Array antenna and radar equipment

Abstract

To reduce a calculation amount for deciding an element interval.SOLUTION: In array antennas arranged in a point-symmetric manner, a condition 1 and a condition 2 are satisfied. The condition 1: the total of the number of line groups and the number of antenna elements not located on the line group is equal to or greater than the number of observation objects +1 when straight lines included in the first straight line group formed of parallel straight line groups and the second straight line group formed of the parallel straight line groups and intersecting with the straight lines of the first straight line group at the position of the antenna element are distributed to one or more line groups formed of two or more straight lines intersecting with each other at the position of the antenna element. The condition 2: a formula (5) or a formula (6) is satisfied for the greatest common factor Dgcd_U of an interval in the first direction of the antenna elements of the first group and the greatest common factor Dgcd_V of an interval in the second direction of the antenna elements of the first group in all the combinations of grouping when classifying one of the pair of antenna elements arranged at the point-symmetric positions into the first group and classifying the other into the second group.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates to array antennas and radar equipment. [Background technology]

[0002] Patent Document 1 describes a technique for determining the arrangement of elements in an unequal-spacing array antenna to avoid the occurrence of grating lobes, which are undesirable peaks. In the technique disclosed in Patent Document 1, the antenna elements are divided into two groups, and the greatest common divisor of the antenna element spacing between the groups is determined from the greatest common divisor of the antenna element spacing between the two groups. Then, for all combinations of dividing the antenna elements into two groups, the spacing of the antenna elements is determined such that the greatest common divisor obtained for each group does not exceed a predetermined value.

[0003] While the technology disclosed in Patent Document 1 describes the arrangement of antenna elements in a one-dimensional array antenna, it does not mention the arrangement of antenna elements in a two-dimensional array antenna. Therefore, the inventor considered adopting the technology disclosed in Patent Document 1 for a two-dimensional array antenna, taking into account the element spacing in the first direction and the element spacing in the second direction. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-241702 [Overview of the project] [Problems that the invention aims to solve]

[0005] Here, the number of combinations for dividing into two groups depends on the number of antenna elements. When the number of antenna elements is n, the number of combinations is 2 (n-1)The result is -1. For example, if there are 16 antenna elements, the number of combinations is 32,767. However, if there are 32 antenna elements, the number of combinations exceeds 2.1 billion. Furthermore, if there are 64 antenna elements, the number of combinations is 1.8 × 10⁻¹⁰. 19 This exceeds [a certain value]. Thus, as the number of antenna elements increases, the number of combinations becomes enormous, and consequently, the computational complexity also becomes enormous. Therefore, it becomes practically impossible to perform the calculation. [Means for solving the problem]

[0006] This disclosure can be implemented in the following forms:

[0007] According to a first embodiment of the present disclosure, an array antenna is provided. The array antenna (210) includes K antenna elements (K is an even number greater than or equal to 4) arranged in two dimensions, wherein the K antenna elements are arranged point-symmetrically, and the K antenna elements are arranged such that conditions 1 and 2 are satisfied when the number of objects to be observed is (L is 2). Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more antenna elements, and consisting of lines that are inclined with respect to a first direction and a second direction, A second group of lines, which are parallel to each other and have an inclination with respect to the first and second directions, and which are not parallel to the lines of the first group of lines, but which intersect with any of the lines of the first group of lines at the position of the antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more groups of lines, each consisting of two or more lines that intersect each other at the position of the antenna element. For the number of the line groups determined through the above and for one or more antenna elements not located on the lines of the line groups, the sum of the number of the line groups and the number of the one or more antenna elements is (L + 1) or more. Condition 2: When dividing the K antenna elements into two groups by a method of dividing one of a pair of antenna elements arranged symmetrically about the center of point symmetry into a first group and the other of the pair of antenna elements into a second group, in all combinations of grouping, the greatest common divisor of the intervals in the first direction of the antenna elements included in the first group is obtained as the greatest common divisor D gcd_U and the greatest common divisor of the intervals in the second direction of the antenna elements included in the first group is obtained as the greatest common divisor D gcd_V when obtained, at least one of Expression (5) or Expression (6) is satisfied (the wavelength of the received signal is λ, A system capable of detecting the observed object in the horizontal direction. the upper limit of the range is U max , In the aforementioned horizontal direction, the object to be observed can be detected. the lower limit of the range is U min , A system capable of detecting the observed object in the vertical direction. the upper limit of the range is V max , In the aforementioned vertical direction, the object of observation can be detected. the lower limit of the range is V min and is set as such), D gcd_U (U max - U min ) < L·λ ··· (5) D gcd_V (V max - V min ) < L·λ ··· (6)

[0008] According to the above form, the arrangement of the antenna elements in each of the two divided groups is the same. When performing the calculation necessary to determine the interval of the antenna elements, it is only necessary to perform the calculation for the interval of the antenna elements included in one group, and it is not necessary to perform the calculation for the intervals of the antenna elements included in each of the two groups. Therefore, the amount of calculation necessary to determine the interval of the antenna elements can be reduced.

[0009] According to a second embodiment of the present disclosure, an array antenna is provided. This array antenna (210) includes R (R is an even number greater than or equal to 2) receiving antenna elements arranged in two dimensions and T (T is an even number greater than or equal to 2) transmitting antenna elements arranged in two dimensions, and is used as a virtual receiving array antenna composed of R × T virtual antenna elements. The receiving antenna elements are arranged point-symmetrically with respect to the center of the arrangement of the receiving antenna elements, and the transmitting antenna elements are arranged point-symmetrically with respect to the center. When the number of objects to be observed is L (where L is 2), the receiving antenna element and the transmitting antenna element are arranged such that the arrangement of the virtual antenna elements satisfies conditions 1 and 2. Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more of the aforementioned virtual antenna elements, and consisting of lines that are inclined with respect to the first and second directions, A second group of lines, each consisting of parallel lines having an inclination with respect to the first and second directions, which are not parallel to the lines of the first group of lines, and which intersect any of the lines of the first group of lines at the position of the virtual antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most virtual antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more line groups, each consisting of two or more lines that intersect each other at the position of the virtual antenna element. The number of the line groups and one or more of the virtual antenna elements not located on the lines of the line groups are determined through the process, The sum of the number of the wire groups and the number of the one or more virtual antenna elements is (L+1) or greater. Condition 2: When dividing the R × T virtual antenna elements into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the receiving antenna element, into two groups, And, In the case where R × T virtual antenna elements are divided into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the transmitting antenna element, into two groups, In all combinations of grouping, The greatest common divisor of the spacing between the virtual antenna elements included in the first group in the first direction is the greatest common divisor D. gcd_U The greatest common divisor D is the greatest common divisor of the spacing between the virtual antenna elements in the second direction that are included in the first group. gcd_V When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where the wavelength of the received signal is λ, A system capable of detecting the observed object in the horizontal direction. Set the upper limit of the range to U max , In the aforementioned horizontal direction, the object to be observed can be detected. Lower limit of range U min , A system capable of detecting the observed object in the vertical direction. Set the upper limit of the range to V max , In the aforementioned vertical direction, the object of observation can be detected. The lower limit of the range is V min (Assume). D gcd_U (U max -U min ) <L·λ···(5) D gcd_V (V max -V min ) <L·λ···(6)

[0010] According to the above configuration, when the virtually arranged antenna elements are divided into two groups, the arrangement of antenna elements in each group will be the same. When performing the calculations necessary to determine the spacing of the antenna elements, it is only necessary to calculate the spacing of the antenna elements in one group, and it is not necessary to calculate the spacing of the antenna elements in each of the two groups. Therefore, the amount of computation required to determine the spacing of the antenna elements can be reduced.

[0011] A third embodiment of this disclosure provides a radar device (1). This radar device includes a transmitting antenna (140) that transmits a transmission signal, a receiving antenna (210) which is an array antenna including K antenna elements (K is an even number of 4 or more) arranged in two dimensions, wherein the K antenna elements are arranged point-symmetrically, a mixer (230) that mixes the received signal received by the K antenna elements with the transmission signal to obtain a beat signal, an A / D converter (250) that samples the beat signal at a preset sampling frequency to obtain received data for multiple channels corresponding to the K antenna elements, and an orientation detection unit (320) that detects the distance to an object and the direction in which the object is located based on the received data. When the number of objects to be observed is L (where L is 2), the K antenna elements are arranged such that conditions 1 and 2 are satisfied. Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more antenna elements, and consisting of lines that are inclined with respect to a first direction and a second direction, A second group of lines, which are parallel to each other and have an inclination with respect to the first and second directions, and which are not parallel to the lines of the first group of lines, but which intersect with any of the lines of the first group of lines at the position of the antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more groups of lines, each consisting of two or more lines that intersect each other at the position of the antenna element. The number of the line groups and one or more antenna elements not located on the lines of the line groups are determined through the process described above. The sum of the number of the aforementioned wire groups and the number of the aforementioned one or more antenna elements is (L+1) or greater. Condition 2: When dividing the K antenna elements into two groups by dividing one of a pair of antenna elements, which are positioned point-symmetrically with respect to a point-symmetric center, into a first group and the other of the pair of antenna elements into a second group, in all combinations of grouping, The greatest common divisor D is the greatest common divisor of the spacing between the antenna elements included in the first group in the first direction. gcd_U The greatest common divisor D is calculated as the spacing between the antenna elements in the first group in the second direction. gcd_V When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where the wavelength of the received signal is λ, A system capable of detecting the observed object in the horizontal direction. Set the upper limit of the range to U max , In the aforementioned horizontal direction, the object to be observed can be detected. Lower limit of range U min , A system capable of detecting the observed object in the vertical direction. Set the upper limit of the range to V max , In the aforementioned vertical direction, the object of observation can be detected. The lower limit of the range is V min (Assuming), D gcd_U (U max -U min ) <L·λ···(5) D gcd_V (V max -V min ) <L·λ···(6)

[0012] In the above configuration, the arrangement of antenna elements is the same in each of the two divided groups. When performing the calculations necessary to determine the spacing of the antenna elements, it is only necessary to calculate the spacing of the antenna elements in one group, and it is not necessary to calculate the spacing of the antenna elements in each of the two groups. Therefore, the amount of computation required to determine the spacing of the antenna elements can be reduced.

[0013] A fourth embodiment of this disclosure provides a radar device (1). This radar device includes an array antenna used as a virtual receiving array antenna composed of R × T virtual antenna elements, which include R (R is an even number of 2 or more) receiving antenna elements arranged in two dimensions and T (T is an even number of 2 or more) transmitting antenna elements arranged in two dimensions; a mixer (230) that mixes a received signal and a transmitted signal to obtain a beat signal; an A / D converter (250) that samples the beat signal at a preset sampling frequency to obtain received data for multiple channels corresponding to the virtual antenna elements; and an orientation detection unit (320) that detects the distance to an object and the direction in which the object is located based on the received data. The receiving antenna elements are arranged point-symmetrically with respect to the center of the arrangement of the receiving antenna elements, and the transmitting antenna elements are arranged point-symmetrically with respect to the center. When the number of objects to be observed is L (where L is 2), the receiving antenna element and the transmitting antenna element are arranged such that the arrangement of the virtual antenna elements satisfies conditions 1 and 2. Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more of the aforementioned virtual antenna elements, and consisting of lines that are inclined with respect to the first and second directions, A second group of lines, each consisting of parallel lines having an inclination with respect to the first and second directions, which are not parallel to the lines of the first group of lines, and which intersect any of the lines of the first group of lines at the position of the virtual antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most virtual antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more line groups, each consisting of two or more lines that intersect each other at the position of the virtual antenna element. The number of the line groups and one or more of the virtual antenna elements not located on the lines of the line groups are determined through the process, The sum of the number of the wire groups and the number of the one or more virtual antenna elements is (L+1) or greater. Condition 2: When dividing the R × T virtual antenna elements into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the receiving antenna element, into two groups, And, In the case where R × T virtual antenna elements are divided into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the transmitting antenna element, into two groups, In all combinations of grouping, The greatest common divisor of the spacing between the virtual antenna elements included in the first group in the first direction is the greatest common divisor D. gcd_U The greatest common divisor D is the greatest common divisor of the spacing between the virtual antenna elements in the second direction that are included in the first group. gcd_V When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where the wavelength of the received signal is λ, A system capable of detecting the observed object in the horizontal direction. Set the upper limit of the range to U max , In the aforementioned horizontal direction, the object to be observed can be detected. Lower limit of range U min , A system capable of detecting the observed object in the vertical direction. Set the upper limit of the range to V max , In the aforementioned vertical direction, the object of observation can be detected. The lower limit of the range is V min (Assume). D gcd_U (U max -U min ) <L·λ···(5) D gcd_V (V max -V min ) <L·λ···(6)

[0014] According to the above configuration, when the virtually arranged antenna elements are divided into two groups, the arrangement of antenna elements in each group will be the same. When performing the calculations necessary to determine the spacing of the antenna elements, it is only necessary to calculate the spacing of the antenna elements in one group, and it is not necessary to calculate the spacing of the antenna elements in each of the two groups. Therefore, the amount of computation required to determine the spacing of the antenna elements can be reduced. [Brief explanation of the drawing]

[0015] [Figure 1] This diagram shows the relative positions of a vehicle equipped with radar equipment and other vehicles. [Figure 2] This is a block diagram illustrating the schematic configuration of a radar system. [Figure 3] This diagram illustrates the path difference of the signals received by the antenna elements. [Figure 4] This diagram shows an example of the positional relationship between the object being observed and the antenna elements. [Figure 5] This figure shows an example of antenna elements arranged symmetrically. [Figure 6] This figure shows an example of an antenna element arrangement that satisfies the conditions. [Figure 7] This figure shows an example of a different grouping method in the same arrangement as in Figure 6. [Figure 8] This figure shows the spectrum in the configuration shown in Figure 6. [Figure 9] This figure shows an example of the arrangement of transmitting and receiving antenna elements. [Figure 10] This figure shows an example of virtual antenna element placement using MIMO. [Figure 11] This figure shows the spectrum when MIMO is used in the array antenna configuration shown in Figure 9. [Figure 12] This figure shows an example of the arrangement of transmitting and receiving antenna elements. [Modes for carrying out the invention]

[0016] A. Embodiment A1. Overview of Radar Equipment As shown in Figure 1, the radar device 1 according to this embodiment is an in-vehicle radar mounted on the vehicle M1. The radar device 1 is installed, for example, in the front grille of the vehicle M1. The radar device 1 detects the distance to another vehicle M2, which is an observation target located in front of the vehicle M1, the bearing of the other vehicle M2, and the relative speed of the other vehicle M2 with respect to the vehicle M1. The detection results of the radar device 1 are used to inform the driver about the surrounding environment while driving. Specifically, the radar device 1 emits radio waves as a transmitted wave IL. The transmitted wave is a millimeter wave. The transmitted wave IL is reflected by an observation target outside the vehicle M1, such as the other vehicle M2, and becomes a reflected wave RL. The radar device 1 estimates the distance to the observation target from the delay time obtained from the transmission time of the transmitted wave IL and the reception time of the reflected wave RL. The radar device 1 also estimates the relative speed of the observation target from the Doppler shift amount of the reflected wave RL with respect to the transmitted wave IL.

[0017] Furthermore, the radar device 1 estimates the direction of the observed object by utilizing the fact that a phase difference occurs in the reflected wave RL received by each antenna element of the receiving antenna, depending on the direction of arrival. As a calculation algorithm for estimating the direction with high accuracy and high resolution, there is, for example, MUSIC (Multiple Signal Classification).

[0018] The azimuth estimation algorithm is used in combination with an array antenna. To improve the azimuth resolution of multiple observation targets, the aperture area of ​​the antenna should be increased. Array antennas include equally spaced array antennas, where multiple antenna elements are arranged at equal intervals, and unequally spaced array antennas, where multiple antenna elements are arranged at unequal intervals. In equally spaced array antennas, the spacing between antenna elements needs to be reduced to suppress the occurrence of grating lobes. For example, in an equally spaced antenna, reducing the spacing between antenna elements and increasing the aperture area of ​​the antenna increases the number of antenna elements. Therefore, it has been proposed to use an unequally spaced array antenna to reduce the number of antenna elements in order to suppress the occurrence of grating lobes.

[0019] As shown in Figure 2, the radar device 1 comprises a transmitting unit 100, a receiving unit 200, and a processing unit 300. In this embodiment, the radar device 1 is an FMCW (Frequency Modulated Continuous Wave) radar.

[0020] The transmitting unit 100 comprises an oscillator 110, an amplifier 120, a distributor 130, and a transmitting antenna 140. The oscillator 110 is, for example, a voltage-controlled oscillator (VCO). When a triangular wave voltage signal is input to the oscillator 110 from the transmit / receive control unit 330 of the processing unit 300, the oscillator 110 outputs a transmission signal, which is a frequency-modulated high-frequency signal, to the amplifier 120. The amplifier 120 amplifies the transmission signal and outputs the amplified signal to the distributor 130. The distributor 130 distributes the amplified transmission signal to the transmitting antenna 140 and the mixer 230 of the receiving unit 200. A portion of the transmission signal distributed to the mixer 230 is used for detection of the received signal. The transmitting antenna 140 radiates the transmission signal supplied via the distributor 130 as radio waves to the outside of the vehicle M1.

[0021] The receiving unit 200 comprises an array antenna 210, an amplifier 220, a mixer 230, a low-pass filter 240, and an A / D (Analog Digital) converter 250. The array antenna 210 is a two-dimensional array antenna. The array antenna 210 is an unequal-spacing array antenna in which K antenna elements are arranged at unequal intervals on a plane. K is an even number greater than or equal to 4. The K antenna elements correspond to each channel from the 1st channel to the Kth channel. The array antenna 210 receives the reflected wave reflected from the object being observed as a received signal and outputs the received signal to the amplifier 220.

[0022] Furthermore, in this embodiment, the K antenna elements are arranged in a point-symmetrical manner. The reason for this point-symmetrical arrangement will be explained later.

[0023] The amplifier 220 amplifies the received signal and outputs the amplified signal to the mixer 230. The mixer 230 mixes the distributed transmitted signal and the received signal to generate a beat signal for phase detection. Phase detection is the process of extracting amplitude and phase information from the received signal. The beat signal output by the mixer 230 is supplied to the A / D converter 250 via a low-pass filter 240 that cuts out high-frequency noise. The A / D converter 250 converts the beat signal into a digital signal by sampling and quantizing it at the sampling frequency. The converted digital signal is supplied to the processing unit 300.

[0024] The processing unit 300 comprises a frequency processing unit 310, an orientation detection unit 320, and a transmission / reception control unit 330. The processing unit 300 is composed of a computer including a CPU (Central Processing Unit), memory, etc. The frequency processing unit 310 calculates zero or more beat frequencies from the supplied digital signal. The orientation detection unit 320 estimates the orientation of the observed object using MUSIC or the like for each calculated beat frequency. The transmission / reception control unit 330 controls the transmission unit 100 and the reception unit 200.

[0025] A2. Regarding the occurrence of grating groves As shown in Figure 3, assume that reflected waves are incident on antenna elements A0 and A1 at the same angle Φ. If we use the reflected wave signal received by antenna element A0 as the reference, the signal received by antenna element A1 will be out of phase by a path difference Δd. That is, a phase difference corresponding to the path difference Δd occurs between the signal received by antenna element A0 and the signal received by antenna element A1.

[0026] When the phase difference between the received signal of antenna element A0 and the received signal of antenna element A1 is an integer multiple of the wavelength λ, which is the wavelength of the signal received by radar device 1, the received signal of antenna element A0 and the received signal of antenna element A1 are said to be in phase. When the received signals of multiple antenna elements are in phase, in high-resolution techniques known as subspace techniques such as MUSIC, the received signals of multiple antenna elements are treated as a single signal.

[0027] For example, suppose an array antenna 210 has six antenna elements, and three of the six antenna elements are divided into group 1 and the remaining three into group 2. Suppose the received signals of the three antenna elements belonging to group 1 are in the same phase, and the received signals of the three antenna elements belonging to group 2 are in the same phase. In this case, the three antenna elements belonging to group 1 become equivalent antenna elements. The three antenna elements belonging to group 2 also become equivalent antenna elements.

[0028] In this case, the number of signals that can be separated and received by the array antenna 210 is effectively two. In this case, the size of the correlation matrix obtained from the received signals is a 2x2 matrix, and the maximum number of eigenvectors obtained from the correlation matrix is ​​two. When there are two eigenvectors, the space spanned by the eigenvectors is two-dimensional. In this situation, if there are arriving waves from two observation targets, and furthermore, there is an direction in which no observation target exists but satisfies the conditions, the direction vector for the direction in which no observation target exists is not independent, but is linearly dependent on the respective direction vectors representing the two observation targets. Direction vectors are also called mode vectors or steering vectors. The radar device 1 mounted on the vehicle is required to separate and detect at least two signal sources. A signal source is an observation target from which radio waves are reflected. Here, since there are two observation targets, the antenna elements included in the array antenna 210 are divided into two groups. The number of groups is selected according to the number of arriving waves. Generally, when there are L objects to observe, the antenna elements contained in the array antenna 210 need to be divided into L groups. L is a positive integer.

[0029] Direction estimation using subspace methods such as MUSIC involves obtaining noise vectors from the eigenvectors of the correlation matrix of the array antenna 210's output, and then using the property that the noise subspace spanned by the noise vectors is orthogonal to the signal subspace to determine the direction of the incoming wave. If the direction vector indicating the direction of the incoming wave from the observed object and the direction vector indicating the direction where the observed object does not exist are linearly dependent, then the direction vector indicating the direction where the observed object does not exist is also orthogonal to the noise vector. For this reason, when performing direction estimation using high-resolution methods known as subspace methods such as MUSIC, a grating lobe indicating a direction different from the actual observed object may occur, depending on the spacing of the antenna elements and the conditions of the incoming wave's direction of arrival. As a result, the direction where the observed object does not exist is incorrectly estimated as the direction of the incoming wave.

[0030] As shown in Figure 4, the positional relationship between the observation target T1, the observation point P1 where the observation target T1 is observed, and the antenna elements A0 to A5 is represented in a Cartesian coordinate system. The origin where the X, Y, and Z axes intersect is defined as observation point P1. In this embodiment, the X-axis direction is also called the U-axis direction, and the Y-axis direction is also called the V-axis direction. The antenna elements A0 to A5 are arranged at unequal intervals in the U-axis and V-axis directions.

[0031] For example, the distance between two antenna elements in the U-axis direction is the distance between a point on the U-axis representing the position of one antenna element when that antenna element is projected onto the U-axis, and a point on the U-axis representing the position of the other antenna element when that antenna element is projected onto the U-axis. The distance between two antenna elements in the V-axis direction is the distance between a point on the V-axis representing the position of one antenna element when that antenna element is projected onto the V-axis, and a point on the V-axis representing the position of the other antenna element when that antenna element is projected onto the V-axis. In this embodiment, multiple antenna elements are said to be arranged at unequal intervals, meaning that the antenna elements are arranged such that the distance between them in the U-axis direction is unequal, and the distance between them in the V-axis direction is unequal. As shown in Figure 4, the directions indicated by the X-axis, Y-axis, and Z-axis are mutually orthogonal. Here, orthogonal means that the angle that one direction makes with another direction is within the range of plus or minus 10 degrees from a right angle. The U-axis direction is also called the first direction. The V-axis direction is also called the second direction.

[0032] If the direction of the observed object T1 is represented by a unit vector, then the direction t of the observed object T1 is t = (U t ,V t ,√(1-U t 2 -V t 2 It is expressed as ). The detectable range on the U-axis of radar device 1 is -1 t <+1. The detectable range on the V-axis of radar device 1 is -1≦V t The limit is +1.

[0033] ​ Furthermore, when there are two antenna elements, the two antenna elements are aligned on a straight line, so the path difference Δd of the received signal can be expressed by the following equation (1). In equation (1), D u D is the spacing between the antenna elements in the U-axis direction. v This is the spacing between the antenna elements in the V-axis direction. Δd=D u ·U t +D v ·V t ...(1)

[0034] In the case of three or more antenna elements, the multiple antenna elements are not necessarily aligned in a straight line. Therefore, in order to adjust the phase difference between antenna elements, the spacing between antenna elements in a two-dimensional array antenna needs to be considered in both the U-axis direction and the V-axis direction. Accordingly, in this embodiment, Δd = n·λ is assumed to hold when (a) and (b) below are satisfied, or when (c) is satisfied. n1 is an integer other than zero. n2 is an integer including zero. (a)D u ·U t =n1·λ (b)D v ·V t =n1·λ (c)D u ·U t +D v ·V t =n²·λ

[0035] A3. Antenna element placement conditions First, we will explain an example where the received signals of multiple antenna elements have the same phase, in the antenna element arrangement shown in Figure 4. First, we will explain A0, A1, and A3. In the following explanation, the basic unit representing the distance between elements is d. d = λ / 2, where λ is the wavelength of the received signal. Hereafter, antenna element A0 may be simply referred to as A0. The same applies to antenna elements A1 to A5.

[0036] The distance between A0 and A1 in the U-axis direction is 2d, and the distance in the V-axis direction is 2d. U t = 1 / 2, V t = 1 / 2, when D u ·U t = λ / 2, D v ·V t = λ / 2. Therefore, D u ·U t + D v ·V t = λ. U t = 1 / 2, V t = 1 / 2, as represented by the above formula (c), the path difference Δd between A0 and A1 is an integer multiple of the wavelength λ, so the received signals of A0 and A1 have the same phase. The distance between A0 and A3 in the U-axis direction is 4d, and the distance in the V-axis direction is 4d. U t = 1 / 2, V t = 1 / 2, when D u ·U t = λ, D v ·V t = λ. Therefore, D u ·U t + D v ·V t = 2λ. U t = 1 / 2, V t = 1 / 2, the path difference Δd between A0 and A3 is an integer multiple of the wavelength λ, so the received signals of A0 and A3 have the same phase. The distance between A1 and A3 in the U-axis direction is 2d, and the distance in the V-axis direction is 2d, so D u ·U t = λ / 2, D v ·V t = λ / 2. Therefore, D u ·U t + D v ·V t = λ. U t = 1 / 2, V t = 1 / 2, the path difference Δd between A1 and A3 is an integer multiple of the wavelength λ, so the received signals of A1 and A3 have the same phase.

[0037] Thus, U t = 1 / 2, Vt When = 1 / 2, the path difference Δd between A0, A1, and A3 is an integer multiple of the wavelength λ, so the received signals of A0, A1, and A2 are in phase. Therefore, the three antenna elements A0, A1, and A3 can be said to be equivalent antenna elements.

[0038] Furthermore, we will explain another example where the received signals of multiple antenna elements have the same phase in the antenna element arrangement shown in Figure 4. Below, we will explain A0, A1, and A2. The distance between A0 and A1 in the U-axis direction is 2d, and the distance in the V-axis direction is 2d, so U t =1, V t When = 1, D u ·U t =λ, D v ·V t =λ. As shown in equations (a) and (b) above, the path difference Δd between A0 and A1 is an integer multiple of the wavelength λ, so the received signal at A0 and the received signal at A1 are in phase. The distance between A0 and A2 in the U-axis direction is 6d, and the distance in the V-axis direction is 4d, so U t =1, V t When = 1, D u ·U t =3λ, D v ·V t = 2λ. The received signal of A0 and the received signal of A2 are in phase. The distance between A1 and A2 in the U-axis direction is 4d, and the distance in the V-axis direction is 2d, so U t =1, V t When = 1, D u ·U t =2λ, D v ·V t =λ. The received signal from A1 and the received signal from A2 are in phase.

[0039] Thus, U t =1, V t When = 1, the path difference Δd between A0, A1, and A2 is an integer multiple of the wavelength λ, and the received signals of A0, A1, and A2 are in phase. Therefore, the three antenna elements A0, A1, and A2 can be said to be equivalent antenna elements.

[0040] As mentioned above, in the arrangement of antenna elements shown in Figure 4, U t = 1 / 2, V t When = 1 / 2, A0, A1, and A3 have the same phase. Also, A0, A1, and A3 are arranged so as to lie on the same straight line. In this way, the received signals of multiple antenna elements arranged on the same straight line may have the same phase depending on the spacing between the antenna elements and the direction of arrival of the incoming wave. Assume that this straight line has an arbitrary slope K. In this case, D v =K·D u It can be expressed as follows. By rearranging equation (1), the path difference Δd for A0, A1, and A3 can be expressed as shown in equation (2) below. Δd=D u ·U t +K·D U ·V t ...(2)

[0041] Furthermore, in cases where the antenna elements can be connected by a straight line, such as A0, A1, and A3, the absolute value of n when Δd=n·λ holds is smaller compared to cases where the antenna elements cannot be connected by a straight line, such as A0, A1, and A2. In other words, when the antenna elements can be connected by a straight line, U is smaller compared to cases where the antenna elements cannot be connected by a straight line. t The value and V t The values ​​of and take small values. This means that when antenna elements can be connected by a straight line, the detection range in which grating lobes do not occur is narrower compared to when they cannot be connected by a straight line. Therefore, it is preferable that not all antenna elements belonging to the same group are located on the same straight line.

[0042] As mentioned above, the radar device 1 mounted on the vehicle is required to detect at least two signal sources separately. Therefore, the radar device 1 needs to detect at least two objects to be observed. First, let's consider the case where there are two objects to be observed. In the antenna arrangement shown in Figure 4, for example, A1 and A3 are group 1, and A4 and A5 are group 2. In this case, antenna elements A0 and A2 are not used.

[0043] Let A1 and A3, which belong to Group 1, be connected by a straight line, and let the slope of that line be K1. In the antenna arrangement shown in Figure 4, K1 = V / U = 1. The spacing of the antenna elements in the U-axis direction is given by D in equation (2). u Substitute it into the variable. Δd=D u ·U t +K1·D U ·V t =2d·U t +2d·V t ...(3)

[0044] Let A4 and A5, which belong to Group 2, be connected by a straight line, and let the slope of that line be K2. K2 = V / U = -2 / 3. The spacing of the antenna elements in the U-axis direction is given by D in equation (3). u Substitute it into the variable. Δd=D u ·U t +K2·D U ·V t =3d·U t +(-2 / 3)·3d·V t ...(4)

[0045] Here, U t =2 / 5, V tWhen = 3 / 5, in equation (3), Δd = λ, and Δd takes an integer multiple of the wavelength λ. In this case, the received signal of A1 and the received signal of A3, which belong to group 1, have the same phase. Also, in equation (4), Δd = 0, and Δd takes an integer multiple of the wavelength λ. In this case, the received signal of A4 and the received signal of A5, which belong to group 2, have the same phase. Furthermore, since both the Δd shown in equation (3) and the Δd shown in equation (4) take an integer multiple of the wavelength λ, the received signals of A1 and A3, which belong to group 1, and the received signals of A4 and A5, which belong to group 2, can be in phase. In this way, in multiple groups, the received signals of the antenna elements included in each group can be in phase. This can reduce the effective number of antenna elements and cause a grating lobe that points in a different direction from the actual observed object.

[0046] Next, we will discuss the case where antenna elements other than A2 are used in the antenna arrangement shown in Figure 4. Let's consider the case where A0, A1, A3, A4, and A5 belong to the same group. Let's call this group Group 1. When there are three or more antenna elements, as described in Patent Document 1, a phase difference in the received signals of multiple antenna elements occurs depending on the greatest common divisor of the spacing between the multiple antenna elements. In this case, in equations (1) and (2), D u D is the greatest common divisor of the spacing between multiple antenna elements in the U-axis direction, and v This is the greatest common divisor of the spacing between multiple antenna elements in the V-axis direction.

[0047] As mentioned above, U t =2 / 5, V t When = 3 / 5, the received signals of A1 and A3, which are positioned so as to lie on a straight line with slope K1, have the same phase. A0 has slope K1 and is positioned so as to lie on a straight line passing through the positions of A1 and A3. Therefore, U t =2 / 5, V t When =3 / 5, the received signals of A0, A1, and A3 have the same phase. Also, U t =2 / 5, V tWhen = 3 / 5, the received signals of A4 and A5, which are located on a straight line with slope K2, have the same phase. A0 is located on a straight line with slope K2 that passes through the positions of A4 and A5. Therefore, U t =2 / 5, V t When the phase is 3 / 5, the received signals A0, A4, and A5 have the same phase.

[0048] U t =2 / 5, V t When = 3 / 5, the Δd obtained for A0, A1, and A3, which are arranged on a straight line with slope K1, takes an integer multiple of the wavelength λ. t =2 / 5, V t When = 3 / 5, the Δd obtained for A0, A4, and A5, which are arranged on a straight line with slope K2, takes an integer multiple of the wavelength λ. Therefore, the received signals at A0, A1, and A3, and the received signals at A0, A4, and A5, have the same phase. In this way, even if antenna elements belonging to the same group are located on two different straight lines, the received signals can be in phase.

[0049] When antenna elements belonging to the same group are located on two different lines, it can be determined as follows whether the received signals can be in phase. Even if antenna elements belonging to the same group are located on two different lines, the received signals can be in phase if the two lines intersect at the position where either antenna element is placed. In the example shown in Figure 4, the line with slope K1 and the line with slope K2 intersect at the position where A0 is placed. Therefore, the received signals at A0, A1, A3, A4, and A5 can be in phase.

[0050] Furthermore, if A0, A1, A3, A4, and A5 belong to the same group, then assume that there are multiple antenna elements not shown in Figure 4, and that these multiple antenna elements belong to a different group, Group 2. Group 2 includes antenna elements other than A0, A1, A3, A4, and A5. For the sake of ease of understanding the technology, A2 shown in Figure 4 will not be considered. If all the antenna elements in Group 2 are arranged so as to be aligned on a straight line with inclination K1 or a straight line with inclination K2, then the received signals of the antenna elements in Group 1 and the received signals of the antenna elements in Group 2 may be in phase. This can result in a reduction in the effective number of antenna elements and the generation of a grating lobe that indicates a different direction from the actual observed object.

[0051] In the example above, multiple antenna elements were arranged along two straight lines with different slopes. Now, let's consider the case where multiple antenna elements are arranged along three straight lines with different slopes. Let the slopes of the three lines be K1, K2, and K3, respectively. In this case, assume the following situation holds: For the antenna elements arranged along the first straight line with slope K1, Δd = D u ·U t +K1·D u ·V t The equation =n11·λ holds. For antenna elements arranged to be aligned on a second straight line with slope K2, Δd=D u ·U t +K2·D u ·V t The equation =n12·λ holds. For antenna elements arranged to be aligned on the third straight line with slope K3, Δd=D u ·U t +K3·D u ·V t The equation = n13·λ holds true. Note that n11, n12, and n13 are all integers. In this case, since there are three independent equations, generally there are two independent variables U t and V t It is not possible to determine this. Therefore, the slope of the line will not have three or more values, but only two.

[0052] Furthermore, the embodiments assume a two-dimensional array antenna, and do not assume a one-dimensional array antenna. An array antenna in which the antenna elements are arranged on a line parallel to the U-axis is a one-dimensional array antenna. Similarly, an array antenna in which the antenna elements are arranged on a line parallel to the V-axis is also a one-dimensional array antenna. Therefore, array antennas in which the antenna elements are arranged on a line parallel to the U-axis and array antennas in which the antenna elements are arranged on a line parallel to the V-axis are excluded.

[0053] Furthermore, if the antenna elements are arranged so as to be aligned on a straight line having an inclination K1, or on a straight line having an inclination K2 different from inclination K1, and the straight line having inclination K1 or K2 is parallel to the U-axis, then when the antenna elements are not aligned on a straight line, the above (a) and (b) are satisfied, Δd = n·λ holds, but since the straight line having inclination K1 or K2 is parallel to the U-axis, D v = 0, meaning (b) is not satisfied. Therefore, (a) and (b) are not satisfied.

[0054] Furthermore, if the antenna elements are arranged so as to be aligned on a straight line having an inclination K1, or on a straight line having an inclination K2 different from inclination K1, and the straight line having inclination K1 or K2 is parallel to the V-axis, then D u = 0, meaning (a) is not satisfied. Therefore, (a) and (b) are not satisfied.

[0055] Based on the above, in the embodiment, the antenna elements are arranged as follows. When the antenna elements are arranged so as to be aligned on a straight line having an inclination K1, or on a straight line having an inclination K2 different from inclination K1, the straight line having inclination K1 and the straight line having inclination K2 must be straight lines that are not parallel to the U axis and the V axis. A straight line that is not parallel to the U axis is a straight line that has an inclination with respect to the U axis. A straight line that is not parallel to the V axis is a straight line that has an inclination with respect to the V axis.

[0056] Furthermore, in this embodiment, the K antenna elements included in the array antenna 210 are arranged point-symmetrically. As mentioned above, when there are L objects to observe, it is necessary to divide the antenna elements included in the array antenna 210 into L groups. L is a positive integer. For example, suppose the number of objects to observe is 2. In this case, it is necessary to divide the K antenna elements into 2 groups. In this embodiment, for reasons to be explained later, the K antenna elements are divided into 2 groups by dividing one of a pair of point-symmetrical antenna elements into the first group and the other into the second group. The reason for dividing the K point-symmetrically arranged antenna elements into one of a pair of point-symmetrical antenna elements into the first group and the other into the second group will be explained below.

[0057] First, as described in Patent Document 1, in order to determine the spacing of the antenna elements, it is necessary to generate all combinations of antenna elements to be included in each group when K antenna elements are divided into two groups. The number of grouping combinations is determined according to the number of antenna elements. In this embodiment, no distinction is made between the two groups. Also, the case in which either group does not contain any antenna elements is excluded. In this case, if the number of antenna elements is K, the number of grouping combinations is (2 K -2) / 2=2 K-1The answer is -1. For example, if the number of antenna elements is 16, the number of combinations is 32,767. If the number of antenna elements is 32, the number of combinations exceeds 2.1 billion. Furthermore, if the number of antenna elements is 64, the number of combinations is 1.8 × 10⁻¹⁰. 19 This exceeds [a certain value]. Thus, as the number of antenna elements increases, the number of combinations becomes enormous, and consequently, the computational complexity also becomes enormous. Therefore, it becomes practically impossible to perform the calculation.

[0058] Figure 5 shows an example of antenna elements arranged symmetrically. In the example shown, eight antenna elements, A1 to A8, are arranged. A1 and A8 are arranged symmetrically with respect to the central point CP. The central point CP is the point set as the center of the arrangement of the eight antenna elements. The central point CP is also called the center. A2 and A7 are arranged symmetrically with respect to the central point CP. A3 and A6 are arranged symmetrically with respect to the central point CP. A4 and A5 are arranged symmetrically with respect to the central point CP.

[0059] Suppose we divide a pair of point-symmetric antenna elements into two groups: one into group g1 and the other into group g2. Examples of grouping are as follows: Assign A1 to group g1 and A8 to group g2. Assign A7 to group g1 and A2 to group g2. Assign A6 to group g1 and A3 to group g2. Assign A5 to group g1 and A4 to group g2. Therefore, the elements assigned to group g1 are A1, A5, A6, and A7, and the elements assigned to group g2 are A2, A3, A4, and A8. In this case, the arrangement of the antenna elements in group g1, when rotated 180 degrees around the center point CP, coincides with the arrangement of the antenna elements in group g2. The arrangement of the antenna elements in group g1 and the arrangement of the antenna elements in group g2 are substantially the same.

[0060] Similarly, if, for example, A1, A2, A3, and A4 are assigned to group g1, and A5, A6, A7, and A8 are assigned to group g2, the same applies. In this case as well, the arrangement of the antenna elements in group g1 will overlap with the arrangement of the antenna elements in group g2 when rotated 180 degrees around the central point CP. Therefore, the arrangement of the antenna elements in group g1 and the arrangement of the antenna elements in group g2 are substantially the same.

[0061] In this way, by assigning one of a pair of point-symmetric antenna elements to group g1 and the other to group g2, the arrangement of the antenna elements in the two groups becomes substantially the same. Therefore, when generating combinations of grouping, the number of K antenna elements can be considered to be substantially halved. In this case, the number of combinations of grouping is 2 (K / 2-1) It is -1.

[0062] For example, suppose the number of antenna elements K is 16. When using the grouping method described above, the number of grouping combinations is 2 (16 / 2-1) -1 = 127. On the other hand, if the above grouping method is not used, the number of grouping combinations is 2 (16-1) -1 = 32767. In this way, the number of combinations can be greatly reduced, and thus the computational amount required to determine the arrangement of antenna elements can be greatly reduced. Also, for example, suppose the number of antenna elements K is 32. If the above grouping method is not used, the number of grouping combinations exceeds 2.1 billion. In this case, the number of grouping combinations is enormous, and it becomes practically difficult to calculate the arrangement of antenna elements. On the other hand, if the above grouping method is used, the number of combinations is 2 (32 / 2-1)-1 = 32767. In this way, the number of grouping combinations can be reduced to a degree that makes it practically possible to calculate the placement of antenna elements. Furthermore, the placement of antenna elements in each of the two divided groups becomes practically the same. When performing the calculations necessary to determine the spacing of the antenna elements, it is only necessary to calculate the spacing of the antenna elements in one of the groups. Since it is not necessary to calculate the spacing of the antenna elements in each of the two groups, the amount of computation required to determine the spacing of the antenna elements can be reduced.

[0063] Based on the above considerations, in this embodiment, the conditions for the arrangement of the antenna elements are as follows. First, in an array antenna that includes K antenna elements (K is an even number of 4 or more) arranged in two dimensions, and in which the K antenna elements are arranged point-symmetrically, the antenna elements are arranged to satisfy the following conditions 1 and 2. The number of objects to be observed is L (L is 2).

[0064] Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more antenna elements and having an inclination with respect to the U-axis and V-axis directions, A second group of lines consists of lines that are parallel to each other, have an inclination with respect to the U-axis and V-axis, are not parallel to the lines of the first group of lines, and intersect with any of the lines of the first group of lines at the position of the antenna element, combination A first process that defines the lines of the first set of lines and the lines of the second set of lines so that they pass through the positions of the most antenna elements, A second process involves distributing all lines included in the first group of lines and all lines included in the second group of lines into one or more groups of lines, each consisting of two or more lines that intersect each other at the position of the antenna element. The number of line groups and one or more antenna elements not located on the lines of the line groups are determined through the following process. The sum of the number of wire groups and the number of antenna elements (one or more) is (L+1) or greater. Condition 2: When dividing N antenna elements into two groups by dividing one of a pair of antenna elements, which are positioned point-symmetrically with respect to a point-symmetric center, into a first group and the other of the pair into a second group, in all combinations of grouping, The greatest common divisor D is the greatest common divisor of the spacing in the U-axis direction of the antenna elements included in the first group. gcd_U The greatest common divisor D is the greatest common divisor of the spacing in the V-axis direction of the antenna elements included in the first group. gcd_V When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where the wavelength of the received signal is λ, A system capable of detecting the observed object in the horizontal direction. Set the upper limit of the range to U max , In the aforementioned horizontal direction, the object to be observed can be detected. Lower limit of range U min , A system capable of detecting the observed object in the vertical direction. Set the upper limit of the range to V max , In the aforementioned vertical direction, the object of observation can be detected. The lower limit of the range is V min (Assuming), D gcd_U (U max -U min ) <L·λ···(5) D gcd_V (V max -V min ) <L·λ···(6)

[0065] Equations (5) and (6) of condition 2 are two-dimensional extensions of the equations that the spacing of antenna elements must satisfy, as described in Patent Document 1. When the arrangement of antenna elements is one-dimensional, the occurrence of grating lobes could be suppressed by adjusting the spacing of the antenna elements.

[0066] However, when the antenna elements are arranged in two dimensions, as mentioned above, adjusting the spacing between the antenna elements alone is not enough to suppress the occurrence of grating lobes. More specifically, false images may occur within the range defined by condition 2. Condition 1 is set to suppress this. Condition 1 is a necessary condition to be satisfied in order to resolve the problem of false images occurring when the technology disclosed in Patent Document 1 is applied to a two-dimensional array antenna. By selecting an antenna element arrangement that satisfies conditions 1 and 2, it is possible to prevent the occurrence of grating lobes in each range obtained by dividing the detectable range of the radar device 1 equally by the number of arriving waves, similar to Patent Document 1.

[0067] Furthermore, when dividing the N antenna elements arranged point-symmetrically in the array antenna 210 into two groups, by adopting a method of dividing one of a pair of point-symmetrical antenna elements into the first group and the other into the second group, the number of grouping combinations can be significantly reduced compared to a method in which one of a pair of point-symmetrical antenna elements is not divided into the first group and the other into the second group.

[0068] Furthermore, by dividing one of a point-symmetric pair of antenna elements into the first group and the other into the second group, the arrangement of antenna elements in each of the two groups becomes the same.

[0069] Therefore, the greatest common divisor (GCD) of the spacing of antenna elements in the U-axis direction in the first group is the same as the GCD of the spacing of antenna elements in the U-axis direction in the second group. Thus, it is only necessary to calculate the GCD of the spacing of antenna elements in the U-axis direction in one group. If the arrangement of antenna elements in the two groups is not the same, as described in Patent Document 1, it was necessary to first find the GCD of the spacing of antenna elements in the U-axis direction in each group and then calculate the GCD between the groups. However, in the method according to the embodiment, it is only necessary to calculate the GCD of the spacing of antenna elements in the U-axis direction in one group. Similarly, the greatest common divisor (GCD) of the spacing of antenna elements in the V-axis direction in the first group is the same as the GCD of the spacing of antenna elements in the V-axis direction in the second group. Thus, it is only necessary to calculate the GCD of the spacing of antenna elements in the V-axis direction in one group. Thus, the amount of computation required to determine the spacing of antenna elements can be reduced.

[0070] For example, the greatest common divisor (gcd1) of the spacing between the antenna elements in the U-axis direction of the first group of antenna elements is gcd1. u And the greatest common divisor (gcd2) of the spacing between the antenna elements of the second group in the first direction. u If they are different, the greatest common divisor is gcd1 u and the greatest common divisor gcd2 u The greatest common divisor of the first group (hereinafter referred to as the greatest common divisor between the groups) is the greatest common divisor of the first group, gcd1. u and the second group gcd2 u It will be a smaller value. For example, the greatest common divisor gcd1 in the first group. u Since is 2, the greatest common divisor in the second group is gcd2 u If is 3, the value of the greatest common divisor between the groups is 1. On the other hand, the greatest common divisor in the first group is gcd1 u and gcd2 in the second group u If both and are 2, then the greatest common divisor between the groups is 2. Thus, the greatest common divisor of the spacing in the U-axis direction of the antenna elements of the first group is gcd1. uAnd the greatest common divisor (gcd2) of the spacing between the antenna elements of the second group in the first direction. u If they are the same, the greatest common divisor of the spacing in the U-axis direction of the antenna elements of the first group is gcd1. u And the greatest common divisor (gcd2) of the spacing between the antenna elements of the second group in the first direction. u The value of the greatest common divisor between the groups is larger compared to the case where the two groups are different.

[0071] Furthermore, in order to estimate the direction of arrival with high accuracy using MUSIC or similar methods, it is necessary to increase the number of snapshots, which is the number of samples taken during the observation period. However, in automotive radar, it is necessary to estimate the direction of the observed object in real time. For this reason, the number of snapshots is sometimes increased by preprocessing using the spatial averaging method. When using an unequal-spacing array, the sub-array spatial averaging method cannot be used, so the forward spatial averaging method or the backward spatial averaging method is used. When using the forward spatial averaging method or the backward spatial averaging method, the antenna elements must be arranged point-symmetrically. The configuration according to this embodiment arranges the antenna elements point-symmetrically, so it is useful in reducing the amount of computation required to determine the spacing of the antenna elements when using the forward spatial averaging method or the backward spatial averaging method.

[0072] The following describes the process for checking whether condition 1 is satisfied. The number of objects to be observed, L, is 2. The process described below is performed, for example, by a computer equipped with a processor and memory.

[0073] First, a set of parallel lines is generated, each passing through the positions of two or more antenna elements. The generated set of lines does not include any lines parallel to the U-axis or V-axis. Note that the number of lines in the generated set of lines is not necessarily multiple; it may be just one. One or more sets of lines are generated. Of the generated sets of lines, the set that passes through the positions of the most antenna elements is determined to be the first set of lines.

[0074] Next, a second set of lines is determined, consisting of lines that are parallel to each other, are not parallel to any of the lines in the first set of lines, and intersect any of the lines in the first set of lines at the positions of the antenna elements. The lines in the second set of lines do not include lines parallel to the U-axis or V-axis. Note that the number of lines in the second set of lines is not necessarily multiple; it may be just one. Also, if there are multiple sets of lines that could form the second set of lines, the set of lines that passes through the positions of the most antenna elements is determined as the second set of lines. The process of defining the combination of the first set of lines and the second set of lines is also called the first process.

[0075] Next, all the lines in the first group of lines and all the lines in the second group of lines are divided into one or more groups of lines, each consisting of two or more lines that intersect each other at the positions of the antenna elements. One group of lines identifies a set of antenna elements in which the received signals can be in phase. The received signals of multiple antenna elements located on a line included in one group of lines can be in phase.

[0076] Next, confirm that the sum of the number of line groups and the number of antenna elements not on the line groups is 3 or greater, which is obtained by adding 1 to the number of observed objects. If the sum of the number of line groups and the number of antenna elements not on the line groups is 3 or greater, then condition 1 is satisfied.

[0077] Next, we will explain the process for checking whether condition 2 is satisfied. In an arrangement of antenna elements that satisfies condition 1, when dividing N antenna elements into two groups by dividing one of a pair of antenna elements positioned point-symmetric with respect to the center of point symmetry into the first group and the other of the pair into the second group, all possible combinations of grouping are generated. Assume that the number of generated combinations is C, where C is an integer greater than or equal to 1.

[0078] First, the following process is performed on the first combination: The two groups are designated as Group 1 and Group 2. The greatest common divisor D is the spacing between the antenna elements in the U-axis direction that are included in Group 1. gcd_U The following is required. Also, the greatest common divisor D of the spacing in the V-axis direction of the antenna elements included in group 1 is required. gcd_V This can be calculated. Furthermore, if equation (5) is satisfied, the greatest common divisor D is found. gcd_V Calculation of this is unnecessary.

[0079] It is determined whether at least one of equation (5) or equation (6) in condition 2 is satisfied. D gcd_U (U max -U min ) <L·λ···(5) D gcd_V (V max -V min ) <L·λ···(6)

[0080] Next, the same process is performed to check whether at least one of equation (5) or equation (6) is satisfied in the second combination. Then, the same process is performed for the third combination, ..., and the Cth combination, respectively.

[0081] If, among the combinations from the first to the Cth, there is one or more combinations that do not satisfy either equation (5) or equation (6), then the antenna element arrangement being considered will not be effective in suppressing grating lobes. Therefore, other antenna element arrangements will be reconsidered. In this way, for all combinations that can be grouped together for antenna arrangements that satisfy condition 1, it is checked whether at least one of equation (5) or equation (6) is satisfied. After the above process, an antenna arrangement that satisfies conditions 1 and 2 is determined.

[0082] In this way, by determining the spacing of the antenna elements, the occurrence of grating lobes can be avoided in a radar system having a two-dimensional unequal-spacing array antenna when the number of arriving waves is L or less.

[0083] A4. Examples that meet the placement requirements Figure 6 shows an example of antenna element arrangement. The number of observation targets is assumed to be 2. Note that the antenna element arrangement shown in Figure 6 is the same as in Figure 5.

[0084] First, a set of parallel lines is generated, each passing through the positions of two or more antenna elements. The generated set of lines does not include any lines parallel to the U-axis or V-axis. From the generated set of lines, we look for the set of lines that passes through the positions of the most antenna elements. In the example shown in Figure 6, the parallel lines L11 and L13 each pass through the positions of two or more antenna elements, and the number of antenna elements they pass through is 4, which is the maximum. Therefore, the set of lines consisting of lines L11 and L13 is determined to be the first set of lines. The slope K1 of the lines in the first set of lines is -3 / 5.

[0085] Next, we look for a second group of lines that are parallel to each other, are not parallel to the lines in the first group of lines, and intersect with one of the lines in the first group of lines at the position of an antenna element. The lines in the second group of lines do not include any lines parallel to the U-axis or V-axis. In the example shown in Figure 6, the group of lines consisting of the parallel lines L12 and L14 is not parallel to the first group of lines. Also, line L12 intersects with line L11 of the first group of lines at position A6. Line L14 intersects with line L13 of the first group of lines at position A3. Furthermore, the number of antenna elements that lines L12 and L14 pass through is 4, which is the largest number among the groups of lines consisting of lines that intersect with one of the lines in the first group of lines at the position of an antenna element. Therefore, the group of lines consisting of lines L12 and L14 is determined to be the second group of lines. The slope K2 of the lines in the second group of lines is -6.

[0086] Subsequently, all the lines included in the first group of lines and all the lines included in the second group of lines are divided into one or more groups of lines, each consisting of two or more lines that intersect each other at the position of the antenna element.

[0087] As shown in Figure 6, line L11 of the first line group and line L12 of the second line group intersect at position A6. Therefore, line L11 and line L12 form a single line group. Let this line group be called line group LG1.

[0088] Furthermore, line L13 of the first line group and line L14 of the second line group intersect at position A3. Therefore, line L13 and line L14 form a single line group. Let this line group be called line group LG2.

[0089] As described above, each line group identifies a set of antenna elements whose received signals can be in phase. Here, A1, A5, and A6, which lie on line group LG1, can have their received signals in phase. The antenna elements on line group LG1 are grouped together as antenna element group AG1. Similarly, A3, A4, and A8, which lie on line group LG2, can have their received signals in phase. The antenna elements on line group LG2 are grouped together as antenna element group AG2.

[0090] Additionally, antenna elements A2 and A7 are not located on the lines of line groups LG1 and LG2. Therefore, the sum of the number of line groups and the number of antenna elements not located on the line groups is 4. Note that the number of line groups and the number of antenna element groups are the same. Here, the number of observation targets L is 2. Therefore, the antenna configuration shown in Figure 5 satisfies condition 1.

[0091] Antenna elements A2 and A7 are not included in either antenna element group G1 or G2. Therefore, the received signals of antenna elements A2 and A7 cannot be in phase with the received signals of the antenna elements of antenna element group AG1. Furthermore, the received signals of antenna elements A2 and A7 cannot be in phase with the received signals of the antenna elements of antenna element group AG2. As mentioned above, when there are two observation targets, if there are two effective signals, a grating lobe may occur that indicates a different direction from the actual observation target. However, in the example shown in Figure 6, four effective signals can be secured. Therefore, in the antenna configuration shown in Figure 6, if condition 2, described later, is met, a grating lobe will not occur.

[0092] Next, let's consider condition 2. For example, suppose we assign A1, A5, A6, and A7 to group g1, and A2, A3, A4, and A8 to group g2. In Figure 6, the antenna elements of group g1 are represented by white circles, and the antenna elements of group g2 are represented by black circles. If we rotate A2, A3, A4, and A8, which belong to group g2, 180 degrees around the center point CP, they will overlap with A1, A5, A6, and A7, which belong to group g1. Thus, the arrangement of the antenna elements in group g1 and the arrangement of the antenna elements in group g2 are substantially the same.

[0093] The greatest common divisor of the spacing between antenna elements in group g1 in the U-axis direction is gcd1. U Since the arrangement of antenna elements in group g1 and group g2 are substantially the same, the greatest common divisor of the spacing of antenna elements in group g1 in the U-axis direction is gcd1. U And the greatest common divisor of the spacing between the antenna elements of group g2 in the U-axis direction is gcd2. U These are all 1d. The greatest common divisor of group g1 is gcd1. U The greatest common divisor D gcd_U Let's assume the greatest common divisor is D. gcd_U =λ / 2, and D gcd_U < 2λ, and equation (5) is satisfied.

[0094] Let's consider yet another example of antenna element combinations. For example, suppose we assign A1, A2, A3, and A4 to group g1, and A5, A6, A7, and A8 to group g2, as shown in Figure 7. Note that the arrangement of antenna elements shown in Figure 7 is the same as the examples shown in Figures 5 and 6. In Figure 7, the antenna elements of group g1 are represented by white circles, and the antenna elements of group g2 are represented by black circles.

[0095] The greatest common divisor of the spacing between antenna elements in group g1 in the U-axis direction is gcd1. U And the greatest common divisor of the spacing between the antenna elements of group g2 in the U-axis direction is gcd2.U Both of these are 1d. The greatest common divisor is gcd1. U The greatest common divisor D gcd_U Let's assume the greatest common divisor is D. gcd_U =λ / 2, and D gcd_U < 2λ, and equation (5) is satisfied.

[0096] Here, we have described two examples of grouping patterns. In practice, we generate all possible combinations of grouping and assume that in all combinations, at least one of (5) or equation (6) is satisfied. Thus, condition 2 is satisfied. When conditions 1 and 2 are satisfied, the antenna element arrangement shown in Figure 5 can be said to be an arrangement that can suppress the generation of grating lobes when the number of arriving waves is two or less.

[0097] Figure 8 shows the spectral image (hereinafter referred to as the MUSIC spectrum) output when two observation targets were observed using the array antenna configuration shown in Figure 6, and the direction of the observation targets was detected using MUSIC. The detected directions of the observation targets (hereinafter referred to as the target direction) are (U,V) = (1 / 2,1 / 2) and (-1 / 2,-1 / 2), respectively. In Figure 8, the observation targets are circled. As shown in this figure, no false images were generated.

[0098] A5. Example of adopting MIMO Another technique for virtually increasing the number of receiving antenna elements is MIMO (Multi Input Multi Output). By employing MIMO, a virtual receiving array antenna containing R × T virtual antenna elements can be realized from R (where R is an even number greater than or equal to 2) receiving antenna elements and T (where T is an even number greater than or equal to 2) transmitting antenna elements.

[0099] In the example shown in Figure 9, eight receiving antenna elements and four transmitting antenna elements are arranged. In Figure 9, receiving antenna elements are represented by white circles, and transmitting antenna elements by black circles. The transmitting antenna elements are arranged point-symmetrically, and the receiving antenna elements are also arranged point-symmetrically. The number of antenna elements virtually arranged by MIMO can be obtained by multiplying the number of receiving antenna elements by the number of transmitting antenna elements. As shown in Figure 10, the number of virtually arranged antenna elements is 32. Furthermore, the antenna elements virtually arranged by MIMO are also arranged point-symmetrically. To facilitate understanding of the technology, it is assumed that the arrangement of virtual antenna elements satisfies condition 1. The method of grouping virtual antenna elements according to condition 2 will be explained below.

[0100] If there are 32 virtual antenna elements, and we group them by dividing a pair of antenna elements that are positioned symmetrically from one another into two groups, the number of possible grouping combinations is 2 (32 / 2-1) -1 = 32767. As the number of grouping combinations increases, the amount of computation required to determine the spacing of the antenna elements also increases.

[0101] Therefore, when MIMO is adopted, the virtual antenna elements are grouped using the following methods C1 and C2. In order to divide the virtually arranged antenna elements into two groups, the number of groups Gr and Gt are determined such that the product of the number of receiving antenna elements Gr and the number of transmitting antenna elements Gt is 2.

[0102] The grouping method C1 is described below. In method C1, the number of groups Gt for the transmitting antenna elements is 2. First, all combinations of grouping are generated by dividing the pair of antenna elements, which are positioned symmetrically to each other, into two groups. The number of grouping combinations is 2 (4 / 2-1)= 2. In the example shown in Figure 9, in the first combination, A9 and A11 are assigned to one group, and A10 and A12 are assigned to the other group. In the second combination, A9 and A10 are assigned to one group, and A11 and A12 are assigned to the other group.

[0103] In the first combination, the resulting virtual antenna elements, obtained from A9 and A11 and the eight receiving antenna elements, are allocated to the first group. In the first combination, the resulting virtual antenna elements, obtained from A10 and A12 and the eight receiving antenna elements, are allocated to the second group. The arrangement of the virtual antenna elements obtained from the antenna elements in the first group coincides with the arrangement of the virtual antenna elements obtained from the antenna elements in the second group when rotated 180 degrees around the center point CP. The greatest common divisor D is the greatest common divisor of the spacing in the U-axis direction of the virtual antenna elements in the first group. gcd_U And the greatest common divisor D is the greatest common divisor of the spacing in the V-axis direction of the antenna elements included in the first group. gcd_V For and , it is determined whether at least one of equation (5) or equation (6) is satisfied.

[0104] In the second combination, the resulting virtual antenna elements are assigned to the first group by A9 and A10 and the eight receiving antenna elements. In the second combination, the resulting virtual antenna elements are assigned to the second group by A11 and A12 and the eight receiving antenna elements. The arrangement of the virtual antenna elements obtained by the antenna elements in the first group coincides with the arrangement of the virtual antenna elements obtained by the antenna elements in the second group when rotated 180 degrees around the center point CP. In the second combination as well, the greatest common divisor D is the greatest common divisor of the spacing in the U-axis direction of the virtual antenna elements in the first group. gcd_U And the greatest common divisor D is the greatest common divisor of the spacing in the V-axis direction of the antenna elements included in the first group. gcd_VFor and , it is determined whether at least one of equation (5) or equation (6) is satisfied.

[0105] Next, we will explain the grouping method C2. In method C2, the number of groups Gr for the receiving antenna elements is 2. First, we generate all combinations of grouping (hereinafter referred to as method C2) by dividing each pair of antenna elements, which are positioned symmetrically to each other, into two groups from among the 8 receiving antenna elements. The number of grouping combinations is 2 (8 / 2-1) = 8.

[0106] In the first combination, the resulting virtual antenna elements, consisting of the receiving antenna elements allocated to one group and the four transmitting antenna elements, are allocated to the first group. In the first combination, the resulting virtual antenna elements, consisting of the receiving antenna elements allocated to the other group and the four transmitting antenna elements, are allocated to the second group. The greatest common divisor D is the greatest common divisor of the spacing in the U-axis direction of the virtual antenna elements included in the first group. gcd_U And the greatest common divisor D is the greatest common divisor of the spacing in the V-axis direction of the antenna elements included in the first group. gcd_V For and , it is determined whether at least one of equation (5) or equation (6) is satisfied.

[0107] Next, the same process is performed to check whether at least one of equation (5) or equation (6) is satisfied in the second combination. Then, the same process is performed for the third, ..., and eighth combinations, respectively. If at least one of (5) or equation (6) is satisfied in all combinations, then the antenna element arrangement shown in Figure 9 can be said to be an arrangement that can suppress the generation of grating lobes when the number of arriving waves is two or less.

[0108] Figure 11 shows the spectral image output when two observation targets were observed using MIMO with the array antenna configuration shown in Figure 9, and the direction of the observed targets was detected using MUSIC. The detected directions of the observed targets (hereinafter referred to as target directions) are (U,V) = (1 / 2,1 / 2) and (-1 / 2,-1 / 2), respectively. In Figure 11, the observed targets are circled. As shown in this figure, no false images were generated.

[0109] There are 2 combinations of grouping using method C1 and 8 combinations of grouping using method C2, so the total number of grouping combinations is 10. If there are 32 virtual antenna elements, and the pair of antenna elements placed in point-symmetric positions are divided into two groups, then the number of grouping combinations is 2 (32 / 2-1) -1 = 32767. In this way, the number of grouping combinations can be significantly reduced. Furthermore, in all grouping combinations, the virtual arrangement of antenna elements in each of the two groups is virtually the same. Therefore, when performing the calculations necessary to determine the spacing of the antenna elements, it is sufficient to calculate the spacing of the antenna elements in one of the groups. Thus, it is not necessary to calculate the spacing of the antenna elements in each of the two groups. Consequently, the amount of computation required to determine the spacing of the antenna elements can be reduced.

[0110] In another arrangement example shown in Figure 12, there are 16 receiving antenna elements and 4 transmitting antenna elements. In Figure 12, the receiving antenna elements are represented by white circles and the transmitting antenna elements by black circles. The transmitting antenna elements are arranged point-symmetrically, and the receiving antenna elements are also arranged point-symmetrically. The positions of each transmitting antenna element, expressed in coordinates on the UV plane, are (-39,-36), (-36,39), (36,-39), and (39,36). The positions of each receiving antenna element, expressed in coordinates on the UV plane, are (-35,23), (-33,-9), (-24,-35), (-23,8), (-19,-19), (-17,33), (-8,1), (-1,-24), (1,24), (8,-1), (17,-33), (19,19), (23,-8), (24,35), (33,9), and (35,-23).

[0111] By employing MIMO in the arrangement shown in Figure 12, the number of virtually arranged antenna elements is 64. To facilitate understanding of the technology, the arrangement of virtual antenna elements is assumed to satisfy condition 1. When there are 64 virtual antenna elements, if we group them by dividing a pair of antenna elements arranged in point-symmetric positions into two, the number of grouping combinations is 2 (64 / 2-1) The result is -1, exceeding 2.1 billion. In this case, it becomes difficult to perform the calculations required to determine the spacing of the antenna elements.

[0112] Since there are 4 antenna elements for transmission, the number of grouping combinations using method C1 is 2 (4 / 2-1) = 2. For the first and second combinations, the process is performed to check whether at least one of equation (5) or equation (6) is satisfied, as described above. Also, since there are 16 receiving antenna elements, the number of combinations for grouping using method C2 is 2 (16 / 2-1)= 128. For the 1st combination, the 2nd combination, ..., the 128th combination is checked in the same way as described above to see if at least one of equation (5) or equation (6) is satisfied. If at least one of equation (5) or equation (6) is satisfied for all combinations, then condition 2 is satisfied. In this case, the antenna element arrangement shown in Figure 12 can be said to be an arrangement that can suppress the generation of grating lobes when the number of arriving waves is 2 or less.

[0113] If the number of virtual antenna elements is 64, using methods C1 and C2, the total number of grouping combinations is 130. In this way, the number of grouping combinations can be significantly reduced, and the computational amount required to determine the spacing of the antenna elements can be reduced.

[0114] B. Other Embodiments In the embodiment, an example was described in which the basic unit representing the distance between elements is d = λ / 2, but the embodiment is not limited to this. It is preferable that the basic unit representing the distance between elements is a value greater than 1 / 10 of the wavelength λ of the received signal.

[0115] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of Symbols]

[0116] 1...Radar device, 140...Transmitting antenna, 200...Receiver, 210...Array antenna, 220...Amplifier, 230...Mixer, 250...A / D converter, 320...Directional detection unit

Claims

1. An array antenna (210) comprising K antenna elements (where K is an even number of 4 or more) arranged in two dimensions, wherein the K antenna elements are arranged point-symmetrically, When the number of objects to be observed is L (where L is 2), the K antenna elements are arranged such that conditions 1 and 2 are satisfied. Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more antenna elements, and consisting of lines that are inclined with respect to a first direction and a second direction, A second group of lines, which are parallel to each other and have an inclination with respect to the first and second directions, and which are not parallel to the lines of the first group of lines, but which intersect with any of the lines of the first group of lines at the position of the antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more line groups, each consisting of two or more lines that intersect each other at the position of the antenna element. The number of the line groups and one or more antenna elements not located on the lines of the line groups are determined through the process, The sum of the number of the aforementioned wire groups and the number of the aforementioned one or more antenna elements is (L+1) or greater. Condition 2: When dividing the K antenna elements into two groups by dividing one of a pair of antenna elements, which are positioned point-symmetrically with respect to a point-symmetric center, into a first group and the other of the pair of antenna elements into a second group, in all combinations of grouping, The greatest common divisor D is the greatest common divisor of the spacing between the antenna elements included in the first group in the first direction. ｇｃｄ＿Ｕ The greatest common divisor D is calculated as the spacing between the antenna elements in the first group in the second direction. ｇｃｄ＿Ｖ When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where λ is the wavelength of the received signal, and U is the upper limit of the range in which the observed object can be detected in the horizontal direction). ｍａｘ , the lower limit of the range in which the observed object can be detected in the horizontal direction is U ｍｉｎ , the upper limit of the range in which the observed object can be detected in the vertical direction is V ｍａｘ , the lower limit of the range in which the observed object can be detected in the vertical direction is V ｍｉｎ (Assuming...) D ｇｃｄ＿Ｕ (U) ｍａｘ -U ｍｉｎ )<L・λ・・・(5) D ｇｃｄ＿Ｖ (V ｍａｘ -V ｍｉｎ )<L・λ・・・(6) Array antenna.

2. An array antenna used as a virtual receiving array antenna composed of R × T virtual antenna elements, comprising R (where R is an even number greater than or equal to 2) receiving antenna elements arranged in two dimensions and T (where T is an even number greater than or equal to 2) transmitting antenna elements arranged in two dimensions, The receiving antenna elements are arranged point-symmetrically with respect to the center of the arrangement of the receiving antenna elements, and the transmitting antenna elements are arranged point-symmetrically with respect to the center. When the number of objects to be observed is L (where L is 2), the receiving antenna element and the transmitting antenna element are arranged such that the arrangement of the virtual antenna elements satisfies conditions 1 and 2. Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more of the aforementioned virtual antenna elements, and consisting of lines that are inclined with respect to the first and second directions, A second group of lines, each consisting of parallel lines having an inclination with respect to the first and second directions, which are not parallel to the lines of the first group of lines, and which intersect any of the lines of the first group of lines at the position of the virtual antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most virtual antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more line groups, each consisting of two or more lines that intersect each other at the position of the virtual antenna element. The number of the line groups and one or more of the virtual antenna elements not located on the lines of the line groups are determined through the process, The sum of the number of the aforementioned wire groups and the number of the aforementioned one or more virtual antenna elements is (L+1) or greater. Condition 2: When dividing the R × T virtual antenna elements into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the receiving antenna element, into two groups, And, In the case where R × T virtual antenna elements are divided into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the transmitting antenna element, into two groups, In all combinations of grouping, The greatest common divisor of the spacing between the virtual antenna elements included in the first group in the first direction is the greatest common divisor D. ｇｃｄ＿Ｕ The greatest common divisor D is the greatest common divisor of the spacing between the virtual antenna elements in the second direction that are included in the first group. ｇｃｄ＿Ｖ When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where λ is the wavelength of the received signal, and U is the upper limit of the range in which the observed object can be detected in the horizontal direction). ｍａｘ , the lower limit of the range in which the observed object can be detected in the horizontal direction is U ｍｉｎ , the upper limit of the range in which the observed object can be detected in the vertical direction is V ｍａｘ , the lower limit of the range in which the observed object can be detected in the vertical direction is V ｍｉｎ (Assuming...) D ｇｃｄ＿Ｕ (U) ｍａｘ -U ｍｉｎ )<L・λ・・・(5) D ｇｃｄ＿Ｖ (V ｍａｘ -V ｍｉｎ )<L・λ・・・(6) Array antenna.

3. Radar device (1), A radar device comprising: a transmitting antenna (140) for transmitting a transmission signal; a receiving antenna (210) which is an array antenna including K antenna elements (K is an even number of 4 or more) arranged in two dimensions, wherein the K antenna elements are arranged point-symmetrically; a mixer (230) which mixes the received signal received by the K antenna elements with the transmitting signal to obtain a beat signal; an A / D converter (250) which samples the beat signal at a preset sampling frequency to obtain received data for multiple channels corresponding to the K antenna elements; and an orientation detection unit (320) which detects the distance to the object being observed and the direction in which the object is located based on the received data, When the number of objects to be observed is L (where L is 2), the K antenna elements are arranged such that conditions 1 and 2 are satisfied. Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more antenna elements, and consisting of lines that are inclined with respect to a first direction and a second direction, A second group of lines, which are parallel to each other and have an inclination with respect to the first and second directions, and which are not parallel to the lines of the first group of lines, but which intersect with any of the lines of the first group of lines at the position of the antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more line groups, each consisting of two or more lines that intersect each other at the position of the antenna element. The number of the line groups and one or more antenna elements not located on the lines of the line groups are determined through the process, The sum of the number of the aforementioned wire groups and the number of the aforementioned one or more antenna elements is (L+1) or greater. Condition 2: When dividing the K antenna elements into two groups by dividing one of a pair of antenna elements, which are positioned point-symmetrically with respect to a point-symmetric center, into a first group and the other of the pair of antenna elements into a second group, in all combinations of grouping, The greatest common divisor D is the greatest common divisor of the spacing between the antenna elements included in the first group in the first direction. ｇｃｄ＿Ｕ The greatest common divisor D is calculated as the spacing between the antenna elements in the first group in the second direction. ｇｃｄ＿Ｖ When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where λ is the wavelength of the received signal, and U is the upper limit of the range in which the observed object can be detected in the horizontal direction). ｍａｘ , the lower limit of the range in which the observed object can be detected in the horizontal direction is U ｍｉｎ , the upper limit of the range in which the observed object can be detected in the vertical direction is V ｍａｘ , the lower limit of the range in which the observed object can be detected in the vertical direction is V ｍｉｎ (Assuming...) D ｇｃｄ＿Ｕ (U) ｍａｘ -U ｍｉｎ )<L・λ・・・(5) D ｇｃｄ＿Ｖ (V ｍａｘ -V ｍｉｎ )<L・λ・・・(6) Radar device.

4. Radar device (1), A radar device comprising: an array antenna used as a virtual receiving array antenna composed of R × T virtual antenna elements, including R receiving antenna elements (R is an even number of 2 or more) arranged in two dimensions and T transmitting antenna elements (T is an even number of 2 or more) arranged in two dimensions; a mixer (230) that mixes the received signal and the transmitted signal to obtain a beat signal; an A / D converter (250) that samples the beat signal at a preset sampling frequency to obtain received data for multiple channels corresponding to the virtual antenna elements; and an orientation detection unit (320) that detects the distance to the object being observed and the direction in which the object is located based on the received data, The receiving antenna elements are arranged point-symmetrically with respect to the center of the arrangement of the receiving antenna elements, and the transmitting antenna elements are arranged point-symmetrically with respect to the center. When the number of objects to be observed is L (where L is 2), the receiving antenna element and the transmitting antenna element are arranged such that the arrangement of the virtual antenna elements satisfies conditions 1 and 2. Condition 1: The first process is, A first group of parallel lines, each passing through the positions of two or more of the aforementioned virtual antenna elements, and consisting of lines that are inclined with respect to the first and second directions, A second group of lines, each consisting of parallel lines having an inclination with respect to the first and second directions, which are not parallel to the lines of the first group of lines, and which intersect any of the lines of the first group of lines at the position of the virtual antenna element, combination A first process that defines such that the lines of the first group of lines and the lines of the second group of lines pass through the positions of the most virtual antenna elements, A second process involves distributing all the lines included in the first group of lines and all the lines included in the second group of lines into one or more line groups, each consisting of two or more lines that intersect each other at the position of the virtual antenna element. The number of the line groups and one or more of the virtual antenna elements not located on the lines of the line groups are determined through the process, The sum of the number of the aforementioned wire groups and the number of the aforementioned one or more virtual antenna elements is (L+1) or greater. Condition 2: When dividing the R × T virtual antenna elements into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the receiving antenna element, into two groups, And, In the case where R × T virtual antenna elements are divided into a first group and a second group by dividing a corresponding pair of antenna elements, which are positioned point-symmetrically with respect to the center in the transmitting antenna element, into two groups, In all combinations of grouping, The greatest common divisor of the spacing between the virtual antenna elements included in the first group in the first direction is the greatest common divisor D. ｇｃｄ＿Ｕ The greatest common divisor D is the greatest common divisor of the spacing between the virtual antenna elements in the second direction that are included in the first group. ｇｃｄ＿Ｖ When calculated as follows, at least one of equation (5) or equation (6) is satisfied (where λ is the wavelength of the received signal, and U is the upper limit of the range in which the observed object can be detected in the horizontal direction). ｍａｘ , the lower limit of the range in which the observed object can be detected in the horizontal direction is U ｍｉｎ , the upper limit of the range in which the observed object can be detected in the vertical direction is V ｍａｘ , the lower limit of the range in which the observed object can be detected in the vertical direction is V ｍｉｎ (Assuming...) D ｇｃｄ＿Ｕ (U) ｍａｘ -U ｍｉｎ )<L・λ・・・(5) D ｇｃｄ＿Ｖ (V ｍａｘ -V ｍｉｎ )<L・λ・・・(6) Radar device.

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