Apparatus for estimating direction of arrival and method for estimating direction of arrival

Abstract

The present invention achieves an arrival direction estimation device and an arrival direction estimation method with which it is possible to appropriately estimate the arrival direction of a radio wave by means of a simple configuration or processing. This arrival direction estimation device comprises: an array antenna (11) which includes a plurality of antenna elements (A(m)) and in which the respective phase centers of the plurality of antenna elements (A(m)) are arranged in one direction; a target estimation unit (12) that estimates the arrival direction of a radio wave on the basis of a reception signal for each of the antenna elements (A(m)); an electric power estimation unit (14) that estimates the electric power in the arrival direction for each of a plurality of sub-array antennas each containing the same number of antenna elements; and a target determination unit (15) that determines the arrival direction to be an arrival direction estimation target if the amount of variation in the electric power in the arrival direction estimated for each of the sub-array antennas is less than or equal to a predetermined value.

Description

Technical Field

[0001] The present invention relates to an arrival direction estimation device and an arrival direction estimation method.

Background Art

[0002] In a communication device or a radar (RADAR: RAdio Detection And Ranging), a method of estimating the arrival direction of radio waves using an array antenna in which a plurality of antennas are arrayed is common. In such an arrival direction estimation method using an array antenna, there is a case where a direction different from the actual arrival direction of radio waves is estimated as the arrival direction of radio waves. In Patent Document 1, a plurality of antennas capable of receiving two orthogonal polarization waves are sub-arrayed, and at least one of phase shift and amplitude adjustment is used to weight and synthesize the received signals of each antenna belonging to each sub-array antenna, and the arrival direction of radio waves is estimated based on the synthesized signal. At the same time, the arrival direction of radio waves is estimated based on the received signals of a plurality of antennas, and a technique for removing a direction different from the actual arrival direction of radio waves based on the difference between the respective estimation results is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above prior art, when performing arrival direction estimation using the received signal of each sub-array antenna and arrival direction estimation using the received signal output from each antenna in parallel, two arrival direction estimation means are required, and the implementation cost may increase. Alternatively, when different arrival direction estimation processes are executed in a time-sharing manner, the processing speed may decrease.

[0005] This disclosure has been made in view of the above, and aims to realize an arrival direction estimation device and an arrival direction estimation method that can appropriately estimate the direction of arrival of radio waves with a simple configuration or processing. [Means for solving the problem]

[0006] An approach direction estimation device according to one aspect of the present disclosure comprises: an array antenna having a plurality of antenna elements, wherein the phase centers of the plurality of antenna elements are aligned in one direction; a target estimation unit that estimates the approach direction of radio waves based on the received signal of each antenna element; a power estimation unit that estimates the power in the approach direction for each of a plurality of sub-array antennas, each containing the same number of antenna elements; and a target determination unit that determines the approach direction as the approach direction estimation target when the amount of variation in the power in the approach direction estimated for each sub-array antenna is less than or equal to a predetermined value.

[0007] This configuration allows for the distinction between the estimated direction of arrival target and false images caused by side lobes, and suppresses the effects of side lobes that increase due to phase shifts between antenna elements. Furthermore, it enables accurate estimation of the direction of arrival of radio waves with a simple configuration.

[0008] A method for estimating the direction of arrival of a radio wave, according to one aspect of the present disclosure, includes: a target estimation step of estimating the direction of arrival of a radio wave based on the received signal of each antenna element whose phase centers are aligned in one direction; a power estimation step of estimating the power in the direction of arrival for each of a plurality of sub-array antennas, each containing the same number of antenna elements; and a target determination step of determining the direction of arrival as the target of the direction of arrival estimation if the amount of variation in the power in the direction of arrival estimated for each sub-array antenna is less than or equal to a predetermined value.

[0009] This configuration allows for the distinction between the estimated direction of arrival target and false images caused by side lobes, and suppresses the effects of side lobes that increase due to phase shifts between antenna elements. Furthermore, it enables accurate estimation of the direction of arrival of radio waves through simple processing. [Effects of the Invention]

[0010] According to this disclosure, an arrival direction estimation device and an arrival direction estimation method can be realized that can appropriately estimate the direction of arrival of radio waves with a simple configuration or processing. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing a schematic configuration of an arrival direction estimation device according to an embodiment. [Figure 2] Figure 2 is a schematic diagram showing an example of the antenna mounting surface of a dielectric substrate that constitutes an array antenna. [Figure 3A] Figure 3A is a conceptual diagram showing the positional relationship between the direction of arrival estimation device and the direction of arrival estimation target according to the embodiment. [Figure 3B] Figure 3B is a conceptual diagram showing the estimated position of the direction of arrival from the received signal of each antenna element. [Figure 4] Figure 4 is a conceptual diagram showing the direction of arrival of radio waves from the estimated direction of arrival target. [Figure 5] Figure 5 is a conceptual diagram showing the relationship between the phase center and phase difference of an antenna element. [Figure 6] Figure 6 is a conceptual diagram showing the variation in the phase center of the antenna element. [Figure 7] Figure 7 is a flowchart showing an example of the direction of arrival estimation process by the direction of arrival estimation device according to the embodiment. [Figure 8] Figure 8 is a conceptual diagram showing an example of a subarray configuration according to the embodiment. [Figure 9] Figure 9 is a conceptual diagram showing an example of the definition of the phase center position of each antenna element in the subarray configuration according to the embodiment. [Figure 10] Figure 10 is a flowchart showing an example of the power estimation process. [Figure 11] Figure 11 shows the power in the direction of arrival plotted in the direction of the subarray arrangement. [Figure 12]Figure 12 is a flowchart showing an example of the target discrimination process. [Figure 13] Figure 13 is a conceptual diagram showing a first example of an antenna configuration according to a first modified embodiment. [Figure 14] Figure 14 is a conceptual diagram showing a second example of an antenna configuration according to the first modified embodiment. [Figure 15] Figure 15 is a conceptual diagram showing a first example of a subarray configuration according to a second modified embodiment. [Figure 16] Figure 16 is a conceptual diagram showing a second example of a subarray configuration according to a second modified embodiment. [Modes for carrying out the invention]

[0012] The direction of arrival estimation apparatus and direction of arrival estimation method according to the embodiments will be described in detail below with reference to the drawings. However, this disclosure is not limited by these embodiments.

[0013] Figure 1 is a block diagram showing the schematic configuration of an approach direction estimation device according to an embodiment. The approach direction estimation device 1 according to the embodiment includes an array antenna 11, a target estimation unit 12, a sub-array signal extraction unit 13, a power estimation unit 14, and a target discrimination unit 15.

[0014] Figure 2 is a schematic diagram showing an example of the antenna mounting surface of a dielectric substrate constituting an array antenna. In this embodiment, as shown in Figure 2, the array antenna 11 is an equally spaced linear array antenna in which the phase centers of a plurality of antenna elements A(m) (where m is an integer from 1 to M) are aligned equally in one direction. Each antenna element A(m) is connected to a plurality of patch antennas Pa provided on the dielectric substrate by a feed line Pl, and a feed point is provided at one end. In this disclosure, the array antenna 11 is not limited to the embodiment shown in Figure 2, as long as at least the phase centers are aligned in one direction.

[0015] Figure 3A is a conceptual diagram showing the positional relationship between the direction of arrival estimation device and the direction of arrival estimation target according to the embodiment. Figure 3B is a conceptual diagram showing the position of the direction of arrival estimated from the received signal of each antenna element. In Figures 3A and 3B, the horizontal axis shows the direction of arrangement of the antenna elements A(m), and the vertical axis shows the direction perpendicular to the direction of arrangement of the antenna elements A(m). Point a in Figure 3B indicates the position corresponding to the direction of arrival estimation target Tp of the direction of arrival estimation device 1 according to the embodiment, and the multiple points b indicate false images that appear in a direction different from the direction of arrival estimation target Tp.

[0016] Figure 4 is a conceptual diagram showing the direction of arrival of radio waves from the estimated direction of arrival target. Figure 5 is a conceptual diagram showing the relationship between the phase center and phase difference of antenna elements. In Figures 4 and 5, the horizontal axis shows the direction of arrangement of the antenna elements, and the vertical axis shows the direction perpendicular to the direction of arrangement of the antenna elements. The black dots in the figures indicate the phase center of the antenna elements. In Figures 4 and 5, the phase centers of the antenna elements are arranged on the horizontal axis. In Figure 4, the phase centers of six antenna elements are shown as an example.

[0017] In an ideal array antenna, the spacing d between the phase centers of each antenna element is assumed to be constant. For example, the spacing d between the phase centers of each antenna element in an ideal array antenna is given by λ / 2 (λ: wavelength of the radio wave received by each antenna element). The direction of arrival of the radio wave from the estimated direction of arrival target Tp is defined by the angle of arrival θ, where the direction perpendicular to the direction of the antenna element arrangement is 0 degrees. The phase φ(d,θ) between each antenna element at the estimated direction of arrival target Tp is given by equation (1) below.

[0018]

number

[0019] As shown in Figure 5, radio waves from the target Tp for estimating the direction of arrival are incident on each antenna element with a phase difference of ξ2, ξ3, ξ4, ..., when the phase center of a certain antenna element is used as the reference point. The direction of arrival of the radio waves can be estimated from this phase difference.

[0020] On the other hand, the phase center of each antenna element A(m) in an actual array antenna varies due to manufacturing variations in the array antenna, aging degradation, or electromagnetic interactions between antenna elements (inter-antenna electromagnetic coupling), as shown in Figure 6. Figure 6 is a conceptual diagram showing the variation in the phase centers of antenna elements. In this case, if the distance between the phase centers of each antenna element is d', the phase φ(d',θ) is expressed by the following equation (2).

[0021]

number

[0022] The phase φ(d',θ) shown in equation (2) above includes the variation in the phase center of each antenna element in an actual array antenna. Due to this variation in the phase center of each antenna element, the side lobes increase, and as shown in Figure 3B, in addition to position a corresponding to the estimated direction of arrival target Tp, multiple false images b appear in directions different from position a corresponding to the estimated direction of arrival target Tp.

[0023] Therefore, in this disclosure, the array antenna 11 is divided into sub-arrays, and the power in the direction of arrival is estimated for each sub-array. If the amount of variation in the power in the direction of arrival estimated for each sub-array is less than or equal to a predetermined value, the direction of arrival is determined to be the estimated direction of arrival target Tp. This makes it possible to exclude false images b that appear in a direction different from position a corresponding to the estimated direction of arrival target Tp.

[0024] The following describes specific examples of processing in each component of the direction of arrival estimation device 1 according to the embodiment: the target estimation unit 12, the subarray signal extraction unit 13, the power estimation unit 14, and the target discrimination unit 15. Figure 7 is a flowchart showing an example of the direction of arrival estimation process by the direction of arrival estimation device according to the embodiment.

[0025] In the direction of arrival estimation process shown in Figure 7, the direction of arrival estimation device 1 receives the received signal x from each antenna element A(m). mBased on this, the arrival angle θ of the radio wave k (hereinafter, also referred to as "target angle θ k ") is estimated (target estimation process, step S001). The target estimation process (arrival direction estimation process) is executed by the target estimation unit 12. As the arrival direction estimation method in the target estimation unit 12, for example, the AF (Annihilating Filter) method using an annihilating filter (hereinafter, also referred to as the "AF method"), FFT, Prony method, beamformer (Beamformer) method (hereinafter, also referred to as the "BF method"), MUSIC (Multiple Signal Classification) method, etc. are exemplified. Note that, by using, for example, the AF method as the arrival direction estimation method in the target estimation unit 12, high angular resolution can be obtained. Thereby, a plurality of targets with close angles can be separated.

[0026] The target angle θ k can be expressed by the following formula (3). Further, the target estimation unit 12 generates the inter-antenna element phase difference z k corresponding to the target angle θ k shown by the following formula (3). The inter-antenna element phase difference z k can be expressed by the following formula (4).

[0027]

Equation

[0028]

Equation

[0029] The number of arrival directions estimated in the observation range of the arrival direction estimation device 1 is unknown. The target angle θ k (k is an integer from 1 to K, and K is unknown) estimated by the target estimation unit 12 includes the positions corresponding to the arrival direction estimation target Tp and a plurality of target angles θ k corresponding to positions different from the arrival direction estimation target Tp. Hereinafter, the arrival direction estimated by the target estimation unit 12 is also referred to as "arrival direction k".

[0030] FIG. 8 is a conceptual diagram showing an example of a sub-array configuration according to an embodiment. In FIG. 8, in an equally spaced linear array antenna in which the phase centers of the antenna elements A(m) are arranged at substantially equal intervals, the phase centers of the antenna elements A(m) are arranged in order from one end (the left end in FIG. 8) of the array antenna 11, and while shifting one element at a time, an example in which sub-array antennas SA(n) (n is an integer from 1 to N, N < M) with the number of elements R are arranged is shown. Further, in FIG. 8, the number of elements M of the array antenna 11 is 6, the total number N of each sub-array antenna SA(n) is 4, and the number of elements R of each sub-array antenna SA(n) is 3.

[0031] The number of elements M of the array antenna 11, the total number N of the sub-array antennas SA(n), and the number of elements R of each sub-array antenna SA(n) shown in FIG. 8 are merely examples and are not limited thereto. In the present disclosure, the number of elements R of each sub-array antenna SA(n) is the same, and each sub-array antenna SA(n) only needs to have substantially the same interval between the phase centers of adjacent antenna elements in the arrangement direction of the antenna elements A(r) (r is an integer from 1 to R).

[0032] Specifically, in the example shown in FIG. 8, the interval between the phase center of the antenna element A(1) included in the sub-array antenna SA(1) and the phase center of the antenna element A(2), the interval between the phase center of the antenna element A(2) included in the sub-array antenna SA(2) and the phase center of the antenna element A(3), the interval between the phase center of the antenna element A(3) included in the sub-array antenna SA(3) and the phase center of the antenna element A(4), and the interval between the phase center of the antenna element A(4) included in the sub-array antenna SA(4) and the phase center of the antenna element A(5) are each substantially the same.

[0033] Furthermore, in the example shown in Figure 8, the distance between the phase center of antenna element A(2) and the phase center of antenna element A(3) included in subarray antenna SA(1), the distance between the phase center of antenna element A(3) and the phase center of antenna element A(4) included in subarray antenna SA(2), the distance between the phase center of antenna element A(4) and the phase center of antenna element A(5) included in subarray antenna SA(3), and the distance between the phase center of antenna element A(5) and the phase center of antenna element A(6) included in subarray antenna SA(4) are all approximately the same.

[0034] Furthermore, if the array antenna 11 is an equally spaced linear array antenna, the spacing between the phase centers of all adjacent antenna elements A(r) in each sub-array antenna SA(n) will be approximately equal.

[0035] Figure 9 is a conceptual diagram showing an example of the definition of the phase center position of each antenna element in a subarray configuration according to the embodiment. In Figure 9, in a subarray antenna SA with R elements, the phase center position of each antenna element A(r) is defined as l r-1 That is what they say.

[0036] Specifically, in the example shown in Figure 9, the phase center position of antenna element A(1) is l0, the phase center position of antenna element A(2) is l1, the phase center position of antenna element A(3) is l2, and the phase center position of antenna element A(R) is l R-1 That is what they say.

[0037] Phase center position l of each antenna element A(r) of the subarray antenna SA r-1 When the spacing between each antenna element A(r) is λ / 2, the phase center position l0 of antenna element A(1) at one end of the subarray antenna SA (the left end in Figure 9) is taken as the reference position (l0=0), the phase center position l1=λ / 2 of antenna element A(2), the phase center position l2=2λ / 2 (=λ) of antenna element A(3), and the phase center position l of antenna element A(R) R-1 =(R-1)λ / 2.

[0038] In the direction of arrival estimation process shown in Figure 7, the direction of arrival estimation device 1 estimates the power in the direction of arrival k for each subarray antenna SA(n) (power estimation process, step S002). The power estimation process is performed by the subarray signal extraction unit 13 and the power estimation unit 14. Figure 10 is a flowchart of an example of the power estimation process. Here, we will first explain the concepts of the processing in the subarray signal extraction unit 13 and the power estimation unit 14.

[0039] The subarray signal extraction unit 13 uses the column vector X shown in equation (5) below. n This generates the signal obtained by each antenna element A(r) in a subarray antenna SA(n) with R elements, x n+r-1 This can be generalized as follows.

[0040]

number

[0041] When the total number of incoming directions k is K, the complex amplitude s of each incoming direction k in the subarray antenna SA(n) is k (n) is the column vector S shown in equation (6) below. n Expressed as, the column vector X shown in equation (5) above n and the column vector S shown in equation (6) below n This can be expressed by the relationship shown in equation (7) below. V shown in equation (7) below + This is the generalized inverse of the matrix V shown in equation (8) below.

[0042]

number

[0043]

number

[0044]

number

[0045] In equation (8) above, w can be expressed by equation (9) below.

[0046]

number

[0047] The power estimation unit 14 calculates the complex amplitude s of each incoming direction k obtained by equations (5) to (9) above. k Using (n), the power p for each sub-array antenna SA(n) in each direction of arrival k is given. k Calculate (n). Power p for each sub-array antenna SA(n) in each incoming direction k. k (n) can be calculated using the following formula (10).

[0048]

number

[0049] In the power estimation process shown in Figure 10, the power estimation unit 14 calculates the phase difference between antenna elements z in each incoming direction k calculated by the target estimation unit 12. k Using this, we generate the matrix V shown in equation (8) above (step S201).

[0050] When the spacing between each antenna element A(r) of the subarray antenna SA(n) is λ / 2, the matrix V shown in equation (8) above can be transformed into equation (11) below.

[0051]

number

[0052] The direction of arrival estimation device 1 initializes the number n of the subarray antenna SA(n) (n=0, step S202), increments the number n (n=n+1, step S203), and then performs the subsequent processing.

[0053] The sub-array signal extraction unit 13 receives the received signal x from the antenna element A(r) included in each sub-array antenna SA(n). n+r-1 Extract the following to obtain the column vector X shown in equation (5) below. n Generate (step S204).

[0054] The power estimation unit 14 uses equations (5) to (9) above to calculate the complex amplitude s of each incoming direction k. k (n) is calculated (step S205), and the power p for each sub-array antenna SA(n) in each incoming direction k is calculated using the above equation (10). k Calculate (n) (step S206).

[0055] The direction of arrival estimation device 1 determines whether the number n of the subarray antenna SA(n) is N or not (step S207), and if the number n of the subarray antenna SA(n) is not N (step S207; No), in other words, the power p in each direction of arrival k. k If the calculation of (n) is not completed, the process returns to step S203, the number n of the subarray antenna SA(n) is incremented (n=n+1, step S203), and the processes from step S204 to step S207 by the subarray signal extraction unit 13 and the power estimation unit 14 are repeatedly executed. When the number n of the subarray antenna SA(n) becomes N (step S207; Yes), in other words, the power p in each direction of arrival k is k Once the calculation of (n) is complete, the process returns to the direction of arrival estimation process shown in Figure 7.

[0056] Figure 11 shows the power in the direction of arrival plotted in the direction of the subarray arrangement. In Figure 11, the vertical axis represents the power p in the direction of arrival k. k The horizontal axis shows the sub-array antenna SA(n) number n. If the direction of arrival k corresponds to the direction of arrival target Tp (see Figures 3A and 3B), then the power p for each sub-array antenna SA(n) is shown. k It is expected that the variation will decrease. On the other hand, if the direction of arrival k is a false image that is different from the direction of the estimated direction of arrival target Tp, the power p for each subarray antenna SA(n) kIt is assumed that the variability will be relatively large compared to the estimated target Tp of the direction of arrival.

[0057] In the direction of arrival estimation process shown in Figure 7, the direction of arrival estimation device 1 estimates the power p for each sub-array antenna SA(n). k A comparison process is performed between the amount of variation and a predetermined value to determine the truth or falsity of the direction of arrival k (target determination process, step S003). The target determination process is performed by the target determination unit 15. Figure 12 is a flowchart of an example of the target determination process. Here, we will first explain the concept of the processing in the target determination unit 15.

[0058] In this embodiment, the power p in the direction of arrival k is calculated using the following equation (12). k (n) mean p av (k) is calculated, and the power p in the direction of arrival k is calculated using equation (13) below. k Standard deviation p of (n) σ (k) is calculated. Then, the mean value p is calculated using equation (12) below. av (k), and the standard deviation p calculated using equation (13) below. σ Using (k), the α(k) calculated by equation (14) below is used to express the power p in the direction of arrival k. k This is defined as the amount of variation.

[0059]

number

[0060]

number

[0061]

number

[0062] The target determination unit 15 uses equations (12) to (14) above to determine the power p in the direction of arrival k. k The variation α(k) is calculated.

[0063] Furthermore, power p in the direction of arrival k. k The amount of variation is not limited to the above. Specifically, the power p in the direction of arrival k. k As the amount of variation, for example, the standard deviation p calculated using equation (13) above. σ (k) may be used, or power p k It is also acceptable to use the variance value of (n).

[0064] The target determination unit 15 determines, for example, the power p in the direction of arrival k obtained by equations (12) to (14) above. k The variation amount α(k) and a predetermined threshold α set in advance. th A comparison and determination is made. Power p in the direction of arrival k. k The variation amount α(k) is the threshold α th The direction of arrival k is considered the estimated direction of arrival target Tp if the following conditions are met. This allows us to exclude false images that appear in a direction different from the estimated direction of arrival target Tp.

[0065] The direction corresponding to the estimated direction of arrival target Tp (see Figures 3A and 3B) estimated by each sub-array antenna SA(n) differs from the direction corresponding to the side lobe due to variations in the phase center of each sub-array antenna SA(n). This variation in the phase center of each sub-array antenna SA(n) causes variations in the power from the side lobe. Therefore, it is assumed that the direction in which there is a large power variation between each sub-array antenna SA(n) is a false image.

[0066] Here, when the AF method is used as the direction of arrival estimation method in the target estimation unit 12, it has higher accuracy compared to direction of arrival estimation methods such as FFT and BF method, and it is possible to accurately estimate the peak power from the direction of arrival estimation target Tp. As a result, the amount of variation in power from the false image among each subarray antenna SA(n) becomes relatively larger, which improves the accuracy of the target discrimination process in the target discrimination unit 15 (see Figure 12).

[0067] In the target discrimination process shown in Figure 12, the direction of arrival estimation device 1 initializes the number k of the direction of arrival k (k=0, step S301), increments the number k (k=k+1, step S302), and then executes the subsequent processes.

[0068] The target determination unit 15 uses equations (12) to (14) above to determine the power p in the direction of arrival k. k The variation amount α(k) is calculated (step S303), and the power p in the direction of arrival k is calculated. k The variation amount α(k) is a predetermined threshold α th Determine whether or not (α(k)≦α th (Step S304).

[0069] Power p in the direction of arrival k k The variation amount α(k) is the threshold α th If the following conditions apply (α(k)≦α th Step S304; Yes), the target determination unit 15 sets the value u(k) corresponding to the direction of arrival k to the boolean value "True" (u(k) = "True", step S305). Power p in the direction of arrival k k The variation amount α(k) is the threshold α th If it exceeds (step S304; No), the target determination unit 15 sets the value u(k) corresponding to the direction of arrival k to the truth value "False" (u(k) = "False", step S306).

[0070] The direction of arrival estimation device 1 determines whether the number k of the direction of arrival k is K (step S307). If the number k of the direction of arrival k is not K (step S307; No), in other words, if the truth value determination for all directions of arrival k has not been completed, the device returns to the process in step S302, increments the number k of the direction of arrival k (k=k+1, step S302), and repeatedly executes the processes from step S303 to step S307 by the target determination unit 15. When the number k of the direction of arrival k becomes K (step S307; Yes), in other words, when the truth value determination for all directions of arrival k has been completed, the device returns to the direction of arrival estimation process shown in Figure 7 and terminates the direction of arrival estimation process.

[0071] Furthermore, the direction of arrival estimation device 1 and the direction of arrival estimation direction related to this disclosure can be used, for example, in communication terminal equipment to improve the detection accuracy of base stations and other terminal equipment. Specifically, for example, after the direction of arrival estimation process shown in Figure 7, the direction of arrival estimation device 1 (target discrimination unit 15) determines the target angle θ corresponding to the direction of arrival k, with the value u(k) set to the truth value "True". k Target angle θ Tp This is output to the communication terminal device. As a result, the communication terminal device receives the target angle θ of the estimated arrival direction target Tp, which has been appropriately estimated by the arrival direction estimation process according to the embodiment. Tp This can be used to improve the detection accuracy of base stations and other terminal devices.

[0072] Furthermore, the direction of arrival estimation device 1 and the direction of arrival estimation direction related to this disclosure can be used, for example, to improve the accuracy of target position estimation in a radar device mounted on a moving object such as an automobile. Specifically, for example, after the direction of arrival estimation process shown in Figure 7, the direction of arrival estimation device 1 (target discrimination unit 15) determines the target angle θ corresponding to the direction of arrival k, where the value u(k) is set to the truth value "True". k Target angle θ Tp This is output to the radar device. As a result, the radar device outputs the target angle θ of the estimated target Tp, which is appropriately estimated by the direction of arrival estimation process according to the embodiment. Tp This method can be used to improve the accuracy of estimating the target position.

[0073] (First variation) Figure 13 is a conceptual diagram showing a first example of an antenna configuration according to the first modification of the embodiment. Figure 14 is a conceptual diagram showing a second example of an antenna configuration according to the first modification of the embodiment. In Figure 8, an equally spaced linear array antenna is illustrated in which the phase centers of each antenna element A(m) are arranged at approximately equal intervals, but a configuration comprising multiple equally spaced linear array antennas (array antennas 111, 112) is also possible. In the first example of the first modification shown in Figure 13, a configuration in which the orientations of the antenna elements of the two array antennas 111, 112 overlap is illustrated. In the second example of the first modification shown in Figure 14, a configuration in which the orientations of the antenna elements of the two array antennas 111, 112 are arranged in parallel is illustrated.

[0074] (Second variation) Figure 15 is a conceptual diagram showing a first example of a subarray configuration according to a second modification of the embodiment. Figure 16 is a conceptual diagram showing a second example of a subarray configuration according to a second modification of the embodiment. In the second modification, the array antennas 11a and 11b are exemplified as unequal-spacing linear array antennas in which the phase centers of the antenna elements A(m) are arranged at unequal intervals. This increases the design freedom of the beam pattern. Specifically, for example, it is possible to adopt a beam pattern that suppresses specific side lobes. In this case, the spacing between the antenna elements A(m) should be set to match the target beam pattern.

[0075] In the first example of the second modified example shown in Figure 15, an example is shown in which the number of antenna elements R of each sub-array antenna SA(1) and SA(2) is 4, but the invention is not limited to this. For each sub-array antenna SA(1) and SA(2), it is sufficient that the spacing between the phase centers of adjacent antenna elements in the direction of the arrangement of antenna elements A(r) is approximately the same.

[0076] Specifically, in the first example of the second modified example shown in Figure 15, the distance between the phase center of antenna element A(1) and the phase center of antenna element A(2) included in array antenna SA(1) is approximately the same as the distance between the phase center of antenna element A(4) and the phase center of antenna element A(5) included in sub-array antenna SA(2). Furthermore, the distance between the phase center of antenna element A(2) and the phase center of antenna element A(3) included in sub-array antenna SA(1) is approximately the same as the distance between the phase center of antenna element A(5) and the phase center of antenna element A(6) included in sub-array antenna SA(2). Furthermore, the distance between the phase center of antenna element A(3) and the phase center of antenna element A(4) included in sub-array antenna SA(1) is approximately the same as the distance between the phase center of antenna element A(6) and the phase center of antenna element A(7) included in sub-array antenna SA(2).

[0077] Furthermore, in the first example of the second modified configuration shown in Figure 15, the phase center position l0 of antenna element A(1) at one end of the subarray antenna SA(1) (the left end in Figure 15) is set as the reference position (l0=0), and the phase center position l1=3λ / 2 for antenna element A(2), l2=4λ / 2 (=2λ) for antenna element A(3), and l3=5λ / 2 for antenna element A(4).

[0078] In the first example of the second modified form shown in Figure 15, the matrix V shown in equation (8) above is the phase center position l of each antenna element A(r). r-1 Applying this to w shown in (9) above, it can be transformed into equation (15) below. The generalized inverse matrix V of the matrix V shown in equation (15) below + By applying this, power estimation processing similar to that in the embodiment (see Figure 10) can be performed.

[0079]

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[0080] In the second example of the second modified example shown in Figure 16, an example is given in which the number of antenna elements R of each subarray antenna SA(1) and SA(2) is 5, but the invention is not limited to this. For each subarray antenna SA(1) and SA(2), it is sufficient that the spacing between the phase centers of adjacent antenna elements in the direction of the arrangement of antenna elements A(r) is approximately the same.

[0081] Specifically, in the second example of the second modified example shown in Figure 16, the distance between the phase center of antenna element A(1) and the phase center of antenna element A(2) included in array antenna SA(1) is approximately the same as the distance between the phase center of antenna element A(4) and the phase center of antenna element A(5) included in sub-array antenna SA(2). Furthermore, the distance between the phase center of antenna element A(2) and the phase center of antenna element A(3) included in sub-array antenna SA(1) is approximately the same as the distance between the phase center of antenna element A(5) and the phase center of antenna element A(6) included in sub-array antenna SA(2). Furthermore, the distance between the phase center of antenna element A(3) and the phase center of antenna element A(4) included in sub-array antenna SA(1) is approximately the same as the distance between the phase center of antenna element A(6) and the phase center of antenna element A(7) included in sub-array antenna SA(2). Furthermore, the distance between the phase center of antenna element A(4) and the phase center of antenna element A(5) included in subarray antenna SA(1) is approximately the same as the distance between the phase center of antenna element A(7) and the phase center of antenna element A(8) included in subarray antenna SA(2).

[0082] In the second example of the second modified form shown in Figure 16, the phase center position l of each antenna element A(r) r-1 By applying this to w shown in (9) above and transforming the matrix V shown in equation (8) above, we obtain the generalized inverse matrix V of the matrix V. + Using this, power estimation processing similar to that in the embodiment (see Figure 10) can be performed.

[0083] Furthermore, in this second modified example using such an unequal-spacing linear array antenna, the BF method, the MUSIC method, or the like can be used as the direction of arrival estimation method in the target estimation unit 12.

[0084] In the embodiments described above, there is some variation. The embodiments described above are provided to facilitate understanding of this disclosure and are not intended to limit the invention. This disclosure may be modified or improved without departing from its spirit, and equivalents thereof are also included.

[0085] This disclosure may take the following configuration, as described above, or alternatively.

[0086] (1) An approach direction estimation device according to one aspect of the present disclosure comprises: an array antenna having a plurality of antenna elements, wherein the phase centers of the plurality of antenna elements are aligned in one direction; a target estimation unit that estimates the approach direction of radio waves based on the received signal of each antenna element; a power estimation unit that estimates the power in the approach direction for each of a plurality of sub-array antennas, each containing the same number of antenna elements; and a target determination unit that determines the approach direction as an approach direction estimation target when the amount of variation in the power in the approach direction estimated for each sub-array antenna is less than or equal to a predetermined value.

[0087] This configuration allows for the distinction between the estimated direction of arrival target and false images caused by side lobes, and suppresses the effects of side lobes that increase due to phase shifts between antenna elements. Furthermore, it enables accurate estimation of the direction of arrival of radio waves with a simple configuration.

[0088] (2) In the direction of arrival estimation device described in (1) above, the distance between the phase center of a first antenna element and the phase center of a second antenna element adjacent to each other in the direction of the arrangement of the antenna elements of the multiple subarray antennas is substantially the same.

[0089] (3) In the direction of arrival estimation device described in (2) above, the array antenna has the phase centers of the multiple antenna elements arranged at approximately equal intervals.

[0090] (4) In the direction of arrival estimation device described in (3) above, the target estimation unit estimates the direction of arrival of the radio waves using the vanishing filter method.

[0091] (5) In the direction of arrival estimation device described in (2) to (4) above, the target estimation unit determines the phase difference z between the antenna elements in the direction of arrival. k (where k is an integer from 1 to the total number of incoming directions K) The power estimation unit calculates the wavelength of the received radio wave as λ, the total number of sub-array antennas as N, the number of antenna elements included in the sub-array antenna as R, and the received signal for each antenna element included in the sub-array antenna as x n+r-1 (where n is an integer from 1 to N, and r is an integer from 1 to R), the phase center position of each antenna element is set to l, with the phase center position of the antenna element at one end of the subarray antenna as the reference position. r-1 , the complex amplitude for each direction of arrival is s k When (n) is used, the power p in the direction of arrival for each subarray antenna is calculated using equations (16) to (21) below. k Calculate (n).

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[0098] (6) In the direction of arrival estimation device described in (5) above, the target determination unit uses the following equation (22) to determine the power p in the direction of arrival for each subarray antenna. k (n) mean p av (k) is calculated, and the power p in the direction of arrival for each subarray antenna is calculated using equation (23) below. k Standard deviation p of (n) σ (k) is calculated, and the power p in the direction of arrival for each subarray antenna is calculated using equation (24) below. k Calculate the variation α(k) of (n).

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[0102] (7) A method for estimating the direction of arrival of a radio wave according to one aspect of the present disclosure includes: a target estimation step of estimating the direction of arrival of a radio wave based on the received signal of each antenna element whose phase centers are aligned in one direction; a power estimation step of estimating the power in the direction of arrival for each of a plurality of subarray antennas, each containing the same number of antenna elements; and a target determination step of determining the direction of arrival as the target of the direction of arrival estimation if the amount of variation in the power in the direction of arrival estimated for each subarray antenna is less than or equal to a predetermined value.

[0103] This configuration allows for the distinction between the estimated direction of arrival target and false images caused by side lobes, and suppresses the effects of side lobes that increase due to phase shifts between antenna elements. Furthermore, it enables accurate estimation of the direction of arrival of radio waves through simple processing.

[0104] (8) In the method for estimating the direction of arrival described in (7) above, the distance between the phase center of a first antenna element and the phase center of a second antenna element adjacent to each other in the direction of the arrangement of the antenna elements of the multiple subarray antennas is substantially the same.

[0105] (9) In the method for estimating the direction of arrival described in (8) above, the phase centers of the multiple antenna elements are arranged at approximately equal intervals.

[0106] (10) In the method for estimating the direction of arrival described in (9) above, the direction of arrival of the radio waves is estimated using the vanishing filter method in the target estimation step.

[0107] (11) In the method for estimating the direction of arrival described in (8) to (10) above, in the target estimation step, the phase difference z between the antenna elements in the direction of arrival k (where k is an integer from 1 to the total number of incoming directions K) is calculated, and in the power estimation step, the wavelength of the received radio wave is λ, the total number of sub-array antennas is N, the number of antenna elements included in the sub-array antenna is R, and the received signal for each antenna element included in the sub-array antenna is x n+r-1 (where n is an integer from 1 to N, and r is an integer from 1 to R), the phase center position of each antenna element is set to l, with the phase center position of the antenna element at one end of the subarray antenna as the reference position. r-1 , the complex amplitude for each direction of arrival is s k When (n) is used, the power p in the direction of arrival for each subarray antenna is calculated using equations (25) to (30) below. k Calculate (n).

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[0114] (12) In the method for estimating the direction of arrival described in (11) above, in the target determination step, the power p in the direction of arrival for each subarray antenna is determined using the following equation (31). k (n) mean p av (k) is calculated, and the power p in the direction of arrival for each subarray antenna is calculated using equation (32) below. k Standard deviation p of (n) σ (k) is calculated, and the power p in the direction of arrival for each subarray antenna is calculated using equation (33) below. k Calculate the variation α(k) of (n).

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[0118] This disclosure makes it possible to realize an arrival direction estimation device and an arrival direction estimation method that can appropriately estimate the direction of arrival of radio waves with a simple configuration or processing. [Explanation of symbols]

[0119] 1 Direction of arrival estimation device 11,11a,11b,111,112 Array Antenna 12 Target estimation part 13 Subarray signal extraction section 14 Power estimation section 15 Target discrimination part A(m) Antenna element SA(n) Subarray Antenna

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