JP2020020696A - Arrival direction estimating device and arrival direction estimating method - Google Patents

Abstract

To provide an arrival direction estimation technology which can improve the accuracy of estimating the angle of a target without causing a phase fold-back.SOLUTION: An arrival direction estimating device comprises first to third calculation units and an estimation unit. The first and second calculation units calculate a first phase shift matrix from receive signals obtained by first and third sub-arrays which are a combination of a plurality of receive antennas and receive signals obtained by second and fourth sub-arrays of the same shape as that of the first and third sub-arrays, which cause first and second phase differences between the first and third sub-arrays and these sub-arrays. The third sub-array is of the same shape as the first sub-array. The second phase difference differs from the first phase difference. The third calculation unit calculates the eigen vector of a linear coupling matrix in which the first and second phase shift matrices are linearly coupled. The estimation unit estimates the arrival direction of a radio wave from a combination of eigen values of the first and second phase shift matrices in the same eigen vector.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for estimating a direction of arrival of a radio wave.

  The radar device irradiates radio waves and receives the radio waves (reflected waves) reflected from the target, thereby estimating the arrival direction of the reflected waves. The method of estimating the direction of arrival is a method of calculating the direction of arrival (angle) from information on the phase difference and amplitude difference of the received signals obtained by a plurality of receiving antennas that receive the reflected waves.

JP 2012-103132 A

  When calculating an angle from a phase difference between sub-arrays, such as the ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) method or the DoA-matrix method, there is a trade-off between angle accuracy and phase folding. Specifically, the larger the amount of movement between the sub-arrays, the better the angular accuracy of the target, but if it is less than half the wavelength of the arriving radio wave, phase wrapping does not occur, and conversely, the amount of movement between the sub-arrays If it is larger than the half wavelength of the radio wave, phase wrapping occurs.

  Therefore, for example, the arrival direction estimating technique disclosed in Patent Document 1 cannot make the angle of the target highly accurate without causing phase wrapping.

  The present invention has been made in view of the above circumstances, and has as its object to provide a direction-of-arrival estimation technique that can improve the angular accuracy of a target without causing phase wrapping.

  The direction of arrival estimation apparatus according to the present invention is configured such that a reception signal obtained by a first sub-array, which is a combination of a plurality of reception antennas, has the same shape as that of the first sub-array and is between the first sub-array and the first sub-array. A first calculating unit for calculating a first phase shift matrix from a received signal obtained in a second sub-array in which a first phase difference occurs, and a third sub-array having the same shape as the first sub-array And a fourth sub-array having the same shape as the third sub-array and having a second phase difference different from the first phase difference between the received signal and the third sub-array. A second calculating unit that generates a second phase shift matrix from the received signal, and a second calculating unit that calculates an eigenvector of a linear combination matrix obtained by linearly combining the first phase shift matrix and the second phase shift matrix. Calculation unit of 3 An estimator for estimating the arrival direction of a radio wave from a combination of the eigenvalue of the first phase shift matrix and the eigenvalue of the second phase shift matrix in the same eigenvector (first configuration) It is.

  In the direction-of-arrival estimation apparatus having the first configuration, even if both the coefficient of the first phase shift matrix and the coefficient of the second phase shift matrix in the linear combination are not zero (second configuration), Good.

  In the direction-of-arrival estimating device having the second configuration, at least one of a coefficient of the first phase shift matrix and a coefficient of the second phase shift matrix in the linear combination is variable (third configuration). You may.

  In the direction-of-arrival estimation apparatus according to any one of the first to third configurations, the first sub-array and the third sub-array may be the same sub-array (fourth configuration).

  In the direction-of-arrival estimation apparatus according to any one of the first to third configurations, the first sub-array and the third sub-array may be different sub-arrays (fifth configuration).

  The method of estimating the direction of arrival according to the present invention is characterized in that a reception signal obtained in a first sub-array, which is a combination of a plurality of reception antennas, is between the first sub-array and the same shape as the first sub-array. A first calculating step of calculating a first phase shift matrix from a received signal obtained by a second sub-array in which a first phase difference occurs, and a third sub-array having the same shape as the first sub-array And a fourth sub-array having the same shape as the third sub-array and having a second phase difference different from the first phase difference between the received signal and the third sub-array. A second calculating step of generating a second phase shift matrix from the received signal, and calculating an eigenvector of a linear combination matrix obtained by linearly combining the first phase shift matrix and the second phase shift matrix. Calculation of 3 And a step of estimating a direction of arrival of a radio wave from a combination of an eigenvalue of the first phase shift matrix and an eigenvalue of the second phase shift matrix in the same eigenvector (sixth embodiment). Configuration).

  ADVANTAGE OF THE INVENTION According to the direction-of-arrival estimation technique which concerns on this invention, the angle precision of a target can be improved, without generating phase return.

Diagram showing a configuration example of a radar device Flow chart showing the flow of first to third calculation processing and estimation processing The figure which shows the angle candidate of the 1st target The figure which shows the example of arrangement of a receiving antenna

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

<1. Configuration of radar device>
FIG. 1 is a diagram illustrating a configuration of a radar device 1 according to the present embodiment. The radar device 1 is mounted on a vehicle such as an automobile, for example. When the radar device 1 is mounted at the front end of the host vehicle, the radar device 1 acquires target data related to a target existing in front of the host vehicle by using a transmission wave. The target data includes a distance to the target, a relative speed of the target with respect to the radar device 1, and the like. However, in order to describe the radar device 1 according to the present embodiment as an example of the DOA estimating device, in the following description, only the portion related to DOA estimation will be described.

  As shown in FIG. 1, the radar device 1 mainly includes a transmission unit 2, a reception unit 3, and a signal processing device 4.

  The transmission unit 2 includes a signal generation unit 21 and a transmitter 22. The transmitter 22 modulates the signal generated by the signal generator 21 to generate a transmission signal. The transmission antenna 23 converts a transmission signal into a transmission wave TW and outputs the same.

  The receiving unit 3 includes a plurality of receiving antennas 31 and a plurality of individual receiving units 32 connected to the plurality of receiving antennas 31. In the present embodiment, the receiving unit 3 includes, for example, four receiving antennas 31 and four individual receiving units 32. The four receiving antennas 31 correspond to the receiving channels ch1 to ch4, respectively. The four receiving antennas 31 are arranged along the left-right direction of the vehicle, and the distance between adjacent antennas is a predetermined distance d. Note that the three predetermined distances d do not have to be strictly the same, as long as the three predetermined distances d can be regarded as the same in consideration of design errors and variations. The predetermined distance d is preferably equal to or less than a half wavelength of the received signal obtained by the receiving antenna 31 so that the amount of movement between the sub-arrays in which phase aliasing does not occur can be secured. However, even when the phase wrapping occurs, it is possible to prevent the phase wrapping from occurring in the FOV depending on the setting of the FOV of the radar apparatus 1. Therefore, the predetermined distance d is a half of the reception signal obtained by the reception antenna 31. It may be larger than the wavelength. In this embodiment, the predetermined distance d is set to be equal to or less than a half wavelength of the reception signal obtained by the reception antenna 31. The four individual receiving units 32 correspond to the four receiving antennas 31, respectively. Each receiving antenna 31 receives a reflected wave RW from an object to obtain a received signal, and each individual receiving unit 32 processes the received signal obtained by the corresponding receiving antenna 31.

  Each individual receiving section 32 includes a mixer 33 and an A / D converter 34. The reception signal obtained by the reception antenna 31 is sent to the mixer 33 after being amplified by a low noise amplifier (not shown). The transmission signal from the transmitter 22 of the transmission unit 2 is input to the mixer 33, and the transmission signal and the reception signal are mixed in the mixer 33. Thereby, a beat signal having a beat frequency that is a difference between the frequency of the transmission signal and the frequency of the reception signal is generated. The beat signal generated by the mixer 33 is converted to a digital signal by the A / D converter 34 and then output to the signal processing device 4.

  The signal processing device 4 includes a microcomputer including a CPU (Central Processing Unit), a memory 41, and the like. The signal processing device 4 stores various data to be operated on in a memory 41 which is a storage device. The memory 41 is, for example, a RAM (Random Access Memory). The signal processing device 4 includes a transmission control unit 42, a Fourier transform unit 43, and a data processing unit 44 as functions implemented by software using a microcomputer. The transmission control unit 42 controls the signal generation unit 21 of the transmission unit 2. The data processing unit 44 includes a peak extracting unit 45, first to third calculating units 46 to 48, and an estimating unit 49.

  Since the Fourier transform unit 43 receives the reflected waves from the plurality of targets in the receiving antenna 31 in an overlapping state, the frequency component based on the reflected waves of each target is calculated from the beat signal generated based on the received signal. (For example, FFT (Fast Fourier Transfer) processing). In the FFT processing, a reception level and phase information are calculated for each frequency point (may be referred to as a frequency bin) set at a predetermined frequency interval.

  The peak extracting unit 45 detects a peak from the result of the FFT processing or the like by the Fourier transform unit 43.

The first calculation unit 46 is a combination of the reception signal obtained by the first sub-array, which is a combination of the reception antenna 31 of 1ch and the reception antenna 31 of 2ch, and the reception antenna 31 of 2ch and the reception antenna 31 of 3ch. A first phase shift matrix _Rα is calculated from the received signals obtained in the second sub-array. The second sub-array, the first phase difference [Phi _alpha is generated between the first sub-array have the same shape as the first sub-array.

The second calculation unit 47 is a combination of the reception signal obtained by the third sub-array, which is a combination of the reception antenna 31 of 1ch and the reception antenna 31 of 2ch, and the reception antenna 31 of 3ch and the reception antenna 31 of 4ch. A second phase shift matrix _Rβ is generated from the received signal obtained in the fourth sub-array. In this embodiment, the first sub-array and the third sub-array are the same sub-array. The fourth sub-array has the same shape as the third sub-array, and a second phase difference Φ _β different from the first phase difference Φ _α is generated between the fourth sub-array and the third sub-array.

Third calculating section 48 calculates the eigenvectors of the linear coupling matrix R _gamma and the first phase shift matrix R _alpha and the second phase shift matrix R _beta linear combination _{(= pR α + qR β)} . Note that p and q are real numbers, respectively, and at least one of p and q is not zero.

Estimation unit 49, a combination of a first phase shift matrix R _alpha eigenvalues and second eigenvalue of the phase shift matrix R _beta in the same eigenvector estimates the arrival direction of radio waves. The estimation unit 49 outputs the azimuth (angle) at which the estimated target exists to the memory 41, the vehicle control ECU 5, and the like.

<2. Details of calculation processing and estimation processing>
FIG. 2 is a flowchart illustrating a flow of the first to third calculation processes executed by the first to third calculation units 46 to 48 and an estimation process executed by the estimation unit 49.

The first calculator 46 performs a calculation using the input vector x ₁ (t) of the first sub-array and the input vector x ₂ (t) of the _second sub-array. Each of the input vector x ₁ (t) and the input vector x ₂ (t) is a two-dimensional column vector. The first row element of the input vector x ₁ (t) is a peak value extracted by the peak extracting unit 45 corresponding to the received signal obtained by the receiving antenna 31 of 1ch. The element in the second row of the input vector x ₁ (t) is a peak value extracted by the peak extraction unit 45 corresponding to the reception signal obtained by the reception antenna 31 of 2ch. The first row element of the input vector x ₂ (t) is a peak value extracted by the peak extraction unit 45 corresponding to the reception signal obtained by the reception antenna 31 of 2ch. The element in the second row of the input vector x ₂ (t) is a peak value extracted by the peak extraction unit 45 corresponding to the reception signal obtained by the reception antenna 31 of 3ch.

First calculating section 46 first calculates an autocorrelation matrix _{R 11} in the first sub-array (step S1). Autocorrelation matrix R ₁₁ can be calculated by the following equation (1). Here, E [•] represents a time averaging process, and [•] ^H represents a complex conjugate transpose.
R ₁₁ = E [x ₁ (t) x ₁ ^H (t)] (1)

First calculating section 46 then calculates the cross-correlation matrix R ₂₁ between the first sub-array and a second sub-arrays (step S2). Cross-correlation matrix R ₂₁ can be calculated by the following equation (2).
R ₂₁ = E [x ₂ (t) x ₁ ^H (t)] (2)

The first calculating unit 46 calculates a first phase shift matrix R _alpha (step S3). The first phase shift matrix _Rα can be calculated by the following equation (3). Here, [·] ⁻¹ represents an inverse matrix.
R _α = R ₂₁ [R ₁₁ ] ⁻¹ (3)

The second calculation unit 47 performs calculation using the input vector x ₃ (t) of the _third sub-array and the input vector x ₄ (t) of the _fourth sub-array. Each of the input vector x ₃ (t) and the input vector x ₄ (t) is a two-dimensional column vector. The first row element of the input vector x ₃ (t) is a peak value extracted by the peak extracting unit 45 corresponding to the received signal obtained by the receiving antenna 31 of 1ch. The element in the second row of the input vector x ₃ (t) is a peak value extracted by the peak extraction unit 45 corresponding to the reception signal obtained by the reception antenna 31 of 2ch. The first row element of the input vector x ₄ (t) is a peak value extracted by the peak extracting unit 45 corresponding to the received signal obtained by the receiving antenna 31 of 3ch. The element of the second row of the input vector x ₄ (t) is a peak value extracted by the peak extracting unit 45 corresponding to the received signal obtained by the receiving antenna 31 of 4 ch.

In step S4 following the step S3, the second calculating unit 47 calculates an autocorrelation matrix _{R 33} in the third sub-array. Autocorrelation matrix R ₃₃ can be calculated by the following formula (4).
R ₃₃ = E [x ₃ (t) x ₃ ^H (t)] (4)

Second calculating unit 47 then calculates the cross-correlation matrix R ₄₃ between the third sub-array and a fourth sub-array (step S5). Cross-correlation matrix R ₄₃ can be calculated by (5) below.
R ₄₃ = E [x ₄ (t) x ₃ ^H (t)] (5)

The second calculation unit 47 calculates a second phase shift matrix R _beta (step S6). The second phase shift matrix _Rβ can be calculated by the following equation (6).
R _β = R ₄₃ [R ₃₃ ] ⁻¹ (6)

  In the flowchart of FIG. 2, the processing of steps S4 to S6 is performed after the processing of steps S1 to S3 is completed. However, the processing of steps S1 to S3 and the processing of steps S4 to S6 are performed in parallel. Is also good. Further, in the present embodiment, since the first sub-array and the third sub-array are the same sub-array, the processing of step S4 may be omitted, and the second calculating unit 47 may use the processing result of step S1. .

After the processing of steps S1 to S6 is completed, the third calculating unit 48 calculates a linear combination matrix _Rγ (step S7). The linear combination matrix _Rγ can be calculated by the following equation (7). Note that p and q are real numbers, respectively, and at least one of p and q is not zero.
R _γ = pR _α + qR _αβ (7)

And a third calculation unit 48 performs eigenvalue decomposition of the linear combination matrix R _gamma, calculates the eigenvectors of the linear coupling matrix R _gamma (step S8). That is, the third calculation unit 48 performs eigenvalue decomposition of the linear combination matrix R _gamma, calculates the eigenvectors A satisfying the following equation (8). Incidentally, the [Phi _gamma is a unique value of the linear combination matrix R _gamma. Since the linear combination matrix _Rγ is a matrix having two rows and two columns, two eigenvectors A are obtained. Therefore, in the following description, one eigenvector A is described as an eigenvector A1, and the other eigenvector A is described as an eigenvector A2.
R _γ A = AΦ _γ (8)

In step S9 following the step S8, the estimation unit 49 calculates a first phase shift matrix one of the eigenvalues of R _alpha [Phi _{[alpha] 1} and a second one of the eigenvalues [Phi _.beta.1 phase shift matrix R _beta using eigenvectors A1 to calculate a first of the other eigenvalues [Phi _.beta.2 of the other eigenvalues [Phi _{[alpha] 2} and the second phase shift matrix R _beta phase shift matrix R _alpha using eigenvectors A2. Each eigenvalue can be calculated by the following equations (9) to (12).
R _α A1 = A1Φ _α1 (9)
R _β A1 = A1Φ _β1 (10)
R _α A2 = A2Φ _α2 (11)
R _β A2 = A2Φ _β2 (12)

Estimation unit 49 converts the eigenvalues [Phi _{[alpha] 1} in the angle theta _{[alpha] 1} of the first target object, converts the eigenvalues [Phi _.beta.1 angle theta _.beta.1 of the first target object. Accuracy of the angle theta _{[alpha] 1} is bad angle theta _{[alpha] 1} in the phase wrapping is not generated, better accuracy of angle theta _.beta.1 the angle theta _.beta.1 in phase folding is occurring. Therefore, the estimating unit 49 estimates the angle closest to the angle θ _α1 among the phase turning angles of the angle θ _β1 and the angle θ _{β1 as} the angle of the first target (Step S10). For example, when the angle θ _α1 and the phase turning angles θ _β1 ′ and θ _β1 ″ of the angle θ _β1 and the angle θ _{β1 have} the relationship illustrated in FIG. 3, the estimation unit 49 sets the angle θ _β1 ′ to the first The angle is estimated as the angle of the first target, whereby the angle accuracy of the first target can be improved without causing phase wrapping.

Incidentally, if the absolute value of the eigenvalues [Phi _{[alpha] 1} is less than the predetermined value, the estimation unit 49 determines that there is no first target object, it is preferable not to perform angle estimation of the first target object. Accordingly, it is possible to prevent the estimation unit 49 from performing the angle estimation of the ghost target. Absolute value may be used for the average of the absolute value or eigenvalue [Phi _{[alpha] 1} and eigenvalues [Phi _.beta.1 eigenvalues [Phi _.beta.1 instead of the absolute values of the eigenvalues [Phi _{[alpha] 1.}

Estimation unit 49 converts the eigenvalues [Phi _{[alpha] 2} of the angle theta _{[alpha] 2} of the second target object, converts the eigenvalues [Phi _.beta.2 angle theta _.beta.2 of the second target object. Accuracy of angle _θ α2 is bad angle _θ α2 in the phase aliasing is not generated, the accuracy of the angle _θ β2 is good angle _θ β2 in the phase wrapping has occurred. Therefore, the estimating unit 49 estimates the angle closest to the angle θ _α2 among the phase turning angles of the angle θ _β2 and the angle θ _{β2 as} the angle of the second target (step S11). This makes it possible to improve the angular accuracy of the second target without generating a phase turn.

Incidentally, if the absolute value of the eigenvalues [Phi _{[alpha] 2} is less than the predetermined value, the estimation unit 49 determines that there is no second target object, it is preferable not to perform angle estimation of the second target object. Accordingly, it is possible to prevent the estimation unit 49 from performing the angle estimation of the ghost target. Absolute value may be used for the average of the absolute value or eigenvalue [Phi _{[alpha] 2} and eigenvalues [Phi _.beta.2 eigenvalues [Phi _.beta.2 instead of the absolute values of the eigenvalues [Phi _{[alpha] 2.}

  In the flowchart of FIG. 2, the process of step S11 is performed after the process of step S10 ends, but the process of step S10 and the process of step S11 may be performed in parallel.

According to the first to third calculation process and estimation process described above, the linear combination matrix R _gamma only eigenvalue decomposition, i.e. can be improved angular accuracy of the target without causing phase folding in eigenvalue decomposition only once. Therefore, the angle accuracy of the target can be improved with a small amount of calculation and without causing phase aliasing.

In the above equation (7), it is preferable that both p and q are not zero. In an ideal received signal, the "first phase shift matrix R _alpha only determined eigenvectors" and "second phase shift matrix R _beta only eigenvector" match. However, in the actual received signal, for errors and noise of each receiving antenna 31 is slightly different, the "first phase shift matrix R _alpha only determined eigenvectors" and "second phase shift matrix R _beta only eigenvector Does not match.

Therefore, without the p and q are both zero and, better to use the "first phase shift matrix R _alpha and a second eigenvector obtained by the phase shift matrix R _beta" is "only the first phase shift matrix R _alpha in the obtained eigenvectors "or than using" second phase shift matrix R _beta eigenvectors only "increases the angular accuracy of the target. Than the difference between the "first phase shift matrix R _alpha only determined eigenvectors" and "second eigenvector only the phase shift matrix R _beta", "first phase shift matrix R _alpha only determined eigenvectors" and it is less of a difference between the "first phase shift matrix R _alpha and a second eigenvector obtained by the phase shift matrix R _beta" Similarly, the "first phase shift matrix R _alpha only determined eigenvectors" and than the difference between the "second eigenvector only the phase shift matrix R _beta", the "second eigenvector only the phase shift matrix R _beta," "the first phase shift matrix R _alpha and the second phase shift matrix This is because more of the difference between the eigenvectors "obtained in _R β is small.

  The value of p and the value of q at which the angular accuracy of the target is maximized change according to the error of each receiving antenna 31 and the situation of noise. Although it is not realistic to always set p and q to optimal values, the third calculation unit 48 may be set according to, for example, the type of vehicle on which the radar device 1 is mounted, the surrounding environment of the vehicle on which the radar device 1 is mounted, and the like. Preferably vary p and q. For example, the third calculator 48 sets p and q to standard values (for example, 1), and sets the radar device 1 to a vehicle type on which the radar device 1 is mounted, a surrounding environment of the vehicle on which the radar device 1 is mounted, and the like. The third calculation unit 48 may obtain information on the related information and change p and q as necessary based on the obtained information.

<3. Others>
Various technical features disclosed in the present specification can be modified in various ways in addition to the above-described embodiment without departing from the spirit of the technical creation. In addition, a plurality of embodiments and modifications shown in this specification may be implemented in combination within a possible range.

  In the above-described embodiment, each sub-array is configured by a combination of two reception antennas, but each sub-array may be configured by a combination of three or more reception antennas. By increasing the number of receiving antennas forming the sub-array, the number of target angles that can be calculated can be increased. Note that each sub-array may have the same shape, and the shape (the arrangement of the receiving antennas in the sub-array) is not limited.

  In the above-described embodiment, a configuration is adopted in which the first sub-array and the third sub-array are the same sub-array. Thus, the space occupied by the receiving antenna group including the first to fourth sub-arrays can be reduced, and the radar apparatus 1 can be downsized.

  However, there may be a case where the receiving antenna groups including the first to fourth sub-arrays cannot be integrated into one place due to, for example, restrictions on the shape of the radar device 1. In such a case, a configuration may be adopted in which the first sub-array and the third sub-array are different from each other. That is, by adopting a configuration in which the first sub-array and the third sub-array are different sub-arrays, the degree of freedom regarding the shape of the radar device 1 can be increased. As an example of a configuration in which the first sub-array and the third sub-array are different from each other, the arrangement of the receiving antenna shown in FIG. 4 can be mentioned.

  In the above-described embodiment, the in-vehicle radar device has been described. However, the present invention is also applicable to an infrastructure radar device, an aircraft surveillance radar device, and the like installed on a road or the like.

REFERENCE SIGNS LIST 1 radar device 2 transmission unit 3 reception unit 31 reception antenna 4 signal processing device 46 to 48 first to third calculation unit 49 estimation unit

Claims (6)

A second sub-array having the same shape as the first sub-array and having a first phase difference between the reception signal obtained by the first sub-array, which is a combination of a plurality of reception antennas, and the first sub-array; A first calculator for calculating a first phase shift matrix from the received signals obtained in the sub-array;
A received signal obtained in a third sub-array having the same shape as the first sub-array, and having the same shape as the third sub-array and different from the first phase difference between the third sub-array and the third sub-array A second calculator configured to generate a second phase shift matrix from a received signal obtained by the fourth sub-array in which the second phase difference occurs;
A third calculation unit that calculates an eigenvector of a linear combination matrix obtained by linearly combining the first phase shift matrix and the second phase shift matrix;
An estimating unit that estimates a direction of arrival of a radio wave from a combination of an eigenvalue of the first phase shift matrix and an eigenvalue of the second phase shift matrix in the same eigenvector;
An arrival direction estimation device comprising:   The direction-of-arrival estimation apparatus according to claim 1, wherein the coefficient of the first phase shift matrix and the coefficient of the second phase shift matrix in the linear combination are not zero.   The direction-of-arrival estimation apparatus according to claim 2, wherein at least one of a coefficient of the first phase shift matrix and a coefficient of the second phase shift matrix in the linear combination is variable.   The direction-of-arrival estimation apparatus according to any one of claims 1 to 3, wherein the first sub-array and the third sub-array are the same sub-array.   The direction-of-arrival estimation apparatus according to any one of claims 1 to 3, wherein the first sub-array and the third sub-array are different sub-arrays. A second sub-array having the same shape as the first sub-array and having a first phase difference between the reception signal obtained by the first sub-array, which is a combination of a plurality of reception antennas, and the first sub-array; A first calculating step of calculating a first phase shift matrix from the received signals obtained in the sub-array;
A received signal obtained in a third sub-array having the same shape as the first sub-array, and having the same shape as the third sub-array and different from the first phase difference between the third sub-array and the third sub-array A second calculation step of generating a second phase shift matrix from a received signal obtained in a fourth sub-array in which a second phase difference occurs;
A third calculation step of calculating an eigenvector of a linear combination matrix obtained by linearly combining the first phase shift matrix and the second phase shift matrix;
An estimating step of estimating a direction of arrival of a radio wave from a combination of an eigenvalue of the first phase shift matrix and an eigenvalue of the second phase shift matrix in the same eigenvector;
Comprising,
Direction of arrival estimation method.

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