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

Estimation device, estimation method, and program

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

[0002] Methods using wireless signals have been 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 using Orthogonal Frequency Division Multiplexing (OFDM) signals.

[0003] JP 2015-117972 A JP 2017-129558 A JP 2018-008021 A JP 2012-088279 A JP 2012-137340 A JP 2006-157663 A JP 2001-144722 A

[0004] 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

[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.

[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 of 1 or more) 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, and a reception antenna unit having N (N is a natural number of 1 or more) reception antenna elements, and an estimation device 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 obtained by the multicarrier signals transmitted from each of the M transmission antenna elements being reflected or scattered by a 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 that do not pass through the living body from the plurality of receiving signals, extracted using one or more elements of the first complex transfer function.

[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 of 1 or more) transmitting antenna elements, thereby transmitting the multicarrier signal from the transmitting antenna unit, and estimating a received signal that includes 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 using the plurality of received signals observed during the first period, 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 element and the receiving antenna element in that 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.

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

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

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

[0012] (Findings that Form the Basis of the Present Disclosure) Methods that utilize wireless signals are being considered as methods for determining the location of a person, etc.

[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 a radar cross section (RCS) calculated from the received power using a configuration similar to 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 including 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 including 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 included in 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 a 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 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, in the methods of Patent Documents 4 and 5, in order to obtain sufficient accuracy, the transmission pulse needs to be steep, which requires a wide frequency band, and therefore the hardware costs are higher than those of communication devices for consumer use.

[0020] The technology of Non-Patent Document 1 uses a measuring device such as a network analyzer to transmit and receive signals of multiple frequencies, thereby estimating the ToF (Time of Flight) between a transmitting antenna and a receiving antenna, as well as the distance 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 propagated between the antennas. The technology of Non-Patent Document 1 further improves resolution by estimating the ToF using the MUSIC (MUltiple SIgnal Classification) method. However, the transmitting and receiving sides must operate on the same reference frequency or be synchronized with high precision, which means that household devices such as wireless LANs cannot be used. Furthermore, only the distance between antennas can be estimated, and it is not possible to 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 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; 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) clock fluctuations between a transmitter including a transmission signal generation unit and a transmission unit that transmits from a transmission antenna unit and a receiver including a reception unit that receives by a reception antenna unit, and (2) timing fluctuations 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 in a short time with high accuracy using a wireless signal.

[0024] This configuration makes it possible to realize a biological radar by utilizing 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 each 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 that 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 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 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 the estimation device according to the seventh or eighth aspect, wherein 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.

[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 foci at the positions of the M transmitting antenna elements and the N receiving antenna elements and whose major axes have lengths equal to 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 of 1 or more) transmitting antenna elements, thereby transmitting the multicarrier signal to the transmitting antenna unit, and estimating a received signal that includes 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 using the plurality of received signals observed during the first period, 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 element and the receiving antenna element in that 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) clock fluctuations between a transmitter including a transmission signal generation unit and a transmission unit that transmits from a transmission antenna unit and a receiver including a reception unit that receives by a reception antenna unit, and (2) timing fluctuations 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 in a short time with high accuracy using a wireless signal.

[0040] This configuration makes it possible to realize a biological radar by utilizing 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 are implemented as 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] First Embodiment Hereinafter, a method for estimating a distance to a living body, which is a detection target, using an estimation device 100 according to an embodiment will be described with reference to the drawings.

[0045] [Configuration of Estimation Apparatus 100] FIG. 1 is a block diagram showing an example of the configuration of an estimation apparatus 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 distance measuring unit 1900. The estimation device 100 estimates the location of a biological body 200 based on the position 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 Generator 1200] The transmission signal generator 1200 generates a multicarrier signal in which multiple subcarrier signals are returned for each of the M transmission antenna elements included in the transmission antenna unit 1000. The transmission signal generator 1200 generates S subcarrier signals corresponding to S subcarriers (S is a natural number greater than or equal to 2) in different frequency bands, and multiplexes the generated S subcarrier signals to generate a multicarrier signal. In this embodiment, the transmission signal generator 1200 uses an OFDM signal as an example of a multicarrier signal. However, the transmission signal generator 1200 is not limited to generating an OFDM signal in which the subcarriers are orthogonal, as long as the multicarrier signal is obtained by multicarrier modulation. Other multicarrier signals, such as a simple FDM (Frequency Division Multiplexing) signal, may also be generated. Note that an 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.

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

[0049] [Transmitting Unit 1100] The transmitting unit 1100 performs appropriate processing on the signal generated by the transmitting signal generating unit 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 transmitting unit 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 transmitting antenna elements 1001 (M is a natural number greater than or equal to 1) included 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 (transmitting wave) generated by the transmitting unit 1100.

[0051] [Receiving Antenna Unit 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 the living body 200.

[0052] [Receiving unit 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 calculation 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 during a first period by the reception 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 representing 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]

[0058] [Second Complex Transfer Function Calculation Unit 1600] Here, the first complex transfer function vector h includes frequency fluctuation components derived from the transmitter and receiver, and Doppler shifts derived 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 derived from fixed objects.

[0059] The frequency fluctuation components originating from the transmitter and receiver include, for example, (i) attenuation or phase rotation due to spatial propagation of the transmitted signal, (ii) clock frequency error (f ＲＸ -f ＴＸ), (iii) sampling clock frequency error used in the radio equipment, such as in 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]

[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 ｌ Here, the element of the direct wave component is the element h １ Any element of the first complex transfer function vector h may be used, such as: 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, thereby calculating 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 consisting of the transmission signal generation unit 1200 and the transmission unit 1100 that transmits from the transmission antenna unit 1000 and the receiver consisting of the reception unit 1400 that receives by the reception antenna unit 1300, and (2) timing fluctuations of the digital-to-analog conversion of the transmission signal or the analog-to-digital conversion of the reception 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 reception 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′ for calibrating (correcting) the phase error in the frequency direction. ｃａｌ1 The phase error in the frequency direction is the phase error between multiple signals having 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 FIG. 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 transmitting and receiving signals of multiple known frequencies and measuring the phase difference. 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, in order 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 represented by the matrix obtained by the measurement. ｍｅａｓ and the spatial ideal channel h, which is expressed by 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 the 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 ｊΦｔｘ and 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 Here, h ｉｄｅａｌ is a complex vector having elements of the number S of subcarriers, and the i-th element is calculated by Equation 3.

[0069]

[0070] In this way, h ｉｄｅａｌ1 is an ideal complex transfer function between the transmitting antenna element 1001 and the receiving antenna element 1301, 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 derived from the activity of the living organism 200. The period derived from the activity of the living organism 200 is a period derived from the living organism (biological fluctuation period) that 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 the number of elements S.

[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 / phase correction value h for correcting the frequency / 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]

[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 a memory or the like, and the frequency phase correction value h stored in the memory or the like 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 If the frequency phase correction value h is calculated, the frequency phase correction value h will be calculated from the next time onwards. 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]

[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 have been 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] [Biocorrelation matrix calculation unit 1800] The biocorrelation 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 M x N combinations in chronological order, which is the order in which they were observed. Then, the biocorrelation matrix calculation unit 1800 extracts components related to the biomedical organism from the third complex transfer function vector h" observed in a first period sequentially recorded in chronological order for each of the S subcarriers and for each of the M x N combinations, thereby calculating a biocomponent transfer function vector expressed by an M x N-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 a 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 a 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, a frequency component between 0.1 Hz and 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 ｉｆｆｔ By 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'' ｆｆｔThe 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, and 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] The time domain biological component transfer function vector h'' is shown in Fig. 5. ｉｆｆｔ 4 shows the relationship between time (column direction of the matrix) and phase. The phase changes of the solid line 4100 and dashed line 4200 in FIG. 4 appear as peaks indicated by the solid line 5100 and dashed line 5200, respectively. However, the time resolution Δt obtained here is expressed by Equation 6 using the subcarrier bandwidth B.

[0085]

[0086] For example, when the bandwidth is 20 MHz, the time resolution is equivalent to 0.05 μs, which is equivalent 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 SIgnal Classification) 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]

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

[0090] [Distance measuring unit 1900] The distance measuring unit 1900 measures 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 ​​to obtain a vector U corresponding to the signal. 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 as above, the MUSIC spectrum P ＭＵＳＩＣ (d) is calculated.

[0092]

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

[0094]

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

[0096] The MUSIC spectrum P thus obtained ＭＵＳＩＣThe 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 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. Also, 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 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, among the multiple elements included in the first complex transfer function vector, may be used, each corresponding to two or more subcarriers that are adjacent in frequency among the multiple subcarriers. The two or more elements are elements that correspond to two or more subcarriers that are all adjacent to each other among the multiple subcarriers that have different frequencies. The two or more subcarriers have 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, two or more adjacent subcarriers will be referred to as K adjacent subcarriers in the subcarrier direction (K=K １ +K ２ , K. １ HA-K１ an integer of 0 or more that satisfies ≧1, K ２ is l+K ２ ≦S) are sometimes referred to as subcarriers.

[0104] For example, the l-th element h of the first complex transfer function vector h ｌ The direct wave component used for the 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]

[0106]

[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 S - K. In this case, the steering vector a(d) used in Equation 8 is calculated as shown in Equation 12.

[0108]

[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 using Equation 13 and Equation 14. As a result, the second complex transfer function vector h′ may be calculated as shown in Equation 15.

[0110]

[0111]

[0112]

[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 is calculated, and the calculated correlation matrix R Ｒ , R Ｔ By decomposing each of these into eigenvalues, the eigenvalue D Ｒ , D Ｔ 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 pair of eigenvectors u that maximizes １ , v １ multiplying the first complex transfer function vector h(t) by １ Ｈ h(t)v １ and all elements of the first complex transfer function vector h are converted into the channel components u of the direct wave. １ Ｈ h(t)v １ The second complex transfer function vector h' is calculated by dividing by

[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 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]

[0116] [Another Example of Biocorrelation Matrix] The biocorrelation 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]

[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]

[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, thereby obtaining a 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]

[0124]

[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]

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

[0128] [Operation of Estimation Device 100] The following describes 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 estimation 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 using the receiving antenna element 1301 during a second period in which no living organisms or other moving objects are 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 apparatus 100 calculates, from the S subcarrier signals observed during the second time 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 (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 apparatus 100 calculates 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 an 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] Then, the estimation device 100 calculates the ideal channel h ｉｄｅａｌ and the second complex transfer function vector h' to obtain the frequency phase correction value h ｃａｌ is calculated (S1220).

[0142] FIG. 11 is a flowchart showing the detailed distance measurement process 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 during the first period, multiple first complex transfer functions representing the propagation characteristics between the transmitting antenna element 1001 and the receiving antenna element 1301, for each of the multiple subcarriers to which the multiple subcarrier signals respectively correspond (S1340).

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

[0148] Next, the estimation apparatus 100 calculates the frequency phase correction value h ｃａｌ The second complex transfer function vector h′ is corrected using Equation 5 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 apparatus 100 calculates the MUSIC spectrum P ＭＵＳＩＣ (d) is calculated (S1380).

[0151] Finally, the estimation apparatus 100 calculates the MUSIC spectrum P ＭＵＳＩＣ The value d at which (d) is maximized is searched for, 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 the transmission signal, it is possible to estimate the distance between a living body and an antenna by utilizing an existing multicarrier transceiver.

[0153] Furthermore, by using the MUSIC method, distance measurement with fine distance resolution is possible.

[0154] Furthermore, according to the estimation device 100 of this embodiment, the position of the living body can be estimated from the intersection of the ellipse by estimating multiple third distances to the receiver using three or more transmitters.

[0155] Furthermore, according to the estimation device 100 of this embodiment, the position of the living body can be estimated from the intersection of the ellipse by estimating multiple third distances to the transmitter using three or more receivers.

[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 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 the number of M transmitting antenna elements is one and the number of N receiving antenna elements is one has been mainly described, but this is not limited to this. The number of M transmitting antenna elements may be two or more, and the number of N receiving antenna elements may be two or more. The number of M transmitting antenna elements may be two or more, and the number of N receiving antenna elements may be two or more.

[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 only needs to 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 transmission antenna unit 1000 and the receiver consisting of the reception unit 1400 that receives by the reception antenna unit 1300, and (2) timing fluctuation of the digital-to-analog conversion of the transmission signal or the analog-to-digital conversion of the reception signal. Therefore, the direction from the estimation device to the living body, the position of the living body, the identifier of the living body, etc. can be estimated with high accuracy.

[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 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.

[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.

[0165] 100 Estimation device 200 Living body 1000 Transmitting antenna unit 1001 Transmitting antenna element 1100 Transmitting unit 1200 Transmitting signal generating unit 1300, 1300-1, 1300-2, 1300-3 Receiving antenna unit 1301 Receiving antenna element 1400 Receiving unit 1500 First complex transfer function calculating unit 1600 Second complex transfer function calculating unit 1700 Third complex transfer function calculating unit 1800 Living body correlation matrix calculating unit 1900 Distance measuring unit 2001-A, 2001-B, 2001-C Phase of each subcarrier signal transmitted from the transmitting antenna unit 2002-B, 2002-C Phase change of signals with different frequencies transmitted from the transmitting antenna unit 4100, 4200 Phase change with respect to 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 generation unit that generates a multi-carrier signal modulated by a plurality of sub-carrier 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 multi-carrier signal and outputs it to the transmission antenna unit, thereby transmitting the multi-carrier signal to the transmission antenna unit; A reception antenna unit having N (N is a natural number of 1 or more) reception antenna elements; A reception unit that observes, for a first period corresponding to a period derived from the activity of the living body, a reception signal received by each of the N reception antenna elements, the reception signal including a reflection signal in which the multi-carrier signal transmitted from each of the M transmission antenna elements is reflected or scattered by the living body; A first complex transfer function calculation unit that calculates a plurality of first complex transfer functions for each of M×N combinations, which are combinations of each of the M transmission antenna elements and each of the N reception antenna elements, for each of the plurality of sub-carriers corresponding to each of the plurality of sub-carrier signals, representing the propagation characteristics between the transmission antenna element and the reception antenna element in the combination, using a plurality of the reception signals observed in the first period in the reception unit; A second complex transfer function calculation unit that calculates a second complex transfer function by dividing all elements of the first complex transfer function, which is a direct wave component extracted using one or more elements of the first complex transfer function and is a direct wave component that does not pass through the living body from the plurality of reception signals; The one or more elements used for extraction of the direct wave component include two or more elements respectively corresponding to two or more sub-carriers that are adjacent in frequency among the plurality of sub-carriers; The direct wave component is an average value of one element included in the first complex transfer function and the two or more elements; An estimation device.

2. A transmission signal generation unit that generates a multi-carrier signal modulated by a plurality of sub-carrier 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 multi-carrier signal and outputs it to the transmission antenna unit, thereby transmitting the multi-carrier signal to the transmission antenna unit; A reception antenna unit having N (N is a natural number of 1 or more) reception antenna elements; A received signal received by each of the N receiving antenna elements, the received signal including a reflected signal in which the multi-carrier signal transmitted from each of the M transmitting antenna elements is reflected or scattered by a living body, is observed for a first period corresponding to a period derived from the activity of the living body, a receiving unit; Using the plurality of received signals observed in the first period in the receiving unit, for each of the M×N combinations that are combinations of each of the M transmitting antenna elements and each of the N receiving antenna elements, a first complex transfer function representing propagation characteristics between the transmitting antenna element and the receiving antenna element in the combination is calculated for each of the plurality of sub-carriers corresponding to each of the plurality of sub-carrier signals, a first complex transfer function calculation unit; A second complex transfer function calculation unit that calculates a second complex transfer function by dividing all elements of the first complex transfer function, the direct wave component extracted using one or more elements of the first complex transfer function, the direct wave component that does not pass through the living body from the plurality of received signals; The one or more elements used for extraction of the direct wave component include two or more elements respectively corresponding to two or more sub-carriers that are adjacent in frequency among the plurality of sub-carriers; 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 an eigenvalue and an eigenvector calculated by performing eigenvalue decomposition on a correlation matrix of one element included in the first complex transfer function and the two or more elements; An estimation device.

3. Furthermore, A third complex transfer function calculation unit that calculates a third complex transfer function obtained by correcting a frequency phase error in the plurality of sub-carriers based on a 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. Furthermore, A third complex transfer function calculation unit that calculates a third complex transfer function obtained by correcting a frequency phase error in the plurality of sub-carriers 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; The estimation device according to claim 1 or 2.

5. Furthermore, Sequentially record the calculated plurality of the third complex transfer functions in the time series in the order they are observed, and calculate a bio-correlation matrix by extracting components related to the living body in the third complex transfer function, a bio-correlation matrix calculation unit; A ranging unit that estimates a third distance, which is the sum of a first distance between the transmission antenna unit and the living body and a second distance between the reception antenna unit and the living body, using the bio-correlation matrix. The estimation device according to claim 3.

6. The bio-correlation matrix calculation unit Calculates a correlation matrix of the third complex transfer function, Calculates a first vector obtained by vectorizing a lower triangular matrix excluding diagonal terms of the correlation matrix, Calculates the bio-correlation matrix by extracting components related to the living body in the first vector. The estimation device according to claim 5.

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

8. At least one of the M transmission antenna elements and the N reception antenna elements includes two antenna elements, A position estimation unit that focuses on the positions of the M transmission antenna elements and the N reception antenna elements, calculates two or more ellipses whose major axis length is the third distance, and estimates the intersection point as the position of the living body. The estimation device according to claim 5.

9. Generate a multi-carrier signal modulated by a plurality of sub-carrier signals, Process the multi-carrier signal and output it to a transmission antenna unit having M (M is a natural number of 1 or more) transmission antenna elements, thereby causing the transmission antenna unit to transmit the multi-carrier signal, A received signal 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) reception antenna elements constituting the reception antenna unit, wherein the multi-carrier signal transmitted from each of the M transmission antenna elements is a received signal including a reflected signal reflected or scattered by the living body, and is observed for a first period corresponding to a period derived from the activity of the living body. Using the plurality of received signals observed during the first period, for each of the 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 representing the propagation characteristics between the transmitting antenna element and the receiving antenna element in the combination are calculated for each of the plurality of subcarriers corresponding to the plurality of subcarrier signals respectively, A direct wave component extracted using one or more elements of the first complex transfer function, which is a direct wave component not passing through the living body from the plurality of received signals, and a second complex transfer function is calculated by dividing all elements of the first complex transfer function. The one or more elements used for the extraction of 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. 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 of the pair of eigenvalues and eigenvectors calculated by performing eigenvalue decomposition on the correlation matrix of one element and the two or more elements included in the first complex transfer function, where the eigenvalue is the maximum. Estimation method.

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