JP2019093104A - Identification apparatus and identification method - Google Patents

Abstract

To provide an identification apparatus and the like capable of reducing an equivalence error rate in biological identification.SOLUTION: An identification apparatus includes: M transmission antenna elements transmitting first transmission signals to a prescribed range containing a first living body; N receiving parts each of which has a reception antenna element, which are disposed around the periphery of the prescribed range, and which receive first reception signals containing reflection signals where the first transmission signals are reflected from the first living body each using the reception antenna elements for a prescribed period of time; a memory 41 storing teacher signals 42 as M×N second reception signals obtained for a second living body; and a circuit 40 which calculates a plurality of correlation factors from the teacher signals 42 and the M×N first reception signals obtained by reception of the first reception signal by each of the N reception parts, performs biological identification of the first living body in response to whether or not a maximum value of the plurality of calculated correlation factors exceeds a threshold value, and identifies that the first living body and the second living body are identical by a prescribed method when performing the biological identification of the first living body.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an identification apparatus and an identification method for irradiating a living body with a wireless signal and receiving a reflected signal thereof to identify the living body.

  There is known a technique of irradiating a living body with a wireless signal and receiving a reflected signal to identify the living body (for example, Patent Documents 1 and 2). Patent Document 1 discloses a device for identifying an individual driver by irradiating a driver of a car with an electromagnetic wave and extracting a heartbeat and a heart sound signal using the reflected wave. Further, Patent Document 2 discloses a method of measuring a subject's heart rate using a plurality of transceivers for a driver of a car.

  Further, for example, Patent Document 3 discloses a 360-degree radiation pattern measurement apparatus using a plurality of antennas for a subject.

JP, 2015-042293, A JP 2009-055997 A JP 2007-325621 A

  By the way, in living body identification using electromagnetic waves, living body identification is often performed by comparing teacher data and measurement data obtained by measuring a subject.

  However, when the teacher data does not include the data of the subject, there is a problem that the teacher data closest to the data of the subject is recognized as the person, and another person is erroneously accepted.

  The present disclosure has been made in view of the above-mentioned circumstances, and is equivalent to error error rate (EER: Equal Error Rate) which is a balance point between false acceptance rate (FAR) and false rejection rate (FRR). It is an object of the present invention to provide an identification device and an identification method which can reduce the size of.

  In order to achieve the above object, an identification apparatus according to an aspect of the present disclosure includes M (M is an integer of 1 or more) transmission antenna elements for transmitting a first transmission signal in a predetermined range including a first living body; N (N is an integer of 3 or more) receiving units each having a receiving antenna element and disposed around the periphery of the predetermined range, wherein the first transmission signal is reflected by the first living body N reception units each receiving a first reception signal including a reflection signal using the reception antenna element for a predetermined period, and second transmission transmitted from the M transmission antenna elements to a second living body Storing a teacher signal which is an M × N second received signal obtained by causing the N receiving units to receive in advance a second received signal including a reflected signal reflected by the second living body; Memory, the teacher signal, and Of the plurality of correlation coefficients calculated from the plurality of correlation coefficients from the M × N first reception signals obtained by receiving the first reception signals When performing biometric authentication of the first living body according to whether or not the value exceeds the threshold and performing biometric authentication of the first living body, the first living body and the second living body are identical by a predetermined method And a circuit that identifies that there is.

  Note that these general or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer readable CD-ROM, and the system, the method, the integrated circuit, the computer It may be realized by any combination of program and recording medium.

  According to the identification device according to the present disclosure, the equivalent error rate of biometric identification can be reduced.

FIG. 1: is a block diagram which shows an example of a structure of the identification device in embodiment. FIG. 2 is a diagram showing an example of the teacher signal shown in FIG. FIG. 3 is a block diagram showing an example of a detailed configuration of the circuit shown in FIG. FIG. 4 is a flowchart showing an example of the operation of the identification device in the embodiment. FIG. 5 is a flowchart showing the detailed operation of step S14 shown in FIG. FIG. 6 is a flowchart showing the detailed operation of step S15 shown in FIG. FIG. 7 is a diagram showing an environment used for a recognition test by the identification device in the embodiment. FIG. 8 is a diagram showing an example of a propagation channel calculated from a received signal received in the environment shown in FIG. FIG. 9 is a diagram showing an example of the DC removal channel obtained by removing the DC component from the propagation channel shown in FIG. FIG. 10 is a diagram showing an example of a graph in which a plurality of maximum values of the correlation coefficient are described. FIG. 11 is a diagram in which FAR and FRR are plotted when the threshold value in the embodiment is changed.

(Findings that formed the basis of this disclosure)
In Patent Documents 1 and 2, a person sitting in the driver's seat of a car is irradiated with an electromagnetic wave, and a reflected wave from the person is measured. The heart rate or heart sound is measured by performing arithmetic processing on the measured result, and the biological correlation is realized by acquiring the time correlation of the measured heart rate or heart sound. However, as described above, when the teacher data does not include the data of the subject, there is a problem that the teacher data closest to the data of the subject is recognized as the person, and another person is erroneously accepted.

  By the way, there is a relation that the person rejection rate (FRR) decreases and the false acceptance rate (FAR) increases if the threshold value used for such determination of the biometric identification is loose. On the other hand, if the threshold is tightened, the false rejection rate increases, and the false acceptance rate decreases. That is, there is no point in lowering the false acceptance rate (FAR), and it is necessary to reconcile the decrease in the false rejection rate (FRR) with the decrease in the false acceptance rate (FAR). In other words, it is required to reduce the equivalent error rate, which is the error rate at which the false acceptance rate (FAR) and the false rejection rate (FRR) become equal (which is a balance point).

  As a result of researches on this subject, the inventors have found the following things to reduce the equivalent error rate (EER) of the identification device for identifying a living body. That is, an antenna element is installed around a living body to be identified, a transmission wave is transmitted from various directions, and reception is performed by capturing reflected waves and scattered waves in various directions and capturing more features of the living body. Get a signal. Then, it has been found that, by calculating a plurality of correlation coefficients between the received signal and the teacher data, it is possible to accurately identify whether or not there is a living body to be measured in the teacher data.

  More specifically, in order to achieve the above object, the identification device according to an aspect of the present disclosure transmits M first transmission signals in a predetermined range including the first living body (M is an integer of 1 or more) And N (N is an integer of 3 or more) receiving portions disposed around the periphery of the predetermined range, the first living body including the transmitting antenna element and the receiving antenna element, N reception units each receiving a first reception signal including a reflection signal in which a transmission signal is reflected using the reception antenna element for a predetermined period, and the M transmission antenna elements for a second living body M × N second received signals obtained by causing the N receiving units to receive in advance the second received signals including the reflected signals that the transmitted second transmitted signals are reflected by the second living body A memory storing a certain teacher signal, and A plurality of correlation coefficients calculated from a master signal and M × N first reception signals obtained by the N reception units respectively receiving the first reception signals; When performing biometric authentication of the first living body and performing biometric authentication of the first living body according to whether or not the maximum value of the correlation coefficient of the first living body exceeds the threshold value, the first living body and the first living body may be And a circuit that identifies the two living bodies as identical.

  According to this, it is possible to calculate a plurality of correlation coefficients from the first reception signal which is a measurement signal obtained from the reception antenna element installed around the first living body and the teacher signal. Then, the biometric authentication is performed by identifying that the first living body and the second living body included in the teacher data are the same according to whether or not the maximum value among the plurality of correlation coefficients exceeds the threshold value. Can. As a result, it is possible to suppress an error of accepting another person as the principal when the first living body is not included in the teacher data, so that the equivalent error rate (EER) can be reduced.

  Here, for example, the circuit performs biometric authentication of the first living body when the calculated maximum value of the plurality of correlation coefficients exceeds a threshold, and the maximum value of the plurality of correlation coefficients is the threshold. When it falls below, biometric authentication of the first living body is not performed.

  Also, for example, the circuit identifies that the first living body and the second living body corresponding to the correlation coefficient having the maximum value are the same.

  Also, for example, the circuit may be configured such that a DC (Direct Current) component is removed in a predetermined method from at least the first received signal of the first received signal and the second received signal.

  As a result, it is possible to suppress the DC component, which is a noise component unnecessary for the identification of the living body, from the received signal, and the living body identification can be performed efficiently.

  Also, for example, the circuit calculates, as the plurality of correlation coefficients, a plurality of correlation coefficients between the teacher signal and each of the M × N first received signals by a sliding correlation operation. It may be

  According to this, it is possible to determine whether biometric authentication is to be performed using the maximum value of the time correlation coefficient of the sliding correlation. As a result, it is possible to suppress an error of accepting another person as the principal when the first living body is not included in the teacher data, so that the equivalent error rate (EER) can be reduced.

  Also, for example, the circuit calculates, as the plurality of correlation coefficients, a plurality of correlation coefficients between the teacher signal and each of the M × N first received signals by a sliding correlation operation. It may be

  Note that these general or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer readable CD-ROM, and the system, the method, the integrated circuit, the computer It may be realized by any combination of program and recording medium.

  Hereinafter, embodiments of the present disclosure will be described in detail using the drawings. The embodiments described below each show a preferable specific example of the present disclosure. Numerical values, shapes, materials, components, arrangement positions and connection forms of components, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present disclosure. Moreover, about the component in the following embodiment, the component which is not described in the independent claim which shows the highest concept of this indication is demonstrated as an arbitrary component which comprises a more preferable form. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

Embodiment
[Configuration of Identification Device 10]
FIG. 1: is a block diagram which shows an example of a structure of the identification device 10 in embodiment. FIG. 2 is a diagram showing an example of the teacher signal 42 shown in FIG. FIG. 3 is a block diagram showing an example of a detailed configuration of the circuit 40 shown in FIG.

  The identification device 10 in the present disclosure includes M (M is an integer of 1 or more) transmitting antenna elements, N (N is an integer of 3 or more) receiving units each having a receiving antenna element, a circuit 40, and a memory And 41.

  The M transmission antenna elements transmit transmission signals in a predetermined range A1 including the living body 50. The transmission signal is a high frequency signal such as a microwave generated by a transmitter or the like. The living body 50 is a human or the like. The living body 50 is an identification target of the identification device 10, and is a living body on which biometric authentication is performed. The predetermined range A1 is a space of a predetermined range and a space including the living body 50. In other words, the predetermined range A1 is a space in which the identification device 10 is used to identify the living body 50.

  For example, the M transmission antenna elements transmit the first transmission signal in a predetermined range A1 including the first living body which is the living body 50 to be measured. In addition, the M transmission antenna elements transmit the second transmission signal in a predetermined range A1 including the second living body which is the known living body 50 as teacher data.

  Each of the N receiving units has a receiving antenna element, and is disposed to surround the predetermined range A1. Each of the N reception units receives the reception signal including the reflection signal of which the transmission signal is reflected by the living body 50 for a predetermined period using the reception antenna element. For example, each of the N reception units receives the first reception signal including the reflection signal in which the first transmission signal is reflected by the first living body using the reception antenna element for a predetermined period. Also, for example, each of the N reception units uses the reception antenna element to multiply the teacher signal, which is the second reception signal including the reflection signal of the second transmission signal reflected by the second living body, by K for a predetermined period. Receive for a period of (K is 2 or more).

  In the present embodiment, as shown in FIG. 1, the identification device 10 includes, for example, eight transmitting / receiving units 30A to 30H, a circuit 40, and a memory 41. That is, the M transmission antenna elements and the N reception units may be configured by eight transmission / reception units 30A to 30H. The number of transmitting and receiving units is not limited to eight.

[Transmitter unit 30A to 30H]
In the present embodiment, the eight transmitting / receiving units 30A to 30H are disposed at positions around the predetermined range A1, and transmit the transmission signal to the predetermined range A1 including the living body 50 such as a human body to obtain the living body 50. Receive the received signal including the reflected signal reflected by the For example, the eight transmitting / receiving units 30A to 30H may be arranged in a circle at equal intervals, or may be arranged at a position outside the predetermined range A1.

  As shown in FIG. 1, the transmitting and receiving units 30A to 30H each have one antenna element 31A to 31H. The transmission / reception units 30A to 30H transmit transmission signals in a predetermined range A1 using the antenna elements 31A to 31H. More specifically, the transmission / reception units 30A to 30H emit microwaves as transmission signals to the living body 50 such as a human using the antenna elements 31A to 31H. The transmitting / receiving units 30A to 30H may transmit the non-modulated transmission signal using the antenna elements 31A to 31H, or may transmit the transmission signal subjected to the modulation processing. When transmitting the transmission signal subjected to the modulation process, the transmitting and receiving units 30A to 30H may further include a circuit for performing the modulation process.

  The transmitting and receiving units 30A to 30H receive the reception signal including the reflection signal which is a signal obtained by reflecting the transmission signal by the living body 50 for a predetermined period using the antenna elements 31A to 31H. The transmitting and receiving units 30A to 30H output the received signal to the circuit 40. Each of the transmitting and receiving units 30A to 30H may include a circuit for processing a received signal. In this case, each of the transmitting and receiving units 30A to 30H may convert the frequency of the received signal received into a low frequency signal. In addition, each of the transmission / reception units 30A to 30H may perform demodulation processing on the received signal. Then, each of the transmission / reception units 30A to 30H outputs a signal obtained by performing frequency conversion and / or demodulation processing to the circuit 40.

  In the example shown in FIG. 1, the transmitting unit and the receiving unit are expressed as being configured by eight transmitting / receiving units 30A to 30H each having one antenna element common to the transmitting and the receiving. Not limited to this. The eight transmission / reception units 30A to 30H are not limited to eight, and may be configured by N (N is an integer of 3 or more) transmission / reception units. Alternatively, a transmitter having M (M is an integer of 1 or more) transmitting antenna elements and a receiver having N receiving antenna elements may be separately provided.

[Memory 41]
The memory 41 is an auxiliary storage device having a non-volatile storage area, and is, for example, a read only memory (ROM), a flash memory, a hard disk drive (HDD) or the like. The memory 41 stores, for example, information used for various processes for operating the identification device 10.

  The memory 41 stores a teacher signal 42 as shown in FIG. The teacher signal 42 is a signal waveform acquired in advance for the second living body, which is the known living body 50 in the predetermined range A1. More specifically, the teacher signal 42 includes N second received signals including a reflection signal in which the second transmission signal transmitted from the M transmitting antenna elements to the second living body is reflected by the second living body. And M.times.N second received signals obtained by causing the receiving unit to receive in advance. Here, the teacher signal 42 is an M × N second received signal obtained by the N receiving units receiving the second received signal in a period of K times (K is 2 or more) of the predetermined period. It may be

  In the present embodiment, the M transmission antenna elements and the N reception units are configured by eight transmission / reception units 30A to 30H as shown in FIG. An example of the teacher signal 42 in this case will be described with reference to FIG. The teacher signal 42 shown in FIG. 2 is an example of a reception signal received by one receiver in a measurement period.

  The teacher signal 42 shown in FIG. 2 is a reflected signal in which transmission signals transmitted from the antenna elements 31A to 31H are reflected by the surface of the living body 50 with respect to a known living body 50 (second living body) in the predetermined range A1. These are time response waveforms of a plurality of received signals obtained by the transmitting and receiving units 30A to 30H receiving in advance the received signals including the signal. That is, the teacher signals 42 shown in FIG. 2 are a plurality of reception signals obtained by the reception units 30A to 30H receiving in advance the reception signals including the reflection signal in the measurement period. Here, the measurement period is a period that is K times (K is 2 or more) of the predetermined period described above. The measurement period is, for example, 120 [s], but is not limited thereto. It may be 3 s, 10 s, or 30 s because it may be equal to or longer than the cycle of the human heart beat.

  The teacher signal 42 may be acquired in advance for each of the plurality of known second living bodies. In this case, the plurality of teacher signals 42 respectively corresponding to the plurality of known second living bodies may be stored in the memory 41 in a state of being associated with identification information identifying the corresponding second living body.

[Circuit 40]
The circuit 40 performs various processes to operate the identification device 10. The circuit 40 includes, for example, a processor that executes a control program, and a volatile storage area (main storage device) that is used as a work area used when executing the control program. This storage area is, for example, a RAM (Randdom Access Memory).

  The circuit 40 temporarily stores, in a storage area, the first reception signal acquired from each of the N reception units for a predetermined period. The circuit 40 may temporarily store the phase and amplitude of the first received signal in the storage area for a predetermined period. In the present embodiment, the circuit 40 temporarily stores the reception signals acquired from each of the transmission / reception units 30A to 30H in the storage area for a predetermined period.

  The circuit 40 may be configured by a dedicated circuit for performing various processes for operating the identification device 10. That is, the circuit 40 may be a circuit that performs software processing or a circuit that performs hardware processing. Also, the circuit 40 may have a non-volatile storage area.

  Subsequently, the functional configuration of the circuit 40 will be described.

  The circuit 40 includes, as shown in FIG. 3, a DC removing unit 401, a correlation coefficient calculating unit 402, an identification determining unit 403, and an identifying unit 404. The DC removing unit 401 is not essential.

<DC removing unit 401>
The DC removing unit 401 removes a DC (Direct Current) component of at least the first received signal of the first received signal and the second received signal by a predetermined method.

  More specifically, DC removing section 401 first uses transmission signals stored in memory area of circuit 40 and a teacher signal stored in memory 41 to transmit each propagation channel H (t). calculate.

Here, a propagation channel H obtained when a multiple-input and multiple-output (MIMO) array antenna configured of M _r reception antenna elements and M _t transmission antenna elements is arranged around the living body 50. (T) is represented by the following (Expression 1).

In Equation (1), h _ij indicates the complex channel response of the j-th transmitter to the i-th receiver, and t indicates the observation time.

  Next, the DC removing unit 401 removes a DC component, which is a noise component unnecessary for identification of the living body 50, from the propagation channel of the received signal and the teacher signal represented by the following (Expression 2) Calculate The DC removing unit 401 may store the calculated DC removal channel in the memory 41 or may store it in the storage area of the circuit 40.

Here, the DC removal channel H _{w / o DC} (t) of the received signal and the teacher signal is calculated from each component of the propagation channel as shown in (Equation 3) and (Equation 4) below. It is calculated by subtracting the DC component calculated by the measurement time average.

Here, N indicates the number of snapshots, F _s indicates the sampling frequency, and T indicates the measurement time.

  In addition, the removal method of DC component is not restricted to the method represented by the right side of (Formula 3). For example, the DC component may be removed by subtracting the propagation channel obtained in the unmanned predetermined range A1 where the living body 50 is not present.

<Correlation Coefficient Calculation Unit 402>
The correlation coefficient calculation unit 402 calculates a plurality of correlation coefficients by comparing the teacher signal 42 stored in the memory 41 with the plurality of received signals stored in the storage area of the circuit 40. More specifically, the correlation coefficient calculation unit 402 is divided into a plurality from the teacher signal and the M × N first reception signals obtained by each of the N reception units receiving the first reception signal. Calculate the correlation coefficient of

  Here, the plurality of correlation coefficients may be calculated by sliding correlation calculation. That is, correlation coefficient calculation unit 402 calculates a plurality of correlation coefficients between the teacher signal and each of M × N first received signals by sliding correlation calculation as the plurality of correlation coefficients. Good. The sliding correlation operation is an operation capable of finding a time relationship in which the correlation between the two signals is the highest by comparing the observed received signal with the teacher signal while sliding it.

  In addition, when the DC removal unit 401 calculates DC removal channels of the plurality of received signals and teacher signals and stores them in the storage area of the memory 41 or the circuit 40, the correlation coefficient calculation unit 402 generates the plurality of received signals and A plurality of correlation coefficients may be calculated using the DC removal channel of the teacher signal 42. Then, the plurality of correlation coefficients may be calculated by sliding correlation calculation. In other words, the correlation coefficient calculation unit 402 may calculate a plurality of correlation coefficients with each other by a sliding correlation operation using the teacher signal 42 and the DC removal channel of the plurality of received signals.

  Here, an example of a method of calculating a plurality of correlation coefficients will be described.

A measurement channel obtained for a predetermined range A1 including the first living body is defined as an identification channel H _T (t), where N _T is the number of snapshots using Equation (1). Also, assuming that the number of registrants is S and the number of snapshots is N _D , the database channel of the q-th registrant measured in advance using (Eq. 1) is defined as H _D (t, q). Note that H _D (t, q) corresponds to a measurement channel obtained for a predetermined range A1 including the q-th second biological body included in the teacher signal.

At this time, in order to shorten the measurement time for obtaining the identification channel, the relationship between the number of snapshots N _T and N _D is set to be the relationship shown in (Expression 5). And let the length of the sliding correlation time window be _NT .

In addition, regarding the identification channel and database channel in which the time windows are matched, those obtained by excluding the DC component using (Eq. 2) are H _{TW / o DC} (t) and H _{DW / o DC} (t, q) . Using these, the evaluation function ((p, q) using the sliding correlation is calculated by an operation for obtaining the correlation coefficient represented by (Expression 6) and (Expression 7). In equations (6) and (7), p indicates the number of loops for calculating the sliding correlation.

  The evaluation function ((p, q) using the sliding correlation is not limited to the case represented by the above (Equation 6) and (Equation 7), and may be represented by (Equation 8), for example. Further, the evaluation function ((p, q) using the sliding correlation may be expressed by (Expression 9) or (Expression 10) obtained by excluding the trial number r from (Expression 8). In Equation (9), the correlation is calculated using the expected value of the time correlation. In Equation (10), the correlation is calculated with the combination of antennas having the largest time correlation, that is, the combination with high correlation is selected from the combinations of MIMO, and the correlation is calculated.

<Identification determination unit 403>
The identification determination unit 403 performs biometric authentication of the first living body according to whether or not the calculated maximum value of the plurality of correlation coefficients exceeds a threshold. For example, the identification determination unit 403 performs biometric authentication of the first living body when the calculated maximum value of the plurality of correlation coefficients exceeds the threshold, and the maximum value of the plurality of correlation coefficients falls below the threshold. It is sufficient if biometric authentication of a living body is not performed.

In the present embodiment, the identification determination unit 403 compares the maximum value of the plurality of correlation coefficients calculated by the correlation coefficient calculation unit 402 with a threshold value of, for example, 0.6 input by a predetermined method. For example, when the maximum value of the correlation coefficient is equal to or larger than the threshold, the identification determination unit 403 identifies the first living body by the identification unit 404 as biometric authentication of the first living body. On the other hand, when the maximum value of the correlation coefficient is less than the threshold, the identification determination unit 403 determines that the first living body is not a corresponding person in the teacher signal, and ends the identification process without performing the biometric authentication of the first living body. Note that the identification determination unit 403 compares, for example, the maximum evaluation function _{max max} (p, q) extracted from the evaluation function ((p, q) shown in (Expression 6) with the threshold and determines whether the threshold is exceeded. The biometric authentication of the first living body is performed according to

<Identifier 404>
The identification unit 404 identifies that the first living body and the second living body are the same by a predetermined method when performing biometric authentication of the first living body. More specifically, the identification unit 404 identifies that the first living body and the second living body corresponding to the correlation coefficient having the maximum value are the same.

In the present embodiment, when it is determined by the identification determination unit 403 that the maximum value of the correlation coefficient is equal to or greater than the threshold value, the identification unit 404 provides training data to the living body 50 that has obtained the maximum value of the correlation coefficient. Identified as being identical to the known living body 50 included in That is, the identifying unit 404 classifies the registrant q (second living body) who has taken the extracted maximum evaluation function _{max max} (p, q) as the first living body that is the target of biometric authentication, It identifies that the registrant q and the first living body are identical.

  In this manner, the identification device 10 illustrated in FIG. 1 can identify the living body 50 by processing the reception signals received by the transmission / reception units 30A to 30H by the circuit 40.

[Operation of Identification Device 10]
Next, the operation of the identification device 10 configured as described above will be described. FIG. 4 is a flowchart showing an example of the operation of the identification device 10 according to the embodiment. FIG. 5 is a flowchart showing the detailed operation of step S14 shown in FIG. FIG. 6 is a flowchart showing the detailed operation of step S15 shown in FIG.

  First, the identification device 10 transmits M transmission signals and receives N reception signals (S11). More specifically, the identification device 10 transmits the first transmission signal in a predetermined range A1 including the first living body, using M transmission antenna elements. Then, in the identification device 10, each of the N reception units receives the first reception signal including the reflection signal in which the first transmission signal is reflected by the first living body using the reception antenna element for a predetermined period. In the present embodiment, the transmitting / receiving units 30A to 30H cause the antenna elements 31A to 31H to transmit transmission signals to the predetermined range A1 in a state where the first living body as the identification target living body 50 is disposed within the predetermined range A1. . Then, using the antenna elements 31A to 31H, the transmitting and receiving units 30A to 30H receive the first reception signal including the reflection signal in which the first transmission signal is reflected by the first living body for a predetermined period.

  Here, FIG. 7 is a view showing an environment used for the identification test by the identification device 10 according to the embodiment. FIG. 8 is a diagram showing an example of a propagation channel calculated from a received signal received in the environment shown in FIG.

  As shown in FIG. 7, in the present identification test, eight transceivers corresponding to the transceivers 30A to 30H are used. The eight transceivers are arranged in a circle with a radius of 0.5 m centering on the subject 50a and at an interval of 45 degrees. The subject 50a corresponds to the living body 50 to be identified in the identification test, that is, the first living body. In addition, a rectangular patch antenna of one element is used as a reception antenna element and a transmission antenna element corresponding to the antenna elements 31A to 31H. More specifically, eight receiving antenna elements included in eight transceivers are square patch antennas, respectively, and are installed at a height of 0.9 m from the floor surface. The eight transmitting antenna elements included in the eight transceivers are disposed directly above one microwave wavelength of the corresponding receiving antenna element.

As shown in FIG. 8, the components of the propagation channel h ₁₁ and component h ₈₈ is shows a periodic and large variations in comparison with the other components, it is understood that the same waveform. Component h ₁₁ is the channel response of receive antenna elements on the front of the subject 50a, component h ₈₈ is the channel response of receive antenna elements to the right forward as viewed from the subject 50a.

  The other component is the channel response of the receiving antenna element on the back or side of the subject 50a. That is, it can be seen that the back and side variations of the living body are small. This is considered to be because fluctuations due to biological activity occur in the chest and / or abdomen of the living body.

  Next, the identification device 10 removes DC components from the plurality of received signals acquired in step S11 and the teacher signal 42 stored in the memory 41 (S12). More specifically, first, the identification device 10 transmits the second transmission signal transmitted from the M transmitting antenna elements to the second living body which is the known living body 50 by the second living body. A teacher signal 42 which is M × N second received signals obtained by receiving in advance by N receiving units is read from the memory 41. Then, the identification device 10 removes the DC component from the first reception signal acquired in step S11 and the teacher signal read from the memory 41. In the present embodiment, the circuit 40 reads the teacher signal 42 from the memory 41, and calculates each DC removal channel using the teacher signal 42 and the reception signal acquired in step S11.

FIG. 9 is a diagram showing an example of the DC removal channel obtained by removing the DC component from the propagation channel shown in FIG. 9 shows, the propagation channel component _{h 11} as an _example, component _{h 88} and the component _{h 77} DC removal channel component _{h 11} to remove the DC component from _has been shown component _{h 88} and component _{h 77.} As shown in FIG. 8, since the DC component of the propagation channel differs depending on the position of the subject 50a, the position of the component waveform of the propagation channel in the vertical axis (i.e., intensity) direction is different. When the identification processing is performed using the components of the propagation channel in which the DC components are different as described above, the identification accuracy is degraded. On the other hand, in FIG. 9, the DC component of the propagation channel is removed, and the positions in the direction of the vertical axis (that is, the intensity) of the component waveform of the propagation channel are aligned. That is, when the identification processing is performed using the component of the propagation channel from which the DC component is removed, the identification accuracy is improved.

  Next, the identification device 10 calculates a plurality of correlation coefficients using the plurality of reception signals from which the DC component has been removed in step S12 and the teacher signal 42 (S13). More specifically, the identification device 10 receives M × N teacher signals from which DC components have been removed by a predetermined method, and M × N pieces of data received by each of the N reception units and from which DC components have been removed by a predetermined method. A plurality of correlation coefficients are calculated from the first received signal of In the present embodiment, the circuit 40 calculates a plurality of correlation coefficients from the respective DC removal channels calculated in step S12. In addition, since the detail of the calculation method of several correlation coefficient is as having demonstrated using (Formula 1)-(Formula 10), description is abbreviate | omitted.

  Next, the identification device 10 determines whether to perform biometric authentication of the first living body (S14). More specifically, the identification device 10 determines whether to perform biometric authentication of the first living body according to whether the maximum value of the plurality of correlation coefficients exceeds a threshold.

  More specifically, as shown in FIG. 5, first, the circuit 40 calculates the maximum value of the plurality of correlation coefficients calculated in step S13 (S141). Next, the circuit 40 compares the maximum value of the correlation coefficient with a threshold, such as 0.6, and determines whether the maximum value of the correlation coefficient is equal to or greater than the threshold (S142). In step S142, when the maximum value of the correlation coefficient is equal to or larger than the threshold (Yes in S142), the circuit 40 determines that the corresponding person is present (S143), and proceeds to step S15. On the other hand, when the maximum value of the correlation coefficient is smaller than the threshold in step S142 (No in S142), the circuit 40 determines that there is no applicable person (S144), and ends the operation of the identification device 10. When the identification device 10 determines that there is no applicable person, it determines that the living body 50 to be identified, that is, the first living body is not the known living body 50 included in the teacher signal, and returns a response that rejects biometric authentication. It is also good.

FIG. 10 is a diagram showing an example of a graph in which a plurality of maximum values of the correlation coefficient are described. FIG. 10 is an example of a diagram showing the maximum evaluation function _{max max} (p, q) of the evaluation function ((p, q) using the sliding correlation shown in (Expression 6), for example. In FIG. 10, the sliding correlation between the plurality of second living bodies included in the teacher data and the first living body which is the living body 50 to be identified is shown. In FIG. 10, the correlation coefficient indicated by a solid line with the highest peak indicates that there is a second living body coincident with the first living body. The correlation coefficient indicated by the broken line with the second highest peak indicates that there is a second living body that shows others with characteristics similar to the first living body. The correlation coefficient having the third and subsequent peaks indicates that there is a second living body indicating another person having a feature different from the first living body.

  FIG. 11 is a diagram in which FAR and FRR are plotted when the threshold value in the embodiment is changed. FIG. 11 shows a false acceptance rate (FAR) and a false rejection rate (FRR: False Rejection Rate) when biometric authentication is performed using the plurality of correlation coefficients calculated by the identification device 10 and the changed threshold value. ing. As shown in FIG. 11, it can be seen that the false rejection rate (FRR) rises at the same time as the false acceptance rate (FAR) decreases as the threshold value increases. That is, as shown in FIG. 11, when the threshold value is increased to 0.7 instead of 0.6, the false acceptance rate (FAR) is further decreased, but the false rejection rate (FRR) is also increased. Although the threshold is described as 0.6 in the present embodiment, the threshold may be appropriately changed in accordance with the requirements of the application destination.

  Next, the identification device 10 identifies whether the first living body is identical to the second living body included in the teacher data (S15). More specifically, when performing biometric authentication of the first living body, the identification device 10 identifies that the first living body and the second living body are the same by a predetermined method.

  More specifically, as shown in FIG. 6, first, the second living body used to identify whether the circuit 40 is the same as the first living body is the phase of the second living body included in the teacher data. It is determined whether it is the second living body corresponding to the maximum value of the relation number (S151). In step S151, when the circuit 40 determines that the second living body is the second living body corresponding to the maximum value of the correlation coefficient (Yes in S151), the second living body performs biometric authentication. It identifies that it is the same as the first living body to be identified (S152), and ends the biometric authentication of the first living body. On the other hand, when the circuit 40 determines in step S151 that the second living body is not the second living body corresponding to the maximum value of the correlation coefficient (No in S151), biometric authentication is performed with the second living body. It discriminate | determines that it is different from the 1st biological body which is identification object for (S153), and returns to step S151.

[Effects, etc.]
In the environment used for the recognition test shown in FIG. 7, the identification device 10 transmits transmission waves from each of, for example, eight antenna elements installed around the living body 50, and receives a reception signal. Then, the identification device 10 performs a sliding correlation operation on a plurality of temporal correlations between the teacher signal stored in the memory 41 and the received signal from the subject 50a that is the living body 50 that is the object of biometrics authentication. Calculated by Here, when the subject 50a matches the known living body 50 included in the teacher signal, that is, when the known living body 50 and the subject 50a are the same person, the maximum value of the correlation coefficient of the sliding correlation becomes large. On the other hand, in the case where the subject 50a matches the known living body 50 included in the teacher signal, that is, when the known living body 50 and the subject 50a are different people, the maximum value of the sliding correlation correlation coefficient decreases. Thereby, the identification device 10 can determine whether the subject 50a is in the known living body 50 included in the teacher signal, using the maximum value of the correlation coefficient calculated by the sliding correlation operation.

  In addition, it turned out that this tendency becomes so remarkable that there are many antenna elements to install, and, thereby, can contribute more to improvement of equivalent error rate (EER).

  Also, DC bias is applied to the received signal acquired by each antenna element of the identification device 10, and this DC bias is easily affected by individual differences of the identification device 10 and subtle differences in the position of the living body 50, and the identification rate Affect. Therefore, the identification device 10 according to the present embodiment calculates a plurality of correlation coefficients using the received signal from which the DC component has been removed. This can improve the identification rate.

  As described above, according to the identification device 10 according to the present embodiment, a plurality of correlation coefficients are obtained from the first received signal and the teacher signal which are measurement signals obtained from the receiving antenna element installed around the first living body. Can be calculated. And performing biometric authentication by identifying that the first living body and the second living body included in the teacher data are the same according to whether the maximum value among the plurality of correlation coefficients exceeds the threshold value. it can. As a result, it is possible to suppress an error of accepting another person as the principal when the first living body is not included in the teacher data, so that the equivalent error rate (EER) can be reduced.

  In the example illustrated in FIG. 1, the identification device 10 performs biometric identification using the reception signals received by the N transmission / reception units 30A to 30H arranged around the predetermined range A1. Whether or not the maximum value of the correlation coefficient calculated before performing biometric identification exceeds the threshold value is compared, and the maximum value of the correlation coefficient is less than the threshold value, it is determined that there is no applicable person. As a result, since the living body 50 that is the object of biometric authentication, that is, the first living body does not exist as the known living body 50 that is included in the teacher data as the second living body, no equivalent person can be found. Can be made smaller.

  In addition, in the identification device 10 according to the present embodiment, the correlation coefficient is calculated after DC components of the first received signal and the second received signal are removed by a predetermined method. As a result, it is possible to suppress the DC component, which is a noise component unnecessary for the living body identification, from the received signal, so that the living body identification can be efficiently performed in a short time.

  Further, in the identification device 10 according to the present embodiment, a plurality of correlation coefficients may be calculated using a sliding correlation operation. According to this, it is possible to determine whether biometric authentication is to be performed using the maximum value of the time correlation coefficient of the sliding correlation. As a result, it is possible to suppress an error of accepting another person as the principal when the first living body is not included in the teacher data, so that the equivalent error rate (EER) can be reduced.

  In addition, the identification device 10 according to the present embodiment can identify the living body 50 such as a human using a wireless signal such as a microwave. That is, the identification device 10 according to the present embodiment can identify the living body 50 such as a human without performing image analysis on an image captured by a camera or the like. Therefore, human identification can be performed while protecting human privacy.

  The present disclosure can be used for an identification device and an identification method for identifying a living body using a wireless signal, and in particular, an identification device mounted on a home appliance that performs control according to the living body, a monitoring device that detects intrusion of a living body, and the like. And can be used for identification methods.

DESCRIPTION OF REFERENCE NUMERALS 10 identification device 30A to 30H transmission / reception unit 31A to 31H antenna element 40 circuit 41 memory 42 teacher signal 50 living body 50a subject 401 DC removal unit 402 correlation coefficient calculation unit 403 identification determination unit 404 identification unit

Claims (7)

M (M is an integer of 1 or more) transmission antenna elements for transmitting the first transmission signal in a predetermined range including the first living body,
N (N is an integer of 3 or more) receiving units each having a receiving antenna element and disposed around the periphery of the predetermined range, wherein the first transmission signal is reflected by the first living body N receiving units each receiving a first received signal including a reflected signal for a predetermined period of time using the receiving antenna element;
Causing the N reception units to receive in advance a second reception signal including a reflection signal in which a second transmission signal transmitted from the M transmission antenna elements to the second living body is reflected by the second living body A memory storing a teacher signal which is the M × N second received signals obtained by
A plurality of correlation coefficients are calculated from the teacher signal and the M × N first received signals obtained by each of the N receiving units receiving the first received signals,
Performing biometric authentication of the first living body according to whether or not the calculated maximum value of the plurality of correlation coefficients exceeds a threshold value,
When performing biometric authentication of the first living body, the circuit includes a circuit that identifies the first living body and the second living body as being identical by a predetermined method.
Identification device. The circuit is
The biometric authentication of the first living body is performed when the calculated maximum value of the plurality of correlation coefficients exceeds a threshold value, and the maximum value of the plurality of correlation coefficients falls below the threshold value. Do not do biometrics,
The identification device according to claim 1. The circuit is
Identifying that the first living body and the second living body corresponding to the correlation coefficient having the maximum value are identical;
The identification device according to claim 1. The circuit is
At least the first received signal of the first received signal and the second received signal has a DC (Direct Current) component removed by a predetermined method.
The identification device according to any one of claims 1 to 3. The circuit is
As the plurality of correlation coefficients, a plurality of correlation coefficients between the teacher signal and each of the M × N first received signals are calculated by sliding correlation operation.
The identification apparatus of any one of Claims 1-4. The teacher signal is a period of K times (K is 2 or more) of the predetermined period, and the M × N second signals obtained by the N reception units receiving the second reception signal in advance. It is a received signal,
The identification device according to any one of claims 1 to 5. N (N is an integer of 3 or more) receiving units that have M (M is an integer of 1 or more) transmitting antenna elements and a receiving antenna element and are arranged around a predetermined range, and a memory A method of identifying an identification device comprising:
Transmitting the first transmission signal to a predetermined range including the first living body using the M transmission antenna elements;
Each of the N reception units receives a first reception signal including a reflection signal in which the first transmission signal is reflected by the first living body by using the reception antenna element, for a predetermined period,
A second transmission signal transmitted from the M transmission antenna elements to the second living body is a reflection signal that is reflected by the second living body, and M × obtained by the N reception units receiving in advance Reading a teacher signal which is N second received signals from the memory;
A plurality of correlation coefficients are calculated from the read teacher signal and the M × N first received signals received by each of the N receiving units,
Performing biometric authentication of the first living body according to whether or not the calculated maximum value of the plurality of correlation coefficients exceeds a threshold value,
When performing biometric authentication of the first living body, the first living body and the second living body are identified as the same by a predetermined method.
Identification method.

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