Estimation device, estimation method, and program

Abstract

This estimation device comprises: a transmitting unit (1100) that processes a multicarrier signal and transmits the processed signal to a transmitting antenna unit; the transmitting antenna unit (1000) consisting of M transmitting antenna elements; a receiving antenna unit (1300) consisting of N receiving antenna elements; a receiving unit (1400) that observes the received signal for the first period; a first complex transfer function calculation unit (1500) that calculates a plurality of first complex transfer functions representing propagation characteristics between each transmitting antenna element and each receiving antenna element from the plurality of received signals observed within the first period for each subcarrier of the modulated signal; and a second complex transfer function calculation unit (1600) that calculates second complex transfer functions by dividing all elements of the first complex transfer functions by a direct wave component.

Description

[Technical Field]

[0001] The present disclosure relates to an estimation device, an estimation method, and a program for accurately estimating information about a living body. [Background technology]

[0002] Methods using wireless signals are being considered as a method for determining the location of a person (see, for example, Patent Documents 1 to 4). Patent Documents 1, 2, and 3 disclose techniques for estimating the location and state of a person to be detected by analyzing components including Doppler shifts using differential calculations. Patent Documents 4 and 5 disclose Doppler sensors that use OFDM (Orthogonal Frequency Division Multiplexing) signals. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-117972 [Patent Document 2] Japanese Patent Application Publication No. 2017-129558 [Patent Document 3] Japanese Patent Application Publication No. 2018-008021 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-088279 [Patent Document 5] Japanese Patent Application Laid-Open No. 2012-137340 [Patent Document 6] Japanese Patent Application Laid-Open No. 2006-157663 [Patent Document 7] Japanese Patent Application Laid-Open No. 2001-144722 [Non-patent literature]

[0004] [Non-Patent Document 1] H. Yamada, M. Ohmiya, Y. Ogawa and K. Itoh, "Superresolution techniques for time-domain measurements with a network analyzer," in IEEE Transactions on Antennas and Propagation, vol. 39, no. 2, pp. 177-183, Feb. 1991 Summary of the Invention [Problem to be solved by the invention]

[0005] With conventional methods, it is difficult to estimate information about a living body with high accuracy.

[0006] The present disclosure has been made in consideration of the above circumstances, and provides an estimation device that can estimate information about a living body with higher accuracy. [Means for solving the problem]

[0007] In order to achieve the above object, an estimation device according to an embodiment of the present disclosure includes a transmission signal generation unit that generates a multicarrier signal obtained by modulating a plurality of subcarrier signals, a transmission antenna unit having M (M is a natural number equal to or greater than 1) transmission antenna elements, a transmission unit that processes the multicarrier signal and outputs the multicarrier signal to the transmission antenna unit, thereby causing the multicarrier signal to be transmitted from the transmission antenna unit, and a reception antenna unit having N (N is a natural number equal to or greater than 1) reception antenna elements, and a reception signal that is received by each of the N reception antenna elements and includes a reflected signal that is a result of the multicarrier signal transmitted from each of the M transmission antenna elements being reflected or scattered by a living body, for a first period corresponding to a cycle derived from activity of the living body. a first complex transfer function calculation unit that calculates, for each of M×N combinations that are combinations of each of the M transmitting antenna elements and each of the N receiving antenna elements, a plurality of first complex transfer functions that represent propagation characteristics between the transmitting antenna elements and the receiving antenna elements in the combination, for each of a plurality of subcarriers to which the plurality of subcarrier signals respectively correspond; and a second complex transfer function calculation unit that calculates a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted from the plurality of receiving signals using one or more elements of the first complex transfer function, the direct wave components not passing through the living body. The one or more elements used to extract the direct wave component include two or more elements corresponding to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers, and the direct wave component is an average value of one element included in the first complex transfer function and the two or more elements. . Moreover, an estimation device according to an embodiment of the present disclosure includes a transmission signal generation unit that generates a multicarrier signal obtained by modulating a plurality of subcarrier signals, a transmission antenna unit having M (M is a natural number equal to or greater than 1) transmission antenna elements, a transmission unit that processes the multicarrier signal and outputs the multicarrier signal to the transmission antenna unit, thereby transmitting the multicarrier signal to the transmission antenna unit, a reception antenna unit having N (N is a natural number equal to or greater than 1) reception antenna elements, a reception unit that observes reception signals received by each of the N reception antenna elements, the reception signals including reflected signals obtained by the multicarrier signal transmitted from each of the M transmission antenna elements being reflected or scattered by a living body, for a first period corresponding to a cycle derived from activity of the living body, and and a second complex transfer function calculation unit that calculates a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted from the plurality of received signals using one or more elements of the first complex transfer function, the direct wave components not passing through the living body. The one or more elements used to extract the direct wave components include two or more elements corresponding to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers, and the direct wave components are direct wave transfer functions that are channel components of direct waves calculated by multiplying the first complex transfer function by the eigenvector of a pair with the largest eigenvalue among pairs of eigenvalues ​​and eigenvectors calculated by eigenvalue decomposition of a correlation matrix between one element included in the first complex transfer function and the two or more elements.

[0008] Furthermore, an estimation method according to an aspect of the present disclosure includes generating a multicarrier signal in which a plurality of subcarrier signals are modulated, processing the multicarrier signal, and outputting the multicarrier signal to a transmitting antenna unit having M (M is a natural number equal to or greater than 1) transmitting antenna elements, thereby transmitting the multicarrier signal to the transmitting antenna unit, and estimating a received signal including a reflected signal resulting from the multicarrier signal transmitted from each of the M transmitting antenna elements reflected or scattered by a living body, based on a period corresponding to an activity of the living body. and calculating, for each of M×N combinations of each of the M transmitting antenna elements and each of the N receiving antenna elements, a plurality of first complex transfer functions representing propagation characteristics between the transmitting antenna elements and the receiving antenna elements in the combination, for each of a plurality of subcarriers to which the plurality of subcarrier signals respectively correspond, using the plurality of received signals observed during the first period; and calculating a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted from the plurality of received signals using one or more elements of the first complex transfer function, the direct wave components not passing through the living body. wherein the one or more elements used to extract the direct wave component include two or more elements respectively corresponding to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers, and the direct wave component is a direct wave transfer function that is a channel component of a direct wave, calculated by multiplying the first complex transfer function by the eigenvector of a pair with the largest eigenvalue, among pairs of eigenvalues ​​and eigenvectors calculated by eigenvalue decomposition of a correlation matrix between one element included in the first complex transfer function and the two or more elements. .

[0009] These general or specific aspects may be realized as a system, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized as any combination of an apparatus, a system, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0010] According to the present disclosure, information about a living body can be estimated with higher accuracy. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a block diagram showing an example of the configuration of an estimation device. [Figure 2] FIG. 2 is a schematic diagram showing that the phase of a received signal changes depending on the frequency and distance. [Figure 3] FIG. 3 is a schematic diagram showing the relationship between the phase error and the channel. [Figure 4] FIG. 4 is a schematic diagram showing the relationship between frequency and the gradient of the phase difference. [Figure 5] FIG. 5 is a schematic diagram showing the phase of a time-domain biological component transfer function matrix. [Figure 6] FIG. 6 is a schematic diagram showing the positional relationship between the living body, the transmitting antenna element, and the receiving antenna element, and the position of the living body defined by the third distance. [Figure 7] FIG. 7 is a schematic diagram showing how the position of a living body is estimated using a plurality of receiving antenna elements. [Figure 8] FIG. 8 is a flowchart showing the estimation process of the estimation device. [Figure 9] FIG. 9 is a flowchart showing the second complex transfer function calculation process. [Figure 10] FIG. 10 is a flowchart showing the third complex transfer function calculation process. [Figure 11] FIG. 11 is a flowchart showing the distance measurement process. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Findings that formed the basis of this disclosure) As a method for determining the location of a person, a method using radio signals is being considered.

[0013] For example, Patent Documents 1 and 2 disclose a method of transmitting a radio signal to a predetermined area, receiving the radio signal reflected by a detection target using multiple antennas, and estimating a complex transfer function between the transmitting and receiving antennas. The complex transfer function is a function of complex numbers that represents the relationship between input and output, and in this case, represents the propagation characteristics between the transmitting and receiving antennas. The number of elements of this complex transfer function is equal to the product of the number of transmitting antennas and the number of receiving antennas. Furthermore, Patent Document 3 discloses a method of estimating the posture of a living body using the radar cross section (RCS) calculated from the received power, using a configuration similar to that of Patent Document 2. The RCS is an index that represents the area of ​​an object that reflects the transmitted wave, and the RCS of a living body varies depending on its posture.

[0014] Patent Document 1 further discloses that the position and status of a person to be detected can be determined by analyzing components containing Doppler shift using Fourier transform. More specifically, the time changes of elements of a complex transfer function are recorded, and the resulting time waveform is Fourier transformed. Living organisms, such as people, impart a slight Doppler effect to reflected waves due to biological activities such as breathing and heartbeat. Therefore, components containing Doppler shift include the influence of the person. On the other hand, components without Doppler shift are not influenced by the person, i.e., correspond to reflected waves from fixed objects or direct waves between transmitting and receiving antennas. In other words, the position and status of a person to be detected can be determined using components within a predetermined frequency range in the Fourier transformed waveform.

[0015] Patent Document 2 discloses a method for extracting components containing slight Doppler shifts due to the influence of living organisms by recording the time changes of elements of a complex transfer function and analyzing the difference information. In other words, the difference information can be used to know the position and state of the person to be detected.

[0016] On the other hand, Patent Document 3 discloses an OFDM Doppler radar that transmits pulses using OFDM signals and detects the Doppler shift caused by a target moving object. Also, Patent Document 4 discloses a high-speed processing method for OFDM Doppler radar that does not require a Fourier transform.

[0017] Furthermore, Patent Documents 6 and 7 disclose techniques for improving the estimation accuracy of the complex transfer function between transmitting and receiving antennas by transmitting OFDM signals. Patent Document 5 discloses that the received noise components can be reduced by averaging the complex transfer function for each subcarrier, and Patent Document 7 discloses that the received noise components can be reduced by selecting the subcarrier with the maximum received power.

[0018] However, the methods of Patent Documents 1, 2, and 3 transmit unmodulated waves, making it difficult to use commercially available devices and requiring dedicated hardware. In other words, currently popular communication devices cannot be used, and users must install dedicated hardware in addition to their existing communication devices.

[0019] Furthermore, the methods of Patent Documents 4 and 5 also require a steep transmission pulse to achieve sufficient accuracy, which requires a wide frequency band, resulting in higher hardware costs compared to consumer communication devices.

[0020] The technology in Non-Patent Document 1 uses a measuring device such as a network analyzer to transmit and receive signals at multiple frequencies, thereby estimating the ToF (Time of Flight) between the transmitting and receiving antennas and the distance that can be calculated from the ToF. This utilizes the property that, similar to a frequency-modulated continuous wave (FMCW) radar ranging sensor, when two signals of different frequencies are transmitted with the same phase, the phase received by the receiving antenna changes depending on the frequency difference of the signals and the distance they propagate between the antennas. The technology in Non-Patent Document 1 further improves resolution by estimating ToF using the MUSIC (Multiple Signal Classification) method. However, the transmitting and receiving sides must operate on the same reference frequency or be highly synchronized, which means that household devices such as wireless LANs cannot be used. Furthermore, it is only possible to estimate the distance between antennas; it cannot estimate the distance to, for example, a living body that does not have special equipment.

[0021] In view of this, the inventors have invented an estimation device etc. that can estimate information about a living body with high accuracy at low cost using existing communication devices and by utilizing multi-carrier radio signals such as OFDM. The information about the living body includes the distance from the estimation device to the living body, the direction from the estimation device to the living body, the position of the living body, the identifier of the living body, etc.

[0022] That is, the estimation device according to the first aspect of the present disclosure includes a transmission signal generation unit that generates a multicarrier signal in which a plurality of subcarrier signals are modulated, a transmission antenna unit having M (M is a natural number of 1 or more) transmission antenna elements, a transmission unit that processes the multicarrier signal and outputs it to the transmission antenna unit, thereby transmitting the multicarrier signal to the transmission antenna unit, and a reception antenna unit having N (N is a natural number of 1 or more) reception antenna elements, and observes, for a first period corresponding to a cycle derived from activity of the living body, reception signals received by each of the N reception antenna elements, the reception signals including reflected signals formed by the multicarrier signals transmitted from each of the M transmission antenna elements being reflected or scattered by a living body. The apparatus comprises a receiving unit, a first complex transfer function calculation unit that calculates, for each of M×N combinations, which are combinations of each of the M transmitting antenna elements and each of the N receiving antenna elements, a plurality of first complex transfer functions that represent propagation characteristics between the transmitting antenna elements and the receiving antenna elements in that combination, for each of a plurality of subcarriers to which the plurality of subcarrier signals respectively correspond, using the plurality of received signals observed in the receiving unit during the first period, and a second complex transfer function calculation unit that calculates a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted from the plurality of received signals using one or more elements of the first complex transfer function, the direct wave components not passing through the living body.

[0023] This makes it possible to calculate a second complex transfer function in which the frequency phase error and components corresponding to at least one of (1) a clock fluctuation between a transmitter including a transmission signal generator and a transmitter that transmits from a transmitting antenna and a receiver including a receiver that receives by a receiving antenna, and (2) a timing fluctuation of digital-to-analog conversion of a transmission signal or analog-to-digital conversion of a reception signal are suppressed. Therefore, information about a living body can be obtained using a wireless signal in a short time with high accuracy.

[0024] This configuration makes it possible to realize a biological radar by using a multi-carrier signal such as OFDM for the transmission signal, utilizing existing communication equipment. For example, OFDM receivers are already widely used in mobile phones, television broadcast receivers, wireless LAN devices, etc., and are less expensive than those using unmodulated signals.

[0025] An estimation device according to a second aspect of the present disclosure is the estimation device according to the first aspect, wherein the one or more elements used to extract the direct wave component include two or more elements corresponding to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers.

[0026] As a result, it is possible to more effectively suppress components corresponding to at least one of (1) clock fluctuations between a transmitter consisting of a transmission signal generation unit and a transmission unit that transmits from a transmission antenna unit, and a receiver consisting of a reception unit that receives by a reception antenna unit, and (2) timing fluctuations in the digital-to-analog conversion of the transmission signal or the analog-to-digital conversion of the reception signal.

[0027] An estimation device according to a third aspect of the present disclosure is the estimation device according to the second aspect, wherein the direct wave component is an average value of one element included in the first complex transfer function and the two or more elements.

[0028] An estimation device according to a fourth aspect of the present disclosure is the estimation device according to the second aspect, wherein the direct wave component is a direct wave transfer function, which is a channel component of a direct wave, calculated by multiplying the first complex transfer function by the eigenvector that is the pair of eigenvalues ​​with the largest eigenvalue, among pairs of eigenvalues ​​and eigenvectors calculated by eigenvalue decomposition of a correlation matrix between one element included in the first complex transfer function and the two or more elements.

[0029] An estimation device according to a fifth aspect of the present disclosure is an estimation device according to any one of the first to fourth aspects, further comprising a third complex transfer function calculation unit that calculates a third complex transfer function in which a frequency phase error in the plurality of subcarriers is corrected based on the distance between the transmitting antenna element and the receiving antenna element and the first complex transfer function.

[0030] An estimation device according to a sixth aspect of the present disclosure is the estimation device according to any one of the first to fourth aspects, further comprising a third complex transfer function calculation unit that calculates a third complex transfer function in which frequency phase errors in the plurality of subcarriers are corrected based on a distance between the transmitting antenna element and the receiving antenna element and a reference complex transfer function matrix that is a complex transfer function observed for a second time period.

[0031] An estimation device according to a seventh aspect of the present disclosure is an estimation device according to the fifth or sixth aspect, further comprising: a biometric correlation matrix calculation unit that calculates a biometric correlation matrix by sequentially recording the calculated third complex transfer functions in a time series in the order in which they are observed and extracting components related to the biometric organism from the third complex transfer functions; and a ranging unit that uses the biometric correlation matrix to estimate a third distance, which is the sum of a first distance between the transmitting antenna unit and the biometric organism and a second distance between the receiving antenna unit and the biometric organism.

[0032] Therefore, the third distance can be calculated with higher accuracy.

[0033] An estimation device according to an eighth aspect of the present disclosure is the estimation device according to the seventh aspect, wherein the biometric correlation matrix calculation unit calculates a correlation matrix of the third complex transfer function, calculates a first vector by vectorizing a lower triangular matrix excluding diagonal terms of the correlation matrix, and extracts components related to the biometric organism from the first vector, thereby calculating the biometric correlation matrix.

[0034] Therefore, the third distance can be calculated with higher accuracy.

[0035] An estimation device according to a ninth aspect of the present disclosure is an estimation device according to the seventh or eighth aspect, wherein the distance measurement unit estimates the third distance using any one of the MUSIC (MUltiple SIgnal Classification) method, the beamformer method, and the Capon method.

[0036] An estimation device according to a tenth aspect of the present disclosure is an estimation device according to any one of the seventh to ninth aspects, wherein at least one of the M transmitting antenna elements and the N receiving antenna elements includes two antenna elements, and the estimation device is equipped with a position estimation unit that calculates two or more ellipses having the positions of the M transmitting antenna elements and the N receiving antenna elements as their foci and whose major axes have the length of the third distance, and estimates the intersection of the ellipses as the position of the living body.

[0037] Therefore, the position of the living body relative to the estimation device can be estimated with higher accuracy.

[0038] An estimation method according to an eleventh aspect of the present disclosure includes generating a multicarrier signal in which a plurality of subcarrier signals are modulated, processing the multicarrier signal, and outputting the multicarrier signal to a transmitting antenna unit having M (M is a natural number equal to or greater than 1) transmitting antenna elements, thereby transmitting the multicarrier signal to the transmitting antenna unit, and estimating a received signal, which is received by each of N (N is a natural number equal to or greater than 1, provided that at least one of M and N is equal to or greater than 2) receiving antenna elements constituting a receiving antenna unit, and which includes a reflected signal resulting from the multicarrier signal transmitted from each of the M transmitting antenna elements being reflected or scattered by a living body, as a period corresponding to an activity of the living body. and using the plurality of received signals observed during the first period, calculates, for each of M×N combinations which are combinations of each of the M transmitting antenna elements and each of the N receiving antenna elements, a plurality of first complex transfer functions which represent propagation characteristics between the transmitting antenna element and the receiving antenna element in the combination, for each of a plurality of subcarriers to which the plurality of subcarrier signals respectively correspond, and calculates a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted from the plurality of received signals using one or more elements of the first complex transfer function, the direct wave components not passing through the living body.

[0039] This makes it possible to calculate a second complex transfer function in which the frequency phase error and components corresponding to at least one of (1) a clock fluctuation between a transmitter including a transmission signal generator and a transmitter that transmits from a transmitting antenna and a receiver including a receiver that receives by a receiving antenna, and (2) a timing fluctuation of digital-to-analog conversion of a transmission signal or analog-to-digital conversion of a reception signal are suppressed. Therefore, information about a living body can be obtained using a wireless signal in a short time with high accuracy.

[0040] This configuration makes it possible to realize a biological radar by using a multi-carrier signal such as OFDM for the transmission signal, utilizing existing communication equipment. For example, OFDM receivers are already widely used in mobile phones, television broadcast receivers, wireless LAN devices, etc., and are less expensive than those using unmodulated signals.

[0041] A program according to a twelfth aspect of the present disclosure is a program for causing a computer to execute the estimation method according to the eleventh aspect.

[0042] The present disclosure may be realized not only as an apparatus, but also as an integrated circuit including the processing means of such an apparatus, as a method in which the processing means constituting the apparatus have steps, as a program that causes a computer to execute those steps, or as information, data, or signals indicating the program.These programs, information, data, and signals may be distributed via recording media such as CD-ROMs or communication media such as the Internet.

[0043] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that each of the embodiments described below represents a preferred specific example of the present disclosure. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present disclosure will be described as optional components that constitute a more preferred embodiment. Note that in this specification and drawings, components having substantially the same functional configuration will be assigned the same reference numerals to avoid redundant description.

[0044] (Embodiment 1) Hereinafter, a method for estimating the distance to a living body, which is a detection target, by the estimation device 100 according to the embodiment will be described with reference to the drawings.

[0045] [Configuration of Estimation Device 100] FIG. 1 is a block diagram showing an example of the configuration of an estimation device 100 according to an embodiment.

[0046] 1 includes a transmitting antenna unit 1000, a transmitting unit 1100, a transmitting signal generating unit 1200, a receiving antenna unit 1300, a receiving unit 1400, a first complex transfer function calculating unit 1500, a second complex transfer function calculating unit 1600, a third complex transfer function calculating unit 1700, a biological correlation matrix calculating unit 1800, and a ranging unit 1900. The estimation device 100 estimates the location of a biological body 200 based on the location of the estimation device 100. The estimation device 100 estimates, for example, the distance from the estimation device 100 to the biological body 200.

[0047] [Transmission signal generation unit 1200] The transmission signal generating unit 1200 generates a multicarrier signal in which a plurality of subcarrier signals are returned for each of the M transmission antenna elements included in the transmission antenna unit 1000. The transmission signal generating unit 1200 generates S subcarrier signals corresponding to S subcarriers (S is a natural number equal to or greater than 2) in different frequency bands, and multiplexes the generated S subcarrier signals to generate a multicarrier signal. In this embodiment, the transmission signal generating unit 1200 will be described using an OFDM signal as an example of a multicarrier signal. However, as long as the multicarrier signal is obtained by multicarrier modulation, the transmission signal generating unit 1200 is not limited to generating an OFDM signal in which the subcarriers are orthogonal, and may generate other multicarrier signals such as a simple FDM (Frequency Division Multiplexing) signal. Note that the OFDM signal has high frequency band utilization efficiency and is, for example, a signal in which S subcarrier signals corresponding to the S subcarriers are multiplexed.

[0048] Furthermore, the signal generated by the transmission signal generating unit 1200 may be used in common with the signal used for communication.

[0049] [Transmitter 1100] The transmitter 1100 performs appropriate processing on the signal generated by the transmission signal generator 1200 to generate a transmission wave. Examples of processing performed here include up-conversion, which converts the signal from an intermediate frequency (IF) frequency band to a radio frequency (RF) frequency band, and amplification, which amplifies the signal to an appropriate transmission level. As shown in FIG. 1 , the transmitter 1100 outputs the processed multicarrier signal to the transmitting antenna unit 1000, causing the transmitting antenna unit 1000 to transmit the multicarrier signal. As a result, the multicarrier signal is transmitted from M (M is a natural number equal to or greater than 1) transmitting antenna elements 1001 provided in the transmitting antenna unit 1000.

[0050] [Transmitting antenna unit 1000] The transmitting antenna unit 1000 has M transmitting antenna elements 1001. In this embodiment, the transmitting antenna unit 1000 has one transmitting antenna element 1001. As described above, the transmitting antenna element 1001 transmits the signal (transmission wave) generated by the transmitting unit 1100.

[0051] [Receiving antenna part 1300] The receiving antenna unit 1300 has N (N is a natural number equal to or greater than 1) receiving antenna elements 1301. In this embodiment, the receiving antenna unit 1300 has one receiving antenna element 1301. As shown in FIG. 1 , for example, one receiving antenna element 1301 receives a signal (received signal) transmitted from one transmitting antenna element 1001 and reflected by a living body 200.

[0052] [Receiver 1400] The receiving unit 1400 observes the received signal received by the receiving antenna element 1301, which includes a reflected signal resulting from the multicarrier signal transmitted from the transmitting antenna element 1001 being reflected or scattered by the living organism 200, for a first period corresponding to a cycle derived from the activity of the living organism 200. The cycle derived from the activity of the living organism is a cycle derived from the living organism (biological variation cycle) that is a time period equal to or longer than half the cycle of any one of breathing, heartbeat, and body movement of the living organism 200.

[0053] The receiving unit 1400 converts high-frequency signals received by the receiving antenna elements 1301 into low-frequency signals that can be processed. The receiving unit 1400 then demodulates the M OFDM signals transmitted by the transmitting antenna elements 1001 into S×M subcarrier signals. In this embodiment, since M=1, S subcarrier signals are demodulated. Each of the S×M subcarrier signals is represented by an IQ symbol. The receiving unit 1400 outputs S×M sets of subcarrier signals (low-frequency signals) obtained by converting the high-frequency signals received by the N receiving antenna elements 1301 to the first complex transfer function calculating unit 1500, at least for a first period.

[0054] In addition, the receiving unit 1400 may constantly observe the received signal received by the receiving antenna unit 1300 and continuously or periodically transmit S×M subcarrier signals (IQ symbols) to the first complex transfer function calculating unit 1500.

[0055] [First complex transfer function calculation unit 1500] The first complex transfer function calculation unit 1500 uses a plurality of received signals observed in a first period by the receiving unit 1400 to calculate, for each of M×N combinations which are combinations of M transmitting antenna elements 1001 and N receiving antenna elements 1301, a plurality of first complex transfer functions which represent propagation characteristics between the transmitting antenna elements 1001 and the receiving antenna elements 1301 in the combination, for each of a plurality of subcarriers to which a plurality of subcarrier signals respectively correspond. In this embodiment, the estimation apparatus 100 includes one transmitting antenna element 1001 and one receiving antenna element 1301, and therefore there is one combination.

[0056] In this embodiment, the first complex transfer function calculation unit 1500 uses S subcarrier signals (IQ symbols) transmitted from the receiving unit 1400 to calculate a first complex transfer function vector h as a first complex transfer function representing the propagation characteristics between the transmitting antenna element 1001 and the receiving antenna element 1301 for each of the S subcarrier signals, as shown in Equation 1.

[0057]

number

[0058] [Second complex transfer function calculation unit 1600] Here, the first complex transfer function vector h includes frequency fluctuation components originating from the transmitter and receiver, and Doppler shift originating from the living body 200. The first complex transfer function vector also includes reflected waves that do not pass through the living body 200, such as direct waves and reflected waves originating from fixed objects.

[0059] The frequency fluctuation components originating from the transmitter and receiver include, for example, (i) attenuation or phase rotation of the transmitted signal due to spatial propagation, (ii) clock frequency error (f RX -f TX ), (iii) sampling clock frequency error used in the radio equipment such as DA conversion. In order to remove the phase rotation of the frequency fluctuation components originating from the transmitter and receiver from the first complex transfer function vector h, the second complex transfer function calculation unit 1600 selects any one element h of the first complex transfer function vector h as a direct wave component. l Extract.

[0060]

number

[0061] Then, the second complex transfer function calculation unit 1600 extracts all elements of the first complex transfer function vector h as direct wave components as shown in Equation 2, and calculates one element h lThe second complex transfer function vector h' is calculated by dividing by h. Here, the element of the direct wave component may be any element of the first complex transfer function vector h, such as element h1. The second complex transfer function vector h' is an example of the second complex transfer function.

[0062] In this way, the second complex transfer function calculation unit 1600 performs a predetermined calculation using one or more elements of the first complex transfer function vector h to calculate a second complex transfer function vector h' from the first complex transfer function vector h, in which components corresponding to at least one of (1) clock fluctuations between the transmitter (composed of the transmission signal generation unit 1200 and the transmission unit 1100) that transmits from the transmitting antenna unit 1000 and the receiver (composed of the reception unit 1400) that receives via the receiving antenna unit 1300, and (2) timing fluctuations in digital-to-analog conversion of the transmitted signal or analog-to-digital conversion of the received signal are suppressed. Specifically, the second complex transfer function calculation unit 1600 calculates the second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted using one or more elements of the first complex transfer function. The direct wave components are components extracted from multiple received signals that do not pass through the living body 200.

[0063] [Third complex transfer function calculation unit 1700] The third complex transfer function calculation unit 1700 acquires the second complex transfer function vector h′ calculated by the second complex transfer function calculation unit 1600, and calculates a frequency phase correction value h cal1 The phase error in the frequency direction is the phase error between multiple signals with different frequencies. The phase error that requires calibration will be explained using Figure 2. Figure 2 is a schematic diagram showing how the phase of a received signal changes depending on the frequency and distance.

[0064] When signals of different frequencies propagate through space and are received, the amount of phase rotation of the transmitted signal relative to the received signal varies depending on the frequency and the distance between the transmitting antenna and the receiving antenna (hereinafter referred to as the antenna distance). The three transmitted waves 2001-A, 2001-B, and 2001-C in Figure 2 are signals of different frequencies transmitted from the transmitting antenna unit 1000 with the same phase, and it can be seen that the phases become more different as the propagation distance increases (2002-B, 2002-C). Therefore, the antenna distance can be calculated by measuring the phase difference between signals of known frequencies. However, the actually measured phase difference includes not only the influence of spatial propagation between the transmitting antenna and the receiving antenna, but also errors (hereinafter referred to as phase errors) due to the influence of the internal circuits and antenna phase characteristics of the transmitter and receiver. Therefore, to accurately measure the antenna distance, it is necessary to remove the phase error from the observed signal.

[0065] FIG. 3 is a diagram showing the correspondence between the above-mentioned phase error and the channel (complex transfer function).

[0066] The phase error is calculated for channel h, which is given by the matrix obtained by the measurement. meas and the ideal spatial channel h, which is expressed as a matrix that can be calculated from the antenna distance. ideal This is not limited to the case of estimating the distance between the antennas, but also applies to the case of estimating the distance to the living body 200.

[0067] Hereinafter, the specific operation of the third complex transfer function calculation unit 1700 will be described. The third complex transfer function calculation unit 1700 acquires the second complex transfer function vector h' and corrects the frequency phase error. Here, the frequency phase error refers to the difference in the phase of the second complex transfer function matrix from the reference subcarrier signal S0 that is not caused by spatial propagation between antennas. Specifically, the frequency phase error includes errors caused by the frequency characteristics of the transmitter 1100 and receiver 1400, the electrical length of the circuitry inside the transmitter 1100, the electrical length of the circuitry inside the receiver 1400, etc. The phase error is the phase error e jΦtxand the phase error e due to the receiving antenna unit 1300 and the receiving unit 1400. jΦrx Includes:

[0068] The third complex transfer function calculation unit 1700 calculates a frequency phase correction value for each element of the second complex transfer function vector using a predetermined method. First, the third complex transfer function calculation unit 1700 calculates h, which is an ideal channel between the antenna elements, based on the distance d between the transmitting antenna element 1001 and the receiving antenna element 1301 that is input in advance. ideal where h ideal is a complex vector having elements of the number S of subcarriers, and the i-th element is calculated using Equation 3.

[0069]

number

[0070] In this way, h ideal1 is an ideal complex transfer function between the transmitting antenna element and the receiving antenna element, which is obtained based on the inter-antenna distance between the transmitting antenna element 1001 and the receiving antenna element 1301.

[0071] Next, the third complex transfer function calculation unit 1700 acquires from the second complex transfer function calculation unit 1600 a reference complex transfer function vector, which is a complex transfer function vector received during a second reference period. The second period corresponds to a period resulting from the activity of the living organism 200. The period resulting from the activity of the living organism 200 is a period resulting from the activity of the living organism (biological fluctuation period), which is at least half a period of any of the periods of breathing, heartbeat, and body movement of the living organism 200. Note that the reference complex transfer function vector is preferably measured in an unattended state where there is little influence from moving bodies such as living organisms, but it may also include influence from living organisms and other moving bodies. The first complex transfer function vector acquired from the second complex transfer function calculation unit 1600 may be used as the reference complex transfer function vector. Note that if the second period is not unattended or if the direct wave component is not sufficiently large, the reference complex transfer function vector may be a complex transfer function vector obtained by Fourier transforming the observed complex transfer function vector with respect to the observation time (slow time) and extracting only the time-invariant components. Furthermore, the third complex transfer function calculating unit 1700 may calculate a new reference complex transfer function matrix based on data at a timing when fluctuations are small, which is obtained by simultaneously calculating fluctuations over time of the absolute values ​​of the complex transfer functions, and update the reference complex transfer function matrix with the calculated new reference complex transfer function matrix. In this embodiment, since there is one transmitting antenna element 1001 and one receiving antenna element 1301, the reference complex transfer function vector is a vector with S elements.

[0072] Next, the third complex transfer function calculation unit 1700 calculates the ideal channel h ideal1 and the reference complex transfer function (channel h meas ) and calculate a frequency and phase correction value h for correcting the frequency and phase error in the S subcarriers. cal1 Specifically, the third complex transfer function calculation unit 1700 calculates the ideal channel h ideal1 and the measured reference complex transfer function matrix h meas The ratio is calculated as the frequency phase correction value h cal1 Specifically, the frequency phase correction value h is calculated using the following equation 4. cal1 is calculated.

[0073]

number

[0074] Frequency phase correction value h cal is the same if the reference complex transfer function does not change. Therefore, the third complex transfer function calculation unit 1700 calculates the frequency phase correction value h cal1 is stored in memory, etc., and the frequency phase correction value h stored in memory, etc. is used from the next time onwards. cal1 That is, the third complex transfer function calculation unit 1700 may once use the frequency phase correction value h cal1 Once calculated, the frequency phase correction value h cal1 does not need to be calculated.

[0075] Finally, the third complex transfer function calculation unit 1700 calculates the frequency phase correction value h cal Based on this, the second complex transfer function vector h′ is corrected in accordance with the following equation 5 to calculate a third complex transfer function vector h″. The third complex transfer function vector h″ is an example of a third complex transfer function.

[0076]

number

[0077] In this way, the third complex transfer function calculation unit 1700 calculates the third complex transfer function vector h'' in which the frequency phase errors in the multiple subcarriers are corrected, based on the distance between the transmitting antenna element 1001 and the receiving antenna element 1301 and the reference complex transfer function matrix, which is the complex transfer function observed for the second period.

[0078] The third complex transfer function calculation unit 1700 outputs the calibrated third complex transfer function vector h'' thus obtained to the subsequent biological correlation matrix calculation unit 1800.

[0079] In the present embodiment, a method for calculating the calibration value from the measurement result of the complex transfer function has been described. However, if the calibration value does not change over time, a value measured using a measuring instrument such as a network analyzer in a factory or the like may be stored in memory as the calibration value, and the calibration value may be used to calculate the third complex transfer function vector h''.

[0080] [Biological correlation matrix calculation unit 1800] The biological correlation matrix calculation unit 1800 sequentially records the calculated third complex transfer function vector h" for each of the S subcarriers and for each of the MxN combinations in chronological order, which is the order in which they were observed. Then, the biological correlation matrix calculation unit 1800 extracts components related to the biological component from the third complex transfer function vector h" observed in the first period, which are sequentially recorded in chronological order, for each of the S subcarriers and for each of the MxN combinations, thereby calculating a biological component transfer function vector expressed by an MxN-dimensional matrix for each of the S subcarriers.

[0081] Here, the biological component transfer function vector is an extracted reflected wave or scattered wave (biological component) contained in the received signal that has passed through the living body 200. Methods for determining the biological component from a complex transfer function recorded in time series include the Fourier transform disclosed in Patent Document 1 and a method using difference information disclosed in Patent Document 2.

[0082] For example, in a method using Fourier transform, the third complex transfer function vector h'' is Fourier transformed with respect to the observation time (slow time) to extract only specific frequency components, thereby obtaining the biological component transfer function vector h'' fft Here, the biological component transfer function vector h fft is calculated for each of a plurality of frequency components that may include the influence of biological activity, for example, from 0.1 Hz to 3 Hz. In this method, the calculated biological component transfer function vector h fft is further inverse Fourier transformed in the subcarrier direction to obtain the biological component transfer function vector h ifftBy calculating the time from when the signal containing the biological component is transmitted from the transmitting unit 1100 until when it is received by the receiving unit 1400, the time is calculated.

[0083] Here, the biological component transfer function vector h'' fft The relationship between the frequency (column direction of the matrix) and phase of the above is shown in Figure 4. The solid line 4100 shows how the phase of each component of the biological component transfer function vector varies depending on the subcarrier frequency when the biological component 200 is present at a certain position. The phase here is the phase of the channel h used as the reference when calculating the second complex transfer function. l (frequency of subcarrier S0). When the living body 200 approaches the transmitting antenna element 1001 or the receiving antenna element 1301 from the above position, the path length of the radio waves reflected by the living body 200 becomes shorter, so the slope of the graph becomes gentler, as shown by the dashed line 4200. In principle, it is possible to estimate the ToF (Time Of Flight) or the distance to the living body from the slope of this graph. Specifically, this living body component transfer function vector h'' fft Further, the time domain biological component transfer function vector h'' is obtained by inverse Fourier transform in the subcarrier direction. ifft By calculating the time from when the signal containing the biological component is transmitted from the transmitter until when it is received by the receiver, the time can be calculated.

[0084] Figure 5 shows the time-domain biological component transfer function vector h'' ifft This shows the relationship between time (column direction of the matrix) and phase. The phase changes of solid line 4100 and dashed line 4200 in Figure 4 appear as peaks indicated by solid line 5100 and dashed line 5200, respectively. However, the time resolution Δt found here is expressed by Equation 6 using the subcarrier bandwidth B.

[0085]

number

[0086] For example, if the bandwidth is 20 MHz, the time resolution is equivalent to 0.05 μs, which translates to a distance resolution of approximately 15 m, which is not practical.

[0087] Therefore, in this embodiment, the resolution is improved by using the MUSIC (MUltiple SIgnification) method. In order to use the MUSIC method, the biological correlation matrix calculation unit 1800 calculates the biological component transfer function vector h''. fft Correlation matrix R f (Biocorrelation matrix) is calculated according to the following equation 7.

[0088]

number

[0089] where the biological component transfer function vector h'' fft exists for each frequency that may include vibrations caused by the living body after Fourier transform of the third complex transfer function vector h''. E[·] in Equation 7 indicates averaging processing in the frequency direction.

[0090] [Distance measurement section 1900] The distance measurement unit 1900 calculates the correlation matrix R calculated by the biological correlation matrix calculation unit 1800. f First, the distance measurement unit 1900 calculates the correlation matrix R f is decomposed into eigenvalues ​​and the vector U corresponding to the signal is obtained. S and the eigenvector U corresponding to the noise N Here, the eigenvectors corresponding to the signal are vectors that are ordered from the first eigenvector up to the number of targets to be measured, and if there is one target, for example, there is only the first eigenvector. Also, if there are k targets (k is a natural number of 2 or more), the eigenvectors corresponding to the signal are k eigenvectors from the first eigenvector to the k-th eigenvector. Also, the eigenvectors corresponding to noise refer to eigenvectors other than the eigenvector corresponding to the signal.

[0091] Using the eigenvectors obtained in this way, the MUSIC spectrum P MUSIC Calculate (d).

[0092]

number

[0093] where a(d) represents the steering vector and is calculated as shown in Equation 9.

[0094]

number

[0095] where λ i represents the wavelength of the i-th subcarrier.

[0096] The MUSIC spectrum P obtained in this way MUSIC The maximum value d in (d) corresponds to the sum (third distance) of the distance a (first distance) and the distance b (second distance) in FIG. 6, which will be described later. The distance a (first distance) is the distance between the transmitting antenna element 1001 and the living body 200. The distance b (second distance) is the distance between the receiving antenna element 1301 and the living body 200. In other words, the ranging unit 1900 can calculate the third distance by calculating the maximum value d. In this way, the ranging unit 1900 estimates the third distance, which is the sum of the first distance and the second distance between the transmitting antenna unit 1000 and the living body 200, using the living body correlation matrix calculated for each of the multiple subcarriers.

[0097] FIG. 6 is a schematic diagram showing the positional relationship between a living body, a transmitting antenna element, and a receiving antenna element, and the position of the living body defined by the third distance.

[0098] As shown in Fig. 6, by estimating the third distance, it can be seen that the position of the living body 200 on a plane is limited to the circumference of an ellipse 6100 whose foci are the positions of the transmitting antenna unit 1000 and the receiving antenna unit 1300. Note that, as shown in Fig. 7, three or more transmitting antenna units 1000 or receiving antenna units 1300 may be used to estimate a plurality of third distances, thereby estimating the position of the living body 200 from the intersection of the ellipses.

[0099] FIG. 7 is a schematic diagram showing how the position of a living body is estimated using a plurality of receiving antenna elements.

[0100] In this case, the receiving antenna unit 1300 of the estimation apparatus 100 includes three receiving antenna elements 1301-1, 1301-2, and 1301-3. Note that the receiving antenna unit 1300 is not limited to having three receiving antenna elements, as long as it has three or more receiving antenna elements. Furthermore, instead of the receiving antenna unit 1300 having three or more receiving antenna elements, the transmitting antenna unit 1000 may have three or more transmitting antenna elements.

[0101] As a result, for each of the three combinations (i.e., M×N combinations) of the combination of transmitting antenna element 1001 and receiving antenna element 1301-1, the combination of transmitting antenna element 1001 and receiving antenna element 1301-2, and the combination of transmitting antenna element 1001 and receiving antenna element 1301-3, ellipses 7100-1, 7100-2, and 7100-3 are calculated with the positions of the transmitting antenna element and receiving antenna element included in that combination as their focal points and the length of the major axis being the third distance, and the position of the living body 200 is estimated based on the three (i.e., M×N) intersections of the three (i.e., M×N) ellipses 7100-1, 7100-2, and 7100-3 obtained by the calculation that are closest to each other (i.e., M×N).

[0102] [Another example of a direct wave component] The second complex transfer function calculation unit 1600 of the embodiment calculates the first complex transfer function vector h by calculating any one element h in the first complex transfer function vector h as a direct wave component. l The second complex transfer function vector h' is calculated by dividing by one element h l The division is not limited to division by .

[0103] Specifically, to extract the direct wave component, two or more elements included in the first complex transfer function vector may be used, each of which corresponds to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers. The two or more elements correspond to two or more adjacent subcarriers among the plurality of subcarriers having different frequencies. The two or more subcarriers include at least two first subcarriers, each of which is adjacent to only one other subcarrier. Of the two or more subcarriers, the subcarriers other than the two first subcarriers are each adjacent to the other two subcarriers. In this way, the two or more adjacent subcarriers include multiple subcarriers that are consecutively adjacent from the subcarrier corresponding to the lowest frequency to the subcarrier corresponding to the highest frequency among the two subcarriers. Hereinafter, the two or more adjacent subcarriers may be referred to as K subcarriers (K=K1+K2, where K1 is an integer greater than or equal to 0 satisfying l-K1≧1, and K2 is an integer greater than or equal to 0 satisfying l+K2≦S) adjacent in the subcarrier direction.

[0104] For example, the l-th element h of the first complex transfer function vector h l The direct wave component used for division is the l-th element h of the first complex transfer function vector h. l and the average value of K elements adjacent in the subcarrier direction. lmean is calculated using the following equation 10, and the l-th element h of the second complex transfer function vector h' is l ' is the calculated average value of the l-th element h lmean and is calculated using Equation 11.

[0105]

number

[0106]

number

[0107] In this case, the second complex transfer function vector h' is calculated using Equation 11 based on each element of the first complex transfer function vector h. Here, the number of elements of the second complex transfer function vector h' that can be calculated using Equation 10 is SK. In this case, the steering vector a(d) used in Equation 8 is calculated as shown in Equation 12.

[0108]

number

[0109] Furthermore, for example, the direct wave component used in the division may be calculated by obtaining h(t) by observing the complex transfer function for a certain period of time, performing eigenvalue decomposition on the correlation matrix for the entire observation time, and then calculating based on the eigenvalues ​​and eigenvectors calculated from Equations 13 and 14. As a result, the second complex transfer function vector h' may be calculated as shown in Equation 15.

[0110]

number

[0111]

number

[0112]

number

[0113] As shown in Equation 13 and Equation 14, the second complex transfer function calculation unit 1600 calculates the correlation matrix R of the first complex transfer function vector h(t). R , R T Calculate the correlation matrix R R , R T By decomposing each of these, the eigenvalue D R , D T and eigenvectors U and V. Next, the second complex transfer function calculation unit 1600 calculates the eigenvalue D as shown in Equation 15 using the results calculated by Equation 13 and Equation 14.R , D T The first complex transfer function vector h(t) is multiplied by the pair of eigenvectors u1 and v1 that maximizes the direct wave channel component u1 H h(t)v1 is calculated, and all elements of the first complex transfer function vector h are the channel components u1 of the direct wave. H The second complex transfer function vector h' is calculated by dividing by h(t)v1.

[0114] The direct wave component may be calculated based on the eigenvectors calculated by eigenvalue decomposing the correlation matrix over the entire observation time and calculating it using Equation 13 and Equation 14. As a result, the second complex transfer function vector h′ may be calculated as shown in Equation 16.

[0115]

number

[0116] [Another example of a biometric correlation matrix] The biological correlation matrix calculation unit 1800 according to the embodiment calculates the correlation matrix R by a method using Fourier transform. f However, the biological correlation matrix may be calculated using a lower triangular matrix.

[0117] The biological correlation matrix calculation unit 1800 may calculate the correlation matrix R of the second complex transfer function vector h′ as in Equation 17.

[0118]

number

[0119] The biological correlation matrix calculation unit 1800 calculates a lower triangular vector h'' by vectorizing the lower triangular matrix excluding the diagonal terms of the correlation matrix R as shown in Equation 18.

[0120]

number

[0121] The biological correlation matrix calculation unit 1800 performs a Fourier transform on the lower triangular vector h'' with respect to the observation time (slow time) to extract only specific frequency components, and calculates the biological component transfer function vector h for each frequency component from about 0.1 Hz to 3 Hz. fft The biological correlation matrix calculation unit 1800 calculates the biological component transfer function vector h fft ” and calculate the correlation matrix Rf using Equation 7.

[0122] In this case, the steering vector a(d) in Equation 8 is calculated as follows:

[0123]

number

[0124]

number

[0125] The biological correlation matrix calculation unit 1800 calculates the correlation matrix R a The steering vector a(d) is calculated by vectorizing the lower triangular matrix excluding the diagonal terms of (d) as shown in Equation 21.

[0126]

number

[0127] Furthermore, when using Equation 11 and Equation 12, the biological correlation matrix calculation unit 1800 calculates Equation 18 and Equation 21 in accordance with the number of elements.

[0128] [Operation of the estimation device 100] A description will be given of the operation of the estimation process of the estimation device 100 configured as above. Fig. 8 is a flowchart showing the estimation process of the estimation device 100 in this embodiment.

[0129] First, the estimation apparatus 100 calculates a second complex transfer function by dividing the first complex transfer function by the direct wave component (S1100).

[0130] Next, the estimating apparatus 100 calculates a third complex transfer function based on the calculated frequency phase correction value (S1200).

[0131] Then, the estimation device 100 calculates a biological correlation matrix based on the third complex transfer function and estimates a third distance which is the sum of the distance a (first distance) between the transmitting antenna unit 1000 and the biological body 200 and the distance b (second distance) between the receiving antenna unit 1300 and the biological body 200 (S1300).

[0132] FIG. 9 is a flowchart showing the detailed process of calculating the second complex transfer function in step S1100.

[0133] First, the estimation apparatus 100 transmits a multicarrier signal including S subcarriers from the transmitting antenna element 1001 (S1110).

[0134] Then, the estimation device 100 observes the signal (received signal) transmitted from the transmitting antenna element 1001 with the receiving antenna element 1301 during a second period in which no living body or other moving object is present in the specified space that is the estimation target area (S1120).

[0135] Next, the estimation apparatus 100 performs multicarrier demodulation on the received signal observed in the second period to demodulate it into S subcarrier signals (S1130).

[0136] Next, the estimation device 100 calculates a plurality of first complex transfer functions representing propagation characteristics between the transmitting antenna element 1001 and the receiving antenna element 1301 from the S subcarrier signals observed in the second time period, for each of the plurality of subcarriers to which the plurality of subcarrier signals respectively correspond (S1140). These processes are performed in parallel or sequentially for each subcarrier. The details are as described above, so a description thereof will be omitted here. The same applies hereinafter.

[0137] Next, the estimation device 100 derives the direct wave component h from the complex transfer function for each subcarrier. l is calculated (S1150).

[0138] Then, the estimation device 100 calculates the direct wave component h l and the complex transfer function for the second period, and calculates the difference h' (S1160).

[0139] FIG. 10 is a flowchart showing the detailed process of calculating the third complex transfer function in step S1200.

[0140] First, the estimation device 100 calculates the ideal channel h from the distance between the transmitting antenna element 1001 and the receiving antenna element 1301 given in advance. ideal is calculated (S1210).

[0141] The estimation device 100 then calculates the ideal channel h ideal and the second complex transfer function vector h' to obtain the frequency and phase correction value h cal is calculated (S1220).

[0142] FIG. 11 is a flowchart showing the detailed processing of distance measurement in step S1300.

[0143] First, the estimation apparatus 100 transmits a multicarrier signal including S subcarriers from the transmitting antenna element 1001 (S1310).

[0144] Then, the estimation device 100 observes the received signal including the reflected signal reflected by the living body 200 for a first period corresponding to a cycle resulting from the activity of the living body 50 (S1320).

[0145] Next, the estimation apparatus 100 performs multicarrier demodulation on the received signals observed in the first period, demodulating them into S signal sequences (S1330).

[0146] Next, the estimation device 100 calculates, from the S subcarrier signals observed in the first period, a plurality of first complex transfer functions representing propagation characteristics between the transmitting antenna element 1001 and the receiving antenna element 1301, for each of the plurality of subcarriers to which the plurality of subcarrier signals respectively correspond (S1340).

[0147] Next, the estimation apparatus 100 calculates a second complex transfer function vector h' according to Equation 2 (S1350).

[0148] Next, the estimation device 100 calculates the frequency phase correction value h cal The second complex transfer function vector h′ is corrected according to Equation 5 using the above formula to calculate the third complex transfer function vector h″ (S1360).

[0149] Next, the estimation device 100 derives the biological component transfer function vector h from the calibrated third complex transfer function vector h″. fft ” is calculated and the correlation matrix R f is calculated (S1370).

[0150] Next, the estimation device 100 calculates the MUSIC spectrum P MUSIC (d) is calculated (S1380).

[0151] Finally, the estimation device 100 calculates the MUSIC spectrum P MUSIC A search is made for d at which (d) is maximized, and the search result is output as the sum of the distance a between the transmitting antenna element 1001 and the living body 200 and the distance b between the living body 200 and the receiving antenna element 1301 (S1390).

[0152] [Effects, etc.] According to the estimation device 100 and estimation method of this embodiment, by using a multicarrier signal such as OFDM as a transmission signal, it is possible to estimate the distance between a living body and an antenna by utilizing an existing multicarrier transceiver.

[0153] In addition, the MUSIC method enables distance measurement with fine distance resolution.

[0154] Furthermore, according to the estimation device 100 of this embodiment, by using three or more transmitters to estimate a plurality of third distances to receivers, it is possible to estimate the position of the living body from the intersection of the ellipse.

[0155] Furthermore, according to the estimation device 100 of this embodiment, by using three or more receivers to estimate a plurality of third distances to the transmitter, it is possible to estimate the position of the living body from the intersection of the ellipse.

[0156] Furthermore, according to the estimation device 100 of this embodiment, it is possible to estimate the distance between a living body and an antenna and the position of the living body even in the case of a MISO (Multiple-Input Single-Output), SIMO (Single-Input Multiple-Output), or MIMO (Multiple-Input Multiple-Output) configuration.

[0157] As described above, the estimation device 100 according to this embodiment can realize an estimation device and estimation method that can estimate the distance and position of a living body using a wireless signal in a short time and with high accuracy.

[0158] While the positioning sensor and distance estimation method according to one aspect of the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiment or configurations constructed by combining components of different embodiments are also included within the scope of the present disclosure.

[0159] For example, in the above embodiment, distance estimation and position estimation of the living body 200 have been described as an example, but the present invention is not limited to the living body 200. When a high-frequency signal is irradiated, the present invention can be applied to various moving objects (machines, etc.) that exert a Doppler effect on the reflected wave due to their activity.

[0160] Furthermore, for example, in the above embodiment, an example in which there is one M transmitting antenna element and one N receiving antenna element has been mainly described, but this is not limited to this. There may be two or more M transmitting antenna elements, and there may be two or more N receiving antenna elements. There may also be two or more M transmitting antenna elements and two or more N receiving antenna elements.

[0161] Furthermore, for example, in the above embodiment, the estimation device 100 includes the third complex transfer function calculation unit 1700, the biological correlation matrix calculation unit 1800, and the distance measurement unit 1900. However, these components may not be included. The estimation device 100 may estimate information about the biological body 200 using the second complex transfer function vector h′ calculated by the second complex transfer function calculation unit 1600. As described above, the information about the biological body 200 includes, for example, the distance from the estimation device to the biological body, the direction from the estimation device to the biological body, the position of the biological body, and the biological body identifier. In this way, the second complex transfer function vector h′ calculated by the estimation device 100 can be used to estimate the direction from the estimation device to the biological body, the position of the biological body, the biological body identifier, and the like, in addition to estimating the distance from the estimation device to the biological body. The second complex transfer function vector h' has suppressed components corresponding to at least one of the frequency phase error and (1) clock fluctuation between the transmitter consisting of the transmission signal generation unit 1200 and the transmission unit 1100 that transmits from the transmitting antenna unit 1000 and the receiver consisting of the reception unit 1400 that receives by the receiving antenna unit 1300, and (2) timing fluctuation of the digital-to-analog conversion of the transmitted signal or the analog-to-digital conversion of the received signal. This makes it possible to estimate with high accuracy the direction from the estimation device to the living body, the position of the living body, the identifier of the living body, etc.

[0162] In each of the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may also be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0163] Furthermore, the present disclosure can be realized not only as a positioning sensor having such characteristic components, but also as an estimation method in which the characteristic components included in the positioning sensor are used as steps. Furthermore, the present disclosure can also be realized as a computer program that causes a computer to execute each of the characteristic steps included in such a method. It goes without saying that such a computer program can be distributed on a non-transitory computer-readable recording medium such as a CD-ROM or via a communication network such as the Internet. [Industrial Applicability]

[0164] The present disclosure can be used in positioning sensors and distance estimation methods that estimate the distance and position of a living body using wireless signals, and in particular in measuring instruments that measure the distance and position of a living body, including between a living body and a machine, home appliances that perform control according to the distance and position of a living body, and monitoring devices that detect the intrusion of a living body. [Explanation of symbols]

[0165] 100 Estimator 200 Living organisms 1000 Transmitting antenna section 1001 Transmitting antenna element 1100 Transmitter 1200 Transmission signal generator 1300, 1300-1, 1300-2, 1300-3 Receiving antenna section 1301 Receiving antenna element 1400 Receiver 1500 First complex transfer function calculation unit 1600 Second complex transfer function calculation unit 1700 Third complex transfer function calculation unit 1800 Biological correlation matrix calculation unit 1900 Rangefinder 2001-A, 2001-B, 2001-C Phase of each subcarrier signal transmitted from the transmitting antenna 2002-B, 2002-C Phase change of signals with different frequencies transmitted from the transmitting antenna 4100, 4200 Phase variation with frequency of complex transfer function matrix 5100, 5200 Phase after inverse Fourier transform of complex transfer function matrix 6100, 7100-1, 7100-2, 7100-3 Ellipse where a living body may exist, determined by the third distance

Claims

1. a transmission signal generator that generates a multicarrier signal in which a plurality of subcarrier signals are modulated; a transmitting antenna unit having M (M is a natural number equal to or greater than 1) transmitting antenna elements; a transmitting unit that processes the multicarrier signal and outputs the processed multicarrier signal to the transmitting antenna unit, thereby transmitting the multicarrier signal to the transmitting antenna unit; a receiving antenna unit having N (N is a natural number equal to or greater than 1) receiving antenna elements; a receiving unit that observes received signals received by each of the N receiving antenna elements, the received signals including reflected signals of the multicarrier signals transmitted from each of the M transmitting antenna elements reflected or scattered by a living body, for a first period corresponding to a cycle derived from activity of the living body; a first complex transfer function calculation unit that calculates, for each of M×N combinations of the M transmitting antenna elements and the N receiving antenna elements, a first complex transfer function that represents a propagation characteristic between the transmitting antenna element and the receiving antenna element in the combination, for each of a plurality of subcarriers to which the plurality of subcarrier signals respectively correspond, using the plurality of received signals observed in the receiving unit during the first period; a second complex transfer function calculation unit that calculates a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted from the plurality of received signals using one or more elements of the first complex transfer function, the direct wave components not passing through the living body; the one or more elements used to extract the direct wave component include two or more elements corresponding to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers, The direct wave component is an average value of one element included in the first complex transfer function and the two or more elements. Estimation device.

2. A transmission signal generation unit that generates a multicarrier signal in which a plurality of subcarrier signals are modulated; a transmitting antenna unit having M (M is a natural number equal to or greater than 1) transmitting antenna elements; a transmitting unit that processes the multicarrier signal and outputs the processed multicarrier signal to the transmitting antenna unit, thereby transmitting the multicarrier signal to the transmitting antenna unit; a receiving antenna unit having N (N is a natural number equal to or greater than 1) receiving antenna elements; a receiving unit that observes received signals received by each of the N receiving antenna elements, the received signals including reflected signals of the multicarrier signals transmitted from each of the M transmitting antenna elements reflected or scattered by a living body, for a first period corresponding to a cycle derived from activity of the living body; a first complex transfer function calculation unit that calculates, for each of M×N combinations of the M transmitting antenna elements and the N receiving antenna elements, a first complex transfer function that represents a propagation characteristic between the transmitting antenna element and the receiving antenna element in the combination, for each of a plurality of subcarriers to which the plurality of subcarrier signals respectively correspond, using the plurality of received signals observed in the receiving unit during the first period; a second complex transfer function calculation unit that calculates a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted from the plurality of received signals using one or more elements of the first complex transfer function, the direct wave components not passing through the living body; the one or more elements used to extract the direct wave component include two or more elements corresponding to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers, The direct wave component is a direct wave transfer function that is a channel component of a direct wave, calculated by multiplying the first complex transfer function by an eigenvector that is a pair of eigenvalues ​​and eigenvectors that are maximum among pairs of eigenvalues ​​and eigenvectors calculated by eigenvalue decomposition of a correlation matrix between one element included in the first complex transfer function and the two or more elements. Estimation device.

3. moreover, a third complex transfer function calculation unit that calculates a third complex transfer function in which a frequency phase error in the plurality of subcarriers is corrected based on the distance between the transmitting antenna element and the receiving antenna element and the first complex transfer function; The estimation device according to claim 1 or 2.

4. moreover, a third complex transfer function calculation unit that calculates a third complex transfer function in which frequency and phase errors in the plurality of subcarriers are corrected based on a distance between the transmitting antenna element and the receiving antenna element and a reference complex transfer function matrix that is a complex transfer function observed for a second period of time; The estimation device according to claim 1 or 2.

5. moreover, a biological correlation matrix calculation unit that calculates a biological correlation matrix by sequentially recording the calculated third complex transfer functions in time series in the order in which they are observed and extracting components related to the biological body from the third complex transfer functions; a distance measurement unit configured to estimate a third distance, which is the sum of a first distance between the transmitting antenna unit and the living body and a second distance between the receiving antenna unit and the living body, using the living body correlation matrix. The estimation device according to claim 3 .

6. The biological correlation matrix calculation unit calculating a correlation matrix of the third complex transfer function; calculating a first vector by vectorizing a lower triangular matrix excluding the diagonal terms of the correlation matrix; The biological correlation matrix is ​​calculated by extracting a biological component from the first vector. The estimation device according to claim 5 .

7. The distance measurement unit estimates the third distance using any one of a MUSIC (Multiple Signal Classification) method, a beamformer method, and a Capon method. The estimation device according to claim 5 .

8. At least one of the M transmitting antenna elements and the N receiving antenna elements includes two antenna elements; a position estimation unit that calculates two or more ellipses whose focal points are the positions of the M transmitting antenna elements and the N receiving antenna elements and whose major axis has a length of the third distance, and estimates the intersection of the ellipses as the position of the living body; The estimation device according to claim 5 .

9. generating a multicarrier signal modulated by a plurality of subcarrier signals; The multicarrier signal is processed and output to a transmitting antenna unit having M (M is a natural number equal to or greater than 1) transmitting antenna elements, thereby transmitting the multicarrier signal to the transmitting antenna unit; Observing received signals received by each of N (N is a natural number of 1 or more, provided that at least one of M and N is 2 or more) receiving antenna elements constituting a receiving antenna unit, the received signals including reflected signals resulting from the multicarrier signals transmitted from each of the M transmitting antenna elements being reflected or scattered by a living body, for a first period corresponding to a cycle resulting from activity of the living body; using the plurality of received signals observed during the first time period, for each of M×N combinations of each of the M transmitting antenna elements and each of the N receiving antenna elements, calculating a plurality of first complex transfer functions representing propagation characteristics between the transmitting antenna element and the receiving antenna element in the combination for each of a plurality of subcarriers to which the plurality of subcarrier signals respectively correspond; calculating a second complex transfer function by dividing all elements of the first complex transfer function by direct wave components extracted using one or more elements of the first complex transfer function, the direct wave components not passing through the living body from the plurality of received signals; the one or more elements used to extract the direct wave component include two or more elements corresponding to two or more subcarriers that are adjacent in frequency among the plurality of subcarriers, The direct wave component is a direct wave transfer function that is a channel component of a direct wave, calculated by multiplying the first complex transfer function by an eigenvector that is a pair of eigenvalues ​​and eigenvectors that are maximum among pairs of eigenvalues ​​and eigenvectors calculated by eigenvalue decomposition of a correlation matrix between one element included in the first complex transfer function and the two or more elements. Estimation method.

10. A program for causing a computer to execute the estimation method according to claim 9.

Images