) and will not be elaborated on here.

[0044] The first ADC processing branch 20 is provided with a first ADC21, and the second ADC processing branch 30 is provided with a second ADC31. The range of the first ADC21 is greater than the range of the second ADC31. ADC, or analog-to-digital converter, is an electronic component used to convert analog signals into digital signals. The range represents the input voltage range that the ADC can measure. Signal voltages exceeding this range will cause saturation or truncation.

[0045] It can be seen here that the first ADC21 is an analog-to-digital converter with a larger range, and the second ADC31 is an analog-to-digital converter with a smaller range, so that the large voltage is measured through the first ADC processing branch 20 and the small voltage is measured through the second ADC processing branch 30.

[0046] The output end of the programmable gain amplifier PGA is connected to the switching switch, and the switching switch is used to alternately connect the output end of the programmable gain amplifier PGA to the first ADC processing branch 20 and the second ADC processing branch 30, thereby realizing time-division multiplexing of the two ADCs.

[0047] In the optional embodiments of the present application, there are many options for the switching switch 50, such as a signal range switching switch, a multiplexer, and a discrete relay. It only needs time to switch the initial amplified signal to two different ADC processing branches in a time-sharing manner. In this embodiment, the switching switch 50 is preferably a signal range switching switch, which dynamically switches the signal path in the circuit and guides the input signal to measurement channels of different ranges.

[0048] When the signal range switch connects the output end of the programmable gain amplifier PGA to the first ADC processing branch 20 , the initial amplified signal is input to the first ADC processing branch 20 and processed by the first ADC 21 to obtain a first voltage.

[0049] The DAC 40 generates a compensation signal according to the first voltage. The dynamic range of the DAC 40 is the same as the dynamic range of the first ADC 21 , and is used to form a compensation signal that completely matches the first voltage.

[0050] When the signal range switching switch connects the output end of the programmable gain amplifier PGA to the second ADC processing branch 30, the initial amplified signal and the compensation signal are input into the second ADC processing branch 30 and processed by the second ADC 31, and a second voltage is measured. The sum of the first voltage and the second voltage is the total voltage.

[0051] In an embodiment of the present application, the first ADC processing branch 20 includes a first operational amplifier 22 and a first ADC 21 connected in sequence.

[0052] The second ADC processing branch 30 includes a differential operational amplifier 32, a second operational amplifier 33 and a second ADC 31. The differential operational amplifier 32 has a first input terminal 32a and a second input terminal 32b. The output terminal of the DAC 40 is connected to the first input terminal 32a, and the second input terminal 32b is used to connect to the signal range switching switch. The differential operational amplifier 32, the second operational amplifier 31 and the second ADC 31 are connected in sequence, wherein the amplification factor of the second operational amplifier is greater than the amplification factor of the first operational amplifier.

[0053] The differential operational amplifier 32 performs precise differential operation on the compensation signal generated by DAC40 and the initial amplified signal, effectively offsetting the previous stage measurement error and system offset. The second operational amplifier 33 adopts a higher amplification factor to perform secondary amplification on the residual signal after differentiation, so that the details of the weak signal can fully cover the input range of the second ADC31, thereby maximizing the use of the ADC resolution while ensuring non-saturation. Through this two-stage amplification architecture design, it avoids the noise and distortion problems easily introduced by a single-stage high-gain amplifier, and ensures the system's high-precision acquisition capability of small-amplitude bioelectric signals, ultimately achieving the unity of wide dynamic range and high resolution.

[0054] In a preferred embodiment of the present application, the measurement range of the second ADC 31 is greater than the quantization accuracy of the first ADC 21 .

[0055] Ensure that the residual signal after quantization by the first ADC21 can fall completely within the range of the second ADC31, avoid the secondary truncation error caused by the residual signal exceeding the range of the second ADC31, and at the same time, make each quantization step of the second ADC31 accurately correspond to the quantization error of the first ADC21, thereby achieving seamless splicing in the digital domain and ensuring that the total synthesized signal has no range gap or overlap.

[0056] Based on the above sampling system, this embodiment proposes an anti-interference ADC biopotential sampling method, which is characterized by comprising the following steps:

[0057] S1, amplifying and impedance converting the initial bioelectric signal to generate an initial amplified signal;

[0058] According to the above embodiment, a programmable gain amplifier (PGA) is used to amplify and impedance-convert the initial bioelectric signal to generate an initial amplified signal;

[0059] S2, measuring the initial amplified signal after performing a first analog-to-digital conversion to obtain a first voltage;

[0060] That is, the output end of the programmable gain amplifier PGA is connected to the first ADC processing branch 20 through the signal range switching switch, the initial amplified signal is amplified by the first operational amplifier 22 and then enters the first ADC 21 for the first analog-to-digital conversion, and then the first voltage V1 is measured.

[0061] S3, generating a compensation signal according to the first voltage through digital-to-analog conversion, and performing a second analog-to-digital conversion on the initial amplified signal and the compensation signal to obtain a second voltage by measurement;

[0062] That is, the output end of the programmable gain amplifier PGA is connected to the second ADC processing branch 30 through the signal range switching switch, and the digital signal corresponding to the first voltage V1 is converted into an analog compensation signal through the DAC40 to form an analog compensation signal, which is then input into the differential operational amplifier 32 together with the initial amplified signal. The differential operational amplifier 32 performs a precise differential operation on the compensation signal generated by the DAC40 and the initial amplified signal. The second operational amplifier 33 performs a secondary amplification on the residual signal after the differential, and then enters the second ADC31 for the first analog-to-digital conversion, and then measures to obtain the second voltage V2.

[0063] S4. Add the first voltage and the second measurement result to obtain a large dynamic range voltage of the initial bioelectric signal.

[0064] The first voltage V1 plus the second voltage V2 is added to obtain the real voltage V0, which has a larger dynamic range than V1 and V2.

[0065] S5. Filtering out the offset voltage and temperature drift of the large dynamic range voltage.

[0066] For example, a high-pass filter can be used to filter out offset voltage and temperature drift to obtain a more accurate and effective bioelectric signal voltage.

[0067] The system and method provided in this embodiment resolve the contradiction between the easy saturation of small dynamic range ADCs and the high cost of large dynamic range ADCs by time-sharing multiplexing high- and low-range ADCs and combining them with signal compensation technology, thus achieving the unity of wide dynamic range and high-frequency signal fidelity. The first ADC processing branch first measures the main components of the signal and generates a compensation signal, while the second ADC processing branch performs a refined measurement of the residual signal. The superposition of the two expands the overall dynamic range of the system, effectively avoiding signal saturation or detail loss caused by the range limitation of a single ADC. While ensuring the real-time performance of the signal, precise sampling with a high signal-to-noise ratio and wide range compatibility is achieved at a low hardware cost.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An anti-interference ADC biopotential sampling system, characterized in that: It includes a signal amplifying unit, a first ADC processing branch, a second ADC processing branch, a DAC and a switch; The signal amplification unit is used to amplify and perform impedance conversion on the initial bioelectric signal to generate an initial amplified signal. The first ADC processing branch is provided with a first ADC, and the second ADC processing branch is provided with a second ADC. The range of the first ADC is greater than the range of the second ADC. The output end of the signal amplification unit is connected to the switching switch, and the switching switch is used to alternately connect the output end of the signal amplification unit to the first ADC processing branch and the second ADC processing branch. When the switch connects the output end of the signal amplifying unit to the first ADC processing branch, the initial amplified signal is input to the first ADC processing branch and processed by the first ADC to obtain a first voltage. The DAC generates a compensation signal according to the first voltage; When the switching switch connects the output end of the signal amplifying unit to the second ADC processing branch, the initial amplified signal and the compensation signal are input into the second ADC processing branch and processed by the second ADC, and a second voltage is measured. The sum of the first voltage and the second voltage is the total voltage.

2. The anti-interference ADC biopotential sampling system according to claim 1, characterized in that: The signal amplifying unit includes at least one of a programmable gain amplifier, a voltage-controlled gain amplifier, a digital-to-analog converter combined with a fixed gain amplifier, and a digital potentiometer combined with an operational amplifier.

3. The anti-interference ADC biopotential sampling system according to claim 2, characterized in that: The signal amplification unit is a programmable gain amplifier, and the gain coefficient of the programmable gain amplifier is dynamically adjusted through automatic gain control technology to adapt to the amplitude range of the input signal.

4. The anti-interference ADC biopotential sampling system according to claim 1, characterized in that: The switching switch includes at least one of a signal range switching switch, a multiplexer, and a discrete relay.

5. The anti-interference ADC biopotential sampling system according to any one of claims 1 to 4, characterized in that: The first ADC processing branch includes a first operational amplifier and a first ADC connected in sequence.

6. The anti-interference ADC biopotential sampling system according to claim 5, characterized in that: The second ADC processing branch includes a differential operational amplifier, a second operational amplifier, and a second ADC. The differential operational amplifier has a first input terminal and a second input terminal. The output terminal of the DAC is connected to the first input terminal, and the second input terminal is used to be connected to the switching switch. The differential operational amplifier, the second operational amplifier, and the second ADC are connected in sequence. The amplification factor of the second operational amplifier is greater than the amplification factor of the first operational amplifier.

7. The anti-interference ADC biopotential sampling system according to claim 6, characterized in that: The dynamic range of the DAC is the same as the dynamic range of the first ADC, and is used to form a compensation signal.

8. The anti-interference ADC biopotential sampling system according to claim 5, characterized in that: The measurement range of the second ADC is greater than the quantization accuracy of the first ADC.

9. An anti-interference ADC biopotential sampling method, characterized in that: The steps include: S1, amplifying and impedance converting the initial bioelectric signal to generate an initial amplified signal; S2, measuring the initial amplified signal after performing a first analog-to-digital conversion to obtain a first voltage; S3, generating a compensation signal according to the first voltage through digital-to-analog conversion, and performing a second analog-to-digital conversion on the initial amplified signal and the compensation signal to obtain a second voltage by measurement; S4. Add the first voltage and the second measurement result to obtain a large dynamic range voltage of the initial bioelectric signal.

10. An anti-interference ADC biopotential sampling method, characterized in that: Also includes: S5. Filtering out the offset voltage and temperature drift of the large dynamic range voltage.

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