Biological signal processing device and biological signal processing program

Abstract

[Problem] To acquire vital information having enhanced accuracy from reflected waves obtained by transmitting radio waves to a living body. [Solution] As shown in Fig. 1, a biological signal processing device according to the present embodiment uses one radar module employing array antennas (23, 25), and by subjecting a reception signal to beam forming or using null beams, the ratio of complex signals of two reflected waves, one from a region R1 exhibiting large motion due to inclusion of vitals and the other from a region R2 exhibiting small motion due to absence of vitals, is used to extract a vital signal with body motion components removed. In the present embodiment, as a method for acquiring the reflected wave by designating a specific site, such as the region R2 (shoulder) having small motion due to absence of vitals, the reflected wave is multiplied by weight information w1, w2 obtained in advance by beamforming.

Description

Biological signal processing device and biological signal processing program

[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.

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

[0003] However, measurement methods using radio waves have the problem that noise due to the subject's movements is included in the vital signs. That is, while body surface fluctuations due to heartbeats are approximately 0.5 mm, for example, when measuring a driver's vital signs using radar in a moving vehicle, 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 the vital signs. Patent Document 1 proposes a technology to eliminate the effects of such body movements. The technology described in Patent Document 1 extracts vital signs from which noise due to the subject's body movements has been removed, based on the difference between multiple distance information calculated using reflected waves of radio waves transmitted toward multiple different regions of the subject.

[0004] However, in the technology described in Patent Document 1, various signal processing operations 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 accurately obtain distance information. When a wide band is not available or when a 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. Therefore, errors that occur before the difference in distance information is obtained accumulate, resulting in low accuracy in the calculated vital signs.

[0005] Patent No. 7255748

[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.

[0007] The present invention provides a biological signal processing device comprising: a reflected wave acquisition means for acquiring reflected waves of radio waves transmitted toward a living organism; a phase signal acquisition means for acquiring a first phase signal from a first region of the living organism and a second phase signal from a second region different from the first region using the acquired reflected waves; a vital information acquisition means for acquiring vital information of the living organism 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.

[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.

[0009] 1 is a diagram for explaining the configuration of a biological signal processing device. FIG. 2 is a diagram for explaining the hardware configuration of a signal processing device. FIG. 3 is a flowchart for explaining the procedure of biological signal processing. FIG. 4 is an explanatory diagram conceptually showing a created radar cube. FIG. 5 is an explanatory diagram showing the results of distance FFT for each channel. FIG. 6 is an explanatory diagram showing IQ data constituting a distance bin for each channel on a two-dimensional complex plane. FIG. 7 is an explanatory diagram conceptually showing the process of removing body motion components. FIG. 8 is an explanatory diagram plotting IQ data R1, R2 and IQ' data after body motion components have been removed on a complex plane. FIG. 9 is an explanatory diagram showing the frequency characteristics of IQ data R1, R2 and IQ' data after body motion components have been removed. FIG. 10 is an explanatory diagram conceptually showing a heartbeat waveform and heart rate extracted from IQ' data after body motion components have been removed. FIG. 11 is an explanatory diagram of an equation for calculating weight information w. FIG. 12 is an explanatory diagram showing a state in which a metal plate or the like is attached to a driver's seat belt.

[0010] A preferred embodiment of the biological signal processing device 1 and biological signal processing program of the present invention will be described in detail below with reference to Figures 1 to 12. (1) Overview of the Embodiment As shown in Figure 1, the biological signal processing device 1 of this embodiment uses a single radar module using array antennas (23, 25). By beamforming or null beaming the received signal, a ratio of complex signals of reflected waves h(t)1 from a region R1 of the subject (living body) 7, which contains vital signs and therefore exhibits large movement, and reflected waves h(t)2 from regions R2 and R3, which do not contain vital signs and therefore exhibit small movement, is used to extract a vital signal from which body movement components have been removed. In this embodiment, a method for acquiring reflected waves by specifying specific regions, such as region R2 (shoulder) or region R3 (flank), which do not contain vital signs and exhibit small movement, is achieved by multiplying the reflected waves by weight information w1 and w2 previously determined by beamforming.

[0011] (2) Details of the Embodiment Fig. 1 is a diagram illustrating the configuration of a biosignal processing device 1 for measuring biosignals (vital signs, vital signals) in this embodiment. In this embodiment, biosignals measured include respiration, heart rate, and pulse wave. In the embodiment described below, the biosignals are measured when a subject 7 seated in a chair moves back and forth as indicated by an arc-shaped arrow 60. However, the device can be widely used in a variety of situations, such as being installed in a vehicle to measure the biosignals of a driver, detecting the biosignals of users in a hospital or nursing home, or being installed on a home bathroom sink to detect the biosignals of a person washing their face, or detecting the biosignals of a person 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, etc. 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 mixed signal to the signal processing device 4. The millimeter wave circuit 2 includes an oscillator 21, a distribution phase shift unit 24, mixers 26 and 27, a transmitting antenna 23, and a receiving antenna 25.

[0013] The control device 3 controls the driving of the transmitter 21, supplying power to the transmitter 21 and driving 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 FMCW (frequency continuously modulated wave) so that the frequency increases linearly over time. The control device 3 controls the transmitter 21 to output non-directional millimeter waves, rather than millimeter waves with directionality toward a predetermined area of ​​the person 7.

[0014] The transmitter 21 includes a millimeter-wave transmitting 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 (e.g., 79 GHz band). Alternatively, a transmitter 21 that transmits microwaves (e.g., 24 GHz band) instead of millimeter waves may be used. In the biosignal processing device 1 of this embodiment, by using radio waves (millimeter waves) in the high-frequency band, reflected waves from the skin surface (body surface) of the subject 7 become dominant, making it possible to effectively observe phase fluctuations as body surface fluctuations. The transmission waves (millimeter waves) generated by the transmitter 21 are distributed to the transmitting antenna 23 and the distribution phase shifter 24 via a transmission path.

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

[0016] The transmitting antenna 23 is configured as a two-element patch array antenna and irradiates the millimeter waves generated by the transmitter 21 toward the subject 7. The receiving antenna 25 is configured as a four-element patch array antenna and receives the millimeter waves transmitted by the transmitting antenna 23 and reflected from the subject 7, distributes them, and sends them to mixers 26 and 27. In this way, the biological signal processing device 1 configures virtual antennas for a total of eight channels by adopting a MIMO (Multiple Input Multiple Output) method for transmitting and receiving using multiple antennas, but Fig. 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 large body movements in the direction of the millimeter-wave circuit 2, and also moves slightly due to vital movements 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] Mixer 26 mixes the reflected wave received by receiving antenna 25 with the transmitted wave from oscillator 21, and outputs an in-phase I(t) signal to signal processing device 4. Mixer 27 mixes the reflected wave received by receiving antenna 25 with a reference wave (transmitted wave) phase-shifted by 90°, and outputs an orthogonal Q(t) signal to signal processing device 4.

[0019] The signal processing device 4 functions as a biological signal processing device as set forth in claim 1, and the biological signal processing device 1 shown in Fig. 1 functions as a biological signal 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, etc.

[0020] The CPU 41 executes various programs, such as the biological signal processing program 451 of this embodiment, to perform 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, the RAM 43 temporarily stores IF data (IF raw data) 431, a radar cube 432, a phase signal 433, vital information 434, and various other data.

[0021] The IF data 431 stores the I(t) and Q(t) signals output from the millimeter-wave circuit 2. Continuously frequency-modulated millimeter waves are sequentially transmitted from the transmitting antenna 23, and n I(t) and Q(t) signals are sampled per transmission unit (chirp set) and stored for each mch (channel). Therefore, m × n I(t) and Q(t) signals are stored in the IF data 431 for each chirp set. In this embodiment, the number of samples n per chirp set stored in the IF data 431 is 256, but it can be less (e.g., 128) or more (e.g., 512). Here, a chirp set consists of two chirps, since it corresponds to the number of transmitting antennas 23 (two). Meanwhile, the number of channels m is eight (two transmit × four receive), but it can also be (transmit f × receive v) channels, e.g., (three transmit × four receive) = 12 channels.

[0022] The radar cube 432 stores IQ data consisting of I(t) and Q(t) stored in the IF data 431, which is generated for each channel, sampling, and chirp set. 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 FIG. 1. Here, j is the imaginary unit, and t represents time. The radar cube 432 forms a virtual cube by arranging the IQ data in the sampling direction (hereinafter referred to as the distance direction) within each chirp set, 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 FIG. 4), as will be described in detail later.

[0023] A first phase signal from the first region R1 (see FIG. 1 ) and a second phase signal from the second region R2 are stored in the phase signal 433. The first phase signal and the second phase signal are calculated by multiplying predetermined weight information w1 and w2 by the IQ data for each channel obtained by range FFT analysis of the radar cube 432, and are stored in the phase signal 433. Here, the weight information w1 and w2 are 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 body movement components from the first phase signal and second phase signal stored in phase signal 433. Other data stored in 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 receiving operations from a 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 a 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 for reading and writing various information such as programs and data from and to the storage medium. The storage medium used in the storage device 45 is primarily a semiconductor storage device such as a hard disk or a solid-state drive (SSD), but external storage media such as semiconductor storage media such as memory chips or IC cards, or optically readable storage media 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) and Q(t) signals output from the millimeter wave circuit 2. The weighting information 452 is weighting information that extracts phase signals from predetermined regions R1 and R2 of the subject 7 by multiplying the weighting information 452 by a wave reflected from the subject 7, and weighting information w1 corresponding to region R1 and weighting information w2 corresponding to region R2 are stored in advance. The vital information 453 is data that is read from the RAM 43 as vital information 434 obtained by the biological signal processing program 451 and stored in the storage device 45 together with information such as the processing date and time and the subject.

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

[0029] The CPU 41 acquires data necessary for analysis (step 10). That is, 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) per chirp set, and sequentially stores them in the IF data 431 of the RAM 43. Here, 256×8 I(t) signals and Q(t) signals are stored per chirp set.

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

[0031] The CPU 41 generates one IQ data set from a set of I(t) and Q(t) signals for one sample in one channel stored in the IF data 431, using h(t) = I(t) + jQ(t) in Equation 22 shown in FIG. 1 . Then, for one chirp set, the CPU 41 generates IQ data sets equal to m (=8) of all channels multiplied by n (=256) of the number of samples in the chirp set. The CPU 41 sequentially generates IQ data sets for each chirp set that are 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 generating IQ data sets for each chirp set and storing them in the radar cube 432, p (e.g., 90,000) of n x m IQ data sets shown in FIG. 4 are generated in the time direction (downward along 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. 4. The CPU 41 then averages s IQ data aligned in the time direction and stores this average radar cube, which is one average IQ data, in the RAM 43. As a result, the radar cube 432 shown in FIG. 4 has q / s frames aligned in the time direction (vertical direction). By averaging s IQ data aligned in the time direction in one frame to create average IQ data, it is possible to reduce noise in each average IQ data (IQ data).

[0033] In this embodiment, the number s of chirp sets constituting one frame is set to 15, 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 = 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 a distance bin (step 16). That is, the CPU 41 converts each frame of the radar cube 432 in FIG. 4 into a distance by applying a distance FFT (Fast Fourier Transform) in the distance direction (sampling direction) for each channel (ch1 to ch8).

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

[0037] Next, the CPU 41 determines the overall distance bin by sequentially identifying the IQ data with the largest distance value (taking the peak value) from n pieces of IQ data (=256 pieces) in the distance direction for each of channels 1 to 8 for each frame (each row in the distance direction × channel direction in Figure 4). For channel 1 (ch1) in the first row of chirp sets in Figure 4, the distance FFT is applied to n pieces of IQ data in the distance direction (to the right in the figure), and the IQ data taking the peak distance value (e.g., the shaded IQ data 38) is identified as the optimal IQ data. This identifies m pieces of IQ data per frame, and a distance bin consisting of a total of m × q pieces of IQ data is 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 the IQ data after applying the distance FFT. FIG. 6 shows the IQ data constituting the distance bin for each channel, plotted on a two-dimensional complex plane. As an example, FIG. 6 plots IQ data for 6,000 chirp sets for each channel. As shown in FIG. 6, by plotting the IQ data for each channel on a two-dimensional complex plane, the data follows a periodic, approximately concentric trajectory in synchronization with the body movements and vital signs of the subject 7. The concentric trajectory occurs because the radio waves irradiated to the subject 7 are millimeter waves, which have a very high frequency. In the case of microwaves, which have a frequency lower than that of millimeter waves, the data follows a concentric, arc-like trajectory.

[0039] Next, the CPU 41 acquires IQ data R1 and IQ data R2 for each region (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 calculate the IQ data R1 and IQ data R2 corresponding to regions R1 and R2. Specifically, the CPU 41 converts the IQ data of m channels (1ch to 8ch) into a vector and multiplies it by the weight information w1 and w2 expressed as a Hermitian matrix to acquire the IQ data R1 and IQ data R2 corresponding to regions R1 and R2 of the subject 7. The acquired IQ data R1 and IQ data R2 are complex signals expressed by the equation h(t) = I(t) + jQ(t), similar to Equation 22 (see FIG. 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 obtains the IQ' data after removing the body motion component (step 22). That is, the CPU 41 obtains the IQ' data after removing the body motion component by calculating the ratio (IQ data R1) / (IQ data R2) of the IQ data R1 from region R1 and the IQ data R2 from 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 FIG. 6 will shift from the correct origin O to a virtual origin O', resulting in a signal error. For this reason, the CPU 41 removes the body motion component from the ratio of the IQ data R1 and IQ data R2 after correcting the origin position.

[0041] Figure 7 conceptually illustrates the process of body motion component removal. Note that in Figure 7, the origin correction and body motion component removal processes are explained using microwaves, which are easier to illustrate than the millimeter waves shown in Figure 6, but the principles are the same. Also, in Figure 7, IQ data R1 from region R1, expressed by h(t) = I(t) + jQ(t) of Equation 22 on a complex plane with real axis I and imaginary axis Q, is represented by S1, and IQ data R2 from region R2 is represented by S2.

[0042] The distance between the origin O and the virtual origin O' is represented by offsets C1 and C2, the vital component included in the IQ data is represented by exp{jθv}, and the body movement component included in the signal is represented by exp{jθm}. Then, the IQ data R1 from the 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, the IQ data R2 from the 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 locus of the arcs 61 and 62, and then calculating the distance from this virtual origin O' to the origin O of the complex plane.

[0043] As shown in Figure 7(b), the CPU 41 calculates exp{jθv} by calculating the ratio of (S1-C1) in region R1, from which error components due to reflection components from fixed objects have been removed, to (S2-C2) in region R2. That is, the CPU 41 can calculate exp{jθv}, which is IQ' data containing only vital components and not body movement components, using the following equation A, as shown by arc 63 in Figure 7(b): (S1-C1) / (S2-C2)=exp{j(θv+θm-θm)}=exp{jθv}...A

[0044] FIG. 8 plots on a complex plane the IQ data R1 and R2 (after removing offsets C1 and C2; the same applies to FIG. 9 ) for regions R1 and R2 and the IQ′ data after removing the body motion component. Note that the IQ data R1 and R2 are 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 motion component. FIGS. 8 and 9 show laboratory measurement data, measured while a subject 7, seated 0.5 m from the millimeter-wave circuit 2, was periodically moving back and forth within a body motion displacement range of 2.0 cm (body motion frequency: 0.5 Hz).

[0045] As shown in Figures 9(a) and (b), the IQ data R1 and R2 have amplitude spectrum peaks 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 IQ' data calculated from the ratio of the IQ data R1 to the IQ data R2 has the peak value at a frequency of 0.5 Hz removed, as shown in Figure 9(c). In this way, by calculating the ratio of the IQ data R1 to the IQ data R2, the body movement component of the subject 7 can be removed. In practice, not only the body movement component of the subject 7 but also noise commonly contained in the IQ data R1 and the IQ data R2 can be removed, thereby obtaining more accurate IQ' data.

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

[0047] 10A and 10B conceptually show the heart rate waveform and heart rate extracted from the IQ' data after the body movement component has been removed. FIG. 10A conceptually shows the heart rate waveform after the filter has been applied. The CPU 41 obtains vital information (heart rate) by determining each peak of this heart rate waveform and determining the corresponding heart rate from the time between adjacent peaks, and stores the obtained vital information in the vital information 434 of the RAM 43. FIG. 10B shows the obtained heart rate.

[0048] The CPU 41 functions as an output unit that outputs 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, outputting the information to the vital information 453 in the storage device 45, displaying the information on the display of the input / output unit 44, and providing the information to the outside via a communication unit (not shown in FIG. 2). Since the CPU 41 uses region R1 as the region onto which the heart is projected, it also contains a respiratory component in addition to a heartbeat component. Therefore, the CPU 41 can also separate the respiratory waveform from the IQ' data after removing the body movement component and determine the respiratory rate.

[0049] Next, we will explain the weight information w1 and w2 used to obtain the IQ data R1 and IQ data R2 corresponding to regions R1 and R2 from the IQ data obtained in step 18. The weight information 452 (weight information w1 and w2) stored in the storage device 45 used in this embodiment is based on the assumption that the measurement location and the posture of the subject 7 are fixed, such as the driver, passenger, or patient in a specified examination position (hereinafter referred to as a specific measurement location). By having the subject 7 in this fixed measurement location, it is possible to identify the location of region R1 with large movement (body movement + vital signs) and regions R2 and R3 with small movement (body movement only) as general regions independent of the subject 7.

[0050] In the biological signal processing device 1, before performing a measurement on a specific subject 7, weight information w1, w2 for regions R1, R2, etc. of the experimental subject 7 is calculated for each specific measurement location and stored in weight information 452 in the storage 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, when the specific measurement location (driver's seat) has been determined corresponding to the location where the millimeter-wave circuit 2 is installed, only the weight information w1, w2 corresponding to the specific measurement location is stored in the storage device 45, and the CPU 41 uses the stored weight information w1, w2.

[0051] FIG. 11 shows the formula for calculating the weight information w. The pre-stored weight information w (w1, w2) will be described with reference to the formula in FIG. 11. The weight information w1 and w2 are calculated by beamforming to the subject 7 present at a specific measurement location. Specifically, differences d1 to d8 in the propagation path length of the millimeter wave from the body part (regions R1, R2) of the subject 7 to be beamformed to each element (2 transmit × 4 receive = 8 elements) 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. 11B is created. In FIG. 11B, weight information w(w1, w2) is the Hermitian matrix a{H} of steering vector a(a1, a2). The created weight information w1, w2 is saved in storage device 45. Note that in the millimeter-wave circuit 2 described in this embodiment, an array antenna with (2 transmit × 4 receive) = 8 channels is described, so the dimension of the steering vector is 8. However, when an array antenna with (f transmit × v receive) 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) from region R1 of the subject's body, which contains vital components and exhibits large phase fluctuations, and phase data (IQ data R2) from region R2, which does not contain vital components and exhibits small phase fluctuations. The acquired IQ data R1 and IQ data R2 are then used to remove body movement components by calculating the ratio of the two phase data (IQ data R1 / IQ data R2). Therefore, the biological signal processing of this embodiment uses data that is less processed and closer to the raw data than 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 calculating the difference between the two distance information. This allows for more accurate vital information to be obtained. Furthermore, the biological signal processing device 1 of this embodiment can obtain highly accurate vital information even when a frequency band is unavailable or when the distance to the living body cannot be accurately detected using a narrowband CW radar, because the body movement components are removed by using the ratio of the phase data (IQ data R1 / IQ data R2).

[0054] Although one embodiment of the biosignal processing device 1 of the present invention has been described above, the present invention is not limited to the described embodiment, and modifications within the scope of the claims and the scope described in the embodiment, as well as further modifications to other variations, are possible. For example, in the described embodiment, a case was described in which the IQ data of a complex signal acquired using transmitted millimeter waves hf(t) and reflected waves hv(t) was multiplied by weighting information w1 and w2 to obtain reflected wave IQ data R1 from region R1 (heart area) and reflected wave IQ data R2 from region 2 (shoulder). In this embodiment, the weighting information w1 and w2 used to calculate the IQ data R1 and IQ data R2 were obtained in advance by beamforming for the subject 7 at a specific measurement location, and the weighting information w1 and w2 defined corresponding to the specific measurement location were read from the storage device 45 and used in the actual measurement.

[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 regions 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 then stores the created weight information w1 and w2 in the RAM 43 and may use the information continuously while measurements are being performed on the subject 7, or may calculate the weight information w1 and w2 every predetermined number of frames (e.g., 100 frames).

[0056] In the embodiments and modifications 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 body part 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 areas R1 and R2.

[0057] Furthermore, in the described embodiments and variations, millimeter waves are transmitted to the subject 7 who is not wearing any special device or object. 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, the IQ data R2 can be more easily separated by placing a metal plate on a location that moves in the same way as the body, such as part of a seat belt in the case of a driver in a vehicle. Furthermore, the metal plate may be attached to the subject 7's clothing, such as the shoulder (R2) or flank (R3), in addition to the seat belt.

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

[0059] FIG. 12 illustrates a state in which a metal plate (or backscatter) is provided on the driver's seat belt. Note that FIG. 12 corresponds to FIG. 1 . As shown in FIG. 12 , in the above-described modified example, a metal plate 66 or backscatter 67 (hereinafter simply referred to as the metal plate 66, etc.) is provided on the driver's seat belt 56. The metal plate 66, etc. is provided on the outer surface of the seat belt 56 (the surface facing the millimeter-wave circuit 2) or inside the bag-shaped seat belt 56. While FIG. 12 illustrates a case in which the metal plate 66, etc. is provided in a shoulder region R2 that does not contain vital components of the subject 7 while the seat belt 65 is fastened, it may also be provided in a flank region R3 that does not contain vital components. Note that it is also possible to acquire vital information by outputting millimeter waves toward the passenger in the front passenger seat, assuming that the passenger is the subject 7. In this case, the seat belt of the passenger in the front passenger seat will be worn in the opposite direction to that in FIG. 12 (from upper left to lower right), so it is preferable to arrange the metal plate 66 etc. in a position corresponding to the flank region R3.

[0060] In the described embodiment and modified examples, noise removal is performed before the body motion component removal process (step 22). However, since these noises can also be removed by removing the body motion component by calculating the frequency component ratio (IQ data R1 / IQ data R2), it is possible to omit the preliminary noise removal process. Here, the following (a) to (c) are examples of noise removal processes that can be omitted, and any one or more of these may be omitted. (a) Step 14: averaging s IQ data aligned in the time direction across multiple frames to obtain average IQ data. (b) Step 16: removing clutter components from the surroundings of the subject 7 by subtracting the average of the IQ data that have undergone distance FFT in the time direction as a DC component. (c) Step 22: returning the virtual origin O' of the IQ data R1 and R2 to the origin O by calculating (S1-C1) and (S2-C2) from the phase component ratio, which was performed immediately before removing the body motion component.

[0061] Furthermore, in the described embodiment and modified examples, the left chest is used as the region R1 where the heart is projected, which is a region with large movement because it contains vital signs. However, the region R4 where the abdomen is projected may also be used as a region with large movement because it contains vital signs, and vital signals may be acquired from this region. In this case, IQ" data containing only vital components, without 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 the region R4 where the abdomen is projected and the region R2 or R3 where the shoulders or flanks are projected. In the case of the region R1 where the heart is projected, the IQ' data after removing the body movement components contains a respiratory component and a heartbeat component, so that either one or both of these components can be extracted. In contrast, only the respiratory component is extracted from IQ" data obtained for the region R4 where the abdomen is projected instead of the region R1. In this case, the respiratory component can be extracted with high accuracy because the heartbeat component is not included.

[0062] In addition, in the embodiments and variant examples, region R2 including the shoulders and 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 above-described embodiments and modifications, the MIMO system and the FMCW (Frequency Continuous Modulation Waveform) system have been described, but other systems that can be substituted as appropriate may be adopted. For example, instead of the FMCW system, a CW (continuous wave) system that outputs a continuous wave with constant amplitude and frequency can be adopted. In the case of this CW system, IQ data R1 and IQ data R2 corresponding to regions R1 and R2 are acquired 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 embodiment and modified examples, a case has been described in which non-directional millimeter waves are transmitted from the transmitting antenna 23 without being given directivity by beamforming or the like, and beamforming or the like is performed on the reflected waves received by the receiving antenna 25. In contrast, the control device 3 may transmit directional millimeter waves from the transmitting antenna. That is, the control device 3 may control the phase of the millimeter waves transmitted from the transmitting antenna 23 so that they have directivity in the directions of 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 a chirp set number q = 90,000 (q / s = 6,000 frames) has been described, including the purpose of acquiring data for verification. Alternatively, IQ' data (exp{jθv}) of only vital components 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, preferably every 6 frames. This allows IQ' data to be obtained promptly after starting measurement (every time 6 frames of chirp sets are transmitted and received). Furthermore, rather than calculating IQ' data for every u frames, after receiving the first u frames, IQ' data is calculated using the total u frames (the most recent frame and the previous frame (u−1)). This allows new IQ' data and new vital information to be obtained for each frame after the u frames.

[0066] In the described embodiment and modified examples, the IQ data acquired from the millimeter wave circuit 2 is multiplied by weight information w1 and w2 to acquire IQ data R1 for region R1 and IQ data R2 for region R2. That is, the case where beamforming is performed on received reflected waves, rather than on transmitted waves, has been described. Alternatively, millimeter waves may be irradiated onto regions R1 and R2 by beamforming on transmitted waves (millimeter waves) from each transmitting antenna 23.

[0067] In the above-described embodiment and modified example, a case where a phase signal is acquired using IQ data acquired from the millimeter-wave circuit 2 has been described. That is, a case where a complex signal consisting of an in-phase signal I and a quadrature signal Q, which are formed by radio waves transmitted by a transmitting antenna and reflected waves received by a receiving antenna, is acquired as the first phase signal and the second phase signal has been described. In contrast, the first phase signal and the second phase signal may be a complex signal consisting of only the in-phase signal I or the quadrature signal Q. Even in this case, a complex number containing phase information can be obtained by applying a distance FFT to the radar cube formed by the in-phase signal I or the quadrature signal Q. Therefore, even when only the in-phase signal I or the quadrature signal Q is acquired, the CPU 41 can acquire a vital signal using the same processing procedure as the biological signal processing described in FIG. 3.

[0068] In the above-described embodiment and modified examples, the biosignal processing is performed using millimeter waves, but other radio waves, such as microwaves or submillimeter waves (decimeter waves), may be used. In this case, the transmitter 21 is configured to emit microwaves or submillimeter waves.

[0069] (Configuration 1) A biological signal processing device comprising: reflected wave acquisition means for acquiring reflected waves of radio waves transmitted toward a living body; phase signal acquisition 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 from the acquired reflected waves; vital information acquisition means for acquiring vital information of the living body using a ratio of the acquired first phase signal to the acquired second phase signal; and output means for outputting the acquired vital information. (Configuration 2) The biological signal processing device according to Configuration 1, comprising: a transmitting antenna for transmitting microwaves, millimeter waves, or submillimeter waves toward the living body; and a receiving antenna for receiving reflected waves of the radio waves transmitted from the transmitting antenna, wherein the phase signal acquisition means acquires the first phase signal and the second phase signal from the reflected waves received by the receiving antenna. (Configuration 3) The biological signal processing device according to Configuration 1 or 2, wherein 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 a radio wave transmitted by the transmitting antenna and a reflected wave received by the receiving antenna. (Configuration 4) The biological signal processing device according to Configuration 1, 2, or 3, wherein the phase signal acquiring means sets, as the first region, a region in which phase fluctuation due to a vital sign of the living body is larger than that of the second region. (Configuration 5) The biological signal processing device according to Configuration 1, 2, or 3, wherein the phase signal acquiring means sets, as the first region, a region onto which the heart or abdomen of the living body is projected, and sets, as the second region, a region onto which the shoulder or flank of the living body is projected. (Configuration 6) The biological signal processing device according to any one of Configurations 1 to 5, wherein at least one of the transmitting antenna and the receiving antenna has a plurality of antennas. (Configuration 7) The biological signal processing device according to any one of Configurations 1 to 6, wherein 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.(Configuration 8) The biological signal processing device of any one of Configurations 1 to 6, wherein 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. (Configuration 9) The biological signal processing device of Configuration 8, further comprising: 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, and the phase signal acquiring means uses the first weight and the second weight determined by the weight determining means. (Configuration 10) The biological signal processing device of Configuration 9, wherein 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 captured of the living body. (Configuration 11) The biological signal processing device of any one of Configurations 2 to 10, wherein the transmitting antenna transmits radio waves using a continuous frequency modulation method. (Configuration 12) A biological signal processing device according to any one of configurations 1 to 11, characterized in that the phase signal acquisition 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. (Configuration 13) A biological signal processing program characterized by causing a computer to realize: 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 area in the living body and a second phase signal from a second area different from the first area using the acquired reflected waves; a vital information acquisition function that acquires vital information in the living body using a ratio between the acquired first phase signal and the acquired second phase signal; and an output function that outputs the acquired vital information.

[0070] REFERENCE SIGNS LIST 1 Biological signal processing device 2 Millimeter wave circuit 3 Control device 4 Signal processing device 7 Subject 21 Transmitter 23 Transmitting antenna 24 Distribution phase shift unit 25 Receiving antenna 26, 27 Mixer 41 CPU 43 RAM 431 IF data 432 Radar cube 433 Phase signal 434 Vital information 44 Input / output unit 45 Storage device 451 Biological signal 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 biological signal processing device comprising: a reflected wave acquisition means for acquiring reflected waves of radio waves transmitted toward a living body; a phase signal acquisition 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 acquisition means for acquiring vital information of the living body using the ratio between the acquired first phase signal and the acquired second phase signal; and an output means for outputting the acquired vital information.

2. A biological signal processing device as described in claim 1, characterized in that it comprises a transmitting antenna that transmits microwaves, millimeter waves or submillimeter waves toward the living body, and a receiving antenna that receives reflected waves of the radio waves transmitted from the transmitting antenna, and the phase signal acquisition means acquires the first phase signal and the second phase signal from the reflected waves received by the receiving antenna.

3. The biological signal processing device described in claim 2, characterized in that 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 waves transmitted by the transmitting antenna and the reflected waves received by the receiving antenna.

4. The biological signal processing device according to claim 1, characterized in that the phase signal acquisition means sets the first region as a region in which phase fluctuations due to vital signs of the living body are larger than those in the second region.

5. The biological signal processing device according to claim 1, characterized in that the phase signal acquisition means defines the area onto which the heart or abdomen of the living body is projected as the first area, and the area onto which the shoulder or flank of the living body is projected as the second area.

6. The biological signal processing device according to claim 2, wherein at least one of the transmitting antenna and the receiving antenna comprises a plurality of antennas.

7. The biological signal processing device according to claim 6, characterized in that the phase signal acquisition 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.

8. The biological signal processing device according to claim 6, characterized in that the phase signal acquisition 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.

9. A biological signal processing device as described in claim 8, characterized in that it is provided with a weight determination means that determines the first weight and the second weight before or after the reflected wave is acquired by the reflected wave acquisition means, and the phase signal acquisition means uses the first weight and the second weight determined by the weight determination means.

10. A biological signal processing device as described in claim 9, characterized in that the weight determination means determines the first area and the second area by beamforming or null beam for the reflected wave, or by image processing of an image captured of the biological body.

11. A biological signal processing device according to any one of claims 2 to 10, characterized in that the transmitting antenna transmits radio waves using a continuous frequency modulation method.

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

13. A biological signal processing program that causes a computer to realize the following: a reflected wave acquisition function that acquires reflected waves of radio waves transmitted toward a living organism; a phase signal acquisition function that acquires a first phase signal from a first region of the living organism and a second phase signal from a second region different from the first region using the acquired reflected waves; a vital information acquisition function that acquires vital information of the living organism using the ratio between the acquired first phase signal and the acquired second phase signal; and an output function that outputs the acquired vital information.

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