Orientation estimation device

Abstract

The present invention provides a direction estimation device that can suppress the decrease in direction estimation accuracy caused by factors such as errors in the position coordinates of antenna elements. [Solution] The direction estimation device 1 comprises a transmitting unit 2, a receiving unit 3 including an array antenna 31 that receives the reflected wave of the transmitted wave from an object, and an estimation unit 52 that estimates the angle of arrival of the reflected wave as the direction of the object. The array antenna has a group of antenna elements including a plurality of first antenna elements and a plurality of second antenna elements arranged at reference intervals in a predetermined one direction. The estimation unit 52 sets two sub-arrays that overlap when the group of antenna elements is translated in one direction. The estimation unit 52 determines the amount of phase rotation that makes the correlation between the first received vector based on the received signal from one sub-array and the second received vector based on the received signal from the other sub-array the strongest when the first received vector based on the received signal from one sub-array is phase-rotated. Then, the estimation unit 52 determines the direction of the object based on the amount of phase rotation and the reference interval.

Description

[Technical Field]

[0001] This disclosure relates to an orientation estimation device that estimates the orientation of an object using radio waves. [Background technology]

[0002] Direction estimation devices utilize array antennas consisting of multiple antenna elements. In array antennas, increasing the antenna aperture length is effective in improving resolution. However, attempting to improve resolution by evenly distributing many antenna elements leads to increased costs and power consumption.

[0003] In contrast, methods for obtaining resolution equivalent to that of a large aperture with a small number of antenna elements arranged at unequal intervals, using MIMO, etc., are disclosed, for example, in Patent Document 1. MIMO is an abbreviation for Multi Input Multi Output. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7023565 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, Patent Document 1 describes a system in which the received signal from an array antenna is processed by digital beamforming (so-called DBF) to convert it into a radar image. In DBF, the position coordinates of all antenna elements constituting the array antenna are required, so manufacturing and mounting errors and variations in the spacing of the antenna elements greatly affect the accuracy of direction estimation.

[0006] This disclosure aims to provide a direction estimation device that can suppress the decrease in direction estimation accuracy due to the influence of errors in the position coordinates of antenna elements, etc. [Means for solving the problem]

[0007] The invention described in claim 1 is, A compass device, A transmitting unit (2) that transmits radio waves of a predetermined frequency as a transmitted wave, A receiving unit (3) includes an array antenna (31) that receives the reflected wave of the transmitted wave from an object, It comprises an estimation unit (52) that estimates the angle of arrival of the reflected wave as the orientation of the object, The array antenna has a group of antenna elements including a plurality of first antenna elements arranged at predetermined reference intervals in a predetermined direction and a plurality of second antenna elements arranged at reference intervals in a predetermined direction at positions different from those of the first antenna elements. The estimation unit sets two sub-arrays in the antenna element group that overlap when translated in one direction, and determines the amount of phase rotation that maximizes the correlation between the first received vector, based on the received signal from one sub-array, and the second received vector, based on the received signal from the other sub-array, when the first received vector, based on the received signal from one sub-array, is phase-rotated. The unit then determines the orientation of the object based on the determined amount of phase rotation and the reference interval.

[0008] In this type of object orientation estimation, positional information indicating the distance between the first and second antenna elements is unnecessary. Therefore, compared to orientation estimation methods like DBF, which require positional information for all antenna elements constituting an array antenna, this method can suppress the decrease in orientation estimation accuracy due to errors in the positional coordinates of the antenna elements.

[0009] The invention described in claim 6 is, A compass device, A transmitting unit (2) that transmits radio waves of a predetermined frequency as a transmitted wave, A receiving unit (3) includes an array antenna (31) that receives the reflected wave of the transmitted wave from an object, It comprises an estimation unit (52) that estimates the angle of arrival of the reflected wave as the orientation of the object, Array antennas are The first antenna element group includes a plurality of first antenna elements arranged at predetermined first reference intervals in a predetermined one direction, and a plurality of second antenna elements arranged at different positions from the first antenna elements at predetermined first reference intervals in a predetermined direction, The second antenna element group includes a plurality of third antenna elements arranged at predetermined second reference intervals in other directions intersecting in one direction, and a plurality of fourth antenna elements arranged at different positions from the third antenna elements at second reference intervals in other directions, The estimation section is, Two sub-arrays that overlap when translated in one direction within an array antenna are set as the first sub-array. The first phase rotation amount is determined as the amount by which the correlation between the first received vector, based on the received signal of one of the first sub-arrays, and the second received vector, based on the received signal of the other first sub-array, is strongest when the first received vector is phase-rotated. The orientation of an object corresponding to one direction is determined based on the determined first phase rotation amount and the first reference interval. Within the array antenna, two sub-arrays that overlap when translated in opposite directions are set as the second sub-array. The phase rotation amount at which the correlation between the third received vector based on the received signal of one of the second sub-arrays and the fourth received vector based on the received signal of the other second sub-array is strongest is determined as the second phase rotation amount. Based on the determined second phase rotation amount and the second reference interval, the orientation of the object corresponding to the other direction is determined.

[0010] Thus, if an array antenna is composed of antenna elements aligned in one direction and antenna elements aligned in a different direction, two-dimensional orientation estimation becomes possible. Furthermore, with the orientation estimation method of this invention, positional information indicating the distance between the first and second antenna elements, and positional information indicating the distance between the third and fourth antenna elements, is not required. Therefore, compared to orientation estimation methods such as DBF, which require positional information for all antenna elements constituting the array antenna, it is possible to suppress the decrease in orientation estimation accuracy due to the influence of errors in the positional coordinates of the antenna elements.

[0011] Note that the reference signs with parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and the specific components etc. described in the embodiments described later.

Brief Description of Drawings

[0012] [Figure 1] It is a schematic configuration diagram of an azimuth estimation device according to the first embodiment. [Figure 2] It is an explanatory diagram for explaining the arrangement mode of the actual antenna elements in the azimuth estimation device according to the first embodiment. [Figure 3] It is an explanatory diagram for explaining the array antenna of the azimuth estimation device according to the first embodiment. [Figure 4] It is an explanatory diagram for explaining the phase of the received signal at each antenna element of the azimuth estimation device according to the first embodiment. [Figure 5] It is a flowchart showing an example of the control process executed by the control unit of the azimuth estimation device according to the first embodiment. [Figure 6] It is an explanatory diagram for explaining the arrangement mode of the actual antenna elements in the azimuth estimation device according to the second embodiment. [Figure 7] It is an explanatory diagram for explaining the phase of the received signal at each antenna element of the azimuth estimation device according to the second embodiment. [Figure 8] It is an explanatory diagram for explaining the arrangement mode of the actual antenna elements in the azimuth estimation device according to the third embodiment. [Figure 9] It is an explanatory diagram for explaining the array antenna of the azimuth estimation device according to the third embodiment. [Figure 10] It is a flowchart showing an example of the control process executed by the control unit of the azimuth estimation device according to the third embodiment. <​​​​​​This is an explanatory diagram illustrating the arrangement of actual antenna elements in the direction estimation device according to the fourth embodiment. [Figure 14] This is an explanatory diagram illustrating the array antenna of the direction estimation device according to the fourth embodiment. [Figure 15] This is an explanatory diagram illustrating an example where the paths of the transmitted and reflected waves coincide. [Figure 16] This is an explanatory diagram illustrating the phase of the received signal at each antenna element in the case of path matching. [Figure 17] This is an explanatory diagram illustrating an example where the paths of the transmitted wave and the reflected wave do not coincide. [Figure 18] This is an explanatory diagram illustrating the phase of the received signal at each antenna element in the case of a mismatch in the signal path. [Figure 19] This is an explanatory diagram illustrating the arrangement of actual antenna elements in the direction estimation device according to the fifth embodiment. [Figure 20] This is an explanatory diagram illustrating the combination of sub-arrays used to estimate the horizontal direction in the direction estimation device according to the fifth embodiment. [Figure 21] This is an explanatory diagram illustrating the combination of sub-arrays used to estimate the vertical direction in the direction estimation device according to the fifth embodiment. [Figure 22] This is an explanatory diagram illustrating the arrangement of actual antenna elements in the direction estimation device according to the sixth embodiment. [Figure 23] This is an explanatory diagram illustrating the combination of sub-arrays used to estimate the horizontal direction in the direction estimation device according to the sixth embodiment. [Figure 24] This is an explanatory diagram illustrating the combination of sub-arrays used to estimate the vertical direction in the direction estimation device according to the sixth embodiment. [Figure 25] This is an explanatory diagram illustrating each sensor of the orientation estimation device according to the seventh embodiment. [Figure 26] This is an explanatory diagram illustrating the arrangement of each sensor in the orientation estimation device according to the seventh embodiment. [Figure 27]This is an explanatory diagram illustrating the combination of sub-arrays used to estimate the horizontal direction in the direction estimation device according to the seventh embodiment. [Figure 28] This is an explanatory diagram illustrating the combination of sub-arrays used to estimate the vertical direction in the direction estimation device according to the seventh embodiment. [Figure 29] This is an explanatory diagram illustrating the arrangement of actual antenna elements in the orientation estimation device according to the eighth embodiment. [Figure 30] This is an explanatory diagram illustrating an example of target placement. [Figure 31] This is an explanatory diagram illustrating the azimuth estimation results obtained by processing the received signal from an array antenna using digital beamforming. [Figure 32] This is an explanatory diagram illustrating the direction estimation result obtained by signal processing of a received signal from an array antenna using the method of this invention. [Figure 33] This is an explanatory diagram illustrating the arrangement of each sensor in the orientation estimation device, which is a modified example of the eighth embodiment. [Modes for carrying out the invention]

[0013] Embodiments of this disclosure will be described below with reference to the drawings. In the following embodiments, parts that are the same as or equivalent to those described in the prior embodiments will be denoted by the same reference numerals, and their descriptions may be omitted. Also, if only a part of a component is described in an embodiment, the components described in the prior embodiments can be applied to the other parts of that component. The following embodiments can be partially combined with each other, even if not explicitly stated, as long as it does not impede the combination.

[0014] (First Embodiment) This embodiment will be described with reference to Figures 1 to 5. In this embodiment, an example will be described in which the direction estimation device 1 of the present disclosure is applied to a radar device mounted on a vehicle that detects various objects present around the vehicle.

[0015] First, to briefly explain radar systems, they emit radio waves forward from a vehicle and receive radio waves reflected by objects in front of the vehicle (i.e., reflected waves) to determine the orientation of objects relative to the vehicle. Specifically, radar systems employ the FMCW (Full-Motion Wave) modulation scheme as the signal modulation method. Radar systems operate at a frequency band corresponding to millimeter waves (for example, 76.5 GHz). However, the operating frequency of radio waves transmitted and received by a radar system is not limited to the millimeter wave frequency; it may also be a frequency other than the millimeter wave.

[0016] The radar system includes an orientation estimation device 1 that estimates the orientation of a target object. As shown in Figure 1, the orientation estimation device 1 comprises a transmitter 2, a receiver 3, and a control unit 5.

[0017] The transmitting unit 2 transmits radio waves of a predetermined frequency as a transmitted wave. The transmitting unit 2 includes a transmitting antenna 21 and a transmitting-side generation unit 22 that generates a signal to be transmitted from the transmitting antenna 21 and transmits it to the transmitting antenna 21. Specifically, the transmitting-side generation unit 22 generates a chirp signal with a continuously changing frequency based on a reference signal output by an oscillator 51 (described later), and provides the generated chirp signal to the transmitting antenna 21.

[0018] The transmitting antenna 21 transmits radio waves corresponding to the chirp signal provided by the transmitting generation unit 22 toward the front of the vehicle. In this example, the transmitting antenna 21 is composed of a single transmitting antenna element Tx, as shown in Figure 2. The transmitting antenna element Tx is positioned with a predetermined horizontal reference interval dh from the receiving antenna element Rx, which will be described later.

[0019] Here, the horizontal reference interval dh is set to satisfy the following equation F1, given that the detection range of the radar device is "±1 / 2·θfov". In this embodiment, θfov is set to "180°", and the horizontal reference interval dh is set to "1 / 2·λ". λ is the wavelength of the radio wave.

[0020] 1 / sin(θfov / 180·π)·2 <dh ···(F1) The receiving unit 3 includes an array antenna 31 that receives the reflected wave of the transmitted wave from an object, and a receiving-side generation unit 32 that transmits the signal received by the array antenna 31 to the control unit 5. The array antenna 31 is a group of antenna elements having a plurality of receiving antenna elements Rx1 to Rx4 that receive the reflected wave reflected by an object. As shown in Figure 2, the array antenna 31 in this example is composed of a plurality of real receiving antenna elements Rx1 to Rx4. The receiving antenna elements Rx are arranged in a line along a predetermined direction with a predetermined interval between them.

[0021] Specifically, the array antenna 31 comprises a plurality of first antenna elements Rx1, Rx2 and a plurality of second antenna elements Rx3, Rx4. The plurality of first antenna elements Rx1, Rx2 are arranged in the horizontal direction Dh with a horizontal reference interval dh. The plurality of second antenna elements Rx3, Rx4 are arranged in the horizontal direction Dh with a horizontal reference interval dh at different positions from the first antenna elements Rx1, Rx2. Furthermore, the array antenna 31 has the first antenna elements Rx2 and the second antenna elements Rx3 spaced apart by a distance of "3dh", which is three times the horizontal reference interval dh. In this embodiment, the horizontal direction Dh corresponds to a "predetermined one direction".

[0022] In the array antenna 31 configured in this way, when the first antenna element Rx1 and the second antenna element Rx3 are moved in parallel in the horizontal direction Dh, the first antenna element Rx2 and the second antenna element Rx4 overlap. The spacing between the first antenna elements Rx1 and Rx2 may be strictly the horizontal reference spacing dh, or it may include an error that is generally acceptable in the art to which the present invention belongs, and does not contradict the spirit of the present invention. The same applies to the spacing between the second antenna elements Rx3 and Rx4, and the spacing between the first antenna element Rx2 and the second antenna element Rx3.

[0023] The receiving-side generation unit 32 generates a beat signal based on a reference signal (so-called local signal) output by the oscillator 51, which will be described later, samples the beat signal, and provides it to the control unit 5. Although not shown, the receiving-side generation unit 32 is composed of a mixer, amplifier, AD converter, etc.

[0024] The control unit 5 includes an oscillator 51 that generates a reference signal used when transmitting a wave and when receiving a reflected wave, and an estimation unit 52 that estimates the angle of arrival of the reflected wave as the orientation of an object.

[0025] The oscillator 51, together with the transmitter 2 and receiver 3, constitutes part of the sensor for object detection. The oscillator 51 may be located alongside either the transmitter 2 or the receiver 3, rather than in the control unit 5.

[0026] The estimation unit 52 is an electronically controlled device centered around a microcomputer equipped with a processor and memory. The memory is, for example, ROM, RAM, etc. The various functions of the microcomputer are realized by the processor executing programs stored in a non-transitional physical storage medium.

[0027] The estimation unit 52 of this embodiment detects a signal corresponding to an object based on the radio waves received when transmitting and receiving radio waves using an array antenna 31 for SIMO that corresponds to an antenna configuration such as a single transmitting antenna element Tx and multiple receiving antenna elements Rx.

[0028] One method for estimating the orientation of an object is to process the received signal from the array antenna 31 using digital beamforming (so-called DBF) to convert it into a radar image or the like. However, DBF requires the position coordinates of all the antenna elements that make up the array antenna 31, so manufacturing and mounting errors and variations in the spacing between the antenna elements greatly affect the accuracy of orientation estimation.

[0029] Taking this into consideration, the inventors investigated ways to suppress the decrease in the accuracy of direction estimation due to the effects of errors in the position coordinates of antenna elements, and devised a method that can achieve this. The method devised by the inventors will be described below.

[0030] In this embodiment, the array antenna 31 has a horizontal reference interval dh between each first antenna element Rx1, Rx2 and between each second antenna element Rx3, Rx4. As shown in Figure 3, when the orientation of the target object (i.e., the angle of arrival of the reflected wave) is "θ", the optical path difference L1 between each first antenna element Rx1, Rx2 is given by the following formula F2.

[0031] L1 = dh * sinθ ... (F2) Similarly, the optical path difference L2 for each of the second antenna elements Rx3 and Rx4 is given by the following formula F2.

[0032] L2 = dh * sinθ ... (F3) Furthermore, when the first antenna element Rx1 and the second antenna element Rx3 are used as the first sub-array, and the first antenna element Rx2 and the second antenna element Rx4 are used as the second sub-array, if one of each sub-array is shifted horizontally in the direction Dh, it will overlap with the other.

[0033] Here, Figure 4 shows the phase of the received signal for each antenna element Rx1 to Rx4 with respect to the first antenna element Rx1 as the reference. The horizontal axis of Figure 4 shows the position coordinates of the antennas in the horizontal direction Dh. In Figure 4, the phase difference between each of the first antenna elements Rx1 and Rx2, and the phase difference between each of the second antenna elements Rx3 and Rx4 are shown as "α". Also in Figure 4, the dotted circle indicates the phase position of the signal when the antenna elements are arranged with a horizontal reference interval dh between the first antenna element Rx2 and the second antenna element Rx3.

[0034] As shown in Figure 4, the phase of the received signal shifts horizontally Dh with a constant inclination corresponding to the orientation θ of the target object. When the received signal vector X1, consisting of the received signals from one sub-array (indicated by the white circle in Figure 4), is phase-rotated and superimposed on the received signal vector X2, consisting of the received signals from the other sub-array (indicated by the black circle in Figure 4), the correlation is strongest at a phase rotation amount corresponding to the phase difference α.

[0035] Therefore, the phase difference α can be detected by determining the amount of phase rotation that results in the strongest correlation when the received signal vector X1 of one sub-array is phase-rotated and superimposed on the received signal vector X2 of the other sub-array. The phase difference α is obtained by multiplying the optical path difference L by the wavenumber (2π / λ), as shown in the following equation F4.

[0036] α = L * 2π / λ ... (F4) Then, by substituting the optical path differences L1 and L2 shown in equations F2 and F3 into equation F4 and rearranging, we obtain an equation that shows the relationship between the object's azimuth θ, phase difference α, and horizontal reference interval dh. Using the equation obtained in this way, the object's azimuth θ can be determined based on the phase difference α and the horizontal reference interval dh. The above is an explanation for the case where there is one target object. When there are multiple target objects, the azimuth of each target can be determined by dividing the received signal into a received signal vector for each target based on the received signal.

[0037] The estimation unit 52 of this embodiment is configured to estimate the orientation of an object based on the method described above. Specifically, the estimation unit 52 determines the amount of phase rotation that results in the strongest correlation when the received signal vector X1 of one subarray is phase-rotated using the ESPRIT method and superimposed on the received signal vector X2 of the other subarray. ESPRIT is an abbreviation for Estimation of Signal Parameter via Rotational Invariance Techniques.

[0038] The mathematical processing in the ESPRIT method is implemented as a program in the estimation unit 52. The mathematical processing in the ESPRIT method is briefly explained below. First, the received signal vector X of the antenna element is represented by the following model equation F5.

[0039] X=[a(θ1),..., a(θt)]s+N=As+N...(F5) In the above-mentioned model equation F5, the array vector is denoted as "a", the complex signal of the radio waves reflected by the object is "s", and the number of target objects is denoted as "t".

[0040] Furthermore, the eigenvalue decomposition of the correlation matrix Rxx is expressed by the following model equations F6 to F10.

[0041] Rxx=E[XX H ]=ASA+σ 2 I ···(F6) S=E[ss H ] ···(F7) RxxE=EΛ ···(F8) Λ = diag[λ1, ..., λ] N ] ···(F9) E=[e1, ..., e N ] ···(F10) In the above formulas F9 and F10, the eigenvalues ​​are denoted as "λ" and the eigenvectors as "e".

[0042] There exists one "T" that satisfies the following mathematical formula F11, where Es is composed of the eigenvectors e of the signal subspace arranged from the correlation matrix Rxx.

[0043] Es = AT ···(F11) As described above, one subarray and the other subarray coincide at a certain phase rotation amount Φ. Therefore, when the matrix for selecting one subarray from A arranged with array vectors a is "J1" and the matrix for selecting the other subarray is "J2", the following mathematical formula F12 holds.

[0044] J1Aφ = J2A ···(F12) Let the eigenvector of one subarray be "Ex" and the eigenvector of the other subarray be "Ey", then the relationships of the following mathematical formulas F13 and F14 hold.

[0045] Ex = J1Es = J1AT = A1ΦT ···(F13) Ey = J2Es = J2AT = A2ΦT ···(F14) Substituting "A" in the mathematical formula F11 into the mathematical formula F12, the following mathematical formula F15 can be obtained.

[0046] J1EsT -1 φ = J2EsT -1 ···(F15) By replacing "Es" in the mathematical formula F15 with "Ex" and "Ey" and arranging, the following mathematical formula F16 is obtained.

[0047] Ey = ExT -1 [[ID=**36**]]φT ···(F16) By obtaining the eigenvalues of "T -1 φT" in the mathematical formula F16, the phase rotation amount Φ corresponding to the orientation of the object serving as the signal source can be obtained.

[0048] Here, the following mathematical formula F17 can be derived from the mathematical formula F6, etc.

[0049] S = T[Λs - σ 2 I]T H ···(F17) Note: There seems to be a formatting issue in the original text where the superscript "T" in formula F16 in the provided text is not properly formatted. I have tried to keep the translation as faithful as possible while assuming it should be a superscript in the mathematical context. If this is incorrect, please provide more accurate formatting information. Also, the numbering in the original text jumps from 36 to 38, which is likely a typo. I have left the numbering as is in the translation.The diagonal elements of matrix S represent the reflected power corresponding to the reflected wave reflected by the target object. The complex signal s of the reflected wave reflected by the object is then obtained from maximum likelihood estimation using the following equations F18A and F18B.

[0050] s = wX ···(F18A) s=TE S H X ···(F18B) In the above formula F18, the weight vector determined for each target is denoted as "w". Then, for each target, the weight vector "w" that enables signal reproduction is given by the following formula F18C. W=TE S H =[w1, ...w L ] ···(F18C)

[0051] As described above, the ESPRIT method can determine the phase rotation amount Φ corresponding to the orientation of the signal source object through matrix operations. In addition, the ESPRIT method can determine the reflected power of the target object and the weight vector w that enables signal reconstruction according to the target. Furthermore, by using eigenvectors as the received signal vector based on the received signal, the phase rotation amount Φ for each target can be determined even when there are multiple target objects. This makes it possible to estimate the orientation of each target even when there are multiple target objects.

[0052] Next, an overview of the direction estimation process performed by the control unit 5 of the direction estimation device 1 will be explained with reference to Figure 5. The process shown in Figure 5 is performed periodically or irregularly by the control unit 5 when a chirp signal is transmitted from the transmission unit 2 at a predetermined transmission cycle.

[0053] In step S100, the control unit 5 receives the reflected wave from the object using the array antenna 31. The received signal is then mixed with a reference signal by the mixer in the receiving unit 3. Subsequently, the desired frequency components are extracted through a low-pass filter or the like, and these frequency components are provided as a beat signal from the receiving unit 3 to the control unit 5.

[0054] Next, in step S110, the control unit 5 performs spatial averaging using the received signals received by each receiving antenna element Rx constituting the array antenna 31. Specifically, the control unit 5 divides each receiving antenna element Rx constituting the array antenna 31 into two sub-arrays and calculates the correlation matrix (i.e., covariance matrix) for each of the two sub-arrays. Then, the control unit 5 calculates a spatially averaged correlation matrix by adding the elements corresponding to the correlation matrices of each sub-array. This spatial averaging process improves the signal-to-noise ratio (S / N) of the signal and restores the rank of the correlation matrix used for estimating the orientation of an object. In this embodiment, since the first antenna elements Rx1 and Rx2 and the second antenna elements Rx3 and Rx4 are symmetrical with respect to the center of the array antenna 31, a forward / backward type (F / B type) spatial averaging can be used.

[0055] Next, in step S120, the control unit 5 estimates the orientation of the object in the horizontal direction Dh using the spatially averaged correlation matrix. In this embodiment, the control unit 5 uses the spatially averaged correlation matrix to perform the object orientation estimation process using the ESPRIT method described above.

[0056] The orientation estimation device 1 described above sets up two sub-arrays that overlap when translated in the horizontal direction Dh. Next, the orientation estimation device 1 determines the amount of phase rotation at which the correlation between the first received vector, based on the received signal from one sub-array, and the second received vector, based on the received signal from the other sub-array, is strongest when the first received vector, based on the received signal from one sub-array, is phase-rotated. Then, the orientation estimation device 1 determines the orientation of the object based on the previously determined amount of phase rotation and the horizontal reference interval dh.

[0057] In this type of object orientation estimation, positional information indicating the spacing between the first antenna elements Rx1 and Rx2 and the second antenna elements Rx3 and Rx4, which are arranged at intervals different from the reference interval dh, is not required. Therefore, compared to orientation estimation that requires positional information for all antenna elements constituting the array antenna 31, such as DBF, it is possible to suppress the decrease in orientation estimation accuracy due to the influence of errors in the positional coordinates of the antenna elements.

[0058] In addition, since this design does not require positional information indicating the distance between the first antenna elements Rx1 and Rx2 and the second antenna elements Rx3 and Rx4, the distance between them can be increased, thereby increasing the antenna aperture length.

[0059] For example, the array antenna 31 of this invention can secure an antenna aperture length of "6dh" by arranging some of the receiving antenna elements Rx1 to Rx4 at unequal intervals.

[0060] Furthermore, the orientation estimation device 1 of this embodiment has the following features. (1) The control unit 5 of this embodiment estimates the orientation of an object using the ESPRIT method. Unlike methods that determine the orientation of an object by searching angular space, the ESPRIT method has the advantage of being able to determine the orientation by calculation.

[0061] (Second Embodiment) Next, a second embodiment will be described with reference to Figures 6 and 7. In this embodiment, the differences from the first embodiment will be mainly described.

[0062] As shown in Figure 6, in this embodiment, the array antenna 31 has a first antenna element Rx2 and a second antenna element Rx3 arranged in the horizontal direction Dh with a spacing of "6dh", which is six times the horizontal reference interval dh. When the first antenna element Rx1 and the second antenna element Rx3 are moved in parallel in the horizontal direction Dh, the array antenna 31 is configured so that they overlap with the first antenna element Rx2 and the second antenna element Rx4.

[0063] Here, Figure 7 shows the phase of the received signal for each antenna element Rx1 to Rx4 with respect to the first antenna element Rx1 as the reference. The horizontal axis of Figure 7 shows the position coordinates of the antennas in the horizontal direction Dh. In Figure 7, the phase difference between each of the first antenna elements Rx1 and Rx2, and the phase difference between each of the second antenna elements Rx3 and Rx4 are shown as "α". Also in Figure 7, the dotted circle indicates the phase position of the signal when the antenna elements are arranged with a horizontal reference interval dh between the first antenna element Rx2 and the second antenna element Rx3.

[0064] As shown in Figure 7, the phase of the received signal shifts horizontally in the Dh direction with a constant inclination corresponding to the orientation θ of the target object. When the received signal vector X1 of one sub-array, indicated by the white circle in Figure 7, is phase-rotated and superimposed on the received signal vector X2 of the other sub-array, indicated by the black circle in Figure 7, the correlation is strongest at the phase rotation amount corresponding to the phase difference α.

[0065] Taking this into consideration, the orientation estimation device 1 of this embodiment detects the phase difference α by determining the amount of phase rotation that results in the strongest correlation when the received signal vector X1 of one sub-array is phase-rotated and superimposed on the received signal vector X2 of the other sub-array.

[0066] Other aspects are the same as in the first embodiment. The orientation estimation device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved from a configuration common to or equivalent to that of the first embodiment.

[0067] Furthermore, the direction estimation device 1 of this embodiment has the following features. (1) In this embodiment, the antenna aperture length of the array antenna 31 is increased compared to the first embodiment, so the resolution of direction estimation can be improved.

[0068] (Modified version of the second embodiment) In the second embodiment, the first antenna element Rx2 and the second antenna element Rx3 are arranged with a spacing of "6dh" in the horizontal direction Dh, which is six times the horizontal reference spacing dh, as an example, but the invention is not limited to this. When considering the resolution of direction estimation, it is desirable that the array antenna 31 has the first antenna element Rx2 and the second antenna element Rx3 arranged with a spacing of 10 times or more the horizontal reference spacing dh in the horizontal direction Dh. Here, since the first antenna elements Rx1 and Rx2 are spaced close together, constructing them as a patch antenna on the same substrate allows their positions to be determined by the etching of the substrate, thus improving manufacturing precision. The same applies to the second antenna elements Rx3 and Rx4. On the other hand, when the first antenna element Rx2 and the second antenna element Rx3 are fabricated on the same substrate, the area between the first antenna element Rx2 and the second antenna element Rx3 becomes wasted space. Alternatively, the first antenna element Rx2 and the second antenna element Rx3 could be fabricated on separate substrates, and the substrate on which the first antenna element Rx2 is mounted could be mechanically fixed to the substrate on which the second antenna element Rx3 is mounted. However, mechanical fixing of substrates to each other is difficult to achieve with high precision, and in direction estimation, such as DBF, where the positional information of all antenna elements constituting the array antenna 31 is required, the accuracy of direction estimation decreases due to the influence of errors in the positional coordinates of the antenna elements. In contrast to these, the direction estimation method of this proposal does not require positional information indicating the distance between the first antenna elements Rx1 and Rx2 and the second antenna elements Rx3 and Rx4. Therefore, it is possible to suppress the decrease in the accuracy of direction estimation due to the effects of errors in the positional coordinates of the antenna elements.

[0069] (Third embodiment) Next, the third embodiment will be described with reference to Figures 8 to 12. In this embodiment, the differences from the first embodiment will be mainly described.

[0070] As shown in Figure 8, the transmitting antenna 21 is composed of four existing transmitting antenna elements Tx1 to Tx4. The four transmitting antenna elements Tx1 to Tx4 are arranged in the vertical direction Dv with a predetermined vertical reference interval dv. The vertical reference interval dv is, for example, half the wavelength of the transmitted wave. In this embodiment, one of the horizontal reference interval dh and the vertical reference interval dv corresponds to the "first reference interval," and the other of the horizontal reference interval dh and the vertical reference interval dv corresponds to the "second reference interval." Also, in this embodiment, the vertical direction Dv corresponds to "another direction intersecting a predetermined one direction."

[0071] The array antenna 31, like the first embodiment, is configured to include four receiving antenna elements Rx1 to Rx4 arranged at predetermined intervals in the horizontal direction Dh. As shown in Figure 9, the array antenna 31 of this embodiment is configured to include multiple transmitting antenna elements Tx1 to Tx4 that constitute the transmitting unit 2 and multiple virtual antenna elements generated by MIMO using multiple existing receiving antenna elements Rx1 to Rx4. In Figure 9, the received signal at each antenna element is denoted as "xij (i → channel index of Tx, j → channel index of Rx)".

[0072] Specifically, the array antenna 31 has a first group of antenna elements, which includes a first antenna element arranged in the horizontal direction Dh with a horizontal reference interval dh, and a second antenna element arranged in the horizontal direction Dh with a horizontal reference interval dh at a different position from the first antenna element. This first group of antenna elements is composed of antenna elements arranged at predetermined intervals in the horizontal direction Dh. The array antenna 31 also has a second group of antenna elements, which includes a third antenna element arranged in the vertical direction Dv with a vertical reference interval dv, and a fourth antenna element arranged in the vertical direction Dv with a vertical reference interval dv at a different position from the third antenna element. This second group of antenna elements is composed of antenna elements arranged at predetermined intervals in the vertical direction Dv.

[0073] The array antenna 31 configured in this way allows two sub-arrays that overlap each other when the antenna is moved in the horizontal direction Dh to be set as the first sub-array. Furthermore, the array antenna 31 allows two sub-arrays that overlap each other when the antenna is moved in the vertical direction Dv to be set as the second sub-array.

[0074] The control unit 5 of this embodiment uses an array antenna 31 composed of antenna elements arranged in both the horizontal direction Dh and the vertical direction Dv to estimate two-dimensional directions such as the direction in the horizontal direction Dh and the direction in the vertical direction Dv. Below, an overview of the direction estimation process performed by the control unit 5 of the direction estimation device 1 of this embodiment will be described with reference to Figure 10. The process shown in Figure 10 is performed periodically or irregularly by the control unit 5 when a chirp signal is transmitted from the transmission unit 2 at a predetermined transmission period.

[0075] In step S100A, the control unit 5 receives the reflected wave reflected by the object with the array antenna 31, and then in step S110A, it performs spatial averaging using the received signals received by each receiving antenna element Rx constituting the array antenna 31. The control unit 5 performs forward-type spatial averaging using the received signals of x2=(x21, ..., x24), x3=(x31, ..., x34), and x4=(x41, ..., x44), which are obtained by translating x1=(x11, ..., x14) constituting the array antenna 31. Furthermore, since the antenna arrangement is symmetrical with respect to the horizontal direction Dh, the effect can be further enhanced by also performing F / B-type spatial averaging as described in the first embodiment.

[0076] Next, in step S120A, the control unit 5 estimates the orientation θi of the object in the horizontal direction Dh using the spatially averaged correlation matrix. Specifically, the control unit 5 selects one of the received signals x1 to x4 that overlap when translated in the horizontal direction Dh to be the signal corresponding to the first first sub-array, and the other to be the signal corresponding to the second first sub-array. Next, the control unit 5 determines the first phase rotation amount, which is the amount by which the correlation between the first received vector based on the received signal corresponding to one of the first sub-arrays and the second received vector based on the received signal corresponding to the other first sub-array is strongest when the first received vector based on the received signal corresponding to one of the first sub-arrays is phase-rotated. Then, the control unit 5 determines the orientation θ of the object in the horizontal direction Dh based on the first phase rotation amount and the horizontal reference interval dh.

[0077] Next, in step S130A, the control unit 5 calculates the weight vector w corresponding to the orientation θ of the object in the horizontal direction Dh. If n orientations θ of the object in the horizontal direction Dh are found, the control unit 5 calculates n weight vectors wi. In "wi", "i" is a variable that takes values ​​from 1 to n.

[0078] Next, in step S140A, the control unit 5 determines whether or not the orientation estimation of all target objects has been completed. If the orientation estimation of all objects has been completed, the control unit 5 exits this process; otherwise, it proceeds to step S150A.

[0079] When the control unit 5 moves to step S150A, it reconstructs the received signals at the antenna elements aligned in the vertical direction Dv based on the weight vector wi obtained in step S130A and the received signals at the antenna elements aligned in the horizontal direction Dh of the array antenna 31. Specifically, as shown in Figure 11, the control unit 5 reconstructs the received signals yi1 to yi4 at the antenna elements aligned in the vertical direction Dv by multiplying the received signals x1 to x4 at the antenna elements aligned in the horizontal direction Dh by the weight vector wi. When the received signal yi1 is used as the reference, the received signals yi2 to yi4 include differences in the position in the vertical direction Dv and phase differences corresponding to the orientation φ of the object.

[0080] Next, in step S160A, the control unit 5 estimates the orientation φ of the object in the vertical direction Dv based on the regenerated received signals yi1 to yi4. Specifically, the control unit 5 selects one of the received signals yi1 to yi4 that overlaps with each other when translated in the vertical direction Dv as the signal corresponding to the first second sub-array, and the other as the signal corresponding to the second second sub-array. Next, the control unit 5 determines the second phase rotation amount, which is the amount of phase rotation that results in the strongest correlation between the third received vector, based on the received signal corresponding to one of the second sub-arrays, and the fourth received vector, based on the received signal corresponding to the other second sub-array, when the third received vector, based on the received signal corresponding to one of the second sub-arrays, is phase-rotated. Then, the control unit 5 determines the orientation φ of the object in the vertical direction Dv based on the second phase rotation amount and the vertical reference interval dv. In this way, similar to the orientation estimation in the horizontal direction Dh, the orientation φ in the vertical direction Dv can be estimated by representing the signals of the two second sub-arrays as vectors and determining the amount of phase rotation that reinforces the interference when rotated in the vertical direction Dv. Furthermore, since the antenna arrangement is symmetrical with respect to the vertical direction Dv, the F / B type spatial averaging described in the first embodiment can also be performed.

[0081] Here, Figure 12 shows an example of the arrangement of target objects, with the target objects lined up in both the horizontal direction Dh and the vertical direction Dv. In Figure 12, the position of the object in the horizontal direction Dh is denoted as "U," and the position of the object in the vertical direction Dv is denoted as "V."

[0082] As shown in Figure 12, since objects tgt1 and tgt2 are aligned in the vertical direction Dv, the direction θ1 corresponding to objects tgt1 and tgt2, and the direction θ2 corresponding to object tgt3 can be determined using the aforementioned direction estimation method for the horizontal direction Dh. Furthermore, the received signals y11~y14, reconstructed by multiplying the signals indicating the direction of objects tgt1 and tgt2 by the weight vector w1, contain the phase information of objects tgt1 and tgt2 in the vertical direction Dv. Therefore, the direction φ1 corresponding to object tgt1 and the direction φ2 corresponding to object tgt2 can be determined using the aforementioned direction estimation method for the vertical direction Dv.

[0083] Other aspects are the same as in the first embodiment. The orientation estimation device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved from a configuration common to or equivalent to that of the first embodiment.

[0084] Furthermore, the orientation estimation device 1 of this embodiment has the following features. (1) The array antenna 31 of this embodiment is composed of antenna elements arranged in the horizontal direction Dh and antenna elements arranged in the vertical direction Dv. This makes it possible to estimate the direction in two dimensions. Furthermore, with the direction estimation of this invention, position information indicating the distance between the first antenna element and the second antenna element, and position information indicating the distance between the third antenna element and the fourth antenna element are not required. For this reason, compared to direction estimation that requires position information for all antenna elements constituting the array antenna 31, such as DBF, it is possible to suppress the decrease in the accuracy of direction estimation due to the influence of errors in the position coordinates of the antenna elements.

[0085] (2) Here, it is possible to perform the direction estimation of the horizontal direction Dh and the direction estimation of the vertical direction Dv separately and independently, but the number of dimensions of the vector becomes four times greater and the number of variables to search doubles, which significantly increases the computational load of the signal processing.

[0086] Taking this into consideration, the control unit 5 of this embodiment is configured to estimate the direction of the vertical direction Dv using the result of the direction estimation in the horizontal direction Dh. Specifically, when determining the first phase rotation amount, the control unit 5 obtains a weight vector w, and based on this weight vector and the received signals of the antenna elements aligned in the vertical direction Dv in the array antenna 31, it reconstructs the received signals of the antenna elements aligned in the vertical direction Dv. Then, the control unit 5 obtains a second phase rotation amount based on the reconstructed received signals, and estimates the direction of the vertical direction Dv based on this second phase rotation amount. By performing direction estimation of the vertical direction Dv using the result of the direction estimation of the horizontal direction Dh in this way, the amount of computation required for signal processing can be reduced.

[0087] (3) The array antenna 31 is configured to include multiple virtual antenna elements generated by MIMO using multiple transmitting antenna elements Tx that constitute the transmitting unit 2 and multiple receiving antenna elements Rx that constitute the receiving unit 3. This makes it possible to increase the antenna aperture length with fewer antenna elements.

[0088] (Modified version of the third embodiment) As in the third embodiment, it is desirable that the direction estimation device 1 uses the result of the direction estimation in the horizontal direction Dh to estimate the direction in the vertical direction Dv, but it is not limited to this. The direction estimation device 1 may perform the direction estimation in the horizontal direction Dh and the direction estimation in the vertical direction Dv separately and independently.

[0089] Furthermore, as in the third embodiment, it is preferable that the array antenna 31 is configured to include multiple virtual antenna elements generated by MIMO, but this is not required.

[0090] (Fourth Embodiment) Next, the fourth embodiment will be described with reference to Figures 13 to 18. In this embodiment, the differences from the first embodiment will be mainly described.

[0091] As shown in Figure 13, the transmitting antenna 21 is composed of two existing transmitting antenna elements Tx1 and Tx2. The two transmitting antenna elements Tx1 and Tx2 are positioned at intervals in the horizontal direction Dh that are integer multiples of the horizontal reference interval dh. The transmitting antenna elements Tx1 and Tx2 are positioned at a distance of the horizontal reference interval dh from the receiving antenna elements Rx1 and Rx4, which will be described later.

[0092] The array antenna 31, like the first embodiment, is configured to include four receiving antenna elements Rx1 to Rx4 arranged at predetermined intervals in the horizontal direction Dh. As shown in Figure 14, the array antenna 31 of this embodiment is configured to include multiple virtual antenna elements generated by MIMO using multiple transmitting antenna elements Tx1 and Tx2 that constitute the transmitting unit 2 and multiple existing receiving antenna elements Rx1 to Rx4. The array antenna 31 configured in this way has the advantage of being able to increase the antenna aperture length with fewer antenna elements.

[0093] Here, as shown in Figure 15, in the case where the path of the transmitted wave and the path of the reflected wave coincide, a phase difference corresponding to the path difference between each transmitting antenna element Tx1 and Tx2 is added. In this case, as shown in Figure 16, the phase difference of the received signal shifts horizontally Dh with a constant slope corresponding to the azimuth θ of the target object. Therefore, the phase difference α can be detected by determining the amount of phase rotation that results in the strongest correlation when the received signal vector of one subarray is phase-rotated and superimposed on the received signal vector of the other subarray.

[0094] On the other hand, as shown in Figure 17, in cases where the path of the transmitted wave and the path of the reflected wave do not coincide, for example, when the orientation of the target object is zero, the phase difference corresponding to the path difference between each transmitting antenna element Tx1 and Tx2 is not added. In this case, as shown in Figure 18, the phase difference of the received signal becomes discontinuous in some places when it shifts in the horizontal direction Dh. This can cause false images in signal processing for orientation estimation, such as DBF.

[0095] In contrast, the control unit 5 of this embodiment sets the subarrays such that, when one subarray is translated in the horizontal direction Dh so that it overlaps with the other subarray, one of the transmitting antenna element Tx and the receiving antenna element Rx is common to the overlapping antenna elements. Specifically, when determining the direction in the horizontal direction Dh, the control unit 5 sets the subarrays such that, when one of the two subarrays is translated in the horizontal direction Dh, the transmitting antenna element Tx is common to the antenna elements that overlap with the other. With this setup, the amount of phase rotation is determined within a range where the phase difference of the received signal is continuous, thus suppressing the influence of discontinuities in the phase difference of the received signal on the direction estimation.

[0096] Other aspects are the same as in the first embodiment. The orientation estimation device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved from a configuration common to or equivalent to that of the first embodiment.

[0097] Furthermore, the orientation estimation device 1 of this embodiment has the following features. (1) The array antenna 31 of this embodiment has an antenna configuration that utilizes MIMO, so the antenna aperture length can be increased with fewer antenna elements. However, in MIMO, if the path of the transmitted wave and the path of the reflected wave do not coincide, a false image indicating a target may be generated in an direction in which there is actually no target object.

[0098] Taking these factors into consideration, in this proposal, when one sub-array is translated in one direction so that it overlaps with the other sub-array, one of the transmitting antenna element Tx and the receiving antenna element Rx is made common for the overlapping antenna elements. This prevents false images due to path mismatches while expanding the antenna aperture length using MIMO.

[0099] (Fifth embodiment) Next, the fifth embodiment will be described with reference to Figures 19 to 21. In this embodiment, the differences from the fourth embodiment will be mainly described.

[0100] As shown in Figure 19, the transmitting antenna 21 is composed of four existing transmitting antenna elements Tx1 to Tx4. Of the four transmitting antenna elements Tx1 to Tx4, two transmitting antenna elements Tx1 and Tx2 are positioned at a horizontal reference interval dh relative to the receiving antenna elements Rx1 and Rx4, which will be described later. The remaining transmitting antenna elements Tx3 and Tx4 are positioned vertically Dv relative to the two transmitting antenna elements Tx1 and Tx2 described above, with a vertical reference interval dv.

[0101] The array antenna 31, similar to the fourth embodiment, is configured to include four receiving antenna elements Rx1 to Rx4 arranged at predetermined intervals in the horizontal direction Dh. As shown in Figures 20 and 21, the array antenna 31 is configured to include four transmitting antenna elements Tx1 to Tx4 that constitute the transmitting unit 2 and a plurality of virtual antenna elements generated by MIMO using the four actual receiving antenna elements Rx1 to Rx4.

[0102] When determining the azimuth in the horizontal direction Dh, the control unit 5 sets the first sub-array so that the transmitting antenna element Tx is common to the antenna elements that overlap with the other sub-array when one of the two first sub-arrays is shifted horizontally in the direction Dh, as shown in Figure 20. Similarly, when determining the azimuth in the vertical direction Dv, the control unit 5 sets the second sub-array so that the receiving antenna element Rx is common to the antenna elements that overlap with the other sub-array when one of the two second sub-arrays is shifted vertically in the direction Dv, as shown in Figure 21.

[0103] If the sub-array is set up in this way, the first and second phase rotation amounts will be determined within a range where the phase difference of the received signal is continuous, thus suppressing the influence of discontinuous phase differences in the received signal on direction estimation.

[0104] Other aspects are the same as in the fourth embodiment. The orientation estimation device 1 of this embodiment can obtain the same effects as in the fourth embodiment, which are achieved from a configuration common to or equivalent to that of the fourth embodiment.

[0105] Furthermore, the orientation estimation device 1 of this embodiment has the following features. (1) In the direction estimation device 1, when one first sub-array is shifted horizontally in the Dh direction so that it overlaps with the other first sub-array, the transmitting antenna element Tx is made common for the overlapping antenna elements. Also, in the direction estimation device 1, when one second sub-array is shifted vertically in the Dv direction so that it overlaps with the other second sub-array, the receiving antenna element Rx is made common for the overlapping antenna elements. This makes it possible to enlarge the antenna aperture length in the horizontal direction Dh using MIMO while preventing false images due to path mismatch.

[0106] (Sixth Embodiment) Next, the sixth embodiment will be described with reference to Figures 22 to 24. In this embodiment, the differences from the fifth embodiment will be mainly described.

[0107] As shown in Figure 22, the transmitting antenna 21 is composed of four existing transmitting antenna elements Tx1 to Tx4. Of the four transmitting antenna elements Tx1 to Tx4, two transmitting antenna elements Tx1 and Tx2 are positioned at a distance of horizontal reference interval dh from the receiving antenna elements Rx1 and Rx4, which will be described later. Specifically, the two transmitting antenna elements Tx1 and Tx2 are positioned with a distance of "4dh + dxh" from each other in the horizontal direction Dh. Also, the two transmitting antenna elements Tx1 and Tx2 are positioned with a distance of "2dv + dxv" from each other in the vertical direction Dv. Note that the distance between the two transmitting antenna elements Tx1 and Tx2 may or may not be an integer multiple of the horizontal reference interval dh or the vertical reference interval dv.

[0108] The remaining two transmitting antenna elements Tx3 and Tx4 are positioned vertically in the vertical direction Dv with a vertical reference spacing dv relative to the two transmitting antenna elements Tx1 and Tx2 described earlier. Specifically, the remaining two transmitting antenna elements Tx3 and Tx4 are positioned horizontally in the horizontal direction Dh with a spacing of "4dh + dxh" between them. Also, the remaining two transmitting antenna elements Tx3 and Tx4 are positioned with a spacing of "dxv" between them. Note that the spacing between the remaining two transmitting antenna elements Tx3 and Tx4 may or may not be an integer multiple of the horizontal reference spacing dh or the vertical reference spacing dv.

[0109] The array antenna 31 is composed of four receiving antenna elements Rx1 to Rx4 arranged at predetermined intervals in the horizontal direction Dh and the vertical direction Dv. Of the four receiving antenna elements Rx1 to Rx4, the first antenna element Rx2 and the second antenna element Rx3 are arranged with a gap of "dxh" in the horizontal direction Dh. In addition, the first antenna element Rx2 and the second antenna element Rx3 are arranged with a gap of "2dv + dxv" in the vertical direction Dv. The spacing between the first antenna element Rx2 and the second antenna element Rx3 may or may not be an integer multiple of the horizontal reference interval dh or the vertical reference interval dv.

[0110] As shown in Figures 23 and 24, the array antenna 31 is composed of multiple virtual antenna elements generated by MIMO using four transmitting antenna elements Tx1 to Tx4 that constitute the transmitting unit 2 and four actual receiving antenna elements Rx1 to Rx4.

[0111] When determining the azimuth in the horizontal direction Dh, the control unit 5 sets the first sub-array so that the transmitting antenna element Tx is common to the antenna elements that overlap with the other when one of the two first sub-arrays is shifted horizontally in the direction Dh, as shown in Figure 23. Similarly, when determining the azimuth in the vertical direction Dv, the control unit 5 sets the second sub-array so that the receiving antenna element Rx is common to the antenna elements that overlap with the other when one of the two second sub-arrays is shifted vertically in the direction Dv, as shown in Figure 24.

[0112] If the sub-array is set up in this way, the first and second phase rotation amounts will be determined within a range where the phase difference of the received signal is continuous, thus suppressing the influence of discontinuous phase differences in the received signal on direction estimation.

[0113] Other aspects are the same as in the fifth embodiment. The orientation estimation device 1 of this embodiment can obtain the same effects as in the fifth embodiment, which are achieved from a configuration common to or equivalent to that of the fifth embodiment.

[0114] Furthermore, the orientation estimation device 1 of this embodiment has the following features. (1) In the direction estimation device 1, when one first sub-array is shifted horizontally in the Dh direction so that it overlaps with the other first sub-array, the transmitting antenna element Tx is made common for the overlapping antenna elements. Also, in the direction estimation device 1, when one second sub-array is shifted vertically in the Dv direction so that it overlaps with the other second sub-array, the receiving antenna element Rx is made common for the overlapping antenna elements. This prevents false images due to path mismatches and allows for expansion of the antenna aperture lengths in both the horizontal Dh and vertical Dv directions using MIMO.

[0115] Here, for example, if “dxh” in Figure 22 is “10dh”, the antenna aperture length in the horizontal direction Dh can be expanded to “24dh”. Also, if “dxv” in Figure 22 is “10dv”, the antenna aperture length in the vertical direction Dv can be expanded to “24dv”. It is desirable that the direction estimation device 1 has the first antenna element and the second antenna element spaced at least 10 times the horizontal reference interval dh in the horizontal direction Dh, and the third antenna element and the fourth antenna element spaced at least 10 times the vertical reference interval dv in the vertical direction Dv.

[0116] (Seventh Embodiment) Next, the seventh embodiment will be described with reference to Figures 25 to 28. In this embodiment, the differences from the sixth embodiment will be mainly described.

[0117] As shown in Figure 25, the orientation estimation device 1 of this embodiment includes a first sensor SD1 and a second sensor SD2 as sensor devices for estimating the orientation of an object. Each sensor SD1 and SD2 is located in a different position. For example, as shown in Figure 26, when the orientation estimation device 1 is applied to a vehicle, each sensor SD1 and SD2 is positioned such that one sensor is located inside the front bumper and the other sensor is located behind the rearview mirror. The first sensor SD1 is equipped with two transmitting antenna elements Tx1 and Tx3 and two receiving antenna elements Rx1 and Rx2, which are positioned biased to one side in the horizontal direction Dh. The first sensor SD1 is also equipped with a first oscillator 51A. The first oscillator 51A is a device that generates a first reference signal Lo1, which is used when transmitting waves from the two transmitting antenna elements Tx1 and Tx3 and when receiving reflected waves from the two receiving antenna elements Rx1 and Rx2.

[0118] The second sensor SD2 is equipped with two transmitting antenna elements Tx2 and Tx4 and two receiving antenna elements Rx3 and Rx4, which are positioned offset to the other side of the horizontal direction Dh. The second sensor SD2 is also equipped with a second oscillator 51B. The second oscillator 51B is a device that generates a second reference signal Lo2, which is used when transmitting waves from the two transmitting antenna elements Tx2 and Tx4 and when receiving reflected waves from the two receiving antenna elements Rx3 and Rx4.

[0119] The azimuth estimation device 1, configured in this way, is divided into a first sensor SD1 and a second sensor SD2, which allows for an enlargement of the antenna aperture length while keeping the overall size of the azimuth estimation device 1 down.

[0120] However, the equipment used to generate the reference signal Lo differs for each sensor, SD1 and SD2. This leads to phase and frequency shifts in the complex signals of the received signals at each sensor, SD1 and SD2, which can cause errors in azimuth estimation.

[0121] Taking this into consideration, the orientation estimation device 1 of this embodiment uses a common reference signal for antenna elements that overlap when one of the two sub-arrays is translated in a predetermined direction so that it overlaps with the other. When estimating the orientation in the horizontal direction Dh, for example, as shown in Figure 27, when one first sub-array is translated in the horizontal direction Dh so that it overlaps with the other first sub-array, a common reference signal is used for antenna elements that overlap with each other. Similarly, when estimating the orientation in the vertical direction Dv, for example, as shown in Figure 28, when one second sub-array is translated in the vertical direction Dv so that it overlaps with the other second sub-array, a common reference signal is used for antenna elements that overlap with each other.

[0122] Other aspects are the same as in the sixth embodiment. The orientation estimation device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved from a configuration common to or equivalent to that of the sixth embodiment.

[0123] Furthermore, the orientation estimation device 1 of this embodiment has the following features. (1) In a configuration in which a reference signal used when transmitting a wave and when receiving a reflected wave is generated by a single oscillator 51, if the antenna aperture length of the array antenna 31 is to be increased, it is necessary to connect distant antenna elements to the same oscillator 51. This is a factor that leads to an increase in the size of the direction estimation device 1.

[0124] In contrast, the direction estimation device 1 of this embodiment is equipped with a plurality of oscillators 51A and 51B that generate reference signals used when transmitting transmitted waves and when receiving reflected waves. This makes it possible to connect nearby antenna elements to one of the oscillators 51A and 51B, and distant antenna elements to the other of the oscillators 51A and 51B. Therefore, it is possible to suppress the increase in size of the direction estimation device 1 caused by the expansion of the antenna aperture length of the array antenna 31.

[0125] In addition, in this design, when one sub-array is shifted in a predetermined direction so that it overlaps with the other sub-array, the overlapping antenna elements share a common reference signal. As a result, even when using multiple oscillators 51A and 51B, direction estimation can be performed using synchronized reference signals.

[0126] (2) Furthermore, multiple oscillators 51A and 51B are mounted on different sensors SD1 and SD2, respectively. When one sub-array is moved in a predetermined direction so that it overlaps with the other sub-array, the overlapping antenna elements use a common reference signal. This makes it possible to maintain the size of each sensor SD1 and SD2 while securing the antenna aperture length of the array antenna 31.

[0127] (3) At least a portion of each sensor SD1 and SD2 is positioned differently from the others. In this way, if a portion of each sensor SD1 and SD2 can be positioned differently from the others, it becomes possible to arrange each sensor SD1 and SD2 in a way that makes them inconspicuous. This contributes to improving the design freedom of the equipment to which the direction estimation device 1 is applied. In this case, if each sensor SD1 and SD2 is mechanically fixed with screws or the like, the positional accuracy of each sensor SD1 and SD2 will deteriorate. Also, the position of each sensor SD1 and SD2 may shift due to vibrations during vehicle operation. In contrast, the direction estimation device 1 of this invention does not require information on the sensor spacing in the horizontal direction Dh and the sensor spacing in the vertical direction Dv for direction estimation, so the positional accuracy of each sensor SD1 and SD2 does not significantly affect the direction estimation accuracy.

[0128] (Variation of the 7th embodiment) As in the seventh embodiment, it is desirable that multiple oscillators 51A and 51B are mounted on different sensors SD1 and SD2, but this is not required. Also, it is desirable that at least a portion of each sensor SD1 and SD2 are located in a different position from the others, but each sensor SD1 and SD2 may be located in the same place.

[0129] In the seventh embodiment, the orientation estimation device 1 is exemplified as being capable of estimating both the horizontal direction Dh and the vertical direction Dv, but the orientation estimation device 1 is not limited to this. For example, the orientation estimation device 1 may be capable of estimating either the horizontal direction Dh or the vertical direction Dv.

[0130] (Eighth embodiment) Next, the eighth embodiment will be described with reference to Figures 29 to 32. In this embodiment, the differences from the seventh embodiment will be mainly described.

[0131] In this embodiment, the array antenna 31 has first and second antenna elements arranged in the horizontal direction Dh at a distance of 10 times or more the horizontal reference interval dh. Specifically, in the array antenna 31, the first and second antenna elements that are separated beyond the horizontal reference interval dh in the horizontal direction Dh are arranged at a distance of 100 times the horizontal reference interval dh (100dh).

[0132] Furthermore, in this embodiment, the array antenna 31 has a third antenna element and a fourth antenna element arranged in the vertical direction Dv that are separated by a distance of 10 times or more the vertical reference interval dv. Specifically, in the array antenna 31, the third antenna element and the fourth antenna element, which are separated by a distance exceeding the vertical reference interval dv in the vertical direction Dv, are spaced at a distance of 100 times the vertical reference interval dv (100dv). Note that the wavelength in millimeter-wave radar is about 4 mm, so "100dh" and "100dv" are about 20 cm.

[0133] The inventors of this invention verified the difference between general DBF-based direction estimation and the direction estimation method of this invention using an array antenna 31 configured as described above. In this verification, it was assumed that an object with a signal strength of "1" exists at a position where U=0 and V=0, as shown in Figure 30.

[0134] Figure 31 shows the two-dimensional spectrum resulting from the direction estimation using DBF. As shown in Figure 31, in direction estimation using DBF, strong signal intensity is distributed over a wide area other than the central region where the object is located. Thus, direction estimation using DBF generates a large number of false images outside the central region where the object is located.

[0135] Figure 32 shows the two-dimensional power distribution resulting from the direction estimation method. As shown in Figure 32, in the direction estimation method, the power is high in the central area where the object is located, while the power is low, at the level of noise, in a wide area outside the central area. Thus, the direction estimation method can appropriately estimate the direction in which the object is located.

[0136] Other aspects are the same as in the seventh embodiment. The orientation estimation device 1 of this embodiment can obtain the same effects as in the seventh embodiment, which are achieved from a configuration common to or equivalent to that of the seventh embodiment.

[0137] Furthermore, the orientation estimation device 1 of this embodiment has the following features. (1) The direction estimation device 1 has a first antenna element and a second antenna element arranged horizontally in the direction Dh at a distance of 10 times or more the horizontal reference interval dh, and a third antenna element and a fourth antenna element arranged vertically in the direction Dv at a distance of 10 times or more the vertical reference interval dv. With this arrangement, the antenna aperture length in both the horizontal direction Dh and the vertical direction Dv can be greatly increased with a small number of antenna elements.

[0138] (Variation of the 8th embodiment) In the orientation estimation device 1 of the eighth embodiment, positional information indicating the distance between the first antenna elements Rx1 and Rx2 mounted on the first sensor SD1 and the second antenna elements Rx3 and Rx4 mounted on the second sensor SD2 is not required for estimating the orientation of an object. Therefore, according to the orientation estimation device 1 of the eighth embodiment, even if each sensor SD1 and SD2 is mounted on different drones (unmanned aerial vehicles), as shown in Figure 33, the orientation of an object can be appropriately estimated.

[0139] As in the eighth embodiment, it is desirable that the first antenna element and the second antenna element of the direction estimation device 1 are arranged horizontally in the direction Dh at a distance of 10 times or more the horizontal reference interval dh, but this is not required. Also, it is desirable that the third antenna element and the fourth antenna element of the direction estimation device 1 are arranged vertically in the direction Dv at a distance of 10 times or more the vertical reference interval dv, but this is not required.

[0140] (Other embodiments) While typical embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above and can be modified in various ways, for example, as follows.

[0141] The orientation estimation device 1 of the above embodiment is configured to perform orientation estimation of an object using the ESPRIT method (i.e., orientation estimation by matrix operation), but is not limited to this. Instead of the ESPRIT method, the orientation estimation device 1 may estimate the orientation of an object using an optimization method such as Bayesian estimation, which is obtained from iterative calculations with rotation as a parameter.

[0142] In the above-described embodiment, an example was given in which the direction Dh in the horizontal direction and the direction Dv in the vertical direction are estimated. However, the direction estimation device 1 may be configured to estimate the direction in a direction different from the horizontal direction Dh and the vertical direction Dv.

[0143] In the embodiments described above, an example was given in which the direction estimation device 1 of this disclosure is applied to a radar device mounted on a moving object such as a vehicle or a drone to detect the direction of various objects present around the moving object. However, the application of the direction estimation device 1 is not limited to this. The direction estimation device 1 can also be applied to other moving objects and stationary equipment, for example, other than vehicles and drones.

[0144] In the embodiments described above, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where they are explicitly stated to be essential or where they are clearly considered essential in principle.

[0145] In the embodiments described above, if numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiment are mentioned, the embodiment is not limited to those specific numbers unless explicitly stated as particularly essential or clearly limited to a specific number in principle.

[0146] In the embodiments described above, when referring to the shape, positional relationships, etc. of the components, the definition is not limited to those shapes, positional relationships, etc., unless otherwise specifically stated or when the definition is fundamentally limited to a particular shape, positional relationship, etc.

[0147] The control unit and its method of this disclosure may be implemented in a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. The control unit and its method of this disclosure may be implemented in a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. The control unit and its method of this disclosure may be implemented in one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. The computer program may also be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium. [Explanation of symbols]

[0148] 1 Orientation estimation device 2. Transmitter 3. Receiving Unit 31 Array Antenna 52 Estimation part

Claims

1. A compass device, A transmitting unit (2) that transmits radio waves of a predetermined frequency as a transmitted wave, A receiving unit (3) includes an array antenna (31) that receives the reflected wave of the transmitted wave from an object, The system includes an estimation unit (52) that estimates the angle of arrival of the reflected wave as the orientation of the object, The array antenna has a group of antenna elements including a plurality of first antenna elements arranged at predetermined reference intervals in a predetermined direction and a plurality of second antenna elements arranged at different positions from the first antenna elements, at predetermined reference intervals in the same direction. The estimation unit sets two sub-arrays in the antenna element group that overlap when translated in one direction, and determines the amount of phase rotation that maximizes the correlation between the first received vector based on the received signal in one sub-array and the second received vector based on the received signal in the other sub-array when the first received vector based on the received signal in one sub-array is phase-rotated, and determines the orientation of the object based on the determined amount of phase rotation and the reference interval, in an orientation estimation device.

2. The array antenna is configured to include a plurality of virtual antenna elements generated by MIMO using a plurality of transmitting antenna elements constituting the transmitting unit and a plurality of receiving antenna elements constituting the receiving unit. The orientation estimation device according to claim 1, wherein when one of the sub-arrays is translated in one direction so as to overlap with the other sub-array, the antenna elements that overlap with each other have one of the transmitting antenna elements and the receiving antenna elements in common.

3. The orientation estimation device according to claim 1, wherein the first antenna element and the second antenna element are arranged in one direction at a distance of 10 times or more the reference interval.

4. The system includes a plurality of oscillators (51) that generate reference signals used when transmitting the transmitted wave and when receiving the reflected wave, The direction estimation device according to claim 1, wherein when one sub-array is translated in one direction so as to overlap with the other sub-array, the antenna elements that overlap with each other share the same reference signal used when transmitting the transmitted wave and when receiving the reflected wave.

5. Multiple oscillators are mounted on different sensors (SD1, SD2), The orientation estimation device according to claim 4, wherein when one of the sub-arrays is translated in one direction so that it overlaps with the other sub-array, the antenna elements that overlap each other use a common reference signal.

6. A compass device, A transmitting unit (2) that transmits radio waves of a predetermined frequency as a transmitted wave, A receiving unit (3) includes an array antenna (31) that receives the reflected wave of the transmitted wave from an object, The system includes an estimation unit (52) that estimates the angle of arrival of the reflected wave as the orientation of the object, The aforementioned array antenna is The first antenna element group includes a plurality of first antenna elements arranged at predetermined first reference intervals in a predetermined one direction, and a plurality of second antenna elements arranged at different positions from the first antenna elements at predetermined first reference intervals in the same direction, The second antenna element group includes a plurality of third antenna elements arranged at predetermined second reference intervals in a direction intersecting the aforementioned one direction, and a plurality of fourth antenna elements arranged at different positions from the third antenna elements at predetermined second reference intervals in the other direction, The estimation unit, Within the array antenna, two sub-arrays that overlap when translated in one direction are set as the first sub-array, and the amount of phase rotation that results in the strongest correlation between the first received vector based on the received signal of one of the first sub-arrays and the second received vector based on the received signal of the other first sub-array is determined as the first phase rotation amount, and the orientation of the object corresponding to the one direction is determined based on the determined first phase rotation amount and the first reference interval. An orientation estimation device that sets two sub-arrays that overlap when translated in the other direction within the array antenna as a second sub-array, determines the amount of phase rotation that results in the strongest correlation between the third received vector based on the received signal of one of the second sub-arrays and the fourth received vector based on the received signal of the other second sub-array when the third received vector based on the received signal of one of the second sub-arrays is phase-rotated, determines the orientation of the object corresponding to the other direction based on the determined second phase rotation amount and the second reference interval.

7. The orientation estimation device according to claim 6, wherein the estimation unit obtains a weight vector when determining the first phase rotation amount, reconstructs the received signals of the antenna elements arranged in the other direction based on the weight vector and the received signals of the antenna elements arranged in the one direction in the array antenna, and determines the second phase rotation amount based on the reconstructed received signals.

8. The array antenna is configured to include a plurality of virtual antenna elements generated by MIMO using a plurality of transmitting antenna elements constituting the transmitting unit and a plurality of receiving antenna elements constituting the receiving unit. When one of the first subarrays is translated in one direction so that it overlaps with the other first subarray, the virtual antenna elements that overlap each other have a common transmitting antenna element and a common receiving antenna element. The orientation estimation device according to claim 6 or 7, wherein when one of the second subarrays is translated in the other direction so as to overlap with the other second subarray, the antenna elements that overlap with each other have one of the transmitting antenna elements and the receiving antenna elements in common.

9. The first antenna element and the second antenna element are arranged in one direction at a distance of 10 times or more the first reference interval. The orientation estimation device according to claim 6 or 7, wherein the third antenna element and the fourth antenna element are arranged at a distance of 10 times or more the second reference interval in the other direction.

10. The system includes a plurality of oscillators (51A, 51B) that generate reference signals used when transmitting the transmitted wave and when receiving the reflected wave, When one of the first subarrays is translated in one direction so that it overlaps with the other first subarray, the antenna elements that overlap each other share the same reference signal used when transmitting the transmitted wave and when receiving the reflected wave. The direction estimation device according to claim 6 or 7, wherein when one of the second subarrays is translated in the other direction so as to overlap with the other second subarray, the antenna elements that overlap with each other share the same reference signal used when transmitting the transmitted wave and when receiving the reflected wave.

11. Multiple oscillators are mounted on different sensors (SD1, SD2), When one of the first subarrays is translated in one direction so that it overlaps with the other first subarray, the antenna elements that overlap each other use a common reference signal. The orientation estimation device according to claim 10, wherein when one of the second subarrays is translated in the other direction so as to overlap with the other second subarray, the antenna elements that overlap each other use a common reference signal.

12. The orientation estimation device according to claim 5 or 11, wherein at least some of the multiple sensors are arranged in positions different from the others.

13. The orientation estimation device according to claim 1 or 6, wherein the estimation unit estimates the orientation of the object using the ESPRIT method.

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