Heartbeat signal measuring device or heartbeat signal measuring method

Abstract

A heartbeat signal measurement device (3) comprises: an acquisition unit (31) that acquires a set of a range bin where a living body may be present, an azimuth direction bin in an azimuth direction, and an elevation direction bin in an elevation direction, and a signal digitally beamformed in the azimuth direction and elevation direction in order with respect to the range bin; and a measurement unit (32) that generates phase signals on the basis of the digitally beamformed signal, the range bin, the azimuth direction bin in the azimuth direction, and the elevation direction bin in the elevation direction, removes a removal target component due to respiration or body movement of a subject from the generated phase signals, and selects a phase signal from the phase signals from which the removal target component has been removed on the basis of the result of evaluating the periodicity of the signals, thereby measuring the heartbeat signal of the subject.

Description

[Technical Field]

[0001] The present disclosure relates to a heartbeat signal measuring device or a heartbeat signal measuring method. [Background technology]

[0002] A technique for measuring the heart rate signal of a subject using frequency-modulated continuous wave (FMCW) radar is known. FMCW radar transmits frequency-modulated radio waves to a target, receives the radio waves reflected by the target, generates a beat signal having a frequency corresponding to the difference in frequency between the transmitted and received radio waves, and measures the distance to the target based on the frequency of the generated beat signal.

[0003] For example, a device described in Patent Document 1 transmits radio waves to a subject, receives the radio waves reflected by the subject, and calculates a distance spectrum by performing an FFT (Fast Fourier Transform) on a beat signal generated based on the received signal. Based on the distance spectrum, the device selects a distance bin containing the reflected waves from the subject, selects the distance bin with the largest phase change from multiple peaks, and measures the phase change in the selected distance bin. The phase change includes not only heartbeat but also phase changes due to breathing or body movement. Therefore, by using a polynomial to remove trend components due to breathing or body movement, it is possible to measure body surface fluctuations due to heartbeat, i.e., heartbeat signals. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-123929 Summary of the Invention [Problem to be solved by the invention]

[0005] The conventional technology described in Patent Document 1 evaluates the magnitude of phase change in multiple distance bins and selects the distance bin with the largest phase change. However, body surface fluctuations caused by respiration or body movement are greater than fluctuations caused by heartbeat. Therefore, when the distance bin with the largest phase change is selected, the distance bin with the largest phase change due to respiration or body movement is selected, which poses a problem of not being able to measure the heartbeat signal accurately.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a heartbeat signal measuring device that can measure a heartbeat signal from which components derived from the breathing or body movement of the subject have been removed. [Means for solving the problem]

[0007] The heartbeat signal measuring device according to the present disclosure includes an acquisition unit that acquires sets of distance bins, azimuth direction bins, and elevation direction bins in which a living body may be present, calculated based on received signals of radio waves irradiated to the subject and reflected by the subject, and signals beamformed in the azimuth direction and elevation direction for the distance bins in order; and a measurement unit that measures the heartbeat signal of the subject by generating phase signals based on the beamformed signals, the distance bins, the azimuth direction bins, and the elevation direction bins, removing components to be removed that are derived from the subject's breathing or body movement from the generated phase signals, and selecting phase signals from the phase signals from which the components to be removed have been removed based on evaluation results of the signal periodicity. [Effects of the Invention]

[0008] According to the present disclosure, a heartbeat signal of a subject is measured by acquiring sets of distance bins, azimuth direction bins, and elevation direction bins in which a living body may be present, and signals beamformed in the azimuth and elevation directions in order for the distance bins, generating phase signals based on the beamformed signals, the distance bins, the azimuth direction bins, and the elevation direction bins, removing components derived from the subject's breathing or body movement from the phase signals, and selecting a phase signal from the phase signals from which the components to be removed have been removed based on an evaluation result of the signal periodicity.In this way, the heartbeat signal measurement device according to the present disclosure can measure the heartbeat signal from which the components derived from the subject's breathing or body movement have been removed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing an example of the configuration of a heartbeat signal measuring system according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a measurement unit in the first embodiment. [Figure 3] 3 is a flowchart showing a heartbeat signal measuring method according to the first embodiment. [Figure 4] 1 is a graph showing a chirp signal for each transmission cycle. [Figure 5] 4 is a flowchart showing detailed processing of step ST1 in FIG. 3. [Figure 6] FIG. 1 is a schematic diagram showing an overview of digital beamforming. [Figure 7] 4 is a flowchart showing detailed processing of step ST2 in FIG. 3. [Figure 8] 8 is a flowchart showing detailed processing of step ST2-2 in FIG. 7. [Figure 9] FIG. 1 is a diagram showing a complex plane on which the real and imaginary parts of a biological information signal are plotted. [Figure 10] 10A, 10B and 10C are waveform diagrams showing phase-unwrapped phase signals. [Figure 11]11A, 11B, and 11C are waveform diagrams showing the phase signal and the trend component before the trend component is removed. [Figure 12] 12A and 12B are diagrams showing a highly periodic phase signal and an autocorrelation function from which the trend component has been removed. [Figure 13] 13A and 13B are diagrams showing a less periodic phase signal and autocorrelation function from which the trend component has been removed. [Figure 14] 14A and 14B are block diagrams showing a hardware configuration that realizes the functions of the heartbeat signal measuring device according to the first embodiment. [Figure 15] FIG. 10 is a block diagram showing an example of the configuration of a heartbeat signal measuring system according to a second embodiment. [Figure 16] FIG. 10 is a block diagram showing an example of the configuration of a measurement unit in the second embodiment. [Figure 17] 10 is a flowchart showing a heartbeat signal measuring method according to the second embodiment. [Figure 18] 18A, 18B, and 18C are waveform diagrams showing the phase signal from which the low-frequency components have been removed and the low-frequency components. [Figure 19] FIG. 10 is a block diagram showing an example of the configuration of a heartbeat signal measuring system according to a third embodiment. [Figure 20] 10 is a flowchart showing a heartbeat signal measuring method according to a third embodiment. [Figure 21] FIG. 10 is a diagram showing the extraction results of distance bins and direction bins when there are two subjects. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiment 1 Fig. 1 is a block diagram showing an example of the configuration of a heartbeat signal measurement system 1 according to a first embodiment. In Fig. 1, the heartbeat signal measurement system 1 is a system that measures the heartbeat signal of a person being measured using radar signals, and includes a radar sensor unit 2 and a heartbeat signal measurement device 3. The radar sensor unit 2 includes N antennas 21-1, 21-2, ..., 21-N, N circulators 22-1, 22-2, ..., 22-N, N signal receiving units 23-1, 23-2, ..., 23-N, and a signal transmitting unit 24. N is an integer equal to or greater than 2.

[0011] The radar sensor unit 2 is equipped with N antennas 21-1, 21-2, ..., 21-N to improve the resolution of received signals by MIMO (Multiple-Input Multiple-Output). Each of the antennas 21-1, 21-2, ..., 21-N is a transmitting / receiving antenna, and functions as both a transmitting antenna and a receiving antenna. However, this is merely an example, and the radar sensor unit 2 may be equipped with separate transmitting antennas and receiving antennas. When the radar sensor unit 2 radiates a transmission wave, one antenna for radiating the transmission wave is selected from the antennas 21-1, 21-2, ..., 21-N.

[0012] The transmission order of the transmission waves from the antennas 21-1, 21-2, ..., 21-N is fixed. For example, the transmission order is fixed as antenna 21-1, antenna 21-2, ..., antenna 21-N. However, this is merely an example, and the transmission order may be, for example, antenna 21-N, ..., antenna 21-2, antenna 21-1.

[0013] Antenna 21-n (n = 1,...,N) emits a transmission wave related to the transmission signal output from circulator 22-n into a space in which a target object exists. The transmission wave emitted from antenna 21-n is reflected by the target object. The target object includes not only a person being measured who exists in the space, but also stationary objects such as the walls of a room that forms the space or a desk that exists in the space. Each of antennas 21-1, 21-2,...,21-N receives the reflected wave from the target object and outputs a received signal of the reflected wave to circulators 22-1, 22-2,...,22-N.

[0014] 1, the signal transmitting unit 24 includes an output destination selecting unit 241 and a signal generator 242. The signal transmitting unit 24 sequentially selects one antenna 21-n from among the antennas 21-1, 21-2, ..., 21-N to emit a transmission wave. The signal transmitting unit 24 outputs a transmission signal to the circulator 22-n connected to the selected antenna 21-n, so that the transmission wave is radiated from the selected antenna 21-n into the space in which the person being measured is present.

[0015] The output destination selection unit 241 outputs the transmission signal generated by the signal generator 242 to the circulator 22-n connected to the antenna 21-n that is next to radiate the transmission wave among the N circulators 22-1, 22-2, ..., 22-N. The signal generator 242 generates, for example, a transmission signal whose frequency changes over time or a pulsed transmission signal. Examples of transmission signals whose frequency changes over time include an up-chirp signal and a down-chirp signal. The signal generator 242 outputs a transmission signal to the output destination selection unit 241 .

[0016] The circulator 22-n (n=1, . . . , N) outputs the transmission signal output from the output destination selection unit 241 to the antenna 21-n. Furthermore, the circulator 22-n outputs the received signal output from the antenna 21-n to the signal receiving unit 23-n.

[0017] The signal receiving unit 23-n (n=1, . . . , N) performs reception processing on the received signal output from the circulator 22-n. The reception processing includes, for example, down-converting the frequency of the received signal and converting the frequency-converted received signal from an analog signal to a digital signal.

[0018] The signal receiving unit 23-n outputs a digital signal S(t, g, h, q, c) to the heartbeat signal measuring device 3. t is the reception time of the reflected wave received by the antenna 21-n. g is a variable for identifying the antenna 21-n that radiated the transmitted wave, and g=1,...,N. h is a variable for identifying the antenna 21-n that received the reflected wave, and h=1,...,N. q is a variable for identifying the hit number within a certain transmission cycle, and q=1,...,Q. Q is an integer equal to or greater than 2. c is a variable for identifying the transmission cycle of the transmitted wave radiated from the antennas 21-1, 21-2,...,21-N, and c=1,...,C. C is an integer equal to or greater than 2.

[0019] The heartbeat signal measuring device 3 includes an acquiring unit 31 , a measuring unit 32 , and an output unit 33 . The acquisition unit 31 acquires a set of distance bins, azimuth direction direction bins, and elevation direction direction bins in which a living body may be present, calculated based on the received signals of radio waves irradiated to the subject and reflected by the subject, and digital beamformed signals in the azimuth direction and elevation direction in order for the distance bins. The acquisition unit 31 includes a signal acquisition unit 311 , a preprocessing unit 312 , a stationary object suppression unit 313 , a Fourier transform unit 314 , a distance bin extraction unit 315 , an orientation bin extraction unit 316 , and a digital beamforming unit 317 .

[0020] The signal acquisition unit 311 acquires N×N×Q signals S(t, g, h, q, c) from the signal reception units 23-1, 23-2, . . . , 23-N in each transmission cycle c (c=1, . . . , C). The signal acquisition unit 311 outputs the N×N×Q signals S(t, g, h, q, c) to the pre-processing unit 312 in each transmission cycle c.

[0021] The pre-processing unit 312 acquires N×N×Q signals S(t, g, h, q, c) in each transmission cycle c (c=1, , C) from the signal acquisition unit 311. The pre-processing unit 312 calculates S(t, g, h, q, c) by adding up all hits q (q=1, , Q) for the acquired signals S(t, g, h, q, c). pre (t, g, h, c) is output to the stationary object suppression unit 313.

[0022] The stationary object suppression unit 313 receives N×N×Q preprocessed signals S pre (t, g, h, c). The stationary object suppression unit 313 obtains the obtained N×N×Q pre-processed signals S pre For (t, g, h, c), the stationary object signal S averaged over all cycles c (c = 1, , C) is sta (t, g, h). The stationary object suppression unit 313 obtains the pre-processed signal S pre (t,g,h,c) to S sta (t, g, h) are subtracted, and the signal S obtained by this subtraction is mov (t, g, h, c) is output to the Fourier transform unit 314.

[0023] In each transmission cycle c, the Fourier transform unit 314 converts N×N signals S mov Each of (t, g, h, c) is Fourier transformed in the time direction. The Fourier transform may be, for example, a fast Fourier transform (FFT) or a discrete Fourier transform (DFT). In each transmission cycle c, the Fourier transform unit 314 generates N×N Fourier-transformed signals S mov The distance bin extracting unit 315 outputs (r, g, h, c) to the distance bin extracting unit 315 and the digital beam forming unit 317. r is a variable for identifying a distance bin from the heartbeat signal measuring device. r=1, . . . , R. R is an integer equal to or greater than 2.

[0024] The range bin extractor 315 receives N×N Fourier transformed signals S mov Get (r,g,h,c). The range bin extractor 315 extracts the Fourier transformed signal S mov Based on the complex amplitude of the signal, distance bin r' in which the subject may exist is extracted. r' is a variable for identifying the extracted distance bins, and is R' integers between 1 and R. R' is an integer less than or equal to R. Distance bin extraction unit 315 outputs distance bins r' in which the subject may exist to digital beam forming unit 317.

[0025] The digital beam forming unit 317 converts the Fourier transformed signal S mov (r, g, h, c) is obtained from the Fourier transform unit 314, and the distance bin r' in which the subject may exist is obtained from the distance bin extraction unit 315. The digital beam forming unit 317 converts the Fourier transformed signal S movDigital beamforming is performed in the azimuth and elevation directions in order for distance bin r' where a subject corresponding to (r, g, h, c) may exist, and a digital beamformed signal BF(r', e, a, c) is calculated. Here, e is a variable for identifying an orientation bin in the elevation direction. e = 1, . . . E. E is an integer greater than or equal to 2. a is a variable for identifying an orientation bin in the azimuth direction, and a = 1, . . . A. A is an integer greater than or equal to 2. The digital beamforming unit 317 outputs the digital beamformed signal BF(r', e, a, c) to the orientation bin extraction unit 316 and the measurement unit 32.

[0026] The orientation bin extraction unit 316 acquires a digital beamformed signal BF(r', e, a, c) from the digital beamforming unit 317. Then, based on the complex amplitude of the digital beamformed signal BF, the orientation bin extraction unit 316 extracts distance bins, orientation bins in the azimuth direction, and orientation bins (i, j, k) in the elevation direction where a subject may be present. Here, (i, j, k) is a set of L integers, where i is an integer included in r', j is an integer between 1 and E, and k is an integer between 1 and A. The orientation bin extraction unit 316 outputs the set of L integers (i, j, k) consisting of distance bins, orientation bins in the azimuth direction, and orientation bins in the elevation direction where a subject may be present to the measurement unit 32.

[0027] The measurement unit 32 generates L phase signals P(l,c) based on the digital beamformed signal BF(r',e,a,c) and L sets of integers (i,j,k) consisting of distance bins, azimuth direction bins, and elevation direction bins, removes components to be removed that are derived from the breathing or body movement of the subject from the generated L phase signals P(l,c), and derives a phase signal (heartbeat signal P''(l,m,c) from which the components to be removed have been removed based on the evaluation result of the periodicity of the signal. heart By selecting (c), the subject's heart rate signal P heart (c) is measured.

[0028] FIG. 2 is a block diagram showing an example configuration of the measurement unit 32. As shown in FIG. 2, the measurement unit 32 is configured with a phase calculation unit 321, a phase unwrapping unit 322, a trend removal unit 323, and a heartbeat signal selection unit 324. The phase calculation unit 321 acquires a digitally beamformed signal BF(r', e, a, c) from the digital beamforming unit 317 and acquires L sets of integers (i, j, k) consisting of distance bins, azimuth direction bins, and elevation direction bins in which the subject may be present, from the direction bin extraction unit 316. The phase calculation unit 321 calculates L phase signals P(l, c) corresponding to the acquired sets of L integers (i, j, k) from the acquired signal BF(r', e, a, c). Here, l is a variable for identifying the acquired sets of L integers, and l = 1, . . . , L. The phase calculation unit 321 outputs L phase signals P(l,c) to the phase unwrapping unit 322.

[0029] The phase unwrapping unit 322 acquires L phase signals P(l,c) from the phase calculation unit 321. The phase unwrapping unit 322 performs phase unwrapping processing on each of the L phase signals P(l,c) to calculate L phase-unwrapped phase signals P'(l,c). The phase unwrapping unit 322 outputs the L phase-unwrapped phase signals P'(l,c) to the trend removal unit 323.

[0030] The trend removal unit 323 obtains L phase-unwrapped phase signals P'(l,c) from the phase unwrapping unit 322. The trend removal unit 323 calculates a trend component P'(l,c) for each of the L phase-unwrapped phase signals P'(l,c) using an m-th degree polynomial. trend Calculate (m, c), where m is a variable for identifying the degree of the polynomial, and is M integers equal to or greater than 1. M is an integer equal to or greater than 2.

[0031] The trend remover 323 extracts the trend component P from the phase-unwrapped phase signal P'. trendto calculate L×M phase signals P″(l, m, c) from which the trend components have been removed. The trend removing unit 323 outputs the L×M phase signals P″(l, m, c) from which the trend components have been removed to the heartbeat signal selecting unit 324.

[0032] The heartbeat signal selection unit 324 acquires L×M phase signals P″(l, m, c) from which the trend component has been removed from the trend removal unit 323. The heartbeat signal selection unit 324 calculates an evaluation value X based on the level of periodicity of each of the L×M phase signals P″(l, m, c) from which the trend component has been removed. The heartbeat signal selection unit 324 selects the phase signal with the maximum evaluation value X from the L×M phase signals P″(l, m, c) from which the trend component has been removed. The phase signal that maximizes this evaluation value X is the heartbeat signal P heart That is, by selecting the phase signal with the maximum evaluation value X from the L×M phase signals P''(l, m, c) from which the trend component has been removed, the heartbeat signal P heart (c) is measured. The heartbeat signal selection unit 324 selects the heartbeat signal P heart (c) is output to the output unit 33.

[0033] The output unit 33 receives the heartbeat signal P from the heartbeat signal selection unit 324. heart The output unit 33 acquires the heartbeat signal P heart The function of the output unit 33 may be provided in the measurement unit 32. In this case, the heartbeat signal measurement device 3 does not need to be provided with the output unit 33.

[0034] Next, a heartbeat signal measuring method according to the first embodiment will be described. FIG. 3 is a flowchart showing the heartbeat signal measuring method according to the first embodiment. The acquisition unit 31 acquires a set of distance bins, azimuth direction direction bins, and elevation direction direction bins in which a living body may be present, calculated based on the received signals of radio waves irradiated to the subject and reflected by the subject, and signals digitally beamformed (two-dimensional digital beamformed) in the azimuth direction and elevation direction in order for the distance bins (step ST1).

[0035] The measurement unit 32 generates phase signals based on the digital beamformed signal, distance bins, azimuth direction direction bins, and elevation direction direction bins, removes trend components derived from the subject's breathing or body movement from the generated phase signals, and measures the subject's heart rate signal by selecting a phase signal from the phase signals from which the trend components have been removed based on the evaluation results of the signal periodicity (step ST2).

[0036] The output unit 33 receives the heartbeat signal P from the heartbeat signal selection unit 324. heart (c) is acquired, and the acquired heart rate signal P heart (c) is output to the outside (step ST3). By performing the series of processes shown in FIG. 3, the heartbeat signal measuring device 3 can measure a heartbeat signal from which components derived from the breathing or body movement of the subject have been removed.

[0037] Next, a pre-processing of the heartbeat signal measuring method according to the first embodiment, in which the data acquired by the acquiring unit 31 is generated, will be described. The signal generator 242 in the signal transmission unit 24 provided in the radar sensor unit 2 generates an up-chirp signal or a down-chirp signal as a transmission signal, for example, according to a frequency modulated continuous wave (FMCW) method or a fast-chirp modulation (FCM) method.

[0038] Fig. 4 is a graph showing the chirp signal for each transmission cycle. For example, as shown in Fig. 4, the signal generator 242 repeats radio wave transmission for hits of 1 to Q in each transmission cycle c (c = 1,...,C). Furthermore, within each hit, the signal generator 242 repeatedly generates up-chirp signals Tx(n) for the number of antennas 21-1 to 21-N. Therefore, the signal generator 242 generates a total of N x Q x C up-chirp signals Tx(n). Note that in the example shown in Fig. 4, N = 3.

[0039] The signal generator 242 up-converts the frequency of the generated up-chirp signal Tx(n) (n=1, . . . , N) to a signal in a high frequency band, and outputs the up-converted signal as a transmission signal Tx'(n) to the output destination selection unit 241. The high frequency band is, for example, a millimeter wave band of about 30 to 300 GHz.

[0040] The output destination selection unit 241 obtains a transmission signal Tx'(n) (n=1, . . . , N) in each transmission cycle c (c=1, . . . , C) and each hit q (q=1, . . . , Q) from the signal generator 242. The output destination selection unit 241 outputs the transmission signal Tx'(n) to the circulator 22-n, among the N circulators 22-1 to 22-N, that is connected to the antenna 21-n that is next to radiate a transmission wave.

[0041] For example, if the antenna 21-n whose turn it is to radiate a transmission wave next is antenna 21-1, the output destination selection unit 241 outputs the transmission signal Tx'(1) to the circulator 22-1, and if the antenna 21-n whose turn it is to radiate a transmission wave next is antenna 21-2, the output destination selection unit 241 outputs the transmission signal Tx'(2) to the circulator 22-2. Furthermore, for example, if the antenna 21-n whose turn it is to radiate the transmission wave next is the antenna 21-N, the output destination selection unit 241 outputs the transmission signal Tx'(N) to the circulator 22-N.

[0042] Upon receiving the transmission signal Tx'(n) from the output destination selection unit 241, the circulator 22-n (n=1, . . . , N) outputs the transmission signal Tx'(n) to the antenna 21-n. When the antenna 21-n (n = 1,...,N) receives a transmission signal Tx'(n) from the circulator 22-n, it radiates a transmission wave, which is a radio wave related to the transmission signal Tx'(n), into the space in which the target object is present. The transmission wave radiated from the antenna 21-n is reflected by the target object. That is, the transmission wave radiated from the antenna 21-n is reflected not only by the person being measured but also by the walls and the like that form the space. The wave reflected by the person being measured may further be reflected by the walls and the like of the room in which the person being measured is present.

[0043] In each transmission cycle c (c=1,...,C) and each hit q (q=1,...,Q), one antenna out of the N antennas 21-1 to 21-N sequentially emits a transmission wave into space N times. Therefore, each of the antennas 21-1 to 21-N receives a reflected wave N x Q times in each transmission cycle c. The antenna 21-n (n=1,...,N) outputs a received signal including a wave reflected by a target object to the circulator 22-n. The circulator 22-n (n=1,...,N) outputs the received signal output from the antenna 21-n to the signal receiving unit 23-n.

[0044] The signal receiving unit 23-n (n = 1, . . . , N) performs reception processing on each of the N × Q reception signals output from the circulator 22-n in each transmission cycle c (c = 1, . . . , C). As reception processing on the reception signals, the signal receiving unit 23-n performs, for example, processing to down-convert the frequency of the reception signal to a frequency in the intermediate frequency band and processing to convert the frequency-converted reception signal from an analog signal to a digital signal. In each transmission cycle c, the signal receiving unit 23-n outputs each of N × Q digital signals S(t, g, h, q, c) to the heartbeat signal measuring device 3. As a result, in each transmission cycle c (c = 1, . . . , C), a total of N × N × Q (= G × H × Q) signals S(t, g, h, q, c) are acquired by the heartbeat signal measuring device 3 from the signal receiving units 23-1 to 23-N.

[0045] Next, detailed processing of the heartbeat signal measuring method according to the first embodiment will be described. FIG. 5 is a flowchart showing detailed processing of step ST1 in FIG. 3, and shows each process performed by the signal acquisition unit 311, pre-processing unit 312, stationary object suppression unit 313, Fourier transform unit 314, distance bin extraction unit 315, azimuth bin extraction unit 316, and digital beamforming unit 317 included in the acquisition unit 31.

[0046] The signal acquiring unit 311 acquires N×N×Q signals S(t, g, h, q, c) from the signal receiving units 23-1 to 23-N in each transmission cycle c (c=1, . . . , C) (step ST1-1). The signal acquiring unit 311 outputs the N×N×Q signals S(t, g, h, q, c) to the pre-processing unit 312 in each transmission cycle c.

[0047] The preprocessing unit 312 acquires N×N×Q signals S(t, g, h, q, c) from the signal acquisition unit 311 in each transmission cycle c (c=1, , C), and sums up all hits q (q=1, , Q) for the signals S(t, g, h, q, c) (step ST1-2). This summation produces a preprocessed signal S pre(t,g,h,c) is calculated. If the time interval between hits is very short, the signal S pre By summing (t,g,h,c) between hits, the signal-to-noise ratio (SNR) of the signal can be improved. The preprocessing unit 312 outputs the preprocessed signal S pre (t, g, h, c) is output to the stationary object suppression unit 313.

[0048] The stationary object suppression unit 313 receives N×N×Q preprocessed signals S pre (t, g, h, c). The stationary object suppression unit 313 obtains N×N×Q pre-processed signals S pre For (t, g, h, c), the stationary object signal S averaged over all cycles c (c = 1, , C) is sta (t, g, h). The stationary object suppression unit 313 calculates the pre-processed signal S pre (t,g,h,c) to S sta The signal S obtained by subtracting (t, g, h) mov (t, g, h, c) are calculated (step ST1-3). Since the signals reflected by stationary objects do not change between cycles, unnecessary signals reflected by stationary objects can be suppressed by subtracting the stationary object reception data averaged between cycles from the preprocessed reception data. The stationary object suppression unit 313 receives the signal S mov (t, g, h, c) is output to the Fourier transform unit 314.

[0049] In each transmission cycle c, the Fourier transform unit 314 converts N×N signals S mov Each of (t, g, h, c) is Fourier transformed in the time direction (step ST1-4). The Fourier transform may be, for example, a fast Fourier transform (FFT) or a discrete Fourier transform (DFT). The Fourier transform unit 314 converts N×N Fourier-transformed signals Smov (r, g, h, c) is output to the distance bin extraction unit 315 and the digital beam forming unit 317. r is a variable for identifying a distance bin from the heart rate signal measuring device 3, where r=1, . . . , R. R is an integer equal to or greater than 2.

[0050] The range bin extractor 315 extracts N×N Fourier transformed signals S mov (r, g, h, c). The distance bin extractor 315 extracts the Fourier transformed signal S mov Based on the complex amplitude of the signal, distance bins r' in which the subject may exist are extracted (step ST1-5), where r' is an R'-number of integers between 1 and R. For example, the range bin extractor 315 extracts the Fourier transformed signal S mov Complex amplitude S of (r,g,h,c) abs Calculate (r, g, h, c) and calculate the complex amplitude S abs (r, g, h, c) and the antenna 21-g that emitted all the transmitted waves, the antenna 21-h that received the reflected waves, and the distance information signal S NCI Calculate (r). Next, the distance bin extraction unit 315 extracts the distance information signal S NCI A peak whose intensity is equal to or greater than a certain threshold is selected for (r), as well as bins before and after the peak, and R' distance bins are extracted. The distance bin extraction unit 315 outputs the extracted distance bin r′ in which the subject may exist to the digital beam forming unit 317 .

[0051] The digital beam forming unit 317 converts the Fourier transformed signal S mov (r, g, h, c) is obtained from the Fourier transform unit 314, and the distance bin r' in which the subject may exist is obtained from the distance bin extraction unit 315. Then, the digital beam forming unit 317 converts the Fourier transformed signal S movDigital beamforming is performed in the azimuth and elevation directions in order for distance bin r' among (r, g, h, c) where a subject may be present (step ST1-6). This calculates a digital beamformed signal BF(r', e, a, c). e is a variable for identifying an azimuth bin in the elevation direction. e = 1, . . . E. E is an integer equal to or greater than 2. a is a variable for identifying an azimuth bin in the azimuth direction. a = 1, . . . A. A is an integer equal to or greater than 2.

[0052] For example, the operation when R'=3 and r'=r'1, r'2, r'3 will be described. FIG. 6 is a schematic diagram showing an overview of digital beamforming. First, the digital beam forming unit 317 converts the Fourier transformed signal S mov Two-dimensional beamforming is performed for the (r'1, g, h, c) signals for each cycle using DBF (Digital Beam Forming). The two-dimensional direction is the azimuth direction and the elevation direction. However, one-dimensional beamforming may be used depending on the arrangement of the transmitting and receiving antennas. Two-dimensional beamforming using DBF is also performed for r'2 and r'3 in the same way. As a result, C signals each are obtained for r'1, r'2, and r'3, for a total of 3 × C two-dimensional digital beamformed signals. Note that the digital beamforming process may also be performed using other methods such as the Capon method. The digital beam forming unit 317 outputs the digital beam formed signal BF(r', e, a, c) to the azimuth bin extracting unit 316 and the measuring unit 32, respectively.

[0053] The azimuth bin extraction unit 316 acquires the digital beamformed signal BF(r′, e, a, c) from the digital beamforming unit 317 . Next, the azimuth bin extraction unit 316 acquires a set (i, j, k) of distance bins, azimuth bins, and elevation bins where the subject may be present, based on the complex amplitude of the acquired digital beamformed signal BF (step ST1-7), where (i, j, k) is a set of L integers, i is an integer included in r', j is an integer between 1 and E, and k is an integer between 1 and A.

[0054] An example where R'=3 and r'=r'1, r'2, r'3 will be described. The azimuth bin extraction unit 316 first extracts a BF (r', e, a, c) from the digitally beamformed signal BF (r', e, a, c) by adding up the complex amplitudes of the digitally beamformed signal BF (r'1, e, a, c) corresponding to r'1 for all cycles c. abs Calculate (e, a). Next, the orientation bin extraction unit 316 extracts the calculated BF abs The orientation bin extraction unit 316 extracts pairs of e and a for which the complex amplitude for (e, a) is equal to or greater than a certain threshold. Similarly, the orientation bin extraction unit 316 extracts pairs of e and a for r'2 and r'3, and calculates L pairs of integers (i, j, k) by combining the pairs of e and a corresponding to r'1, r'2, and r'3, respectively. The azimuth direction bin extraction unit 316 outputs to the measurement unit 32 L sets of integers (i, j, k) of distance bins, azimuth direction bins, and elevation direction bins in which a subject may be present.

[0055] Next, the detailed operation of the measurement unit 32 will be described. FIG. 7 is a flowchart showing the detailed processing of step ST2 in FIG. The measurement unit 32 acquires L sets of distance bins, azimuth direction bins, and elevation direction bins in which a living body may exist, calculated based on the complex amplitude of the digital beamformed signal, from the direction bin extraction unit 316 (step ST2-1). Next, the measurement unit 32 selects phase signals from the digital beamformed signal based on phase changes of the signals corresponding to the L sets of distance bins, azimuth direction bins, and elevation direction bins in which a living body may exist, and measures the selected phase signals as heartbeat signals (step ST2-2).

[0056] FIG. 8 is a flowchart showing the detailed processing of step ST2-2 in FIG. The phase calculation unit 321 calculates the phase of each of the signals corresponding to the L sets of extracted distance bins, azimuth direction bins, and elevation direction bins from among the digital beamformed signals (step ST2-2-1). For example, the phase calculation unit 321 acquires a digital beam-formed signal BF(r', e, a, c) from the digital beam forming unit 317, and acquires L sets of integers (i, j, k) of distance bins, azimuth direction direction bins, and elevation direction direction bins where the subject may be present from the direction bin extraction unit 316. The phase calculation unit 321 obtains L biometric information signals V(l, c) corresponding to the L sets of integers (i, j, k) from BF(r', e, a, c). Here, l is a variable for identifying the L sets of integers (i, j, k), and l = 1, 2, . . . , L.

[0057] The phases of the L number of biological information signals V(l,c) change between cycles due to the subject's body movements, breathing, and fluctuations on the body surface caused by heartbeat. Fig. 9 is a diagram showing a complex plane on which the real and imaginary parts of a bioinformation signal are plotted, and shows the phase change of the bioinformation signal V, which is obtained by plotting the real and imaginary parts of the bioinformation signal V(l,c) on the complex plane over cycle c. As shown in Fig. 9, the real and imaginary parts of the bioinformation signal V change in a circular manner on the complex plane. The center of the circle may deviate from the origin on the complex plane due to the influence of unnecessary components other than the reflected signal from the target subject.

[0058] If the phase is calculated while the center of the circle is shifted from the origin on the complex plane, the correct phase change cannot be calculated. Therefore, the measurement unit 32 performs circle fitting on the biometric information signal V(l,c) to estimate the center of the circle. The estimated center of the circle is corrected to be the origin on the complex plane. By setting the center coordinate of the estimated circle to DC, correction is performed to make the center of the circle the origin on the complex plane according to the following equations (1) and (2). V' represents the corrected biometric information signal, Real(A) represents the real part of the complex number A, and Imag(A) represents the imaginary part of the complex number A. The circle fitting process may use a circle fitting method such as Kasa fit, Pratt fit, Taubin fit, or Hyper fit. TIFF0007825797000001.tif16166

[0059] Next, the phase calculation unit 321 calculates L phase signals P(l,c) for the corrected biological information signal V'(l,c) using an arctangent demodulation method (AD method) according to the following equation (3). The phase calculation unit 321 outputs the L phase signals P(l,c) to the phase unwrapping unit 322. TIFF0007825797000002.tif13166

[0060] The phase unwrapping unit 322 acquires L phase signals P(l,c) from the phase calculation unit 321. The phase calculation unit 321 performs phase unwrapping on each of the L phase signals P(l,c) to calculate L phase-unwrapped phase signals P'(l,c) (step ST2-2-2). A publicly known technique may be used for the phase unwrapping.

[0061] 10A, 10B, and 10C are waveform diagrams showing the phase-unwrapped phase signal, illustrating the relationship of phase with respect to cycle number. The phase signals shown in FIGS. 10A, 10B, and 10C are signals calculated from different sets of range bins and azimuth bins, respectively. As shown in FIGS. 10A, 10B, and 10C, the phase-unwrapped phase signals calculated from different sets of range bins and azimuth bins each have a different waveform. The phase unwrapping unit 322 outputs the phase-unwrapped phase signal P'(l,c) to the trend removal unit 323.

[0062] The trend removal unit 323 acquires L phase-unwrapped phase signals P'(l,c) from the phase unwrapping unit 322. In addition to the phase change due to the heartbeat, the phase-unwrapped phase signal P'(l,c) also has a trend component including a phase change due to body movement or respiration superimposed thereon. The trend removal unit 323 extracts the trend component P'(c) from the l-th phase signal P'(c) of the L phase-unwrapped phase signals P'(l,c) by using an m-th polynomial. trend (m, c) is calculated (step ST2-2-3), where m is M integers equal to or greater than 1. A known technique may be used to calculate the trend component using a polynomial.

[0063] The trend remover 323 extracts the phase signals P′(c) from the phase signals P′(c) trend(m,c) are subtracted from each other to calculate M phase signals P''(m,c) from which the trend component has been removed. The trend component is similarly removed from L phase signals P'(l,c) to calculate L × M phase signals P''(l,m,c) from which the trend component has been removed.

[0064] 11A, 11B, and 11C are waveform diagrams showing the phase signal and trend component before the trend component is removed. FIG. 11A shows the phase signal P' before the trend component is removed when the polynomial degree m is 3, as a solid line, and the calculated trend component is shown together with this phase signal P', as a dashed line. Similarly, FIG. 11B shows the phase signal P' before the trend component is removed when m is 10, as a solid line, and the calculated trend component is shown together with this phase signal P', as a dashed line. Furthermore, FIG. 11C shows the phase signal P' before the trend component is removed when m is 20, as a solid line, and the calculated trend component is shown together with this phase signal P', as a dashed line.

[0065] As shown in FIGS. 11A, 11B, and 11C, the waveform of the trend component calculated varies depending on the degree m of the polynomial. Therefore, the phase signal P'' from which the trend component has been removed also varies depending on the degree m of the polynomial. The trend removal unit 323 outputs L×M phase signals P''(l, m, c) from which the trend component has been removed to the heartbeat signal selection unit 324.

[0066] The heartbeat signal selection unit 324 acquires L×M phase signals P″(l, m, c) from which the trend components have been removed from the trend removal unit 323. The phase signals P″(l, m, c) from which the trend components have been removed have different waveforms depending on the set (i, j, k) of distance bins, azimuth direction bins, and elevation direction bins, or the order m of the polynomial used when the trend components were removed.

[0067] The heartbeat signal selection unit 324 estimates the phase signal from which the trend component has been removed, which is capable of measuring the heartbeat signal with the highest accuracy, from among the L×M phase signals P″(l, m, c) from which the trend component has been removed and which have mutually different waveforms, and selects the estimation result. The heartbeat signal selection unit 324 calculates the autocorrelation function expressed by the following formula (4) for each of the L×M phase signals P″(l, m, c) from which the trend component has been removed. Here, the phase signal from which the trend component has been removed is denoted by x c Also, the x bar is x c is the average value of , and u is the number of lags. TIFF0007825797000003.tif15166

[0068] 12A and 12B are diagrams showing a highly periodic phase signal and an autocorrelation function from which the trend component has been removed. In FIG. 12A, the horizontal axis represents the cycle number, and the vertical axis represents the phase. The phase signal shown in FIG. 12A is the waveform of a highly periodic phase signal from which the trend component has been removed. FIG. 12B shows the characteristics of the autocorrelation function with respect to the number of lags.

[0069] 13A and 13B are diagrams showing a phase signal with low periodicity from which the trend component has been removed and an autocorrelation function. In FIG. 13A, the horizontal axis represents the cycle number, and the vertical axis represents the phase. The phase signal shown in FIG. 13A is the waveform of a phase signal with low periodicity from which the trend component has been removed. FIG. 13B shows the characteristics of the autocorrelation function with respect to the number of lags.

[0070] The phase signal from which the trend component has been removed shown in Fig. 12A and the phase signal from which the trend component has been removed shown in Fig. 13A have different waveforms, and the characteristics of the autocorrelation function calculated from the phase signals are different, as shown in Fig. 12B and Fig. 13B. The height of the peak of the autocorrelation function increases as the periodicity of the signal increases. Because the phase signal shown in Fig. 12A has high periodicity, the height of the peak of the autocorrelation function corresponding to the phase signal in Fig. 12A increases, as shown in Fig. 12B. On the other hand, the phase signal shown in FIG. 13A is a signal with lower periodicity than the phase signal shown in FIG. 12A, and therefore the height of the corresponding peak of the autocorrelation function shown in FIG. 13B is also lower.

[0071] The heartbeat signal selection unit 324 acquires α peak values ​​for each of the calculated L×M autocorrelation functions in ascending order of the coefficient of the autocorrelation function or in descending order of the lag number, calculates the average value, and calculates a value Y indicating the periodicity height, where α is an integer equal to or greater than 1. Also, a value Z is calculated by multiplying the degree m of the polynomial used to remove the trend component by a coefficient β. Here, β is a value equal to or greater than 0. Using the calculated Y and Z, an evaluation value X is calculated according to the following formula (5). The reason why the value Z calculated based on the degree m of the polynomial is subtracted from the value Y indicating the level of periodicity is that if the degree m of the polynomial used to remove the trend component becomes large, there is a high possibility that components derived from the heart rate will be removed. TIFF0007825797000004.tif11166

[0072] The heartbeat signal selection unit 324 selects the phase signal P''(c) from which the trend component has been removed, which maximizes the evaluation value X, and outputs the heartbeat signal P heart If the periodicity increases due to components derived from breathing, and the evaluation value increases, there is a possibility that the breathing signal will be selected as the heart rate signal. Therefore, since the period of a heartbeat is generally shorter than the period caused by breathing, the heartbeat signal selection unit 324 does not need to select a signal as a heartbeat signal if the set number of α peaks is not obtained for the calculated autocorrelation function, or if the period is calculated from the lag value of the peaks of the calculated autocorrelation function and the calculated period is equal to or greater than a certain value. heart (c) is output to the output unit 33.

[0073] The output unit 33 receives the heartbeat signal P from the heartbeat signal selection unit 324. heart The output unit 33 acquires the heartbeat signal P heart(c) is output externally.

[0074] Next, a hardware configuration for realizing the functions of the heartbeat signal measuring device 3 will be described. The functions of the acquisition unit 31, measurement unit 32, and output unit 33 included in the heartbeat signal measuring device 3 are realized by a processing circuit. That is, the heartbeat signal measuring device 3 includes a processing circuit for executing the processes of steps ST1 to ST3 shown in Fig. 3. The processing circuit may be dedicated hardware, or may be a CPU (Central Processing Unit) that executes a program stored in a memory.

[0075] Fig. 14A is a block diagram showing a hardware configuration that realizes the functions of the heartbeat signal measuring device 3. Fig. 14B is a block diagram showing a hardware configuration that executes software that realizes the functions of the heartbeat signal measuring device 3. In Figs. 14A and 14B, an acquisition unit 31 acquires data from the radar sensor unit 2 via an input interface 100. An output unit 33 outputs the data to the outside via an output interface 101.

[0076] 14A, the processing circuit 102 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. The functions of the acquisition unit 31, the measurement unit 32, and the output unit 33 included in the heartbeat signal measurement device 3 may be realized by separate processing circuits, or these functions may be realized together by a single processing circuit.

[0077] 14B, the functions of the acquisition unit 31, measurement unit 32, and output unit 33 included in the heartbeat signal measurement device 3 are realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 104.

[0078] The processor 103 reads and executes programs stored in the memory 104 to implement the functions of the acquisition unit 31, the measurement unit 32, and the output unit 33 included in the heartbeat signal measuring device 3. For example, the heartbeat signal measuring device 3 includes the memory 104 for storing a program that, when executed by the processor 103, results in the execution of steps ST1 to ST3 shown in FIG. 3 . These programs cause a computer to execute the procedures or methods of the processes performed by the acquisition unit 31, the measurement unit 32, and the output unit 33. The memory 104 may be a computer-readable storage medium that stores programs for causing a computer to function as the acquisition unit 31, the measurement unit 32, and the output unit 33.

[0079] Memory 104 may be, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically-EPROM) (registered trademark), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, etc.

[0080] Some of the functions of the acquisition unit 31, measurement unit 32, and output unit 33 included in the heartbeat signal measurement device 3 may be realized by dedicated hardware, and other functions may be realized by software or firmware. For example, the functions of the acquisition unit 31 and the output unit 33 may be realized by a processing circuit 102 that is dedicated hardware, and the function of the measurement unit 32 may be realized by the processor 103 reading and executing a program stored in the memory 104. In this way, the processing circuit can realize the above functions by hardware, software, firmware, or a combination of these.

[0081] As described above, the heartbeat signal measurement device 3 according to the first embodiment includes an acquisition unit 31 that acquires sets of distance bins, azimuth direction bins, and elevation direction bins in which a living body may be present, and signals digitally beamformed in the azimuth direction and elevation direction for the distance bins in sequence, and a measurement unit 32 that generates phase signals based on the digital beamformed signals, the distance bins, the azimuth direction bins, and the elevation direction bins, removes components to be removed that are due to the breathing or body movement of the subject from the generated phase signals, and selects phase signals from the phase signals from which the components to be removed have been removed based on an evaluation result of the periodicity of the signals, thereby measuring the heartbeat signal of the subject. Heartbeats are generally periodic, and fluctuations in the subject's body surface are also periodic. Therefore, the heartbeat signal measuring device 3 can measure a heartbeat signal from which components derived from the breathing or body movement of the subject have been removed by selecting a phase signal from which highly periodic trend components have been removed.

[0082] In the heartbeat signal measuring device 3 according to the first embodiment, the measuring unit 32 measures the heartbeat signal based on phase changes of phase signals corresponding to a plurality of sets of acquired distance bins, azimuth direction bins, and elevation direction bins among the digital beamformed signals. This allows the heartbeat signal measuring device 3 to select phase signals from which highly periodic trend components have been removed, thereby enabling measurement of heartbeat signals from which components derived from the subject's breathing or body movement have been removed.

[0083] In the heartbeat signal measuring device 3 according to the first embodiment, the measuring unit 32 calculates phase signals of each of the beamformed signals corresponding to a plurality of sets of the acquired distance bin, azimuth direction bin, and elevation direction bin, performs phase unwrapping on each of the calculated phase signals, calculates a phase signal from which the trend component has been removed using a polynomial for removing a trend component derived from the breathing or body movement of the subject for each of the phase signals from which the phase unwrapping has been performed, calculates an evaluation value relating to the height of the periodicity for each of the phase signals from which the trend component has been removed based on the height of the peak of the autocorrelation function, and measures the heartbeat signal by selecting the phase signal with the largest evaluation value from the plurality of phase signals from which the trend component has been removed. This allows the heartbeat signal measuring device 3 to select a phase signal from which highly periodic trend components have been removed, making it possible to measure a heartbeat signal from which components derived from the subject's breathing or body movement have been removed.

[0084] The heartbeat signal measurement method according to the first embodiment includes the steps of: (1) acquiring, by an acquisition unit 31, sets of distance bins, azimuth direction bins, and elevation direction bins in which a living body may be present, calculated based on received signals of radio waves irradiated to the subject and reflected by the subject, and acquiring signals beamformed in the azimuth and elevation directions for the distance bins in order; and (2) measuring, by a measurement unit 32, generating phase signals based on the beamformed signals, the distance bins, the azimuth direction bins, and the elevation direction bins, removing components derived from the subject's respiration or body movement from the generated phase signals, and selecting phase signals from the phase signals from which the components to be removed have been removed based on an evaluation result of the signal periodicity, thereby measuring the subject's heartbeat signal. By performing the heartbeat signal measurement method, the heartbeat signal measurement device 3 can measure the heartbeat signal from which the components derived from the subject's respiration or body movement have been removed.

[0085] Embodiment 2 Fig. 15 is a block diagram showing an example of the configuration of a heartbeat signal measurement system 1A according to embodiment 2. In Fig. 15, the heartbeat signal measurement system 1A is a system that measures the heartbeat signal of a person being measured using radar signals, and includes a radar sensor unit 2 and a heartbeat signal measurement device 3A. The radar sensor unit 2 includes N antennas 21-1, 21-2, ..., 21-N, N circulators 22-1, 22-2, ..., 22-N, N signal receiving units 23-1, 23-2, ..., 23-N, and a signal transmitting unit 24. N is an integer equal to or greater than 2.

[0086] Heartbeats are generally periodic, and fluctuations in the body surface of the subject are also periodic. Therefore, the heartbeat signal measuring device 3A measures the heartbeat signal with high accuracy by selecting a phase signal that has passed through a high-pass filter with high periodicity. The heartbeat signal measuring device 3A includes an acquiring unit 31, a measuring unit 32A, and an output unit 33. For example, the heartbeat signal measuring device 3A is realized by a computer. A memory included in the computer stores programs constituting information processing applications for realizing the functions of the acquiring unit 31, the measuring unit 32A, and the output unit 33. A processor included in the computer executes the information processing application read from the memory, thereby realizing the functions of the acquiring unit 31, the measuring unit 32A, and the output unit 33.

[0087] 16 is a block diagram showing an example of the configuration of the measurement unit 32 A. As shown in FIG. 16, the measurement unit 32 A includes a phase calculation unit 321, a phase unwrapping unit 322, a heartbeat signal selection unit 324, and a high-pass filter unit 325. The phase calculation unit 321 acquires the digital beamformed signal BF(r', e, a, c) from the digital beamforming unit 317, and acquires L sets of integers (i, j, k) consisting of distance bins, azimuth direction bins, and elevation direction bins where a subject may be present, from the direction bin extraction unit 316. The phase calculation unit 321 calculates L phase signals P(l, c) corresponding to the acquired sets of L integers (i, j, k) from the acquired signal BF(r', e, a, c). l is a variable for identifying the acquired sets of L integers, and l = 1, . . . , L. The phase calculation unit 321 outputs the L phase signals P(l, c) to the phase unwrapping unit 322.

[0088] The phase unwrapping unit 322 acquires L phase signals P(l,c) from the phase calculation unit 321. The phase unwrapping unit 322 performs phase unwrapping processing on each of the L phase signals P(l,c) to calculate L phase-unwrapped phase signals P'(l,c). The phase unwrapping unit 322 outputs the L phase-unwrapped phase signals P'(l,c) to the high-pass filter unit 325.

[0089] The high-pass filter unit 325 performs high-pass filtering with a cutoff frequency m' on each of the L phase signals after phase unwrapping to calculate M' phase signals from which low-frequency components have been removed. The heartbeat signal selection unit 324 calculates an evaluation value relating to the height of periodicity for each of the M' phase signals from which low-frequency components have been removed based on the height of the peak of the autocorrelation function, and measures the heartbeat signal by selecting the phase signal with the maximum evaluation value from the M' phase signals from which low-frequency components have been removed.

[0090] Next, a heartbeat signal measuring method according to the second embodiment will be described. FIG. 17 is a flowchart showing a heartbeat signal measuring method according to the second embodiment, illustrating a series of processes corresponding to step ST2-2 in FIG. The phase calculation unit 321 calculates the phase of each of the signals corresponding to the L sets of extracted distance bins, azimuth direction bins, and elevation direction bins from among the digital beamformed signals (step ST2A-2-1). The phase unwrapping unit 322 acquires L phase signals P(l,c) from the phase calculation unit 321. The phase calculation unit 321 performs phase unwrapping on each of the L phase signals P(l,c) and calculates L phase-unwrapped phase signals P'(l,c) (step ST2A-2-2).

[0091] The high-pass filter unit 325 acquires L phase-unwrapped phase signals P'(l,c) from the phase unwrapping unit 322. The phase-unwrapped phase signals P'(l,c) contain superimposed low-frequency components including phase changes due to body movement or breathing, in addition to phase changes due to heartbeats. The high-pass filter unit 325 removes low-frequency components from the l-th phase signal P'(c) among the L phase-unwrapped phase signals P'(l,c) using a high-pass filter with a cutoff frequency of m' Hz, and calculates M' high-pass filtered phase signals P''(m',c) (step ST2A-2-3). A known technique may be used for the high-pass filter. The high-pass filter unit 325 similarly removes low-frequency components from each of the L phase signals P'(l,c) to calculate LxM high-pass filtered phase signals P''(l,m',c).

[0092] 18A, 18B, and 18C are waveform diagrams showing the phase signal and low-frequency components before the low-frequency components are removed. FIG. 18A shows the phase signal P' before the low-frequency components are removed when the cutoff frequency m' is 0.3, as a solid line, and the removed low-frequency components are shown together with this phase signal P', as a dashed line. Similarly, FIG. 18B shows the phase signal P' before the low-frequency components are removed when m' is 1.2, as a solid line, and the low-frequency components are shown together with this phase signal P', as a dashed line. Furthermore, FIG. 18C shows the phase signal P' before the low-frequency components are removed when m' is 1.8, as a solid line, and the low-frequency components are shown together with this phase signal P', as a dashed line.

[0093] As shown in FIGS. 18A, 18B, and 18C, the waveform of the low-frequency components calculated varies depending on the cutoff frequency m'. Therefore, the waveform of the phase signal P'' from which the low-frequency components have been removed also varies depending on the cutoff frequency m'. The high-pass filter unit 325 outputs L×M' phase signals P''(l, m', c) from which the low-frequency components have been removed to the heartbeat signal selection unit 324.

[0094] The heartbeat signal selection unit 324 acquires L×M' phase signals P''(l, m', c) from which low frequency components have been removed, from the high-pass filter unit 325. The L×M' phase signals P''(l, m', c) from which low frequency components have been removed have different waveforms depending on the set (i, j, k) of distance bins, azimuth direction azimuth direction bins, and elevation direction azimuth direction bins, or the cutoff frequency m' used when the low frequency components were removed. The heartbeat signal selection unit 324 measures the heartbeat signal by selecting the phase signal that can measure the heartbeat signal with the highest accuracy from among the L×M′ phase signals P″(l, m′, c), each of which has a different waveform and from which low-frequency components have been removed (step ST2A-2-4).

[0095] First, the heartbeat signal selection unit 324 calculates the autocorrelation function represented by the above formula (4) for each of the L×M′ phase signals P″(l, m′, c) that have passed through the high-pass filter. For each of the calculated L×M′ autocorrelation functions, the heartbeat signal selection unit 324 acquires α peak values ​​in ascending order of the autocorrelation function coefficient or the ascending order of the lag number, calculates their average value, and calculates a value Y that indicates the level of periodicity. Here, α is an integer greater than or equal to 1. The heartbeat signal selection unit 324 also calculates a value Z by multiplying the cutoff frequency m′ of the high-pass filter used to remove low-frequency components by a coefficient β. Here, β is a value greater than or equal to 0. The heartbeat signal selection unit 324 calculates an evaluation value X using the calculated Y and Z according to the following formula (6). The reason for subtracting Z from the value Y that indicates the level of periodicity is that as the cutoff frequency of the high-pass filter increases, there is a higher possibility that components derived from the heartbeat will be removed. TIFF0007825797000005.tif9166

[0096] The heartbeat signal selection unit 324 selects the phase signal that maximizes the evaluation value X from the phase signals P''(c) that have passed through the high-pass filter, and uses the selected phase signal as the heartbeat signal P heart (c) Note that the respiratory signal may be selected as the heart rate signal due to the high periodicity of the components derived from breathing, resulting in a large evaluation value. Therefore, since the period of a heartbeat is generally shorter than the period caused by breathing, if the set number of α peaks cannot be obtained for the calculated autocorrelation function, or if the period is calculated from the lag value of the peaks of the calculated autocorrelation function and the calculated period is equal to or greater than a certain value, the heartbeat signal selection unit 324 may not select the heartbeat signal P heart (c) is output to the output unit 33.

[0097] In the heartbeat signal measuring device 3A according to the second embodiment, the measuring unit 32A calculates phase signals of each of the beamformed signals corresponding to a plurality of sets of the acquired distance bins, azimuth direction bins, and elevation direction bins, performs phase unwrapping on each of the calculated phase signals, performs high-pass filtering at a cutoff frequency on each of the phase-unwrapped phase signals to calculate phase signals from which a plurality of low-frequency components have been removed, calculates an evaluation value relating to the height of periodicity for each of the phase signals from which the low-frequency components have been removed based on the height of the peak of the autocorrelation function, and measures the heartbeat signal by selecting the phase signal with the largest evaluation value from the plurality of phase signals from which the low-frequency components have been removed. Heartbeats are generally periodic, and fluctuations in the body surface of the subject are also periodic. Therefore, the heartbeat signal measuring device 3A can measure a heartbeat signal from which components derived from the breathing or body movement of the subject have been removed by selecting a phase signal with high periodicity that has passed through a high-pass filter.

[0098] Embodiment 3 FIG. 19 is a block diagram showing an example of the configuration of a heartbeat signal measurement system 1B according to a third embodiment. In FIG. 19, the heartbeat signal measurement system 1B is a system that measures the heartbeat signal of a person being measured using a radar signal, and includes a radar sensor unit 2 and a heartbeat signal measurement device 3B. The heartbeat signal measurement device 3B extracts distance bins and direction bins after performing digital beamforming. The heartbeat signal measurement device 3B includes an acquisition unit 31A, a measurement unit 32B, and an output unit 33.

[0099] The acquisition unit 31A acquires a set of distance bins, azimuth direction direction bins, and elevation direction direction bins in which a living body may be present, calculated based on the received signals of radio waves irradiated to the subject and reflected by the subject, and digital beamformed signals in the azimuth direction and elevation direction in order for the distance bins.

[0100] Acquisition unit 31A includes signal acquisition unit 311, preprocessing unit 312, stationary object suppression unit 313, Fourier transform unit 314, digital beamforming unit 317, and distance bin and azimuth bin extraction unit 318. Distance bin and azimuth bin extraction unit 318 estimates the number of subjects O based on the complex amplitude of the digital beamformed signal, and extracts distance bins, azimuth bins, and elevation bins (o, i, j, k) where subjects may exist.

[0101] Next, a heartbeat signal measuring method according to the third embodiment will be described. FIG. 20 is a flowchart showing a heartbeat signal measuring method according to the third embodiment, illustrating a series of processes corresponding to step ST2 in FIG. First, the measurement unit 32B acquires L' sets of distance bins, azimuth direction azimuth bins, elevation direction bins, and the number of subjects O, calculated by the distance bin and azimuth bin extraction unit 318 based on the complex amplitude of the digital beamformed signal, in which a living body may be present (step ST2B-1).

[0102] Fig. 21 shows the extraction results of distance bins and azimuth bins when there are two subjects. The extraction results shown in Fig. 21 are drawn two-dimensionally in terms of distance and azimuth direction. The distance bin and azimuth bin extraction unit 318 calculates BF(r, e, a, c) by adding up the complex amplitudes of the digitally beamformed signal BF(r, e, a, c) for all cycles c. abs (r, e, a). The range and orientation bin extractor 318 then extracts the calculated signal BF abs A set (i,j,k) of r, e, and a whose complex amplitude is equal to or greater than a certain threshold value is extracted for (r,e,a).

[0103] Next, the distance bin and orientation bin extraction unit 318 classifies the extracted sets (i, j, k) of r, e, and a into clusters o using a clustering method such as DBSCAN (Density-based spatial clustering of applications with noise), and calculates the number of subjects O from the number of classified clusters. The distance bin and orientation bin extraction unit 318 outputs the L' sets (o, i, j, k) extracted and classified into clusters o to the measurement unit 32B. Here, o is a variable for identifying clusters and is an integer equal to or less than o=1, . . . , O. O is the number of clusters, i.e., the number of subjects, and is an integer equal to or greater than 1. i is an integer equal to or greater than 1 and equal to R, j is an integer equal to or greater than 1 and equal to E, and k is an integer equal to or greater than 1 and equal to A.

[0104] The measurement unit 32B measures O heartbeat signals based on phase changes of signals corresponding to each of L' sets of distance bins, azimuth direction direction bins, and elevation direction direction bins acquired from the signals after digital beamforming (step ST2B-2). The measurement unit 32B acquires L' sets of integers (o, i, j, k) of the extracted person, distance bins, azimuth direction direction bins, and elevation direction direction bins from the distance bin and orientation bin extraction unit 318.

[0105] The measurement unit 32B measures the heartbeat signal for each cluster o and obtains O heartbeat signals Pheart (o, c) is output to the output unit 33. Here, the measurement process of the heartbeat signal is the same as in the first or second embodiment, and the measurement unit 32B calculates an evaluation value X for each cluster o and selects the phase signal with the maximum evaluation value X as the heartbeat signal of the multiple people. These heartbeat signals are phase signals from which highly periodic trend components or low-frequency components have been removed.

[0106] As described above, in the heartbeat signal measuring device 3B according to the third embodiment, the acquiring unit 31A calculates distance bins, azimuth direction bins, elevation direction bins, and the number of subjects where a living body may be present based on the complex amplitude of the digital beamformed signal, and acquires multiple sets of these. The measuring unit 32B measures multiple heartbeat signals based on phase changes in the phase signals corresponding to each of the multiple sets of distance bins, azimuth direction bins, and elevation direction bins acquired from the digital beamformed signal. Heartbeats are generally periodic, and fluctuations in the subject's body surface are also periodic. Therefore, the heartbeat signal measuring device 3B can accurately measure the heartbeat signals of multiple subjects simultaneously by selecting phase signals from which highly periodic trend components or low-frequency components have been removed.

[0107] It is possible to combine the embodiments, modify any of the components of the embodiments, or omit any of the components of the embodiments. [Industrial Applicability]

[0108] The heart rate signal measuring device according to the present disclosure can be used, for example, in a driving assistance system that takes into account the state of a vehicle driver based on a heart rate signal. [Explanation of symbols]

[0109] 1, 1A, 1B Heartbeat signal measurement system, 2 Radar sensor unit, 3, 3A, 3B Heartbeat signal measurement device, 21-1, 21-2, 21-N, 21-g, 21-h, 21-n Antenna, 22-1, 22-2, 22-n, 22-N Circulator, 23-1, 23-2, 23-n, 23-N Signal receiving unit, 24 Signal transmitting unit, 31, 31A Acquisition unit, 32, 32A, 32B Measurement unit, 33 Output unit, 100 Input interface, 101 Output interface, 102 Processing circuit, 103 Processor, 104 Memory, 241 Output destination selection unit, 242 Signal generator, 311 Signal acquisition unit, 312 Preprocessing unit, 313 Stationary object suppression unit, 314 Fourier transform unit, 315 Distance bin extraction unit, 316 An azimuth bin extraction unit, 317 a digital beamforming unit, 318 a range bin and azimuth bin extraction unit, 321 a phase calculation unit, 322 a phase unwrapping unit, 323 a trend removal unit, 324 a heartbeat signal selection unit, and 325 a high-pass filter unit.

Claims

1. an acquisition unit that acquires a set of distance bins, azimuth direction direction bins, and elevation direction direction bins in which a living body may exist, calculated based on a received signal of radio waves irradiated to the subject and reflected by the subject, and signals beamformed in the azimuth direction and the elevation direction in order for the distance bins; a measurement unit that measures a heartbeat signal of the subject by generating phase signals based on the beamformed signal, the distance bins, the azimuth direction bins, and the elevation direction bins, removing components to be removed that are derived from the subject's breathing or body movement from the generated phase signals, and selecting a phase signal from the phase signals from which the components to be removed have been removed based on an evaluation result of signal periodicity; A heart rate signal measuring device comprising:

2. The measurement unit measures the heartbeat signal based on a phase change of the phase signal corresponding to a plurality of sets of the acquired distance bin, the acquired azimuth direction bin, and the acquired elevation direction bin from the beamformed signal.

2. The heartbeat signal measuring device according to claim 1.

3. the acquisition unit calculates the distance bins, the azimuth direction direction bins, the elevation direction direction bins, and the number of subjects in which the living body may be present, based on the complex amplitude of the beamformed signal, and acquires a plurality of sets of these; The measurement unit measures the plurality of heartbeat signals based on phase changes of the phase signals corresponding to each of a plurality of sets of the acquired distance bin, the acquired azimuth direction bin, and the acquired elevation direction bin among the beamformed signals.

2. The heartbeat signal measuring device according to claim 1.

4. The measurement unit calculating the phase signals of the beamformed signals corresponding to a plurality of sets of the acquired range bins, the acquired azimuth direction bins, and the acquired elevation direction bins; performing phase unwrapping on each of the calculated phase signals; calculating, for each of the plurality of phase signals that have been subjected to phase unwrapping, the phase signal from which the trend component has been removed using a polynomial for removing the trend component resulting from the respiration or body movement of the subject; An evaluation value relating to the height of periodicity is calculated based on the height of a peak of an autocorrelation function for each of the plurality of phase signals from which the trend component has been removed, and the heartbeat signal is measured by selecting the phase signal from the plurality of phase signals from which the trend component has been removed that has the maximum evaluation value.

4. The heartbeat signal measuring device according to claim 2 or 3.

5. The measurement unit calculating the phase signals of the beamformed signals corresponding to a plurality of sets of the acquired range bins, the acquired azimuth direction bins, and the acquired elevation direction bins; performing phase unwrapping on each of the calculated phase signals; performing high-pass filtering of a cutoff frequency on each of the plurality of phase unwrapped phase signals to calculate the phase signal from which a plurality of low frequency components have been removed; An evaluation value relating to the height of periodicity is calculated based on the height of a peak of an autocorrelation function for each of the plurality of phase signals from which the low frequency components have been removed, and the heartbeat signal is measured by selecting the phase signal from the plurality of phase signals from which the low frequency components have been removed that has the maximum evaluation value.

4. The heartbeat signal measuring device according to claim 2 or 3.

6. 1. A method for measuring a heartbeat signal, performed by a heartbeat signal measuring device, comprising: an acquiring unit acquiring a set of distance bins, azimuth direction direction bins, and elevation direction direction bins in which a living body may exist, calculated based on a received signal of radio waves irradiated to the subject and reflected by the subject, and signals beamformed in the azimuth direction and the elevation direction in order for the distance bins; a measurement unit generating phase signals based on the beamformed signals, the distance bins, the azimuth direction bins, and the elevation direction bins, removing components to be removed that are derived from the breathing or body movement of the subject from the generated phase signals, and selecting the phase signals from the phase signals from which the components to be removed have been removed based on an evaluation result of the periodicity of the signals, thereby measuring a heartbeat signal of the subject; A method for measuring a heart rate signal comprising:

Images