Biological signal measurement system

Abstract

This biological signal measurement system comprises a first sensor device (1-1) that is attached to a right side part of a person under measurement and a second sensor device that is attached to a left side part of the person under measurement. Each of the first and second sensor devices includes a common mode component removal unit (1032) for removing, from a signal received by a reception electrode (1030), a component of a signal of the sensor device itself that is transmitted from a transmission electrode (1020) to the other sensor device.

Description

Biosignal Measurement System

[0001] The present invention relates to a biological signal measurement system for measuring biological signals such as electrocardiogram waveforms.

[0002] The number of heart disease patients in Japan is increasing year by year. Heart disease is one of the leading causes of death among Japanese people. Among heart diseases, diagnosing tachycardia requires a measurement period of several weeks. Early detection of heart disease requires continuous long-term electrocardiogram waveform measurement in daily life.

[0003] For this reason, progress is being made in the development of wearable devices, such as clothing and wrist-worn devices, that enable electrocardiogram waveform measurement not only in hospitals and facilities but also in patients' daily lives at home. One example of a wrist-worn wearable device is the Apple Watch (registered trademark) manufactured by Apple Inc. Wrist-worn devices are easy to put on and take off, and cause minimal discomfort, making them convenient for the wearer. However, wrist-worn devices require the wearer to touch the device with their fingers or hands when measuring electrocardiogram waveforms, which means that measurement must be performed while the wearer is stationary and is not suitable for long-term measurement.

[0004] On the other hand, the wearable device has two conductive fabric bioelectrodes and wiring sewn inside the garment. These electrodes and wiring are in contact with the wearer's skin. The wearable device also wirelessly transmits the measured electrocardiogram waveform to an external terminal using a dedicated transmitter attached to the chest.

[0005] Fig. 22 shows an outline of a conventional biosignal measurement system. In the system shown in Fig. 22, a device worn on the body of a wearer 100 constitutes a differential gain stage 10, and an external terminal constitutes a common-mode rejection stage 20. The configuration shown in Fig. 22 removes noise components applied in phase to the electrodes of the device worn on the body of the wearer 100, while amplifying biopotentials that appear in antiphase. If the size of the clothing is appropriately selected, such a wearable device allows stable measurement even when the wearer moves, and is suitable for long-term measurement.

[0006] However, conventional biosignal measurement systems require wires to connect devices, restricting the wearer's body and causing discomfort. For example, in the case of electrocardiogram measurement, the potential difference between two points on the wearer's body is measured, so the wiring between the electrodes restricts the wearer's physical movement. While research and development has been conducted on wearable electrocardiograms, such as patch-type electrocardiograms, which do not require wires, the hassle of putting on and taking off clothing when wearing them poses a problem that can easily cause wearers to feel uncomfortable.

[0007] In other words, from the viewpoint of usability, it is desirable that the device be worn on the limbs, and a device that can perform measurements for a long period of time without restricting the wearer's body movements is required. To meet these requirements, a system that eliminates inter-electrode wiring to reduce the burden on the wearer has been proposed (Non-Patent Document 1). The system disclosed in Non-Patent Document 1 eliminates inter-electrode wiring by using a human body transmission path as part of the electrocardiogram waveform measurement circuit, and by wearing two devices on the wearer's left and right limbs, it is possible to measure electrocardiogram waveforms even when the wearer is moving freely.

[0008] The configuration of the system disclosed in Non-Patent Document 1 is shown in Fig. 23. Although not shown here, devices 1000-1 and 1000-2 each have electrodes for measuring biosignals, and transmitting and receiving electrodes for transmitting modulated signals via the body of wearer 100. All of the electrodes are in contact with the body (skin) of wearer 100.

[0009] A low-pass filter (LPF) 1001-1 of device 1000-1 inputs the results of low-pass filtering of biosignals such as cardiac potentials measured by the biosignal measurement electrodes of device 1000-1 to a differential amplifier 1002-1. A modulator (MOD) 1003-1 modulates the output signal of the differential amplifier 1002-1. The modulated signal output from MOD 1003-1 is transmitted from the transmitting electrode of device 1000-1 to device 1000-2 on the opposite side via the body of the wearer 100. Similarly, a modulated signal output from MOD 1003-2 of device 1000-2 is transmitted from the transmitting electrode of device 1000-2 to device 1000-1 via the body of the wearer 100.

[0010] The modulated signal transmitted from device 1000-2 through the body of wearer 100 is received by the receiving electrode of device 1000-1. A demodulation unit (DEMOD) 1004-1 of device 1000-1 demodulates the modulated signal received by the receiving electrode to extract a biosignal. A differential amplifier unit 1002-1 is used to weaken the in-phase signal and strengthen the out-of-phase signal. The out-of-phase signal indicates that the biosignal measured by device 1000-1 and the biosignal measured by device 1000-2 are in an out-of-phase relationship. Therefore, the biosignal measured by device 1000-2 needs to be fed back and input to the inverting input terminal of the differential amplifier unit 1002-1 of device 1000-1. Similarly, the biosignal measured by device 1000-1 needs to be fed back and input to the inverting input terminal of the differential amplifier unit 1002-2 of device 1000-2.

[0011] That is, in the configuration shown in FIG. 23 , the mutual feedback circuit between the differential amplifiers 1002-1 and 1002-2 is realized by a human body path as indicated by 1007. When the mutual feedback functions normally, the output from the differential amplifiers 1002-1 and 1002-2 is a signal in which the opposite-phase signal is strengthened. The AD converters 1005-1 and 1005-2 convert the output signals from the differential amplifiers 1002-1 and 1002-2 into digital data. The wireless transmitters 1006-1 and 1006-2 wirelessly transmit the digital data output from the AD converters 1005-1 and 1005-2 to the external terminal 1010. The external terminal 1010 calculates, for example, the difference between the biosignal transmitted from the device 1000-1 and the biosignal transmitted from the device 1000-2 as an electrocardiogram waveform.

[0012] In the case of a system using human body transmission as described in FIG. 23, devices 1000-1 and 1000-2 and the body of wearer 100 correspond to differential gain stage 10 in FIG.

[0013] However, human body transmission is said to be good in the frequency range below 100 MHz, and some literature suggests up to about 40 MHz. Therefore, since multiple signal transmissions are performed in a narrow frequency range, the impact on mutual feedback becomes an issue. Specifically, there is a possibility that a signal transmitted by the device itself may be received by the receiving electrode of the device itself via the wearer's body, resulting in a problem that a weak signal from another device that should be received becomes buried in the signal transmitted by the device itself and cannot be demodulated.

[0014] In other words, each of the devices 1000-1 and 1000-2 in Figure 23 must receive a weak signal from the other device, while also removing the strong signal it has transmitted. Because the frequencies of the modulated signals transmitted by the devices 1000-1 and 1000-2 are close, a narrow-band, steep band-pass filter must be used to remove the signal. However, to achieve a narrow-band, steep band-pass filter, it is necessary to use a large number of inductors with high Q values, which increases the mounting area and costs.

[0015] Kento Watanabe et al., "Proposal of a Wireless Electrocardiogram Measurement Circuit Using the Human Body as Inter-element Wiring," Proceedings of the Institute of Electronics, Information and Communication Engineers General Conference, vol. 1, B-19-1, p. 467, 2023

[0016] The present invention has been made to solve the above-mentioned problems, and aims to provide a biosignal measurement system that can easily demodulate weak signals from a paired device and perform good biosignal measurement.

[0017] The biosignal measurement system of the present invention comprises a first sensor device configured to be worn on one of the right and left sides of a subject, and a second sensor device configured to be worn on the other of the right and left sides, each of the first and second sensor devices including a first electrode provided to be in contact with the skin of the subject, a first amplifier configured to amplify a biopotential detected by the first electrode, a modulator configured to modulate a carrier wave in accordance with the biopotential amplified by the first amplifier, and a second amplifier configured to amplify a signal output from the modulator, and a second amplifier provided to be in contact with the skin of the subject and amplifying a signal output by the second amplifier. a second electrode configured to transmit and receive a signal amplified by the first amplifier to and from the other sensor device via the body of the subject; a third amplifier configured to amplify the signal from the other sensor device received by the second electrode; a demodulator configured to demodulate the signal amplified by the third amplifier to extract information about the biopotential; a reference potential generator configured to generate a reference potential for the first amplifier based on the biopotential amplified by the first amplifier and the biopotential output from the demodulator; and a common mode component remover configured to remove components of the signal of the subject's own device to be transmitted to the other sensor device from the signal received by the second electrode.

[0018] According to the present invention, by connecting the first sensor device and the second sensor device via wireless communication, it is possible to eliminate the wiring connecting the first sensor device and the second sensor device. This reduces the discomfort of the measurement subject caused by the wiring and eliminates the need for physical constraints on the measurement subject. Furthermore, according to the present invention, by providing a common-mode component removal unit in each of the first sensor device and the second sensor device, it is possible to remove the signal transmitted from the first sensor device from the signal received by the second electrode. This allows the present invention to easily demodulate weak signals from the paired device, thereby achieving stable mutual feedback and enabling excellent biosignal measurement. According to the present invention, it is not necessary to use a narrow-band, steep bandpass filter to remove noise components. This prevents increases in circuit area and cost.

[0019] FIG. 1 is a diagram illustrating the principle of the present invention. FIGS. 2A and 2B are diagrams illustrating the configuration of a biosignal measurement system according to a first embodiment of the present invention. FIG. 3 is a block diagram illustrating the configuration of a sensor device according to the first embodiment of the present invention. FIG. 4 is a block diagram illustrating the configuration of an external terminal according to the first embodiment of the present invention. FIG. 5 is a flowchart illustrating the operation of a sensor device according to the first embodiment of the present invention. FIG. 6 is a flowchart illustrating the operation of a sensor device according to the first embodiment of the present invention. FIG. 7 is a circuit diagram illustrating the configuration of an amplifier unit of a sensor device according to the first embodiment of the present invention. FIG. 8 is a flowchart illustrating the operation of an external terminal according to the first embodiment of the present invention. FIG. 9 is a diagram illustrating an overview of attenuation adjustment in a second embodiment of the present invention. FIG. 10 is a block diagram illustrating the configuration of a sensor device according to a second embodiment of the present invention. FIG. 11 is a block diagram illustrating the configuration of an attenuation unit according to the second embodiment of the present invention. FIG. 12 is a block diagram illustrating the configuration of a CM component removal unit according to the first and second embodiments of the present invention. FIG. 13 is a circuit diagram illustrating the configuration of an attenuation unit according to a third embodiment of the present invention. FIG. 14 is a circuit diagram illustrating another configuration of an attenuation unit according to the third embodiment of the present invention. FIG. 15 is a circuit diagram illustrating the configuration of an amplitude detection unit according to the third embodiment of the present invention. FIG. 16 is a circuit diagram showing another configuration of an amplitude detection unit according to a third embodiment of the present invention. FIG. 17 is a block diagram showing the configuration of an amplitude detection unit according to a fourth embodiment of the present invention. FIG. 18 is a block diagram showing the configuration of a sensor device according to a fifth embodiment of the present invention. FIG. 19 is a flowchart explaining the attenuation adjustment operation according to the fifth embodiment of the present invention. FIG. 20 is a diagram explaining the principle of a sixth embodiment of the present invention. FIG. 21 is a block diagram showing the configuration of a sensor device according to the sixth embodiment of the present invention. FIG. 22 is a diagram showing an outline of a conventional biosignal measurement system. FIG. 23 is a diagram showing another configuration of a conventional biosignal measurement system.

[0020] [Principle of the Invention] In a system using intrabody transmission as described in Figure 23, the noise source is the transmission signal of the device itself. Therefore, in the present invention, the transmission signal, which is a crosstalk component, is known, and the transmission signal component that has reached the receiving electrode and the signal on the transmitting electrode side are treated as in-phase signals, thereby removing the common mode (CM) component. This removes crosstalk, realizes stable mutual feedback, and performs good biosignal measurement while reducing the burden on the subject. According to the present invention, it is also possible to track changes in frequency components due to FM (Frequency Modulation), which is difficult to track with a basic filter circuit.

[0021] Fig. 1 is a diagram illustrating the principle of the present invention. In Fig. 1, 1020 is a transmitting electrode, 1021 is an amplifier that amplifies a modulated signal from a modulator (not shown) and outputs it to the transmitting electrode 1020, 1030 is a receiving electrode, and 1031 is an amplifier that amplifies the modulated signal received by the receiving electrode 1030. Note that Fig. 1 illustrates the case of a sensor device worn on the right side of a subject 100.

[0022] FIG. 1 shows a signal Tx transmitted from the device itself. Ｒ is transmitted to the receiving electrode 1030 side through the body of the subject 100, and the signal Tx transmitted from the other sensor device that should have been received is Ｌ When the sensor devices are worn on the right and left hands of the subject, the signal Rx obtained from the receiving electrode 1030 of the sensor device worn on the right hand is Ｒ is expressed as in equation (1). Ｒ = αTx Ｒ +βTx Ｌ ...(1)

[0023] The coefficients α and β are values ​​less than or equal to 1, which means that the signal is lost as it propagates through the human body. In the case of a sensor device worn on the right hand, the transmission signal Tx Ｒ is a signal transmitted from the own device and is known.

[0024] The attenuation unit 1033 in FIG. ＲThe CM component removal unit 1032 attenuates the transmission signal Tx supplied from the attenuation unit 1033 and supplies it to the CM component removal unit 1032. Ｒ The component of the signal Rx Ｒ This removes the signal Tx from other devices that should be received. Ｌ can be obtained.

[0025] [First embodiment] An embodiment of the present invention will be described below with reference to the drawings. Figures 2A and 2B are diagrams showing the configuration of a biosignal measurement system according to this embodiment. The biosignal measurement system is composed of a sensor device 1-1 worn on the right side of a subject 100, a sensor device 1-2 worn on the left side of the subject 100, and an external terminal 2.

[0026] When measuring cardiac potentials as biosignals, sensor devices 1-1 and 1-2 must be positioned so as to sandwich heart 110 of subject 100, as shown in FIGS. 2A and 2B. In the example of FIG. 2A, sensor device 1-1 is worn on the right upper limb of subject 100, and sensor device 1-2 is worn on the left upper limb. The upper limbs include parts such as the shoulder, upper arm, forearm, wrist, palm, and fingers. In the example of FIG. 2B, sensor device 1-1 is worn on the right upper limb of subject 100, and sensor device 1-2 is worn on the left lower limb. The lower limbs include parts such as the thigh, lower leg, ankle, dorsum of the foot, sole, and toes. S1 and S2 in FIGS. 2A and 2B represent biosignal data wirelessly transmitted from sensor devices 1-1 and 1-2 to external terminal 2.

[0027] 3 is a block diagram showing the configuration of sensor device 1-1. Sensor device 1-1 includes a bioelectric potential detection unit 101, a modulated signal transmission unit 102, a modulated signal reception unit 103, a wireless transmission unit 104, a CPU (Central Processing Unit) 106, a memory 107, and a buffer 108. CPU 106 executes the following processes in accordance with a program stored in memory 107.

[0028] The bioelectric potential detection unit 101 is composed of a bioelectrode 1010 that comes into contact with the skin on the right side of the subject 100, a frequency filter 1011, an amplifier 1012, an AD converter (ADC) 1013, and a reference potential generator 1014.

[0029] The modulated signal transmitting unit 102 is composed of a transmitting electrode 1020 that comes into contact with the skin on the right side of the subject 100, an amplifier 1021, and a modulator 1022. The modulated signal receiving unit 103 is composed of a receiving electrode 1030 that comes into contact with the skin on the right side of the subject 100, an amplifier 1031, a commercial component removing unit 1032, an attenuator 1033, and a demodulator 1034.

[0030] In the case of sensor device 1-2, the bioelectrode 1010, the transmitting electrode 1020, and the receiving electrode 1030 come into contact with the skin on the left side of the subject 100. Other configurations of sensor device 1-2 are the same as those of sensor device 1-1, so sensor device 1-2 will also be described using the reference numerals in FIG.

[0031] Electrodes of various materials and configurations can be used for the bioelectrode 1010, the transmitting electrode 1020, and the receiving electrode 1030. Any electrode can be used, including Ag / AgCl electrodes used in medical applications, conductive cloth electrodes, and metal electrodes.

[0032] 4 is a block diagram showing the configuration of the external terminal 2. The external terminal 2 includes a wireless receiving unit 200, a data storage unit 202, a data processing unit 203, a data analysis unit 204, a monitor unit 205, a CPU 206, a memory 207, and a buffer 208. The CPU 206 executes the following processes in accordance with a program stored in the memory 207.

[0033] In the configuration of FIG. 4, the data processing unit 203 and the data analysis unit 204 are shown as separate components from the CPU 206, but at least a part of the data processing unit 203 and the data analysis unit 204 may be realized by the CPU 206.

[0034] Fig. 5 is a flowchart explaining the operation of sensor device 1-1, and Fig. 6 is a flowchart explaining the operation of sensor device 1-2. Note that the order of processing shown in Fig. 5 and Fig. 6 is an example given for ease of understanding, and the order does not have to be the same as Fig. 5 and Fig. 6.

[0035] The frequency filters 1011 of the sensor devices 1-1 and 1-2 pass only signals in the frequency band of the biopotential among the signals detected by the bioelectrodes 1010 of the sensor devices 1-1 and 1-2 (step S100 in FIG. 5, step S200 in FIG. 6).

[0036] The amplifiers 1012 of the sensor devices 1-1 and 1-2 amplify the signals (bioelectric potentials) output from the frequency filters 1011 of the sensor devices 1-1 and 1-2 (steps S101 and S201).

[0037] The ADCs 1013 of the sensor devices 1-1 and 1-2 convert the bioelectric potentials amplified by the amplifiers 1012 of the sensor devices 1-1 and 1-2 into digital data (steps S102 and S202).

[0038] The wireless transmitting units 104 of the sensor devices 1-1 and 1-2 wirelessly transmit the biopotential data output from the ADCs 1013 of the sensor devices 1-1 and 1-2 to the external terminal 2 (steps S103 and S203). The operation of the external terminal 2 will be described later.

[0039] On the other hand, the modulators 1022 of the sensor devices 1-1 and 1-2 modulate the carrier waves in accordance with the bioelectric potentials amplified by the amplifiers 1012 of the sensor devices 1-1 and 1-2, respectively, and output the modulated signals to the amplifiers 1021 (steps S104 and S204). The modulators 1022 generate carrier waves using their internal carrier frequency generators.

[0040] The amplifiers 1021 of the sensor devices 1-1 and 1-2 amplify the modulated signals from the modulators 1022 of the sensor devices 1-1 and 1-2, respectively, and output the amplified signals to the transmitting electrodes 1020 (steps S105 and S205). As a result, the modulated signals amplified by the amplifiers 1021 of the sensor device 1-1 (transmission signals Tx Ｒ) is transmitted from the transmitting electrode 1020 of the sensor device 1-1 to the sensor device 1-2 through the body of the subject 100 (step S106). Similarly, the modulated signal (transmission signal Tx Ｌ ) is transmitted from the transmitting electrode 1020 of the sensor device 1-2 to the sensor device 1-1 through the body of the subject 100 (step S206).

[0041] The CM component removal unit 1032 of the sensor device 1-1 removes the transmission signal Tx supplied from the attenuation unit 1033 of its own device. Ｒ The CM component removal unit 1032 of the sensor device 1-2 removes the CM component from the modulated signal Tx received by the receiving electrode 1030 of the sensor device 1-2 (step S107). Ｌ The component of is removed from the modulated signal received by the receiving electrode 1030 of the device itself (step S207).

[0042] The amplifiers 1031 of the sensor devices 1-1 and 1-2 amplify the modulated signals output from the commercial component removers 1032 of the sensor devices 1-1 and 1-2 (steps S108 and S208). The demodulators 1034 of the sensor devices 1-1 and 1-2 demodulate the modulated signals amplified by the amplifiers 1031 of the sensor devices 1-1 and 1-2 to extract biopotential information (steps S109 and S209). The demodulators 1034 generate local signals for demodulation using an internal local frequency oscillator.

[0043] The reference potential generating unit 1014 of each sensor device 1-1, 1-2 generates a reference potential for the amplifier unit 1012 of its own device based on the biopotential amplified by the amplifier unit 1012 of its own device and the biopotential demodulated by the demodulator unit 1034 of its own device (steps S110, S210).

[0044] The bioelectric potential detected by the bioelectrode 1010 is a very weak signal, and therefore requires signal amplification by the amplifier 1012. In order to improve the measurement accuracy of the bioelectric potential, it is important that the reference potential of the amplifier 1012 on the sensor device 1-1 side and the reference potential of the amplifier 1012 on the sensor device 1-2 side are the same. In this embodiment, since the sensor devices 1-1 and 1-2 are not connected by wiring, the reference potentials of the sensor devices 1-1 and 1-2 may not match, which may result in a deterioration in the measurement accuracy of the bioelectric potential.

[0045] Therefore, in this embodiment, information on the biological potential is transmitted and received between the sensor devices 1-1 and 1-2, so that the reference potential Vref in the amplifiers 1012 of the sensor devices 1-1 and 1-2 is made common.

[0046] 7 is a circuit diagram showing an example of the configuration of the amplifier unit 1012. The amplifier unit 1012 is composed of an operational amplifier A1, whose non-inverting input terminal is connected to the output terminal of the frequency filter 1011, a resistor R1, whose one end is connected to the inverting input terminal of the operational amplifier A1, and a resistor R2, whose one end is connected to the inverting input terminal of the operational amplifier A1 and whose other end is connected to the output terminal of the operational amplifier A1. A reference potential Vref is supplied to the other end of the resistor R1.

[0047] The reference potential generating section 1014 of each of the sensor devices 1-1 and 1-2 may generate the reference potential Vref by, for example, calculating the arithmetic mean of the biopotential amplified by the amplifier section 1012 and the biopotential demodulated by the demodulator section 1034.

[0048] The sensor device 1-1 repeatedly executes the processes of steps S100 to S110 until the measurement is terminated, for example, in response to an instruction from the subject (YES in step S111). Similarly, the sensor device 1-2 repeatedly executes the processes of steps S200 to S211 until the measurement is terminated (YES in step S211).

[0049] 8 is a flowchart illustrating the operation of the external terminal 2. The wireless receiving unit 200 of the external terminal 2 receives biopotential data from the sensor devices 1-1 and 1-2 (step S300 in FIG. 8). The data received by the wireless receiving unit 200 is stored in the data storage unit 202.

[0050] If the data received by the wireless receiving unit 200 is biopotential data (YES in step S301), the CPU 206 passes the data to the data processing unit 203. The data processing unit 203 processes the biopotential data received from the sensor device 1-1 and the biopotential data received from the sensor device 1-2 (step S302). Specifically, the data processing unit 203 calculates, for example, the difference between the biopotential received from the sensor device 1-1 and the biopotential received from the sensor device 1-2 as an electrocardiogram waveform. The calculated electrocardiogram waveform is stored in the data storage unit 202.

[0051] The data analysis unit 204 analyzes the data calculated by the data processing unit 203 (step S303). For example, the data analysis unit 204 analyzes the electrocardiogram waveform and calculates the heartbeat interval as a feature amount, or calculates the heart rate as a feature amount.

[0052] The monitor unit 205 displays the data calculated by the data processing unit 203 and the data analysis unit 204 (step S304). The monitor unit 205 may display the electrocardiogram waveform calculated by the data processing unit 203, may display the feature values ​​calculated by the data analysis unit 204, or may display both the electrocardiogram waveform and the feature values. The external terminal 2 repeatedly executes the processes of steps S300 to S304 until, for example, measurement is terminated in response to an instruction from the subject (YES in step S305).

[0053] As described above, in this embodiment, the sensor devices 1-1 and 1-2 are connected by wireless communication, thereby eliminating the need for wires to connect the sensor devices 1-1 and 1-2. This reduces the discomfort felt by the subject due to the wires and eliminates the need to restrict the subject's body.

[0054] Furthermore, in this embodiment, by providing each of the sensor devices 1-1 and 1-2 with a CM component removal unit 1032 and an attenuation unit 1033, it is possible to remove noise components (CM components) from the signal transmitted from the sensor device itself at the receiving electrode side of the sensor device itself. This allows the sensor device to receive weak signals from its paired device, realizing stable mutual feedback and enabling good biosignal measurement. This embodiment eliminates the need to use a narrow, steep bandpass filter to remove noise components. This prevents increases in circuit area and cost.

[0055] Furthermore, in this embodiment, the transmission signal of the device itself is used to remove crosstalk components, so the restrictions on the magnitude of the transmission signal can be relaxed. In other words, there is a trade-off relationship in which the power of the transmission signal needs to be increased to transmit signals, but the power of the transmission signal needs to be reduced to prevent interference. In this embodiment, the power of the transmission signal can be increased within a range that does not affect the body of the measurement subject, which eliminates the above trade-off problem and has the effect of making system design easier.

[0056] Second Embodiment In the first embodiment, the amount of attenuation of the transmission signal Tx by the attenuation unit 1033 is set to a predetermined fixed value, but there is a possibility that a residual error in phase with the transmission signal Tx may appear in the output of the CM component removal unit 1032. Therefore, it is desirable to be able to appropriately adjust the amount of attenuation.

[0057] 9 is a diagram for explaining an outline of attenuation adjustment in this embodiment. In this embodiment, the overall configuration of the biological signal measurement system is the same as in the first embodiment, so the explanation will use the symbols in FIGS. 2A and 2B.

[0058] The attenuation amount of the transmission signal Tx by the attenuation unit 1033a in this embodiment is expressed by an attenuation coefficient k. The attenuation coefficient k is a real number equal to or less than 1. For example, the attenuation unit 1033a of the sensor device 1-1 attenuates the transmission signal Tx of the sensor device itself by Ｒ kTx Ｒ The signal is attenuated to the level of kTx and output. Ｒ The level of αTx in equation (1)Ｒ The damping coefficient k can be adjusted to a level equivalent to that of the

[0059] The CM component removal unit 1032 of the sensor device 1-1 removes the signal Rx obtained from the receiving electrode 1030 of the sensor device 1-1. Ｒ from the output kTx of the attenuation unit 1033a Ｒ By subtracting the noise component (CM component) αTx Ｒ can be removed.

[0060] The attenuation unit 1033a attenuates the transmission signal Tx appearing at the output of the CM component removal unit 1032. Ｒ The attenuation coefficient k is adjusted according to the level of the residual error e in phase with the transmission signal Tx. Ｒ A residual e having the same phase as the residual e appears in the output of the commercial component remover 1032. In this case, the attenuator 1033a increases the attenuation coefficient k (decreases the amount of attenuation).

[0061] Conversely, when the attenuation coefficient k is large, the transmission signal Tx Ｒ A residual error e of opposite phase to the CM component appears in the output of the CM component remover 1032. In this case, the attenuator 1033a reduces the attenuation coefficient k (increases the amount of attenuation). In this way, the noise component can be appropriately removed, and the signal Tx from the sensor device 1-2 that should be received is Ｌ 9 is applied to the sensor device 1-1 as shown in Fig. 10. The sensor device 1-2 has the same configuration as the sensor device 1-1.

[0062] 11 is a block diagram showing an example of the configuration of the attenuation unit 1033a of this embodiment. The attenuation unit 1033a is composed of an attenuator 300, which is made up of a voltage-controlled variable resistor and the like, and a control unit 301. The control unit 301 can adjust the attenuation amount (attenuation coefficient k) of the attenuator 300 by changing the control signal given to the attenuator 300. The attenuator 300 can be a T-type attenuator or a π-type attenuator, depending on the combination of variable resistors, and either can be used.

[0063] To adjust the amount of attenuation of the attenuator 300, the amplitude detection unit 1035 outputs a signal proportional to the amplitude of the component of the transmission signal Tx of the device itself, which is included in the residual e appearing in the output of the CM component removal unit 1032 of the device itself. The control unit 301 changes the control signal to be provided to the attenuator 300 so that the amplitude of the component detected by the amplitude detection unit 1035 becomes zero.

[0064] The attenuation units 1033a of the sensor devices 1-1 and 1-2 may be configured to constantly adjust the amount of attenuation as described above during operation of the sensor devices 1-1 and 1-2 described with reference to FIGS.

[0065] FIG. 12 is a block diagram showing an example of the configuration of the CM component remover 1032 in the first embodiment and this embodiment. The example in FIG. 12 shows an example in which a transformer is used as the CM component remover 1032. A transformer is typically a circuit element that provides insulation between input and output signals and performs voltage transformation. A transformer generates an induced electromotive force by completely receiving, in its secondary coil, a magnetic field generated in response to a current flowing through its primary coil, and transmits a signal in an electrically isolated state. In the present invention, noise components are removed by taking advantage of this characteristic of signal transmission by current.

[0066] 12, a receiving electrode 1030 is connected to one end of the primary coil of the transformer, and the output terminal of an attenuator 1033 or 1033a is connected to the other end of the primary coil, and an attenuated transmission signal Tx is input. An input terminal of an amplifier 1031 is connected to one end of the secondary coil of the transformer, and the other end of the secondary coil is connected to ground.

[0067] For example, in the case of the sensor device 1-1, the signal Rx obtained from the receiving electrode 1030 Ｒ αTx included in Ｒ and the kTx output from the attenuation unit 1033 or 1033a Ｒ As a result, the voltage applied to the transformer is equal to the received signal βTx Ｌ The current flowing through the primary coil is also the received signal βTx Ｌ Therefore, the secondary coil receives the received signal βTx ＬIn this way, the noise component can be removed.

[0068] Because transformers do not allow DC components to pass through, the attenuators of the attenuation units 1033 and 1033a may be capacitively coupled to the transformers for isolation. Since both the transmit signal Tx and the receive signal Rx are AC signals, they can be isolated without any problems. By providing such capacitive isolation, not only can crosstalk be eliminated, but also an important safety measure, namely, protecting living organisms, can be achieved at the same time. Medical devices are subject to strict safety standards set by regulations. Circuit isolation is extremely effective for ensuring the safety of living organisms, and this embodiment is particularly suitable for measuring biological signals. Similar effects can be achieved by using a transformer for additional isolation, as with capacitive isolation.

[0069] As another configuration of the commercial component remover 1032, a differential amplifier circuit may be used. In this case, the receiving electrode 1030 is connected to the non-inverting input terminal of the differential amplifier circuit, and the output terminal of the attenuator 1033 or 1033a is connected to the inverting input terminal of the differential amplifier circuit. With this configuration, it is possible to perform signal amplification while removing the commercial component, and therefore the amplifier 1031 between the commercial component remover 1032 and the modulator 1034 is not necessary.

[0070] Therefore, if a differential amplifier circuit is used as the configuration of the commercial component remover 1032, the circuit area of ​​each of the sensor devices 1-1 and 1-2 can be reduced. The impedance on the receiving side can easily become as high as 100 kΩ depending on the contact conditions with the body of the person being measured. For this reason, a junction field effect transistor (JFET), which can easily achieve a high input impedance, is suitable as the transistor to be used in the differential amplifier circuit.

[0071] In the configuration of FIG. 10, the modulated signal transmitting unit 102 and the modulated signal receiving unit 103 are shown as separate components from the CPU 106, but at least a part of the control unit 301 in the attenuation unit 1033a may be realized by the CPU 106, for example.

[0072] Next, a third embodiment of the present invention will be described. This embodiment is intended to improve the output of the residual e, and describes another example of the attenuation unit 1033a described in the second embodiment and a specific example of the amplitude detection unit 1035.

[0073] The residual error e appearing in the output of the commercial component remover 1032 contains frequency components, and its amplitude changes depending on the phase. For this reason, the attenuator 1033a is required to perform high-speed control to adjust the attenuation amount. This embodiment proposes a means for alleviating this high-speed requirement.

[0074] The signals transmitted by the sensor devices 1-1 and 1-2 are periodic signals such as sine waves. Therefore, the residual e is also a periodic signal. The amplitude detection unit 1035 suppresses periodic fluctuations in the output of the noise cancellation unit 1032 and extracts only the amplitude component. This allows the noise component A ｅ The output signal A of the amplitude detector 1035 can be obtained. ｅ to the reverse phase signal generating unit 1033a, high speed is not required for adjusting the attenuation amount, and a simple, low-cost element can be used as the variable resistance element that constitutes the attenuator 300.

[0075] An example of a variable resistance element in this case is a PIN diode. The resistance value of a PIN diode changes depending on the DC voltage applied to the signal A. ｅ can be considered to be approximately a DC voltage. ｅ If the input is input to a PIN diode, the PIN diode will output signal A ｅ The PIN diode is a variable resistance element whose resistance value changes depending on the input voltage. The transmission signal Tx of the device itself is input to the PIN diode, and the frequency of the transmission signal Tx is sufficiently higher than DC. Therefore, it is possible to attenuate the transmission signal Tx without affecting the resistance value of the PIN diode.

[0076] 13 shows the configuration of the attenuation unit 1033a when a PIN diode is used. The attenuator 300 of the attenuation unit 1033a is composed of a PIN diode D1 and capacitances C1 and C2. The output signal A of the amplitude detection unit 1035 ｅis applied to the anode of the PIN diode D1. The transmission signal Tx amplified by the amplifier 1021 of the device itself is input to the anode of the PIN diode D1 via the capacitance C1. As can be seen from Fig. 13, this configuration does not require the control unit 301 shown in Fig. 11.

[0077] Signal A ｅ When the level of signal A increases, the resistance value of PIN diode D1 decreases, and therefore the attenuation amount of attenuation unit 1033a decreases. ｅ When the level of the signal decreases, the resistance value of the PIN diode D1 increases, and therefore the attenuation amount of the attenuation section 1033a increases.

[0078] It is also possible to configure a voltage-controlled variable resistor using a JFET. The non-saturation region of a JFET changes depending on the drain-source voltage. The inverse of the slope of the drain current relative to the change in drain-source voltage corresponds to the drain-source resistance. This resistance changes depending on the gate-source voltage of the JFET. In other words, the resistance can be controlled by the gate-source voltage.

[0079] The configuration of the negative phase signal generating unit 1033a when a JFET is used is shown in Fig. 14. The attenuator 300 of the negative phase signal generating unit 1033a is composed of a transistor Q1, a resistor R3, and capacitors C3 and C4.

[0080] A diode detection circuit, a peak hold circuit, or the like can be used as the amplitude detection unit 1035. Fig. 15 shows an example of the configuration of the amplitude detection unit 1035. The amplitude detection unit 1035 is configured with a diode D2 having an anode (input terminal of the amplitude detection unit 1035) to which the output signal In of the commercial component removal unit 1032 is input and a cathode (output terminal of the amplitude detection unit 1035) connected to the attenuation unit 1033a, a resistor R4 having one end connected to the cathode of the diode D2 and the other end connected to ground, and a capacitor C5 having one end connected to the cathode of the diode D2 and the other end connected to ground.

[0081] The diode detector circuit shown in Fig. 15 is a circuit that is normally used when demodulating an AM (Amplitude Modulation) modulated signal, and it is necessary to properly design the time constant τ = CR in order to follow the modulation degree. On the other hand, the application of the diode detector circuit in this embodiment is not demodulation, but the application of the signal A ｅ Therefore, by increasing the time constant τ, a stable signal A ｅ 15 has the advantage that it has a simple structure and can be realized in a small area and at low cost. In the configuration example of FIG. 15, the resistor R4 may be removed (R→∞).

[0082] On the other hand, a peak hold circuit is a circuit that continuously holds the maximum value of the input signal. As is well known, a peak hold circuit uses an operational amplifier in addition to a diode detector. A peak hold circuit can hold the peak for a longer period of time with higher accuracy than a diode detector.

[0083] The configuration of amplitude detection unit 1035 using a peak hold circuit is shown in Fig. 16. The amplitude detection unit 1035 shown in Fig. 16 is composed of a diode D2, a resistor R4, capacitors C5 and C6, switches SW1 and SW2, an operational amplifier A2, and a clock generation unit 302. The clock generation unit 302 outputs a clock signal that alternately turns on switches SW1 and SW2. Note that the configuration of amplitude detection unit 1035 is not limited to a diode detection circuit or a peak hold circuit, and various circuits that can obtain the amplitude component of a periodic signal can be applied.

[0084] [Fourth Example] Next, a fourth example of the present invention will be described. In this example, the output signal A of the amplitude detector 1035 is ｅ In addition, the signal Tx from the other device that should be received Ｌ According to the third embodiment, it is possible to remove most of the noise components appearing in the output of the CM component removal unit 1032, but the output signal A of the amplitude detection unit 1035 is also included. ｅ Tx to ＬAs a result, a slight noise component remains in the output of the CM component removal unit 1032. When the frequencies of the signal transmitted from the transmitting electrode 1020 of the sensor device 1-1 and the signal transmitted from the transmitting electrode 1020 of the sensor device 1-2 are close to each other, it is difficult to remove the noise component remaining in the output of the CM component removal unit 1032 by using a filter.

[0085] Therefore, by using an amplitude detection unit 1035 configured as shown in FIG. 17, the reference signal Ref=Tx Ｒ The amplitude detector 1035 of this embodiment includes a multiplier 303 that multiplies the output signal In of the commercial component remover 1032 by a reference signal Ref, and a signal A that is obtained by low-pass filtering the output signal of the multiplier 303. ｅ and a low-pass filter 304 that outputs the signal as

[0086] In the case of the sensor device 1-1, the reference signal Ref is a transmission signal Tx output from the modulation unit 1022 or the amplification unit 1021 of the sensor device 1-1. Ｒ In the case of the sensor device 1-2, the reference signal Ref is the transmission signal Tx output from the modulation unit 1022 or the amplification unit 1021 of the sensor device 1-2. Ｌ The transmission signal Tx of the sensor device 1-1 Ｒ sinω Ｒ t, and the transmission signal Tx of the sensor device 1-2 Ｌ sinω Ｌ Let t be ω. Ｒ , ω Ｌ is the angular frequency and t is the time.

[0087] In the sensor device 1-1, the output signal In of the commercial component removal unit 1032 is multiplied by the reference signal Ref by the multiplication unit 303, and the result is expressed by equation (2).

[0088]

[0089] The output of the multiplier 303 shown in equation (2) is low-pass filtered by the low-pass filter 304, so that components other than the first term of equation (2) are removed. ＲSignal A indicating the magnitude of coefficient α of ｅ Therefore, the output signal A of the amplitude detector 1035 shown in FIG. ｅ is applied to the attenuation section 1033a, the signal Rx obtained from the receiving electrode 1030 of the sensor device 1-1 is Ｒ From the transmission signal Tx Ｒ can be removed with a very high removal ratio.

[0090] The attenuation amount adjustment by the attenuation unit 1033a is performed by adjusting the output signal A of the amplitude detection unit 1035 as described above. ｅ However, simply adjusting the attenuation amount so that the signal A ｅ If it follows Tx Ｒ In the step after the removal, the output signal of the amplitude detection unit 1035 is A ｅ = 0, the CM component removal unit 1032 does not perform the canceling operation, and the signal Rx Ｒ Tx to Ｒ In other words, the signal Rx Ｒ Tx included in Ｒ The decrease and increase of the component will be repeated alternately.

[0091] Therefore, the control unit 301 shown in FIG. 11 detects the output signal A of the amplitude detection unit 1035. ｅ is compared with a predetermined threshold value TH, and the signal A ｅ exceeds the threshold TH, the signal A ｅ The control signal to be given to the attenuator 300 is changed so that the signal A is equal to or less than the threshold value TH. ｅ When the signal A becomes equal to or smaller than the threshold value TH, the change of the control signal given to the attenuator 300 is stopped. ｅ The control signal at the time when the signal A becomes equal to or smaller than the threshold value TH is maintained. ｅ When Tx becomes equal to or less than the threshold value TH, the attenuation coefficient k of the attenuation unit 1033a is fixed. Ｒ The component of the signal will no longer alternate between decreasing and increasing.

[0092] Normally, when high-speed control is performed on a high-speed signal, the amount of update of the attenuation coefficient k must also be large. However, in the present invention, the frequency of the transmission signal Tx exceeds 1 MHz, while the band of the biological signal is about 10 kHz, and the frequencies of these signals are significantly different, so low-speed control can be performed. Specifically, the output signal A of the amplitude detection unit 1035 ｅ If the subject is in a state of near rest for 1 ms or more, the update amount may be set to a value that can converge in the order of about 1 s. This makes it possible to suppress unstable operation due to excessive tracking performance of the attenuation unit 1033a, and the signal Rx Ｒ Tx included in Ｒ The components can be efficiently removed.

[0093] Furthermore, since the attenuation coefficient k in the attenuation unit 1033a can be controlled at a low speed, a digital circuit can be used as the control unit 301. By using a digital circuit for the control unit 301, it is possible to simplify the circuit and reduce power consumption, which are extremely important in wearable devices with size restrictions. For example, the signal A acquired as a digital value ｅ Based on this, a control signal for controlling the attenuation coefficient k is generated by a low-computational-load gradient descent method using an LMS (Least Mean Square) algorithm, and is supplied to the attenuator 300.

[0094] When a digital circuit is used for the control unit 301, the attenuator 300 can be realized by arranging switches and resistors in an array, and the attenuation of the attenuator 300 can be varied by turning the switches on and off. The digital signal output from the control unit 301 can be used as the input of the switch, making it possible to eliminate the need for digital-to-analog conversion between the control unit 301 and the attenuator 300.

[0095] Generally, when communication is multi-channelized, the number of frequencies used increases and the frequency bands of each channel become closer. In this embodiment, even when the frequency bands of transmission and reception are close, it is possible to remove only the transmission signal that becomes noise with high accuracy. Therefore, the biological signal measurement system of this embodiment is particularly suitable for measuring a 12-lead electrocardiogram.

[0096] When a signal is received through the body of the subject, the phase of the signal may change. Therefore, a phase shifter that compensates for the changed signal phase may be inserted between the reference signal Ref and the multiplication unit 303. The signal Rx obtained from the receiving electrode 1030 of the sensor device 1-1 is Ｒ Tx included in Ｒ By adjusting the phase of the reference signal Ref so that it is in phase with the component of Tx Ｒ While suppressing performance degradation due to phase changes of the component of the signal Tx from the sensor device 1-2 Ｌ can be obtained.

[0097] In the description of this embodiment, the sensor device 1-1 is taken as an example, but it goes without saying that the same configuration as that shown in FIG. 17 can also be applied to the amplitude detection section 1035 of the sensor device 1-2.

[0098] Fifth Example Next, a fifth example of the present invention will be described. In this example, the attenuation amount adjustment of the attenuation unit 1033a in the second to fourth examples is performed when the sensor devices 1-1 and 1-2 are attached to the measurement subject.

[0099] Fig. 18 is a block diagram showing the configuration of a sensor device 1-1 of this embodiment. The configuration of Fig. 18 is obtained by adding an adjustment instruction unit 105 to the sensor devices 1-1 of the second to fourth embodiments. The configuration of a sensor device 1-2 is similar to that of the sensor device 1-1, and will be described using the reference numerals in Fig. 18.

[0100] 19 is a flowchart illustrating the attenuation adjustment operation of the biological signal measurement system in this embodiment. In this embodiment, when the sensor devices 1-1 and 1-2 are attached to the subject, communication between the sensor devices 1-1 and 1-2 is not started immediately, but rather the attenuation of the attenuation unit 1033a of one of the sensor devices, the sensor device 1-1, is first adjusted.

[0101] When the adjustment instruction unit 105 of the sensor device 1-1 receives data on the bioelectric potential detected by the bioelectrode 1010 from the ADC 1013 of the device after the device is turned on, the adjustment instruction unit 105 determines that the device is attached to the body of the person being measured (step S400 in Figure 19).

[0102] The adjustment instruction unit 105 of the sensor device 1-1 transmits the transmission signal Tx Ｒ The output of the transmission signal Tx by the adjustment instruction unit 105 is turned on. Ｒ The on / off of the transmission signal Tx amplified by the amplifier 1021 of the sensor device 1-1 is realized by, for example, the adjustment instruction unit 105 turning on / off the power supply of the modulator 1022 and the amplifier 1021. Ｒ is transmitted from the transmitting electrode 1020 of the sensor device 1-1 to the sensor device 1-2 through the body of the subject 100 (step S401).

[0103] The amplitude detection unit 1035 of the sensor device 1-1 detects the residual e appearing in the output of the CM component removal unit 1032 of the sensor device 1-1 as the transmitted signal Tx of the sensor device 1-1. Ｒ A signal proportional to the amplitude of the component ｅ is output (step S402).

[0104] The control unit 301 of the attenuation unit 1033a of the sensor device 1-1 detects the output signal A of the amplitude detection unit 1035 of the sensor device itself. ｅ The control signal to be given to the attenuator 300 is changed to adjust the attenuation amount so that the signal A becomes 0 (step S403). As explained in the fourth embodiment, the control unit 301 ｅ The control signal given to the attenuator 300 is changed so that the signal A is equal to or less than the threshold value TH. ｅ When the value of the control signal becomes equal to or smaller than the threshold value TH, the change of the control signal may be stopped.

[0105] When the attenuation amount adjustment by the control unit 301 of the sensor device 1-1 is completed, the adjustment instruction unit 105 of the sensor device 1-1 outputs the transmission signal Tx Ｒ(step S404), and waits for a certain period of time. This waiting period is set to be sufficiently longer than the time required for adjusting the amount of attenuation on the sensor device 1-2 side.

[0106] As with the sensor device 1-1, the adjustment instruction unit 105 of the sensor device 1-2 determines that the device is attached to the body of the subject when the data of the bioelectric potential detected by the bioelectrode 1010 is output from the ADC 1013 of the sensor device 1-2 after the power of the sensor device 1-2 is turned on (step S400). Ｌ is set to a state in which it does not transmit (step S405).

[0107] The sensor device 1-1 transmits a signal Tx Ｒ When the sensor device 1-2 is transmitting the transmission signal Tx, the signal received by the receiving electrode 1030 of the sensor device 1-2 is demodulated by the demodulation unit 1034 of the sensor device 1-2 to obtain information on the biopotential. Ｒ When the transmission of the signal stops, the biopotential information obtained from the demodulation unit 1034 ceases to exist.

[0108] When the bioelectric potential information obtained from the demodulation unit 1034 of the sensor device 1-2 is stopped (step S406), the adjustment instruction unit 105 of the sensor device 1-2 determines that the other sensor device has stopped transmitting, and resets the transmission signal Tx of the sensor device 1-2. Ｌ As a result, the output of the transmission signal Tx amplified by the amplifier 1021 of the sensor device 1-2 is Ｌ is transmitted from the transmitting electrode 1020 of the sensor device 1-2 to the sensor device 1-1 through the body of the subject 100 (step S407).

[0109] The amplitude detection unit 1035 of the sensor device 1-2 detects the residual error e appearing in the output of the CM component removal unit 1032 of the sensor device 1-2, and calculates the residual error e of the transmission signal Tx of the sensor device 1-2. Ｌ A signal proportional to the amplitude of the component ｅ is output (step S408).

[0110] The control unit 301 of the attenuation unit 1033a of the sensor device 1-2 detects the output signal A of the amplitude detection unit 1035 of the sensor device itself. ｅ The control signal to be given to the attenuator 300 is changed to adjust the attenuation amount so that the signal A becomes 0 (step S409). ｅ The control signal given to the attenuator 300 is changed so that the signal A is equal to or less than the threshold value TH. ｅ When the value of the control signal becomes equal to or smaller than the threshold value TH, the change of the control signal may be stopped.

[0111] This completes the attenuation adjustment for the sensor devices 1-1 and 1-2. In step S404, the adjustment instruction unit 105 of the sensor device 1-1 adjusts the attenuation of the transmission signal Tx Ｒ After a certain time has passed since the output of the transmission signal Tx Ｒ This turns on the output of the transmission signal Tx from the sensor device 1-1. Ｒ The transmission is resumed (step S410).

[0112] Signal attenuation during human body transmission is thought to be affected by changes in the contact state between the subject's body and the electrodes. When sensor devices 1-1 and 1-2 are securely attached to the subject's body, the degree of signal attenuation does not change significantly. Therefore, in this embodiment, the attenuation amount is adjusted during the first calibration operation after sensor devices 1-1 and 1-2 are attached to the subject.

[0113] The attenuation adjustment is performed while signal transmission from other sensor devices is stopped. Therefore, the attenuation adjustment can be performed without being affected by the transmission signals from other sensor devices. After the attenuation adjustment, mutual feedback between the sensor devices 1-1 and 1-2 is started, so that noise components appearing in the output of the CM component remover 1032 can be removed and weak signals from other devices can be demodulated.

[0114] 18, the adjustment instruction unit 105 is shown as a separate component from the CPU 106, but the adjustment instruction unit 105 may be realized by the CPU 106. In the example of Fig. 19, the attenuation adjustment is started from the sensor device 1-1 in a predetermined order, but it goes without saying that the attenuation adjustment may be started from the sensor device 1-2.

[0115] Sixth Embodiment Next, a sixth embodiment of the present invention will be described. FIG. 20 is a diagram illustrating the principle of this embodiment. In the first to fifth embodiments, each sensor device was provided with a separate transmitting electrode and a receiving electrode. In contrast, in this embodiment, each sensor device shares the transmitting electrode and the receiving electrode, and a single transmitting / receiving electrode 1090 is provided. Since the transmitting signal Tx of the device itself, amplified by the amplifier 1021, is directly superimposed on the transmitting / receiving electrode 1090, the signal-to-noise ratio is worse than in the first to fifth embodiments.

[0116] Therefore, in this embodiment, in order to achieve high noise removal performance under such adverse conditions, an amplifier 1091 with the same amplification factor as the transmitting amplifier 1021 is provided between the modulator 1022 and the commercial component remover 1032. The amplifier 1091 amplifies the signal output from the modulator 1022. This allows a signal equivalent to the transmission signal Tx of the device itself to be removed to be input to the commercial component remover 1032.

[0117] By directly inputting the output of the amplifier 1091 to the commercial component remover 1032, it is possible to extract only signals from other devices without providing an attenuation section. In this embodiment, too, by using an isolation amplifier for the amplifier 1091 or by providing isolation using the method described in the second embodiment, it is possible to maintain insulation between the subject's body and the main circuits, thereby achieving high biosafety. Because errors may occur in the performance of the amplifiers 1021 and 1091, an attenuation section that attenuates the output signal of the amplifier 1091 may be provided between the amplifier 1091 and the commercial component remover 1032.

[0118] 21 is a block diagram showing the configuration of a sensor device 1-1 according to this embodiment. The sensor device 1-1 includes a bioelectric potential detection unit 101, a modulated signal transmission / reception unit 109, a wireless transmission unit 104, a CPU 106, a memory 107, and a buffer 108.

[0119] The configuration of the biopotential detection unit 101 is the same as in the first to fifth embodiments. The modulated signal transmission / reception unit 109 is made up of an amplifier 1021, a modulator 1022, an amplifier 1031, a commercial component removal unit 1032, an attenuation unit 1033a, a demodulator 1034, an amplitude detection unit 1035, a transmitting / receiving electrode 1090 that comes into contact with the skin on the right side of the subject 100, and an amplifier 1091. The configuration of sensor device 1-2 is the same as that of sensor device 1-1, and will be described using the reference numerals in FIG. 21.

[0120] The processing flow of the sensor devices 1-1 and 1-2 is the same as that of the first embodiment, so the operations of the sensor devices 1-1 and 1-2 will be described using the reference numerals in Figures 5 and 6. The operations of steps S100 to S104 in Figure 5 and steps S200 to S204 in Figure 6 are the same as those of the first embodiment.

[0121] The amplifiers 1021 of the sensor devices 1-1 and 1-2 amplify the modulated signals from the modulators 1022 of the sensor devices 1-1 and 1-2, respectively, and output the amplified signals to the transmitting / receiving electrodes 1090 (steps S105 and S205). As a result, the modulated signals amplified by the amplifiers 1021 of the sensor device 1-1 (transmission signals Tx Ｒ ) is transmitted from the transmitting / receiving electrode 1090 of the sensor device 1-1 to the sensor device 1-2 through the body of the subject 100 (step S106). Similarly, the modulated signal (transmission signal Tx Ｌ ) is transmitted from the transmitting / receiving electrode 1090 of the sensor device 1-2 to the sensor device 1-1 through the body of the subject 100 (step S206).

[0122] The CM component removal unit 1032 of the sensor device 1-1 receives the transmission signal Tx of the sensor device 1-1 from the attenuation unit 1033a of the sensor device 1-1. ＲThe CM component removal unit 1032 of the sensor device 1-2 removes the CM component from the modulated signal Tx of the sensor device 1-2 supplied from the attenuation unit 1033a of the sensor device 1-2 (step S107). Ｌ The component of is removed from the modulated signal received by the transmitting / receiving electrode 1090 of the sensor device 1-2 (step S207).

[0123] The operations of steps S108 to S110 in FIG. 5 and steps S208 to S210 in FIG. 6 are the same as those in the first embodiment.

[0124] As in the second to fifth embodiments, the amplitude detection unit 1035 of each of the sensor devices 1-1 and 1-2 detects the residual error e appearing in the output of the CM component removal unit 1032 of the sensor device itself, and calculates the residual error e that is the transmission signal Tx of the sensor device itself. Ｒ , Tx Ｌ A signal proportional to the amplitude of the component ｅ Output.

[0125] The control unit 301 of the attenuation unit 1033a of each of the sensor devices 1-1 and 1-2 detects the output signal A of the amplitude detection unit 1035 of the device itself. ｅ As explained in the fourth embodiment, the control unit 301 adjusts the attenuation amount by changing the control signal given to the attenuator 300 of the own device so that the signal A ｅ The control signal given to the attenuator 300 is changed so that the signal A is equal to or less than the threshold value TH. ｅ When the value of the control signal becomes equal to or smaller than the threshold value TH, the change of the control signal may be stopped.

[0126] The attenuation units 1033a of the sensor devices 1-1 and 1-2 may be configured to constantly adjust the attenuation amount while the sensor devices 1-1 and 1-2 are in operation. Alternatively, the adjustment instruction unit 105 described in the fifth embodiment may be provided in each of the sensor devices 1-1 and 1-2, and the attenuation adjustment method of the fifth embodiment may be applied to this embodiment.

[0127] Alternatively, the amplitude detection unit 1035 may be omitted, and the attenuation unit 1033a may be replaced with an attenuation unit 1033 having a fixed attenuation amount. Alternatively, the amplitude detection unit 1035 and the attenuation unit 1033a may be omitted, and the amplification unit 1091 and the commercial component removal unit 1032 may be directly connected as described in FIG. 20 .

[0128] The biosignal measurement system of the present invention is not limited to electrocardiogram waveforms, but can also be applied to measurements of myoelectricity, electroencephalograms, and the like.

[0129] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0130] (Supplementary Note 1) A biosignal measurement system of the present invention includes a first sensor device configured to be worn on one of the right and left sides of a subject, and a second sensor device configured to be worn on the other of the right and left sides, and each of the first and second sensor devices includes a first electrode provided to be in contact with the skin of the subject, a first amplifier configured to amplify a biopotential detected by the first electrode, a modulator configured to modulate a carrier wave in accordance with the biopotential amplified by the first amplifier, and a second amplifier configured to amplify a signal output from the modulator, and a second amplifier provided to be in contact with the skin of the subject, The measurement device comprises a second electrode configured to transmit and receive a signal amplified by a second amplifier unit to and from the other sensor device via the body of the person being measured, a third amplifier unit configured to amplify the signal from the other sensor device received by the second electrode, a demodulator unit configured to demodulate the signal amplified by the third amplifier unit to extract information about the biopotential, a reference potential generator unit configured to generate a reference potential for the first amplifier unit based on the biopotential amplified by the first amplifier unit and the biopotential output from the demodulator unit, and a common mode component removal unit configured to remove components of the signal of the device itself to be transmitted to the other sensor device from the signal received by the second electrode.

[0131] (Appendix 2) In the biosignal measurement system described in Appendix 1, each of the first sensor device and the second sensor device further includes an attenuation unit configured to attenuate the signal amplified by the second amplifier unit, and the second electrode comprises a transmitting electrode for transmitting the signal amplified by the second amplifier unit to the other sensor device via the body of the person being measured, and a receiving electrode for receiving the signal from the other sensor device via the body of the person being measured, and the common mode component removal unit removes the output signal of the attenuation unit as a component of the signal of the device itself from the signal received by the receiving electrode.

[0132] (Appendix 3) In the biosignal measurement system described in Appendix 1, each of the first sensor device and the second sensor device further includes a fourth amplifier configured to amplify the signal output from the modulator with the same amplification factor as the second amplifier, and an attenuator configured to attenuate the output signal of the fourth amplifier, and the common mode component removal unit removes the output signal of the attenuator as a component of the signal of the device itself from the signal received by the second electrode.

[0133] (Appendix 4) In the biosignal measurement system described in Appendix 2 or 3, each of the first sensor device and the second sensor device further includes an amplitude detection unit configured to output a signal proportional to the amplitude of a component of the signal of the device itself, among the residuals appearing in the output of the common mode component removal unit, and the attenuation unit adjusts its own attenuation amount based on the output signal of the amplitude detection unit.

[0134] (Appendix 5) In the biosignal measurement system described in Appendix 4, the amplitude detection unit comprises a synchronous detection circuit configured to receive the output signal of the common mode component removal unit and the signal output from the modulation unit or the second amplification unit as inputs, and to extract a component from the output of the common mode component removal unit that has a phase synchronized with the signal of the device itself.

[0135] (Appendix 6) In the biosignal measurement system described in Appendix 4, each of the first sensor device and the second sensor device further includes an adjustment instruction unit configured to cause the attenuation unit to perform attenuation adjustment as a calibration operation for the device itself.

[0136] (Appendix 7) In the biosignal measurement system described in Appendix 6, the adjustment instruction unit of each of the first sensor device and the second sensor device alternately suspends signal transmission to the other sensor device in a predetermined order, and causes the attenuation unit of the own device to adjust the attenuation amount when signal transmission from the other sensor device is stopped.

[0137] The present invention can be applied to a technique for measuring a biological signal.

[0138] 1-1, 1-2...sensor device, 2...external terminal, 101...bioelectric potential detection unit, 102...modulated signal transmission unit, 103...modulated signal reception unit, 104...wireless transmission unit, 105...adjustment instruction unit, 106, 206...CPU, 107, 207...memory, 108, 208...buffer, 109...modulated signal transmission / reception unit, 200...wireless reception unit, 202...data storage unit, 203...data processing unit, 204...data analysis unit, 205...monitor unit, 300...attenuator, 301... Control unit, 302...clock generation unit, 303...multiplication unit, 304...low-pass filter, 1010...bioelectrode, 1011...frequency filter, 1012, 1021, 1031, 1091...amplification unit, 1013...AD conversion unit, 1014...reference potential generation unit, 1020...transmitting electrode, 1022...modulation unit, 1030...receiving electrode, 1032...CM component removal unit, 1033, 1033a...attenuation unit, 1034...demodulation unit, 1035...amplitude detection unit, 1090...transmitting and receiving electrode.

Claims

1. A measurement subject's body comprises a first sensor device configured to be worn on one of the right and left sides of the subject, and a second sensor device configured to be worn on the other of the right and left sides, each of the first sensor device and the second sensor device comprising: a first electrode arranged to contact the skin of the subject, a first amplifier configured to amplify a bioelectric potential detected by the first electrode, a modulator configured to modulate a carrier wave in accordance with the bioelectric potential amplified by the first amplifier, a second amplifier configured to amplify a signal output from the modulator, a second electrode arranged to contact the skin of the subject and configured to transmit and receive the signal amplified by the second amplifier between the subject and the other sensor device via the body of the subject, a third amplifier configured to amplify the signal from the other sensor device received by the second electrode, and a demodulator configured to demodulate the signal amplified by the third amplifier to extract information on the bioelectric potential. A biosignal measurement system comprising: a reference potential generating unit configured to generate a reference potential for the first amplifier based on the biopotential amplified by the first amplifier and the biopotential output from the demodulation unit; and a common mode component removing unit configured to remove components of a signal of the sensor device itself to be transmitted to the other sensor device from the signal received by the second electrode.

2. A biosignal measuring system as described in claim 1, wherein each of the first sensor device and the second sensor device further comprises an attenuation section configured to attenuate the signal amplified by the second amplifier section, the second electrode comprises a transmitting electrode for transmitting the signal amplified by the second amplifier section to the other sensor device via the body of the person being measured, and a receiving electrode for receiving the signal from the other sensor device via the body of the person being measured, and the common mode component removal section removes the output signal of the attenuation section as a component of the signal of the own device from the signal received by the receiving electrode.

3. A biosignal measuring system as described in claim 1, wherein each of the first sensor device and the second sensor device further comprises a fourth amplifier unit configured to amplify the signal output from the modulator unit with the same amplification factor as the second amplifier unit, and an attenuation unit configured to attenuate the output signal of the fourth amplifier unit, and the common mode component removal unit removes the output signal of the attenuation unit as a component of the signal of the device itself from the signal received by the second electrode.

4. A biosignal measuring system as claimed in claim 2 or 3, wherein each of the first sensor device and the second sensor device further comprises an amplitude detection unit configured to output a signal proportional to the amplitude of a component of the signal of the device itself among the residuals appearing in the output of the common mode component removal unit, and the attenuation unit adjusts its own amount of attenuation based on the output signal of the amplitude detection unit.

5. A biosignal measuring system as claimed in claim 4, characterized in that the amplitude detection unit comprises a synchronous detection circuit configured to receive as input the output signal of the common mode component removal unit and the signal output from the modulation unit or the second amplification unit, and to extract from the output of the common mode component removal unit a component whose phase is synchronized with the signal of the device itself.

6. A biosignal measuring system as described in claim 4, wherein each of the first sensor device and the second sensor device further comprises an adjustment instruction unit configured to cause the attenuation unit to perform an attenuation adjustment as a calibration operation for the device itself.

7. A biosignal measuring system as described in claim 6, characterized in that the adjustment instruction unit of each of the first sensor device and the second sensor device alternately pauses signal transmission to the other sensor device in a predetermined order, and when signal transmission from the other sensor device is stopped, causes the attenuation unit of the own device to perform attenuation adjustment.

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