Biological signal processing device and biological signal processing program

Abstract

To acquire more accurate vital information from a reflection wave obtained by transmitting an electric wave to a living body.SOLUTION: In a biological signal processing device, vital signals in which a body motion component is removed are taken out by using the ratio of complex signals of two reflection waves by a reflection wave from a region R1 where the motion is large because it includes a vital component in a person to be measured (living body) 7 and a reflection wave from a region R2 where the motion is small because it does not include a vital component by a beamforming and a null beam of a reception signal using one radar module using an array antenna (23 and 25) as indicated in Fig. 1. As a method of the present invention for acquiring a reflection wave by designating a specific site such as the region R2 (shoulder) which does not include a vital component and whose motion is small, the reflection wave is multiplied by weighting information w1 and w2 obtained by beamforming beforehand.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a biological signal processing device and a biological signal processing program, and more particularly to a technique for analyzing vital information using, for example, a reflected wave of a radio wave transmitted to a living body. [Background technology]

[0002] Measuring vital information (biological signals) from living organisms is becoming increasingly important for understanding the health and psychological state of vehicle drivers, hospital patients, and everyday people, as well as for detecting signs of illness. In response to such demands, various technologies have been proposed for measuring vital information without contacting the subject, such as transmitting radio waves to the subject and using the Doppler shift (frequency transition) of the reflected waves to detect changes in distance to the subject.

[0003] However, measurement methods that use radio waves have the problem that noise caused by the subject's movements is included in the vital signs information. That is, while heartbeats cause fluctuations of about 0.5 mm on the body surface, when measuring a driver's vital signs using radar in a moving car, for example, body movements of 0.5 mm or more are included due to the driver's movements and vibrations while driving, making it impossible to accurately measure vital information. Patent Document 1 proposes a technique for eliminating the influence of such body movements. The technology described in Patent Document 1 extracts vital signs from the subject, with noise caused by body movements removed, from the difference between multiple distance information calculated using reflected waves of radio waves transmitted and directed toward multiple different areas of the subject.

[0004] However, in the technology described in Patent Document 1, various signal processes are performed on the reflected waves from the subject to obtain final distance information, and then vital signs are obtained from the difference in the distance information. A wide frequency band is required to obtain accurate distance information. When a wide band is not available or when narrowband CW (continuous wave) radar is used, it is difficult to obtain accurate distance information sufficient for vital sign detection, which requires a distance accuracy of 1 mm or less. As a result, errors that occur before the difference in distance information is calculated accumulate, reducing the accuracy of the calculated vital signs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7255748 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to obtain more accurate vital information from reflected waves obtained by transmitting radio waves to a living body. [Means for solving the problem]

[0007] The present invention provides a biological signal processing device comprising: a reflected wave acquiring means for acquiring reflected waves of radio waves transmitted toward a living body; a phase signal acquiring means for acquiring a first phase signal from a first region of the living body and a second phase signal from a second region different from the first region using the acquired reflected waves; a vital information acquiring means for acquiring vital information of the living body using a ratio between the acquired first phase signal and the acquired second phase signal; and an output means for outputting the acquired vital information. [Effects of the Invention]

[0008] According to the present invention, vital information of a living body is obtained using the ratio between the obtained first phase signal and second phase signal, and therefore an object of the present invention is to obtain more accurate vital information. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a biological signal processing device. [Figure 2] FIG. 2 is a diagram illustrating a hardware configuration of a signal processing device. [Figure 3] 10 is a flowchart illustrating a procedure for processing a biological signal. [Figure 4] FIG. 1 is an explanatory diagram conceptually showing the created radar cube. [Figure 5] FIG. 10 is an explanatory diagram showing the results of distance FFT for each channel. [Figure 6] FIG. 10 is an explanatory diagram showing IQ data constituting a distance bin for each channel on a two-dimensional complex plane. [Figure 7] FIG. 10 is an explanatory diagram conceptually showing the process of removing the body movement component. [Figure 8] FIG. 1 is an explanatory diagram in which IQ data R1, R2 and IQ′ data after removing the body motion component are plotted on a complex plane. [Figure 9] FIG. 10 is an explanatory diagram showing frequency characteristics of IQ data R1, R2 and IQ′ data after removing body movement components. [Figure 10] FIG. 10 is an explanatory diagram conceptually showing the heart rate waveform and heart rate extracted from the IQ′ data after removing the body movement component. [Figure 11] FIG. 10 is an explanatory diagram of an equation for determining weight information w. [Figure 12] FIG. 10 is an explanatory diagram showing a state in which a metal plate or the like is disposed on a seat belt of a driver's seat. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the biological signal processing device 1 and the biological signal processing program of the present invention will be described in detail with reference to FIGS. (1) Overview of the embodiment In the biological signal processing device 1 of this embodiment, as shown in FIG. 1, one radar module using array antennas (23, 25) is used, and by beamforming or null beam of the received signal, a reflected wave h(t)1 from region R1 of the subject (living body) 7, which contains vital signs and therefore has large movement, and a reflected wave h(t)2 from regions R2 and R3, which do not contain vital signs and therefore have small movement, are used to extract a vital signal from which the body movement component has been removed. In this embodiment, as a method for acquiring reflected waves by specifying specific areas such as area R2 (shoulder) or area R3 (flank) that do not include vital signs and have little movement, the reflected waves are acquired by multiplying the weight information w1 and w2 obtained in advance by beamforming.

[0011] (2) Details of the embodiment 1 is a diagram illustrating the configuration of a biological signal processing device 1 that measures biological signals (vital signs, vital signals) in this embodiment. In this embodiment, breathing, heart rate, pulse wave, etc. are measured as biological signals. In the embodiment described below, the biosignals are measured when the subject 7, seated in a chair, moves back and forth, as indicated by the arc-shaped arrow 60. However, the device can be widely used in a variety of situations, for example, by installing it in a vehicle to measure the driver's biosignals, by detecting the biosignals of users in a hospital or nursing home, by installing it on a home washbasin to detect the biosignals of someone washing their face, or by detecting the biosignals of someone sleeping in bed at home.

[0012] The biological signal processing device 1 is composed of a millimeter wave circuit 2, a control device 3, a signal processing device 4, and the like. The millimeter wave circuit 2 is a circuit that irradiates millimeter waves hf(t) toward the subject 7, receives reflected waves hv(t) from the subject 7, mixes the transmitted waves (millimeter waves) with the reflected waves, and outputs the result to the signal processing device 4. The millimeter-wave circuit 2 includes an oscillator 21, a phase-shifting division unit 24, mixers 26 and 27, a transmitting antenna 23, and a receiving antenna 25.

[0013] The control device 3 is a control device that controls the driving of the transmitter 21, and supplies power to the transmitter 21 and drives it to generate millimeter waves. The control device 3 of this embodiment controls the transmitter 21 to output a millimeter wave transmission wave (chirp) modulated by the FMCW (frequency continuous modulation) method so that the frequency increases linearly over time. It should be noted that control device 3 controls transmitter 21 so that it outputs millimeter waves with no directionality, rather than millimeter waves with directionality in the direction of a predetermined area of ​​person 7.

[0014] The transmitter 21 includes a millimeter wave transmission device and generates and transmits millimeter waves of a predetermined frequency. In this embodiment, the transmitter 21 transmits millimeter waves in the 60 GHz band, but it may also transmit millimeter waves in other frequency bands (for example, the 79 GHz band). Alternatively, a transmitter 21 that transmits microwaves (for example, the 24 GHz band) instead of millimeter waves may be used. In the biological signal processing device 1 of this embodiment, by using radio waves (millimeter waves) in the high frequency band, the reflected waves from the skin surface (body surface) of the subject 7 become dominant, and therefore phase fluctuations can be effectively observed as fluctuations on the body surface. The transmission wave (millimeter wave) generated by the oscillator 21 is distributed to the transmission antenna 23 and the distribution phase shift unit 24 via a transmission path.

[0015] The distribution phase shift unit 24 has a distribution function and a phase shift function (for example, it is configured by combining a distributor and a phase shifter), and divides the transmission wave into two waves using the reference wave as a reference wave, inputs one of the waves to the mixer 26 in phase with the reference wave, and inputs the other wave to the mixer 27 after shifting the phase by 90°. In this way, the distributing and phase shifting unit 24 generates a reference wave that is in phase with the millimeter wave output from the transmitting antenna 23 and a reference wave that is orthogonal in phase to the millimeter wave output from the transmitting antenna 23, and inputs these to the mixers 26 and 27, respectively.

[0016] Transmitting antenna 23 is configured as a two-element patch array antenna, and irradiates the millimeter waves generated by transmitter 21 toward subject 7 . Receiving antenna 25 is configured as a four-element patch array antenna, and receives the millimeter waves transmitted by transmitting antenna 23 and reflected from subject 7, distributes them, and sends them to mixers 26 and 27. In this way, the biological signal processing device 1 configures a total of eight virtual antennas by adopting the MIMO (Multiple Input Multiple Output) method, which transmits and receives using multiple antennas, but Figure 1 shows an antenna set for one of these channels.

[0017] As shown by the arc-shaped arrow 60, the body surface of the subject 7 moves back and forth due to bodily movements, causing large movements in the direction of the millimeter-wave circuit 2, and also small movements due to vital functions such as heartbeat and breathing, causing the reflected millimeter waves to undergo a Doppler shift. In this way, the reflected waves received by the receiving antenna 25 contain information on body movements and vital signs.

[0018] The mixer 26 mixes the reflected wave received by the receiving antenna 25 with the transmitted wave from the transmitter 21 to output an in-phase I(t) signal to the signal processing device 4. The mixer 27 mixes the reflected wave received by the receiving antenna 25 with a reference wave (transmitted wave) phase-shifted by 90°, and outputs an orthogonal Q(t) signal to the signal processing device 4.

[0019] The signal processing device 4 functions as a biosignal processing device as set forth in claim 1, and the biosignal processing device 1 shown in FIG. 1 functions as a biosignal processing device as set forth in claim 2. FIG. 2 is an explanatory diagram mainly showing the hardware configuration of the signal processing device 4. As shown in FIG. 2, the signal processing device 4 includes a CPU 41, a ROM 42, a RAM 43, an input / output unit 44, a storage device 45, and the like.

[0020] The CPU 41 executes various programs such as the biological signal processing program 451 of this embodiment, thereby performing various processes such as obtaining vital information from which body movement components have been removed, using the I(t) signal and Q(t) signal obtained from the millimeter wave circuit 2, thereby realizing various functions. The ROM 42 is a read-only memory that stores basic programs and parameters that the CPU 41 uses to operate the signal processing device 4. The RAM 43 is used as a working area when the CPU 41 performs biological signal processing, and in this embodiment, IF data (IF raw data) 431, radar cube 432, phase signal 433, vital information 434, and various other data are temporarily stored.

[0021] In the IF data 431, the I(t) signal and Q(t) signal output from the millimeter wave circuit 2 are stored. The transmitting antenna 23 successively transmits frequency-modulated millimeter waves, and n I(t) signals and Q(t) signals are sampled for each transmission unit (chirp set) and stored for each mch (channel). Therefore, for each chirp set, m×n I(t) signals and Q(t) signals are stored in the IF data 431. In this embodiment, the number of samples n per chirp set stored in the IF data 431 is 256, but it can be less (for example, 128) or more (for example, 512). Here, a chirp set is made up of two chirps, which matches the number of transmitting antennas 23 (two). On the other hand, the number of channels m is 8 (2 transmissions x 4 receptions), but it is also possible to set it to (f transmissions x v receptions) channels, for example, (3 transmissions x 4 receptions) = 12 channels.

[0022] In the radar cube 432, IQ data consisting of I(t) and Q(t) stored in the IF data 431 is generated for each channel, sampling, and chirp set and stored. The IQ data is a complex signal generated from both signals I(t) and Q(t) according to equation 22 (h(t) = I(t) + jQ(t)) shown in Figure 1, where j is the imaginary unit and t represents time. The radar cube 432, which will be described in detail later, forms a virtual cube by arranging the IQ data in the sampling direction within each chirp set (hereinafter referred to as the distance direction), the virtual array antenna direction (hereinafter referred to as the channel direction), and the chirp set number direction (hereinafter referred to as the time direction) (see Figure 4).

[0023] The phase signal 433 stores a first phase signal from the first region R1 (see FIG. 1) and a second phase signal from the second region R2. The first phase signal and the second phase signal are calculated by multiplying the IQ data for each channel obtained by distance FFT analysis of the radar cube 432 by predetermined weight information w1 and w2, and are stored in the phase signal 433. Here, the weight information w1 and w2 is expressed by a Hermitian matrix a{H} of the steering vector a, which will be described later.

[0024] Vital information 434 stores vital information obtained by finally removing the body movement component from the first phase signal and second phase signal stored in phase signal 433. Other data stored in the RAM 43 include an average radar cube formed from average IQ data, distance bin data, etc., which will be described in detail later.

[0025] The input / output unit 44 includes an input unit and an output unit. The input unit includes input devices such as a touch panel, a keyboard, and a mouse, and is a device for accepting operations from the user of the signal processing device 4. The output unit includes output devices such as a display, a speaker, and a printer, and displays the operation screen of the signal processing device 4 on the display and outputs analyzed biosignals (vital information) to these output devices.

[0026] The storage device 45 is composed of a readable / writable storage medium and a drive device for reading and writing various information such as programs and data from and to the storage medium. The storage media used in this storage device 45 are mainly semiconductor storage devices such as hard disks and SSDs (Solid State Drives), but external storage media such as semiconductor storage media such as memory chips and IC cards, and storage media from which information can be optically read, such as CD-ROMs, MOs, and PDs (phase change rewritable optical disks), may also be used. The storage device 45 stores, for example, a biological signal processing program 451, weight information 452, vital information 453, and other programs and data.

[0027] The biological signal processing program 451 is a program for extracting biological signals such as pulse waves from the I(t) signal and Q(t) signal output from the millimeter wave circuit 2. The weight information 452 is weight information that extracts phase signals from predetermined regions R1 and R2 in the subject 7 by multiplying it by the reflected wave from the subject 7, and weight information w1 corresponding to region R1 and weight information w2 corresponding to region R2 are stored in advance. The vital information 453 is data that is obtained by reading the vital information 434 obtained by the biological signal processing program 451 from the RAM 43 and saving it in the storage device 45 together with information such as the processing date and time and the subject.

[0028] Next, the biological signal processing performed by the biological signal processing device 1 to obtain a biological signal (vital information) from the subject 7 will be described. FIG. 3 is a flowchart showing the procedure of the biological signal processing performed by the signal processing device 4. The CPU 41 executes the biological signal processing program 451 stored in the storage device 45 to perform the biological signal processing. As a prerequisite for carrying out the biological signal processing, it is assumed that millimeter waves are output from the millimeter wave circuit 2 to the subject 7 as shown in FIG.

[0029] The CPU 41 acquires the data necessary for analysis (step 10). That is, for each chirp set, the CPU 41 acquires n (=256) I(t) signals and Q(t) signals output from the mixers 26 and 27 of the millimeter-wave circuit 2 for each channel (ch1 to ch8) and stores them sequentially in the IF data 431 of the RAM 43. Here, 256 x 8 I(t) signals and Q(t) signals are stored per chirp set.

[0030] Next, the CPU 41 creates a radar cube (step 12). Figure 4 shows a conceptual representation of the radar cube we created. The radar cube 432 forms a virtual cube in which IQ data are arranged in the distance direction (= 256 sampling points), the channel direction (= 8 channels), and the time direction (e.g., 90,000 sets) within each chirp set.

[0031] The CPU 41 creates one IQ data from a pair of I(t) and Q(t) signals from one sample in one channel stored in the IF data 431 using h(t) = I(t) + jQ(t) in equation 22 shown in Figure 1. Then, for one chirp set, the CPU 41 creates IQ data of m (=8) total channels x n (=256) number of samples in the chirp set. The CPU 41 sequentially creates IQ data for each chirp set that is sequentially output from the millimeter wave circuit 2 and stored in the IF data 431 , and stores the data in the radar cube 432 . By sequentially creating IQ data for each chirp set and storing it in the radar cube 432, p (e.g., 90,000) pieces of n×m IQ data shown in Figure 4 are created in the time direction (downward on the vertical axis of the drawing).

[0032] Next, the CPU 41 performs frame averaging of the radar cube 432 created in step 12 (step 14). The CPU 41 defines a group of m channels x n samplings x s chirp set numbers as one frame in the radar cube 432 shown in FIG. Then, the CPU 41 averages the s number of IQ data aligned in the time direction, and stores the average radar cube, which is a single average IQ data, in the RAM 43. As a result, the radar cube 432 shown in FIG. 4 becomes q / s frames in the time direction (vertical direction). By averaging s pieces of IQ data aligned in the time direction in one frame to obtain average IQ data, it is possible to reduce noise in each average IQ data (IQ data).

[0033] Here, the number s of chirp sets constituting one frame is set to 15 in this embodiment, but it can be set to more or less than 15. For example, s may be set to 1. In this case, the average IQ data is equal to the IQ data, and the processing time can be shortened.

[0034] In the following explanation, for the sake of convenience of the drawings used for the explanation, the case of s=1 will be explained. However, if s>1, the IQ data in each process in the following explanation can be replaced with average IQ data.

[0035] Next, the CPU 41 determines the distance bin (step 16). That is, the CPU 41 applies a distance FFT (Fast Fourier Transform) to each frame of the radar cube 432 in FIG. 4 for each channel (ch1 to ch8) in the distance direction (sampling direction) to convert it into distance.

[0036] FIG. 5 shows the results (peak index) of the distance FFT for each channel (ch1 to ch8). As shown in the index (bottom row) of the peak position in Fig. 5(c), the peak index value in the unmanned space is T = 3, so non-existent targets are removed by removing the index value T = 3 in Fig. 5(a) and (b). Specifically, the CPU 41 removes clutter components from around the subject 7 by subtracting the average of the IQ data that has undergone distance FFT in the time direction as a DC component.

[0037] Next, for each frame (each row in the distance direction × channel direction in Figure 4), the CPU 41 sequentially identifies the IQ data with the largest distance value (peak value) from n pieces of IQ data in the distance direction (= 256 pieces) for each of channels 1 to 8, thereby determining the overall distance bin. In Figure 4, for channel 1 (ch1) in the first chirp set, by applying a distance FFT to n IQ data in the distance direction (to the right in the drawing), the IQ data that takes the peak value in distance (for example, IQ data 38 shown in shaded area) is identified as the optimal IQ data. As a result, m pieces of IQ data are identified per frame, and distance bins consisting of a total of m×q pieces of IQ data are determined.

[0038] Next, the CPU 41 acquires IQ data for each antenna (channel) from the determined distance bin (step 18). The acquired IQ data is IQ data after applying the distance FFT. Figure 6 shows the IQ data that make up the distance bins for each channel plotted on a two-dimensional complex plane. As an example, Figure 6 plots the IQ data for 6000 chirp sets for each channel. As shown in FIG. 6, the IQ data of each channel, when plotted on a two-dimensional complex plane, follows a periodic, approximately concentric locus in synchronization with the body movements and vital signs of the subject 7. The reason for the concentric circular trajectories is that the radio waves irradiated to the subject 7 are millimeter waves with a very high frequency; in the case of microwaves, which have a lower frequency than millimeter waves, the trajectories will be concentric arcs.

[0039] Next, the CPU 41 acquires the IQ data R1 and IQ data R2 for each area (step 20). That is, the CPU 41 uses the IQ data acquired in step 18 and the weight information w1 and w2 stored in the weight information 452 of the storage device 45 to obtain the IQ data R1 and IQ data R2 corresponding to the regions R1 and R2. Specifically, the CPU 41 converts the IQ data of m channels (1ch to 8ch) into a vector as elements, and multiplies this by weight information w1 and w2 expressed as a Hermitian matrix to obtain IQ data R1 and IQ data R2 corresponding to regions R1 and R2 of the subject 7. The IQ data R1 and IQ data R2 acquired here are complex signals expressed by the equation h(t) = I(t) + jQ(t), similar to equation 22 (see Figure 1), and function as a first phase signal from a first region in the living body and a second phase signal from a second region. That is, the IQ data Rn is a complex signal and functions as an nth phase signal from an nth region.

[0040] Next, the CPU 41 acquires the IQ' data after removing the body movement component (step 22). That is, the CPU 41 obtains the IQ' data after removing the body movement component by calculating (IQ data R1) / (IQ data R2), which is the ratio of the IQ data R1 from the region R1 to the IQ data R2 from the region R2. Here, the process of removing the body motion component will be explained. If the IQ data R1 and IQ data R2 contain reflection components from fixed objects such as walls and chairs, the center of the IQ data for each channel shown in Figure 6 will shift from the correct origin O to the virtual origin O', resulting in a signal error. Therefore, the CPU 41 removes the body movement component from the ratio between the IQ data R1 and the IQ data R2 after the origin position correction.

[0041] Figure 7 conceptually illustrates the process of removing the body movement component. In FIG. 7, the process of origin correction and body movement component removal will be explained using microwaves as an example, which is easier to illustrate the processing process than using millimeter waves as shown in FIG. 6, but the principle is the same. In addition, in Figure 7, the IQ data R1 from region R1 is represented by S1, and the IQ data R2 from region R2 is represented by S2, which are expressed by equation 22 h(t) = I(t) + jQ(t) on a complex plane with real axis I and imaginary axis Q.

[0042] The distance between the origin O and the virtual origin O' is represented by offsets C1 and C2, the vital component contained in the IQ data is represented by exp{jθv}, and the body movement component contained in the signal is represented by exp{jθm}. Then, IQ data R1 from a region with a large vital component (region R1 onto which the heart is projected in this embodiment), represented by arc 61 in FIG. 7(a), is expressed as S1=C1+exp{j(θv+θm)}. On the other hand, IQ data R2 from a region with a small vital component (region R2 onto which the shoulders are projected in this embodiment) represented by arc 62 is expressed as S2=C2+exp{jθm}. The offsets C1 and C2 are determined by finding the center point (virtual origin) O' of the loci of the arcs 61 and 62 and calculating the distance from this virtual origin O' to the origin O of the complex plane.

[0043] As shown in FIG. 7(b), the CPU 41 obtains exp{jθv} by calculating the ratio between (S1-C1) in the area R1 and (S2-C2) in the area R2, from which the error components due to the reflection components from fixed objects have been removed. That is, the CPU 41 can obtain exp{jθv}, which is IQ′ data of only vital components that do not contain body movement components, as shown by an arc 63 in FIG. 7(b), using the following equation A. (S1-C1) / (S2-C2)=exp{j(θv+θm-θm)}=exp{jθv}…A

[0044] Figure 8 shows the IQ data R1 and R2 (after removing offsets C1 and C2; same as in Figure 9) of regions R1 and R2 plotted on the complex plane, along with the IQ' data after removing the body motion component. Note that the IQ data R1 and R2 are based on the data after removing offsets C1 and C2. FIG. 9 shows the frequency characteristics of the IQ data R1 and R2 and the IQ' data after removing the body movement component. Figures 8 and 9 show laboratory measurement data, measured while a subject 7 was seated at a distance of 0.5 m from the millimeter-wave circuit 2 and was periodically moving back and forth (body movement frequency 0.5 Hz) within a body movement displacement range of 2.0 cm.

[0045] As shown in FIGS. 9(a) and 9(b), the IQ data R1 and R2 have a peak value of the amplitude spectrum at a frequency of 0.5 Hz, which is the body movement period of the subject 7. On the other hand, as shown in the above-mentioned formula A, the peak value at a frequency of 0.5 Hz is excluded from the IQ' data obtained from the ratio of the IQ data R1 and the IQ data R2, as shown in FIG. 9(c). In this way, by calculating the ratio between the IQ data R1 and the IQ data R2, the body movement component of the person being measured 7 can be removed. In practice, it is possible to remove not only the body movement components of the subject 7 but also noise commonly contained in the IQ data R1 and IQ data R2, thereby obtaining more accurate IQ' data.

[0046] Next, the CPU 41 acquires vital information (step 24). That is, the CPU 41 extracts, for example, the heart rate as a vital signal (biological signal) from the IQ' data (exp{jθv}) after removing the body movement component in step 22 by using various well-known processing methods, for example, by applying a band-pass filter. As a well-known processing method, for example, a bandpass filter of FIR bandpass (Kaiser window) type, with a passband of 0.5 Hz to 2.0 Hz and an order of 600 is applied to the IQ′ data to extract the heartbeat.

[0047] Figure 10 conceptually shows the heart rate waveform and heart rate extracted from the IQ' data after removing the body movement component. FIG. 10(a) conceptually shows the heart rate waveform after filtering. The CPU 41 obtains each peak of this heart rate waveform and obtains the corresponding heart rate from the time between adjacent peaks, thereby acquiring vital information (heart rate), and stores the obtained vital information in the vital information 434 of the RAM 43. FIG. 10(b) shows the calculated heart rate.

[0048] The CPU 41 functions as an output means for outputting the acquired vital information by performing at least one of the following: adding measurement information such as information about the subject 7 and the date of measurement to the vital information 434 stored in the RAM 43 and outputting it to the vital information 453 in the storage device 45; displaying it on the display of the input / output unit 44; and providing it to the outside via a communication unit (not shown in Figure 2). Since the region R1 is the region onto which the heart is projected, it contains not only the heartbeat component but also the respiratory component, so the CPU 41 can separate the respiratory waveform from the IQ' data after removing the body movement component and calculate the respiratory rate.

[0049] Next, weight information w1 and w2 for obtaining IQ data R1 and IQ data R2 corresponding to regions R1 and R2 from the IQ data obtained in step 18 will be described. The weight information 452 (weight information w1, w2) stored in the memory device 45 used in the embodiment is based on the assumption that the measurement location and the posture of the subject 7 are fixed, such as the driver of a vehicle, a passenger, or a patient at a specified examination position (hereinafter referred to as a specific measurement location). By having the subject 7 present at a specific measurement location determined in this manner, it is possible to identify the locations of the region R1 with large movement (body movement + vital signs) and the regions R2 and R3 with small movement (body movement only) as general regions that are not dependent on the subject 7.

[0050] In the biological signal processing device 1, before performing measurements on a specific subject 7, weight information w1, w2 for areas R1, R2, etc. of the experimental subject 7 is calculated for each specific measurement location and stored in weight information 452 of the memory device 45. When actually measuring the subject 7, the CPU 41 uses the weight information w corresponding to the specific measurement location input from the input / output unit 44. Furthermore, if the specific measurement location (driver's seat) is determined in accordance with the location where the millimeter-wave circuit 2 is installed, only the weight information w1 and w2 corresponding to the specific measurement location is stored in the storage device 45, and the CPU 41 uses the stored weight information w1 and w2.

[0051] FIG. 11 shows a mathematical formula for determining the weight information w. The weight information w(w1, w2) stored in advance will be described with reference to the equations in FIG. The weight information w1 and w2 is obtained by beamforming to the subject 7 present at a specific measurement location. That is, the differences d1 to d8 in the propagation path length between the millimeter wave propagation path length from the body part (regions R1 and R2) of the subject 7 to be beamformed to each element (2 transmit x 4 receive = 8 elements) and the propagation path length to the reference element are calculated. Then, the steering vector "a" ("a1" and "a2") shown in FIG. 11(a) is created. Here, the notation "a" in "" represents a vector.

[0052] Then, from the created steering vector, weight information w(w1, w2) for region R1 shown in FIG. 11(b) is created. In FIG. 11(b), weight information w(w1, w2) is the Hermitian matrix a{H} of the steering vector a(a1, a2). The created weight information w1 and w2 is stored in the storage device 45. In the millimeter-wave circuit 2 described in this embodiment, an array antenna with (transmission 2 × reception 4) = 8 channels has been described, so the dimension of the steering vector is 8. However, when an array antenna with (transmission f × reception v) channels is used, the dimension of the steering vector is (f × v).

[0053] As described above, the biological signal processing device 1 of this embodiment acquires phase data (IQ data R1) of region R1 of the subject's body, which contains vital components and thus exhibits large phase fluctuations, and phase data (IQ data R2) of region R2, which does not contain vital components and therefore exhibits small phase fluctuations.The acquired IQ data R1 and IQ data R2 are then used to remove body movement components based on the ratio of both phase data (IQ data R1 / IQ data R2). Therefore, according to the biosignal processing of this embodiment, compared to when distance information is calculated from each of the IQ data R1 and IQ data R2 and then the body movement components are removed by taking the difference between the two distance information, the body movement components are removed using data that is less processed and closer to the raw data, so more accurate vital information can be obtained. Furthermore, in the biological signal processing device 1 of this embodiment, even if the frequency band cannot be obtained or the distance to the biological body cannot be detected with high accuracy by using a narrow-band CW radar, the body movement component is removed using the phase data ratio (IQ data R1 / IQ data R2), so highly accurate vital information can be obtained.

[0054] The above describes one embodiment of the biological signal processing device 1 of the present invention, but the present invention is not limited to the described embodiment, and it is possible to make modifications within the scope described in each claim and the scope described in the embodiment, as well as further modifications to other modifications. For example, in the described embodiment, the case where the IQ data of the complex signal acquired using the transmitted millimeter wave hf(t) and the reflected wave hv(t) is multiplied by weight information w1 and w2 is described to acquire the reflected wave IQ data R1 from region R1 (heart area) and the reflected wave IQ data R2 from region 2 (shoulder). In this embodiment, the weight information w1 and w2 used to calculate the IQ data R1 and IQ data R2 are obtained in advance by beamforming to the subject 7 at a specific measurement location, and in actual measurement, the weight information w1 and w2 defined corresponding to the specific measurement location are read out from the storage device 45 and used.

[0055] Alternatively, the weight information w1 and w2 may be calculated each time an actual measurement is performed on the subject 7. In this case, the CPU 41 uses the IQ data for each antenna acquired in step 18 to calculate the propagation path length differences d1 to d8 from the areas R1 and R2 to be beamformed, and creates steering vectors a1 and a2 and weight information w1 and w2 using a Hermitian matrix. The CPU 41 may then store the created weight information w1 and w2 in the RAM 43 and use it continuously while measurements are being taken of the subject 7, or may calculate the weight information w1 and w2 every predetermined number of frames (for example, every 100 frames).

[0056] In addition, in the embodiments and variants described above, the weight information w1 and w2 are calculated by beamforming, but it is also possible to use a weight w corresponding to a null beam that does not specify a specific area and extracts signals (IQ data) targeting areas other than R1 where there are no vital signals. Furthermore, the weight information w1 and w2 may be obtained by capturing an image of a subject such as a driver in a vehicle and analyzing the image to identify the regions R1 and R2.

[0057] Furthermore, in the embodiment and modified examples described above, the case where millimeter waves are transmitted to the person under measurement 7 who is not wearing any special device or object has been described. However, in situations where it is not possible to separate the reflected wave IQ data R2 from the region R2 that does not contain vital components, it is possible to make it easier to separate the IQ data R2 by placing a metal plate in a location that moves in the same way as the body, such as part of the seat belt in the case of a driver in a vehicle. Furthermore, the metal plate may be attached to the shoulder (R2), flank (R3) or other part of the subject's clothing, other than the seat belt.

[0058] Alternatively, instead of the metal plate, a backscatter may be attached to the seat belt and worn by the person 7 to be measured. The backscatter is a device that has a phase modulation function for the reflected wave and modulates the reflected millimeter wave using a subcarrier signal that turns on and off quickly and randomly (the backscatter subcarrier signal is carried on the reflected wave). By carrying a high-frequency subcarrier signal on the reflected wave from the backscatterer placed on the subject 7, it is possible to easily separate the reflected wave IQ data R2 from the region R2 that does not contain vital components.

[0059] 12 shows a state in which a metal plate (or backscatter) is provided on the seat belt of the driver's seat. Note that FIG. 12 corresponds to FIG. As shown in FIG. 12, in the above-described modified example, a metal plate 66 or a backscatter 67 (hereinafter simply referred to as the metal plate 66, etc.) is provided on the seat belt 56 for the driver's seat. The metal plate 66 and the like are disposed on the outer surface of the seat belt 56 (the surface on the millimeter wave circuit 2 side) or inside the seat belt 56 formed in a bag shape. FIG. 12 shows a case where the metal plate 66 or the like is placed in the shoulder region R2, which does not contain vital components, of the subject 7 while the subject 7 is fastened with the seat belt 65, but it may also be placed in the flank region R3, which does not contain vital components. It is also possible to acquire vital sign information by outputting millimeter waves toward the passenger in the front passenger seat, with the passenger being the subject 7. In this case, the seat belt of the passenger in the front passenger seat will be fastened in the opposite direction (from upper left to lower right) to that in FIG. 12, so it is preferable to arrange the metal plate 66 etc. in a position corresponding to the region R3 of the flank.

[0060] In the embodiment and modified examples described above, the case where noise removal processing is performed before the body movement component removal processing (step 22) is performed has been described. On the other hand, these noises can also be removed by processing to remove body movement components by calculating the ratio of frequency components (IQ data R1 / IQ data R2), so it is possible to omit the prior noise removal processing. Here, the noise removal processes that can be omitted include the following (a) to (c), and it is possible to omit any one or more of these. (a) In step 14, s pieces of IQ data arranged in the time direction of multiple frames are averaged to obtain average IQ data. (b) In step 16, the process of removing clutter components from around the subject 7 by subtracting the average of the distance FFT-processed IQ data extending in the time direction as a DC component. (c) In step 22, the process of returning the virtual origin O' of the IQ data R1 and R2 to the origin O by calculating (S1-C1) and (S2-C2), which was performed immediately before removing the body movement component from the ratio of the phase components.

[0061] In addition, in the described embodiments and variants, the left chest is used as the area where the heart is projected, which is the area R1 that has large movement because it contains vital signs, but the area R4 where the abdomen is projected may also be used as the area where vital signs have large movement to acquire vital signals. In this case, IQ'' data containing only vital components, excluding body movement components, may be obtained from the ratio of IQ data R4 to IQ data R2, or the ratio of IQ data R4 to IQ data R3, corresponding to region R4 onto which the abdomen is projected and region R2 or R3 onto which the shoulders or flanks are projected. In the case of the region R1 onto which the heart is projected, the IQ' data after removing the body movement component contains a respiratory component and a heartbeat component, so that either or both of them can be extracted. In contrast, only the respiratory component is extracted from the IQ'' data obtained for region R4, where the abdomen is projected instead of region R1. In this case, the respiratory component can be extracted with high accuracy because the heart rate component is not included.

[0062] In addition, in the embodiments and variants, the region R2 including the shoulders and the region R3 including the flanks have been described as regions that do not contain vital components and therefore have little movement, but regions including other parts, for example, a relatively narrow region including the clavicle position, may also be targeted.

[0063] Furthermore, in the embodiment and modified examples described above, the MIMO system and the FMCW (Frequency Continuous Modulation Waveform) system are used, but the present invention is not limited to these and other systems that can be substituted as appropriate may be adopted. For example, instead of the FMCW method, a CW (continuous wave) method that outputs a continuous wave with constant amplitude and frequency can be adopted. In the case of this CW method, IQ data R1 and IQ data R2 corresponding to regions R1 and R2 are obtained from two-dimensional IQ data in the virtual array antenna direction (channel direction) m and the time direction p, rather than the radar cube 432 described in Fig. 4.

[0064] In the described embodiments and variants, the transmitted waves are not given directionality such as by beamforming, and non-directional millimeter waves are transmitted from the transmitting antenna 23, and beamforming or the like is performed on the reflected waves received by the receiving antenna 25. In response to this, the control device 3 may transmit a directional millimeter wave from the transmitting antenna 23. That is, the control device 3 may control the phase of the millimeter wave transmitted from the transmitting antenna 23 so that the millimeter wave has directivity in the directions of the regions R1, R2, and R3.

[0065] In the embodiment and modified examples, the case where IQ' data not including body movement components is calculated from the chirp set number q=90000 (q / s=6000 frames) has been described, including the purpose of obtaining data for verification. Alternatively, IQ' data (exp{jθv}) containing only vital components and not including body movement components according to the above formula A may be calculated every u frames (4≦u≦20), for example, every 5 frames, or preferably every 6 frames. This allows IQ' data to be obtained promptly (for each transmission and reception of a chirp set for six frames) after starting measurement. Furthermore, instead of calculating IQ' data for every u frames, after receiving the first u frames, IQ' data is calculated using the total u frames of the most recent frame and the previous frame (u-1), allowing new IQ' data and new vital information to be obtained for each frame after the u frames.

[0066] In the embodiment and modified examples described above, the case where IQ data R1 for region R1 and IQ data R2 for region R2 are obtained by multiplying the IQ data obtained from the millimeter wave circuit 2 by weight information w1 and w2 has been described. In other words, the case where beamforming is performed on received reflected waves, rather than beamforming on transmitted waves, has been described. In contrast to this, beamforming of the transmitted waves (millimeter waves) from each transmitting antenna 23 may be performed so that the millimeter waves are irradiated onto the regions R1 and R2.

[0067] In the embodiment and modified examples described above, the case where a phase signal is acquired using the IQ data acquired from the millimeter wave circuit 2 has been described. That is, a case has been described in which complex signals consisting of an in-phase signal I and a quadrature signal Q, which are made up of radio waves transmitted by a transmitting antenna and reflected waves received by a receiving antenna, are acquired as the first phase signal and the second phase signal. On the other hand, the first phase signal and the second phase signal may be complex signals consisting of only an in-phase signal I or a quadrature signal Q. Even in this case, by applying a range FFT to a radar cube formed from an in-phase signal I or a quadrature signal Q, a complex number containing phase information can be obtained. Therefore, even when the CPU 41 acquires only the in-phase signal I or the quadrature signal Q, it can obtain a vital signal using the same processing procedure as the biological signal processing described with reference to FIG.

[0068] Furthermore, in the described embodiments and variants, biosignal processing is performed using millimeter waves, but other radio waves, such as microwaves and submillimeter waves (decimeter waves), may also be used. In this case, the transmitter 21 is made to emit microwaves or submillimeter waves.

[0069] (Configuration 1) a reflected wave acquiring means for acquiring a reflected wave of a radio wave transmitted to a living body; a phase signal acquiring means for acquiring a first phase signal from a first region in the living body and a second phase signal from a second region different from the first region, using the acquired reflected wave; a vital information acquiring means for acquiring vital information of the living body using a ratio between the acquired first phase signal and the acquired second phase signal; an output means for outputting the acquired vital information; A biological signal processing device comprising: (Configuration 2) a transmitting antenna for transmitting microwaves, millimeter waves, or submillimeter waves toward the living body; a receiving antenna for receiving a reflected wave of the radio wave transmitted from the transmitting antenna, the phase signal acquisition means acquires the first phase signal and the second phase signal from the reflected wave received by the receiving antenna. 2. The biological signal processing device according to configuration 1, (Configuration 3) the phase signal acquisition means acquires, as the first phase signal and the second phase signal, a complex signal consisting of at least one of an in-phase signal I and a quadrature signal Q from the radio wave transmitted by the transmitting antenna and the reflected wave received by the receiving antenna; 3. The biological signal processing device according to configuration 1 or 2. (Configuration 4) the phase signal acquiring means defines a region in which a phase fluctuation due to a vital sign of the living body is larger than that in the second region as the first region; 4. The biological signal processing device according to configuration 1, 2, or 3, (Configuration 5) the phase signal acquiring means defines a region onto which the heart or abdomen of the living body is projected as the first region, and a region onto which the shoulder or flank of the living body is projected as the second region; 4. The biological signal processing device according to configuration 1, 2, or 3, (Configuration 6) At least one of the transmitting antenna and the receiving antenna comprises a plurality of antennas; 6. The biological signal processing device according to any one of configurations 1 to 5, wherein: (Configuration 7) the phase signal acquisition means multiplies the acquired complex signal by a weight w corresponding to the first region and the second region to acquire a first phase signal and a second phase signal; 7. The biological signal processing device according to any one of configurations 1 to 6, wherein: (Configuration 8) the phase signal acquiring means acquires a first phase signal from a first region of the living body using a first weighting for the acquired reflected wave, and acquires a second phase signal from a second region of the living body using a second weighting; 7. The biological signal processing device according to any one of configurations 1 to 6, wherein: (Configuration 9) a weight determining means for determining the first weight and the second weight before or after the reflected wave is acquired by the reflected wave acquiring means, the phase signal acquisition means uses the first weight and the second weight determined by the weight determination means; 9. The biological signal processing device according to configuration 8. (Configuration 10) the weight determining means determines the first region and the second region by beamforming or null beam for the reflected wave, or by image processing of an image of the living body. 10. The biological signal processing device according to configuration 9. (Configuration 11) The transmitting antenna transmits radio waves using a continuous frequency modulation method. 11. The biological signal processing device according to any one of configurations 2 to 10, wherein: (Configuration 12) the phase signal acquiring means acquires a second phase signal using a metal plate placed on the living body or a placement area including backscatter as a second reflection area. 12. The biological signal processing device according to any one of configurations 1 to 11, (Configuration 13) A reflected wave acquisition function that acquires reflected waves of radio waves transmitted toward the living body; a phase signal acquisition function that acquires a first phase signal from a first region in the living body and a second phase signal from a second region different from the first region using the acquired reflected wave; a vital information acquisition function that acquires vital information of the living body using a ratio between the acquired first phase signal and the acquired second phase signal; an output function for outputting the acquired vital information; A biological signal processing program characterized by causing a computer to realize the above. [Explanation of symbols]

[0070] 1. Biosignal processing device 2 Millimeter-wave circuits 3. Control device 4. Signal Processing Device 7 Person to be measured 21 Transmitter 23 Transmitting Antenna 24 Distribution phase shift section 25 receiving antenna 26, 27 mixer 41 CPU 43 RAM 431 IF data 432 Radar Cube 433 phase signal 434 Vital Signs 44 Input / output section 45 Storage device 451 Biosignal Processing Program 452 Weight Information 453 Vital Information 60 Arrow 61 Arc (IQ data R1) 62 Arc (IQ data R2) R1, R2, R3 area

Claims

1. a reflected wave acquiring means for acquiring a reflected wave of a radio wave transmitted to a living body; a phase signal acquiring means for acquiring a first phase signal from a first region in the living body and a second phase signal from a second region different from the first region, using the acquired reflected wave; a vital information acquiring means for acquiring vital information of the living body using a ratio between the acquired first phase signal and the acquired second phase signal; an output means for outputting the acquired vital information; A biological signal processing device comprising:

2. a transmitting antenna for transmitting microwaves, millimeter waves, or submillimeter waves toward the living body; a receiving antenna for receiving a reflected wave of the radio wave transmitted from the transmitting antenna, the phase signal acquisition means acquires the first phase signal and the second phase signal from the reflected wave received by the receiving antenna. The biological signal processing device according to claim 1 .

3. the phase signal acquiring means acquires, as the first phase signal and the second phase signal, a complex signal consisting of at least one of an in-phase signal I and a quadrature signal Q from the radio wave transmitted by the transmitting antenna and the reflected wave received by the receiving antenna; 3. The biological signal processing device according to claim 2.

4. the phase signal acquiring means defines a region in which a phase fluctuation due to a vital sign of the living body is larger than that in the second region as the first region; The biological signal processing device according to claim 1 .

5. the phase signal acquiring means defines a region onto which the heart or abdomen of the living body is projected as the first region, and a region onto which the shoulder or flank of the living body is projected as the second region; The biological signal processing device according to claim 1 .

6. At least one of the transmitting antenna and the receiving antenna comprises a plurality of antennas; 3. The biological signal processing device according to claim 2.

7. the phase signal acquiring means acquires a first phase signal and a second phase signal by multiplying the acquired complex signal by a weight w corresponding to the first region and the second region.

7. The biological signal processing device according to claim 6.

8. the phase signal acquiring means acquires a first phase signal from a first region of the living body using a first weight for the acquired reflected wave, and acquires a second phase signal from a second region of the living body using a second weight for the acquired reflected wave; 7. The biological signal processing device according to claim 6.

9. a weight determining means for determining the first weight and the second weight before or after the reflected wave is acquired by the reflected wave acquiring means, the phase signal acquiring means uses the first weight and the second weight determined by the weight determining means; The biological signal processing device according to claim 8 .

10. the weight determining means determines the first region and the second region by beamforming or null beam for the reflected wave, or by image processing of an image of the living body. The biological signal processing device according to claim 9 .

11. The transmitting antenna transmits radio waves using a continuous frequency modulation method.

11. The biological signal processing device according to claim 2, wherein the biological signal processing device is a biological signal processing device.

12. the phase signal acquiring means acquires a second phase signal using a metal plate placed on the living body or a placement area including backscatter as a second reflection area; The biological signal processing device according to claim 1 .

13. A reflected wave acquisition function that acquires reflected waves of radio waves transmitted toward the living body; a phase signal acquisition function that acquires a first phase signal from a first region in the living body and a second phase signal from a second region different from the first region using the acquired reflected wave; a vital information acquisition function that acquires vital information of the living body using a ratio between the acquired first phase signal and the acquired second phase signal; an output function for outputting the acquired vital information; A biological signal processing program characterized by causing a computer to realize the above.

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