JPH11188015A - Biological signal measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio multi-channel biological signals measuring apparatus of judging radio interference easily and improve a measuring accuracy. SOLUTION: A radio electrode 121 has a detection electrode 201, 202 which inputs the bionic signal S1, a mixed amplification circuit 22 which mixes a standard signal C1 of the frequency that is not included in the frequency of a bionic signal S1 into the biological signal S1 to amplify as a detection signal D1, and a modulation transmission circuit 24 which modulates the detection signal D1 output from mixed amplification circuit 22 to a carrier FM1 in a different frequency to every radio electrode 121 and so on to transmit. A receiver 141 has a receiving modulation circuit 26 which receives the detection signal D1 transmitted from the radio electrode 121 and demodulates it and a filter circuit 28 which separates the detection signal D1 output from the receiving modulation circuit 26 into the bionic signal S1 and the standard signal C1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a biological signal measurement device that wirelessly measures biological signals such as MG), electro-oculogram (EOG), electrocardiogram (ECG), and electroencephalogram (EEG). This biological signal measuring device is applicable not only to the medical field but also to physiological fields including kinematics and psychological fields such as attention and arousal.

[0002]

2. Description of the Related Art A biological signal measuring device for wirelessly measuring a single biological signal is disclosed in JP-A-2-283354, JP-A-63-49135, and the like. This biological signal measuring device is configured to be able to measure a biological signal without restricting the subject's behavior by adding a wireless transmission function to an electrode worn on the subject. An electrode having such a wireless transmission function is hereinafter referred to as a “wireless electrode”.

At present, a biological signal measuring device capable of simultaneously measuring not a single biological signal but a plurality of biological signals (hereinafter referred to as a "multi-channel biological signal measuring device") is only a wired device having electrodes with lead wires. Yes, no completely wireless version is known. A multi-channel biological signal measurement device that is completely wireless by the conventional technology includes a plurality of wireless electrodes and a plurality of receivers corresponding to each wireless electrode, and changes a carrier frequency for each wireless electrode. Can be considered.

[0004]

However, in such a wireless multi-channel biological signal measuring device,
The following problems occur.

(1) In the case of a wireless electrode, it is required that a built-in battery and a circuit be as small as possible so that the wireless electrode can be worn on the skin without placing a burden on a subject. Therefore, the capacity of the battery is small, and the compensating circuit is limited.
As a result, a drop in power supply voltage or a change in ambient temperature
The carrier frequency may shift. This shift of the carrier frequency causes interference at the receiver, so that large noise is mixed in the obtained biological signal. Also, it is assumed that the plurality of wireless electrodes have different carrier frequencies,
Interference may occur due to the incorrect setting of the carrier frequency. However, in these cases, it is extremely difficult to judge whether or not there is interference, since it depends only on the intuition of a skilled person.

(2) Since the biological signal has a very small voltage value of about several μV to several tens mV, it is amplified and measured. Then, the data of the biological signal is converted based on the amplification factor,
It is treated as the voltage value before amplification. However, since the amplification factor changes due to fluctuations in the ambient temperature, the power supply voltage, and the like, the value of the converted biological signal includes a considerable amount of error.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless multi-channel biological signal measuring apparatus which can firstly determine interference and improve measurement accuracy.

[0008]

A biological signal measuring device according to the present invention comprises a plurality of wireless electrodes which are attached to the skin and transmit biological signals wirelessly, and a plurality of receiving electrodes respectively corresponding to these wireless electrodes. Machine. The wireless electrode is configured to mix and amplify a detection electrode for inputting a biological signal and a reference signal having a frequency not included in the frequency band of the biological signal with a biological signal input from the detection electrode and output the amplified signal as a detection signal. An amplifier circuit, and a modulation transmission circuit that modulates a detection signal output from the mixed amplification circuit with a carrier having a different frequency for each of the wireless electrodes and transmits the modulated signal. The receiver, a reception demodulation circuit that receives and demodulates the detection signal transmitted from the wireless electrode, a filter circuit that separates the detection signal output from the reception demodulation circuit into the biological signal and the reference signal Have.

In the biological signal measuring device according to the first aspect, the frequency of the reference signal is different for each of the wireless electrodes. According to a second aspect of the present invention, the reference signal has a constant voltage. According to the biological signal measuring device of the first aspect, the frequency of the reference signal differs for each wireless electrode, so that the frequency of the reference signal separated by the filter circuit indicates a specific wireless electrode. According to the biological signal measuring device of the second aspect, since the reference signal has a constant voltage, the ratio of the voltage value of the reference signal and the voltage of the biological signal separated by the filter circuit excludes the influence of the fluctuation of the amplification factor. It will be.

[0010]

FIG. 1 is a block diagram showing an embodiment of a biological signal measuring device according to the present invention. FIG.
FIG. 2 is an explanatory diagram showing a usage example of the biological signal measurement device in FIG. 1.
Hereinafter, description will be made based on these drawings.

The biological signal measuring device 10 of the present embodiment measures myoelectric potential, and is mounted on the skin of the subject M and includes four wireless electrodes 1 for wirelessly transmitting biological signals.
21 to 124, and four receivers 141 to 144 corresponding to the wireless electrodes 121 to 124, respectively.
Output signals of the receivers 141 to 144 are input to the analyzer 16. The analysis device 16 is, for example, a computer.

The wireless electrode 121 mixes and amplifies the detection electrodes 201 and 202 for inputting the biological signal S1 and a reference signal C1 of a frequency not included in the frequency band of the biological signal S1 into the biological signal S1 to obtain a detection signal D1. And a detection signal D output from the mixed amplification circuit 22.
And a modulation transmission circuit 24 that modulates and transmits the modulation signal 1 with a carrier FM1 having a different frequency for each of the wireless electrodes 121 to 124. The receiver 141 receives and demodulates the detection signal D1 transmitted from the wireless electrode 121.
And a filter circuit 2 for separating the detection signal D1 output from the reception demodulation circuit 26 into a biological signal S1 and a reference signal C1.
8 is provided.

The reference signal C1 is transmitted to the radio electrodes 121 to 124.
The frequency is different for each and is a constant voltage. The wireless electrodes 122 to 124 have the same configuration as the wireless electrode 121 except that the frequencies of the reference signals C2 to C4 (not shown) and the carrier waves FM2 to FM4 are different. Receiver 142-
144 is a receiver 141 except that the tuning frequency is different.
It has the same configuration as.

The detection electrodes 201 and 202 are arranged concentrically so that the myoelectric potential can be measured without considering the directivity. The mixed amplifier circuit 22 receives the reference signal C
1 and a amplifying circuit 32 that mixes and amplifies the reference signal C1 with the biological signal S1 and outputs it as a detection signal D1. The modulation transmission circuit 24 and the reception demodulation circuit 26 are, for example, general ones including an FM modulation IC and an FM demodulation IC. The filter circuit 28 includes a high-pass filter 281 that separates the reference signal C1 from the detection signal D1, and a low-pass filter 282 that separates the biological signal S1 from the detection signal D1.

FIG. 3 is a circuit diagram showing an example of a sine wave oscillation circuit and a mixed amplification circuit in the biological signal measuring device of FIG. FIG. 4 is a circuit diagram showing an amplifier in the mixed amplification circuit of FIG. FIG. 5 is a circuit diagram showing an equivalent circuit from the signal source to the amplifier in FIG. Hereinafter, description will be made based on these drawings. However, the same parts as those in FIG.

The mixing amplifier circuit 32 includes an amplifier 34 and a compensator 36. The power supply voltage Vcc is supplied from a battery (not shown) and is a single DC constant voltage. The compensator 36 includes an operational amplifier 361 and resistors 362 to 365. The compensator 36 divides the power supply voltage Vcc and outputs the divided voltage to the amplifier 34 as a reference voltage. In addition,
Although not shown, the power supply voltage Vcc is also supplied to the amplifier 34 and the operational amplifier 361.

The amplifier 34 has "IN" manufactured by Burr-Brown.
An IC named "A118" is used. A series circuit of a resistor 341 and a capacitor 342 is connected to this IC. With this series circuit, the detection electrodes 201,
A function of setting a gain when amplifying the myoelectric potential input from 202 and a function as a high-pass filter for removing noise contained in the myoelectric potential input from the detection electrodes 201 and 202 before amplification are realized. Have been.

The amplifier 34 includes a non-inverting amplifier 352 and a differential amplifier 353. The non-inverting amplifier 352 includes an external resistor 341 and a capacitor 34.
2. Operational amplifiers 343 and 344, resistors 345 and 346
And so on. The differential amplifier 353 includes resistors 347 to 350 and an operational amplifier 351. Here, the resistance value of the resistor 341 is R _G , the capacitance value of the capacitor 342 is C, the resistance values of the resistors 345 and 346 are R ₁ , the resistance values of the resistors 347 and 348 are R ₂ , and the resistors 349 and 350. Is R ₃ . Resistor 34
1 is for setting the gain, and if there is no capacitor 342, that is, if the capacitor is short-circuited, the gain G is G = 1 + 50 [kΩ].
/ _RG .

In this embodiment, since the capacitor 342 is connected to the resistor 341 in series, the gain G is given by the following equation. G = {(R _G + 2R ₁ ) jωC + 1} / (jωCR _G +1) · (R ₃ / R ₂ ) where R ₃ = R ₂ , R _G << R ₁ , ωCR >> 1 , Are given by: | G | = 1 + 2R ₁ / R _G (ω → ∞) At this time, the cutoff frequency f _C is given by the following equation. f _C = 1 / 2πCR _G ...

The compensator 36 supplies a power supply voltage Vcc (for example, 3
V), resistors 362 and 363, and a resistor 36
The reference voltage Vcc / 2 (for example, 1.5
V) to the amplifier 34, and an operational amplifier 361 as a voltage follower, and resistors 364 and 365 connected between the output terminal of the operational amplifier 361 and the ± input terminal of the amplifier 34, respectively. Operational amplifier 361
Are connected between the output terminal of the amplifier 34 and the ± input terminal of the amplifier 34, respectively, so that the voltage from the detection electrodes 201 and 202 to the ± input terminal of the amplifier 34 is connected via the resistors 364 and 365. The negative feedback to the operational amplifier 361 removes the myoelectric potential noise input from the detection electrodes 201 and 202. The noise removed includes
DC components and common mode noise are included.

The sine wave oscillating circuit 30 includes a signal source 301 for generating a sine wave which is a source of the reference signal C1, and a signal source 301.
And an amplitude attenuating circuit 302 for attenuating the sine wave generated in the step (a) to a predetermined amplitude. The signal source 301 is a general signal source such as a Wien bridge circuit, a quadrature chair circuit, and a crystal oscillation circuit. The amplitude attenuation circuit 302
It comprises a capacitor 311 and resistors 312 to 314.

Both input impedances of the ± input terminals of the amplifier 34 need to be equal in order to prevent noise from being mixed due to a decrease in CMRR (common-mode rejection ratio). Therefore, the resistors 364, 365, 312, 31
3,314, respectively, are r1, r2, r3, r
Assuming that r4 and r5 (where r5 >> r4), each resistance value is selected so as to satisfy the following relationship. r1 = {r2 × (r3 + r4)} / {r2 + (r3 + r4)}

If the output voltage value of the signal source 301 is E ₁ , the input voltage value E ₂ of the − input terminal of the amplifier 34 is
It is given by the following equation. E ₂ = [r2 / {(r4 // r5 + r3) + r2}] × {r4 + (r4 + r5)} × E _1.

Next, the operation of the biological signal measuring device 10 will be described with reference to FIGS.

First, the wireless electrode 121 will be described.
When the wireless electrode 121 is brought into close contact with the skin, a biological signal S1 consisting of a myoelectric potential generated by muscle activity is detected by the detection electrode 20.
1, 202. The input biological signal S1
Is mixed and amplified with the reference signal C1 by the mixing amplifier circuit 22 to become the detection signal D1. The detection signal D1 is transmitted from the modulation transmission circuit 24 to the receiver 141 by the carrier FM1, and is restored by the reception modulation circuit 26.

Here, assuming that the voltage and frequency of the biological signal S1 are Vs ₁ and Fs ₁ , respectively, the voltage and frequency of the reference signal C1 are Vc ₁ and Fc ₁ , and the amplification factor is α. α (Vs ₁ + Vc ₁ ) and the frequency component are (Fs ₁ , Fc ₁ ). Wireless electrodes 122-12
Similarly, the 4, the voltage and frequency of the biosignal S2~S4 respectively _{Vs 2 ~ Vs 4, Fs 2} ~ Fs 4,
The voltages and frequencies of the reference signals C2 to C4 are respectively set to Vc ₂
To Vc ₄ , Fc ₂ to Fc ₄ , the detection signal D 2
To D4 have voltages α (Vs ₂ + Vc ₂ ) to α, respectively.
(Vs ₄ + Vc ₄ ), and the frequency component is (Fs ₂ , Fc ₂ )
To (Fs ₄ , Fc ₄ ). The biological signals S1 to S4 are
Since it is a myoelectric potential, the voltage is on the order of mV and the frequency is 5 Hz
１1 kHz. For example, the voltages of the reference signals C1 to C4 are Vc ₁ to Vc ₄ = 10 mV, and the voltages of the reference signals C1 to C4 are
The frequency of No. 4 is Fc ₁ = 2.0 kHz, Fc ₂ = 2.5
kHz, Fc ₃ = 3.0 kHz, Fc ₄ = 3.5 kHz
It is.

In the filter circuit 28 of the receiver 141, the high-pass filter 281 and the low-pass filter 28
The cutoff frequency cf of 2 is Fsmax <cf <F, where Fcmin is the minimum frequency of the reference signals C1 to C4 and Fsmax is the maximum frequency of the biological signals S1 to S4.
cmin. Therefore, the voltage αVc ₁ and the frequency Fc ₁ are obtained from the high-pass filter 281, and the voltage αVs ₁ and the frequency Fs ₁ are obtained from the low-pass filter 282. Note that the cutoff frequency cf has the same value for the receivers 142 to 144.

Here, since the frequency Fc ₁ obtained by the high-pass filter 281 indicates the wireless electrode 121, it can be easily confirmed that the biological signal S 1 flying from the wireless electrode 121 is received. Also, the carrier FM of the wireless electrode 121
Other wireless electrode 122 to 1, ... carrier FM2, ... As long as the interference, other frequency Fc ₂ to the frequency Fc _1, since ... becomes the intermingled beat wave, interference can be easily determined.
.. Can be easily determined in the same manner even when interference occurs due to erroneous setting of the carrier frequency of the wireless electrodes 121,.

Further, the voltage ArufaVs ₁ obtained by the low-pass filter 282, a voltage ArufaVc ₁ obtained by the high-pass filter 281, a voltage Vc ₁ Tokyo known reference signal C1, the voltage Vs ₁ of the bio-signal S1, the following equation It is calculated by Vs ₁ = Vc ₁ × (αVs ₁ ) / (αVc ₁ ) As is clear from the equation, the voltage Vs ₁ is a value excluding the influence of the fluctuation of the amplification factor α.

[0030]

According to the biological signal measuring device of the present invention, since the frequency of the reference signal is different for each wireless electrode, the frequency of the reference signal separated by the filter circuit of the receiver causes any wireless electrode to fly. It is possible to easily confirm whether the received biological signal is received, and to easily determine interference with other wireless electrodes since the frequency of the reference signal becomes abnormal.

According to the biological signal measuring device of the second aspect, since the reference signal is a constant voltage, the ratio of the voltage value between the reference signal and the biological signal separated by the filter circuit is obtained, whereby the amplification factor can be determined. It is possible to obtain a high-precision biological signal excluding the influence of the fluctuation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a biological signal measuring device according to the present invention.

FIG. 2 is an explanatory diagram showing an example of use of the biological signal measuring device of FIG. 1;

FIG. 3 is a circuit diagram showing an example of a sine wave oscillation circuit and a mixed amplification circuit in the biological signal measurement device of FIG.

FIG. 4 is a circuit diagram illustrating an amplifier in the mixed amplification circuit of FIG. 3;

FIG. 5 is a circuit diagram showing an equivalent circuit from a signal source to an amplifier in FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 biological signal measuring device 22 mixing amplifier circuit 24 modulation transmission circuit 26 reception demodulation circuit 28 filter circuit 121 to 124 wireless electrode 141 to 144 receiver 201, 202 detection electrode C1 reference signal D1 detection signal S1 biological signal FM1 to FM4 carrier

Claims (2)

[Claims] A plurality of wireless electrodes that are attached to the skin and transmit a biological signal wirelessly, and a plurality of receivers corresponding to each of the wireless electrodes, wherein the wireless electrode inputs a biological signal; And a mixed amplifier circuit that mixes and amplifies a reference signal of a different frequency for each wireless electrode that is not included in the frequency band of the biological signal with a biological signal input from the detection electrode and outputs the amplified signal as a detection signal. And a modulation transmission circuit that modulates a detection signal output from the mixed amplification circuit with a carrier having a different frequency for each of the wireless electrodes and transmits the modulated signal. The receiver includes a detection signal transmitted from the wireless electrode. And a filter circuit for separating a detection signal output from the reception / demodulation circuit into the biological signal and the reference signal. Measuring device. 2. A wireless device comprising: a plurality of wireless electrodes mounted on the skin and transmitting a biological signal wirelessly; and a plurality of receivers corresponding to each of the wireless electrodes, wherein the wireless electrode inputs a biological signal. A mixing and amplification circuit that mixes and amplifies a reference signal having a frequency and a constant voltage that is not included in the frequency band of the biological signal with the biological signal input from the detection electrode and outputs the signal as a detection signal; A modulation transmission circuit that modulates and transmits a detection signal output from an amplification circuit with a carrier having a different frequency for each of the wireless electrodes, wherein the receiver receives and demodulates the detection signal transmitted from the wireless electrode. A biological signal measuring device, comprising: a receiving and demodulating circuit for performing the processing; and a filter circuit for separating a detection signal output from the receiving and demodulating circuit into the biological signal and the reference signal.