Estimation device, estimation method, and program

Abstract

An inference device (100) comprises: a transmission signal generation unit (13); a transmission antenna unit (111); a transmission unit (12); a reception antenna unit (21); a reception unit (22); a complex transfer function calculation unit (123); a third complex transfer function calculation unit that calculates a third complex transfer function obtained by correcting frequency phase error and antenna phase error from a second complex transfer function obtained by dividing all elements of a first complex transfer function by a direct wave component; a living body correlation matrix calculation unit (129); and an inference unit (130) that infers a third distance which is a sum of a first distance between the transmission antenna unit (111) and a living body and a second distance between the reception antenna unit (21) and the living body, and a first angle which is a direction to the living body as seen from the transmission antenna unit (111) or the reception antenna unit (21).

Description

[Technical Field]

[0001] The present disclosure relates to an estimation device and an estimation method for estimating a distance or a position of a living body using a wireless signal. [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 [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 the distance from the estimation device to the living body and the direction from the estimation device to the living body with high accuracy.

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

[0007] In order to achieve the above object, an estimation device according to one embodiment of the present disclosure is an estimation device for estimating a distance and an angle to a living body, the estimation device including: a transmission signal generation unit that generates a multicarrier signal obtained by modulating S (S is a natural number equal to or greater than 2) 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 it to the transmission antenna unit, thereby causing the multicarrier signal to be transmitted by the transmission antenna unit; a reception antenna unit having 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) reception antenna elements; a reception unit that 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; and a reception unit that uses the reception signals observed in the first period to estimate a distance and an angle to a living body, a first complex transfer function calculation unit that calculates a first complex transfer function representing propagation characteristics between the transmitting antenna element and the receiving antenna element in each combination for each of the S subcarriers to which the S subcarrier signals respectively correspond, and sequentially records the first complex transfer function in a time series in which the plurality of received signals are observed; and a second complex transfer function 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. a third complex transfer function calculation unit that calculates a third complex transfer function obtained by correcting a frequency phase error in the S subcarriers of the second complex transfer function and an antenna phase error in the M transmitting antenna elements with respect to a reference phase calculated from a positional relationship between the M transmitting antenna elements and the N receiving antenna elements from the second complex transfer function; and a biological correlation matrix calculation unit that calculates a biological correlation matrix of an M×N matrix for each of the S subcarriers by extracting a biological component from the third complex transfer function.and an estimation unit that estimates 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, and a first angle, which is the direction of the living body as seen from the transmitting antenna unit or the receiving antenna unit, using the living body correlation matrix calculated for each of the S subcarriers.

[0008] Furthermore, an estimation method according to another aspect of the present disclosure is an estimation method for estimating a distance and an angle to a living body, the estimation method comprising: generating a multicarrier signal in which S (S is a natural number of 2 or more) subcarrier signals are modulated; processing the multicarrier signal and outputting it to a transmitting antenna unit having M (M is a natural number of 1 or more) transmitting antenna elements, thereby transmitting the multicarrier signal from the transmitting antenna unit; observing, for a first period corresponding to a cycle derived from activity of the living body, 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 formed by the multicarrier signals transmitted from each of the M transmitting antenna elements being reflected or scattered by the living body; and using the plurality of received signals observed in the first period, calculating a first propagation characteristic between the transmitting antenna elements and the receiving antenna elements in 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 complex transfer functions are calculated for each of the S subcarriers to which the S subcarrier signals respectively correspond, and are sequentially recorded in a time series in the order in which the plurality of received signals were observed. A second complex transfer function is calculated 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, and a reference phase calculated from the positional relationship between the M transmitting antenna elements and the N receiving antenna elements is calculated from the second complex transfer function. a third complex transfer function obtained by correcting a frequency phase error in the S subcarriers of the second complex transfer function and an antenna phase error in the M transmitting antenna elements, and extracting a component related to a living body from the third complex transfer function to calculate an M×N living body correlation matrix for each of the S subcarriers; and a third distance that 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 calculated for each of the S subcarriers;A first angle, which is a direction of the living body as seen from the transmitting antenna unit or the receiving antenna unit, is estimated.

[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, it is possible to estimate the distance from an estimation device to a living body and the direction from the estimation device to the living body 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 according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a detection target of the estimation device shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing that the phase of a received signal changes depending on the frequency and distance. [Figure 4] FIG. 4 is a schematic diagram showing the relationship between the phase error and the channel in the first embodiment. [Figure 5] FIG. 5 is a schematic diagram showing the relationship between frequency and the gradient of the phase difference. [Figure 6] FIG. 6 is a schematic diagram showing the phase of a time domain biological component transfer function matrix in the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of the positional relationship of the detection targets of the estimation device shown in FIG. [Figure 8] FIG. 8 is a diagram showing an example of the positional relationship of the detection targets of the estimation apparatus shown in FIG. 1 when a plurality of living organisms are present. [Figure 9] FIG. 9 is a flowchart showing the estimation process of the estimation device according to the first embodiment. 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 that can estimate the distance from the estimation device to a living body, etc., at low cost and with high accuracy using existing communication devices and multi-carrier radio signals such as OFDM.

[0022] That is, an estimation device according to a first aspect of the present disclosure is an estimation device for estimating a distance and an angle to a living body, the estimation device including: a transmission signal generation unit that generates a multicarrier signal obtained by modulating S (S is a natural number of 2 or more) subcarrier signals; 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 causing the multicarrier signal to be transmitted by the transmission antenna unit; a reception antenna unit having N (N is a natural number of 1 or more, provided that at least one of M and N is 2 or more) reception antenna elements; a reception unit that 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; and a reception unit that uses the reception signals observed in the first period in the reception unit to estimate a distance and an angle to a living body. a first complex transfer function calculation unit that calculates 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 the S subcarriers to which the S subcarrier signals respectively correspond, and sequentially records the plurality of received signals in a time series in the order in which they were observed; and a second complex transfer function that calculates 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. a third complex transfer function calculation unit that calculates a third complex transfer function by correcting a frequency phase error in the S subcarriers of the second complex transfer function and an antenna phase error in the M transmitting antenna elements with respect to a reference phase calculated from the positional relationship between the M transmitting antenna elements and the N receiving antenna elements from the second complex transfer function; and a biological correlation matrix calculation unit that calculates a biological correlation matrix of M×N matrix for each of the S subcarriers by extracting a biological component from the third complex transfer function.and an estimation unit that estimates 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, and a first angle, which is the direction of the living body as seen from the transmitting antenna unit or the receiving antenna unit, using the living body correlation matrix calculated for each of the S subcarriers.

[0023] With this configuration, it is possible to realize a bio-radar that measures the distance to a living body by utilizing existing communication devices by using a multi-carrier signal such as OFDM for the transmission signal. For example, receivers for multi-carrier signals such as OFDM are already widespread in mobile phones, television broadcast receivers, wireless LAN devices, etc., and it is possible to realize a bio-radar that measures the distance to a living body at lower cost than when using unmodulated signals.

[0024] An estimation device according to a second aspect of the present disclosure is the estimation device according to the first aspect, wherein the third complex transfer function calculation unit includes a frequency phase correction unit that calculates, for each of the M×N propagation paths between the M transmitting antenna elements and the N receiving antenna elements, a frequency phase correction value for correcting a frequency phase error in the S subcarriers, based on (i) an ideal complex transfer function for each of the M×N propagation paths between the M transmitting antenna elements and the N receiving antenna elements, the ideal complex transfer function being obtained based on M×N inter-antenna distances between each of the M transmitting antenna elements and each of the N receiving antenna elements, and (ii) a reference complex transfer function matrix including the M×N complex transfer functions observed in a second time period, and corrects the complex transfer function for the first time period. This makes it possible to eliminate errors due to the influence of the phase characteristics of the internal circuits or antennas of the transmitting unit and the receiving unit, and to measure the distance from the estimation device to the living body with higher accuracy.

[0025] An estimation device according to a third aspect of the present disclosure is the estimation device according to the first or second aspect, wherein the third complex transfer function calculation unit includes an antenna phase correction unit that calculates, for each of the S subcarriers, an antenna phase correction value for correcting antenna phase errors in the M×N combinations based on (i) ideal complex transfer functions for each of M×N propagation paths between the M transmitting antenna elements and the N receiving antenna elements, the ideal complex transfer functions being obtained based on M inter-antenna distances between the M transmitting antenna elements and the N receiving antenna elements, and (ii) a reference complex transfer function matrix including the M×N complex transfer functions observed in a second time period, and corrects the complex transfer function for the first time period. This makes it possible to eliminate errors due to the influence of internal circuits or phase characteristics of antennas in the transmitting and receiving units, and to measure the distance from the estimation device to the living body with higher accuracy.

[0026] An estimation device according to a fourth aspect of the present disclosure is an estimation device according to any one of the first to third aspects, and includes a matrix transformation unit that transforms the third complex transfer function consisting of M×N×S elements into a complex transfer function vector of A×1 or 1×A (A is an integer of 2 or more and M×N×S or less), and the biometric correlation matrix calculation unit calculates the biometric correlation matrix of the M×N matrix for each of the S subcarriers based on the 1×A complex transfer function vector. Therefore, the position of the biometric device can be estimated more accurately based on the estimation device.

[0027] An estimation device according to a fifth aspect of the present disclosure is the estimation device according to any one of the first to fourth aspects, wherein the estimation unit estimates the third distance and the first angle using any one of a MUSIC (MUltipleSIgnal Classification) method, a Capon method, and a beamformer method, thereby enabling the position of the living body relative to the estimation device to be estimated with higher accuracy.

[0028] An estimation method according to a first aspect of the present disclosure is an estimation method for estimating a distance and an angle to a living body, the method comprising: generating a multicarrier signal in which S (S is a natural number of 2 or more) subcarrier signals are modulated; processing the multicarrier signal and outputting it to a transmitting antenna unit having M (M is a natural number of 1 or more) transmitting antenna elements, thereby transmitting the multicarrier signal from the transmitting antenna unit; observing, for a first period corresponding to a cycle derived from activity of the living body, 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 formed when the multicarrier signals transmitted from each of the M transmitting antenna elements are reflected or scattered by the living body; and using the plurality of received signals observed in the first period, 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, estimating a first complex signal representing a propagation characteristic between the transmitting antenna element and the receiving antenna element in the combination. a plurality of element transfer functions for each of the S subcarriers corresponding to the S subcarrier signals, the plurality of received signals being sequentially recorded in a time series in the order in which they were observed; a second complex transfer function is calculated 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; and a reference phase calculated from the second complex transfer function based on a positional relationship between the M transmitting antenna elements and the N receiving antenna elements. a third complex transfer function obtained by correcting a frequency phase error in the S subcarriers of the second complex transfer function and an antenna phase error in the M transmitting antenna elements, and extracting a component related to a living body from the third complex transfer function to calculate an M×N living body correlation matrix for each of the S subcarriers; and a third distance that 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 calculated for each of the S subcarriers;A first angle, which is a direction of the living body as seen from the transmitting antenna unit or the receiving antenna unit, is estimated.

[0029] With this configuration, it is possible to realize a bio-radar that measures the distance to a living body by utilizing existing communication devices by using a multi-carrier signal such as OFDM for the transmission signal. For example, receivers for multi-carrier signals such as OFDM are already widespread in mobile phones, television broadcast receivers, wireless LAN devices, etc., and it is possible to realize a bio-radar that measures the distance to a living body at lower cost than when using unmodulated signals.

[0030] A program according to a fifth aspect of the present disclosure is a program for causing a computer to execute the estimation method according to the sixth aspect.

[0031] These comprehensive 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.

[0032] 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.

[0033] (Embodiment 1) Hereinafter, a method for estimating the distance and direction from the estimation device 100 to a living body that is a detection target, performed by the estimation device 100 according to the first embodiment, will be described with reference to the drawings.

[0034] In the first embodiment, the case of the MISO system in which there are multiple transmitting antennas will be described, but the present invention can also be applied to the SIMO system in which there are multiple receiving antennas or the MIMO system in which there are multiple transmitting antennas and multiple receiving antennas.

[0035] [Configuration of Estimation Device 100] Fig. 1 is a block diagram showing an example of the configuration of an estimation device 100 according to Embodiment 1. Fig. 2 is a diagram showing an example of a detection target of the estimation device 100 shown in Fig. 1.

[0036] 1 includes a transmitting antenna unit 111, a transmitting unit 12, a transmitting signal generating unit 13, a receiving antenna unit 21, a receiving unit 22, a complex transfer function calculating unit 123, an asynchronous component correcting unit 124, a frequency phase correcting unit 125, an antenna phase correcting unit 126, a phase correcting unit 127, a matrix transforming unit 128, a biological correlation matrix calculating unit 129, an estimating unit 130, and a positioning unit 131. The estimation device 100 estimates the location of a living body 50 using the estimation device 100 as a reference for direction or position.

[0037] [Transmitting antenna section 111] The transmitting antenna unit 111 has M (M is a natural number equal to or greater than 2) transmitting antenna elements. As described above, the transmitting antenna elements transmit multicarrier signals (transmitting waves) generated by the transmitting unit 12, which will be described later.

[0038] [Transmission signal generation unit 13] The transmission signal generation unit 13 generates a multicarrier signal in which S subcarrier signals are modulated for each of the M transmission antenna elements included in the transmission antenna unit 111. The transmission signal generation unit 13 generates S subcarrier signals corresponding to S subcarriers in different frequency bands, and multiplexes the generated S subcarrier signals to generate a multicarrier signal. In this embodiment, an example will be described in which the transmission signal generation unit 13 generates an OFDM signal as the multicarrier signal. However, as long as the multicarrier signal is obtained by multicarrier modulation, the transmission signal generation unit 13 is not limited to generating an OFDM signal in which the subcarriers are orthogonal to each other, 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 S subcarriers are multiplexed.

[0039] Furthermore, the signal generated by the transmission signal generating unit 13 may be used in common with the signal used for communication.

[0040] [Transmitter 12] The transmitter 12 performs appropriate processing on the signal generated by the transmission signal generator 13 to generate a transmission wave. Examples of the 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. 2, the transmitter 12 outputs the processed multicarrier signal to the transmitting antenna unit 111, causing the transmitting antenna unit 111 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 2) transmitting antenna elements provided in the transmitting antenna unit 111.

[0041] [Receiving antenna part 21] The receiving antenna unit 21 has N receiving antenna elements, where N is a natural number equal to or greater than 1. In this embodiment, the receiving antenna unit 21 includes one receiving antenna element. As shown in FIG. 2, for example, the one receiving antenna element receives signals (received signals) transmitted from M transmitting antenna elements and reflected by a living body 50.

[0042] [Receiver 22] The receiving unit 22 observes a received signal received by one receiving antenna element, which includes a reflected signal resulting from reflection or scattering of a multicarrier signal transmitted from M transmitting antenna elements by a living organism 50, for a first period corresponding to a cycle resulting from activity of the living organism 50. The cycle resulting from activity of the living organism is a cycle resulting from the living organism (biological fluctuation cycle) which 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 50.

[0043] The receiver 22 converts a high-frequency signal received by one receiving antenna element into a low-frequency signal that can be processed. The receiver 22 then demodulates the M OFDM signals transmitted by the M transmitting antenna elements into S×M subcarrier signals. Each of the S×M subcarrier signals is represented by an IQ symbol. The receiver 22 outputs S×M sets of subcarrier signals obtained by converting the high-frequency signals received by the N receiving antenna elements (one in this embodiment) to the complex transfer function calculator 123, at least for a first period.

[0044] The receiving unit 22 may constantly observe the received signal received by the receiving antenna unit 21 and continuously or periodically transmit S×M subcarrier signals (IQ symbols) to the complex transfer function calculation unit 123.

[0045] [Complex transfer function calculation unit 123] The complex transfer function calculation unit 123 calculates, for each of M×N (M in this embodiment) combinations of M (two or more in this embodiment) transmitting antenna elements and N (one in this embodiment) receiving antenna elements, a plurality of complex transfer functions representing propagation characteristics between the transmitting antenna elements and receiving antenna elements in the combination, for each of S subcarriers to which the S subcarrier signals correspond, using a plurality of received signals observed in the first period by the receiving unit 22. Note that the M×N combinations are all possible combinations when M transmitting antenna elements and N receiving antenna elements are combined one-to-one.

[0046] In this embodiment, the complex transfer function calculation unit 123 uses the S×M subcarrier signals transmitted from the receiving unit 22 to calculate a first complex transfer function representing the propagation characteristics between each transmitting antenna element and each receiving antenna element for each of the S×M subcarrier signals.

[0047] The calculated first complex transfer function matrix also includes reflected waves that do not pass through the living body 50, such as direct waves and reflected waves from fixed objects.

[0048] A method for calculating the first complex transfer function from one subcarrier signal includes a method for dividing the received IQ symbol by a known signal such as a pilot signal or a guard interval signal.

[0049] The complex transfer function calculation unit 123 may continuously or periodically calculate the complex transfer function matrix at all times by using each of the S subcarrier signals output by the receiving unit 22. With this configuration, when the estimating device 100 is configured to share the hardware of a communication device, the complex transfer function matrix that is constantly calculated for use in processing by the communication device can also be used in the estimating device 100. The complex transfer function calculation unit 123 is an example of a first complex transfer function calculation unit.

[0050] The complex transfer function calculation unit 123 may perform singular value decomposition on the first complex transfer function according to Equation 1, and output the right singular vector V obtained by the singular value decomposition instead of the first complex transfer function h0.

[0051]

number

[0052] Here, H represents a Hermitian matrix. This allows the amount of data passed to the next stage to be reduced. When performing singular value decomposition, the same processing can be performed by replacing h with V in the following explanation.

[0053] [Asynchronous component correction unit 124] The first complex transfer function matrix calculated by the complex transfer function calculation unit 123 includes a time-varying phase error component. This error component is called an asynchronous component. The asynchronous component is generated due to clock fluctuations between the transmitter 12 and the receiver 22, timing fluctuations in digital-to-analog conversion of the transmitted signal or analog-to-digital conversion of the received signal, etc.

[0054] The asynchronous component corrector 124 calculates a second complex transfer function by removing the asynchronous component from the first complex transfer function matrix while leaving the phase change originating from the living body 50.

[0055] In this embodiment, a method using singular value decomposition will be described as a method for removing asynchronous components. The asynchronous components are superimposed equally on components that have passed through any propagation path between the transmitting antenna unit 111 and the receiving antenna unit 21. On the other hand, the phase change caused by the living body 50 is superimposed only on components that have passed through propagation paths where the living body 50 has reflected or scattered signals. That is, the asynchronous component correction unit 124 extracts components that are less affected by reflection or scattering by the living body 50 from the first complex transfer function and divides these components from the total. This allows the asynchronous component correction unit 124 to remove the asynchronous components from the first complex transfer function while leaving the components caused by the living body 50. Specifically, when the first complex transfer function matrix is ​​h0(t), the asynchronous component correction unit 124 performs singular value decomposition into left singular vectors U(t), right singular vectors V(t), and singular value vectors Σ(t) as shown in Equation 2.

[0056]

number

[0057] Each singular value vector obtained in this manner represents the propagation path of each of the multiple transmission signals between the transmitting antenna unit 111 and the receiving antenna unit 21, and the left singular vector u1(t) and the right singular vector v1(t) corresponding to the largest singular value correspond to the propagation of the direct wave between the transmitting antenna unit 111 and the receiving antenna unit 21.

[0058] Next, the asynchronous component corrector 124 obtains a second complex transfer function matrix h′(t) in which the asynchronous components have been corrected using the left singular vector u1(t) and the right singular vector v1(t), as shown in Equation 3.

[0059]

number

[0060] Although the method using singular value decomposition has been described in this embodiment, a reference element may be determined from the elements of the complex transfer function matrix with M rows and S columns, and the complex transfer function matrix at each time may be normalized (divided) by the reference element. This operation also makes it possible to remove asynchronous components. The reference element of the complex transfer function is an example of a direct wave component extracted from multiple received signals that does not pass through the living body 50. The reference element of the complex transfer function is not limited to an element obtained by singular value decomposition, but may be any one element of the first complex transfer function, an average of multiple elements of the first complex transfer function, or a direct wave component obtained by eigenvalue decomposition of the correlation matrix of the first complex transfer function.

[0061] In this way, the asynchronous component corrector 124 calculates the second complex transfer function by dividing all elements of the first complex transfer function by the direct wave component extracted using one or more elements of the first complex transfer function. The direct wave component is a component extracted from a plurality of received signals that does not pass through the living body 50. The asynchronous component corrector 124 is an example of a second complex transfer function calculator.

[0062] [Frequency phase correction unit 125] The frequency phase correction unit 125 obtains the second complex transfer function matrix h′ calculated by the asynchronous component correction unit 124, 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 needs to be corrected will be explained using Figure 3. Figure 3 is a schematic diagram showing how the phase of a received signal changes depending on the frequency and distance.

[0063] 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 1301-A, 1301-B, and 1301-C in Figure 3 are signals of different frequencies transmitted from the transmitting antenna unit 111 with the same phase, and it can be seen that the phases become more different as the propagation distance increases (1302-B, 1302-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.

[0064] FIG. 4 is a diagram showing the correspondence between the above-mentioned phase error and the channel (complex transfer function).

[0065] 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 50.

[0066] Next, a specific operation of the frequency phase correction unit 125 will be described. The frequency phase correction unit 125 acquires the second complex transfer function matrix h' and corrects the frequency phase error. Here, the frequency phase error refers to the difference between the phase of the second complex transfer function matrix and that of the reference subcarrier signal S0 that is not caused by spatial propagation between the antennas. Specifically, the frequency phase error includes errors caused by the frequency characteristics of the transmitting antenna unit 111 and the receiving antenna unit 21, the electrical length of the circuitry inside the transmitting unit 12, the electrical length of the circuitry inside the receiving unit 22, etc. The phase error is the phase error e jΦtxand the phase error e due to the receiving antenna unit 21 and the receiving unit 22. jΦrx Includes:

[0067] The second complex transfer function matrix h′ received by the frequency phase correction unit 125 is expressed by the following equation 4.

[0068]

number

[0069] The second complex transfer function matrix h' is an M x S matrix. M elements included in the same column of the second complex transfer function matrix h' are elements generated by received signals of the same subcarrier (i.e., the same frequency), and are elements based on signals transmitted by M different transmitting antenna elements. Furthermore, S elements included in the same row of the second complex transfer function matrix h' are elements generated by signals of the same transmitting antenna element, and are elements based on S different subcarrier signals. The frequency phase correction unit 125 calculates a frequency phase correction value for each row of the second complex transfer function matrix, i.e., for each antenna, using a predetermined method. Here, the method for calculating the correction value will be described, focusing on the j-th row. First, the frequency phase correction unit 125 calculates a frequency phase correction value d between the j-th transmitting antenna element and the receiving antenna element, which is input in advance. j Based on this, the ideal channel between the antenna elements, h ideal1 where h ideal1 is a complex vector having elements of the number S of subcarriers, and the i-th element is calculated using Equation 5.

[0070]

number

[0071] where k i is the wave number of the i-th subcarrier. ideal1 is the ideal complex transfer function between the transmitting and receiving antenna elements, obtained based on the inter-antenna distance between the transmitting and receiving antenna elements.

[0072] Next, the frequency phase correction unit 125 acquires from the asynchronous component correction unit 124 a reference complex transfer function matrix including M×S complex transfer function matrices observed during a second reference period. The second period corresponds to a period resulting from the activity of the living organism 50. The period resulting from the activity of the living organism is a period resulting from the living organism (biological fluctuation period) that is at least half a period of any one of the periods of breathing, heartbeat, and body movement of the living organism 50. Note that the measurement of the reference complex transfer function matrix is ​​preferably performed in an unattended state where there is little influence from the living organism, but the influence from the living organism may also be included. The reference complex transfer function matrix may use the initial complex transfer function matrix acquired from the complex transfer function calculation unit 123. Alternatively, the frequency phase correction unit 125 may calculate a new reference complex transfer function matrix based on data at a timing with little fluctuation obtained by simultaneously calculating the time fluctuation of the absolute value of the complex transfer function, and update the reference complex transfer function matrix with the calculated new reference complex transfer function matrix. In this embodiment, since there are M transmitting antenna elements and one receiving antenna element, the reference complex transfer function matrix is ​​a matrix h meas is.

[0073] Next, the frequency phase correction unit 125 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 frequency phase correction unit 125 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 6. cal1 is calculated.

[0074]

number

[0075] Frequency phase correction value h cal1is the same if the reference complex transfer function matrix does not change. Therefore, the frequency phase correction unit 125 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 frequency phase correction unit 125 may use the frequency phase correction value h cal1 Once calculated, the frequency phase correction value h cal1 does not need to be calculated.

[0076] [Antenna phase correction unit 126] The antenna phase correction unit 126 obtains the second complex transfer function matrix h′ calculated by the asynchronous component correction unit 124, and calculates an antenna phase correction value h cal2 Here, the antenna phase error refers to the difference between the phase of the reference transmitting antenna element in the second complex transfer function matrix h' and that which is not due to spatial propagation between antennas. Specifically, the antenna phase error includes errors due to the influence of the frequency characteristics of the transmitting antenna unit 111 and the receiving antenna unit 21, the electrical length of the circuit inside the transmitting unit 12, the electrical length of the circuit inside the receiving unit 22, etc. The antenna phase error is the phase error e jΦtx and the phase error e due to the receiving antenna unit 21 and the receiving unit 22. jΦrx Includes:

[0077] The second complex transfer function matrix h′ received by the antenna phase correction unit 126 is expressed by the following equation 7.

[0078]

number

[0079] The second complex transfer function matrix h' is an M x S matrix. M elements included in the same column of the second complex transfer function matrix h' are elements generated by received signals of the same subcarrier (i.e., the same frequency), and are elements based on signals transmitted by M different transmitting antenna elements. Furthermore, S elements included in the same row of the second complex transfer function matrix h' are elements generated by signals of the same transmitting antenna element, and are elements based on S different subcarrier signals. The antenna phase correction unit 126 calculates an antenna phase correction value for each column of the second complex transfer function matrix, i.e., for each frequency, using a predetermined method. Here, a method for calculating the correction value will be described focusing on the i-th column. First, the antenna phase correction unit 126 calculates the distance d between the j-th transmitting antenna element and the receiving antenna element, which is input in advance. j Based on this, the ideal channel between the antenna elements, h ideal2 where h ideal2 is a complex vector having elements of the number M of transmitting antenna elements, and the j-th element is calculated using Equation 8.

[0080]

number

[0081] where k i is the wave number of the i-th subcarrier. ideal2 is the ideal complex transfer function between the transmitting and receiving antenna elements, obtained based on the inter-antenna distance between the transmitting and receiving antenna elements.

[0082] Next, the antenna phase correction unit 126 acquires from the asynchronous component correction unit 124 a reference complex transfer function matrix including M×S complex transfer function matrices observed during a second reference period. The second period corresponds to a period resulting from the activity of the living organism 50. The period resulting from the activity of the living organism 50 is a period resulting from the activity of the living organism (biological fluctuation period) that is at least half a period of any one of the periods of breathing, heartbeat, and body movement of the living organism 50. Note that the measurement of the reference complex transfer function matrix is ​​preferably performed in an unattended state where there is little influence from the living organism, but influence from the living organism may also be included. The reference complex transfer function matrix may use the first second complex transfer function matrix acquired from the asynchronous component correction unit 124. Alternatively, the antenna phase correction unit 126 may calculate a new reference complex transfer function matrix based on data obtained at a time when there is little fluctuation by simultaneously calculating the time fluctuation of the absolute value of the complex transfer function, and update the reference complex transfer function matrix with the newly calculated reference complex transfer function matrix. Alternatively, a reflected wave from a living organism at a known position may be used as the reference complex transfer function matrix. In this embodiment, since there are M transmitting antenna elements and one receiving antenna element, the reference complex transfer function matrix is ​​a matrix h meas is.

[0083] Next, the antenna phase correction unit 126 calculates the ideal channel h ideal2 and the reference complex transfer function (channel h meas ) and calculates a correction value for correcting the antenna phase error in the M transmitting antenna elements. Specifically, the antenna phase correction unit 126 calculates a correction value for correcting the antenna phase error in the M transmitting antenna elements based on the ideal channel h ideal2 and the measured reference complex transfer function matrix h meas Calculate the ratio of this to the antenna phase correction value h cal2 Specifically, the antenna phase correction value h is calculated as follows: cal2 Ask for.

[0084]

number

[0085] Antenna phase correction value hcal2 is the same if the reference complex transfer function matrix does not change. Therefore, the antenna phase correction unit 126 calculates the antenna phase correction value h cal2 In other words, the antenna phase correction unit 126 may once store the antenna phase correction value h cal2 If you calculate this, the antenna phase correction value h cal2 does not need to be calculated.

[0086] In this embodiment, the operation of the frequency phase correction unit 125 is described before the operation of the antenna phase correction unit 126, but the actual order of execution is not limited to this. In other words, the operation of the frequency phase correction unit 125 may be performed before or after the operation of the antenna phase correction unit 126, or may be performed simultaneously (in parallel).

[0087] [Phase correction unit 127] Next, the phase correction unit 127 calculates the frequency phase correction value h cal1 and antenna phase correction value h cal2 Based on the above, the second complex transfer function matrix h′ is corrected according to the following equation 10 to calculate the third complex transfer function matrix h″.

[0088]

number

[0089] Note that the frequency phase correction unit 125, the antenna phase correction unit 126, and the phase correction unit 127 correct the second complex transfer function matrix h' to calculate the third complex transfer function matrix h'', and therefore the frequency phase correction unit 125, the antenna phase correction unit 126, and the phase correction unit 127 are an example of a third complex transfer function calculation unit that calculates the third complex transfer function matrix h''. The third complex transfer function calculation unit calculates the third complex transfer function matrix h'' by correcting the frequency phase errors in the S subcarriers of the second complex transfer function matrix h' and the antenna phase errors in the M transmitting antenna elements from the second complex transfer function matrix h', using offset values ​​with respect to a reference phase calculated from the positional relationship between the M transmitting antenna elements and the M receiving antenna elements.

[0090] [Matrix transformation part 128] The third complex transfer function matrix h'' calculated by the phase corrector 127 is expressed by Equation 11.

[0091]

number

[0092] The matrix transformation unit 128 extracts any one row and one column from the third complex matrix, rearranges the extracted one row and one column as a vector, and generates a first complex transfer function vector h v For example, when the first row and the first column are extracted, v is expressed by Equation 12.

[0093]

number

[0094] [Biological correlation matrix calculation unit 129] The biological correlation matrix calculation unit 129 calculates the first complex transfer function vector h calculated by the matrix transformation unit 128 for each of the S subcarriers and for each of the M×N combinations. vThen, the biological correlation matrix calculation unit 129 calculates the first complex transfer function vector h v By extracting components related to the living body from the matrix, a living body component transfer function matrix expressed by an M×N dimensional matrix is ​​calculated for each of the S subcarriers.

[0095] Here, the biological component transfer function matrix is ​​obtained by extracting reflected waves or scattered waves (biological components) contained in the received signal that have passed through the living body 50. Methods for determining biological components from complex transfer functions recorded in time series include the Fourier transform disclosed in Patent Document 1 and a method using difference information disclosed in Patent Document 2.

[0096] For example, in the method using the Fourier transform, the first complex transfer function vector h v is Fourier transformed for the observation time (slow time) to extract only specific frequency components, and the biological component complex transfer function vector h fft Here, the biological component complex 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 complex transfer function vector h fft is further inverse Fourier transformed in the subcarrier direction to obtain the biological component complex transfer function vector h ifft By calculating the time from when the signal containing the biological component is transmitted from the transmitting unit 12 until when it is received by the receiving unit 22, the time is calculated.

[0097] where the complex transfer function vector h fftThe relationship between the frequency (column direction of the matrix) and phase of is shown in Figure 5. The solid line 1101 shows how the phase of each component of the biological component transfer function matrix fluctuates depending on the subcarrier frequency when the biological component 50 is present at a certain position. The phase here is the difference from the phase at the frequency of the reference subcarrier S0. When the biological component 50 approaches the transmitting antenna or receiving antenna from the above position, the path length of the radio waves reflected by the biological component 50 becomes shorter, so the slope of the graph becomes gentler, as shown by the dashed line 1102. In principle, it is possible to estimate the ToF (Time Of Flight) or the distance to the biological component from the slope of this graph. Specifically, this biological component transfer function matrix h fft Further, the time domain biological component transfer function matrix h ifft By calculating the time from when the signal containing the biological component is transmitted from the transmitting unit 12 until when it is received by the receiving unit 22, the time can be calculated.

[0098] Figure 6 shows the time domain biological component transfer function matrix h ifft 5 shows the relationship between time (column direction of the matrix) and phase. The phase changes of the solid line 1101 and dashed line 1102 in Fig. 5 appear as peaks shown by the solid line 1201 and dashed line 1202, respectively. However, using the time resolution Δt and the subcarrier bandwidth B found here, this can be expressed as Equation 13.

[0099]

number

[0100] 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.

[0101] 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 129 calculates the biological component complex transfer function vector h fft Correlation matrix R' f (Biocorrelation matrix) is calculated according to the following equation 14.

[0102]

number

[0103] Here, E[·] in Equation 14 represents the average calculation in the column direction, i.e., for each transmitting antenna, in the frequency direction that may include the influence of a living body, and m represents the index number from 1 to M of the transmitting antenna.

[0104] In this way, the biological correlation matrix calculation unit 129 extracts components related to the biological body from the third complex transfer function matrix h'' to calculate an M×N biological correlation matrix for each of the S subcarriers.

[0105] [Estimation section 130] The estimation unit 130 estimates the correlation matrix R′ calculated by the biological correlation matrix calculation unit 129. f First, the estimation unit 130 calculates the biological 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; for example, if there is one target, there is only the first eigenvector. Also, the eigenvectors corresponding to the signal are k eigenvectors from the first eigenvector to the k-th eigenvector if there are k targets (k is a natural number of 2 or more). Also, the eigenvectors corresponding to noise refer to eigenvectors other than the eigenvector corresponding to the signal.

[0106] Using the eigenvectors obtained in this way, the MUSIC spectrum P MUSIC Calculate (l,θ).

[0107]

number

[0108] Here, a(l, θ) represents the steering vector, which is calculated using Equation 16.

[0109]

number

[0110] Here, the order of the elements of the steering vector is the same as the transformation performed by the matrix transformation unit 128 when calculating the first complex transfer function vector from the third complex transfer function matrix. i represents the wavelength of the i-th subcarrier, and l represents the total distance from the reference position of the transmitting antenna (for example, the center of the first antenna element) to the receiving antenna via the living body 50. i is the difference between the total distance from the i-th transmitting antenna element to the receiving antenna element via the living body 50 and the total distance from the reference transmitting antenna element to the receiving antenna element via the living body 50. The MUSIC spectrum P MUSIC The l at which (l, θ) takes the maximum value corresponds to the sum (third distance) of the distance a (first distance) and the distance b (second distance) in FIG. 2. The distance a (first distance) is the distance between the transmitting antenna element and the living body 50. The distance b (second distance) is the distance between the receiving antenna element and the living body 50. Also, P MUSIC The θ at which (l, θ) takes the maximum value corresponds to the estimated value of the direction (first angle) from the transmitting antenna element to the living body 50 in Fig. 2. In other words, the estimation unit 130 estimates the MUSIC spectrum P MUSIC The third distance can be calculated by calculating the l that takes the maximum value of (l,θ), and the MUSIC spectrum P MUSIC The first angle can be estimated by calculating θ at which (l, θ) takes the maximum value. In this way, the estimation unit 130 estimates the third distance, which is the sum of the first distance and the second distance between the transmitting antenna unit 111 and the living body 50, and the first angle, which is the direction of the living body 50 as seen from the transmitting antenna element, using the living body correlation matrix calculated for each of the S subcarriers.

[0111] In this embodiment, the angle from the transmitting antenna element is estimated, but the angle from the receiving antenna element may be estimated using a device equipped with a plurality of receiving antenna elements.

[0112] [Positioning Unit 131] The positioning unit 131 calculates the coordinates of the living body 50 based on the third distance L and the first angle θ estimated by the estimation unit 130. Fig. 7 is a diagram showing the relationship between the living body 50, the transmitting antenna unit 111, the receiving antenna unit 21, the third distance L, and the first angle θ. When the third distance L, which corresponds to the sum of the first distance a and the second distance b in Fig. 7, is determined, it is found that the position of the living body 50 is on the circumference of the ellipse 1203, and further, since the first angle θ, which is the angle from the transmitting antenna unit 111, is determined, the position of the living body 50 is determined to be one point on the circumference of the ellipse 1203. A method for calculating the coordinates of the living body 50 will be described below using mathematical formulas.

[0113] First, the positioning unit 131 calculates the first distance a from the law of cosines using the third distance L, the first angle θ, and the inter-antenna distance d. Specifically, the first distance a is calculated by the following equation 17.

[0114]

number

[0115] Finally, the positioning unit 131 calculates the coordinates (x, y) of the living body 50 using the first distance a and the first angle θ, using the following equation 18.

[0116]

number

[0117] In this embodiment, the matrix transformation unit 128 transforms the third complex transfer function matrix to simultaneously include elements in both the row and column directions. However, the estimation unit 130 may perform the MUSIC algorithm separately for each of the row and column directions. As a result, the estimation unit 130 may separately calculate the third distance and the first angle. In this case, even when there are two or more living bodies, the estimation unit 130 can estimate the third distance and the first angle for multiple living bodies 50-1 and 50-2 as shown in FIG. 8, estimate combinations of the third distance and the first angle based on the magnitude relationship between the eigenvalues ​​of the correlation matrix, and calculate the coordinates of each living body. As in this embodiment, by expanding the steering vector used in calculating the MUSIC spectrum to two dimensions (distance and angle), it is possible to simultaneously estimate combinations of the third distance and the first angle for multiple people. The estimation unit 130 can also simultaneously estimate the angle or distance from another transmitting or receiving antenna element by further expanding the dimension of the steering vector.

[0118] Furthermore, when the third distance and the first angle are estimated separately, the estimation unit 130 can improve the estimation accuracy of the third distance or the first angle by performing singular value decomposition or eigenvalue decomposition on the third complex transfer function matrix h'' and performing beamforming in a specific direction as shown in Equation 2 and Equation 3.

[0119] [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. 9 is a flowchart showing the estimation process of the estimation device 100 in this embodiment.

[0120] The estimation apparatus 100 transmits a multicarrier signal including S subcarrier signals from M transmitting antenna elements (S1000).

[0121] Next, the estimation apparatus 100 receives the multicarrier signals transmitted in step S1000 using one or more receiving antenna elements (S1100).

[0122] Next, the estimation apparatus 100 calculates a first complex transfer function matrix h from the received multicarrier signal (S1200).

[0123] Next, the estimation apparatus 100 corrects the asynchronous components of the calculated first complex transfer function matrix h to calculate a second complex transfer function matrix h' (S1300).

[0124] Next, the estimation device 100 calculates a frequency-phase correction value h based on the second complex transfer function matrix h'. cal1 is calculated (S1400).

[0125] Next, the estimation device 100 calculates the antenna phase correction value h based on the second complex transfer function matrix h'. cal2 (S1500) Note that step S1400 may be performed before or after step S1500, or may be performed in parallel with step S1500.

[0126] Next, the estimation device 100 calculates the calculated frequency phase correction value h cal1 and antenna phase correction value h cal2 Based on the above, a third complex transfer function matrix h'' is calculated (S1600).

[0127] Next, the estimation apparatus 100 extracts components related to the living body from the third complex transfer function matrix h'' to calculate an M×N living body correlation matrix for each of the S subcarriers (S1700).

[0128] Next, the estimation apparatus 100 estimates the third distance L and the first angle θ using the MUSIC algorithm based on the biological correlation matrix (S1800).

[0129] Finally, the estimation device 100 estimates the position of the living body 50 based on the third distance L and the first angle θ (S1900).

[0130] [Effects, etc.] According to this embodiment, the coordinates of a living body can be estimated using an estimation device with a MISO or SIMO configuration.

[0131] As described above, according to the present disclosure, it is possible to 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 with high accuracy.

[0132] 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.

[0133] For example, in the first and second embodiments, distance estimation and position estimation of a living body 50 have been described as an example, but the present invention is not limited to the living body 50. When a high-frequency signal is irradiated, the present invention can be applied to various moving objects (machines, etc.) that, due to their activity, give a Doppler effect to the reflected wave.

[0134] 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.

[0135] 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]

[0136] 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 ranging sensors and direction estimation methods that are installed 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]

[0137] 12 Transmitter 13 Transmission signal generator 21 Receiving antenna section 22 Receiving unit 50, 50-1, 50-2 Biological 100 Estimator 111 Transmitting antenna section 123 Complex transfer function calculation unit 124 Asynchronous component correction section 125 Frequency phase correction section 126 Antenna phase correction unit 127 Phase correction section 128 Matrix transformation section 129 Biological correlation matrix calculation unit 130 Estimation part 131 Positioning unit 1001 Path from the transmitting antenna to the living body 1002 Path from the receiving antenna to the living body 1101, 1102 Phase variation with frequency of complex transfer function matrix 1202, 1201 Phase after inverse Fourier transform of complex transfer function matrix 1203, 1203-1, 1203-2 oval 1301-A, 1301-B, 1301-C Phase of each subcarrier signal transmitted from the transmitting antenna unit 1302-B, 1302-C Phase change of signals with different frequencies transmitted from the transmitting antenna section

Claims

1. An estimation device for estimating a distance and an angle to a living body, a transmission signal generator that generates a multicarrier signal in which S (S is a natural number equal to or greater than 2) 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 receiving antenna elements (N is a natural number of 1 or more, provided that at least one of M and N is 2 or more); 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 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 S subcarriers to which the S subcarrier signals correspond, using the plurality of received signals observed in the first period by the receiving unit; 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; a third complex transfer function calculation unit that calculates a third complex transfer function obtained by correcting a frequency phase error in the S subcarriers of the second complex transfer function and an antenna phase error in the M transmitting antenna elements with respect to a reference phase calculated from the second complex transfer function based on a positional relationship between the M transmitting antenna elements and the N receiving antenna elements; a biological correlation matrix calculation unit that calculates a biological correlation matrix of M×N matrix for each of the S subcarriers by extracting a biological component from the third complex transfer function; an estimation unit that estimates a third distance that 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, and a first angle that is the direction of the living body as seen from the transmitting antenna unit or the receiving antenna unit, using the living body correlation matrix calculated for each of the S subcarriers. Estimation device.

2. the third complex transfer function calculation unit includes a frequency phase correction unit that calculates, for each of the M×N propagation paths, a frequency phase correction value for correcting a frequency phase error in the S subcarriers, based on (i) an ideal complex transfer function for each of the M×N propagation paths between the M transmitting antenna elements and the N receiving antenna elements, the ideal complex transfer function being obtained based on M×N inter-antenna distances between each of the M transmitting antenna elements and each of the N receiving antenna elements, and (ii) a reference complex transfer function matrix including the M×N complex transfer functions observed in a second time period, and corrects the complex transfer function for the first time period. The estimation device according to claim 1 .

3. the third complex transfer function calculation unit includes an antenna phase correction unit that calculates, for each of the S subcarriers, an antenna phase correction value for correcting an antenna phase error in the M×N combinations based on (i) an ideal complex transfer function for each of M×N propagation paths between the M transmitting antenna elements and the N receiving antenna elements, the ideal complex transfer function being obtained based on M inter-antenna distances between the M transmitting antenna elements and the N receiving antenna elements, and (ii) a reference complex transfer function matrix including the M×N complex transfer functions observed in a second time period, and corrects the complex transfer function for the first time period. The estimation device according to claim 1 .

4. a matrix transformation unit that transforms the third complex transfer function consisting of M×N×S elements into an A×1 or 1×A complex transfer function vector (A is an integer of 2 or more and M×N×S or less); The biological correlation matrix calculation unit calculates the M×N biological correlation matrix for each of the S subcarriers based on the 1×A complex transfer function vector. The estimation device according to any one of claims 1 to 3.

5. The estimation unit estimates the third distance and the first angle using any one of a MUSIC (Multiple Signal Classification) method, a Capon method, and a beamformer method. The estimation device according to any one of claims 1 to 3.

6. An estimation method for estimating a distance and an angle to a living body, comprising: generating a multicarrier signal in which S subcarrier signals (S is a natural number equal to or greater than 2) are modulated; 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 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 S subcarriers to which the S subcarrier signals respectively correspond, and sequentially recording the plurality of received signals in a time series in the order in which they were observed; 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; calculating a third complex transfer function obtained by correcting a frequency phase error in the S subcarriers of the second complex transfer function and an antenna phase error in the M transmitting antenna elements with respect to a reference phase calculated from the positional relationship between the M transmitting antenna elements and the N receiving antenna elements from the second complex transfer function; extracting a biological component from the third complex transfer function to calculate an M×N biological correlation matrix for each of the S subcarriers; Using the biological correlation matrix calculated for each of the S subcarriers, a third distance is estimated, 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, and a first angle is estimated, which is the direction of the living body as seen from the transmitting antenna unit or the receiving antenna unit. Estimation method.

7. A program for causing a computer to execute the estimation method according to claim 6.

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