Biological information measurement device and biological information measurement method

Abstract

Provided is a biological information measurement apparatus comprising: an AC signal supply unit that supplies an AC signal indicating a reference frequency between a pair of electrodes in contact with a living body; a first high-pass filter that blocks, from a first signal corresponding to the AC signal, a frequency band, which is lower than a first frequency band including the reference frequency; and a first amplification unit that amplifies a third signal obtained by blocking, from a second signal outputted from the first high-pass filter, a second frequency band narrower than the first frequency band and including the reference frequency, and that outputs the amplified third signal as a biological information signal indicating a fluctuation component of the impedance of the living body.

Description

Biological information measuring device and biological information measuring method

[0001] The present invention relates to a biological information measuring device and a biological information measuring method.

[0002] Patent Document 1 describes a bioimpedance measuring device that can be mounted on an implantable medical device. Patent Document 2 describes a biosignal measuring device having a bioimpedance measuring unit. Patent Document 3 describes an electronic medical device for simultaneously measuring impedance and biopotential signals. [Prior art documents] [Patent documents] [Patent document 1] JP 2012-157463 A [Patent document 2] EP 3692908 A [Patent document 3] EP 2294979 A General disclosure

[0003] (Problem to be Solved) It is desired that the bioimpedance measuring device as described in Patent Documents 1 to 3 be able to accurately identify noise components contained in a signal indicating bioimpedance. (Means for Solving the Problem) A first aspect of the present invention provides a bioinformation measuring device including: an AC signal supply unit that supplies an AC signal indicating a reference frequency between a pair of electrodes that are in contact with a living body; a first high-pass filter that blocks a frequency band lower than a first frequency band including the reference frequency from a first signal corresponding to the AC signal; and a first amplifier that amplifies a third signal obtained by blocking a second frequency band that is narrower than the first frequency band and includes the reference frequency from a second signal output from the first high-pass filter, and outputs the third signal as a bioinformation signal indicating a fluctuation component of the impedance of the living body.

[0004] In the biological information measuring device, the first amplifier may include an amplifier circuit that amplifies the third signal and outputs the result as the biological information signal. The third signal may be a signal corresponding to a component of the second signal that is outside the second frequency band of the first frequency band.

[0005] In any of the bioinformation measuring devices, the first amplifier unit may include a first mixer that converts the second signal into a signal of a third frequency band lower than the first frequency band by mixing the second signal with an AC signal indicating the reference frequency, a first low-pass filter that blocks a fourth frequency band that is higher than the third frequency band and includes the reference frequency from the signal output from the first mixer, and a second high-pass filter that blocks a frequency band lower than the first frequency within the third frequency band from the signal output from the first low-pass filter and outputs the signal as the third signal.

[0006] In any of the bioinformation measuring devices, the first amplifier unit may include a first mixer that converts the second signal into a signal of a third frequency band lower than the first frequency band by mixing the second signal with a signal indicating the reference frequency, a first low-pass filter that blocks a fourth frequency band that is higher than the third frequency band and includes the reference frequency from the signal output from the first mixer, and a separator that separates the signal output from the first low-pass filter into a signal of components of a frequency band lower than the first frequency within the third frequency band and a signal of components of a frequency band higher than the first frequency, and outputs the signal of components of the frequency band higher than the first frequency as the third signal.

[0007] In any one of the biological information measuring devices, the first amplifier section may include a notch filter that blocks the second frequency band from the second signal and outputs the second frequency band as the third signal.

[0008] In any of the biological information measuring devices, the first signal may include a biological potential component that is a combination of action potentials from each of a plurality of biological tissues that make up the living body, a fluctuation component of the impedance of the living body, and an average value component of the impedance of the living body.

[0009] In any one of the biological information measuring devices, the first amplifier may remove an average value component of the impedance of the living body by blocking the second frequency band from the second signal.

[0010] In any of the biological information measuring devices, the AC signal supply unit may include a voltage output circuit that outputs an AC voltage signal indicating the reference frequency, and a limiting unit that limits an amount of current flowing from the voltage output circuit to the living body via the pair of electrodes. The first signal may indicate a potential difference between the pair of electrodes caused by the current flowing through the living body.

[0011] The AC signal supply unit may include a current output circuit that outputs an AC signal indicative of the reference frequency. The first signal may indicate a potential difference between the pair of electrodes caused by a current flowing through the living body.

[0012] The AC signal supply unit may include a voltage output circuit that outputs an AC voltage signal indicating the reference frequency. Any of the biological information measurement devices may include a current-voltage conversion amplifier that converts a current flowing through the living body via the pair of electrodes into a voltage signal, and a single-ended differential conversion circuit that converts the voltage signal into a single-ended differential signal and outputs the signal as the first signal.

[0013] Any of the bioinformation measuring devices may further include a generating unit that generates a noise signal indicating a noise component contained in a component that is a combination of action potentials from each of a plurality of biological tissues that constitute the living body based on the bioinformation signal, and a biopotential signal output unit that removes the noise signal component from the first signal and outputs it as a biopotential signal indicating a component that is a combination of action potentials from each of a plurality of biological tissues that constitute the living body.

[0014] In any of the biological information measuring devices, the biopotential signal output unit may include a second amplifier unit that amplifies the signal output from the second low-pass filter by blocking a frequency band lower than a third frequency band including a component obtained by combining action potentials from each of a plurality of biological tissues that constitute the living organism from the first signal, and a frequency band higher than the third frequency band and including the first frequency band. The biopotential signal output unit may output the biopotential signal by removing a component of the noise signal from the signal output from the second amplifier unit.

[0015] In a second aspect of the present invention, there is provided a method for measuring biological information, comprising the steps of: supplying an AC signal indicating a reference frequency between a pair of electrodes in contact with a living body; blocking a frequency band lower than a first frequency band including the reference frequency from a first signal corresponding to the AC signal, and outputting a second signal; blocking a second frequency band narrower than the first frequency band and including the reference frequency from the second signal, and outputting a third signal; and amplifying the third signal and outputting it as a biological information signal indicating a fluctuation component of the impedance of the living body.

[0016] The above summary of the invention does not list all of the features of the present invention, and subcombinations of these features may also be inventions.

[0017] 1 is an example of a schematic diagram illustrating a bioimpedance BioZ generated in a living organism 300. FIG. 2 is a block diagram illustrating an example of the configuration of a biological information measurement device 10a. FIG. 3 is an example of a conceptual diagram illustrating processing performed by a high-pass filter 12. FIG. 4 is an example of a conceptual diagram illustrating processing performed by a mixer 22. FIG. 5 is an example of a conceptual diagram illustrating processing performed by a low-pass filter 24. FIG. 6 is an example of a conceptual diagram illustrating processing performed by a high-pass filter 26. FIG. 7 is an example of a conceptual diagram illustrating processing performed by an amplifier circuit 40. FIG. 8 is an example of a flow diagram of a biological information measurement method using the biological information measurement device 10a. FIG. 9 is an example of a block diagram illustrating the configuration of a biological information measurement device 10b. FIG. 10 is an example of a circuit diagram illustrating an example of a specific configuration of a separator 28, an amplifier circuit 40, and a multiplexer 42. FIG. 11 is an example of a circuit diagram illustrating another example of a specific configuration of a separator 28, an amplifier circuit 40, and a multiplexer 42. FIG. 12 is an example of a flow diagram of a biological information measurement method using the biological information measurement device 10b. FIG. 13 is an example of a block diagram illustrating the configuration of a biological information measurement device 10c. FIG. 14 is an example of a conceptual diagram illustrating the operation of a high-pass filter 30. 1 is a conceptual diagram illustrating an example of the operation of the notch filter 32. Ｎ The signal V is amplified and output. Ａ５FIG. 1 is an example of a conceptual diagram for explaining the above. FIG. 2 is an example of a flow diagram of a biological information measurement method using the biological information measurement device 10c. FIG. 3 is a diagram showing an example of the configuration of an AC signal supply unit 50b. FIG. 4 is a diagram showing an example of the configuration of an AC signal supply unit 50c. FIG. 5 is a diagram showing an example of the configuration of an AC signal supply unit 50d. FIG. 6 is a diagram showing an example of a modified form of the embodiment of FIG. 2 in which all components other than the bioimpedance measurement unit 100a are replaced. FIG. 7 is a block diagram showing an example of the configuration of the biological information measurement device 10d.

[0018] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention as claimed. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0019] In this specification, when referring to variations of the same element, they may be referred to by adding an alphabetical letter, such as bioimpedance measurement unit 100a, bioimpedance measurement unit 100b, etc. On the other hand, these components may also be referred to collectively, such as bioimpedance measurement unit 100.

[0020] Wristband controllers or myoelectric prosthetic hands are known that predict human movements by detecting myoelectric potentials generated immediately before a human moves, and then control an object in accordance with the predicted human movements. Devices such as wristband controllers that detect the movements of living organisms, such as humans, are equipped with biosensors such as myoelectric sensors, and sense bioinformation such as myoelectric potentials or bioimpedance to predict bioinformation about the living organism, such as the movements of the living organism.

[0021] 1 is an example of a schematic diagram illustrating the bioimpedance BioZ generated in a living body 300. The living body 300 includes an epidermis layer 302, a dermis and subcutaneous layer 304, and a muscle layer 306.

[0022] In this embodiment, the living body 300 is a human being. However, the living body 300 may be another animal. If the living body 300 is another animal, the structure of the skin of the living body 300 may differ depending on the type of the living body 300.

[0023] In measuring bioimpedance BioZ, a pair of electrodes 150 are fixed in contact with the living body 300, and a constant current is passed between the electrodes. In this case, by reading the potential difference generated between the electrodes 150, the bioimpedance BioZ based on the body composition of the living body 300 can be read.

[0024] Furthermore, for example, when the living organism 300 activates a muscle, an action potential is generated by electrical excitation of cells in the muscle layer 306 of the living organism 300. Measurement of such an action potential is affected by impedances resulting from the epidermal layer 302 and the dermis and subcutaneous layer 304.

[0025] The epidermis layer 302 is the epidermis of the living body 300. For example, if the living body 300 is a human, the epidermis layer 302 is the part of the skin other than the palms of the hands or the soles of the feet, having an average thickness of about 0.2 mm.

[0026] The epidermis layer 302 is connected to the electrode 150 at a half-cell potential V ＨＣ and the half-cell potential V ＨＣ A variable resistor R ＥＳＩ and variable capacitance C ＥＳＩ The half-cell potential V ＨＣ is the electrostatic potential generated at the contact point between the electrode 150 and the skin layer 302. ＨＣ The component contributes to the measurement of bioimpedance BioZ as a component with a frequency of, for example, 20 Hz or less. In bioimpedance BioZ, the contribution of the contact impedance between the electrode 150 and the skin of the living body 300, i.e., the electrode 150 and the epidermis layer 302, is large. Furthermore, the epidermis layer 302 is connected to the half-cell potential V ＨＣ A variable resistor R ＥＳＩ and variable capacitance C ＥＳＩ The variable resistor R ＥＳＩ and variable capacitance C ＥＳＩvaries significantly depending on the condition of the skin surface. This appears as a variation in the contact impedance between the electrode 150 and the skin of the living body 300 in the bioimpedance BioZ. When the skin surface is dry, these impedances increase by about 10 times, and are therefore expressed as variable resistance and capacitance in the equivalent circuit.

[0027] The dermis and subcutaneous layer 304 includes layers such as the dermis layer, subcutaneous tissue, and fascia. In measuring bioimpedance, the dermis and subcutaneous layer 304 has a resistance R ｂｏｄｙ The dermis and subcutaneous layer 304 contributes to the electrical resistance of the skin. The dermis layer of the dermis and subcutaneous layer 304 is a part of the skin through which capillaries, lymphatic vessels, nerves, etc. pass, and is formed inside the epidermis layer 302. For example, if the living body 300 is a human, the dermis layer is a part having an average thickness of about 2 mm. Of the dermis and subcutaneous layer 304, subcutaneous tissue is formed further inside the dermis layer. The subcutaneous tissue is a part that supports the epidermis layer 302 and the dermis layer, and is a part having an average thickness of about 2 mm to about 9 mm. The subcutaneous layer mainly contains fat cells, and includes large blood vessels, etc. Furthermore, the dermis and subcutaneous layer 304 includes fascia between the subcutaneous tissue and the muscle layer 306. The fascia is about 1 mm thick, and although it is not as large as the skin, it is a part that generates electrical resistance. The resistance R of the dermis and subcutaneous layer 304 ｂｏｄｙ is the resistance value obtained by adding up the electrical resistances of these multiple layers.

[0028] In the end, in the impedance measurement of the living body 300, what contributes to the bioimpedance BioZ is the variable resistance R ＥＳＩ and variable capacitance C ＥＳＩ and resistance R ｂｏｄｙ This becomes:

[0029] The muscle layer 306 is a layer that includes multiple muscle fibers 308. The muscle fibers 308 are tissues that are activated by electrical signals transmitted through nerves 310. When the muscle fibers 308 move, an action potential is generated within the muscle fibers 308. In the muscle layer 306, a potential V is generated that is the sum (composite) of the action potentials of multiple muscle fibers as multiple muscles are activated. ＥＭＧ (compound action potential V ＥＭＧ In measuring myoelectric signals, such a compound action potential V ＥＭＧMeasurements are taken.

[0030] A myoelectric signal is an example of a "biopotential signal." A myoelectric signal may have an amplitude peak in a frequency band higher than 20 Hz and equal to or lower than 4 kHz, for example. As another example, a biopotential signal may be a signal indicating an electric potential generated by the activity of a living organism, such as an electrocardiogram, an electroencephalogram, or a nystagmus. Note that these biopotential signals are merely examples, and biopotential signals are not limited to these signals as long as they are signals based on the action potential of the living organism 300 generated by the activity of the living organism 300.

[0031] For example, if the biopotential signal is an electrocardiogram signal, the electrocardiogram signal may have an amplitude peak in a frequency band higher than 0.05 Hz and lower than 100 Hz. As another example, if the biopotential signal is an electroencephalogram signal, the electroencephalogram signal may have an amplitude peak in a frequency band higher than 0.5 Hz and lower than 70 Hz. As yet another example, if the biopotential signal is a nystagmus signal, the nystagmus vibration may have an amplitude peak in a frequency band higher than 0.05 Hz and lower than 20 Hz. The following description will be given taking as an example a case where the biopotential signal is an electromyogram signal. However, the biopotential signal is not limited to an electromyogram signal and may be another biopotential signal.

[0032] Here, when measuring bioimpedance BioZ, if the living body 300 moves, the electrode 150 may shift relative to the living body 300, or the living body 300 may vibrate, which may result in motion artifacts (MA) occurring at the contact point between the electrode 150 and the living body 300, which may appear as measurement noise.

[0033] The MA generated when the living body 300 moves often has a peak below 20 Hz, for example, if the living body 300 is a human. The influence of such MA can be blocked by a high-pass filter, which will be described later. However, even if the frequency band in which the MA peak appears is 20 Hz or less, if the peak value of MA is large, the influence of the MA lingers from the peak in the frequency band above 20 Hz.

[0034] On the other hand, the vibrations occurring in the living body 300 are, for example, vibrations occurring in moving bodies such as trains, buses, and airplanes on which people are riding. MA occurring when the living body 300 is riding on a moving body can be directly mixed as noise in a frequency band of, for example, 50 Hz or more and less than 200 Hz. In this case, MA is known to contribute as a fluctuation in the capacitive component, and C ＥＳＩ Furthermore, the variation in bioimpedance BioZ due to MA may have a frequency greater than a predetermined frequency (for example, 20 Hz).

[0035] Therefore, the variable capacitance C ＥＳＩ In the measurement of MA, by blocking components in an appropriate frequency range and amplifying the blocked components, it becomes possible to read the fluctuation of the capacitive element proportional to MA, and thus to read the fluctuation of the bioimpedance due to MA. ＥＳＩ The configuration of a biological information measuring device capable of reading fluctuations in blood pressure will be described in detail below.

[0036] 2 is a block diagram showing an example of the configuration of the biological information measurement device 10a. The biological information measurement device 10a includes an AC signal supply unit 50, a bioimpedance measurement unit 100a, and electrodes 150a and 150b.

[0037] The AC signal supply unit 50 supplies a square-wave AC signal that alternately switches on and off between a pair of electrodes 150 a, 150 b that contact the living body. That is, the AC signal supply unit 50 supplies an AC signal modulated at a reference frequency between the pair of electrodes 150 a, 150 b that contact the living body. The AC signal supply unit 50 includes a power supply 52, a chopper 54, and a limiting unit 56.

[0038] The power supply 52 is, for example, a DC power supply such as a battery.

[0039] The chopper 54 converts the DC voltage supplied from the power supply 52 into a signal that turns on and off at a constant cycle. That is, the chopper 54 outputs a rectangular wave whose output potential switches at a constant cycle. The chopper 54 operates at a reference frequency f ｍｏｄIn order to switch the potential of the rectangular wave at a period (for example, a frequency of 10 kHz or more and 100 kHz or less), a reference frequency signal V ｆｍｏｄ In this case, the chopper 54 may receive the voltage from the DC power supply at a reference frequency f ｍｏｄ The chopper 54 functions as a "voltage output circuit" that outputs a voltage signal by switching at a period of, for example, 1 / f ｍｏｄ It includes a switching element that turns on and off.

[0040] The limiting unit 56 receives the square wave voltage signal output from the chopper 54 and limits the reference frequency f ｍｏｄ The current signal according to the formula (1) is output from the AC signal supply unit 50 as an AC signal flowing through the electrodes 150a and 150b, and in this case, the limiting unit 56 limits the magnitude of the current flowing through the living body 300. The limiting unit 56 includes, for example, a resistor.

[0041] The bioimpedance measuring unit 100a measures the bioimpedance BioZ by reading a signal Vs indicating the potential difference generated between the pair of electrodes 150a, 150b in contact with the living body 300 when a square wave current is passed through the pair of electrodes 150a, 150b. The bioimpedance measuring unit 100a includes a high-pass filter 12, a first amplifier 20a, and an ADC (Analog to Digital Converter) 45.

[0042] The high-pass filter 12 extracts the reference frequency f from the signal Vs. ｍｏｄ a frequency band (for example, a frequency band of 100 Hz or less) lower than the first frequency band (for example, a frequency band of 28 kHz or more and 36 kHz or less), including the cutoff frequency f Ｃ１ = 100 Hz.) is shielded, and the signal V Ｈ１ The reference frequency f ｍｏｄ corresponds to the center value of the first frequency band. Therefore, the example shown in this embodiment uses the reference frequency f ｍｏｄ = 32 kHz, and the first frequency band has a reference frequency f ｍｏｄ This is an example where the range is set to ±4 kHz.

[0043] Here, the half-cell potential V when measuring the bioimpedance BioZ is ＨＣ The frequency of the signal generated by V is lower than a certain frequency (e.g., 20 Hz). Therefore, filtering by the high-pass filter 12 reduces the frequency of the signal V Ｓ Half-cell potential V ＨＣ That is, the cutoff frequency f of the high-pass filter 12 is ｃ１ is the reference frequency f ｍｏｄ lower and at half-cell potential V ＨＣ The frequency of the component of the potential occurring at the half-cell potential V ＨＣ The frequency of the potential component generated at may be determined based on the average value of measurements previously measured through experiments or the like.

[0044] The processing performed by the high-pass filter 12 is specifically shown in FIG. 3A. FIG. 3A is an example of a conceptual diagram explaining the processing performed by the high-pass filter 12. In FIGS. 3A to 3E, the horizontal axis represents frequency and the vertical axis represents the magnitude of the signal amplitude, and an outline of the signal output by the processing performed by each component of the first amplifier unit 20a is explained. In particular, FIG. 3A shows the signal V output after the processing performed by the high-pass filter 12. Ｈ１ An overview of the project will be explained.

[0045] The signal V supplied to the high-pass filter 12 Ｓ is a signal indicating the potential difference occurring between the pair of electrodes 150a and 150b in contact with the living body 300. Ｓ is an action potential component 72 appearing near the 0 frequency and a reference frequency f ｍｏｄ and a bioimpedance component 70 that appears in the vicinity.

[0046] The bioimpedance component 70 has a reference frequency f ｍｏｄThe bioimpedance BioZ has an average value component of the bioimpedance BioZ near the average value component, and includes a fluctuation component of the bioimpedance BioZ as a component other than the average value component. In the figure, the frequency band in which the bioimpedance component 70 appears is shown as the first frequency band, and the frequency band including the average value of the bioimpedance component 70 is shown as the second frequency band (e.g., a frequency band of 31.98 kHz or more and 32.02 kHz or less). In other words, the fluctuation component of the bioimpedance BioZ is shown as the portion of the bioimpedance component 70 included in the first frequency band, excluding the component included in the second frequency band.

[0047] On the other hand, the action potential component 72 is a half-cell potential V ＨＣ Furthermore, the action potential component 72 includes, in a band other than the range including the half-cell potential component 73, a component that is a combination of action potentials from each of the multiple biological tissues (e.g., muscle fiber 308) that make up the living body 300.

[0048] Here, it is known that in the measurement of bioimpedance BioZ, the fluctuation component of bioimpedance BioZ includes a component proportional to the motion artifact. Also, the fluctuation component of bioimpedance component 70 includes the amplitude due to the contribution of action potential component 72 near the 0 frequency and the reference frequency f ｍｏｄ The amplitude of the signal is very small compared to the average value of the bioelectrical impedance component 70 that appears nearby, for example, it is a signal having an amplitude of about one hundredth.

[0049] The bioimpedance component 70 measured as an analog signal can be converted into a digital signal by an ADC. Each ADC has a dynamic range, which is a value determined by the ratio of the maximum and minimum values ​​of the signal it can process. If the bioimpedance component 70 is amplified without proper signal filtering by frequency in order to amplify the fluctuation component, the contribution of the action potential component 72 and the reference frequency f ｍｏｄ The contribution of the average value of the bioelectrical impedance component 70 appearing in the vicinity becomes large, and the requirements for the dynamic range of the ADC 45 may become strict.

[0050] For example, in the bioimpedance measuring device disclosed in Patent Document 1, the common voltage of the impedance signal amplifier is adjusted while monitoring the output range of the ADC, thereby subtracting the impedance average value component. Furthermore, in the biosignal measuring device having a bioimpedance measuring unit disclosed in Patent Document 2, the impedance average value component is subtracted by supplying a correction current based on the average value of the ADC output to the impedance signal amplifier. Feedback control such as that performed in Patent Documents 1 and 2 cannot follow fluctuations in the average value of bioimpedance due to electrode misalignment, and this can lead to stricter requirements for the dynamic range of the ADC in design.

[0051] Patent Document 3 describes an electro-medical device for simultaneously measuring impedance and biopotential signals, but this electro-medical device does not have a configuration for extracting the fluctuation component of the bioimpedance component 70 during impedance measurement.

[0052] Therefore, it is desirable to simultaneously measure the bioimpedance BioZ and the biopotential signal and to more accurately extract only the fluctuation components of the bioimpedance component 70. If only the fluctuation components of the bioimpedance component 70 with small amplitudes can be extracted with high accuracy, the requirements for the dynamic range of the ADC used to perform AD conversion of the fluctuation components can be alleviated. The dynamic range of the ADC is a resolution that indicates the ratio (signal-to-noise ratio) of the maximum amplitude of a sine wave handled in AD conversion to errors including, for example, quantization errors.

[0053] Therefore, in such a device, even if the contact impedance between the electrodes 150a, 150b and the living body 300 changes sharply due to vibrations occurring in the living body 300, it is desirable to extract the noise component with high precision and eliminate the influence of MA that is mixed in from the measured living body impedance. The living body impedance measuring unit 100a of this embodiment has a high-pass filter 12 and a first amplifier 20a, so that the signal V Ｓ This makes it possible to remove components other than the fluctuation component of the bioelectrical impedance component 70 with high accuracy.

[0054] The high-pass filter 12 has a cutoff frequency f Ｃ１ The potential that may remain in the vicinity of the action potential component 72 after the high-pass filter 12 blocks the lower frequency band is the residual component 74. The residual component 74 is located at the cutoff frequency f Ｃ１ is set low enough to shield the contribution of the half-cell potential component 73 from the action potential component 72, the biopotential signal V ＥＭＧ However, in the bioelectrical impedance measuring section 100a, the bioelectrical potential signal V ＥＭＧ Since the measurement itself is not performed, 、 In the high-pass filter 12, the cutoff frequency f is set to 0 so that the residual component 74 does not remain. Ｃ１ The signal V output from the high-pass filter 12 may be set to a value other than the reference value. Ｈ１ includes a bioimpedance component 70 and a residual component 74 .

[0055] The high-pass filter 12 may be a so-called active filter, which is configured by connecting a resistor and a capacitor to a terminal to which a voltage to be amplified is input in an inverting or non-inverting amplifier circuit configured with an operational amplifier. When such an active filter is used, the cutoff frequency f Ｃ１ In this way, by using an active filter as the high-pass filter 12, the signal V after blocking is amplified. Ｈ１ If you want to obtain a signal with a large amplitude, use the amplified signal as signal V Ｈ１ Furthermore, when an active filter is used, the number of stages of resistors and capacitors included in the active filter is not limited. In other words, the order of the filter is not limited, and a filter having a desired order may be used.

[0056] The first amplifier 20a in FIG. 2 amplifies the signal V output from the high-pass filter 12. Ｈ１ From the reference frequency f ｍｏｄand shielding a second frequency band narrower than the first frequency band. In the first frequency band, the contribution from the average value of the bioimpedance BioZ is smaller than the reference frequency f ｍｏｄ The contribution of the fluctuation component of the bioimpedance BioZ appears near the reference frequency f ｍｏｄ Therefore, the blocking of the second frequency band by the first amplifier 20a is equivalent to blocking the contribution of the average component of the bioimpedance BioZ and extracting the contribution of the fluctuation component of the bioimpedance BioZ. The first amplifier 20a includes a mixer 22, a low-pass filter 24, a high-pass filter 26, and an amplifier circuit 40.

[0057] 3B is an example of a conceptual diagram illustrating the process performed by the mixer 22. The signal V Ｈ１ The mixer 22 receives the signal V Ｈ１ The reference frequency f ｍｏｄ By mixing the signals representing Ｈ１ is a signal V in a third frequency band (for example, a frequency band of 4 kHz or less) lower than the first frequency band. Ｒ Convert to.

[0058] Specifically, the mixer 22 receives the signal V Ｈ１ Reference frequency signal V ｆｍｏｄ By mixing these, the signal V Ｈ１ A signal V Ｒ 3B indicates the processing by the mixer 22. The mixer 22 outputs a signal V Ｈ１ The third frequency band has a bandwidth that includes the bioimpedance component 70 and a lower limit value of the frequency 0. The bandwidth that includes the bioimpedance component 70 may be set based on the average value of the bioimpedance component measured in advance by an experiment or the like.

[0059] After this mixing process, most of the bioimpedance component 70 and the residual component 74 are shifted to near the zero frequency, and the reference frequency f ｍｏｄNear, reference frequency f ｍｏｄ Twice the frequency 2f ｍｏｄ For the sake of explanation, a portion of the signal remains in the vicinity. ｍｏｄ Near, reference frequency f ｍｏｄ Twice the frequency 2f ｍｏｄ Signals appearing in the vicinity are shown with exaggerated magnitude. By shifting the bioimpedance component 70 and the residual component 74 to near 0 frequency, signal processing for extracting the fluctuation components of the bioimpedance BioZ after the mixer 22 can be performed in the low frequency band. Therefore, the process for extracting the fluctuation components of the bioimpedance BioZ can be performed with less power consumption than processing in the high frequency band.

[0060] The low-pass filter 24 in FIG. Ｒ from the third frequency band, which is higher than the reference frequency band f ｍｏｄ A fourth frequency band (e.g., a frequency band above 10 kHz) including the signal V Ｒ The processing performed by the low-pass filter 24 for the above is specifically shown in FIG. 3C.

[0061] 3C is an example of a conceptual diagram illustrating the process performed by the low-pass filter 24. The lower limit frequency of the fourth frequency band (cutoff frequency f Ｃ２ In this embodiment, for example, the cutoff frequency f Ｃ２ = 6 kHz. The frequency f ) may be predetermined based on the reference frequency band fmod within a range that does not include the third frequency band.

[0062] The third frequency band is the signal V Ｈ１ The fourth frequency band is a frequency band in which the bioimpedance component 70 of the reference frequency f appears after being shifted to the vicinity of 0 frequency. ｍｏｄ The shift residual component 75 that appears in the vicinity and the reference frequency f ｍｏｄ Twice the frequency 2f ｍｏｄ The low-pass filter 24 has a cutoff frequency f that is higher than the third frequency band and lower than the fourth frequency band. Ｃ２ It has.

[0063] signal VＦ is the signal V Ｈ１ , the signal V corresponds to a signal obtained by shifting the components of the first frequency band outside the second frequency band. Ｈ１ , the signal corresponds to the component of the first frequency band outside the second frequency band.

[0064] The low-pass filter 24 filters the signal V Ｒ For the cutoff frequency f Ｃ２ By blocking the higher frequency band, the signal V Ｌ１ Thus, the low-pass filter 24 functions as an anti-aliasing filter that blocks the contribution of high frequencies that may be aliased back from the ADC 45. Note that a fifth frequency band is shown in FIG. 3C as a frequency band that is included in the third frequency band, and this frequency band will be described below with reference to FIG. 3D.

[0065] Next, the high-pass filter 26 in FIG. 2 converts the signal V output from the low-pass filter 24 Ｌ１ to the cutoff frequency f in the third frequency band Ｃ３ The lower frequency band is blocked, and the signal V Ｆ The signal V output from the high-pass filter 26 Ｆ 3D is an example of a conceptual diagram illustrating the processing performed by the high-pass filter 26. In FIG. 3D, the average component of the bioimpedance component 70, which has been shifted to near 0 frequency, appears in the third frequency band, particularly in a band close to 0 frequency.

[0066] Therefore, the high-pass filter 26 converts the bioimpedance component 70 shifted to near zero frequency into a cutoff frequency f Ｃ３ (e.g., 20 Hz) to block signals in a frequency band lower than the cutoff frequency f. The contribution of the average value of the bioimpedance component 70 appears in a frequency band 78 close to the zero frequency in the third frequency band, even after the bioimpedance component 70 is shifted to the vicinity of the zero frequency. Ｃ３By blocking the lower frequency band 78, the contribution of the average value of the bioimpedance component 70 is blocked. In this case, the contribution of a signal resulting from shifting the residual component 74 of the action potential component 72 to the 0 frequency band is also included in the frequency band 78. By blocking the frequency band 78, the high-pass filter 26 also blocks the contribution from the residual component 74.

[0067] Therefore, the signal V remaining after the high-pass filter 26 is filtered out Ｆ The component corresponds to a frequency band including the fluctuation component 79 of the bioimpedance component. Ｃ３ may be set to a frequency similar to the cutoff frequency of the high-pass filter 212, which will be described later with reference to FIG. 14. In this case, the cutoff frequency f Ｃ３ The frequency band below the upper limit of the third frequency band (for example, 20 Hz or more and less than 4 kHz) is an example of a fifth frequency band, which will be described later. Ｃ３ may be determined based on the average value of the bioelectrical impedance component 70 measured in advance by an experiment or the like.

[0068] The amplifier circuit 40 of FIG. Ｆ is amplified, and a signal V Ａ２ 3E shows the signal V output from the amplifier circuit 40. Ａ２ 3E is an example of a conceptual diagram illustrating the processing performed by the amplifier circuit 40. The amplifier circuit 40 amplifies the fluctuation component 79 of the bioelectrical impedance to generate a signal V Ａ２ Output.

[0069] Alternatively, an active filter configured by combining an operational amplifier, a resistor, and a capacitor and capable of performing both shielding and amplification may be used as the low-pass filter 24 or the high-pass filter 26. In this case, the amplifier circuit 40 may be omitted. Furthermore, the active filter used in this case may have a desired order.

[0070] The ADC 45 in FIG. 2 receives the analog signal V Ａ２is converted into a digital signal V Ｂ１ The signal V Ａ２ or signal V Ａ２ The signal V obtained by AD conversion Ｂ１ is an example of a “biological information signal” indicating the fluctuation component 79 of the bioelectrical impedance component 70 of the living body 300 .

[0071] signal V Ｓ Signal V Ａ２ In the process of acquiring the signal V, contributions other than the fluctuation components of the bioimpedance component 70 are removed by processing such as the high-pass filter 12, the mixer 22, the low-pass filter 24, and the high-pass filter 26. Ａ２ In this case, the contribution of components with large amplitudes other than the fluctuation components of the bioelectrical impedance component 70 is excluded, and the requirement for the dynamic range of the ADC 45 is alleviated. Therefore, the biological information measurement device 10a can reduce the requirement for the dynamic range of the ADC 45 when the amplitude of the signal to be AD converted is reduced, and the signal V obtained by digitally converting the component proportional to the motion artifact is Ｂ１ When the ADC 45 with relaxed dynamic range requirements is used, it is possible to use an ADC with low power consumption and a small area (small footprint). This allows the IC in which the ADC 45 is provided (for example, the IC may be configured to include the entire biological information measurement device 10a) to be configured with low power consumption and a small area.

[0072] Furthermore, due to the action of the mixer 22, the signal V Ａ２ The frequency band of is shifted to a low frequency band near frequency 0. This reduces the power consumption required for the ADC 45 to perform AD conversion.

[0073] The high-pass filter 12 is an example of a "first high-pass filter." Ｓ is an example of a "first signal", and the signal V Ｈ１ is an example of a "second signal", and the signal V Ｆ is an example of a "third signal."

[0074] The mixer 22 is an example of a "first mixer," the low-pass filter 24 is an example of a "first low-pass filter," and the high-pass filter 26 is an example of a "second high-pass filter."

[0075] 4 is an example of a flow diagram of a biological information measurement method using the biological information measurement device 10a. The biological information measurement method using the biological information measurement device 10a includes steps S100 to S114.

[0076] The chopper 54 converts the DC voltage supplied from the power supply 52, which is a DC power source, into a reference frequency f ｍｏｄ The limiting unit 56 outputs a signal that switches the voltage level (potential) at a reference frequency f in response to the square wave voltage output from the chopper 54 (S100). ｍｏｄ A current that switches between the voltages is supplied (S102).

[0077] The bioimpedance measuring unit 100a reads a signal Vs indicating a potential difference generated between the pair of electrodes 150a and 150b in contact with the living body 300 when a rectangular wave current is applied to the pair of electrodes 150a and 150b. The high-pass filter 12 filters the signal Vs. Ｓ to the cutoff frequency f ｍｏｄ Lower frequencies are blocked to reduce the signal V Ｈ１ (S104). The mixer 22 outputs the signal V Ｈ１ is the reference frequency signal V ｆｍｏｄ Mixing with the signal V near 0 frequency Ｒ (S106).

[0078] The low-pass filter 24 filters the signal V Ｒ to the cutoff frequency f Ｃ２ Higher frequencies are blocked to reduce the signal V Ｌ１ (S108). The high-pass filter 26 outputs the signal V Ｌ１ to the cutoff frequency f Ｃ３ Lower frequencies are blocked to reduce the signal V Ｆ is output (S110).

[0079] The amplifier circuit 40 outputs the signal V Ｆ is amplified to produce a signal V Ａ２(S112). The ADC 45 outputs the signal V Ａ２ is converted to analog-to-digital (AD) signal V Ｂ１ The above-described biological information measurement method using the biological information measurement device 10a makes it possible to extract with high accuracy the fluctuation components of the bioelectrical impedance BioZ, including components proportional to the motion artifact, using a device equipped with a low-power, small-area IC.

[0080] 5 is an example of a block diagram showing the configuration of the biological information measurement device 10b. The biological information measurement device 10b differs from the biological information measurement device 10a in that it includes a bioelectrical impedance measurement unit 100b.

[0081] The following description will mainly focus on the differences between the bioelectrical impedance measuring unit 100a described with reference to Fig. 2 and the bioelectrical impedance measuring unit 100b shown in Fig. 5. The bioelectrical impedance measuring unit 100b includes a high-pass filter 12, a first amplifier 20b, an amplifier circuit 40, a multiplexer 42, and an ADC 45.

[0082] Therefore, the bioimpedance measuring unit 100b differs from the bioimpedance measuring unit 100a in that it includes an amplifier circuit 14, a first amplifier unit 20b, and a multiplexer 42, as well as in the connection relationship between the first amplifier unit 20b, the multiplexer 42, and the ADC 45.

[0083] Similar to the bioimpedance measuring unit 100a, the bioimpedance measuring unit 100b generates a signal V based on the potential difference generated between the electrodes 150a and 150b in contact with the living body 300. Ｓ Measure.

[0084] The amplifier circuit 14 outputs the signal V Ｈ１ is amplified to produce a signal V Ａ１ This outputs the signal V ＳThe contribution of the bioimpedance component 70 in the first frequency band and the contribution of the residual component 74 of the action potential component 72 excluding the half-cell potential component 73 are amplified. Here, the high-pass filter 12 can be configured as an active filter using an operational amplifier, resistors, and capacitors, so that both the amplification process by the amplifier circuit 14 and the shielding process by the high-pass filter can be performed. In this way, when the high-pass filter 12 is configured as an active filter, or when the signal V Ｈ１ If the amplitude of the signal is large enough to be processed in the subsequent circuit, the amplifier circuit 14 may be omitted, as in the biological information measurement device 10a.

[0085] In the bioimpedance measuring unit 100b, the configuration of the first amplifier unit 20b is different from that of the first amplifier unit 20a, so that the first amplifier unit 20b outputs the signal V Ａ１ The first amplifier 20b includes a mixer 22, a low-pass filter 24, a separator 28, and an amplifier circuit 40. The first amplifier 20b also differs from the bioimpedance measurement unit 100a in the method of removing the average component of the bioimpedance component 70 from the bioimpedance measurement unit 100a.

[0086] In the first amplifier 20b, the mixer 22 outputs the signal V Ａ１ A signal V shifted from Ｒ and the low-pass filter 24 outputs the signal V Ｒ is shielded to block the signal V Ｌ１ The first amplifier 20b is similar to the first amplifier 20a described in FIG. Ｌ１ , components close to 0 frequency in the third frequency band (DC components, for example, components below 20 Hz) are separated from other components (for example, components in frequency bands higher than 20 Hz).

[0087] The separator 28 divides the signal V Ｒ is a signal V of components in a frequency band lower than the first frequency (for example, 20 Hz) in the third frequency band. ＤＣ and a signal V of components in a frequency band higher than the first frequency. ＡＣ Specifically, the separator 28 separates the signal V Ｒ In the third frequency band, the DC component signal VＤＣ and a signal V of an AC component, which is another component in the third frequency band. ＡＣ As described with reference to FIG. 2, a signal having a component proportional to the motion artifact among the bioimpedance components 70 of the living body appears as a fluctuation component of the bioimpedance components 70. ＡＣ is a signal V obtained by shifting the bioimpedance component 70 to the 0 frequency band. Ｒ and includes the fluctuation component of the bioimpedance component 70.

[0088] The separator 28 divides the signal V Ｒ DC component signal V ＤＣ is output to the ADC 45 via the multiplexer 42. Meanwhile, the separator 28 outputs the signal V ＡＣ After being amplified, the signal V ＡＣ The signal V ＡＣ is another example of a "third signal."

[0089] The amplifier circuit 40 outputs the signal V ＡＣ is amplified and input to the multiplexer 42 as the signal V Ａ３ The signal V ＡＣ The amplitude of the signal V ＤＣ Since the signal V is smaller than the reference signal V, the variation component of the bioimpedance component 70 is amplified by the amplifier circuit 40 to a signal with an amplitude that can be processed as a digital signal. ＡＣ and signal V ＤＣ The amplitude difference between the

[0090] The multiplexer 42 receives the signal V Ａ３ or signal V ＤＣ to the ADC 45. For example, the multiplexer 42 in this embodiment selectively outputs the signal V Ａ３ to the ADC 45. Here, the multiplexer 42 outputs a differential signal based on the signal V Ａ３ and signal V ＤＣ may be output to the ADC 45 in a time-division manner, for example.

[0091] The ADC 45 converts the signal output from the multiplexer 42 into a signal V Ｂ２The signal V Ａ３ , or signal V Ａ３ The signal V obtained by AD conversion Ｂ２ is another example of a “biological information signal” indicating the fluctuation component of the bioelectrical impedance BioZ of the living body 300.

[0092] 6A and 6B are circuit diagrams showing an example of a specific configuration of the separator 28, the amplifier circuit 40, and the multiplexer 42. In FIG. 6A, the separator 28 includes an adder 282 and an integrator 284. The separator 28 forms a so-called DC servo circuit, thereby controlling the signal V Ｒ 6B, the separator 28 includes an adder 282 and a low-pass filter 285. The separator 28 separates the DC component from other components in the signal V Ｒ Extract only the DC component in V Ｒ By subtracting from V Ｒ The DC and AC components are separated.

[0093] 5 shows a configuration in which two signal lines are input to the separator 28 in a differential configuration, but for convenience of explanation, FIGS. 6A and 6B show a separator 28 in which one signal line is input to the separator 28 in a single-ended configuration. However, the biological information measurement device 10b including the separator 28 is not limited to the single-ended configuration, and the entire biological information measurement device 10b may have a fully differential configuration in which two signal lines are used.

[0094] 6A, the integrator 284 integrates the output signal of the adder 282 and feeds it back to the minus input terminal of the adder 282. The input to the separator 28 is the sum of a DC component and an AC component around the DC component, and since the integral value of the AC component having a constant period is 0, the integral value of both is the sum (integral) value of the DC component, and the output value of the integrator 284 is a value reflecting the DC component. Therefore, by feeding back the output of the integrator 284 to the minus input terminal of the adder 282, the separator 28 ultimately ＡＣ as an AC component, and the signal V ＤＣis output as a DC component.

[0095] 6B, the low-pass filter 285 cuts off only the AC component of the output signal of the adder 282 and feeds it forward to the minus input terminal of the adder 282. Since the input to the separator 28 is the sum of the DC component and the AC component around the DC component, by feeding forward the output of the low-pass filter 285 to the minus input terminal of the adder 282, the separator 28 ultimately cuts off the signal V ＡＣ is output as an AC component, and the signal V ＤＣ is output as a DC component.

[0096] The adder 282 may be configured by combining an operational amplifier and an amplifier circuit 40 that is an inverting amplifier or a non-inverting amplifier using a resistor or a capacitance.

[0097] 6A, the integrator 284 may have an analog configuration using resistors, capacitance, and an operational amplifier. Alternatively, the integrator 284 may be configured with an ADC that performs analog-to-digital (AD) conversion of the adder output, a digital calculator that integrates the AD converter output, and a DAC that performs digital-to-analog (DA) conversion of the digital calculator output.

[0098] 6B, the low-pass filter 285 may be an analog filter using resistors, capacitances, and an operational amplifier. Alternatively, the low-pass filter 285 may be configured with an ADC that performs analog-to-digital (AD) conversion of the adder output, a digital calculator that blocks AC components from the AD converter output, and a DAC that performs digital-to-analog (DA) conversion of the digital calculator output.

[0099] DC component signal V ＤＣ Compared to the AC component signal V ＡＣ Since the amplitude of the signal V is small, the amplifier circuit 40 ＡＣ is further amplified to produce a signal V Ａ３ The signal V ＡＣis a signal V obtained by shifting the bioimpedance component 70 to the 0 frequency band. Ｒ and includes the fluctuation component of the bioimpedance component 70.

[0100] When the bioelectrical impedance measuring unit 100b has a multiplexer 42, the DC component signal V ＤＣ and the AC component signal V ＡＣ The DC component signal V can be selected and output to detect the component proportional to the motion artifact among the bioimpedance components 70. ＤＣ does not contribute, but V ＤＣ By separating and extracting the above, the bioelectrical impedance measuring section 100b can also measure the average value component of the bioelectrical impedance component 70.

[0101] 7 is an example of a flow diagram of a biological information measurement method using the biological information measurement device 10b. The biological information measurement method using the biological information measurement device 10b includes steps S200 to S216.

[0102] The chopper 54 converts the DC voltage supplied from the power supply 52, which is a DC power source, into a reference frequency f ｍｏｄ The limiting unit 56 outputs a signal that switches the voltage level (potential) at a reference frequency f in response to the square wave voltage output from the chopper 54 (S200). ｍｏｄ A current that switches between the voltages is supplied (S202).

[0103] The bioimpedance measuring unit 100a reads a signal Vs indicating a potential difference generated between the pair of electrodes 150a and 150b in contact with the living body 300 when a rectangular wave current is applied to the pair of electrodes 150a and 150b. The high-pass filter 12 filters the signal Vs. Ｓ to the cutoff frequency f ｍｏｄ Lower frequencies are blocked to reduce the signal V Ｈ１ (S204). The amplifier circuit 14 outputs the signal V Ｈ１ is amplified to produce a signal V Ａ１ (S206). The mixer 22 outputs the signal V Ａ１ is the reference frequency signal V ｆｍｏｄMixing with the signal V near 0 frequency Ｒ (S208).

[0104] The low-pass filter 24 filters the signal V Ｒ to the cutoff frequency f Ｃ２ Higher frequencies are blocked to reduce the signal V Ｌ１ (S210). The separator 28 outputs the signal V Ｌ１ DC component V ＤＣ and AC component signal V ＡＣ is separated to obtain the AC component signal V ＡＣ is output (S212).

[0105] The amplifier circuit 40 outputs the signal V ＡＣ is amplified to produce a signal V Ａ３ (S214). The ADC 45 outputs the signal V Ａ３ is converted to analog-to-digital (AD) signal V Ｂ２ is output (S216).

[0106] Even if the configuration of the biological information measurement device 10b is used as the configuration of the biological information measurement device 10, it is possible to extract only the fluctuation component of the bioelectrical impedance component 70. Furthermore, as described above, according to the biological information measurement device 10b, the component obtained by shifting the average component of the bioelectrical impedance component 70 to the vicinity of 0 frequency is output as the signal V ＤＣ The component in question is not proportional to the motion artifact that can become noise in biopotential signal measurement in bioimpedance BioZ measurement, but the configuration of the biological information measurement device 10b can be used in applications where measurements are made using the average value of bioimpedance BioZ. Similar to the biological information measurement device 10a, the biological information measurement device 10b and the biological information measurement method using the biological information measurement device 10b can extract the fluctuation component of the bioimpedance component 70 with high accuracy using a device that has a low power consumption and a small area IC.

[0107] In addition, in the biological information measurement device 10b, the signal V Ｓ Signal V ＡＣ In the process of acquiring the signal V ＡＣTherefore, the ADC 45 excludes large amplitude components other than the fluctuation component of the bioimpedance component 70 from the signal V Ａ３ Therefore, the dynamic range of the ADC 45 is relaxed even when AD converting the signal V Ｂ２ can be output.

[0108] Furthermore, due to the action of the mixer 22, the signal V Ａ３ The frequency band of is shifted to a low frequency band near frequency 0. This reduces the power consumption required for the ADC 45 to perform AD conversion.

[0109] 8 is an example of a block diagram showing the configuration of the biological information measurement device 10c. The biological information measurement device 10c differs from the biological information measurement device 10a and the biological information measurement device 10b in that it includes a bioelectrical impedance measurement unit 100c.

[0110] The following description will mainly focus on the differences between the bioelectrical impedance measuring unit 100a in Fig. 2 and the bioelectrical impedance measuring unit 100c in Fig. 8. The bioelectrical impedance measuring unit 100c includes a high-pass filter 30, an amplifier circuit 14, a first amplifier unit 20c, and an ADC 45.

[0111] Therefore, the bioimpedance measuring unit 100c differs from the bioimpedance measuring unit 100a in that it includes an amplifier circuit 14 and a first amplifier 20c. The high-pass filter 30 may be a filter similar to the high-pass filter 12, but for the sake of convenience, the following description will use a filter with a cutoff frequency f 1 that is higher than the frequency band including the action potential component 72 and lower than the first frequency band. Ｃ４ The first amplifier unit 20c includes a notch filter 32 and an amplifier circuit 40.

[0112] In the bioelectrical impedance measuring unit 100c of FIG. 8, similarly to the bioelectrical impedance measuring unit 100a, a signal V based on the potential difference generated between the electrodes 150a and 150b in contact with the living body 300 is generated. ＳNext, measure the cutoff frequency f Ｃ４ A high pass filter 30 having a Ｓ 7. This masks the contribution of the action potential component 72 from

[0113] FIG. 9A shows how the high-pass filter 30 filters the signal V Ｓ to the cutoff frequency f Ｃ４ 1 is a conceptual diagram illustrating an example of the effect of blocking signals in a lower frequency band. Here, the bioimpedance component 80 is a reference frequency f ｍｏｄ The frequency band in which the bioimpedance component 80 appears is shown as the first frequency band, and the frequency band containing the average component of the bioimpedance component 80 is shown as the second frequency band.

[0114] The cutoff frequency f of the high-pass filter 30 Ｃ４ is set to a frequency band higher than the contribution from the action potential component 72 and lower than the first frequency band. Therefore, after the filtering of the high-pass filter 30, the bioimpedance component 80 present in the first frequency band remains. The high-pass filter 30 filters the signal V corresponding to the bioimpedance component 80. Ｈ２ Output.

[0115] The amplifier circuit 14 in FIG. Ｈ２ is amplified to produce a signal V Ａ４ In this embodiment, the amplifier circuit 14 outputs the signal V Ｈ２ However, if the high-pass filter 30 is an active filter, or if the signal in the first frequency band has a sufficient amplitude for processing by subsequent circuits, the amplifier circuit 14 may be omitted. Ａ４ is input to the first amplifier 20c, and the notch filter 32 outputs the signal V Ａ４ The frequency band falling within the attenuation band (stop band) is blocked from the

[0116] FIG. 9B shows the lower limit frequency f Ｌ and the upper limit frequency of the attenuation band f Ｕ A notch filter 32 having a notch filter 32 Ａ４10 is an example of a conceptual diagram for explaining the effect of blocking an attenuation band from a signal.

[0117] The notch filter 32 detects the signal V Ａ４ and blocking a second frequency band from the signal V Ｎ Specifically, the notch filter 32 outputs the lower limit frequency f of the attenuation band. Ｌ and the upper limit frequency of the attenuation band f Ｕ The reference frequency f of the bioimpedance component 80 appears in the second frequency band while blocking the attenuation band of ｍｏｄ The notch filter 32 blocks the nearby high average value components. Ｌ and upper limit frequency f Ｕ If the transition width is narrow and has sharp edges in the nearby frequency band, the notch filter 32 Ａ４ The notch filter 32 filters out the fluctuation components 82a and 82b of the bioimpedance component 80 from the signal V Ｎ The signal V Ｎ is yet another example of the "third signal."

[0118] The amplifier circuit 40 in FIG. Ｎ is amplified to produce a signal V Ａ５ 9C shows that the amplifier circuit 40 outputs the signal V Ｎ The signal V is amplified and output. Ａ５ 1 is an example of a conceptual diagram for explaining the above.

[0119] signal V Ｎ are the fluctuation components 82a and 82b of the bioimpedance component 80. Therefore, the amplifier circuit 40 amplifies the fluctuation components 82a and 82b of the bioimpedance component 80 and outputs amplified fluctuation components 84a and 84b as signals V Ａ５ Output as

[0120] The ADC 45 in FIG. 8 converts the signal V Ａ５ is converted to analog-to-digital (AD) signal V Ｂ３ The signal V Ａ５ or signal V Ａ５ The signal V obtained by AD conversionＢ３ is yet another example of a “biological information signal” indicating the fluctuation component of the bioelectrical impedance BioZ of the living body 300.

[0121] 10 is an example of a flow diagram of a biological information measurement method using the biological information measurement device 10c. The biological information measurement method using the biological information measurement device 10c includes steps S300 to S312. The chopper 54 converts a DC voltage supplied from the power supply 52, which is a DC power source, into a reference frequency f ｍｏｄ The limiting unit 56 outputs a signal that switches the voltage level (potential) at a reference frequency f in response to the square wave voltage output from the chopper 54 (S300). ｍｏｄ A current that switches between the voltages is supplied (S302).

[0122] The bioimpedance measuring unit 100c reads a signal Vs indicating a potential difference generated between the pair of electrodes 150a and 150b in contact with the living body 300 when a rectangular wave current is applied to the pair of electrodes 150a and 150b. Ｓ to the cutoff frequency f ｍｏｄ Lower frequencies are blocked to reduce the signal V Ｈ２ (S304). The amplifier circuit 14 outputs the signal V Ｈ２ is amplified to produce a signal V Ａ４ is output (S306).

[0123] The notch filter 32 extracts the lower limit frequency f of the attenuation band from the bioimpedance component 80. Ｌ Higher attenuation band upper limit frequency f Ｕ By blocking signals in the lower frequency band, the signal V Ｎ (S308) In this way, the bioelectrical impedance measuring unit 100c extracts the fluctuation components 82a and 82b of the bioelectrical impedance component 80.

[0124] Next, the amplifier circuit 40 outputs the signal V Ｎ and amplifying the fluctuation components 82a and 82b to obtain signals V corresponding to amplified fluctuation components 84a and 84b. Ａ５ (S310). The ADC 45 outputs the signal V Ａ５ is converted to analog-to-digital (AD) signal V Ｂ３is output (S312).

[0125] As described above, by changing the configuration of the biological information measurement device 10 to that of the biological information measurement device 10c, or by using the biological information measurement method using the biological information measurement device 10c, it is possible to extract only the fluctuation component of the bioelectrical impedance component 80. Ｓ Signal V Ａ５ In the process of acquiring the signal V, signals with large amplitude other than the fluctuation component of the bioimpedance component 80 are Ａ５ Therefore, when the ADC 45 detects the signal V Ａ３ Therefore, the biological information measurement device 10c can reduce the requirement for the dynamic range of the ADC 45 when the amplitude of the signal to be AD converted is reduced, while the signal V obtained by digitally converting the component proportional to the motion artifact is converted. Ｂ３ can be output.

[0126] 11A is a diagram showing an example of the configuration of the AC signal supply unit 50b. The AC signal supply unit 50b includes a power supply 90 and a limiting unit 56.

[0127] The power supply 90 generates a reference frequency f ｍｏｄ A square wave voltage V ｓｉｎ As in the present embodiment, the AC signal supply unit 50 a includes a power supply 52 that outputs a DC voltage, and a power supply 53 that converts the DC voltage signal output by the power supply 52 into a signal having a reference frequency f ｍｏｄ The chopper 54 that modulates the AC signal into a square wave signal having the above waveform may be replaced with the power supply 90. In this way, unlike the AC signal supply unit 50a, the AC signal supply unit 50b functions as a source of an AC signal that is not modulated by the chopper 54.

[0128] The limiting unit 56 limits the value of the current applied to the electrodes 150 a and 150 b. The limiting unit 56 includes resistors 560 and 562. The resistance value of the resistor 560 may be the same as that of the resistor 562, or may be set to a different value as desired.

[0129] 11B is a diagram showing an example of the configuration of the AC signal supply unit 50c. The AC signal supply unit 50c includes a power supply 92 and a limiting unit 56.

[0130] The power supply 92 is a power supply that outputs a sine wave voltage Vsin. As in this embodiment, in the AC signal supply unit 50c, the power supply 52 and chopper 54 in the AC signal supply unit 50a may be replaced with the power supply 92. In this way, unlike the AC signal supply unit 50a, the AC signal supply unit 50c functions as a source of an AC signal that is not modulated by the chopper 54, and supplies a sine wave AC signal. As in this embodiment, each biological information measurement device 10 may read the bioimpedance BioZ from the current flowing through the living organism 300 via the electrodes 150a, 150b when a sine wave AC signal is supplied.

[0131] The limiting unit 56 limits the value of the current applied to the electrodes 150a and 150b. The limiting unit 56 may have the same configuration as the AC signal supplying unit 50b.

[0132] 12 is a diagram showing an example of the configuration of the AC signal supply unit 50d. The AC signal supply unit 50d includes a current source 94 and a mixer 96.

[0133] The AC signal supply unit 50d corresponds to a configuration in which the power supply 52, which is the voltage source in the AC signal supply unit 50a, is replaced with a current source 94, and the limiting unit 56 is omitted. In this manner, each of the power supplies 52, 90, and 92, which are voltage sources including the AC signal supply units 50a to 50c, may be replaced with a current source 94.

[0134] In any of the methods of the AC signal supply units 50a to 50d described above, the AC signal supply units 50a to 50d may be connected to the electrodes 150a, 150b via capacitance such as a capacitor in order to provide insulation for the DC component between the AC signal supply units 50a to 50d and the living body 300.

[0135] Here, the AC signal supply units 50a to 50c use one of the power supplies 52, 90, or 92, which is a voltage source. In this case, the bioimpedance measurement unit 100 measures the fluctuation of the bioimpedance BioZ by measuring a signal Vs indicating the potential difference between the electrodes 150a and 150b. Furthermore, as will be described later with reference to FIG. 14, by providing a biopotential signal output unit 200 connected to the electrodes 150a and 150b, it is possible to output a biopotential signal with reduced influence of MA.

[0136] When the AC signal supply unit 50 applied to a living body uses one of the power sources 52, 90, and 92 as a voltage source to measure both the biopotential signal and the fluctuation components of bioimpedance, the biopotential signal may appear as a relatively low-frequency component regardless of the frequency of the AC signal. Therefore, the low-frequency components of noise contained in the AC signal may become measurement noise in the biopotential signal. Capacitance that reduces the DC component of the AC signal can reduce such noise. Furthermore, the resistors 560 and 562 and capacitance for limiting the current in the limiting unit 56 divide the voltage between the bioimpedance and the resistance, capacitance, and the bioimpedance, thereby preventing noise from the AC signal supply unit 50 from being superimposed on the frequency band of the biopotential signal (e.g., a frequency band of 20 Hz to 4 kHz if the biopotential signal is a myoelectric signal).

[0137] Fig. 13 is a diagram showing an example of a modified embodiment in which components other than the bioimpedance measurement unit 100a are replaced with components other than the bioimpedance measurement unit 100a in the embodiment of Fig. 2. The bioinformation measurement device 10 includes a power supply 105, a current-voltage conversion amplifier 110, and a single-ended differential conversion circuit 115.

[0138] The power supply 105 supplies a single-ended square wave voltage signal referenced to the voltage at the electrode 150 a. Therefore, the circuit connected to the electrode 150 a corresponds to an “AC signal output circuit” including the power supply 105, which corresponds to a “voltage output circuit.”

[0139] The current-voltage converting and amplifying unit 110 converts the current flowing through the living body 300 into a voltage signal via a pair of electrodes 150 a, 150 b, and amplifies the converted voltage signal. The current-voltage converting and amplifying unit 110 is connected to the electrode 150 b. The current-voltage converting and amplifying unit 110 includes an amplifier circuit 112 and a resistor 114.

[0140] The amplifier circuit 112 is, for example, an operational amplifier. The resistor 114 converts the current signal supplied from the electrode 150b into a voltage signal. The amplifier circuit 112 and the resistor 114 form a non-inverting amplifier circuit, which converts the output voltage signal into an amplified signal. Here, the circuit forming the amplifier circuit 112 and the resistor 114 is not limited to a non-inverting amplifier circuit, and an inverting amplifier circuit may also be used.

[0141] The single-ended differential conversion circuit 115 converts the single-ended voltage signal output by the current-voltage conversion amplifier 110 into a differential signal V Ｓ The single-ended differential conversion circuit 115 is a circuit that includes, for example, a differential amplifier, level-shifts the single-ended signal, and outputs a differential signal. Ｓ may be supplied to any one of the bioimpedance measuring units 100a to 100c. By using the single-ended differential conversion circuit 115, even when a current is passed from the single-ended power supply 105 to the electrode 150a and a single-ended current signal is extracted from the electrode 150b, a signal V Ｓ can be obtained.

[0142] 14 is a block diagram showing an example of the configuration of a biological information measurement device 10d. The biological information measurement device 10d includes an AC signal supply unit 50, a bioimpedance measurement unit 100, and electrodes 150, as well as a generation unit 60 and a biopotential signal output unit 200. The bioimpedance measurement unit 100 may be any one of the bioimpedance measurement units 100a, 100b, and 100c already described.

[0143] The bioimpedance measuring unit 100 derives a signal V proportional to the fluctuation of the bioimpedance BioZ from a signal based on the potential generated between the electrodes 150a and 150b. Ｂ１ Output.

[0144] The generator 60 generates the signal V Ｂ１ , a signal V indicative of motion artifacts is generated in response to ＭＡ The generating unit 60 outputs the signal V Ｂ１ and signal V ＭＡ and the signal V input from the bioimpedance measuring unit 100. Ｂ１ and based on the signal V ＭＡ to generate a signal V ＭＡ The generating section 60 may output the signal V Ｂ１ Input signal V ＭＡ The signal V input from the bioimpedance measuring unit 100 is calculated according to a predetermined function that outputs Ｂ１ Signal V ＭＡ to generate a signal V ＭＡ The generating section 60 may output the signal V Ｂ１ is multiplied by a predetermined coefficient to obtain a signal V ＭＡ to generate a signal V ＭＡ The motion artifact corresponds to a noise component included in the component obtained by compounding the action potentials from the multiple muscle fibers that make up the living body 300 in the measurement of myoelectric potential. Therefore, the generating unit 60 outputs the signal V Ｂ１ Based on this, a noise signal V ＭＡ Generate.

[0145] The biopotential signal output unit 200 reads the biopotential from the potential generated between the electrodes 150a and 150b, and outputs a signal V corresponding to the biopotential. ＥＭＧ The biopotential signal output unit 200 outputs a signal V corresponding to the measured biopotential. ＥＭＧ＋ＭＡ noise signal V corresponding to motion artifacts ＭＡ As a result, for example, when the biopotential signal to be measured is a myoelectric signal, the biopotential signal V is removed as a myoelectric signal that indicates a component in which the action potentials from each of the multiple muscle fibers 308 that make up the living body 300 are combined. ＥＭＧ The biopotential signal output section 200 includes a second amplifier section 210, an ADC 220, and a subtractor 222.

[0146] The second amplifier 210 amplifies the signal in the fifth frequency band by blocking, from the signal Vs, a frequency band lower than a fifth frequency band including a component that is a composite of action potentials from each of the multiple biological tissues that make up the living body 300, and a frequency band higher than the fifth frequency band and including the first frequency band. The second amplifier 210 includes a high-pass filter 212, an amplifier circuit 214, and a low-pass filter 216.

[0147] The biopotential signal output unit 200 outputs a signal V that indicates the potential difference occurring between the electrodes 150 a and 150 b that are in contact with the living body 300. Ｓ The high-pass filter 212 measures the signal V Ｓ , and the frequency band lower than the fifth frequency band is blocked, and the signal V Ｈ３ The cutoff frequency of the high-pass filter 212 is, for example, 20 Hz, similar to the high-pass filter 26. As a result, the high-pass filter 212 outputs the signal V Ｓ The contribution of the half-cell potential component 73 is shielded from the signal V , and the signal V is obtained by shielding the signal V from the signal V . The signal V is obtained by shielding the contribution of the half-cell potential component 73 from the signal V . The ... Ｈ３ Output.

[0148] The amplifier circuit 214 outputs the signal V Ｈ３ is amplified to produce a signal V Ａ５ The high-pass filter 212 outputs the signal V Ｓ Alternatively, the amplifier circuit 214 may be an active filter that shields and amplifies the contribution of the half-cell potential component 73 from the power supply 211, in which case the amplifier circuit 214 may be omitted.

[0149] The low pass filter 216 filters the signal V Ａ５ The low-pass filter 216 shields the bioimpedance component 70 from the signal V and also functions as an anti-aliasing filter to prevent high-frequency aliasing signals from occurring when the analog signal is converted into a digital signal. Ａ５ and blocks the high frequency band of the signal V Ｌ２ The low-pass filter 216 filters out frequency bands higher than the fifth frequency band and including the first frequency band. The low-pass filter 216 filters out the signal VＡ５ Alternatively, the filter may be an active filter that blocks and amplifies the high frequency band.

[0150] In this case, the low-pass filter 216 only needs to be able to block the first frequency band and have a cutoff frequency higher than the upper limit of the action potential component 72. In other words, the upper limit of the fifth frequency band only needs to be lower than the lower limit of the first frequency band and equal to or higher than the upper limit of the action potential component 72 of the biopotential signal to be measured, i.e., equal to or higher than the upper limit of the desired biopotential signal. Therefore, the upper limit of the fifth frequency band may be set to 4 kHz or higher, 5 kHz or higher, or 10 kHz or higher, for example, when measuring a myoelectric signal as the biopotential signal. As another example, the upper limit of the fifth frequency band may be set to 100 Hz or higher, or 200 Hz or higher, for example, when measuring an electrocardiogram signal. In this case, the cutoff frequency of the low-pass filter 216 may be set to a frequency higher than 100 Hz or 200 Hz and lower than the lower limit of the first frequency band.

[0151] The ADC 220 receives the signal V Ｌ２ is converted to a digital signal V ＥＭＧ＋ＭＡ Thus, the ADC 220 outputs a signal V corresponding to the residual component 74, which includes the combined components of the action potentials from each of the muscle fibers 308. Ｌ２ is converted to a digital signal V ＥＭＧ＋ＭＡ Output.

[0152] The subtractor 222 subtracts the signal V ＥＭＧ＋ＭＡ noise signal V indicating motion artifacts ＭＡ By subtracting the component of ＥＭＧ For example, when the biopotential signal to be measured is a myoelectric signal, the biopotential signal output unit 200 of the biological information measurement device 10d outputs a biopotential signal V ＥＭＧ can be output.

[0153] According to the configuration of the biological information measurement device 10d of this embodiment, for example, when the biopotential signal to be measured is an electromyogram, a biopotential signal V is generated to generate a surface electromyogram (Electro Myogram) in which action potentials from each of a plurality of biological tissues (e.g., muscle fibers 308) constituting the living body 300 are combined. ＥＭＧ Furthermore, the biological information measurement device 10d realizes a configuration of a low-power analog front end and an ADC 45 using a small IC, and can acquire a biopotential signal V such as a myoelectric signal with high accuracy. ＥＭＧ This allows noise caused by motion artifacts to be removed.

[0154] The high-pass filter 212 is an example of a "third high-pass filter." The amplifier circuit 214 is an example of a "third amplifier circuit." The low-pass filter 216 is an example of a "second low-pass filter." The signal V Ｅ is an example of a "biopotential signal."

[0155] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0156] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order.

[0157] 10 Biological information measuring device 12, 26, 30, 212 High-pass filter 14, 40, 112, 214 Amplification circuit 20 First amplification section 22, 96 Mixer 24, 216 Low-pass filter 28 Separator 32 Notch filter 42 Multiplexer 45, 220 ADC 50 AC signal supply section 52, 90, 92, 105 Power supply 54 Chopper 56 Limiting section 60 Generating section 70, 80 Impedance component 72 Action potential component 73 Half-cell potential component 74 Residual component 75 Shifted residual component 77 High-frequency shift component 78 Frequency band 79, 82 Fluctuation component 84 Amplified fluctuation component 94 Current source 100 Bioimpedance measuring section 110 Current-voltage conversion amplification section 114, 560, 562 Resistor 115 Single-ended differential conversion circuit 150 Electrode 200 Biopotential signal output section 222 Subtractor 282 Adder 284 Integrator 285 Low-pass filter 300 Living body 302 Epidermis layer 304 Dermis and subcutaneous layer 306 Muscle layer 308 Muscle fiber 310 Nerve

Claims

1. A biological information measuring device comprising: an AC signal supply unit that supplies an AC signal indicating a reference frequency between a pair of electrodes in contact with a living body; a first high-pass filter that blocks a frequency band lower than a first frequency band including the reference frequency from a first signal corresponding to the AC signal; and a first amplifier unit that amplifies a third signal obtained by blocking a second frequency band that is narrower than the first frequency band and includes the reference frequency from a second signal output from the first high-pass filter, and outputs the third signal as a biological information signal indicating a fluctuation component of the impedance of the living body.

2. The bioinformation measuring device of claim 1, wherein the first amplifier has an amplifier circuit that amplifies the third signal and outputs it as the bioinformation signal, and the third signal is a signal that corresponds to a component of the second signal that is outside the second frequency band of the first frequency band.

3. The biological information measuring device of claim 2, wherein the first amplifier unit comprises: a first mixer that converts the second signal into a signal of a third frequency band lower than the first frequency band by mixing the second signal with an AC signal indicating the reference frequency; a first low-pass filter that blocks a fourth frequency band that is higher than the third frequency band and includes the reference frequency from the signal output from the first mixer; and a second high-pass filter that blocks a frequency band lower than the first frequency in the third frequency band from the signal output from the first low-pass filter, and outputs the signal as the third signal.

4. The biological information measuring device of claim 2, wherein the first amplifier unit comprises: a first mixer that converts the second signal into a signal of a third frequency band lower than the first frequency band by mixing the second signal with an AC signal indicating the reference frequency; a first low-pass filter that blocks a fourth frequency band higher than the third frequency band and including the reference frequency from the signal output from the first mixer; and a separator that separates the signal output from the first low-pass filter into a signal of a frequency band component lower than the first frequency within the third frequency band and a signal of a frequency band component higher than the first frequency, and outputs the signal of the frequency band component higher than the first frequency as the third signal.

5. The biological information measuring device according to claim 2, wherein the first amplifier section has a notch filter that blocks the second frequency band from the second signal and outputs it as the third signal.

6. The biological information measuring device of claim 1, wherein the first signal includes a biological potential component which is a combination of action potentials from each of a plurality of biological tissues which constitute the living body, a fluctuation component of the impedance of the living body, and an average value component of the impedance of the living body.

7. The biological information measuring device according to claim 6, wherein the first amplifier removes an average value component of the impedance of the living body by blocking the second frequency band from the second signal.

8. The biological information measuring device of claim 1, wherein the AC signal supply unit includes: a voltage output circuit that outputs an AC voltage signal indicating the reference frequency; and a limiting unit that limits the amount of current flowing from the voltage output circuit to the living body via the pair of electrodes; and the first signal indicates a potential difference between the pair of electrodes caused by the current flowing through the living body.

9. The biological information measuring device of claim 1, wherein the AC signal supply unit has a current output circuit that outputs an AC current signal indicating the reference frequency, and the first signal indicates a potential difference between the pair of electrodes caused by a current flowing through the living body.

10. The biological information measuring device of claim 1, wherein the AC signal supply unit has a voltage output circuit that outputs an AC voltage signal indicating the reference frequency, and the biological information measuring device comprises a current-voltage conversion amplifier unit that converts the current flowing through the living body via the pair of electrodes into a voltage signal, and a single-ended differential conversion circuit that outputs a signal obtained by single-ended differential conversion of the voltage signal as the first signal.

11. A biological information measuring device as described in any one of claims 1 to 10, further comprising: a generation unit that generates a noise signal indicating a noise component contained in a component that is a composite of action potentials from each of a plurality of biological tissues that constitute the living organism based on the biological information signal; and a biological potential signal output unit that removes the noise signal component from the first signal and outputs it as a biological potential signal indicating a component that is a composite of action potentials from each of a plurality of muscle fiber biological tissues that constitute the living organism.

12. The bioinformation measuring device of claim 11, wherein the biopotential signal output unit has a second amplifier unit that blocks a frequency band lower than a fifth frequency band including a component that is a combination of action potentials from each of a plurality of biological tissues that constitute the living organism from the first signal, and a frequency band higher than the fifth frequency band and including the first frequency band, and amplifies the signal of the fifth frequency band, and the biopotential signal output unit outputs the biopotential signal by removing components of the noise signal from the signal output from the second amplifier unit.

13. A method for measuring biological information, comprising the steps of: supplying an AC signal indicating a reference frequency between a pair of electrodes in contact with a living body; blocking a frequency band lower than a first frequency band including the reference frequency from a first signal corresponding to the AC signal, and outputting a second signal; blocking a second frequency band narrower than the first frequency band and including the reference frequency from the second signal, and outputting a third signal; and amplifying the third signal, and outputting it as a biological information signal indicating a fluctuation component of the impedance of the living body.