Biosignal measurement system

Abstract

Sensor devices (1-#1 to 1-#3) each comprise: a biosignal acquisition unit (10-1 to 10-3); an amplification unit (11-1 to 11-3) that amplifies the difference between a biosignal and a signal received from another device; a transmission unit (12-1 to 12-3) that transmits an output signal from the amplification unit (11-1 to 11-3) to another device through the body of a measurement subject; a reception unit (13-1 to 13-3) that receives the signal from another device through the body of the measurement subject; and a setting unit (14-1 to 14-3) that sets the transmission frequency of the transmission unit (12-1 to 12-3) and the reception frequency of the reception unit (13-1 to 13-3) so that the signals circulate among three or more devices.

Description

Biosignal Measurement System

[0001] The present invention relates to a biosignal measurement system for measuring biosignals such as cardiac potentials.

[0002] The number of heart disease patients in Japan is increasing year by year. Heart disease is one of the leading causes of death in Japan. 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. For this reason, progress is being made in the development of wearable devices, such as clothing and wrist-worn devices, that can measure electrocardiogram waveforms not only in hospitals and facilities but also in patients' daily lives at home.

[0003] A wearable device has two conductive fabric bioelectrodes and wiring sewn into the inside of the garment. These electrodes and wiring are in contact with the subject's skin. Furthermore, the wearable device wirelessly transmits the measured electrocardiogram waveform to an external terminal using a dedicated transmitter attached to the chest. If the garment size is appropriately selected, such a wearable device can provide stable measurements even when the subject moves, making it suitable for long-term measurement. However, wearable devices have problems, such as the hassle of putting on and taking off the garment for both the subject and medical staff, and the discomfort caused by the electrodes and wiring contacting the skin. This can lead to subjects being reluctant to use them for long periods of time.

[0004] On the other hand, wrist-worn devices are easy to put on and take off and cause little discomfort, making them convenient for subjects to use. However, because wrist-worn devices require subjects to touch the device with their fingers or hands when measuring ECG waveforms, measurements must be taken while the subject is stationary, making them unsuitable for long-term measurements.

[0005] In other words, from the viewpoint of usability, it is desirable that the device be attached to the limbs, and a device that can perform measurements for a long period of time without restricting the body movements of the person being measured is required. To meet these requirements, a system that eliminates inter-electrode wiring to reduce the burden on the person being measured 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 attaching two devices to the left and right limbs of the person being measured, it is possible to measure electrocardiogram waveforms even when the person being measured is moving freely.

[0006] The configuration of the system disclosed in Non-Patent Document 1 is shown in Fig. 14. The biosignal acquisition unit 1001-1 of the sensor device 1000-1 acquires a biosignal V such as a cardiac potential measured by a first biosignal measurement electrode attached to the left hand of the subject 100. Ｌ The biosignal acquisition unit 1001-2 of the sensor device 1000-2 receives a biosignal V such as a cardiac potential measured by a second biosignal measurement electrode attached to the right hand of the subject 100. Ｒ is input to the amplifier 1002-2.

[0007] The transmitter 1003-1 of the device 1000-1 receives the output signal V １ is transmitted from a first transmitting electrode attached to the left hand of the subject 100 to the device 1000-2 through the body of the subject 100. The transmitting section 1003-2 of the device 1000-2 transmits the output signal V ２ is transmitted from a second transmitting electrode attached to the right hand of the subject 100 through the body of the subject 100 to the device 1000-1.

[0008] The receiving section 1004-1 of the device 1000-1 receives a signal V ２ The receiving section 1004-2 of the device 1000-2 receives the signal V １ is input to the amplifier 1002-1.

[0009] The amplifiers 1002-1 and 1002-2 are used to weaken in-phase signals and strengthen out-of-phase signals. The out-of-phase signals indicate that the biosignals measured by device 1000-1 and device 1000-2 are in an out-of-phase relationship. Therefore, it is necessary to feed back the biosignals measured by device 1000-2 and input them to the inverting input terminal of the amplifier of device 1000-1. Similarly, it is necessary to feed back the biosignals measured by device 1000-1 and input them to the inverting input terminal of the amplifier of device 1000-2.

[0010] 14, mutual feedback between amplifiers 1002-1 and 1002-2 is realized by the human body pathway. When the mutual feedback functions normally, the output from amplifiers 1002-1 and 1002-2 is a signal in which the opposite-phase signal is strengthened. Wireless transmitters (not shown) of devices 1000-1 and 1000-2 wirelessly transmit the output signals of amplifiers 1002-1 and 1002-2, respectively, to an external terminal. The external terminal calculates the difference between the signal transmitted from device 1000-1 and the signal transmitted from device 1000-2 as an electrocardiogram waveform.

[0011] The configuration shown in Figure 14 eliminates the need for wiring between devices, making it possible to measure electrocardiogram waveforms without restraining the subject's body. However, in order to achieve electrocardiogram measurement methods such as limb leads or twelve leads, or to measure electroencephalograms, more than two devices or electrodes must be attached to the subject's body, which creates problems such as bulky devices and increased power consumption. Because the devices are battery-powered, increased power consumption shortens the device's operating time.

[0012] 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

[0013] The present invention has been made to solve the above-mentioned problems, and has an object to provide a biosignal measurement system that can reduce the circuitry of each sensor device and reduce power consumption.

[0014] The biosignal measurement system of the present invention comprises three or more sensor devices attached to three or more parts of a subject, each of which comprises a biosignal acquisition unit configured to acquire the biosignal of the subject, an amplifier configured to amplify the difference between the biosignal and a signal received from another sensor device, a transmitter configured to transmit an output signal of the amplifier to another sensor device via the body of the subject, a receiver configured to receive signals from another sensor device via the body of the subject, and a setting unit configured to set the transmission frequency of the transmitter and the reception frequency of the receiver so that the sensor device that receives the signal transmitted from its own device is different from the sensor device that transmits the signal received by the receiver, and so that signals circulate among the three or more sensor devices.

[0015] According to the present invention, by providing each sensor device with a setting unit that sets the transmission frequency of the transmitter and the reception frequency of the receiver so that signals circulate among three or more sensor devices, even when three or more sensor devices are provided to perform detailed biological signal measurement, the circuitry of each sensor device can be reduced and power consumption can be reduced.As a result, the operating time of each sensor device can be extended and the number of times it needs to be charged can be reduced.

[0016] FIG. 1 is a circuit diagram showing the configuration of an amplifier unit of a conventional measurement system. FIG. 2 is a diagram explaining limb leads. FIG. 3 is a block diagram showing a configuration when a conventional measurement system is applied to limb leads. FIG. 4 is a diagram showing an overview of a biosignal measurement system according to an embodiment of the present invention. FIG. 5 is a block diagram showing the configuration of a biosignal measurement system according to an embodiment of the present invention. FIG. 6 is a flowchart explaining a transmission / reception frequency setting operation of a sensor device according to an embodiment of the present invention. FIG. 7 is a flowchart explaining a transmission / reception frequency setting operation of a sensor device according to an embodiment of the present invention. FIG. 8 is a flowchart explaining a transmission / reception frequency setting operation of a sensor device according to an embodiment of the present invention. FIG. 9 is a circuit diagram showing the configuration of an amplifier unit of a sensor device according to an embodiment of the present invention. FIG. 10 is a diagram explaining another method of measuring limb leads. FIG. 11 is a diagram explaining a method of measuring twelve leads. FIG. 12 is a diagram explaining a method of measuring electroencephalograms. FIG. 13 is a block diagram showing an example of the configuration of a computer realizing an external terminal according to an embodiment of the present invention. FIG. 14 is a block diagram showing the configuration of a conventional measurement system.

[0017] [Principle of the invention] The technology disclosed in Non-Patent Document 1 reproduces, without wiring, a differential amplifier circuit that can amplify only the differential components, which are biosignals, without amplifying the in-phase components (common mode components), which are noise, by transmitting amplified signals between devices worn on both hands of the subject.

[0018] Figure 1 shows the configuration of amplifiers 1002-1 and 1002-2 of the conventional measurement system shown in Figure 14. Amplifier 1002-1 is composed of an operational amplifier A-1 and resistors R1-1, R2-1, and R3-1. Amplifier 1002-2 is composed of an operational amplifier A-2 and resistors R1-2, R2-2, and R3-2.

[0019] The biological signal acquired by the biological signal acquisition unit 1001-1 of the sensor device 1000-1 is V Ｌ , the biological signal acquired by the biological signal acquisition unit 1001-2 of the sensor device 1000-2 is V Ｒ , the output signal of the amplifier 1002-1 is V １ , the output signal of the amplifier 1002-2 is V ２The value of the resistors R1-1 and R1-2 is R, and the value of the resistors R2-1 and R2-2 is R Ｇ / 2, the value of resistors R3-1 and R3-2 is R+R Ｇ The transfer function equation from the input to the output of the amplifier 1002-1 is as shown in equation (1), and the transfer function equation from the input to the output of the amplifier 1002-2 is as shown in equation (2).

[0020]

[0021] Here, V Ｌ , V Ｒ is the in-phase noise component V ＣＭ and the opposite-phase signal component V ＳＩＧ and are expressed as equations (3) and (4), respectively.

[0022]

[0023] From equations (3) and (4), equations (1) and (2) can be transformed into equations (5) and (6). Equations (5) and (6) indicate that only the signal component is amplified.

[0024]

[0025] The configuration shown in Fig. 14 uses two sensor devices. On the other hand, a limb lead measurement method requires three sensor devices 2000-1 to 2000-3 as shown in Fig. 2. Measuring the potential between the left and right hand as indicated by dotted line 200 is called lead I, measuring the potential between the left foot and right hand as indicated by dotted line 201 is called lead II, and measuring the potential between the left foot and left hand as indicated by dotted line 202 is called lead III. When attempting to apply the technology disclosed in Non-Patent Document 1 to limb leads, the measurement system would have a configuration as shown in Fig. 3.

[0026] The biosignal acquisition unit 2001-1 of the sensor device 2000-1 is attached to the right hand of the subject 100, and acquires a biosignal V ＲＡ The biological signal acquisition unit 2001-2 of the sensor device 2000-2 is attached to the left hand of the subject 100, and receives the biological signal V ＬＡThe biological signal acquisition unit 2001-3 of the sensor device 2000-3 is attached to the left foot of the subject 100, and receives the biological signal V ＬＬ are acquired and input to the amplifiers 2002-1-3 and 2002-2-3.

[0027] Transmitting section 2003-1-1 of device 2000-1 modulates a carrier wave of a first frequency in accordance with the output signal of amplifying section 2002-1-1 and transmits the modulated signal. Receiving section 2004-1-2 of device 2000-2 demodulates the modulated signal of the first frequency transmitted from transmitting section 2003-1-1 and inputs the extracted signal to amplifying section 2002-1-2. Transmitting section 2003-2-1 of device 2000-1 modulates a carrier wave of a second frequency in accordance with the output signal of amplifying section 2002-2-1 and transmits the modulated signal. Receiving section 2004-1-3 of device 2000-3 demodulates the modulated signal of the second frequency transmitted from transmitting section 2003-2-1 and inputs the extracted signal to amplifying section 2002-1-3.

[0028] Transmitting section 2003-1-2 of device 2000-2 modulates a carrier wave of a third frequency in accordance with the output signal of amplifying section 2002-1-2 and transmits the modulated signal. Receiving section 2004-1-1 of device 2000-1 demodulates the modulated signal of the third frequency transmitted from transmitting section 2003-1-2 and inputs the extracted signal to amplifying section 2002-1-1. Transmitting section 2003-2-2 of device 2000-2 modulates a carrier wave of a fourth frequency in accordance with the output signal of amplifying section 2002-2-2 and transmits the modulated signal. Receiving section 2004-2-3 of device 2000-3 demodulates the modulated signal of the fourth frequency transmitted from transmitting section 2003-2-2 and inputs the extracted signal to amplifying section 2002-2-3.

[0029] The transmitter 2003-1-3 of the device 2000-3 modulates a carrier wave of a fifth frequency in accordance with the output signal of the amplifier 2002-1-3 and transmits the modulated signal. The receiver 2004-2-1 of the device 2000-1 demodulates the modulated signal of the fifth frequency transmitted from the transmitter 2003-1-3 and inputs the extracted signal to the amplifier 2002-2-1. The transmitter 2003-2-3 of the device 2000-3 modulates a carrier wave of a sixth frequency in accordance with the output signal of the amplifier 2002-2-3 and transmits the modulated signal. The receiver 2004-2-2 of the device 2000-2 demodulates the modulated signal of the sixth frequency transmitted from the transmitter 2003-2-3 and inputs the extracted signal to the amplifier 2002-2-2.

[0030] The amplifiers 2002-1-1 and 2002-2-1 of the device 2000-1 receive the biological signal V ＲＡ The amplifiers 2002-1-2 and 2002-2-2 of the device 2000-2 amplify the biological signal V ＬＡ The amplifiers 2002-1-3 and 2002-2-3 of the device 2000-3 amplify the biological signal V ＬＬ Amplify.

[0031] As described above, in order to realize the limb lead measurement method shown in FIG. 2, three devices 2000-1 to 2000-3 are required, which results in an increase in circuit size and power consumption.

[0032] [Example] An example of the present invention will be described below with reference to the drawings. FIG. 4 is a diagram showing an overview of a biosignal measurement system according to an example of the present invention. In this example, sensor device 1-#1 worn on the right hand of subject 100 transmits a signal to sensor device 1-#2 worn on the left hand of subject 100. Sensor device 1-#2 transmits a signal to sensor device 1-#3 worn on the left foot of subject 100. Sensor device 1-#3 transmits a signal to sensor device 1-#1. In this way, a circulating transmission and reception network is formed.

[0033] Device 1-#1 has a transmitter that includes a first frequency in its transmission frequency and a receiver that includes a third frequency in its reception frequency. Device 1-#2 has a transmitter that includes a second frequency in its transmission frequency and a receiver that includes the first frequency in its reception frequency. Device 1-#3 has a transmitter that includes a third frequency in its transmission frequency and a receiver that includes the second frequency in its reception frequency. This makes it possible to transmit signals only to a specific device that has a receiver that corresponds to the transmission frequency band of that device. Furthermore, each device only needs to be provided with one transmitter and one receiver. Therefore, in this embodiment, the number of transmitters and receivers can be reduced compared to the configuration shown in FIG. 3.

[0034] In this embodiment, the number of frequency bands used can be reduced compared to conventional methods, thereby reducing the risk of frequency interference even when using the same communication path, the human body. Any modulation method can be used to convert biosignals into modulated signals. However, the human body is an unstable transmission medium depending on posture and movement. Therefore, frequency modulation or phase modulation is preferred as the modulation method.

[0035] The biological signal output from the amplifier unit of the device is input to the transmitter, and voltage-frequency conversion is performed by a voltage-controlled oscillator (VCO). By setting the VCO oscillation frequency to a different frequency for each device, the transmission frequency band of each device can be made different. For the demodulator in the receiver, a detection circuit that performs frequency-voltage conversion or a PLL (Phase-Locked Loop) demodulator can be used. Simply set the circuit constant of the demodulator corresponding to the frequency to be received, and by setting the circuit constant differently for each device, the reception frequency band of each device can be made different.

[0036] In this way, a unique transmit / receive frequency can be assigned to each device in advance, and the subject can wear each device in a designated location. However, if the transmit / receive frequencies are fixed in advance, increasing the number of devices and performing measurements requires configuring the receivers of existing devices to be able to handle the modulated signals of the frequency transmitted by the newly added devices, which requires a complex switching function. Therefore, the frequency is dynamically set each time a device is worn.

[0037] 5 is a block diagram showing the configuration of the biosignal measurement system of this embodiment. Device 1-#1 has a biosignal acquisition unit 10-1, an amplifier unit 11-1, a transmitter unit 12-1, a receiver unit 13-1, a setting unit 14-1, and a wireless transmitter unit 15-1. Device 1-#2 has a biosignal acquisition unit 10-2, an amplifier unit 11-2, a transmitter unit 12-2, a receiver unit 13-2, a setting unit 14-2, and a wireless transmitter unit 15-2. Device 1-#3 has a biosignal acquisition unit 10-3, an amplifier unit 11-3, a transmitter unit 12-3, a receiver unit 13-3, a setting unit 14-3, and a wireless transmitter unit 15-3.

[0038] The biosignal acquiring unit 10-1 of the device 1-#1 acquires a biosignal V such as a cardiac potential measured by a first biosignal measuring electrode attached to the right hand of the subject 100. ＲＡ The biosignal acquiring unit 10-2 of the device 1-#2 acquires a biosignal V such as a cardiac potential measured by a second biosignal measuring electrode attached to the left hand of the subject 100. ＬＡ The biosignal acquiring unit 10-3 of the device 1-#3 acquires a biosignal V such as a cardiac potential measured by a third biosignal measuring electrode attached to the left leg of the subject 100. ＬＬ Here, device 1-#1 is worn on the right hand of the subject 100, device 1-#2 is worn on the left hand, and device 1-#3 is worn on the left foot, but as will be described later, the wearing positions are not limited to this example. The biological signal acquisition units 10-1 to 10-3 may be equipped with a filter circuit that low-pass filters the biological signal.

[0039] The transmitter 12-1 of the device 1-#1 receives the output signal V １The modulated signal is transmitted from the transmitting electrode of the transmitting unit 12-1 to another device through the body of the subject 100. The receiving unit 13-2 of the device 1-#2 demodulates the modulated signal transmitted from the transmitting unit 12-1 and received by the receiving electrode of the receiving unit 13-2, and extracts the signal V １ is input to the amplifier 11-2.

[0040] The transmitter 12-2 of the device 1-#2 receives the output signal V ２ The modulated signal is transmitted from the transmitting electrode of the transmitting unit 12-2 to another device through the body of the subject 100. The receiving unit 13-3 of the device 1-#3 demodulates the modulated signal transmitted from the transmitting unit 12-2 and received by the receiving electrode of the receiving unit 13-3, and extracts the signal V ２ is input to the amplifier 11-3.

[0041] The transmitter 12-3 of the device 1-#3 receives the output signal V ３ The modulated signal is transmitted from the transmitting electrode of the transmitting unit 12-3 to another device through the body of the subject 100. The receiving unit 13-1 of the device 1-#1 demodulates the modulated signal transmitted from the transmitting unit 12-3 and received by the receiving electrode of the receiving unit 13-1, and extracts the signal V ３ is input to the amplifier 11-1.

[0042] The amplifier 11-1 of the device 1-#1 receives the biological signal V ＲＡ and the signal V input from the receiving unit 13-1 ３ The amplifier 11-2 of the device 1-#2 amplifies the difference between the biological signal V ＬＡ and the signal V input from the receiving unit 13-2 １ The amplifier 11-3 of the device 1-#3 amplifies the difference between the biological signal V ＬＬ and the signal V input from the receiving unit 13-3 ２ amplify the difference between

[0043] The wireless transmitting unit 15-1 of the device 1-#1 receives the output signal V １and its own device number #1 are converted into a digital signal and transmitted wirelessly to the external terminal 2. The wireless transmitting unit 15-2 of the device 1-#2 converts the output signal V ２ and its own device number #2 are converted into a digital signal and transmitted wirelessly to the external terminal 2. The wireless transmission unit 15-3 of the device 1-#3 converts the output signal V ３ and its own device number #3 are converted into a digital signal and wirelessly transmitted to the external terminal 2. The external terminal 2 receives the signal V １ , V ２ , V ３ The electrocardiogram waveform is calculated based on the above.

[0044] FIG. 6 is a flowchart explaining the transmitting and receiving frequency setting operation of device 1-#1, FIG. 7 is a flowchart explaining the transmitting and receiving frequency setting operation of device 1-#2, and FIG. 8 is a flowchart explaining the transmitting and receiving frequency setting operation of device 1-#3.

[0045] For ease of description, we will assign device numbers starting from #1 in the order in which the devices are worn by the subject. Each device has the ability to change the transmission and reception frequency. Specifically, if the frequency is set using an LC circuit, the frequency can be changed by changing the values ​​of inductance L and capacitance C. Also, if the frequency is controlled digitally, the frequency can be changed by changing the parameters.

[0046] Here, it is assumed that the order of frequencies to be used is known, i.e., one of the following is set in advance as a common frequency allocation method for all devices: a method of allocating frequencies in order from lowest to highest, a method of allocating frequencies in order from highest to lowest, or a method of allocating frequencies in any order specified by the user.

[0047] When the subject wears device 1-#1, since no other devices are worn, signals from other devices are input to the receiver 13-1 of device 1-#1. Since the receiver 13-1 does not receive signals from other devices, the setting unit 14-1 of device 1-#1 recognizes that it is the first device (YES in step S100 of FIG. 6 ) and sets the frequency of the transmitter 12-1 of device 1-#1 to transmit a modulated signal at the first frequency (step S101 of FIG. 6 ).

[0048] Furthermore, the setting unit 14-1 of the device 1-#1 sets the frequency of the receiving unit 13-1 so that it receives a modulated signal of the second frequency that will be used next after the currently received frequency (step S102 in FIG. 6). In other words, the only signal that can be received at this time is the modulated signal of the first frequency that is being transmitted from the device itself. Therefore, the device 1-#1 sets the second frequency as the receiving frequency.

[0049] Next, when the subject wears device 1-#2, a modulated signal of a first frequency is input to the receiver 13-2 of device 1-#2. When the receiver 13-2 receives a modulated signal of one frequency, the setting unit 14-2 of device 1-#2 recognizes that it is the second device (YES in step S200 of FIG. 7) and sets the frequency of the receiver 13-2 to receive the modulated signal of the first frequency (step S201 of FIG. 7). This setting enables device 1-#2 to demodulate the modulated signal of the first frequency and extract the biosignal. It is preferable to determine that a signal has been received when the received signal level of the modulated signal is equal to or greater than a predetermined threshold, and to determine that a signal has not been received when the received signal level of the modulated signal is less than the threshold.

[0050] In addition, the setting unit 14-2 of device 1-#2 sets the frequency of the transmitting unit 12-2 of device 1-#2 so as to transmit a modulated signal of a second frequency that will be used next after the first frequency currently being received (step S202 in Figure 7).

[0051] Next, when the subject wears device 1-#3, a modulated signal of the first frequency and a modulated signal of the second frequency are input to the receiver 13-3 of device 1-#3. The setting unit 14-3 of device 1-#3 recognizes that it is the third device because the receiver 13-3 receives the modulated signals of the two frequencies (YES in step S300 of FIG. 8). The order of frequencies to be used is known. Therefore, the setting unit 14-3 sets the frequency of the receiver 13-3 to receive the modulated signal of the second frequency, which is the last frequency of the first and second frequencies (step S301 of FIG. 8). This setting allows device 1-#3 to demodulate the modulated signal of the second frequency and extract the biosignal.

[0052] In addition, the setting unit 14-3 of device 1-#3 sets the frequency of the transmitting unit 12-3 of device 1-#3 so as to transmit a modulated signal of the third frequency that will be used next after the second frequency currently being received (step S302 in FIG. 8).

[0053] When a modulated signal of the third frequency, which is used next after the second frequency, is newly input to the receiving unit 13-1 of device 1-#1 (YES in step S103 in FIG. 6), the setting unit 14-1 of device 1-#1 changes the frequency of the receiving unit 13-1 so that it receives the modulated signal of the third frequency (step S104 in FIG. 6). This setting enables device 1-#1 to demodulate the modulated signal of the third frequency and extract the biosignal. Note that only the first device changes the receiving frequency in this manner.

[0054] In this way, in this embodiment, it is possible to dynamically set the transmission and reception frequencies and enable measurement of biological signals even when the number of devices is 3. Even when the number of devices exceeds 3, a configuration can be made in which signals circulate through the devices by a similar operation.

[0055] The order of signal transmission is not limited to the examples in Figures 6 to 8, and may be Device 1-#1 → Device 1-#3 → Device 1-#2 → Device 1-#1. Furthermore, the device may be worn on any part of the subject's body depending on the information to be measured.

[0056] Next, the detailed operation of this embodiment will be described using an example of measuring limb leads. Figure 9 is a circuit diagram showing the configuration of amplifiers 11-1 to 11-3. The circuit constants described below may be changed arbitrarily without any problems.

[0057] The amplifier 11-1 of the device 1-#1 receives the biological signal V at its non-inverting input terminal. ＲＡ an operational amplifier A-1 to which the signal V is input, a resistor R1-1 provided between the inverting input terminal and the output terminal of the operational amplifier A-1, a resistor R2-1 having one end connected to the inverting input terminal of the operational amplifier A-1, and a resistor R3-1 having one end connected to the other end of the resistor R3-1 and having the other end connected to the other end of the resistor R3-1. ３ and a resistor R3-1 to which the

[0058] The amplifier 11-2 of the device 1-#2 receives the biological signal V at its non-inverting input terminal. ＬＡ an operational amplifier A-2 to which the signal V is input; a resistor R1-2 provided between the inverting input terminal and the output terminal of the operational amplifier A-2; a resistor R2-2 having one end connected to the inverting input terminal of the operational amplifier A-2; and a resistor R3-2 having one end connected to the other end of the resistor R3-2 and having the other end connected to the other end of the resistor R3-2. １ and a resistor R3-2 to which the

[0059] The amplifier 11-3 of the device 1-#3 receives the biological signal V at its non-inverting input terminal. ＬＬ an operational amplifier A-3 to which the signal V is input, a resistor R1-3 provided between the inverting input terminal and the output terminal of the operational amplifier A-3, a resistor R2-3 having one end connected to the inverting input terminal of the operational amplifier A-3, and a resistor R3-3 having one end connected to the other end of the resistor R3-3 and having the other end connected to the other end of the resistor R3-3. ２ and a resistor R3-3 to which is input.

[0060] The values ​​of resistors R1-1 to R1-3 are R, and the values ​​of resistors R2-1 to R2-3 are R Ｇ / 2, the value of resistors R3-1 to R3-3 is R + R Ｇ / 2, the output signals V of the amplifiers 11-1 to 11-3 are １ ~V ３ is expressed as equations (7) to (9).

[0061]

[0062] The α and β in the formulas (7) to (9) are as shown in the formulas (10) and (11).

[0063]

[0064] The external terminal 2 receives the signal V １ ~V ３ By carrying out the processing shown in equations (12) to (14) for

[0065]

[0066] V Ｉ is the induced potential, V ＩＩ is the potential of induction II, V ＩＩＩ is the potential of lead III. In this embodiment, an electrocardiogram has been taken as an example, but it is also possible to calculate potential information between any two points in an electromyogram or an electroencephalogram using a similar configuration.

[0067] Here, when the output potential of each device is evaluated in the case where common mode noise is superimposed, the result is as shown in equation (15).

[0068] ...(15)

[0069] As can be seen from equation (15), the common mode noise V ＣＭ In the case of the amplifier 11-1 of the device 1-#1, the signal V acquired by the device 1-#1 is not amplified. ＲＡ and the signal V sent from device 1-#3 ３ By calculating the difference between ＣＭ While canceling the signal V ＲＡ Although equation (15) shows the case of the amplifier 11-1, the same result can be obtained for the other amplifiers 11-2 and 11-3.

[0070] Since the formula (16) holds, R=R so that the gains of the amplifiers 11-1 to 11-3 become maximum. Ｇ It is preferable to set the following.

[0071]

[0072] The maximum value of equation (16) is 4 / 3. Therefore, a high-precision A / D converter may be provided in each of the wireless transmitting units 15-1 to 15-3, or additional amplifier circuits may be provided before and after the amplifier units 11-1 to 11-3. Also, a filter circuit, a bias circuit, etc. may be added.

[0073] In this embodiment, the case where there are three devices has been described, but more devices may be added. When the number of devices is 2n (n is a natural number), equations (7) to (9) become equation (17).

[0074]

[0075] V １ ~V ２ｎ is the output signal of the amplifiers 11-1 to 11-2n, and v １ ~v ２ｎ is a biological signal acquired by the biological signal acquiring units 10-1 to 10-2n. Generalizing equation (17) gives equation (18).

[0076]

[0077] In formula (18), V ０ =V ２ｎ , i is a natural number between 1 and 2n. Since α and β are known values, an arbitrary potential difference v ｉ -v ｊ is obtained in the same way as in the case of three devices. Also, the common mode noise v ＣＭ When the output signal V of the amplifier 11-i is superimposed ｉ is expressed as in equation (19).

[0078] ...(19)

[0079] As can be seen from equation (19), even when the number of devices is 2n, the common-mode noise V ＣＭ is not amplified, and only the composite component of the signal to be detected is amplified. Ｇ When , equation (20) holds.

[0080]

[0081] The coefficient of the first term in equation (20) can be approximated as in equation (21).

[0082]

[0083] Therefore, if the number of devices is 2n, i.e., an even number, R can be set to R Ｇ By making it sufficiently larger, for example, 100 to 1000 times or more, a high gain can be obtained, and it is possible to achieve both a high gain and a reduced circuit. As described above, when the number of devices is odd, R = R Ｇ This can be done as follows.

[0084] When measuring an electrocardiogram using the limb lead measurement method, it is effective to use right leg drive (RLD) in addition to both hands and the left foot (Figure 10). Device 1-#1 transmits a modulated signal at a first frequency. Device 1-#2 transmits a modulated signal at a second frequency. Device 1-#3 transmits a modulated signal at a third frequency. Device 1-#4 transmits a modulated signal at a fourth frequency.

[0085] Furthermore, when measuring an electrocardiogram using the twelve-lead measurement method, a device is also required on the subject's chest, and the device is therefore positioned as shown in Figure 11. The device worn on the chest is equipped with multiple biosignal measurement electrodes so that twelve leads V1 to V6 can be measured. Alternatively, multiple devices may be worn on the chest. Furthermore, when measuring electroencephalograms, devices 1-#1 to 1-#6 may be placed at the locations to be measured, as shown in Figure 12.

[0086] In this embodiment, the devices may be attached to any part of the subject, but the external terminal 2 must recognize which part of the subject corresponds to the potential of the signal transmitted from each device, and perform calculations such as those shown in Equations (7) to (9) and (18) to calculate an electrocardiogram waveform, etc.

[0087] The subject then inputs the device number and the part of the body where the device is attached into the smartphone. The smartphone then transmits the device number and information indicating the part of the body where the device is attached to the external terminal 2. This allows the external terminal 2 to recognize the part of the body where each device is attached.

[0088] Alternatively, each device may be provided with an input unit for inputting the wearing position, and the subject may input the wearing position of the device. The wireless transmission unit 15 of each device transmits the output signal of the amplifier 11, the device number, and information indicating the part where the device is worn to the external terminal 2.

[0089] In the description of this embodiment, the resistors R2-1 to R2-3 and R3-1 to R3-3 are described separately for technical ease of understanding, but the resistors R2-1 and R3-1 may be combined into one resistor, the resistors R2-2 and R3-2 may be combined into one resistor, and the resistors R2-3 and R3-3 may be combined into one resistor. When combined into one, the combined resistance is R + R Ｇ is.

[0090] The external terminal 2 described in this embodiment can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0091] The computer includes a CPU 300, a storage device 301, and an interface device (I / F) 302. The I / F 302 is connected to hardware such as a wireless communication unit that communicates with each device. In such a computer, a program for implementing the biosignal measurement method of the present invention is stored in the storage device 301. The CPU 300 executes the processing described in this embodiment in accordance with the program stored in the storage device 301.

[0092] Some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0093] (Supplementary Note 1) The biosignal measurement system of the present invention comprises three or more sensor devices attached to three or more parts of a subject, each of which comprises a biosignal acquisition unit configured to acquire a biosignal of the subject, an amplifier configured to amplify the difference between the biosignal and a signal received from another sensor device, a transmitter configured to transmit an output signal of the amplifier to another sensor device via the body of the subject, a receiver configured to receive a signal from another sensor device via the body of the subject, and a setting unit configured to set the transmission frequency of the transmitter and the reception frequency of the receiver so that a sensor device that receives a signal transmitted from its own device is different from a sensor device that transmits a signal received by the receiver, and so that a signal circulates among the three or more sensor devices.

[0094] (Appendix 2) In the biosignal measurement system described in Appendix 1, the amplification unit is composed of an operational amplifier to which the biosignal is input at its non-inverting input terminal, a first resistor arranged between the inverting input terminal and output terminal of the operational amplifier, and a second resistor having one end connected to the inverting input terminal of the operational amplifier and the other end to which the signal received by the receiving unit is input.

[0095] (Supplementary Note 3) In the biosignal measurement system according to Supplementary Note 2, the number of the sensor devices is odd, the value of the first resistor is R, and the value of the second resistor is R+R Ｇ Then, R = R Ｇ is.

[0096] (Supplementary Note 4) In the biosignal measurement system according to Supplementary Note 2, the number of the sensor devices is even, the value of the first resistor is R, and the value of the second resistor is R+R Ｇ When this is the case, R>R Ｇ is.

[0097] 1-#1 to 1-#3...sensor device, 2...external terminal, 10-1 to 10-3...biological signal acquisition unit, 11-1 to 11-3...amplification unit, 12-1 to 12-3...transmission unit, 13-1 to 13-3...reception unit, 14-1 to 14-3...setting unit, 15-1 to 15-3...wireless transmission unit, A-1 to A-3...operational amplifier, R1-1 to R1-3, R2-1 to R2-3, R3-1 to R3-3...resistor.

Claims

1. A biosignal measurement system comprising three or more sensor devices attached to three or more body parts of a subject, each sensor device comprising: a biosignal acquisition unit configured to acquire the biosignal of the subject; an amplifier unit configured to amplify the difference between the biosignal and a signal received from another sensor device; a transmitter unit configured to transmit an output signal of the amplifier unit to the other sensor devices via the body of the subject; a receiver unit configured to receive signals from the other sensor devices via the body of the subject; and a setting unit configured to set the transmission frequency of the transmitter unit and the reception frequency of the receiver unit so that the sensor device that receives the signal transmitted from its own device is different from the sensor device that transmits the signal received by the receiver, and so that signals circulate among the three or more sensor devices.

2. A biosignal measurement system according to claim 1, wherein the amplification section comprises an operational amplifier to which the biosignal is input at its non-inverting input terminal, a first resistor provided between the inverting input terminal and output terminal of the operational amplifier, and a second resistor having one end connected to the inverting input terminal of the operational amplifier and the other end to which the signal received by the receiving section is input.

3. A biosignal measurement system according to claim 2, wherein the number of the sensor devices is odd, the value of the first resistor is R, and the value of the second resistor is R+R. Ｇ Then, R = R Ｇ A biological signal measuring system characterized by:

4. A biosignal measurement system according to claim 2, wherein the number of the sensor devices is even, the value of the first resistor is R, and the value of the second resistor is R+R. Ｇ When this is the case, R>R Ｇ A biological signal measuring system characterized by:

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