ARRIVAL DIRECTION ESTIMATION DEVICE AND ARRIVAL DIRECTION ESTIMATION METHOD

Abstract

The present invention provides an arrival direction estimation apparatus and an arrival direction estimation method with which it is possible to appropriately estimate the arrival direction of a radio wave by a simple configuration or processing.The arrival direction estimation device comprises: an array antenna (11) having 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 based on 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 including the same number of antenna elements; and a target determination unit (15) that determines the arrival direction as 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 area

[0001] The present invention relates to an arrival direction estimation apparatus and an arrival direction estimation method. Background technology

[0002] In a communication device or radar (radio detection and measurement), it is a common technique to estimate the arrival direction of a radio wave using an array antenna obtained by arranging a plurality of antennas in an array. In the arrival direction estimation technique using such an array antenna, a direction different from the actual arrival direction of the radio wave is sometimes estimated as the arrival direction of the radio wave.Patent Document 1 discloses a technique in which the arrival direction of a radio wave is estimated based on a signal obtained by arranging a plurality of antennas capable of receiving two orthogonally polarized waves in a sub-array, weighting the reception signal of each antenna belonging to the sub-array antenna using at least one of phase shift and amplitude adjustment, and combining the weighted results. At the same time, the arrival direction of the radio wave is also estimated based on the respective reception signals of the plurality of antennas. Directions different from the actual arrival direction of the radio wave are removed based on the difference between the two estimation results. Reference listPatent document

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-57791 Brief description of the inventionTechnical problem

[0004] In the conventional technique described above, if the arrival direction estimation using the received signal from each sub-array antenna and the arrival direction estimation using the received signal output from each antenna are performed in parallel, two arrival direction estimators are required, so the installation cost may become high. Alternatively, if different arrival direction estimation processes are performed in a time-shared manner, the processing speed may be reduced.

[0005] The present disclosure has been made in view of the above problems, and an object of the present disclosure is to realize an arrival direction estimation apparatus and an arrival direction estimation method capable of appropriately estimating the arrival direction of a radio wave through a simple configuration or processing. Solution to the problem

[0006] An arrival direction estimation device according to one aspect of the present disclosure includes: an array antenna having a plurality of antenna elements, wherein respective phase centers of the plurality of antenna elements are arranged in one direction; a target estimation unit that estimates an arrival direction of a radio wave based on a reception signal for each of the antenna elements; an electric power estimation unit that estimates an electric power in the arrival direction for each of a plurality of sub-array antennas, each including the same number of antenna elements; and a target discrimination unit that determines the arrival direction as an arrival facility estimation target when a variation amount of the electric power in the arrival direction estimated for each of the sub-array antennas is equal to or less than a predetermined value.

[0007] With such a configuration, the arrival direction estimation target and false images caused by side lobes can be distinguished, and the influence of side lobes, which increases due to the phase shift between the antenna elements, can be suppressed. Furthermore, the arrival direction of the radio wave can be appropriately estimated through a simple configuration.

[0008] An arrival direction estimation method according to one aspect of the present disclosure includes a target estimation step that estimates an arrival direction of a radio wave based on a reception signal for each of the antenna elements whose respective phase centers are arranged in one direction; an electric power estimation step that estimates an electric power in the arrival direction for each of a plurality of sub-array antennas each including the same number of the antenna elements; and a target determination step that determines the arrival direction as an arrival direction estimation target if a variation amount of the electric power in the arrival direction estimated for each of the sub-array antennas is equal to or less than a predetermined value.

[0009] With such a configuration, the arrival direction estimation target and false images caused by side lobes can be distinguished, and the influence of side lobes, which increases due to the phase shift between the antenna elements, can be suppressed. Furthermore, the arrival direction of the radio wave can be appropriately estimated through simple processing. Advantageous effects of the invention

[0010] According to the present disclosure, it is possible to realize an arrival direction estimation apparatus and an arrival direction estimation method capable of appropriately estimating the arrival direction of a radio wave through a simple configuration or processing. Short description of the drawings Fig. 1 is a block diagram showing a schematic configuration of an arrival direction estimation device according to an embodiment. Fig. 2 is a schematic diagram showing an example of an antenna mounting surface of a dielectric substrate constituting an array antenna. Fig. 3A is a conceptual diagram showing the positional relationship between the arrival direction estimation device according to the embodiment and an arrival direction estimation target. Fig. Figure 3B is a conceptual diagram showing positions of the arrival directions estimated from the received signal of each of the antenna elements. Fig. 4 is a conceptual diagram showing the arrival direction of a radio wave from the arrival direction estimation target. Fig. Figure 5 is a conceptual diagram showing the relationship between phase centers and phase differences of antenna elements. Fig. Figure 6 is a conceptual diagram showing variations in the phase centers of the antenna elements. Fig. 7 is a flowchart showing an example of an arrival direction estimation process performed by the arrival direction estimation device according to the embodiment. Fig. 8 is a conceptual diagram showing an example of a sub-array configuration according to the embodiment. Fig. 9 is a conceptual diagram showing an example of the definition of the phase center position of each of the antenna elements in the sub-array configuration according to the embodiment. Fig. 10 is a flowchart showing an example of an electric power estimation process. Fig. 11 is a graph obtained by plotting the electric power in the arrival direction in the arrangement direction of sub-arrays. Fig. Figure 12 is a flowchart showing an example of a target discrimination process. Fig. 13 is a conceptual diagram showing a first example of an antenna configuration according to a first modification of the embodiment. Fig. 14 is a conceptual diagram showing a second example of the antenna configuration according to the first modification of the embodiment. Fig. 15 is a conceptual diagram showing a first example of a sub-array configuration according to a second modification of the embodiment. Fig. 16 is a conceptual diagram showing a second example of the sub-array configuration according to the second modification of the embodiment. Description of the embodiments

[0011] An arrival direction estimation device and an arrival direction estimation method according to an embodiment will be described in detail below based on the drawings. Note that the present disclosure is not limited to such an embodiment.

[0012] Fig. 1 is a block diagram showing a schematic configuration of the arrival direction estimation device according to the embodiment. An arrival 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, an electric power estimation unit 14, and a target discrimination unit 15.

[0013] Fig. Fig. 2 is a schematic diagram showing an example of an antenna mounting surface of a dielectric substrate constituting the array antenna. In the present embodiment, the array antenna 11 is an equally spaced linear array antenna in which the phase centers of a plurality of antenna elements A(m) (m is an integer from 1 to M) are arranged at equal intervals in one direction, as shown in Fig. Fig. 2. Each of the antenna elements A(m) has a plurality of patch antennas Pa provided on the dielectric substrate and connected by a feed line P1, and a feed point is provided at one end of the feed line P1. In the present disclosure, the array antenna 11 is not limited to the Fig. 2, as long as it is at least one aspect in which the phase centers are arranged in one direction.

[0014] Fig. 3A is a conceptual diagram showing a positional relationship between the arrival direction estimation device according to the embodiment and an arrival direction estimation target. Fig. Figure 3B is a conceptual diagram showing the positions of the arrival directions estimated from the received signals of the respective antenna elements. Fig. 3A and Fig. 3B, the horizontal axis indicates the arrangement direction of the antenna elements A(m) and the vertical axis indicates the direction orthogonal to the arrangement direction of the antenna elements A(m). A point a, which is Fig. 3B indicates a position corresponding to an arrival direction estimation target Tp of the arrival direction estimation device 1 according to the embodiment, and a plurality of dots b indicate false images appearing in directions different from the arrival direction estimation target Tp.

[0015] Fig. 4 is a conceptual diagram showing the arrival direction of a radio wave from the arrival direction estimation target. Fig. Figure 5 is a conceptual diagram showing the relationship between phase centers and phase differences of the antenna elements. Fig. 4 and Fig. 5, the horizontal axis indicates the arrangement direction of the antenna elements and the vertical axis indicates the direction orthogonal to the arrangement direction of the antenna elements. Black dots in Fig. 4 and Fig. 5 show the phase centers of the antenna elements. In Fig. 4 and Fig. 5, the phase centers of the antenna elements are arranged next to each other on the horizontal axis. In Fig. Figure 4 shows the phase centers of six antenna elements as examples.

[0016] In an ideal array antenna, the distance d between the phase centers of the respective antenna elements is a constant. In an ideal array antenna, the distance d between the phase centers of the respective antenna elements is, for example, λ / 2 (λ represents the wavelength of the radio wave received by the respective antenna elements). The arrival direction of the radio wave from the arrival direction estimation target Tp is defined by an arrival angle θ with the direction orthogonal to the arrangement direction of the antenna elements set to 0 degrees. The phase φ (d, θ) between the respective antenna elements in the arrival direction estimation target Tp at this time is expressed by the following equation (1). Equation 1 ϕ(d,θ)=2πdλsinθ

[0017] As it is in Fig. 5, when the phase center of a certain antenna element is regarded as a reference point, the radio wave from the arrival direction estimation target Tp is incident on the respective antenna elements with phase differences of, for example, ξ2, ξ3, ξ4, ..., respectively. The arrival direction of the radio waves can be estimated from the phase differences.

[0018] On the other hand, as in Fig. 6, variations occur in the phase centers of the respective antenna elements A(m) in an actual array antenna due to manufacturing variations, aging of the array antenna, or electromagnetic interaction between the antenna elements (i.e., electromagnetic coupling between the antennas). Fig. Figure 6 is a conceptual diagram showing the variations in the phase centers of the antenna elements. When the distance between the phase centers of the respective antenna elements is d', the phase φ (d, θ) at this time is expressed by the following equation (2). Equation 2 ϕ(d'θ)=2πd'λsinθ

[0019] The phase φ (d, θ) shown in equation (2) above includes the variations in the phase centers of the respective antenna elements in an actual array antenna. Due to the variations in the phase centers of the respective antenna elements, side lobes increase; as shown in Fig. 3B, a plurality of false images b appear in directions different from a position a corresponding to the arrival direction estimation target Tp, in addition to the position a corresponding to the arrival direction estimation target Tp.

[0020] Therefore, in the present disclosure, the array antenna 11 is divided into sub-arrays, and the electric power in the arrival direction is estimated for each sub-array. When the amount of variation of the electric power in an arrival direction estimated for each sub-array is equal to or less than a predetermined value, such an arrival direction is determined as the arrival direction estimation target Tp. Thus, the false images b appearing in directions different from the position a corresponding to the arrival direction estimation target Tp can be excluded.

[0021] Specific examples of the processing in each of the target estimation unit 12, the sub-array signal extraction unit 13, the electric power estimation unit 14, and the target discrimination unit 15 of the arrival direction estimation device 1 according to the embodiment will be described below. Fig. 7 is a flowchart showing an example of an arrival direction estimation process performed by the arrival direction estimation device according to the embodiment.

[0022] In the Fig. 7, the arrival direction estimation device 1 estimates an arrival angle θk of the radio wave (hereinafter also referred to as “target angle θk”) based on a reception signal x mof each antenna element A(m) (a target estimation process, step S001). The target estimation process (the arrival direction estimation process) is performed by the target estimation unit 12. Examples of the arrival direction estimation technique in the target estimation unit 12 include an annihilation filter method (hereinafter also referred to as an "AF method") using an annihilation filter, an FFT, a Prony method, a beamformer method (hereinafter also referred to as a "BF method"), a MUSIC (Multiple Signal Classification) method, and the like. It should be noted that high angular resolution can be obtained when, for example, the AF method is used as the arrival direction targeting technique in the target estimation unit 12. Thus, a plurality of targets whose angles are close to each other can be separated.

[0023] The target angle θk can be expressed by the following equation (3). The target estimation unit 12 generates a phase difference z k between antenna elements corresponding to the target angle θk, which is expressed by the following equation (3). The phase difference z k between antenna elements can be expressed by the following equation (4). Equation 3 ϕk(d,θk)=2πdλsinθk Equation 4 zk=exp(jϕk)

[0024] The number of arrival directions estimated in the observation range of the arrival direction estimation device 1 is an unknown number. The target angle θk (k is an integer from 1 to K, where K is an unknown number) estimated by the target estimation unit 12 may include a plurality of target angles θk, each corresponding to a position corresponding to the arrival direction estimation target Tp and 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."

[0025] Fig. 8 is a conceptual diagram showing an example of a sub-array configuration according to the embodiment. Fig. Fig. 8 shows an example of a linear array antenna with equal intervals in which the respective phase centers of the antenna elements A(m) are arranged at substantially equal intervals, the phase centers of the antenna elements A(m) being arranged in an order from one end of the array antenna 11 (the left end in Fig. 8) are arranged, and sub-antennas Sa(n) with the number of elements R (n is an integer from 1 to N, where N <M) durch Verschieben um ein Element angeordnet werden. In Fig. 8, the element number M of the array antenna 11 is 6, the total number N of the sub-array antennas SA(n) is 4, and the element number R of each of the sub-array antennas SA(m) is 3.

[0026] The element number M of the array antenna 11, the total number N of the sub-array antennas SA(n) and the element number R of each of the sub-array antennas SA(n) which are in Fig. 8 are an example and are not limited to such an example. In the present disclosure, it is sufficient that the element number R of each of the sub-array antennas SA(n) is the same, and each of the sub-array antennas SA(n) has substantially the same distance between the respective phase centers of the antenna elements adjacent in the array direction of antenna elements A(r) (r is an integer from 1 to R).

[0027] More precisely, in the Fig. 8, the distance between the phase center of the antenna element A(1) and the phase center of the antenna element A(2) included in the sub-array antenna SA(1), the distance between the phase center of the antenna element A(2) and the phase center of the antenna element A(3) included in the sub-array antenna SA(2), the distance between the phase center of the antenna element A(3) and the phase center of the antenna element A(4) included in the sub-array antenna SA(3), and the distance between the phase center of the antenna element A(4) and the phase center of the antenna element A(5) included in the sub-array antenna SA(4) are substantially the same.

[0028] Furthermore, the Fig. 8, the distance between the phase center of the antenna element A(2) and the phase center of the antenna element A(3) included in the sub-array antenna SA(1), the distance between the phase center of the antenna element A(3) and the phase center of the antenna element A(4) included in the sub-array antenna SA(2), the distance between the phase center of the antenna element A(4) and the phase center of the antenna element A(5) included at the sub-array antenna SA(3), and the distance between the phase center of the antenna element A(5) and the phase center of the antenna element A(6) included in the sub-array antenna SA(4) are substantially the same.

[0029] When the array antenna 11 is an equally spaced linear array antenna, it should be noted that the distances between the phase centers of all adjacent antenna elements A(r) in each of the sub-array antennas SA(n) are substantially equal.

[0030] Fig. 9 is a conceptual diagram showing an example of the definition of the phase center position of each of the antenna elements in the sub-array configuration according to the embodiment. In Fig. 9, in a subarray antenna SA with the number of elements R, the phase center position of each of the antenna elements A(r) I r-1

[0031] More precisely, in the Fig. In the example shown in Figure 9, the phase center position of the antenna element A(1) is I0, the phase center position of the antenna element A(2) is I1, the phase center position of the antenna element A(3) is I2, and the phase center position of the antenna element A(R) is I R-1 .

[0032] If the distance between the respective antenna elements A(r) is λ / 2, with the phase center position I0 of the antenna element A(1) at one end (left end in Fig. 9) the sub-array antenna SA defined as a reference position (I0=0), the phase center position I r-1 of the respective antenna elements A(r) of the sub-array antenna SA as follows:

[0033] The phase center position I1 of the antenna element A(2) = λ / 2, the phase center position I2 of the antenna element A(3) = 2λ / 2 (=λ), and the phase center position I R-1 of the antenna element A(R) = (R-1)λ / 2.

[0034] In the Fig. In the arrival direction estimation process shown in Figure 7, the arrival direction estimation device 1 estimates the electric power in the arrival direction k for each sub-array antenna SA(n) (electric power estimation process, step S002). The electric power estimation process is executed by the sub-array signal extraction unit 13 and the electric power estimation unit 14. Fig. Figure 10 is a flowchart showing an example of the electric power estimation process. Here, the concepts of the processes in the sub-array signal extraction unit 13 and the electric power estimation unit 14 will be described first.

[0035] The sub-array signal extraction unit 13 generates a column vector X n , which is shown in the following equation (5). The received signal from each of the antenna elements A(r) in the sub-array antenna SA(n) with the element number R can be generalized as X n+r-1 . Equation 5 Xn=[xnxn+1⋮xn+(R−1)−1xn+(R−1)]

[0036] If a complex amplitude s k (n) of each arrival direction k in the subarray antenna SA(n) as a column vector S n which is shown in the following equation (6), where the total number of arrival directions is k, the column vector X n, which is shown in equation 5 above, and a column vector S n , shown in the following equation (6), can be expressed by a comparison expression shown in the following equation (7). V + , shown in the following equation (7), is a generalized inverse matrix of a matrix V shown in the following equation (8). Equation 6 Sn=[s1(n)s2(n)⋮sK−1(n)sK(n)] Equation 7 Sn=V+Xn Equation 8 V=[z1w0z2w0⋯zKw0z1w1z2w1⋯zKw1z1w2z2w2⋱zKw2⋮⋮⋯⋮z1wR−1z2wR−1⋯zKwR−1]

[0037] In the above equation (8), w can be expressed by the following equation (9). Equation 9 wr=2lrλ

[0038] The electric power estimation unit 14 uses the complex amplitude s k(n) in each arrival direction k obtained by the above equations (5) to (9) to obtain an electric power p k (n) for each subarray antenna SA(n) of each arrival direction k. The electrical power p k (n) for each sub-array antenna SA(n) in each arrival direction k can be calculated by the following equation (10). Equation 10 pk(n)=|sk(n)|2

[0039] In the Fig. In the electric power estimation process shown in Figure 10, the electric power estimation unit 14 uses the phase difference z k between antenna elements in each arrival direction k, which is calculated by the target estimation unit 12 to generate the matrix V shown in the above equation (8) (step S201).

[0040] When the distance between the respective antenna elements A(r) of the sub-array antenna SA(n) is λ / 2, the matrix V shown in the above equation (8) can be converted into the following equation (11). Equation 11 V=[11⋯zKw0z1z2⋯zKw1z12z22⋱zKw2⋮⋮⋯⋮z1R−1z2wR−1⋯zKwR−1]

[0041] The arrival direction estimation device 1 initializes the number n of the sub-array antennas SA(n) (“n=0” at step S202), increments the number n (“n=n+1” at step S203), and executes the subsequent processing.

[0042] The sub-array signal extraction unit 13 extracts the received signal x n+r-1 of the antenna element A(r) contained in each subarray antenna SA(n) and generates the column vector X n , which is represented by the following equation (5) (step S204).

[0043] The electric power estimation unit 14 uses the above equations (5) to (9) to calculate the complex amplitude s k (n) of each arrival direction k (step S205) and uses the above equation (10) to calculate the electric power p k (n) for each sub-array antenna SA(n) in each arrival direction k (step S206).

[0044] The arrival direction estimation device 1 determines whether the number n of the sub-array antenna SA(n) is N or not (step S207), and if the number n of the sub-array antenna SA(n) is not N (“No” at step S207), in other words, if the calculation of the electric power p k(n) in each arrival direction k has not been completed, the process returns to step S203, increments the number n of the sub-array antenna SA(n) (“n=n+1” at step S203), and repeats the process from step S204 to step S207 by the sub-array signal extraction unit and the electric power estimation unit 14. If the number n of the sub-array antenna SA(n) becomes N (“Yes” at step S207), in other words, if the calculation of the electric power p k (n) has been completed in each arrival direction k, the process returns to the one in Fig. 7 shown arrival direction estimation process.

[0045] Fig. Figure 11 is a graph obtained by plotting the electric power in the arrival direction in the arrangement direction of the sub-arrays. In Fig. 11 the vertical axis shows the electrical power p kin the arrival direction k and the horizontal axis indicates the number n of the sub-array antenna SA(n). If the arrival direction k corresponds to the arrival direction estimation target Tp (see Fig. 3A and Fig. 3B), it is expected that the variation of the electrical power p k for each of the sub-array antennas SA(n) will be small. On the other hand, if the arrival direction k is a false image different from the arrival direction estimation target Tp, it is assumed that the variation of the electric power p k for each sub-array antenna SA(n) will be relatively large with respect to the arrival direction estimation target Tp.

[0046] In the Fig. 7, the arrival direction estimation device 1 performs a comparison process between the variation amount of the electric power p kestimated for each sub-array antenna SA(n) and a predetermined value to determine true or false of the arrival direction k (a target discrimination process, step S003). The target discrimination process is executed by the target discrimination unit 15. Fig. Figure 12 is a flowchart showing an example of the target discrimination process.

[0047] Here, the concept of the process in the goal discrimination unit 15 is first described.

[0048] In the present embodiment, an average value p av (k) the electrical power p k (n) in the arrival direction k using the following equation (12), and a standard deviation p σ (k) the electrical power p k (n) in the arrival direction k is calculated using the following equation (13). Furthermore, α(k), calculated by the following equation (14) using the mean pav (k), calculated using the following equation (12) and the standard deviation p σ (k), calculated using the following equation (13), defined as the amount of variation of the electric power p k in the arrival direction k. Equation 12 pav(k)=1N∑n=1Npk(n) Equation 13 pσ(k)=1N∑n=1N[pk(n)−pav]2 Equation 14 α(k)=1+pσ(k)pav(k)

[0049] The target discrimination unit 15 uses the above equations (12) to (14) to calculate the variation amount α(k) of the electric power p k in the arrival direction k.

[0050] The amount of variation of the electrical power p k in the arrival direction k is not limited to the above. More specifically, the variation amount of the electric power p kin the arrival direction k can also be, for example, an aspect where the standard deviation p σ (k), calculated using the above equation (13), or an aspect in which the dispersion value of the electric power p k (n) is used.

[0051] The target discrimination unit 15 compares and determines the variation amount α(k) of the electric power p k in the arrival direction k, which is obtained by the above equations (12) to (14), for example with a predetermined threshold α th . If the variation amount α(k) of the electrical power p k in the arrival direction k equal to or less than the threshold α th , the arrival direction k is regarded as the arrival direction estimation target Tp. Thus, the false images appearing in directions different from the arrival direction estimation target Tp can be excluded.

[0052] The directions corresponding to the side lobes and the direction corresponding to the arrival direction estimation target Tp (see Fig. 3A and Fig. 3B) estimated by each sub-array antenna SA(n) differs depending on the variation in the phase center for each sub-array antenna SA(n). The variation in the phase center for each sub-array antenna SA(n) causes the variation in the electric power of the side lobes. Therefore, it is assumed that the direction in which the electric power variation between the sub-array antennas SA(n) is large represents a false image.

[0053] When the AF method is used as the arrival direction estimation technique in the target estimation unit 12, higher accuracy is obtained than that of an arrival direction estimation technique using FFT, the BF method, or the like, and the peak electric power of the arrival direction estimation target Tp can be accurately estimated. Since the amount of variation between the sub-array antennas SA(n) in the electric power of the false image is comparatively larger, the accuracy of the target discrimination process (see Fig. 12) in the target discrimination unit 15.

[0054] In the Fig. 12, the arrival direction estimation device 1 initializes the number k of the arrival direction k (“k=0” at step S301), increments the number k (“k=k+1” at step S302), and executes the subsequent processes.

[0055] The target discrimination unit 15 uses the above equations (12) to (14) to calculate the variation amount α(k) of the electric power p k in the arrival direction k (step S303), and determines whether the variation amount α(k) of the electric power p k in the arrival direction k is equal to or less than the predetermined threshold α th (α(k) ≤ α th ?" at step S304).

[0056] If the variation amount α(k) of the electrical power p k in the arrival direction k equal to or less than the threshold α th is (α(k) ≤ α th ; "Yes" at step S304), the destination discrimination unit 15 sets a value u(k) corresponding to the arrival direction k to the Boolean value "True" (u(k) = "True" at step S305). If the variation amount α(k) of the electric power p k in the arrival direction k the threshold value α thexceeds (“No” at step S304), the target discrimination unit 15 sets the value u(k) corresponding to the arrival direction k to the Boolean value “False” (u(k) = “False” at step S306).

[0057] The arrival direction estimation device 1 determines whether the number k of the arrival direction is k or not (step s307), and if the number k of the arrival direction is not K ("No" at step s307), in other words, if the determination of true or false of all the arrival directions k is not completed, the process returns to step S302, implements the number k of the arrival direction k ("k=k+1" at step S302), and repeats the processes from step S303 to S307 by the target discrimination unit 15. If the number k of the arrival direction becomes k ("Yes" at step S307), in other words, if the determination of true or false of all the arrival directions k is completed, the process returns to the step S302. Fig. 7 and the arrival direction estimation process is completed.

[0058] The arrival direction estimation device 1 and the arrival direction estimation device according to the present disclosure can be used to improve, for example, the detection accuracy of the base station or another terminal in a communication terminal. More specifically, for example, after performing the Fig. 7, the arrival direction estimation device 1 (the target discrimination unit 15) outputs to the communication terminal the target angle θk corresponding to the arrival direction k, with the value u(k) set to the Boolean value “true”, as the target angle θ Tp Thus, in the communication terminal, the detection accuracy of the base station or another terminal can be improved by using the target angle θ Tpof the arrival direction estimation target Tp, appropriately estimated by the arrival direction estimation process according to the embodiment.

[0059] In addition, the arrival direction estimation device 1 and the arrival direction estimation device according to the present disclosure can be used to improve, for example, the estimation accuracy of a target position in a radar device mounted on a mobile body such as an automobile. More specifically, for example, after performing the Fig. 7, the arrival direction estimation device 1 (the target discrimination unit 15) outputs to the radar device the target angle θk corresponding to the arrival direction k, with the value u(k) set to the Boolean value “true”, as the target angle θ Tp Thus, in the radar device, the estimation accuracy of the target position can be improved by using the target angle θ Tpof the arrival direction estimation target Tp, appropriately estimated by the arrival direction estimation process according to the embodiment. First modification

[0060] Fig. 13 is a conceptual diagram showing a first example of an antenna configuration according to a first modification of the embodiment. Fig. 14 is a conceptual diagram showing a second example of the antenna configuration according to the first modification of the embodiment. In Fig. 8 shows an example of an equally spaced linear array antenna in which the respective phase centers of the antenna elements A(m) are arranged at substantially equal intervals, but the present disclosure encompasses a configuration including a plurality of equally spaced linear array antennas (array antennas 111 and 112). The first example of the first modification shown in Fig. 13 exemplifies an aspect in which the arrangement directions of the respective antenna elements of the two array antennas 111 and 112 overlap each other. The second example of the first modification shown in Fig. 14 exemplifies an aspect in which the arrangement directions of the respective antenna elements of the two array antennas 111 and 112 are arranged in parallel. Second modification

[0061] Fig. 15 is a conceptual diagram showing a first example of a sub-array configuration according to a second modification of the embodiment. Fig. 16 is a conceptual diagram showing a second example of the sub-array configuration according to the second modification of the embodiment. The second modification exemplifies an aspect in which array antennas 11a and 11b are each an unequal-pitch linear array antenna in which respective phase centers of antenna elements A(m) are arranged at unequal intervals. Thus, the degree of freedom in designing a radiation pattern can be increased. For example, a radiation pattern in which a specific side lobe is suppressed can be adopted. In such a case, it is sufficient to adjust the pitch between the antenna elements A(m) so that it matches a target radiation pattern.

[0062] The first example of the second modification, which is Fig. 15 exemplifies an aspect in which the antenna element number R of each of the sub-array antennas SA(1) and SA(2) is 4, but the present disclosure is not limited to such an aspect. It is sufficient that each of the sub-array antennas SA(1) and SA(2) has substantially the same distance between the respective phase centers of the antenna elements adjacent in the arrangement direction of the antenna elements A(r).

[0063] More specifically, in the first example of the second modification, which is shown in Fig. As shown in Figure 15, the distance between the phase center of the antenna element A(1) and the phase center of the antenna element A(2) included in the array antenna SA(1) is substantially equal to the distance between the phase center of the antenna element A(4) and the phase center of the antenna element A(5) included in the sub-array antenna SA(2). Further, the distance between the phase center of the antenna element A(2) and the phase center of the antenna element A(3) included in the sub-array antenna SA(1) is substantially equal to the distance between the phase center of the antenna element A(5) and the phase center of the antenna element A(6) included in the sub-array antenna SA(2).Furthermore, the distance between the phase center of the antenna element A(3) and the phase center of the antenna element A(4) included in the sub-array antenna SA(1) is substantially the same as the distance between the phase center of the antenna element A(6) and the phase center of the antenna element A(7) included in the sub-array antenna SA(2).

[0064] In the first example of the second modification, which is shown in Fig. 15, the phase center position I0 of the antenna element A(1) at one end (left end in Fig. 15) of the sub-array antenna SA(1) is set as a reference position (I0=0), and the phase center position I1 of the antenna element A(2) is set as 3λ / 2, the phase center position I2 of the antenna element A(3) is set as 4λ / 2 (=2λ), and the phase center position I3 of the antenna element A(4) is set as 5λ / 2.

[0065] In the first example of the second modification, which is shown in Fig. 15, the matrix V shown in the above equation (8) can be converted into the following equation (15) by applying the phase center positions I r-1 of each antenna element A(r) to w, shown in equation (9) above. An electric power estimation process similar to that of the embodiment (see Fig. 10) can be carried out by creating a generalized inverse matrix V + a matrix V shown in the following equation (15). Equation 15 V=[11⋯1z13z23⋯zK3 z14z24⋯zK4z15z25⋯zK5]

[0066] The second example of the second modification, which is shown in Fig. 16 exemplifies an aspect in which the antenna element number R of each of the sub-array antennas SA(1) and SA(2) is 5, but the present disclosure is not limited to such an aspect. It is sufficient that each of the sub-array antennas SA(1) and SA(2) has substantially the same distance between the respective phase centers of the antenna elements adjacent in the array direction of the antenna elements A(r).

[0067] More specifically, in the second example of the second modification, which is shown in Fig. As shown in Fig. 16, the distance between the phase center of the antenna element A(1) and the phase center of the antenna element A(2) included in the array antenna SA(1) is substantially equal to the distance between the phase center of the antenna element A(4) and the phase center of the antenna element A(5) included in the sub-array antenna SA(2). Further, the distance between the phase center of the antenna element A(2) and the phase center of the antenna element A(3) included in the sub-array antenna SA(1) is substantially equal to the distance between the phase center of the antenna element A(5) and the phase center of the antenna element A(6) included in the sub-array antenna SA(2).Furthermore, the distance between the phase center of the antenna element A(3) and the phase center of the antenna element A(4) included in the sub-array antenna SA(1) is substantially equal to the distance between the phase center of the antenna element A(6) and the phase center of the antenna element A(7) included in the sub-array antenna SA(2). Furthermore, the distance between the phase center of the antenna element A(4) and the phase center of the antenna element A(5) included in the sub-array antenna SA(1) is substantially equal to the distance between the phase center of the antenna element A(7) and the phase center of the antenna element A(8) included in the sub-array antenna SA(2).

[0068] In the second example of the second modification example shown in Fig. 16 can also be achieved by applying the phase center position I r-1from each antenna element A(r) to w as shown in the above equation (9), and converting the matrix V shown in the above equation (8), an electric power estimation process similar to that of the embodiment (see Fig. 10) can be carried out using the generalized inverse matrix V + the matrix V.

[0069] In the second modification using the unequal-pitch linear array antenna described above, the BF method, the MUSIC method, or the like may be used as the arrival direction estimation technique in the target estimation unit 12.

[0070] It should be noted that the above-described embodiment is intended to facilitate understanding of the present disclosure and is not intended to limit the interpretation of the present invention. The present disclosure may be modified / improved without departing from its scope, and the present disclosure also includes equivalents thereof.

[0071] The present disclosure may have the following configurations as described above or instead of the above. (1) An arrival direction estimation device according to an aspect of the present disclosure, comprising: an array antenna having a plurality of antenna elements, respective phase centers of the plurality of antenna elements being arranged in one direction; a target estimation unit that estimates an arrival direction of a radio wave based on a reception signal for each of the antenna elements; an electric power estimation unit that estimates an electric power in the arrival direction for each of a plurality of sub-array antennas each including the same number of the antenna elements; and a target discrimination unit that determines the arrival direction as an arrival direction estimation target when a variation amount of the electric power in the arrival direction estimated for each of the sub-array antennas is equal to or less than a predetermined value.

[0072] With such a configuration, the arrival direction estimation target and false images caused by the side lobes can be distinguished, and the influence of the side lobes, which increases due to the phase shift between the antenna elements, can be suppressed.

[0073] (2) The arrival direction estimation device according to the above (1), wherein the plurality of sub-array antennas have substantially the same distance between the phase center of a first antenna element and the phase center of a second antenna element adjacent in an arrangement direction of the antenna elements.

[0074] (3) The arrival direction estimating apparatus according to the above (2), wherein in the array antenna, the respective phase centers of the plurality of antenna elements are arranged at substantially equal intervals.

[0075] (4) The arrival direction estimation device according to the above (3), wherein the target estimation unit estimates the arrival direction of the radio wave using a cancellation filter method.

[0076] (5) The arrival direction estimation device according to any one of the above (2) to (4), wherein the target estimation unit calculates a phase difference z k between the antenna elements in the direction of arrival (k is an integer from 1 to a total number K of the directions of arrival) and the electric power estimation unit uses the following equations (16) to (21) to calculate an electric power p k (n) in the direction of arrival for each sub-array antenna, if the wavelength of a 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, the received signal for each of the antenna elements included in the sub-array antenna is xn+r-1 is (n is an integer from 1 to N and r is an integer from 1 to R), the phase center position of each of the antenna elements I r-1 , where the phase center position of an antenna element at one end of the sub-array antenna is defined as a reference position, and a complex amplitude for each arrival direction s k (n). Equation 16 wr=2lrλ Equation 17 V=[z1w0z2w0⋯zKw0z1w1z2w1⋯zKw1z1w2z2w2⋱zKw2⋮⋮⋯⋮z1wR−1z2wR−1⋯zKwR−1] Equation 18 Xn=[xnxn+1⋮xn+(R−1)−1xn+(R−1)] Equation 19 Sn=[s1(n)s2(n)⋮sK−1(n)sK(n)] Equation 20 Sn=V+Xn Equation 21 pk(n)=|sk(n)|2

[0077] (6) The arrival direction estimation device according to the above (5), wherein the target discrimination unit uses the following equation (22) to calculate a mean value p av(k) the electrical power p av (k) in the arrival direction for each sub-array antenna using the following equation (23) to calculate a standard deviation p σ (k) the electrical power p av (k) in the arrival direction for each sub-array antenna, and uses the following equation (24) to calculate a variation amount α(k) of the electric power p av (k) in the arrival direction for each subarray antenna. Equation 22 pav(k)=1N∑n=1Npk(n) Equation 23 pσ(k)=1N∑n=1N[pk(n)−pav]2 Equation 24 α(k)=1+pσ(k)pav(k)

[0078] (7) An arrival direction estimation method according to an aspect of the present disclosure, comprising: a target estimation step that estimates an arrival direction of a radio wave based on a reception signal for each of the antenna elements whose respective phase centers are arranged in one direction; an electric power estimation step that estimates an electric power in the arrival direction for each of a plurality of sub-array antennas each including the same number of the antenna elements; and a target determination step that determines the arrival direction as an arrival direction estimation target if a variation amount of the electric power in an arrival direction estimated for each of the sub-array antennas is equal to or less than a predetermined value.

[0079] With such a configuration, the arrival direction estimation target and false images caused by side lobes can be distinguished, and the influence of side lobes, which increases due to the phase shift between the antenna elements, can be suppressed. Furthermore, the arrival direction of radio waves can be appropriately estimated through simple processing.

[0080] (8) The arrival direction estimation method according to the above (7), wherein the plurality of sub-array antennas have substantially the same distance between the phase center of a first antenna element and the phase center of a second antenna element adjacent in an arrangement direction of the antenna elements.

[0081] (9) The arrival direction estimation method according to the above (8), wherein the respective phase centers of the plurality of antenna elements are arranged at substantially equal intervals.

[0082] (10) The arrival direction estimation method according to the above (9), wherein in the target estimation step, the arrival direction of the radio wave is estimated using a cancellation filter method.

[0083] (11) The arrival direction estimation method according to any one of the above (8) to (10), wherein in the target estimation step, a phase difference z k between the antenna elements in the arrival direction is calculated (k is an integer from 1 to a total number K of arrival directions) and in the electric power estimation step, the following equations (25) to (30) are used to calculate an electric power p k(n) in the direction of arrival for each sub-array antenna, if the wavelength of a 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, the received signal for each of the antenna elements included in the sub-array antenna is x n+r-1 is (n is an integer from 1 to N and r is an integer from 1 to R), the phase center position of each of the antenna elements I r-1 where the phase center position of an antenna element at one end of the sub-array antenna is defined as a reference position and a complex amplitude for each arrival direction s k (n). Equation 25 wr=2lrλ Equation 26 V=[z1w0z2w0⋯zKw0z1w1z2w1⋯zKw1z1w2z2w2⋱zKw2⋮⋮⋯⋮z1wR−1z2wR−1⋯zKwR−1] Equation 27 Xn=[xnxn+1⋮xn+(R−1)−1xn+(R−1)] Equation 28 Sn=[s1(n)s2(n)⋮sK−1(n)sK(n)] Equation 29 Sn=V+Xn Equation 30 pk(n)=|sk(n)|2

[0084] (12) The arrival direction estimation method according to the above (11), wherein in the target determination step, the following equation (31) is used to obtain a mean value p av (k) the electrical power p k (n) in the direction of arrival for each sub-array antenna, the following equation (32) is used to calculate a standard deviation p σ (k) the electrical power p k (n) in the arrival direction for each sub-array antenna and the following equation (33) is used to calculate a variation amount α(k) of the electric power p k (n) in the arrival direction for each subarray antenna. Equation 31 pav(k)=1N∑n=1Npk(n) Equation 32 pσ(k)=1N∑n=1N[pk(n)−pav]2 Equation 33 α(k)=1+pσ(k)pav(k)

[0085] According to the present disclosure, it is possible to realize an arrival direction estimation apparatus and an arrival direction estimation method capable of appropriately estimating the arrival direction of radio waves through simple configuration or processing. List of reference symbols 1 Arrival direction estimator 11, 11a, 11b, 111, 112 array antenna 12 Target estimation unit 13 Subarray signal extraction unit 14 Electric power estimation unit 15 Target discrimination unit A(m) antenna element SA(n) subarray antenna QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2019-57791

[0003]

Claims

[1] An arrival direction estimation device having the following features: an array antenna having a plurality of antenna elements, wherein respective phase centers of the plurality of antenna elements are arranged in one direction; a target estimation unit that estimates an arrival direction of a radio wave based on a reception signal for each of the antenna elements; an electric power estimation unit that estimates an electric power in the arrival direction for each of a plurality of sub-array antennas each including the same number of antenna elements; and a target discrimination unit that determines the arrival direction as an arrival direction estimation target when a variation amount of electric power in the arrival direction estimated for each of the sub-array antennas is equal to or less than a predetermined value. [2] The arrival direction estimating apparatus according to claim 1, wherein the plurality of sub-array antennas have substantially the same distance between the phase center of a first antenna element and the phase center of a second antenna element adjacent in an arrangement direction of the antenna elements. [3] The arrival direction estimating apparatus according to claim 2, wherein in the array antenna, the respective phase centers of the plurality of antenna elements are arranged at substantially equal intervals. [4] The arrival direction estimating device according to claim 3, wherein the target estimating unit estimates the arrival direction of the radio wave using an extinction filtering method. [5] The arrival direction estimation device according to any one of claims 2 to 4, wherein the target estimation unit a phase difference z kbetween the antenna elements in the direction of arrival (k is an integer from 1 to a total number K of arrival directions), and the electric power estimation unit uses the following equations (1) to (6) to calculate an electric power p k (n) in the direction of arrival for each sub-array antenna, if the wavelength of a 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, the received signal for each of the antenna elements included in the sub-array antenna is x n+r-1 is (n is an integer from 1 to N and r is an integer from 1 to R), the phase center position of each of the antenna elements I r-1, where the phase center position of an antenna element at one end of the sub-array antenna is defined as a reference position, and a complex amplitude for each arrival direction s k (n). Equation 1 wr=2lrλ Equation 2 V=[z1w0z2w0⋯zKw0z1w1z2w1⋯zKw1z1w2z2w2⋱zKw2⋮⋮⋯⋮z1wR−1z2wR−1⋯zKwR−1] Equation 3 Xn=[xnxn+1⋮xn+(R−1)−1xn+(R−1)] Equation 4 Sn=[s1(n)s2(n)⋮sK−1(n) sK(n)] Equation 5 Sn=V+Xn Equation 6 pk(n)=|sk(n)|2 [6] The arrival direction estimation device according to claim 5, wherein the target discrimination unit uses the following equation (7) to calculate a mean value p av (k) the electrical power p av (k) in the arrival direction for each sub-array antenna using the following equation (8) to calculate a standard deviation p σ(k) the electrical power p av (k) in the arrival direction for each sub-array antenna, and uses the following equation (9) to calculate a variation amount α(k) of the electric power p av (k) in the arrival direction for each subarray antenna. Equation 7 pav(k)=1N∑n=1Npk(n) Equation 8 pσ(k)=1N∑n=1N[pk(n)−pav]2 Equation 9 α(k)=1+pσ(k)pav(k) [7] An arrival direction estimation method comprising the following steps: a target estimation step that estimates an arrival direction of a radio wave based on a reception signal for each of the antenna elements whose respective phase centers are arranged in one direction; an electric power estimation step that estimates an electric power in the arrival direction for each of a plurality of sub-array antennas each including the same number of antenna elements; and a target determination step that determines the arrival direction as an arrival direction estimation target if a variation amount of electric power in an arrival direction estimated for each of the sub-array antennas is equal to or less than a predetermined value. [8] The arrival direction estimation method according to claim 7, wherein the plurality of sub-array antennas have substantially the same distance between the phase center of a first antenna element and the phase center of a second antenna element adjacent in an arrangement direction of the antenna elements. [9] The arrival direction estimation method according to claim 8, wherein the respective phase centers of the plurality of antenna elements are arranged at substantially equal intervals. [10] The arrival direction estimation method according to claim 9, wherein in the target estimation step, the arrival direction of the radio wave is estimated using an extinction filter method. [11] The arrival direction estimation method according to any one of claims 8 to 10, wherein in the target estimation step a phase difference z k between the antenna elements in the direction of arrival (k is an integer from 1 to a total number K of arrival directions) and In the electric power estimation step, the following equations (10) to (15) are used to calculate an electric power p k(n) in the direction of arrival for each sub-array antenna, if the wavelength of a 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, the received signal for each of the antenna elements included in the sub-array antenna is x n+r-1 is (n is an integer from 1 to N and r is an integer from 1 to R), the phase center position of each of the antenna elements I r-1 where the phase center position of an antenna element at one end of the sub-array antenna is defined as a reference position, and a complex amplitude for each arrival direction s k (n). Equation 10 wr=2lrλ Equation 11 V=[z1w0z2w0⋯zKw0z1w1z2w1⋯zKw1z1w2z2w2⋱zKw2⋮⋮⋯⋮z1wR−1z2wR−1⋯zKwR−1] Equation 12 Xn=[xnxn+1⋮xn+(R−1)−1xn+(R−1)] Equation 13 Sn=[s1(n)s2(n)⋮sK−1(n)sK(n)] Equation 14 Sn=V+Xn Equation 15 pk(n)=|sk(n)|2 [12] The arrival direction estimation method according to claim 11, wherein in the target determining step, the following equation (16) is used to calculate a mean value p av (k) the electrical power p k (n) in the direction of arrival for each sub-array antenna, the following equation (17) is used to calculate a standard deviation p σ (k) the electrical power p k (n) in the arrival direction for each sub-array antenna, and the following equation (18) is used to calculate a variation amount α(k) of the electric power p k (n) in the arrival direction for each subarray antenna. Equation 16 wr=2lrλ Equation 17 V=[z1w0z2w0⋯zKw0z1w1z2w1⋯zKw1z1w2z2w2⋱zKw2⋮⋮⋯⋮z1wR−1z2wR−1⋯zKwR−1] Equation 18 Xn=[xnxn+1⋮xn+(R−1)−1xn+(R−1)]

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