WO2022139257A1

WO2022139257A1 - Device for measuring low-frequency bio-signal while repeatedly injecting high-frequency current or applying voltage, and method therefor

Info

Publication number: WO2022139257A1
Application number: PCT/KR2021/018478
Authority: WO
Inventors: 조규남; 김영은
Original assignee: 주식회사 바이랩
Priority date: 2020-12-21
Filing date: 2021-12-07
Publication date: 2022-06-30
Also published as: KR20220089171A; KR102478292B1

Abstract

The present invention relates to a device for measuring a low-frequency bio-signal while repeatedly having inflow of high-frequency current or applying voltage, and a method therefor, the device being capable of removing noise caused by current or voltage, which has a relatively higher signal level and higher frequency than the low-frequency bio-signal, and measuring the low-frequency bio-signal, when the low-frequency bio-signal is measured through two from among a plurality of electrodes while a high-frequency current is flowing or voltage is applied to the plurality of electrodes attached to an examinee.

Description

Apparatus and method for measuring low-frequency biosignals while repeatedly injecting high-frequency current or applying voltage

The present invention relates to an apparatus and method for measuring a low-frequency biosignal while repeatedly injecting a high-frequency current or applying a voltage, and more particularly, to a plurality of electrodes attached to a subject by injecting a high-frequency current or applying a voltage When measuring a low-frequency bio-signal through two of the plurality of electrodes during It relates to an apparatus and a method for the same.

Due to the rapid development of medical technology, electrical impedance tomography (EMR) technology to measure the internal impedance of the patient's body, low-frequency bio-signal measurement technology to measure low-frequency bio-signals such as the patient's electrocardiogram or brain waves, etc. Accordingly, the need for a patient monitoring technology for complexly monitoring a patient's condition by combining an electrical impedance tomography technique and a low-frequency biosignal measurement technique is also increasing.

The electrical impedance tomography technique injects a high-frequency current (or applies a high-frequency voltage) through a plurality of electrodes attached to the patient's body, and measures the voltage induced by the injected high-frequency current to the inside of the patient's body ( It is a technique to measure bio-impedance to the chest, lungs, etc.).

In addition, the low-frequency bio-signal measurement technology is a technology for measuring low-frequency bio-signals such as electrocardiogram or brain waves generated in the patient's body through a plurality of electrodes attached to the patient's body.

However, when the impedance signal and the low-frequency bio-signal are simultaneously measured through the conventional patient monitoring technique, there is a problem in that the low-frequency bio-signal includes noise due to the injection of the high-frequency current.

On the other hand, when measuring the bio-impedance signal and the low-frequency bio-signal at the same time, it is functional to provide a low-pass filter in the amplifier for amplifying the low-frequency bio-signal to remove the noise caused by the high-frequency current or voltage. is possible, but it is not easy to remove noise due to high-frequency current or voltage through the low-pass filter in a situation where two signals actually coexist.

Current electrical impedance tomography technology has a structure in which bioimpedance is measured from another electrode by repeatedly injecting or applying a high-frequency current or voltage to a subject through some of a plurality of electrodes, To measure low-frequency biosignals generated from a sample, power (eg, 60Hz), DC offset, high-frequency signals, and noise signals of various frequencies and magnitudes generated by repeatedly injecting current or applying voltage are generated. There is a limit in removing noise caused by the noise signal simply through a low-pass filter.

Accordingly, in the present invention, when a high-frequency bio-impedance signal and a low-frequency bio-signal are simultaneously measured by sharing a plurality of electrodes, a high-frequency current or voltage is repeatedly injected or applied to the plurality of electrodes periodically, but the current or voltage is injected It is intended to measure low-frequency biosignals generated in the subject during half-cycle with or without application. In addition, the low-frequency bio-signal is measured in synchronization with the frequency at which current or voltage is periodically injected or applied, and the low-frequency bio-signal is modulated to obtain the synchronizing frequency, and the modulated signal is demodulated, and the modulation and demodulation are performed. We propose a method to effectively measure a desired low-frequency biosignal by removing the noise signal during the

That is, in the present invention, when a low-frequency bio-signal is measured through two of the plurality of electrodes while a high-frequency current or voltage is applied to the plurality of electrodes attached to the subject, the signal is relatively compared to the low-frequency bio-signal. An apparatus and method for removing high-level or high-frequency noise and measuring low-frequency biosignals are provided.

Next, the prior art existing in the technical field of the present invention will be briefly described, and then the technical matters that the present invention intends to achieve differently from the prior art will be described.

First, Korean Patent Application Laid-Open No. 2008-0088727 (2008.10.06.) relates to a meridian impedance measurement and analysis device. A plurality of impedance measurement sensors and an electrocardiogram sensor are attached to a patient's body to provide a constant value for the plurality of impedance measurement sensors. The present invention relates to a meridian impedance measuring and analyzing apparatus for measuring the bioimpedance of a body part by applying a current having a frequency and simultaneously measuring an electrocardiogram of a patient through the electrocardiogram sensor.

The prior art simply describes how to measure the bioimpedance and the electrocardiogram at the same time by using a plurality of impedance measuring sensors and electrocardiogram sensors, and does not provide a specific and practical method of measuring the electrocardiogram and the electrocardiogram.

That is, according to the present invention, the low-frequency biosignal is modulated at a frequency that is inversely synchronized with the injection of the high-frequency current or voltage through switching synchronized with repeatedly injecting a high-frequency current or applying a high-frequency voltage to a plurality of electrodes. By processing to be acquired, it is possible to effectively measure low-frequency biosignals, and the prior art does not describe, suggest, or suggest any technical features of the present invention.

In addition, Korea Patent No. 0682941 (2007.02.08.) relates to an apparatus and method for simultaneous measurement of biosignals, by temporally separating the application and non-application of a stimulation signal through a plurality of electrodes, After measuring the first intermediate signal for the first bio-signal generated in response to the response and the second intermediate signal for the naturally occurring second bio-signal, the first intermediate signal is used using the frequency for the applied stimulus signal. A biosignal simultaneous measurement apparatus and method for obtaining a first biosignal from a signal and for measuring the naturally occurring specific biosignal by filtering a specific frequency band in which a second biosignal exists from the second intermediate signal .

That is, the prior art simply separates the process of measuring the first bio-signal from the process of measuring the second bio-signal in time to measure the second bio-signal through a separate process. Afterwards, the effect is measured as a biosignal, and the second biosignal is not measured at the same time while the stimulus signal is continuously applied.

On the other hand, in the present invention, the bioimpedance is measured through a plurality of electrodes using switching synchronized with the repeated injection of high-frequency current or voltage application to the plurality of electrodes, and at the same time, specific two electrodes among the plurality of electrodes are used. There is a significant difference between the prior art and the present invention in measuring low-frequency biosignals such as electrocardiogram, brainwave, or electromyography.

In the prior art discussed above, only the concept of simultaneously measuring the bio-impedance and the bio-signal is described, or it describes that the bio-impedance and the bio-signal are simultaneously measured by filtering the bio-impedance and the bio-signal in the frequency band of each signal.

On the other hand, the present invention acquires a biosignal modulated to the reversely synchronized frequency through specific two electrodes by synchronizing inversely to a switching cycle of repeatedly injecting or applying a high-frequency current or voltage to a plurality of electrodes, By demodulating this into a low-frequency bio-signal, the low-frequency bio-signal can be effectively measured, and there is a clear difference between the prior art and the present invention.

The present invention was created to solve the above problems, and by repeatedly injecting a high-frequency current or applying a voltage to a plurality of electrodes attached to the object, the bio-impedance of the object and a specific one of the plurality of electrodes An object of the present invention is to provide an apparatus and method for simultaneously measuring a specific low-frequency biosignal through two electrodes.

In addition, the present invention obtains a low-frequency bio-signal by demodulating the bio-signal modulated to the switching frequency obtained by using the two specific electrodes through the repetitive injection of high-frequency current or switching in reverse synchronization with the application of the high-frequency voltage. Another object of the present invention is to provide an apparatus and a method for the same.

Another object of the present invention is to provide an apparatus and method for efficiently measuring low-frequency bio-signals by removing noise included in an input signal in the process of amplifying and demodulating the switched and modulated bio-signals.

In addition, the present invention includes filtering the differential signals for the biosignals input through the two electrodes, respectively, and removing noise (eg, motion artifacts according to the movement of the subject) included in the differential signals. Another object of the present invention is to provide an apparatus and method for obtaining a biosignal.

In addition, the present invention amplifies the modulated bio-signal, samples the amplified bio-signal at high speed and converts it into a digital signal, and digitally demodulates the converted digital signal to measure a low-frequency bio-signal, or the amplified bio-signal Another object of the present invention is to provide an apparatus and method for measuring a low-frequency biosignal by performing analog demodulation, including removing noise, for the signal.

An apparatus for measuring a low-frequency biosignal while repeatedly injecting a high-frequency current or applying a voltage according to an embodiment of the present invention obtains a biosignal by using specific two electrodes among a plurality of electrodes attached to a subject. A low-frequency bio-signal acquisition unit, a switching unit for outputting a modulated signal obtained by modulating the obtained bio-signal in synchronization with the repeated injection of high-frequency current or voltage application to the plurality of electrodes, and extracting a low-frequency bio-signal from the modulated signal and a low-frequency biosignal processing unit, wherein the modulated signal is generated through switching synchronized with the injection of the high-frequency current or the application of a voltage, and noise caused by the injection of the high-frequency current or the application of a voltage is removed.

In addition, the switching unit is switched to ground while the high-frequency current or voltage is applied, and is switched to the low-frequency bio-signal acquisition unit while the high-frequency current or voltage is not injected or applied, so that the high-frequency current or voltage is applied and reversed. , and modulating the obtained bio-signal with a switching frequency according to the switching.

In addition, the low-frequency bio-signal acquisition unit, a high-pass filter for removing noise by filtering a differential signal for the bio-signal measured using the specific two electrodes, respectively, and the differential signal from which the noise is removed It characterized in that it further comprises an amplifier which acquires the bio-signal by summing and converting it into a single-ended signal. Here, since various operations other than the summation may be used, the present invention is not limited to the summation.

In addition, the low-frequency biosignal processing unit includes an AC amplifying unit for amplifying the modulated signal by a preset multiple, and an A/D converting unit for converting the amplified modulated signal into a digital signal by sampling the amplified modulated signal at high speed and converting the digital signal. Further comprising a digital demodulator for demodulating the modulated signal, or an analog demodulator for demodulating the amplified modulated signal, wherein the AC amplifying unit includes a preset bandwidth based on the same frequency as the switching frequency in the modulated signal. It characterized in that it comprises amplifying the modulation signal within the range.

In addition, the digital demodulator, an in-phase component extracting unit for extracting an in-phase component (In-phase component) from the modulated signal converted to the digital signal, a quadrature component from the modulated signal converted to the digital signal It characterized in that it further comprises a quadrature component extractor to extract and a low-frequency biosignal extractor for extracting the low-frequency biosignal by calculating the square root of the extracted in-phase component and the extracted quadrature component.

In addition, the analog demodulator may include: an in-phase component extractor for extracting an in-phase component from the amplified modulated signal; a quadrature component extracting unit for extracting a quadrature component from the amplified modulated signal; and a low-frequency bio-signal extractor configured to extract the low-frequency bio-signal by calculating the square root of the sum of the square of the extracted in-phase component and the square of the extracted quadrature component.

In addition, in the method of measuring a low-frequency biosignal while repeatedly injecting a high-frequency current or applying a voltage according to an embodiment of the present invention, a biosignal is obtained by using specific two electrodes among a plurality of electrodes attached to the subject. a switching step of outputting a modulated signal obtained by modulating the obtained bio-signal in synchronization with the repeated injection of high-frequency current or voltage application to the plurality of electrodes, and extracting a low-frequency bio-signal from the modulated signal It is characterized in that it comprises a low-frequency bio-signal processing step.

In addition, in the switching step, the high frequency current injection or voltage is switched to ground while the high frequency current is injected or voltage is applied, and switched to the output of the low frequency biosignal acquisition step while the high frequency current is not injected or the voltage is not applied. Synchronized with the application, it characterized in that the obtained bio-signal is modulated with a switching frequency according to the switching.

In addition, the low-frequency bio-signal acquisition step includes filtering each of the bio-signals measured using the two specific electrodes to remove noise, and adding the filtered signals from which the noise is removed in an amplifier to obtain a single-ended signal (Single signal). -ended Signal), characterized in that it further comprises the step of obtaining the bio-signal. Here, since various operations other than the summation may be used, the present invention is not limited to the summation.

In addition, the low-frequency biosignal processing step includes an AC amplification step of amplifying the modulated signal by a preset multiple, and an A/D conversion unit that samples the amplified modulated signal at high speed and converts it into a digital signal and the digital signal A digital demodulation step of demodulating one modulated signal, or an analog demodulation step of demodulating the amplified modulated signal; further comprising, wherein the AC amplifying step is preset based on a frequency equal to the switching frequency in the modulated signal and amplifying the modulated signal within one bandwidth range.

In addition, the digital demodulation step includes an in-phase component extraction step of extracting an in-phase component from the modulated signal converted into the digital signal, a quadrature component extraction step of extracting a quadrature component from the modulated signal converted into the digital signal, and the It characterized in that it further comprises a low-frequency bio-signal extraction step of extracting the low-frequency bio-signal by calculating the square root of the extracted in-phase component and the extracted quadrature component.

In addition, the analog demodulation step may include an in-phase component extraction step of extracting an in-phase component from the amplified modulated signal; a quadrature component extraction step of extracting a quadrature component from the amplified modulated signal; and a low-frequency bio-signal extraction step of extracting the low-frequency bio-signal by calculating the square root of the sum of the square of the extracted in-phase component and the square of the extracted quadrature component.

As described above, the apparatus and method for measuring a low-frequency biosignal while repeatedly injecting or applying a high-frequency current or voltage according to the present invention include repeatedly injecting or applying a high-frequency current or voltage to a plurality of electrodes at the same time as two By synchronizing and switching reception of a low-frequency bio-signal through an electrode at a predetermined frequency, the low-frequency bio-signal is modulated with the predetermined switching frequency, and demodulating the modulated bio-signal to extract a low-frequency bio-signal, wherein By removing noise in the process of modulation and demodulation, it is possible to accurately measure low-frequency bio-signals while repeatedly injecting high-frequency current or applying voltage.

1 is a conceptual diagram illustrating an apparatus and method for measuring a low-frequency biosignal while repeatedly injecting a current or applying a voltage according to an embodiment of the present invention.

2 is a block diagram showing the configuration of an apparatus for simultaneously measuring high-frequency impedance and low-frequency bio-signals while repeatedly injecting current according to an embodiment of the present invention.

3 is a block diagram showing the configuration of a low-frequency bio-signal acquisition unit according to an embodiment of the present invention.

4 is a diagram illustrating a process of extracting a low-frequency biosignal according to an embodiment of the present invention.

5 is a block diagram showing the configuration of a low-frequency biosignal processing unit according to an embodiment of the present invention.

6 is a block diagram illustrating the configuration of a demodulator according to an embodiment of the present invention.

7 is a flowchart illustrating a procedure for measuring a low-frequency biosignal while repeatedly injecting a high-frequency current or applying a voltage according to an embodiment of the present invention.

Hereinafter, a preferred embodiment of an apparatus and method for measuring a low-frequency biosignal while repeatedly injecting a current or applying a voltage of the present invention will be described in detail with reference to the accompanying drawings.

Like reference numerals in each figure indicate like elements. In addition, specific structural or functional descriptions of the embodiments of the present invention are only exemplified for the purpose of describing the embodiments according to the present invention, and unless otherwise defined, all used herein, including technical or scientific terms, are Terms have the same meanings as commonly understood by those of ordinary skill in the art to which the present invention pertains. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present specification. It is preferable not to

As shown in FIG. 1 , an apparatus 100 for measuring a low-frequency bio-signal (hereinafter referred to as a low-frequency bio-signal measuring device) according to an embodiment of the present invention operates in conjunction with the high-frequency bio-signal measuring device 200 . do. That is, while the high-frequency current or high-frequency voltage is repeatedly applied to the plurality of electrodes attached to the subject (human or animal) in the high-frequency bio-signal measuring device 200, the high-frequency bio-signal measuring device 200 The internal impedance of the body to be measured is measured through the plurality of electrodes, and at the same time, the low-frequency biosignal measuring apparatus 100 uses specific two electrodes among the plurality of electrodes to measure a specific low-frequency biometric body to the subject. to measure the signal. Accordingly, by repeatedly injecting current or applying a voltage to the subject through a plurality of electrodes at the same time, by measuring a low frequency biosignal generated from the subject through some of the electrodes at the same time, not only the measured high frequency biosignal but also the low frequency The condition of the subject can be more efficiently monitored using the biosignal.

More specifically, the high-frequency biosignal measuring apparatus 200 selects a pair of electrodes from among a plurality of electrodes according to a preset period, injects the high-frequency current or applies a high-frequency voltage, and passes through the remaining electrodes. A process of measuring a voltage induced by the injected high-frequency current or the applied low-frequency voltage is repeatedly performed to obtain a high-frequency biosignal for the inside of the body of the subject.

In addition, the high-frequency bio-signal measuring device 200 measures the bio-impedance to the inside of the body of the subject according to the obtained high-frequency bio-signal, and processes the measured bio-impedance to determine the impedance distribution within the body or the It performs a function of outputting bio-impedance data including an image inside the body representing the impedance change.

In this case, the high frequency biosignal measuring device 200 is an EIT (Electrical Impedance Tomography) device or bioimpedance for outputting the bioimpedance processing data through repeated injection of a high frequency current or repeated application of a high frequency voltage to the plurality of electrodes. (Bio Impedance) may be a device.

For example, when the high-frequency biosignal measuring device 200 is configured as the EIT device, the measured impedance is processed to generate bioimpedance data including an image inside the body representing an impedance distribution or impedance change in the body, By outputting the generated bio-impedance data to the high-frequency bio-signal display 400, it is possible to visually check the impedance change in the body.

On the other hand, the distribution of the impedance may indicate a distribution of the amount of air in the chest due to respiration of the subject, and the change signal may be a respiration signal indicating a change in the distribution of the air amount, through the outputted bioimpedance processing data. The breathing state of the subject may be monitored.

Hereinafter, the repetitive current injection will be mainly described, but this may be interpreted as a meaning of repeatedly applying a high-frequency voltage in addition to repeatedly injecting a high-frequency current into the plurality of electrodes attached to the subject. .

In addition, the low-frequency bio-signal measuring device 100, while the high-frequency current is repeatedly injected into the plurality of electrodes in the high-frequency bio-signal measuring device 200, selects two specific electrodes selected in advance among the plurality of electrodes. A biosignal for the subject is obtained by measuring the voltage using the

The two specific electrodes measure the high-frequency bio-signal and simultaneously acquire a bio-signal including the specific low-frequency bio-signal. The low-frequency bio-signal measuring device 100 measures the specific low-frequency bio signal. It is attached to different specific positions for this purpose, and any one of the two electrodes may be a reference electrode.

Here, the low-frequency biosignal is a signal generated in the subject, such as an electrocardiogram, an EEG, or an electromyogram.

In this case, the obtained bio-signal includes noise caused by switching for injection of the high-frequency current and repeated injection thereof, noise caused by DC offset, noise caused by a power supply (eg 60Hz), or a combination thereof. may include more. Of course, there can be numerous large and small noises other than those listed here.

For example, an operation of selecting a pair of electrodes from among the plurality of electrodes and injecting a current (alternating current) of 10 V and 100 kHz for 0.5 ms, and not injecting the current during the 0.5 ms (that is, the current injection is 1 ms cycle) to simultaneously measure the bioimpedance and low frequency biosignal (eg, 5mV electrocardiogram), the obtained biosignal includes not only high frequency noise of 100kHz and noise of 1kHz due to the cycle The DC offset and noise due to power are included. In the case of using a low-pass filter having a cut-off frequency of 100 kHz as in the prior art to remove such noise, the noise by 100 kHz at the output of the low-pass filter is reduced to 10 mV, but the noise of 1 kHz of 10 V is reduced to 1 V, which is sufficient The noise level is not removed, and noise due to low frequency power or DC offset is not removed either.

Accordingly, the low-frequency bio-signal measuring apparatus 100 acquires the low-frequency bio-signal by synchronizing in reverse with the switching period for repeated injection of the high-frequency current, that is, the repetition of injection and non-injection of the high-frequency current, so that the bio-signal is As a result of being modulated, the low-frequency bio-signal is restored by decoding the modulated bio-signal. Noise is removed in the process of modulation and demodulation.

The low-frequency bio-signal measuring apparatus 100 supports a function of outputting the measured low-frequency bio-signal to the low-frequency bio-signal display 300 to monitor the condition of the patient.

In addition, the high frequency biosignal measuring apparatus 200 supports a function of outputting the measured high frequency impedance to the high frequency biosignal display 400 to monitor the condition of the patient.

Although FIG. 1 shows the low-frequency bio-signal measuring device 100 and the high-frequency bio-signal measuring device 200 as separate devices, the components and functions of the high frequency bio-signal measuring device 200 are different from the low-frequency bio-signal measuring device 200. It will be natural that it can be implemented by being integrated with the measuring device 100 .

Hereinafter, a description will be given of the interlocking of a device that simultaneously measures a high-frequency bioimpedance and a low-frequency biosignal while repeatedly injecting a high-frequency current.

As shown in FIG. 2 , the low-frequency biosignal measuring apparatus 100 according to an embodiment of the present invention uses two specific electrodes while repeatedly injecting high-frequency current into a plurality of electrodes attached to the body of a subject. a low-frequency bio-signal acquisition unit 110 to obtain a bio-signal for the subject; a switching unit 120 for generating a modulated signal by synchronizing the obtained bio-signal with a cycle of repeating injection of the high-frequency current; and a low-frequency bio-signal processing unit 130 for extracting a low-frequency bio-signal by demodulating a signal included in the high-frequency switching signal from the signal.

The low-frequency bio-signal acquisition unit 110 performs a function of acquiring a bio-signal including the low-frequency bio-signal using two specific electrodes while repeatedly injecting the high-frequency current.

In addition, the switching unit 120 performs a function of periodically selecting and modulating the obtained bio-signal through repeated injection of the high-frequency current and synchronized switching. Here, the switching frequency may be several tens of times higher than that of the obtained biosignal.

Meanwhile, the high frequency biosignal measuring device 200 includes a current injecting unit/voltage applying unit 220 , a high frequency biosignal obtaining unit 210 , and a bioimpedance processing unit 230 .

The current injecting unit/voltage applying unit 220 serves to repeatedly inject a high frequency current into the plurality of electrodes according to a predetermined cycle. A high-frequency voltage may be applied instead of the injection of the high-frequency current.

In addition, the high-frequency bio-signal acquisition unit 210 serves to acquire a high-frequency bio-signal through the remaining electrodes among the plurality of electrodes while the high-frequency current is repeatedly injected into some of the plurality of electrodes.

In addition, the bio-impedance processing unit 230 measures bio-impedance from the obtained high-frequency bio-signal, and processes the measured bio-impedance to include a bio-internal image of the subject, a change in the bio-impedance, or a combination thereof. It serves to generate bioimpedance data through bioimpedance processing.

Hereinafter, the low-frequency bio-signal acquisition unit 110 in the low-frequency bio-signal measuring apparatus 100 will be described in detail.

As shown in FIG. 3 , the low-frequency bio-signal acquisition unit 110 according to an embodiment of the present invention includes a high-pass filter 111 and an amplifier 112 for receiving and amplifying a bio-signal from an input terminal. do.

The high-pass filter 111 serves to remove low-frequency noise (eg, motion artifacts, etc.) included in each differential signal with respect to the bio-signal received from the subject. That is, the high-pass filter 111 receives a differential signal for the bio-signal including the low-frequency bio-signal generated in the subject measured through two specific electrodes at the input end of the low-frequency bio-signal acquisition unit 110 . It receives the input and removes noise (eg, motion artifact) included in the received differential signal.

Here, the low-frequency biosignal is measured by detecting a voltage (or current) value input through the two specific electrodes. Also, in the case of the high-frequency biosignal acquisition unit 210 , it is measured by detecting a voltage value that is connected to the plurality of electrodes and induced by the repeatedly injected current.

For example, when the low-frequency biosignal measuring apparatus 100 intends to measure the electrocardiogram of the subject, the specific frequency may be set to 0.5 Hz to 0.05 Hz. The specific frequency is variably set according to the low-frequency bio-signal to be measured by the low-frequency bio-signal measuring apparatus 100, such as the electrocardiogram, brain wave, or electromyogram.

In addition, the amplifier 112 serves to obtain a low-frequency bio-signal by summing each differential signal from which the low-frequency noise has been removed. That is, the amplifier 112 may be configured as a single (One) Chip Differential Amplifier, and converts the noise-removed differential signals into a single-ended signal by summing them. Accordingly, although the low-frequency biosignal is acquired, the noise induced by the switching frequency in which current is injected and not injected is not removed. Here, since various operations other than the summation may be used, the present invention is not limited to the summation.

If the high-frequency current periodically repeats injection and non-injection, if the low-frequency bio-signal is measured in a section where the high-frequency current is not injected, it will be possible to measure the low-frequency bio-signal without any problem by the ideal logic. However, in reality, when a high-frequency current is applied and then not applied repeatedly, noise is induced by the frequency of repeated application and non-application.

Hereinafter, when a high-frequency current is repeatedly injected, noise induced by a switching frequency that repeats injection and non-injection of the high-frequency current generated when measuring a low-frequency biosignal in a section in which the high-frequency current is not injected is removed. We would like to explain the method in detail.

Referring to the switching unit 120 shown in FIG. 3 , the switching unit 120 is switched to ground while the high-frequency current is injected (ie, switched off), and while the high-frequency current is not injected, the low-frequency biological body It is switched to the output of the signal acquisition unit 110 (ie, switched on), and is switched to the low-frequency bio-signal obtained by the low-frequency bio-signal acquisition unit 110 . That is, when passing through the switching unit 120, the low-frequency bio-signal obtained by the low-frequency bio-signal obtaining unit 110 is modulated by a high switching frequency. Accordingly, the output of the switching unit 120 becomes a biosignal modulated by the switching frequency.

As shown in Fig. 4, it is synchronized to measure the specific low-frequency bio-signal while the high-frequency current is not injected, and the obtained bio-signal is selected according to the switching, and a signal modulated by the switching frequency is output As a result, the modulated signal must be restored back to a low-frequency bio-signal through demodulation. Noise due to high-frequency switching is removed through the demodulation process.

Also, the low-frequency bio-signal processing unit 130 amplifies the modulated signal by a preset multiple and outputs the amplified modulated signal.

At this time, the low-frequency bio-signal processing unit 130 amplifies the modulated signal, but selectively amplifies only the modulated signal corresponding to the same frequency as the switching frequency (ie, the modulation frequency) to remove the additionally introduced noise. . In this case, the selectively amplifying is performed by amplifying a modulated signal having the same frequency as the switching frequency and corresponding to a preset bandwidth range based on the frequency.

For example, when the switching frequency of the low-frequency biosignal processing unit 130 is 3 kHz and the ECG of the subject is to be measured, the bandwidth range may be set to 30 Hz left and right around 3 kHz, that is, a total of 60 Hz. . Meanwhile, the bandwidth range may be variably set according to the type of the low-frequency bio-signal to be measured by the low-frequency bio-signal measuring apparatus 100 .

In addition, the low-frequency biosignal processing unit 130 samples the amplified modulated signal at high speed, converts it into a digital signal, and then digitally demodulates the modulated signal converted to the digital signal again, thereby generating the high-frequency current from the modulated signal. It performs a function of extracting and outputting the specific low-frequency bio-signal from which noise due to the repetitive application of , and noise due to the switching are removed.

In addition, the low-frequency bio-signal processing unit 130 may demodulate the amplified modulated signal to analog. The analog demodulation extracts an in-phase component from the amplified modulated signal, extracts a quadrature component from the amplified modulated signal, and the square of the extracted in-phase component and The low-frequency biosignal may be extracted by calculating a square root of the sum of the squares of the extracted quadrature components.

Meanwhile, the configuration of the low-frequency biosignal processing unit 130 will be described in detail with reference to FIGS. 5 and 6 .

5 is a block diagram illustrating a configuration of a signal processing unit according to an embodiment of the present invention, and FIG. 6 is a block diagram illustrating a configuration of a digital demodulator according to an embodiment of the present invention.

5, the low-frequency biosignal processing unit 130 according to an embodiment of the present invention includes an AC amplifier 131 amplifying the modulated signal output from the switching unit 120, and the amplified modulation signal. A/D converter 132 that converts a signal into a digital signal, and digital demodulation of the modulated signal converted into the digital signal or demodulation of an analog signal, extracting the specific low-frequency biosignal from the modulated signal and outputting it It is configured to include a grandfather (133). For the analog demodulation, the A/D converter 132 is unnecessary.

The AC amplifier 131 amplifies the modulated signal by a preset multiple (eg, 300 times), but selectively amplifies the modulated signal equal to the switching frequency to remove additional high-frequency noise from the modulated signal.

For example, if the low-frequency biosignal to be measured is an electrocardiogram (ECG) and the switching frequency (ie, modulation frequency) is 3 kHz, it has a frequency of 3 kHz and is within a preset bandwidth range centered on the 3 kHz. Selectively amplifies the modulated signal of (eg 60Hz).

In addition, the A/D converter 132 performs a function of converting the amplified modulated signal into a digital signal by high-speed sampling at 300 kHz to 600 kHz. That is, in order to digitally demodulate information on the amplified modulated signal, the A/D converter 132 samples the amplified modulated signal at high speed and converts it into digital data.

In addition, the demodulator 133 digitally demodulates the modulated signal converted into the digital signal, extracts only the component included in the corresponding modulation frequency component, and restores and outputs a specific low frequency biosignal. The demodulator 133 may be configured to perform analog demodulation.

As shown in FIG. 6 , the demodulator 133 according to an embodiment of the present invention receives the modulated bio-signal converted into the digital signal, and extracts an in-phase component. The extraction unit 133a, the quadrature component extraction unit 133b that receives the modulated signal converted into the digital signal and extracts the quadrature component, and the extracted in-phase component and the quadrature component by calculating the square root and a low-frequency bio-signal extracting unit 133c that extracts and outputs the specific low-frequency bio-signal by final demodulating the modulated signal. However, in digital demodulation, time t can be interpreted as a discrete signal.

In addition, the in-phase component extraction unit 133a, from the result of multiplying the modulated biosignal converted into the digital signal by a sinusoidal component of a preset frequency, selects a portion corresponding to a plurality of periods in advance The in-phase component is extracted by performing signal averaging for summing and averaging. Here, when the sine wave is multiplied by the input signal and signal averaging is performed, the frequency component of the sine wave is removed from the input signal and only an average value is output.

In addition, the quadrature extractor 133b adds up and averages portions corresponding to a plurality of preset periods in a result of multiplying the digital signal by a cosine component of a preset frequency. By performing ridging, the quadrature component is extracted. Here, when the cosine wave is multiplied by the input signal and signal averaging is performed, the frequency component of the cosine wave is removed from the input signal and only an average value is output.

In this case, the preset frequency is preferably set to the same frequency as the switching frequency. In addition, the extraction of the in-phase component and the quadrature component of the low-frequency bio-signal is performed in parallel and at the same time.

In addition, the low-frequency biosignal extractor 133c squares and sums the extracted in-phase component and the quadrature component, respectively, calculates a square root of the summed result, and converts the modulated signal into the digital signal to final demodulation. By doing so, the specific low-frequency biosignal (eg, electrocardiogram) is extracted from the modulated signal.

In addition, the low-frequency bio-signal extractor 133c outputs the extracted specific low-frequency bio-signal to the low-frequency bio-signal display 300 .

In addition, the low-frequency biosignal processing unit 130 may be configured to include an analog demodulator 133 for demodulating the amplified modulated signal. Here, the analog demodulator includes an in-phase component extractor for extracting an in-phase component from the amplified modulated signal, and a quadrature component for extracting a quadrature component from the amplified modulated signal. and a low-frequency bio-signal extractor configured to extract the low-frequency bio-signal by calculating the square root of the sum of negative and the square of the extracted in-phase component and the square of the extracted quadrature component. The configuration of the analog demodulator may correspond to each configuration of the digital demodulator and may be separately configured or provided.

In the present invention, the demodulator 133 performs analog demodulation by AC-amplifying the modulated bio-signal and then directly demodulating it without A/D conversion. On the other hand, after AC-amplifying the modulated bio-signal, A/D conversion and demodulation are digital demodulation of discrete signals.

As shown in FIG. 7 , the procedure for measuring a specific low-frequency bio-signal to the subject while repeatedly injecting current or applying a voltage according to an embodiment of the present invention is first performed by the low-frequency bio-signal measuring apparatus 100 ) performs a low-frequency bio-signal acquisition step of acquiring a bio-signal for the subject by using two specific pre-selected electrodes among a plurality of electrodes (S110).

The low-frequency biosignal acquisition step includes removing low-frequency noise from differential signals having different phases from each other measured through the two specific electrodes, and adding the differential signals from which the low-frequency noise has been removed into a single-ended signal by converting it into a single-ended signal, and acquiring a biosignal. Here, since various operations other than the summation may be used, the present invention is not limited to the summation.

Meanwhile, since the detailed procedure for acquiring the biosignal has been described with reference to FIG. 3 , further detailed description will be omitted.

Next, the low-frequency bio-signal measuring apparatus 100 performs a switching step of modulating the obtained bio-signal with a switching frequency synchronized with the high-frequency current injection period (S120).

That is, in the switching step, the obtained bio-signal is modulated with the switching frequency (ie, modulation frequency) through switching synchronized with the repeated injection of the high-frequency current, and outputting the resulting modulated signal, so that the high-frequency current and It removes the noise caused by its repetitive injection.

Next, the low-frequency bio-signal measuring apparatus 100 performs a low-frequency bio-signal processing step of extracting and outputting the specific low-frequency bio-signal from the modulated bio-signal (ie, a modulated signal).

The low-frequency biosignal processing step includes an AC amplification step of amplifying the modulated signal (S130), and an A/D conversion step of converting the amplified modulated signal (the modulated biosignal) into a digital signal (S140) (step S140). is unnecessary when performing analog demodulation), extracting an in-phase component from the modulated signal converted to the digital signal (S150), extracting a quadrature component from the modulated signal converted to the digital signal A quadrature component extraction step (S151) and a low-frequency biosignal extraction step of finally extracting and outputting the specific low-frequency biosignal from the modulated signal converted into the digital signal using the extracted in-phase component and quadrature component (S160) includes

Amplifying the modulated signal and converting the amplified modulated signal into a digital signal has been described with reference to FIG. 5, and thus a further detailed description will be omitted.

In addition, the in-phase component is extracted by multiplying the modulated signal converted into the digital signal by a sinusoidal signal (sinωt) of a preset frequency, and summing the parts corresponding to a plurality of preset periods from the multiplication result and averaging is as described above.

In addition, the quadrature component is obtained by multiplying the modulated signal converted into the digital signal by a cosine wave signal (cosωt) of a preset frequency, and summing the parts corresponding to the plurality of preset periods from the multiplication result and average The extraction is as described above.

In the low-frequency biosignal extraction step, the extracted in-phase component and the quadrature component are squared and summed, respectively, and the square root of the summed result is calculated, thereby finally demodulating the modulated signal converted into the digital signal, Extracts specific low-frequency biosignals.

In addition, the low-frequency biosignal processing step may include an analog demodulation step of demodulating the amplified modulated signal. Here, the analog demodulation step includes an in-phase component extraction step for extracting an in-phase component from the amplified modulated signal, and a quadrature component for extracting a quadrature component from the amplified modulated signal. It may comprise an extraction step and a low-frequency bio-signal extraction step of extracting the low-frequency bio-signal by calculating the square root of the sum of the square of the extracted in-phase component and the square of the extracted quadrature component. It is preferable that the detailed steps of the analog demodulation step correspond to each configuration of the digital demodulator and are separately configured or provided.

In the above, the preferred embodiment according to the present invention has been mainly described above, but the technical spirit of the present invention is not limited thereto, and each component of the present invention is changed or modified within the technical scope of the present invention to achieve the same purpose and effect. it could be

In addition, although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention belongs without departing from the gist of the present invention as claimed in the claims In addition, various modifications may be made by those of ordinary skill in the art, and these modifications should not be individually understood from the technical spirit or perspective of the present invention.

The present invention provides an apparatus and method for measuring a low-frequency biosignal while repeatedly injecting a high-frequency current or applying a voltage, using two specific electrodes through switching synchronized with the repetitively injecting a high-frequency current or applying a high-frequency voltage to modulate the obtained bio-signal, and selectively amplify only the modulated signal within a preset bandwidth range centered on the switching frequency in the modulated bio-signal to repeatedly inject the high-frequency current or repeatedly apply the high-frequency voltage and noise due to the switching can be removed to accurately measure low-frequency biosignals for the subject.

Claims

a low-frequency bio-signal obtaining unit for obtaining bio-signals by using specific two electrodes among a plurality of electrodes attached to the subject;

a switching unit for outputting a modulated signal obtained by modulating the obtained biosignal in synchronization with the repeated injection of high-frequency current or application of voltage to the plurality of electrodes; and

and a low-frequency bio-signal processing unit that extracts a low-frequency bio-signal from the modulated signal.

The modulation signal is generated through switching synchronized with the injection of the high-frequency current or the application of a voltage, and repeatedly injecting a high-frequency current or applying a voltage, characterized in that the noise caused by the injection of the high-frequency current or the application of a voltage is removed A device that measures low-frequency biosignals during application.
The method according to claim 1,

The switching unit,

It is switched to ground while the high-frequency current is injected or voltage is applied, and is switched to the low-frequency biosignal acquisition unit while the high-frequency current is not injected or voltage is not applied, so that it is synchronized with the high-frequency current injection or voltage application,

An apparatus for repeatedly injecting a high-frequency current or measuring a low-frequency bio-signal while applying a voltage, characterized in that the obtained bio-signal is modulated with a switching frequency according to the switching.
The method according to claim 1,

The low-frequency bio-signal acquisition unit,

a high-pass filter for removing noise by filtering a differential signal with respect to the bio-signal measured using the two specific electrodes; and

An amplifier for obtaining the bio-signal by converting the noise-removed differential signal into a single-ended signal; device to measure.
The method according to claim 1,

The low-frequency biosignal processing unit,

an AC amplifier for amplifying the modulated signal by a preset multiple; and

An A/D converter that samples the amplified modulated signal at high speed and converts it into a digital signal, and a digital demodulator that demodulates the modulated signal converted into the digital signal, or converts the amplified modulated signal into an analog multiplier or switch using an analog multiplier or switch. It further includes; an analog demodulator that demodulates;

The AC amplifier is, in the modulation signal, measuring a low-frequency bio-signal while repeatedly injecting a high-frequency current or applying a voltage, characterized in that it amplifies a modulation signal within a preset bandwidth range centered on a frequency equal to a switching frequency device to do.
5. The method according to claim 4,

The digital demodulator,

an in-phase component extracting unit for extracting an in-phase component from the modulated signal converted into the digital signal;

a quadrature component extracting unit for extracting a quadrature component from the modulated signal converted into the digital signal; and

A low-frequency bio-signal extractor that extracts the low-frequency bio-signal by calculating the square root of the sum of the square of the extracted in-phase component and the square of the extracted quadrature component; A device that measures low-frequency biosignals while applying
5. The method according to claim 4,

The analog demodulator,

an in-phase component extracting unit for extracting an in-phase component from the amplified modulated signal;

a quadrature component extracting unit for extracting a quadrature component from the amplified modulated signal; and

A low-frequency bio-signal extractor that extracts the low-frequency bio-signal by calculating the square root of the sum of the square of the extracted in-phase component and the square of the extracted quadrature component; A device that measures low-frequency biosignals while applying
A low-frequency bio-signal acquisition step of acquiring a bio-signal by using specific two electrodes among a plurality of electrodes attached to the subject;

a switching step of outputting a modulated signal obtained by modulating the obtained bio-signal in synchronization with the repetitive injection of high-frequency current or application of voltage to the plurality of electrodes; and

a low-frequency bio-signal processing step of extracting a low-frequency bio-signal from the modulated signal;

The modulation signal is generated through switching synchronized with the injection of the high-frequency current or the application of a voltage, and repeatedly injecting a high-frequency current or applying a voltage, characterized in that noise caused by the injection of the high-frequency current or the application of a voltage is removed A method for measuring low-frequency biosignals during application.
8. The method of claim 7,

The switching step is

It is switched to ground while the high-frequency current is injected or voltage is applied, and is switched to the output of the low-frequency bio-signal acquisition step while the high-frequency current is not injected or voltage is not applied, so that it is synchronized with the high-frequency current injection or voltage application,

A method of repeatedly injecting a high-frequency current or measuring a low-frequency bio-signal while applying a voltage, characterized in that the obtained bio-signal is modulated with a switching frequency according to the switching.
8. The method of claim 7,

The low-frequency biosignal acquisition step includes:

removing noise by filtering a differential signal with respect to the biosignal measured using the specific two electrodes; and

In the amplifier, by converting the noise-removed differential signal into a single-ended signal, obtaining the bio-signal; repeatedly injecting a high-frequency current or applying a voltage, characterized in that it further comprises A method of measuring low-frequency biosignals during
8. The method of claim 7,

The low-frequency biosignal processing step,

an AC amplification step of amplifying the modulated signal by a preset multiple; and

A/D conversion of high-speed sampling of the amplified modulated signal to convert it into a digital signal, and a digital demodulation step of demodulating the modulated signal converted into the digital signal, or demodulating the amplified modulated signal using an analog multiplier or switch It further comprises; an analog demodulation step to

In the AC amplification step, the low-frequency biosignal while repeatedly injecting a high-frequency current or applying a voltage, characterized in that in the modulated signal, amplifying a modulated signal within a preset bandwidth range centered on the same frequency as the switching frequency How to measure.
11. The method of claim 10,

The digital demodulation step is

an in-phase component extraction step of extracting an in-phase component from the modulated signal converted into the digital signal;

a quadrature component extraction step of extracting a quadrature component from the modulated signal converted into the digital signal; and

A low-frequency bio-signal extraction step of extracting the low-frequency bio-signal by calculating the square root of the sum of the square of the extracted in-phase component and the square of the extracted quadrature component; A method of measuring low-frequency biosignals while voltage is applied.
11. The method of claim 10,

The analog demodulation step is

an in-phase component extraction step of extracting an in-phase component from the amplified modulated signal;

a quadrature component extraction step of extracting a quadrature component from the amplified modulated signal; and

A low-frequency bio-signal extractor that extracts the low-frequency bio-signal by calculating the square root of the sum of the square of the extracted in-phase component and the square of the extracted quadrature component; A method of measuring low-frequency biosignals while applying