Radar device

Abstract

To improve angular measurement accuracy or resolution in a radar device.SOLUTION: In a radar device, a plurality of transmission antennas or a plurality of reception antennas includes a plurality of first antenna groups arranged in parallel to each other in a first direction and a plurality of second antenna groups arranged in parallel to each other in a second direction different from the first direction, and the remaining other of the plurality of transmission antennas and the plurality of reception antennas includes a plurality of third antenna groups arranged in parallel to each other in a third direction different from each of the first direction and the second direction. Each of the plurality of first antenna groups has a first interval between adjacent antennas in the first direction, each of the plurality of second antenna groups has the first interval between adjacent antennas in the second direction, and each of the plurality of third antenna groups has a second interval wider than the first interval between adjacent antennas in the third direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to a radar device.

Background Art

[0002] In recent years, studies have been underway on radar devices using radar transmission signals with short wavelengths including microwaves or millimeter waves that can obtain high resolution. In addition, in order to improve outdoor safety, there is a demand for the development of radar devices (for example, called wide-angle radar devices) that can detect small objects such as pedestrians in a wide-angle range even outside vehicles.

[0003] As a configuration of a radar device having a wide detection range, for example, a reflected wave from a target (or a target) is received by an array antenna composed of a plurality of antennas (or also called antenna elements), and based on the reception phase difference with respect to the element interval (antenna interval), a method of estimating the direction (or called the arrival angle) in which the reflected wave arrives (arrival angle estimation method. Direction of Arrival (DOA) estimation) is used.

[0004] For example, as the arrival angle estimation method, there are a Fourier method (FFT (Fast Fourier Transform) method), or the Capon method, MUSIC (Multiple Signal Classification), and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) as methods that can obtain high resolution.

[0005] In addition, as a radar device, for example, in addition to the receiving side, a configuration in which a plurality of antennas (array antennas) are also provided on the transmitting side and beam scanning is performed by signal processing using the transmit-receive array antennas (sometimes called MIMO (Multiple Input Multiple Output) radar) has been proposed (for example, refer to Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2021-081282 [Non-Patent Document]

[0007] [Non-Patent Document 1] J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 [Non-Patent Document 2] Kazuo Shirakawa et al., "Automotive 3D Scanning Millimeter-Wave Radar", Fujitsu Ten Technical Report, Vol.30, No.1, 2012. [Non-Patent Document 3] M. Kronauge, H.Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 [Non-Patent Document 4] Direction-of-arrival estimation using signal subspace modeling Cadzow, J.A.; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28, Issue: 1 Publication Year: 1992, Page(s): 64 - 79 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] However, there is room for study on methods for improving the angle measurement accuracy or resolution in a radar device (for example, a MIMO radar).

[0009] Non-limiting embodiments of the present disclosure contribute to providing a radar device capable of improving angular measurement accuracy or resolution.

Means for Solving the Problem

[0010] A radar device according to an embodiment of the present disclosure includes a transmission circuit that transmits a transmission signal using a plurality of transmission antennas, and a reception circuit that receives a reflected wave signal obtained by reflecting the transmission signal from an object using a plurality of reception antennas. Either one of the plurality of transmission antennas or the plurality of reception antennas includes a first antenna group arranged in a first direction and a second antenna group arranged in a second direction different from the first direction, and the remaining one of the plurality of transmission antennas or the plurality of reception antennas includes a third antenna group arranged in a third direction different from each of the first direction and the second direction, where the interval between adjacent antennas is equal to or greater than one wavelength of the transmission signal.

[0011] These general or specific embodiments may be implemented in a system, apparatus, method, integrated circuit, computer program, or recording medium, or any combination of a system, apparatus, method, integrated circuit, computer program, and recording medium.

Advantages of the Invention

[0012] According to an embodiment of the present disclosure, the angular measurement accuracy or resolution in a radar device can be improved.

[0013] Further advantages and effects in an embodiment of the present disclosure will be apparent from the specification and drawings. Such advantages and / or effects are provided by some embodiments and the features described in the specification and drawings respectively, but not necessarily all are provided to obtain one or more identical features.

Brief Description of the Drawings

[0014]

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Embodiments for Carrying out the Invention

[0015] The MIMO radar transmits a multiplexed signal (radar transmission wave) using, for example, time division, frequency division, or code division from a plurality of transmission antennas (or called transmission array antennas). Then, the MIMO radar receives, for example, a signal (radar reflected wave) reflected by surrounding objects using a plurality of reception antennas (or called reception array antennas), and separates and receives the multiplexed transmission signal from each received signal. Through such processing, the MIMO radar can extract the propagation path response indicated by the product of the number of transmission antennas and the number of reception antennas, and performs array signal processing on these received signals as a virtual reception array.

[0016] In the MIMO radar, by devising the arrangement of the antenna elements in the transmit-receive array antenna, a virtual reception array antenna (hereinafter referred to as a virtual reception array, MIMO virtual reception array, virtual reception antenna, or virtual reception array antenna) that is at most equal to the product of the number of transmission antenna elements and the number of reception antenna elements can be configured. Thereby, the effect of increasing the effective aperture length of the array antenna with a small number of elements can be obtained, and the angle measurement accuracy or resolution can be improved.

[0017] In addition to one-dimensional scanning (angle measurement) in the vertical or horizontal direction, the MIMO radar can also be applied to beam scanning (angle measurement) in two dimensions in the vertical and horizontal directions (see, for example, Non-Patent Document 2).

[0018] As an example, Fig. 1(a) shows a transmitting array antenna including four transmitting antennas (Tx#1 to Tx#4) arranged in the vertical direction (the vertical direction in Fig. 1(a)), and a receiving array antenna including four receiving antennas (Rx#1 to Rx#4) arranged in the horizontal direction (the horizontal direction in Fig. 1(a)). In Fig. 1(a), the transmitting antennas are arranged at equal intervals (d V ) in the vertical direction, and the receiving antennas are arranged at equal intervals (d H ) in the horizontal direction (see, for example, Non-Patent Document 2).

[0019] Fig. 1(b) shows a virtual receiving array including the transmitting and receiving array antennas with the antenna arrangement shown in Fig. 1(a). The virtual receiving array shown in Fig. 1(b) is composed of a 16-element virtual antenna (VA#1 to VA#16) in which four antennas are arranged in a rectangular shape in the horizontal direction and four antennas are arranged in the vertical direction. In Fig. 1(b), the element intervals in the horizontal and vertical directions of the virtual receiving array are d H , d V , respectively. The aperture lengths A H , A V in the horizontal and vertical directions of the virtual receiving array are A H = 3d H , A V = 3d V , respectively.

[0020] Figs. 2(a) and 2(b) show the Fourier beam patterns directed in the horizontal 0° and vertical 0° directions when the element interval d H in the horizontal direction is set to 0.5λ and the element interval d V in the vertical direction is set to 0.5λ in the antenna arrangement of the MIMO radar shown in Fig. 1(a). Note that λ represents the wavelength of the radar carrier wave.

[0021] As shown in FIGS. 2(a) and 2(b), main beams (main lobes) are formed in the horizontal 0° and vertical 0° directions. Here, the narrower the beam width of the main beam, the better the angular separation performance for a plurality of targets. For example, in FIGS. 2(a) and 2(b), the beam width at a power value of 3 dB is about 26°. Also, as shown in FIGS. 2(a) and 2(b), side lobes are generated around the main beam. In a radar device, the side lobes become a factor of false detection as virtual images. Therefore, the lower the peak level of the side lobes, the lower the probability of false detection as a virtual image in the radar device. In FIGS. 2(a) and 2(b), for example, the power ratio (peak sidelobe level ratio (PSLR)) of the peak level of the side lobes normalized by the peak level of the main beam is about -13 dB (however, when using an equal-amplitude beam weight).

[0022] In order to increase the detection distance in a radar device, it is effective to use an antenna with high gain. For example, by narrowing the directivity (beam width) of the antenna, the antenna gain can be improved. The directivity of the antenna becomes narrower, for example, as the aperture area of the antenna is increased. Therefore, in order to narrow the directivity of the antenna, the antenna size tends to become larger.

[0023] For example, in a radar device mounted on a vehicle (also referred to as an in-vehicle radar, for example), in order to narrow the directivity in the vertical direction, a sub-array antenna configured by arranging a plurality of antenna elements in the vertical direction may be used. By narrowing the directivity in the vertical direction with the sub-array antenna, the antenna gain in the vertical direction can be improved, and reflected waves in unnecessary directions such as the road surface can be reduced.

[0024] Note that the vertical direction is the height direction of the vehicle on which the radar device is mounted (or installed). Also, the horizontal direction is the straight-ahead direction of the vehicle, the direction orthogonal to the straight-ahead direction of the vehicle, or the direction orthogonal to the height direction of the vehicle.

[0025] Note that when the radar device is mounted (or installed) on the signal device, for example, the vertical direction may be the direction of gravity, and the horizontal direction may be a direction orthogonal to the direction of gravity.

[0026] For example, FIG. 3 shows an example of a sub-array in which 8 elements are arranged in the vertical direction (the longitudinal direction in FIG. 3) and 1 element is arranged in the horizontal direction (the lateral direction in FIG. 3) for a planar patch antenna. In FIG. 3, H ANT represents the antenna size in the vertical direction, and W ANT represents the antenna size in the horizontal direction. Note that the configuration of the sub-array is not limited to the configuration shown in FIG. 3. For example, the number of elements in each of the vertical and horizontal directions may be different from the numbers shown in FIG. 3.

[0027] Here, when the sub-array antenna is used as an antenna element constituting a transmitting array antenna or a receiving array antenna, the antenna elements of the array antenna cannot be arranged at intervals narrower than the size of the sub-array antenna. For example, when the antenna elements constituting the sub-array antenna are arranged in the vertical direction, the size of the sub-array antenna can be 1 wavelength or more. Therefore, for example, when using a sub-array antenna in the vertical direction (when sub-arrayed in the vertical direction) in the MIMO radar shown in FIG. 1(a), the element interval d V in the vertical direction is widened to 1 wavelength or more.

[0028] FIGS. 4 and 5 show an example of the Fourier beam patterns directed in the horizontal 0° and vertical 0° directions when the element interval d V in the vertical direction is set to 1 wavelength (λ) or more in the transmitting and receiving antenna arrangements of the MIMO radar shown in FIG. 1(a). Note that in FIGS. 4 and 5, the directivity of a single antenna element sub-arrayed in the vertical direction is not considered.

[0029] In FIG. 4, the element interval d v in the vertical direction is λ, and the element interval d H in the horizontal direction is 0.5λ. In FIG. 5, the element interval d V in the vertical direction is 2λ, and the element interval d H in the horizontal direction is 0.5λ.

[0030] As shown in FIGS. 4 and 5, the main beam (main lobe) is directed in the horizontal 0° and vertical 0° directions. For example, compared with the side lobes in FIGS. 2(a) and 2(b), high-level side lobes (e.g., grating lobes) are generated in the vertical direction around the main beam. In FIGS. 4 and 5, the ratio of the peak level of the grating lobe to the peak level of the main lobe (peak side lobe ratio) is 0 dB. Also, in FIG. 5(d V =2λ), compared with FIG. 4(d V =λ), the angular interval at which high-level side lobes (e.g., grating lobes) are generated in the vertical direction becomes narrower. That is, it can be confirmed that the wider the element interval d V in the vertical direction, the narrower the angular interval at which side lobes (e.g., grating lobes) are generated.

[0031] Thus, in the radar device, the larger the antenna size in the vertical direction, the wider the element interval in the vertical direction, and thus grating lobes are more likely to be generated at angles relatively close to the main beam. Therefore, when the detection angle range assumed in the radar device is wider than the angle at which grating lobes are generated, the radar device may erroneously detect a false peak caused by the grating lobe as a target within the detection angle range, and the detection performance of the radar device may deteriorate.

[0032] Also, for example, even if the grating lobe is outside the detection angle range assumed in the radar device, if the power of the reflected wave arriving from the grating lobe direction is sufficiently large, the radar device is likely to erroneously detect that a target has arrived within the viewing angle, and the detection performance of the radar device may deteriorate. For example, when the element interval is 1 wavelength or more, grating lobes are always generated within the range of ±90 degrees. Therefore, even for a radar device with a narrow viewing angle, deterioration of the radar detection performance due to false detection by the grating lobe is likely to occur.

[0033] On the other hand, for example, the wider the element spacing in the vertical direction, the narrower the beam width in the vertical direction, and the angular measurement accuracy or angular resolution in the vertical direction of the radar device can be improved. For example, comparing the element spacings in the vertical direction in FIGS. 2, 4, and 5, they are 0.5λ, λ, and 2λ respectively. When comparing the main lobes in the Fourier beam pattern, it can be confirmed that the wider the element spacing in the vertical direction, the narrower the beam width in the vertical direction, and a sharper beam is formed. Thus, the narrower the beam width in the vertical direction, the more the angular measurement accuracy or angular resolution in the vertical direction of the radar device can be improved.

[0034] Similarly, for example, the wider the element spacing in the horizontal direction, the narrower the beam width in the horizontal direction, and the angular measurement accuracy or angular resolution in the horizontal direction of the radar device can be improved. On the other hand, the wider the element spacing in the horizontal direction, the easier it is for grating lobes to occur. For example, when the detection angle range assumed by the radar device is wider than the angle at which grating lobes occur, the radar device has an increased probability of erroneously detecting a false peak caused by the grating lobe as a target within the detection angle range, and the detection performance of the radar device may deteriorate.

[0035] Therefore, in a non-limiting embodiment of the present disclosure, an antenna arrangement capable of suppressing grating lobes while widening the element spacing in at least one of the vertical and horizontal directions will be described. By realizing such an antenna arrangement, the angular measurement accuracy or resolution can be improved with a smaller number of antennas.

[0036] Note that the radar device according to an embodiment of the present disclosure may be mounted on a moving body such as a vehicle, for example. The radar device mounted on the moving body can be used as a sensor for, for example, an advanced driver assistance system (ADAS) that enhances collision safety or for monitoring the surroundings of the moving body during autonomous driving.

[0037] Further, the radar device according to an embodiment of the present disclosure may be attached to a relatively high structure such as a roadside utility pole or traffic signal. Such a radar device can be used, for example, as a sensor in an assistance system for enhancing the safety of passing vehicles or pedestrians.

[0038] Note that the applications of the radar device are not limited to these, and it may be used for other applications.

[0039] Hereinafter, embodiments according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In the embodiments, the same components are denoted by the same reference numerals, and the description thereof will be omitted since it is redundant.

[0040] Hereinafter, a radar device having a configuration in which a transmission branch transmits different transmission signals code-division multiplexed from a plurality of transmission antennas, and a reception branch separates each transmission signal and performs reception processing (in other words, a MIMO radar configuration) will be described. However, the configuration of the radar device is not limited to this, and a configuration in which the transmission branch transmits different transmission signals frequency-division multiplexed from a plurality of transmission antennas, and the reception branch separates each transmission signal and performs reception processing may also be used. Similarly, the configuration of the radar device may be such that the transmission branch transmits transmission signals time-division multiplexed from a plurality of transmission antennas, and the reception branch performs reception processing.

[0041] Similarly, a configuration in which the transmission branch transmits different transmission signals Doppler-division multiplexed from a plurality of transmission antennas, and the reception branch separates each transmission signal and performs reception processing may also be used. Similarly, a configuration in which the transmission branch transmits transmission signals multiplexed by combining at least two of code-division multiplexing, time-division multiplexing, and Doppler-division multiplexing from a plurality of transmission antennas, and the reception branch separates each transmission signal and performs reception processing may also be used.

[0042] In the following, as an example, the configuration of a radar system (also referred to as fast chirp modulation, for example) using a frequency-modulated pulse wave such as a chirp pulse will be described. However, the modulation method is not limited to frequency modulation. For example, one embodiment of the present disclosure is also applicable to a radar system using a single pulse or a coded pulse.

[0043] (Embodiment 1) [Configuration of Radar Device] FIG. 6 is a block diagram showing a configuration example of a radar device 10 according to the present embodiment.

[0044] The radar device 10 includes a radar transmitter (transmission branch) 100 and a radar receiver (reception branch) 200.

[0045] The radar transmitter 100 generates a radar signal (radar transmission signal) and transmits the radar transmission signal at a prescribed transmission cycle using a transmission array antenna composed of a plurality of transmission antennas 106 (for example, N tx pieces).

[0046] The radar receiver 200 receives a reflected wave signal, which is a radar transmission signal reflected by a target (object, not shown), using a reception array antenna including a plurality of reception antennas 202 (for example, Na pieces). The radar receiver 200 processes the reflected wave signals received by the respective reception antennas 202, and for example, detects the presence or absence of a target or estimates the arrival distance, Doppler frequency (in other words, relative velocity), and arrival direction of the reflected wave signal, and outputs information regarding the estimation result (in other words, positioning information).

[0047] Note that the target is an object to be detected by the radar device 10, and includes, for example, vehicles (including four-wheeled and two-wheeled vehicles), people, blocks, or curbstones.

[0048] [Configuration of Radar Transmitter 100] The radar transmission unit 100 includes a radar transmission signal generation unit 101, a code generation unit 104, a phase rotation unit 105, and a transmission antenna 106.

[0049] The radar transmission signal generation unit 101 generates a radar transmission signal. The radar transmission signal generation unit 101 includes, for example, a modulation signal generation unit 102 and a VCO (Voltage Controlled Oscillator) 103. Hereinafter, each component in the radar transmission signal generation unit 101 will be described.

[0050] The modulation signal generation unit 102 generates a sawtooth-shaped modulation signal (in other words, a modulation signal for VCO control) for each radar transmission period Tr.

[0051] Based on the modulation signal output from the modulation signal generation unit 102, the VCO 103 generates, for example, a frequency modulation signal (hereinafter, for example, referred to as a frequency chirp signal or a chirp signal) as shown in FIG. 7(a), and outputs it to the phase rotation unit 105 and the radar reception unit 200 (the mixer unit 204 described later).

[0052] The code generation unit 104 generates different codes for each transmission antenna 106 that performs code multiplex transmission. The code generation unit 104 outputs the phase rotation amount corresponding to the generated code to the phase rotation unit 105. Further, the code generation unit 104 outputs information regarding the generated code to the radar reception unit 200 (the output switching unit 209 described later).

[0053] The phase rotation unit 105 applies the phase rotation amount input from the code generation unit 104 to the chirp signal input from the VCO 103, and outputs the phase-rotated signal to the transmission antenna 106. For example, the phase rotation unit 105 includes, for example, a phase shifter and a phase modulator (not shown). The output signal of the phase rotation unit 105 is amplified to a specified transmission power and radiated into space from each transmission antenna 106. In other words, the radar transmission signal is code multiplex transmitted from a plurality of transmission antennas 106 by being given a phase rotation amount corresponding to the code.

[0054] Next, an example of a code (for example, an orthogonal code) set in the radar device 10 will be described.

[0055] The code generation unit 104 generates different codes for each transmission antenna 106 that performs code multiplexing transmission, for example.

[0056] For example, hereinafter, the number of transmission antennas 106 that perform code multiplexing transmission is set to "Nt", and the code multiplexing number is set to "N" CM ". In FIG. 6, N CM = Nt.

[0057] The code generation unit 104 selects N allcode (hereinafter, sometimes described as N allcode (Loc)) of orthogonal codes included in a code sequence of code length (in other words, the number of code elements) Loc (for example, an orthogonal code sequence having an orthogonal relationship with each other (or simply referred to as a code or an orthogonal code)) and sets them as codes for code multiplexing transmission. CM

[0058] For example, the code multiplexing number N CM is set to be less than or equal to the number of orthogonal codes N allcode , and N CM ≦ N allcode . For example, N CM orthogonal codes of code length Loc are represented as Code ncm = [OC ncm (1), OC ncm (2),..., OC ncm (Loc)]. Here, "OC ncm (noc)" represents the noc-th code element in the ncm-th orthogonal code Code ncm . Also, "ncm" represents the index of the orthogonal code used for code multiplexing, and ncm = 1,..., N CM . Also, "noc" is the index of the code element, and noc = 1,..., Loc.

[0059] As described above, N CMThe orthogonal codes are, for example, codes that are orthogonal to each other (in other words, uncorrelated codes). For example, Walsh-Hadamard codes may be used for the orthogonal code sequence. The code length of the Walsh-Hadamard code is a power of 2, and the orthogonal code of each code length includes the same number of orthogonal codes as the code length. For example, the Walsh-Hadamard codes with code lengths of 2, 4, 8, or 16 include 2, 4, 8, or 16 orthogonal codes, respectively.

[0060] Hereinafter, as an example, the number of codes N CM The code length Loc of the orthogonal code sequence is set to satisfy the following equation (1).

Equation

[0061] Here, ceil[x] is an operator (ceiling function) that outputs the smallest integer greater than or equal to the real number x. In the case of the Walsh-Hadamard code with code length Loc, the relationship N allcode (Loc) = Loc holds. For example, since the Walsh-Hadamard codes with code lengths Loc = 2, 4, 8, or 16 include 2, 4, 8, or 16 orthogonal codes, respectively, N allcode (2) = 2, N allcode (4) = 4, N allcode (8) = 8, and N allcode (16) = 16 holds. The code generation unit 104 uses, for example, N allcode (Loc) out of the N CM orthogonal codes included in the Walsh-Hadamard code with code length Loc.

[0062] Hereinafter, an example of the orthogonal code for each code multiplicity N CM will be described.

[0063] For example, when the code multiplicity N CM = 3, the code generation unit 104 determines, for example, 3 orthogonal codes out of the Walsh-Hadamard codes with code length Loc = 4 as the codes for code multiplex transmission. For example, the code generation unit 104 may select Code1 = WH4(3) = [1, 1, -1, -1], Code2 = WH4(4) = [1, -1, -1, 1], and Code3 = WH4(2) = [1, -1, 1, -1].

[0064] For example, the code generation unit 104 may select N CM orthogonal codes from among the Walsh - Hadamard codes of the code length Loc shown in Equation (2) as the codes for code multiplex transmission. In this case, N CM ≦Loc = N allcode (Loc). [Number]

[0065] Note that the elements constituting the orthogonal code sequence are not limited to real numbers and may include complex numerical values.

[0066] Also, the code may be another orthogonal code different from the Walsh - Hadamard code. For example, the code may be an orthogonal M - sequence code or a pseudo - orthogonal code.

[0067] As described above, an example of the orthogonal code for each code multiplexing number N CM has been described.

[0068] Next, an example of the phase rotation amount based on the code for code multiplex transmission generated by the code generation unit 104 will be described.

[0069] The radar device 10 performs code multiplex transmission using different orthogonal codes for each of the transmission antennas Tx#1 to Tx#Nt that perform code multiplex transmission, for example. Therefore, the code generation unit 104, for example, in the m - th transmission period Tr, sets the phase rotation amount ψ ncm based on the orthogonal code Code ncm (m) to be applied to the ncm - th transmission antenna Tx#ncm and outputs it to the phase rotation unit 105. Here, ncm = 1, …, N CM .

[0070] For example, the phase rotation amount ψ ncm (m) is, as shown in the following equation (3), for each period of the transmission period of the code length Loc times, the orthogonal code Code ncm Of the Loc code elements OC ncm (1), …, OC ncm (Loc) is cyclically assigned the corresponding phase amounts.

Equation

[0071] Here, angle(x) is an operator that outputs the radian phase of the real number x, angle(1) = 0, angle(-1) = π, angle(j) = π / 2, and angle(-j) = -π / 2. j is the imaginary unit. Also, OC_INDEX is the orthogonal code element index that indicates the elements of the orthogonal code sequence Code ncm And it varies cyclically in the range from 1 to Loc as shown in the following equation (4) for each transmission period (Tr).

Equation

[0072] Here, mod(x,y) is the modulo operator and is a function that outputs the remainder after dividing x by y. Also, m = 1, …, Nc. Nc is the predetermined number of transmission periods (hereinafter referred to as the "number of radar transmission signal transmissions") used by the radar device 10 for radar positioning. Also, the radar device 10 performs transmissions of the number of radar transmission signals Nc that is an integer multiple of Loc (for example, Ncode times). For example, Nc = Loc × Ncode.

[0073] Also, the code generation unit 104 outputs the orthogonal code element index OC_INDEX to the output switching unit 209 of the radar receiving unit 200 for each transmission period (Tr).

[0074] The phase rotation unit 105 is, for example, N txIt includes phase shifters or phase modulators respectively corresponding to the individual transmission antennas 106. For example, every transmission period Tr, the phase rotation unit 105 applies a phase rotation amount ψ ncm (m) to the chirp signal input from the radar transmission signal generation unit 101.

[0075] For example, every transmission period Tr, the phase rotation unit 105 applies, to the chirp signal input from the radar transmission signal generation unit 101, the phase rotation amount ψ ncm based on the orthogonal code Code ncm (m) to the ncm-th transmission antenna Tx#ncm. Here, ncm = 1, …, N CM and m = 1, .., Nc.

[0076] N tx The outputs from the phase rotation unit 105 for the N tx individual transmission antennas 106 are, for example, amplified to a predetermined transmission power and then radiated into space from the N

[0077] As an example, the case of code multiplex transmission when the number of transmission antennas N Tx = 3 and the code multiplicity N CM = 3 will be described. Note that the number of transmission antennas Nt and the code multiplicity N CM are not limited to these values.

[0078] For example, the phase rotation amounts ψ1(m), ψ2(m) and ψ3(m) are output from the code generation unit 104 to the phase rotation unit 105 every m-th transmission period Tr.

[0079] The first phase rotation unit 105 (in other words, the phase shifter corresponding to the first transmission antenna 106 (for example, Tx#1)) applies phase rotation to the chirp signal generated by the radar transmission signal generation unit 101 every transmission period Tr according to the following equation (5) every transmission period Tr. The output of the first phase rotation unit 105 is transmitted from the transmission antenna Tx#1. Here, cp(t) represents the chirp signal in the m-th transmission period Tr. [Equation]

[0080] Similarly, the second phase rotation unit 105 (ncm = 2) applies phase rotation to the chirp signal generated by the radar transmission signal generation unit 101 every transmission period Tr according to the following equation (6) every transmission period Tr. The output of the second phase rotation unit 105 is transmitted from the transmission antenna Tx#2. [Equation]

[0081] Similarly, the third phase rotation unit 105 (ncm = 3) applies phase rotation to the chirp signal generated by the radar transmission signal generation unit 101 every transmission period Tr according to the following equation (7) every transmission period Tr. The output of the third phase rotation unit 105 is transmitted from the transmission antenna Tx#3. [Equation]

[0082] Note that when the radar device 10 continuously performs radar positioning, for each radar positioning (for example, every Nc transmission periods (Nc × Tr)), the code used for the orthogonal code Code ncm may be variably set.

[0083] The configuration example of the radar transmission unit 100 has been described above.

[0084] [Configuration of Radar Reception Unit 200] In FIG. 6, the radar receiving unit 200 includes Na receiving antennas 202 (which may also be denoted as Rx#1 to Rx#Na for example) and constitutes an array antenna. The radar receiving unit 200 also includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a code multiplexing separation unit 212, and a direction estimation unit 213.

[0085] Each receiving antenna 202 receives a reflected wave signal that is a radar transmission signal reflected by a target, and outputs the received reflected wave signal as a received signal to the corresponding antenna system processing unit 201.

[0086] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206.

[0087] The receiving radio unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with a chirp signal that is a transmission signal input from the radar transmission signal generation unit 101. The LPF 205 outputs a beat signal having a frequency corresponding to the delay time of the reflected wave signal by performing LPF processing on the output signal of the mixer unit 204. For example, as shown in the lower part of FIG. 7, the difference frequency between the frequency of the transmission chirp signal (transmission frequency modulation wave) and the frequency of the received chirp signal (received frequency modulation wave) is obtained as the beat frequency.

[0088] The signal processing unit 206 of each antenna system processing unit 201-z (where z is any one of 1 to Na) includes an AD conversion unit 207, a beat frequency analysis unit 208, an output switching unit 209, and a Doppler analysis unit 210.

[0089] The signal (for example, the beat signal) output from the LPF 205 is converted into discrete sample data discretely sampled by the AD conversion unit 207 in the signal processing unit 206.

[0090] The beat frequency analysis unit 208 calculates N data The discrete sample data are subjected to FFT processing. As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at a beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). Note that the beat frequency analysis unit 208 may perform the FFT processing by multiplying a window function coefficient such as a Han window or a Hamming window. Note that the radar device 10 can suppress side lobes that occur around the beat frequency peak by using the window function coefficient. In addition, the N data When the number of discrete sampling data is not a power of two, the beat frequency analysis unit 208 may perform FFT processing as an FFT size of a power of two by including zero-padded data, for example.

[0091] Here, the beat frequency response output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 obtained by transmitting the m-th chirp pulse is defined as RFT z (f b , m), where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,…,(N data / 2)-1, z = 1, …, Na, m = 1, …, N C The beat frequency index f b The smaller the beat frequency, the smaller the delay time of the reflected wave signal (in other words, the closer the distance to the target).

[0092] Also, the beat frequency index f b is calculated by the following equation (8): b ) into the beat frequency index f b Let "distance index f b " is also called.

number

[0093] Here, B w represents the frequency modulation bandwidth within the range gate in the chirp signal, and C0 represents the speed of light.

[0094] Based on the orthogonal code element index OC_INDEX output from the code generation unit 104, the output switching unit 209 selectively switches and outputs the output of the beat frequency analysis unit 208 for each transmission period to the OC_INDEX-th Doppler analysis unit 210 among the Loc Doppler analysis units 210. In other words, the output switching unit 209 selects the OC_INDEX-th Doppler analysis unit 210 in the m-th transmission period Tr.

[0095] The signal processing unit 206 includes Loc Doppler analysis units 210-1 to 210-Loc. For example, data is input to the noc-th Doppler analysis unit 210 every Loc transmission periods (Loc×Tr) by the output switching unit 209. Therefore, the noc-th Doppler analysis unit 210 uses the data of Ncode transmission periods out of Nc transmission periods (for example, the beat frequency response RFT z (f b , m)) to perform Doppler analysis for each distance index f b . Here, noc is the index of the code element, and noc = 1,..., Loc.

[0096] For example, when Ncode is a power of 2, FFT processing may be applied in the Doppler analysis. In this case, the FFT size is Ncode, and the maximum Doppler frequency at which no aliasing occurs derived from the sampling theorem is ±1 / (2Loc×Tr). Also, the Doppler frequency interval of the Doppler frequency index f s is 1 / (Ncode×Loc×Tr), and the range of the Doppler frequency index f s is f s = -Ncode / 2,..., 0,..., Ncode / 2 - 1.

[0097] For example, the output VFT of the Doppler analysis unit 210 of the z-th signal processing unit 206 z noc (f b , f s ) is shown in the following equation (9). Here, j is the imaginary unit, and z = 1 to Na.

Equation

[0098] Also, when Ncode is not a power of 2, for example, zero-padding data can be included to perform FFT processing with a data size (FFT size) of a power of 2. For example, when the FFT size in the Doppler analysis unit 210 including zero-padding data is N codewzero when the output VFT of the Doppler analysis unit 210 in the z-th signal processing unit 206 z noc (f b , f s ) is shown in the following equation (10).

Equation

[0099] Here, noc is the index of the symbol element, and noc = 1,..., Loc. Also, the FFT size is N codewzero and the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1 / (2Loc×Tr). Also, the Doppler frequency interval of the Doppler frequency index f s is 1 / (N codewzero ×Loc×Tr), and the range of the Doppler frequency index f s is f s =-N codewzero / 2,..., 0,..., N codewzero / 2 - 1.

[0100] Hereinafter, as an example, the case where Ncode is a power of 2 will be described. When zero-padding is used in the Doppler analysis unit 210, Ncode is replaced with N in the following description codewzeroBy replacing it, it can be similarly applied and the same effects can be obtained.

[0101] Also, the Doppler analysis unit 210 may multiply, for example, a window function coefficient such as a Han window or a Hamming window during the FFT process. The radar device 10 can suppress side lobes generated around the beat frequency peak by applying the window function.

[0102] The processing in each component of the signal processing unit 206 has been described above.

[0103] In FIG. 6, the CFAR unit 211 performs CFAR processing (in other words, adaptive threshold determination) using the outputs of the Loc Doppler analysis units 210 of the first to Nath signal processing units 206, and gives a distance index f b_cfar and a Doppler frequency index f s_cfar for the peak signal.

[0104] The CFAR unit 211, for example, as shown in the following equation (11), performs power addition on the outputs VFT z noc (f b , f s ) of the Doppler analysis units 210 of the first to Nath signal processing units 206, and performs a two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity), or a CFAR processing combining one-dimensional CFAR processing. For the CFAR processing combining two-dimensional CFAR processing or one-dimensional CFAR processing, for example, the processing disclosed in Non-Patent Document 3 may be applied.

Equation

[0105] The CFAR unit 211 adaptively sets a threshold value, and outputs a distance index f b_cfar , a Doppler frequency index f s_cfar , and received power information PowerFT(f b_cfar , f s_cfar ) to the symbol multiplexing separation unit 212.

[0106] Next, an operation example of the code multiplexing separation unit 212 will be described.

[0107] The code multiplexing separation unit 212 performs separation processing of the code multiplexed signal based on, for example, the distance index f b_cfar and the Doppler frequency index f s_cfar extracted in the CFAR unit 211.

[0108] For example, the code multiplexing separation unit 212 performs code separation processing on the Doppler component VFTALL b_cfar corresponding to the distance index f s_cfar and the Doppler frequency index f z (f b_cfar , f s_cfar ) extracted in the CFAR unit 211 as shown in the following equation (12).

Equation

[0109] Here, DeMul z ncm (f b_cfar , f s_cfar ) is the output of the Doppler analysis unit 210 in the z-th antenna system processing unit 201 for the distance index f b_cfar and the Doppler frequency index f s_cfar , which is the output obtained by separating the code multiplexed signal using the orthogonal code Code ncm . Note that z = 1,..., Na and ncm = 1,..., N CM . Also, in Equation (12),

Equation

[0110] In Equation (12), α(f s_cfar ) represents the "Doppler phase correction vector". The Doppler phase correction vector α(f s_cfar ) corrects the Doppler phase rotation caused by the time difference in Doppler analysis among Loc Doppler analysis units 210 when the Doppler frequency index f s_cfar extracted in the CFAR unit 211 is within the output range (in other words, the Doppler range) of the Doppler analysis unit 210 that does not include Doppler folding.

[0111] For example, the Doppler phase correction vector α(f s_cfar ) is expressed as the following Equation (14). The Doppler phase correction vector α(f s_cfar ) shown in Equation (14) is a vector having, as elements, Doppler phase correction coefficients that correct the phase rotation of the Doppler component of the Doppler frequency index f z 1 (f b_cfar , f s_cfar ) of the output VFT z 2 (f b_cfar , f s_cfar ) of the second Doppler analysis unit 210 to the phase rotation caused by the time delays of Tr, 2Tr,..., (Loc - 1)Tr in the outputs VFT z Loc (f b_cfar , f s_cfar ) from the second to the Loc-th Doppler analysis unit 210, with reference to the Doppler analysis time of the output VFT s_cfar of the first Doppler analysis unit 210. [Number]

[0112] Also, in Equation (12), VFTALL z (f b_cfar , f s_cfar ) is, for example, as in the following Equation (15), the output VFT of the Loc Doppler analysis units 210 in the z-th antenna system processing unit 201 z noc (f b , f s ) among which, the distance index f and Doppler frequency index f b_cfar extracted by the CFAR unit 211 s_cfar and the component VFT corresponding to z noc (f b_cfar , f s_cfar )(where noc = 1,…, Loc) are represented in vector form. [Number]

[0113] The operation example of the symbol multiplexing separation unit 212 has been described above. The configuration shown in FIG. 6 is such that the maximum Doppler frequency without aliasing derived from the sampling theorem is ±1 / (2Loc×Tr), and the operation of the symbol multiplexing separation unit 212 assuming that the targets detected by the radar device 10 are within this range has been described.

[0114] Note that the configuration of the radar device 10 is not limited to the configuration shown in FIG. 6, and the detectable Doppler frequency range can also be further expanded. For example, a folding determination unit may be provided to determine whether the output of the Doppler analysis unit disclosed in FIG. 1 of Patent Document 1 includes a Doppler frequency component exceeding the maximum Doppler frequency ±1 / (2Loc×Tr), perform a folding determination process, and use the determination result to perform symbol multiplexing separation in the symbol multiplexing separation unit.

[0115] However, in order to perform the folding determination process in the folding determination unit of Patent Document 1, the code multiplexing number N of the code generated by the code generation unit in the radar transmission unit CM is set to be less than the number of orthogonal codes N allcode , and N CM < N allcode is satisfied. In other words, the code length Loc of the orthogonal code is made larger than the code multiplexing number N CM .

[0116] By using such a configuration, the detectable Doppler range can be further expanded. For example, the maximum detectable Doppler frequency can be set to ±1 / (2×Tr). Therefore, the operation of the code multiplex separation unit assuming that the targets detected by the radar device are within the Doppler frequency range of ±1 / (2×Tr) becomes possible.

[0117] In the radar device 10, for example, the arrangement of the transmission antenna 106 and the reception antenna 202 that can suppress the grating lobe or the side lobe and enhance the angular resolution by improving the array gain and increasing the aperture length by the virtual reception array may be adopted.

[0118] Hereinafter, an example of the antenna arrangement of the transmission antenna 106 and the reception antenna 202, and an example of the direction estimation process in the direction estimation unit 213 when each arrangement example is applied will be described.

[0119] Also, in the following arrangement examples and modification examples, the arrangement of the transmission antenna 106 may be replaced with the arrangement of the reception antenna 202, or the arrangement of the reception antenna 202 may be replaced with the arrangement of the transmission antenna 106. In the radar device 10, even when the antenna arrangements of the transmission antenna 106 and the reception antenna 202 are interchanged, the same effects as the following arrangement examples can be obtained.

[0120] Also, arrangements in which the horizontal direction and the vertical direction in the following arrangement examples and modification examples are interchanged may be used. When the horizontal direction and the vertical direction are interchanged in the antenna arrangement, the radar device 10 can obtain the effects of interchanging the horizontal direction and the vertical direction in the following arrangement examples.

[0121] Note that the horizontal and vertical directions in the arrangement example do not necessarily exactly coincide with the horizontal and vertical directions. While maintaining the relative positional relationship between the transmitting antenna and the receiving antenna included in the arrangement example, the entire arrangement example may be arranged at a predetermined angle. Even in this case, since the relative positional relationship between the transmitting antenna and the receiving antenna included in the arrangement example is maintained, the same effect can be obtained.

[0122] The antenna arrangement (for example, MIMO antenna arrangement) of the radar device 10 may be an arrangement that satisfies the following arrangement conditions, for example.

[0123] [Arrangement Condition 1] N Tx The N transmitting antennas 106 are arranged in a predetermined arrangement direction at intervals of one wavelength or more. When three or more antennas are arranged, they may be arranged at equal intervals. Note that Tx a part of the N transmitting antennas 106 may be arranged at different intervals. Also, the radar device 10 may include transmitting antennas other than the N Tx transmitting antennas 106.

[0124] The Na receiving antennas 202 include a "first diagonal antenna group" arranged in the "first diagonal direction" and a "second diagonal antenna group" arranged in the "second diagonal direction", and the first diagonal direction and the second diagonal direction are not parallel. In other words, the first diagonal direction and the second diagonal direction are different directions. Note that the radar device 10 may include receiving antennas other than the Na receiving antennas 202. Also, a part of the Na receiving antennas 202 may be arranged at different intervals.

[0125] Note that each of the first diagonal antenna group and the second diagonal antenna group may include at least two receiving antennas 202.

[0126] Further, each of the first diagonal direction and the second diagonal direction may be a direction that does not coincide with a predetermined arrangement direction of the transmission antenna 106. In other words, the first diagonal direction (corresponding to, for example, the first direction) in which the first diagonal antenna group (corresponding to, for example, the first antenna group) is arranged, the second diagonal direction (corresponding to, for example, the second direction) in which the second diagonal antenna group (corresponding to, for example, the second antenna group) is arranged, and the direction (corresponding to, for example, the third direction) in which a plurality (for example, N Tx pieces) of transmission antennas 106 are arranged may be different from each other.

[0127] By arranging the first diagonal antenna group and the second diagonal antenna group that satisfy Arrangement Condition 1 at arbitrary positions, it is possible to suppress grating lobes. For example, as shown in the following arrangement example or modified example, by arranging the first diagonal antenna group and the second diagonal antenna group so that their horizontal positions do not overlap, it becomes possible to arrange antenna elements with a large vertical size.

[0128] Hereinafter, an example of Arrangement Condition 1 will be described. Hereinafter, an arrangement example that satisfies Arrangement Condition 1 and an example of the direction estimation result by computer simulation in the arrangement example will be described.

[0129] Note that hereinafter, a case where the direction in which a plurality of transmission antennas 106 are arranged coincides with the horizontal direction will be described as an example, but the arrangement direction of the transmission antennas 106 is not limited to the direction that coincides with the horizontal direction. For example, in Modified Example 8 of Arrangement Example 1 described later, an arrangement example in the case of a direction different from the horizontal direction is shown.

[0130] <Arrangement Example 1> FIG. 8 is a diagram showing an arrangement example (for example, a MIMO antenna arrangement example) of the transmission antenna 106 (for example, represented as Tx) and the reception antenna 202 (for example, represented as Rx) according to Arrangement Condition 1. In FIG. 8, the scales on the horizontal axis and the vertical axis are, for example, the basic interval D in the horizontal direction H , and the basic interval D in the vertical direction VLet it be so. Note that the scales on the horizontal and vertical axes are the same for the MIMO antenna arrangements in the following other examples. As an example, D H and D V may be at an interval of 0.5 wavelength.

[0131] In the example shown in FIG. 8, the number of transmitting antennas N Tx is 6 (for example, Tx#1, Tx#2, Tx#3, Tx#4, Tx#5, and Tx#6), and the number of receiving antennas Na is 8 (for example, Rx#1, Rx#2, Rx#3, Rx#5, Rx#6, Rx#7, and Rx#8).

[0132] In FIG. 8, N Tx = 6 transmitting antennas Tx#1 to #6 are arranged at equal intervals in the horizontal direction (for example, a predetermined arrangement direction) at an interval of 1.5 wavelengths. In other words, in Arrangement Example 1, all of the plurality (for example, N Tx pieces) of transmitting antennas 106 may be arranged in a predetermined direction (for example, corresponding to the third direction). Also, in Arrangement Example 1, for example, the interval between adjacent transmitting antennas among the plurality of transmitting antennas 106 may be an interval of one wavelength or more of the radar transmission signal.

[0133] Also, in FIG. 8, Na = 8 receiving antennas Rx#1 to #8 include a first diagonal antenna group Rx#1 to #4 arranged in a first diagonal direction and a second diagonal antenna group Rx#5 to #8 arranged in a second diagonal direction. Here, in FIG. 8, the first diagonal direction and the second diagonal direction are not parallel but different directions, satisfying Arrangement Condition 1. Also, as shown in FIG. 8, the first diagonal direction, the second diagonal direction, and the arrangement direction (for example, the horizontal direction) of the transmitting antennas 106 are not parallel to each other but different. Also, for example, as shown in FIG. 8, the first diagonal direction and the second diagonal direction are different directions with respect to the vertical direction and the horizontal direction.

[0134] For example, the first diagonal antenna groups Rx#1 to #4 shown in FIG. 8 are shifted horizontally at intervals of 0.5 wavelengths from left to right in the figure and simultaneously shifted downward at intervals of 0.5 wavelengths vertically. Also, the second diagonal antenna groups Rx#5 to #8 shown in FIG. 8 are shifted horizontally at intervals of 0.5 wavelengths from right to left in the figure and simultaneously shifted downward at intervals of 0.5 wavelengths vertically.

[0135] Thus, in FIG. 8, the antenna arrangement of the first diagonal antenna group arranged in the first diagonal direction and the antenna arrangement of the second diagonal antenna group arranged in the second diagonal direction are in a line-symmetrical relationship with respect to a line perpendicular to the third direction or a line parallel to the vertical direction. In other words, the first diagonal antenna groups Rx#1 to #4 and the second diagonal antenna groups Rx#5 to #8 are arranged in a horizontally inversion-symmetrical (or also called left-right inversion-symmetrical or mirror-symmetrical) arrangement.

[0136] Also, in FIG. 8, in each of the plurality of transmission antennas Tx#1 to #6, the first diagonal antenna groups Rx#1 to #4, and the second diagonal antenna groups Rx#5 to #8, the intervals between adjacent antennas are equal.

[0137] FIG. 9 is a diagram showing an example of the arrangement of a virtual reception array obtained by the antenna arrangement shown in FIG. 8. In FIG. 9, the scales on the horizontal axis and the vertical axis are, for example, the basic interval D in the horizontal direction H , and the basic interval D in the vertical direction V respectively. Note that the scales on the horizontal axis and the vertical axis are the same for the virtual reception array arrangements in the following other examples.

[0138] Here, the arrangement of the virtual reception array may be expressed as in the following formula (16) based on, for example, the positions (e.g., the positions of the feeding points) of the transmission antennas 106 constituting the transmission array antenna and the positions (e.g., the positions of the feeding points) of the reception antennas 202 constituting the reception array antenna.

Equation

[0139] Here, the position coordinates of the transmission antenna 106 (e.g., Tx#n) that constitutes the transmission array antenna are (X T_#n , Y T_#n )(e.g., n = 1,.., N Tx ), the position coordinates of the reception antenna 202 (e.g., Rx#m) that constitutes the reception array antenna are (X R_#m , Y R_#m )(e.g., m = 1,.., Na), and the position coordinates of the virtual antenna VA#k that constitutes the virtual reception array are (X V_#k , Y V_#k )(e.g., k = 1,.., N Tx ×Na).

[0140] Note that in Equation (16), for example, VA#1 is represented as the position reference (0,0) of the virtual reception array.

[0141] For example, from the arrangements of the transmission antennas Tx#1 to Tx#6 and the reception antennas Rx#1 to Rx#8 as shown in FIG. 8, the position coordinates of the virtual antennas VA#1 to #48 that constitute the virtual reception array antenna are calculated from Equation (16). As an example, the position coordinates of the virtual antennas VA#1 to #16 are (X V_#1 , Y V_#1 ) = (0,0), (X V_#2 , Y V_#2 ) = (D H , -D V ), (X V_#3 , Y V_#3 ) = (2D H , -2D V ), (X V_#4 , Y V_#4 ) = (3D H , -3D V ), (X V_#5 , Y V_#5 ) = (18D H , 0), (X V_#6 , Y V_#6 ) = (17D H , -D V ), (X V_#7 , Y V_#7 ) = (16D H , -2D V ), (X V_#8 , YV_#8 ) = (15D H , -3D V ), (X V_#9 , Y V_#9 ) = (3D H , 0), (X V_#10 , Y V_#10 ) = (4D H , -D V ), (X V_#11 , Y V_#11 ) = (5D H , -2D V ), (X V_#12 , Y V_#12 ) = (6D H , -3D V ), (X V_#13 , Y V_#13 ) = (21D H , 0), (X V_#14 , Y V_#14 ) = (20D H , -D V ), (X V_#15 , Y V_#15 ) = (19D H , -2D V ), (X V_#16 , Y V_#16 ) = (18D H , -3D V ) is obtained.

[0142] In addition, in FIG. 9, VA#16 and VA#44 are arranged overlappingly at the same position. Also, VA#8 and VA#36 are arranged overlappingly at the same position.

[0143] Here, for the cases of FIGS. 8 and 9, the cases where 0.5λ is set for D H and D V will be described. For example, they may be set to values in the range of about 0.45λ to 0.8λ respectively (for example, any value in the range from 0.5 times to 0.8 times the wavelength of the radar transmission signal). D H and D V may be set according to the horizontal or vertical field of view angle of the radar device 10 respectively. For example, when the horizontal or vertical field of view angle is in the range of about ±70 degrees to 90 degrees (wide field of view angle), D H or D VIt may be about 0.5λ. Alternatively, in the case of a narrow viewing angle with a horizontal or vertical viewing angle in the range of ±20 degrees to 40 degrees, D H Alternatively, D V May be set at a wider interval, for example, about 0.7λ. D H And D V The setting of is the same for the following arrangement examples (or modified examples). Note that λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, when a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency in the frequency sweep band of the chirp signal.

[0144] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described antenna arrangement is applied will be described.

[0145] In FIG. 1, the direction estimation unit 213 performs a direction estimation process of the target based on the code separation result DeMul b_cfar And the Doppler frequency index f s_cfar Of the output of the Doppler analysis unit 210 corresponding to z ncm (f b_cfar , f s_cfar ).

[0146] For example, the direction estimation unit 213 generates a virtual reception array correlation vector h(f b_cfar , f s_cfar ) and performs a direction estimation process.

[0147] The virtual reception array correlation vector h(f b_cfar , f s_cfar ) includes N Tx Which is the product of the number of transmission antennas N Tx ×Na elements. The virtual reception array correlation vector h(f b_cfar , f s_cfar ) is used for a process of performing direction estimation based on the phase difference between each reception antenna 202 with respect to the reflected wave signal from the target. Here, z = 1,..., Na.

[0148] For example, in the MIMO antenna arrangement of Arrangement Example 1, in the example of FIG. 8, from N Tx = 6 and Na = 8, the virtual reception array correlation vector h(f b_cfar , f s_cfar ) includes 48 elements, each corresponding to the received signal at VA#1 to VA48 in the virtual reception array arrangement shown in FIG. 9. For example, VA#1 corresponds to the first element DeMul1 b_cfar , f s_cfar ) of the column vector elements of h(f 1 (f b_cfar , f s_cfar ). Similarly, the second element corresponds to the received signal of VA#2,..., and the 48th element corresponds to the received signal of VA#48, respectively.

Number

[0149] Next, the direction estimation unit 213 performs direction estimation processing in the horizontal direction and the vertical direction, for example, using the virtual reception array correlation vector h(f b_cfar , f s_cfar ) which is the received signal of the virtual reception array composed of the above-described transmission and reception antenna arrangements.

[0150] For example, the direction estimation unit 213 multiplies the virtual reception array correlation vector h(f b_cfar , f s_cfar ) by the array correction value h_cal [y] that corrects the phase deviation and amplitude deviation between the transmission array antennas and between the reception array antennas, as shown in the following equation (18), to output the virtual reception array correlation vector h _after_cal (f b_cfar , f s_cfar ) with the inter-antenna deviation corrected. Then, the direction estimation unit 213 performs direction estimation processing in the horizontal direction and the vertical direction based on the phase difference between the reception antennas of the incoming reflected wave. Here, y = 1,.., (N Tx ×Na).

Number

[0151] Note that CA is an (N × Na) square matrix including an array correction coefficient for correcting the phase deviation and amplitude deviation between transmission antennas and between reception antennas and a coefficient for reducing the influence of the element - to - element coupling between antennas. When the coupling between the antennas of the virtual reception array can be ignored, CA becomes a diagonal matrix, and the diagonal components include the array correction value h_cal for correcting the phase deviation and amplitude deviation between transmission antennas and between reception antennas. Tx ×Na) square matrix. When the coupling between the antennas of the virtual reception array can be ignored, CA becomes a diagonal matrix, and the diagonal components include the array correction value h_cal for correcting the phase deviation and amplitude deviation between transmission antennas and between reception antennas. [y] is included.

[0152] The virtual reception array correlation vector h _after_cal (f b_cfar , f s_cfar ) after correcting the inter - antenna deviation is a column vector consisting of N × Na elements. In the following, each element is expressed as follows and used in the explanation of the direction estimation process. Note that each element is a complex number value and represents the amplitude component and phase component received by each virtual reception antenna. Tx ×Na elements. In the following, each element is expressed as follows and used in the explanation of the direction estimation process. Note that each element is a complex number value and represents the amplitude component and phase component received by each virtual reception antenna. [Mathematics]

[0153] The direction estimation unit 213 performs direction estimation in the horizontal and vertical directions using the virtual reception array correlation vector h _after_cal (f b_cfar , f s_cfar ) after correcting the inter - antenna deviation. In the direction estimation in the horizontal and vertical directions, the direction estimation unit 213 calculates a spatial profile by making the azimuth direction θ and the elevation angle direction Φ in the arrival direction estimation evaluation function value P(θ, Φ, f b_cfar , f s_cfar ) variable within a specified angular range. The direction estimation unit 213 extracts a predetermined number of maximum peak directions of the calculated spatial profile in descending order, and outputs the azimuth direction and elevation angle direction of each maximum peak as the arrival direction estimation value (for example, the positioning output).

[0154] Incidentally, there are various methods for the arrival direction estimation evaluation function value P(θ, Φ, f b_cfar , f s_cfar ). For example, the estimation method using an array antenna disclosed in Non-Patent Document 4 may be used.

[0155] For example, the beamformer method can be expressed as the following equation (19). Here, the superscript H is the Hermitian transpose operator. Other methods such as Capon and MUSIC can also be applied in the same way.

Equation

[0156] Here, the azimuth direction θ u is a vector obtained by changing θmin to θmax within the azimuth range for arrival direction estimation at an azimuth interval β1. For example, θ u is set as follows. θ u = θmin + uβ1, u = 0, …, NU NU = floor[(θmax - θmin) / β1] Here, floor(x) is a function that returns the largest integer value not exceeding the real number x.

[0157] Also, the elevation direction Φ v is a vector obtained by changing Φmin to Φmax within the azimuth range for arrival direction estimation at an azimuth interval β2. For example, Φ v is set as follows. Φ v = Φmin + vβ2, v = 0, …, NV NV = floor[(Φmax - Φmin) / β2]

[0158] Incidentally, in this embodiment, the radar device 10 may pre-calculate the direction vector a(θ Tx ×Na) based on, for example, virtual reception array arrangements VA#1, …, VA#(N u , Φ v ). Here, the direction vector a(θ u, Φ v ) is an (N Tx × Na) column vector below, with the complex response of the virtual receiving array antenna when radar reflected waves arrive from the azimuth direction θ and the elevation angle direction Φ as elements. The complex response a(θ u , Φ v ) represents the phase difference calculated geometrically with the element spacing between antennas.

[0159] Here, as an example, for the antenna surface shown in Arrangement Example 1, the perpendicular direction to the front is used as the reference (azimuth θ = 0 degrees, elevation angle Φ = 0 degrees).

[0160] Next, an example of the direction estimation result (computer simulation result) when applying the antenna arrangement according to Arrangement Example 1 described above will be described.

[0161] FIG. 10 shows the MIMO array arrangement (D H = 0.5λ, D V = 0.5λ) of Arrangement Example 1, and shows the direction estimation result when using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213. In FIG. 10, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90 degrees range and the vertical direction ±90 degrees range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted. Here, the result when each transmitting antenna and receiving antenna alone is omnidirectional is shown, and the direction estimation results (computer simulation results) in the following other examples also show the results when they are omnidirectional.

[0162] Note that (a) in FIG. 10 is a diagram showing the normalized power value in a two-dimensional direction with the horizontal axis as the horizontal direction and the vertical axis as the vertical direction in a grayscale color map. Also, (b) in FIG. 10 is a diagram showing (a) in FIG. 10, with the horizontal axis as the horizontal direction and the vertical axis as the normalized power value, and showing the normalized power value in a grayscale color map. In FIG. 10, the normalized power value may be shown, for example, as a decibel value (dB) normalized by the peak power, and the same applies to the plots of the direction estimation results in the following other examples.

[0163] Here, in Arrangement Example 1 shown in FIG. 8, the transmission antennas 106 are arranged at intervals of 1.5 wavelengths (1.5λ) in the horizontal direction, the reception antennas 202 are arranged at intervals of 6 wavelengths or more in the horizontal direction, and each virtual antenna in the virtual reception array arrangement shown in FIG. 9 is arranged at intervals of 1 wavelength or more in the horizontal direction. Therefore, it is an antenna interval at which grating lobes can occur. For example, when the target direction is 0 degrees in the horizontal direction, grating lobes can occur at -41.8 degrees and 41.8 degrees in the horizontal direction.

[0164] In Arrangement Example 1, even if the arrangement of the reception antennas 202 is arranged at intervals of 6.5 wavelengths or more in the horizontal direction, for example, and the virtual antennas in the horizontal direction of the virtual reception array arrangement are arranged at intervals of 1 wavelength or more, the grating lobes can be suppressed. For example, as shown in FIG. 10, it can be seen that the grating lobes are suppressed in a direction different from the peak direction of the target true value direction.

[0165] Hereinafter, the principle of suppressing grating lobes by the MIMO antenna arrangement in Arrangement Example 1 will be described.

[0166] FIG. 11 shows the antenna arrangement (hereinafter referred to as "Comparison Arrangement 1") when using the first diagonal antenna groups Rx#1 to #4 among the reception antennas 202 of Arrangement Example 1 shown in FIG. 8 for comparison with Arrangement Example 1. FIG. 12 shows the direction estimation result using the beamformer method when Comparison Arrangement 1 is applied. In FIG. 12, similar to FIG. 10, the output of the arrival direction estimation evaluation function value in the horizontal direction range of ±90 degrees and the vertical direction range of ±90 degrees when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0167] Note that the virtual reception array arrangement when using the first diagonal antenna groups Rx#1 to #4 among the reception antennas 202 of Arrangement Example 1, like Comparison Arrangement 1, corresponds to VA#1 to #4, #9 to #12, #17 to #20, #25 to #28, #33 to #36, #41 to #44 in FIG. 9.

[0168] Similarly, for comparison with Arrangement Example 1, FIG. 13 shows the antenna arrangement (hereinafter referred to as "Comparison Arrangement 2") when the second diagonal antenna group Rx#5 to #8 among the receiving antennas 202 of Arrangement Example 1 shown in FIG. 8 is used. Further, FIG. 14 shows the direction estimation result using the beamformer method when Comparison Arrangement 2 is applied. In FIG. 14, similar to FIG. 10, the output of the arrival direction estimation evaluation function value in the horizontal direction range of ±90 degrees and the vertical direction range of ±90 degrees when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0169] Note that the virtual reception array arrangement when the second diagonal antenna group Rx#5 to #8 among the receiving antennas 202 of Arrangement Example 1 is used, as in Comparison Arrangement 2, corresponds to VA#5 to #8, #13 to #16, #21 to #24, #29 to #32, #37 to #40, #45 to #48 in FIG. 9.

[0170] For example, as in Comparison Arrangement 1 shown in FIG. 11, when the first diagonal antenna group Rx#1 to #4 among the receiving antennas 202 of Arrangement Example 1 shown in FIG. 8 is used, for the target true value (for example, horizontal 0 degrees, vertical 0 degrees), in the direction estimation result (for example, FIGS. 12(a) and (b)) using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213, grating lobes occur in two directions (horizontal direction -41.8 degrees, vertical direction -41.8 degrees), and (horizontal direction +41.8 degrees, vertical direction +41.8 degrees).

[0171] Also, for example, as in Comparison Arrangement 2 shown in FIG. 13, when the second diagonal antenna group Rx#5 to #8 among the receiving antennas 202 of Arrangement Example 1 shown in FIG. 8 is used, for the target true value (for example, horizontal 0 degrees, vertical 0 degrees), in the direction estimation result (for example, FIGS. 14(a) and (b)) using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213, grating lobes occur in two directions (horizontal direction -41.8 degrees, vertical direction +41.8 degrees), and (horizontal direction +41.8 degrees, vertical direction -41.8 degrees).

[0172] Here, the arrangement directions of the receiving antennas Rx#1 to #4 (for example, corresponding to the first diagonal antenna group) of the comparison arrangement 1 shown in FIG. 11 and the arrangement directions of the receiving antennas Rx#5 to #8 (for example, corresponding to the second diagonal antenna group) of the comparison arrangement 2 shown in FIG. 13 are different and not parallel. Therefore, as shown in FIGS. 12 and 14, in the comparison arrangement 1 and the comparison arrangement 2, the horizontal and vertical two-dimensional angular directions in which grating lobes are generated do not coincide and have the property of shifting.

[0173] On the other hand, as shown in FIGS. 12 and 14, in the comparison arrangement 1 and the comparison arrangement 2, the angular directions (for example, horizontal 0 degrees, vertical 0 degrees) of the main lobes corresponding to the target true values coincide.

[0174] Therefore, as shown in FIG. 8, in the arrangement example 1 including the first diagonal antenna and the second diagonal antenna, the grating lobes generated in the comparison arrangement 1 including the first diagonal antenna group and the grating lobes generated in the comparison arrangement 2 including the second diagonal antenna group do not coincide in their respective generation directions (two-dimensional angular directions), and are likely to be dispersed. For this reason, in the arrangement example 1, as shown in FIGS. 10(a) and 10(b), the peak level in the grating lobe direction is likely to be suppressed compared to the peak in the target true value direction.

[0175] For example, as shown in FIG. 8, when the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion-symmetric, the virtual receiving array arrangements corresponding to the comparison arrangement 1 and the comparison arrangement 2 are horizontally inversion-symmetric. As a result, in each of the comparison arrangement 1 and the comparison arrangement 2, the horizontal and vertical two-dimensional directions in which grating lobes are generated are horizontally inversion-symmetric, and as shown in FIGS. 12 and 14, it can be seen that the shift in the horizontal and vertical two-dimensional angular directions in which grating lobes are generated becomes larger.

[0176] Therefore, in Arrangement Example 1, for example, as shown in FIG. 8, when the arrangement directions (for example, diagonal directions) of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion-symmetrical, as shown in FIG. 10, the directions in which grating lobes are generated are horizontally inversion-symmetrical, and the interval (or deviation) between the directions of the suppressed grating lobes tends to be larger.

[0177] Such an arrangement in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion-symmetrical is more suitable, for example, as the number of antennas of the radar device 10 is smaller. For example, as the number of antennas of the radar device 10 is smaller, the beam width of the main beam in direction estimation tends to be wider. For this reason, when the directions of the suppressed grating lobes are close to each other, as the number of antennas of the radar device 10 is smaller, due to the widening of the beam width, the grating lobe powers overlap, and the power of the grating lobes can increase. For this reason, as the number of antennas of the radar device 10 is smaller, the suppression performance of the grating lobes deteriorates, and the probability of false detection in the radar device 10 tends to increase. Therefore, when the number of antennas of the radar device 10 is small, for example, by an arrangement in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion-symmetrical, the overlap of the grating lobe powers can be suppressed, so that the suppression performance of the grating lobes can be improved.

[0178] Also, as shown in FIG. 8, Arrangement Example 1 is an arrangement in which the transmission antennas 106 are arranged in a row in the horizontal direction and the reception antennas 202 are arranged in a row in the diagonal direction. In other words, as shown in FIG. 8, in Arrangement Example 1, both the transmission antennas 106 and the reception antennas 202 are arranged such that the antenna elements do not overlap in the vertical direction. For this reason, in Arrangement Example 1, it is possible to arrange antenna elements having a larger size in the vertical direction (for example, a size of one wavelength or more).

[0179] Therefore, in Arrangement Example 1, for example, by using a subarray antenna configured by arranging a plurality of antenna elements in the vertical direction and narrowing the directivity in the vertical direction, the antenna gain in the vertical direction can be improved.

[0180] Note that the distance between the transmission antenna 106 and the reception antenna 202 may be sufficiently wider than the antenna element size, or may be arranged such that the vertical directions do not overlap and are shifted horizontally.

[0181] As described above, in Arrangement Example 1, it is an antenna arrangement that can use antenna elements of any vertical direction (for example, the vertical direction) size, and is also an antenna arrangement that can suppress grating lobes generated in the virtual reception array.

[0182] Note that each of the first diagonal antenna group and the second diagonal antenna group shown in FIG. 8 may be arranged at any location, and a similar grating lobe suppression effect can be obtained. For example, in Arrangement Example 1, the arrangements of the first diagonal antenna group Rx#1 to Rx#4 and the second diagonal antenna group Rx#5 to Rx#8 are set such that their horizontal positions do not overlap, so that it is possible to arrange antenna elements with a larger vertical size.

[0183] As described above, an example of the direction estimation result (computer simulation result) in Arrangement Example 1 and the effects of Arrangement Example 1 have been described.

[0184] In FIG. 6, the direction estimation unit 213 outputs, for example, the direction estimation result, and further, as the positioning result, distance information based on the distance index f b_cfar (for example, information converted based on Equation (8)), and Doppler velocity information of the target based on the Doppler frequency index f s_cfar of the target. The direction estimation unit 213 may output the positioning result to, for example, a vehicle control device (not shown) in the case of an in-vehicle radar or an infrastructure control device in the case of an infrastructure radar.

[0185] Doppler frequency index f s_cfar to the relative velocity component v d (f s_cfar) To convert it, the following equation (20) may be used for conversion. Here, λ is the wavelength of the carrier frequency of the RF signal output from the transmission radio section (not shown). Also, Δ f is the Doppler frequency interval in the FFT process in the Doppler analysis section 210. For example, in the present embodiment, Δ f = 1 / {Loc × N code × T r}.

Equation

[0186] The operation example of the radar device 10 has been described above.

[0187] As described above, in Arrangement Example 1, in the radar device 10, the receiving antenna 202 includes, for example, a first diagonal antenna group arranged in a first diagonal direction and a second diagonal antenna group arranged in a second diagonal direction. Also, in the antenna arrangement of the radar device 10, the first diagonal direction, the second diagonal direction, and the predetermined direction (for example, the horizontal direction) in which the plurality of transmitting antennas 106 are arranged are different from each other.

[0188] With this antenna arrangement configuration, the radar device 10 can use antenna elements of an arbitrary vertical size (for example, the vertical size) in the MIMO array arrangement, and can suppress the grating lobes generated in the virtual receiving array.

[0189] Also, in Arrangement Example 1, as described above, due to the difference in the arrangement direction of each of the first diagonal antenna group and the second diagonal antenna group in the receiving antenna 202, a grating lobe suppression effect can be obtained. Therefore, in Arrangement Example 1, for example, the element interval of the transmitting antenna 106 can be arbitrarily set. Similarly, in Arrangement Example 1, the interval between the first diagonal antenna group and the second diagonal antenna group can be arbitrarily set. Thereby, for example, according to the setting of at least one of the element interval of the transmitting antenna 106 and the interval between the first diagonal antenna group and the second diagonal antenna group, the aperture length of the virtual receiving array can be expanded, so that the angle measurement accuracy and angle separation performance in the vertical and horizontal directions in the radar device 10 can be improved.

[0190] Therefore, according to Arrangement Example 1, the grating lobe can be suppressed and the angle measurement accuracy or resolution in the radar device 10 can be improved.

[0191] Note that in Arrangement Example 1, in at least one of the transmitting antenna 106 and the receiving antenna 202, antenna elements may be further added to the antenna configuration shown in FIG. 8. In other words, each of the transmitting antenna 106 and the receiving antenna 202 of the radar device 10 only needs to include the antenna elements arranged as shown in FIG. 8. In this case, for example, a virtual antenna is added additively at the position shown in Equation (16). For example, by adding antenna elements to at least one of the transmitting antenna 106 and the receiving antenna 202, another virtual antenna is added to the virtual receiving array arrangement shown in FIG. 9. Even in the case of the antenna arrangement including such Arrangement Example 1, the effects of Arrangement Example 1 described above are maintained, and the same effects as those of Arrangement Example 1 can be obtained.

[0192] For example, antennas may be further added to the antenna configuration of Arrangement Example 1. By adding antennas, the grating lobes or side lobe levels suppressed by Arrangement Example 1 described above are more likely to be further reduced, so that false detections during angle measurement in the radar device 10 can be reduced and the angle measurement performance can be improved. Note that the addition of antennas can be similarly applied to subsequent arrangement examples or modification examples, and the same effects can be obtained.

[0193] Also, in the MIMO array arrangement of Arrangement Example 1, an arrangement in which the horizontal direction and the vertical direction are interchanged may be applied. In this case, for the virtual reception array arrangement, an arrangement in which the horizontal direction and the vertical direction are interchanged is obtained, and angular separation performance in which the horizontal direction and the vertical direction are interchanged is obtained. Note that the interchange of the horizontal direction and the vertical direction of the MIMO array arrangement can be similarly applied to the subsequent arrangement examples or modification examples, and for the virtual reception array arrangement in the subsequent arrangement examples, an arrangement in which the horizontal direction and the vertical direction are interchanged is obtained.

[0194] Hereinafter, a modification example of Arrangement Example 1 will be described.

[0195] [Modification Example 1 of Arrangement Example 1] In Modification Example 1 of Arrangement Example 1, for example, the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group may be wider than the aperture length of N Tx transmission antennas 106.

[0196] For example, in the case of Arrangement Example 1, as shown in FIG. 8, the minimum interval (for example, the interval between Rx#4 and Rx#8) between the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 is Tx narrower than the aperture length (for example, the interval between Tx#1 and Tx#6) of N

[0197] In Modification Example 1 of Arrangement Example 1, for example, as shown in FIG. 15 (hereinafter also referred to as "Arrangement Example 1-1"), the minimum interval (for example, the interval between Rx#4 and Rx#8) between the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 is Tx may be expanded wider than the aperture length (for example, the interval between Tx#1 and Tx#6) of N

[0198] For example, in the case of Arrangement Example 1-1 shown in FIG. 15, the minimum interval (the interval between Rx#4 and Rx#8) between the first diagonal antenna group and the second diagonal antenna group is N TxIt is set to a spacing wider than the aperture lengths of the six transmission antennas 106 (for example, the spacing between Tx#1 and Tx#6). In the arrangement example 1-1 shown in FIG. 15, for settings different from the spacing between the first diagonal antenna group and the second diagonal antenna group, it may be the same as in arrangement example 1 (for example, FIG. 8).

[0199] Based on the arrangement of the transmission antennas Tx#1 to Tx#6 and the arrangement of the reception antennas Rx#1 to Rx#8 as shown in FIG. 15, the position coordinates of the virtual antennas VA#1 to #48 that constitute the virtual reception array antenna are calculated based on Equation (16).

[0200] FIG. 16 is a diagram showing an arrangement example of the virtual reception array obtained by the antenna arrangement shown in FIG. 15. As shown in FIG. 16, the aperture length of the virtual reception array in the horizontal direction is wider compared to FIG. 9.

[0201] Next, an example of the direction estimation result (computer simulation result) when applying the antenna arrangement according to the above-described arrangement example 1-1 will be described.

[0202] FIG. 17 shows the MIMO array arrangement of arrangement example 1-1 (D H = 0.5λ, D V = 0.5λ), and shows the direction estimation result when using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213. In FIG. 17, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0203] Note that FIG. 17(a) is a diagram showing the normalized power value in the two-dimensional direction where the horizontal axis is the horizontal direction and the vertical axis is the vertical direction in a grayscale color map. Also, FIG. 17(b) is a diagram showing FIG. 17(a) with the horizontal axis as the horizontal direction and the vertical axis as the normalized power value, and showing the normalized power value in a grayscale color map. In FIG. 17, the normalized power value may be shown, for example, as a decibel value (dB) normalized by the peak power.

[0204] As shown in FIGS. 17(a) and 17(b), in Arrangement Example 1-1, similar to Arrangement Example 1 (for example, FIG. 10), the peak level in the grating lobe direction is suppressed as compared with the peak in the target true value direction.

[0205] Further, in Arrangement Example 1-1, as compared with Arrangement Example 1, since the virtual reception array arrangement (for example, the aperture length of the virtual reception array) extends more in the horizontal direction, as shown in FIG. 17, the peak in the target true value direction becomes sharper in the horizontal direction as compared with FIG. 10. Therefore, it is possible to improve the angle measurement accuracy or estimation accuracy in the horizontal direction in the radar device 10.

[0206] Note that, as shown in FIG. 17, in Arrangement Example 1-1, a side lobe of about -10 dB may occur in the horizontal direction (lateral direction) of the peak in the target true value direction as compared with Arrangement Example 1 (for example, FIG. 10). The occurrence of this side lobe is caused by, for example, expanding the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group as compared with Arrangement Example 1.

[0207] Thus, in Arrangement Example 1-1, by expanding the interval between the first diagonal antenna group and the second diagonal antenna group, it is possible to improve the angle measurement accuracy or estimation accuracy in the horizontal direction, while the side lobe level in the horizontal direction (lateral direction) of the peak in the target true value direction increases. For example, according to requirements such as the detection target assumed by the radar device 10, the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group may be set within a suitable range.

[0208] Note that the arrangement directions (for example, diagonal directions) of the first diagonal antenna group and the second diagonal antenna group may be opposite to each other with respect to the arrangement in FIG. 15, each arrangement may be inverted left and right (for example, in the horizontal direction), or each arrangement may be inverted up and down (for example, in the vertical direction). Even in these cases, the same effects as those of Arrangement Example 1-1 described above can be obtained. Note that the change in the arrangement direction of each of the first diagonal antenna group and the second diagonal antenna group can be similarly applied to the subsequent arrangement examples.

[0209] As an example, FIG. 18 shows an arrangement (hereinafter referred to as "Arrangement Example 1-1a") in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group in Arrangement Example 1-1 shown in FIG. 15 are reversed from each other.

[0210] In the case of Arrangement Example 1-1 shown in FIG. 15, the first diagonal antenna group and the second diagonal antenna group are horizontally symmetrically arranged. For this reason, Arrangement Example 1-1a shown in FIG. 18 is also an arrangement in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group in Arrangement Example 1-1 are respectively reversed left and right, and is also an arrangement in which the first diagonal antenna group and the second diagonal antenna group in Arrangement Example 1-1 are respectively reversed up and down.

[0211] From the arrangements of the transmission antennas Tx#1 to Tx#6 and the reception antennas Rx#1 to Rx#8 shown in FIG. 18, the position coordinates of the virtual antennas VA#1 to #48 constituting the virtual reception array antenna are calculated based on Equation (16). For example, FIG. 19 is a diagram showing an arrangement example of the virtual reception array obtained by the antenna arrangement shown in FIG. 18.

[0212] Also, in an arrangement such as Arrangement Example 1-1 or Arrangement Example 1-1a, for example, even when the vertical size of the transmission antenna 106 is large, the reception antenna 202 can be arranged on both sides (for example, both horizontal sides) of the transmission antenna 106, so that the effect of reducing the mounting area of the antenna can also be obtained.

[0213] [Modification Example 2 of Arrangement Example 1] In Modification Example 2 of Arrangement Example 1, for example, the distance (for example, the minimum distance) between the first diagonal antenna group and the second diagonal antenna group may be made closer compared to Arrangement Example 1. Also, in Modification Example 2 of Arrangement Example 1, for example, one antenna included in the plurality of reception antennas 202 may be included in each of the first diagonal antenna group and the second diagonal antenna group in an overlapping manner. In other words, the first diagonal antenna group and the second diagonal antenna group may include one or more antennas shared therebetween.

[0214] For example, in the case of Arrangement Example 1, as shown in FIG. 8, the minimum interval between the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 (for example, the interval between Rx#4 and Rx#8) is N Tx is narrower than the aperture length of the N

[0215] In Modification Example 2 of Arrangement Example 1, for example, as shown in FIG. 20 (hereinafter referred to as "Arrangement Example 1-2a"), compared with FIG. 8, the minimum interval between the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 (for example, the interval between Rx#4 and Rx#8) may be arranged closer.

[0216] Alternatively, in Modification Example 2 of Arrangement Example 1, for example, as shown in FIG. 21 (hereinafter referred to as "Arrangement Example 1-2b"), some antennas (for example, Rx#4) of the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#4 to #7 may overlap.

[0217] For example, in the case of Arrangement Example 1-2a shown in FIG. 20, N Tx transmitting antennas Tx#1 to #6 are arranged at equal intervals in the horizontal direction at an interval of 4.5 wavelengths (for example, 9D H ), and the minimum interval between the first diagonal antenna group and the second diagonal antenna group (for example, the interval between Rx#4 and Rx#8) is set to the horizontal basic interval D H . In FIG. 20, in the horizontal direction, the aperture length (for example, 7D H ) of the receiving antennas 202 (Rx#1 to #8) is narrower than the element interval of the transmitting antennas 106 (for example, 9D H ).

[0218] Also, for example, in the case of Arrangement Example 1-2b shown in FIG. 21, N Tx transmitting antennas Tx#1 to #6 are arranged at an interval of 3.5 wavelengths (for example, 7D HThey are arranged at equal intervals in the horizontal direction. Among the seven receiving antennas Rx#1 to #7 where Na = 7, the first diagonal antenna group includes Rx#1 to #4, and the second diagonal antenna group includes Rx#4 to #7. In Fig. 21, in the horizontal direction, the aperture length of the receiving antennas 202 (Rx#1 to #7) (for example, 6D H ) is narrower than the element interval of the transmitting antenna 106 (for example, 7D H ).

[0219] Based on the arrangements of the transmitting antennas Tx#1 to Tx#6 and the receiving antennas Rx#1 to Rx#8 as shown in Fig. 20, the position coordinates of the virtual antennas VA#1 to #48 that constitute the virtual receiving array antenna are calculated based on Equation (16). Fig. 22 is a diagram showing an example of the arrangement of the virtual receiving array obtained by the antenna arrangement shown in Fig. 20.

[0220] Also, based on the arrangements of the transmitting antennas Tx#1 to Tx#6 and the receiving antennas Rx#1 to Rx#7 as shown in Fig. 21, the position coordinates of the virtual antennas VA#1 to #42 that constitute the virtual receiving array antenna are calculated based on Equation (16). Fig. 23 is a diagram showing an example of the arrangement of the virtual receiving array obtained by the antenna arrangement shown in Fig. 21.

[0221] Next, an example of the direction estimation result (computer simulation result) when applying the antenna arrangements according to the above-described Arrangement Examples 1-2a and 1-2b will be described.

[0222] Figs. 24 and 25 show the direction estimation results when using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213 with the MIMO array arrangements (D H = 0.5λ, D V = 0.5λ) of Arrangement Examples 1-2a and 1-2b, respectively. In Figs. 24 and 25, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction range of ±90 degrees and the vertical direction range of ±90 degrees when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0223] Note that FIGS. 24(a) and 25(a) are diagrams showing the normalized power values in a two-dimensional direction with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction in a grayscale color map. Further, FIGS. 24(b) and 25(b) are diagrams showing FIGS. 24(a) and 24(a), with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value, and showing the normalized power value in a grayscale color map. In FIGS. 24 and 25, the normalized power value may be represented, for example, by a decibel value (dB) normalized by the peak power.

[0224] As shown in FIGS. 24 and 25, in Arrangement Examples 1-2a and 1-2b, similar to Arrangement Example 1 (e.g., FIG. 10), the peak level in the grating lobe direction is suppressed as compared with the peak in the target true value direction.

[0225] In arrangements such as Arrangement Example 1-2a and Arrangement Example 1-1b, for example, even when the vertical size of the transmission antenna 106 is large, the reception antenna 202 can be arranged between the elements of the transmission antenna 106, so that the effect of reducing the mounting area of the antenna can be obtained.

[0226] Further, in arrangements such as Arrangement Example 1-2a and Arrangement Example 1-1b, since the virtual antennas are arranged without overlap, the element interval of the transmission antenna 106 is arranged to be wider than the horizontal aperture length of the reception antenna 202. As a result, the horizontal aperture length of the virtual antenna expands, the peak in the target true value direction becomes sharper in the horizontal direction, and the horizontal angle measurement accuracy or resolution is improved. Also, compared with the case where the element interval of the transmission antenna 106 is expanded in Arrangement Example 1, the arrangements of Arrangement Example 1-2a and Arrangement Example 1-1b can suppress the variation in the horizontal interval of the virtual antennas more, and the effect of further reducing the rise of the side lobes near the main lobe can also be obtained.

[0227] In addition, in Arrangement Example 1-2a, the element interval of the transmission antenna 106 is wider than that in Arrangement Example 1-2b, and the horizontal aperture length in the virtual reception array arrangement is expanded. Therefore, in Arrangement Example 1-2a, due to the expansion of the element interval of the transmission antenna 106, the peak in the target true value direction becomes sharper in the horizontal direction, so that the horizontal angle measurement accuracy or estimation accuracy in the radar device 10 can be improved. Although more grating lobes may be generated due to the expansion of the element interval of the transmission antenna 106, as shown in FIG. 24, it can be confirmed that the grating lobes are suppressed by Arrangement Example 1-2a.

[0228] Also, in Arrangement Example 1-2b, the number of reception antennas 202 is smaller than that in Arrangement Example 1-2a. Therefore, in Arrangement Example 1-2b, due to the reduction in the number of reception antennas 202, the antenna configuration in the radar device 10 can be simplified, and the grating lobes can be suppressed.

[0229] In addition, in FIG. 21, the case where the antennas at the ends of each of the first diagonal antenna group and the second diagonal antenna group (for example, Rx#4) overlap has been described, but the present invention is not limited thereto. For example, the antennas included in each of the first diagonal antenna group and the second diagonal antenna group in an overlapping manner may be antennas different from the antennas at the ends of each diagonal antenna group.

[0230] [Modification Example 3 of Arrangement Example 1] The inclination of the first diagonal antenna group and the second diagonal antenna group (for example, the position change in the vertical direction with respect to the horizontal direction) is not limited to the example shown in FIG. 8, and other inclinations may be set.

[0231] For example, in Modification Example 3 of Arrangement Example 1, an example will be described in which the inclination of the first diagonal antenna group and the second diagonal antenna group is set to be gentler than that in Arrangement Example 1.

[0232] For example, in the case of Arrangement Example 1, as shown in FIG. 8, the first diagonal antenna groups Rx#1 to #4 are shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths, and are also shifted downward at intervals of 0.5 wavelengths vertically at the same time. The second diagonal antenna groups Rx#5 to #8 are shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths, and are also shifted downward at intervals of 0.5 wavelengths vertically at the same time.

[0233] In Modification Example 3 of Arrangement Example 1, for example, as shown in FIG. 26 (hereinafter referred to as "Arrangement Example 1-3"), the first diagonal antenna groups Rx#1 to #4 are shifted horizontally from left to right in the figure at intervals of 1 wavelength, and are also shifted downward at intervals of 0.5 wavelengths vertically at the same time. Further, as shown in FIG. 26, the second diagonal antenna groups Rx#5 to #8 are shifted horizontally from right to left in the figure at intervals of 1 wavelength, and are also shifted downward at intervals of 0.5 wavelengths vertically at the same time. In the Arrangement Example 1-3 shown in FIG. 26, the settings different from the inclinations of the first diagonal antenna group and the second diagonal antenna group may be the same as those in Arrangement Example 1 (for example, FIG. 8).

[0234] Thus, in FIG. 26, compared with FIG. 8, the vertical position change with respect to the horizontal direction between adjacent antennas of the first diagonal antenna group and the second diagonal antenna group is small. In other words, in FIG. 26, compared with FIG. 8, the inclinations of the first diagonal antenna group and the second diagonal antenna group are gentle.

[0235] From the arrangements of the transmission antennas Tx#1 to Tx#6 and the reception antennas Rx#1 to Rx#8 as shown in FIG. 26, the position coordinates of the virtual antennas VA#1 to #48 constituting the virtual reception array antenna are calculated based on Equation (16).

[0236] FIG. 27 is a diagram showing an arrangement example of the virtual reception array obtained by the antenna arrangement shown in FIG. 26. The aperture length of the virtual reception array shown in FIG. 27 is wider compared with Arrangement Example 1 (FIG. 9) due to the gentleness of the inclinations of the first diagonal antenna group and the second diagonal antenna group.

[0237] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangement according to the above-described arrangement examples 1-3 is applied will be described.

[0238] FIG. 28 shows the MIMO array arrangement (D H = 0.5λ, D V = 0.5λ) of Arrangement Examples 1-3, and shows the direction estimation result when the beamformer method is used as the arrival direction estimation algorithm of the direction estimation unit 213. In FIG. 28, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0239] Note that FIG. 28(a) is a diagram showing the normalized power value in the two-dimensional direction where the horizontal axis is the horizontal direction and the vertical axis is the vertical direction in a grayscale color map. Further, FIG. 28(b) is a diagram showing FIG. 28(a) with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value, and showing the normalized power value in a grayscale color map. In FIG. 28, the normalized power value may be represented by, for example, a decibel value (dB) normalized by the peak power.

[0240] As shown in FIG. 28, in Arrangement Examples 1-3, similar to Arrangement Example 1 (FIG. 10), the peak level in the grating lobe direction is suppressed as compared with the peak in the target true value direction.

[0241] Also, in Arrangement Examples 1-3, since the virtual reception array arrangement (for example, the aperture length of the virtual reception array) extends more in the horizontal direction as compared with Arrangement Example 1, as shown in FIG. 28, the peak in the target true value direction becomes sharper in the horizontal direction, so that the azimuth measurement accuracy or estimation accuracy in the horizontal direction in the radar device 10 can be improved.

[0242] In addition, in Arrangement Examples 1-3, for example, in addition to the case where the antenna size in the vertical direction of the transmission antenna 106 is large (for example, when it is 1 wavelength or more), the effect that antenna arrangement is possible when the antenna size in the horizontal direction is large (for example, when it is 1 wavelength or more) can also be obtained. For example, the larger the antenna size in the horizontal direction, the narrower the horizontal viewing angle, the directivity gain can be improved, and within a narrower (for example, limited) horizontal viewing angle, the radar performance for detecting more distant targets can be improved.

[0243] As shown in FIG. 28, in Arrangement Examples 1-3, compared with Arrangement Example 1 (for example, FIG. 10), a side lobe of about -10 dB may occur horizontally to the peak in the true target direction. The occurrence of this side lobe is caused by, for example, expanding the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group as compared with Arrangement Example 1.

[0244] For example, by expanding the interval between the first diagonal antenna group and the second diagonal antenna group, while it is possible to improve the horizontal angle measurement accuracy or estimation accuracy, the side lobe level horizontally to the peak in the true target direction increases. For example, according to requirements such as the detection target assumed by the radar device 10, the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group may be set within a suitable range.

[0245] Also, in FIG. 26, the case where the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group is wider than the aperture length of the transmission antenna 106 has been described, but it is not limited thereto, and the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group may be set to be equal to or less than the aperture length of the transmission antenna 106.

[0246] In addition, in Modification Example 3 of Arrangement Example 1, the case where the slopes of the first diagonal antenna group and the second diagonal antenna group are set to be gentler than those in Arrangement Example 1 was described. However, the present invention is not limited to this, and the slopes of the first diagonal antenna group and the second diagonal antenna group may be set to be steeper than those in Arrangement Example 1. When making the slopes of the first diagonal antenna group and the second diagonal antenna group steeper, Modification Example 4 of Arrangement Example 1 or Arrangement Example 2 described later may be applied.

[0247] [Modification Example 4 of Arrangement Example 1] For example, in Arrangement Example 1 shown in FIG. 8, the case where the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 are arranged in horizontal mirror symmetry was described. However, the present invention is not limited to this, and the first diagonal antenna group and the second diagonal antenna group do not have to be arranged in horizontal mirror symmetry. For example, the arrangement directions of the first diagonal antenna group and the second diagonal antenna group may be different directions instead of being parallel.

[0248] For example, as shown in FIG. 29 (hereinafter referred to as "Arrangement Example 1-4a"), the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 may have an asymmetric slope (for example, a position change in the vertical direction with respect to the horizontal direction), or different antenna intervals may be set in each of the horizontal direction and the vertical direction.

[0249] In addition, for example, as shown in FIG. 30 (hereinafter referred to as "Arrangement Example 1-4b"), the arrangement in which the positions of the first diagonal antenna group and the second diagonal antenna group are shifted in the vertical direction may also be used.

[0250] In addition, for example, as shown in FIG. 31 (hereinafter referred to as "Arrangement Example 1-4c"), the number of antennas included in each of the first diagonal antenna group and the second diagonal antenna group may be different.

[0251] Alternatively, for example, an arrangement combining any two or three of Arrangement Example 1-4a (asymmetric inclination), Arrangement Example 1-4b (position shifted in the vertical direction), and Arrangement Example 1-2c (number of antennas) may be used. For example, FIG. 32 (hereinafter referred to as "Arrangement Example 1-4d") shows an arrangement combining Arrangement Example 1-4a, Arrangement Example 1-4b, and Arrangement Example 1-4c.

[0252] As shown in FIG. 29, when the first diagonal antenna group and the second diagonal antenna group have an asymmetric inclination, for example, an arrangement in which the arrangement direction of the first diagonal antenna group and the arrangement direction of the second diagonal antenna group are rotationally symmetric about 90 degrees with respect to each other may be used. In this case, for example, the direction in which the grating lobe is generated due to the relationship between the transmitting antenna 106 and the first diagonal antenna group and the direction in which the grating lobe is generated due to the relationship between the transmitting antenna 106 and the second diagonal antenna group are rotationally symmetric about 90 degrees with respect to each other in the horizontal and vertical two-dimensional planes. Therefore, the interval between the grating lobes tends to be larger.

[0253] Such an arrangement in which the arrangement direction of the first diagonal antenna group and the arrangement direction of the second diagonal antenna group are rotationally symmetric about 90 degrees with respect to each other is more suitable, for example, as the number of antennas of the radar device 10 is smaller. For example, as the number of antennas of the radar device 10 is smaller, the beam width of the main beam in direction estimation tends to be wider. Therefore, when the directions of the suppressed grating lobes are close to each other, as the number of antennas of the radar device 10 is smaller, due to the spread of the beam width, the powers of the suppressed grating lobes overlap, and the power of the grating lobe may increase. Therefore, as the number of antennas of the radar device 10 is smaller, the suppression performance of the grating lobe deteriorates, and the probability of false detection in the radar device 10 tends to increase. Thus, when the number of antennas of the radar device 10 is small, for example, by an arrangement in which the arrangement direction of the first diagonal antenna group and the arrangement direction of the second diagonal antenna group are rotationally symmetric about 90 degrees with respect to each other, the overlap of the grating lobe power can be suppressed, and the suppression performance of the grating lobe can be improved.

[0254] Based on the arrangements of transmission antennas Tx#1 to Tx#6 and the arrangements of reception antennas Rx#1 to Rx#8 or Rx#1 to Rx#7 as shown in FIGS. 29 to 32, the position coordinates of virtual antennas VA#1 to VA#48 or VA#1 to VA#42 that constitute the virtual reception array antenna are calculated based on Equation (16).

[0255] FIGS. 33 to 36 are diagrams showing examples of the arrangements of virtual reception arrays obtained by the antenna arrangements shown in each of FIGS. 29 to 32.

[0256] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangements according to each of the above-described arrangement examples 1-4a to 1-4d are applied will be described.

[0257] Each of FIGS. 37 to 40 shows the MIMO array arrangements (D H = 0.5λ, D V = 0.5λ) of arrangement examples 1-4a (FIG. 29) to 1-4d (FIG. 32), and shows the direction estimation result when the beamformer method is used as the arrival direction estimation algorithm of the direction estimation unit 213. In FIGS. 37 to 40, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0258] Note that (a) in FIGS. 37 to 40 is a diagram showing the normalized power value in a two-dimensional direction where the horizontal axis is the horizontal direction and the vertical axis is the vertical direction in a grayscale color map. Also, (b) in FIGS. 37 to 40 is a diagram showing (a) in FIGS. 37 to 40, where the horizontal axis is the horizontal direction and the vertical axis is the normalized power value, and the normalized power value is shown in a grayscale color map. In FIGS. 37 to 40, the normalized power value may be represented, for example, by a decibel value (dB) normalized by the peak power.

[0259] As shown in each of FIGS. 37 to 40, according to Arrangement Example 1-4, similar to Arrangement Example 1 (FIG. 10), the peak level in the grating lobe direction is suppressed to about -5 dB as compared with the peak in the target true value direction.

[0260] [Modification Example 5 of Arrangement Example 1] In Arrangement Example 1 and Modification Examples 1 to 4, for example, the transmission antenna interval is set to an integer multiple of the basic interval D in the horizontal direction H and the inclination in the diagonal direction of the reception antenna 202 is set to an integer multiple of the basic interval D in the horizontal direction H and the inclination in the vertical direction is set to an integer multiple of the basic interval D in the vertical direction V were described.

[0261] That is, N Tx transmission antennas 106 are arranged in the horizontal direction at intervals of transmission antenna interval dT×D H .

[0262] Also, in Na reception antennas 202, the first diagonal antenna group and the second diagonal antenna group are arranged in different diagonal directions. Also, the first diagonal antenna group is shifted at intervals of dRH1×D in the horizontal direction H and is arranged in a diagonal direction that is also shifted at intervals of D in the vertical direction V . Also, the second diagonal antenna group is shifted at intervals of dRH2×D in the horizontal direction H and is arranged in a diagonal direction that is also shifted at intervals of D in the vertical direction V .

[0263] Here, dT is an integer of 2 or more, and each of dRH1 and dRH2 is an integer of 1 or more. Also, the basic interval D H and the basic interval D VIt may be a value within the range of 0.45 to 0.8 times the wavelength of the radar transmission signal. Note that dRH1 and dRH2 may be the same or different. Also, dRH1 and dRH2 may be collectively referred to as "dRH". For example, when dRH1 = dRH2, the first diagonal antenna group and the second diagonal antenna group are symmetrically arranged in the horizontal direction. When dRH1 ≠ dRH2, the first diagonal antenna group and the second diagonal antenna group are asymmetrically arranged in the horizontal direction.

[0264] For example, each of FIGS. 41 to 44 shows an antenna arrangement example when dRH1 = dRH2 and dT = 2, 4, 5, 7. Also, FIGS. 41 to 43 show the case where dRH1 = dRH2 = 1, and FIG. 44 shows the case where dRH1 = dRH2 = 2. Hereinafter, the antenna arrangement examples of FIGS. 41 to 44 are also referred to as "Arrangement Example 1-5a", "Arrangement Example 1-5b", "Arrangement Example 1-5c", and "Arrangement Example 1-5d".

[0265] Here, the larger dT is, the more likely the direction of the grating lobe generated by the relationship between the transmitting antenna 106 and the first diagonal antenna group and the direction of the grating lobe generated by the relationship between the transmitting antenna 106 and the second diagonal antenna group will coincide. Therefore, for example, as shown in FIGS. 41 to 44, the larger dT is, the closer the first diagonal antenna group and the second diagonal antenna group may be arranged. By bringing the first diagonal antenna group and the second diagonal antenna group closer, the interval between adjacent virtual antennas in the virtual receiving array can be narrowed, so that the grating lobe can be suppressed.

[0266] From the arrangements of the transmitting antennas Tx#1 to Tx#6 and the receiving antennas Rx#1 to Rx#8 as shown in FIGS. 41 to 44, the position coordinates of the virtual antennas VA#1 to VA#48 constituting the virtual receiving array antenna are calculated based on Equation (16).

[0267] Each of FIGS. 45 to 48 is a diagram showing an arrangement example of the virtual receiving array obtained by the antenna arrangements shown in FIGS. 41 to 44.

[0268] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangement according to the above-described arrangement examples 1-5a to 1-5d is applied will be described.

[0269] Each of FIGS. 49 to 52 shows the MIMO array arrangement (D H = 0.5λ, D V = 0.5λ) of the arrangement examples 1-5a to 1-5d shown in FIGS. 41 to 44, and shows the direction estimation result when the beamformer method is used as the arrival direction estimation algorithm of the direction estimation unit 213. In FIGS. 49 to 52, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90 degree range and the vertical direction ±90 degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0270] Note that (a) in FIGS. 49 to 52 is a diagram showing the normalized power value in the two-dimensional direction where the horizontal axis is the horizontal direction and the vertical axis is the vertical direction as a color map of a gray scale. Further, (b) in FIGS. 49 to 52 is a diagram showing (a) in FIGS. 49 to 52, where the horizontal axis is the horizontal direction and the vertical axis is the normalized power value, and the normalized power value is shown as a color map of a gray scale. In FIGS. 49 to 52, the normalized power value may be shown, for example, as a decibel value (dB) normalized by the peak power.

[0271] As shown in FIGS. 49 to 52, according to the arrangement examples 1-5a to 1-5d, similar to the arrangement example 1 (FIG. 10), the peak level in the grating lobe direction is suppressed as compared with the peak in the target true value direction.

[0272] Further, for example, as shown in the arrangement example 1-5a (dT = 2), the arrangement example 1-5b (dT = 4), the arrangement example 1-5c (dT = 5), and the arrangement example 1-5d (dT = 7), the larger dT is, the more the virtual reception array arrangement (for example, the aperture length of the virtual reception array) spreads in the horizontal direction. Therefore, as shown in FIGS. 49 to 52, the peak in the target true value direction becomes sharper in the horizontal direction, so that the angular measurement accuracy or estimation accuracy in the horizontal direction in the radar device 10 can be improved.

[0273] Also, for example, the larger dT is, the narrower the interval at which grating lobes occur, and the more likely it is for more grating lobes to occur. However, as shown in FIGS. 49 to 52, it can be confirmed that in each of Arrangement Examples 1-5a to 1-5d, the grating lobes are suppressed to about -3 dB to 6 dB.

[0274] Regarding the inclination of the first diagonal antenna group and the second diagonal antenna group, in the horizontal direction, it is shifted at an interval of dRH1×D H or dRH2×D H and in the vertical direction, it is also shifted simultaneously at an interval that is an integer multiple larger than the interval of D V (for example, dRV×D V . When dRV is an integer of 2 or more), the directions of the vertical grating lobes generated by the relationship between the transmitting antenna 106 and the first diagonal antenna group and the directions of the vertical grating lobes generated by the relationship between the transmitting antenna 106 and the second diagonal antenna group are more likely to coincide.

[0275] Therefore, for example, the first diagonal antenna group is arranged in a diagonal direction that is shifted at an interval of dRH1×D H in the horizontal direction and simultaneously at an interval of D V (or, in the case of dRV×D V and dRV = 1) in the vertical direction, and the second diagonal antenna group is arranged in a diagonal direction that is shifted at an interval of dRH2×D H in the horizontal direction and simultaneously at an interval of D V (or, in the case of dRV×D V and dRV = 1) in the vertical direction.

[0276] Also, regarding the inclination of the first diagonal antenna group and the second diagonal antenna group, in the horizontal direction, it is shifted at an interval of dRH1×D H or dRH2×D H and in the vertical direction, it is also shifted simultaneously at an interval of D VWhen shifting at intervals that are an integer multiple larger than the interval, for example, Arrangement Example 1-4a, or Arrangement Example 2 and the modification example described later may be applied. The virtual reception array configured using Arrangement Example 2 and the modification example described later has an expanded antenna interval in the vertical direction and can increase the aperture length in the vertical direction, so the angle measurement accuracy or resolution in the vertical direction in the radar device 10 can be improved (examples will be described later).

[0277] Note that in Arrangement Example 1 and Modification Examples 1 to 5, the transmission antenna interval is set to an integer multiple of the horizontal direction basic interval D H Regarding the inclination in the diagonal direction of the reception antenna 202, in the horizontal direction, it is set to an integer multiple of the horizontal direction basic interval D H and in the vertical direction, it is set to an integer multiple of the vertical direction basic interval D V Although an example using intervals set to integer multiples has been described, it is not limited to this, and arrangements that are not integer multiples of D V and D H may also be used.

[0278] For example, the N Tx transmission antennas 106 may be arranged in the horizontal direction with a transmission antenna interval of αD H Also, for example, the Na reception antennas 202 are arranged in different diagonal directions where the first diagonal antenna group and the second diagonal antenna group are not parallel, shifted at an interval of βD H in the horizontal direction and also simultaneously shifted at an interval of γD V in the vertical direction, and may be arranged in a diagonal direction.

[0279] Here, α, β, and γ represent positive real values, αD H is 1 wavelength or more, βD H and γD V may be real values that are 0.45 to 0.8 wavelengths or more, and the same effects as those of one embodiment of the present disclosure described above can be obtained.

[0280] As an example, in the antenna arrangement shown in FIG. 53 (hereinafter referred to as "Arrangement Example 1-5e"), when D V = 0.5 wavelength and D H = 0.5 wavelength, αD H = 2.7 wavelengths, βD V= 0.45 wavelength, γD H It is set to a wavelength of 0.6.

[0281] From the arrangements of transmission antennas Tx#1 to Tx#6 and reception antennas Rx#1 to Rx#8 as shown in FIG. 53, the position coordinates of virtual antennas VA#1 to #48 that constitute the virtual reception array antenna are calculated based on Equation (16). FIG. 54 is a diagram showing an example of the arrangement of the virtual reception array obtained by the antenna arrangement shown in FIG. 53.

[0282] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangement according to Arrangement Examples 1-5e described above is applied will be described.

[0283] FIG. 55 shows the MIMO array arrangement (D H = 0.5λ, D V = 0.5λ) of Arrangement Examples 1-5e shown in FIG. 53, and shows the direction estimation result when the beamformer method is used as the arrival direction estimation algorithm of the direction estimation unit 213. In FIG. 55, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0284] Note that FIG. 55(a) is a diagram showing the normalized power value in the two-dimensional direction where the horizontal axis is the horizontal direction and the vertical axis is the vertical direction as a grayscale color map. Also, FIG. 55(b) is a diagram showing FIG. 55(a) with the horizontal axis as the horizontal direction and the vertical axis as the normalized power value, and showing the normalized power value as a grayscale color map. In FIG. 55, the normalized power value may be shown, for example, as a decibel value (dB) normalized by the peak power.

[0285] As shown in FIG. 55, according to Arrangement Examples 1-5e, similar to Arrangement Example 1 (FIG. 10), the peak level in the grating lobe direction is suppressed as compared with the peak in the target true value direction.

[0286] [Modification Example 6 of Arrangement Example 1] In at least one of the transmission antenna 106 and the reception antenna 202 (for example, the first diagonal antenna group and the second diagonal antenna group), the interval between adjacent antennas is not limited to an equal interval, and may include one or more unequal intervals.

[0287] In the antenna arrangement example shown in FIG. 56 (hereinafter referred to as "Arrangement Example 1-6a"), the transmission antenna 106 may be arranged at unequal intervals (or non-uniform intervals). In FIG. 56, the setting different from the arrangement interval of the transmission antenna 106 may be the same as that of Arrangement Example 1 (for example, FIG. 8).

[0288] Also, in the antenna arrangement example shown in FIG. 57 (hereinafter referred to as "Arrangement Example 1-6b"), the first diagonal antenna group and the second diagonal antenna group may be arranged at unequal intervals (or non-uniform intervals). In FIG. 57, the setting different from the arrangement intervals of the first diagonal antenna group and the second diagonal antenna group may be the same as that of Arrangement Example 1 (for example, FIG. 8).

[0289] Also, in the antenna arrangement example shown in FIG. 58 (hereinafter referred to as "Arrangement Example 1-6c"), the transmission antenna 106, the first diagonal antenna group, and the second diagonal antenna group may be arranged at unequal intervals (or non-uniform intervals). In FIG. 58, the setting different from the arrangement intervals of the transmission antenna 106, the first diagonal antenna group, and the second diagonal antenna group may be the same as that of Arrangement Example 1 (for example, FIG. 8).

[0290] Also in the antenna arrangements shown in FIGS. 56 to 58, the peak level in the grating lobe direction is suppressed as compared with the peak in the target true value direction.

[0291] Note that the present invention is not limited to the above-described arrangement examples. For example, the arrangement of either the first diagonal antenna group or the second diagonal antenna group may be a non-uniform interval arrangement, and either the first diagonal antenna group or the second diagonal antenna group and the transmission antenna 106 may be arranged at non-uniform intervals.

[0292] [Modification Example 7 of Arrangement Example 1] In Modification Example 7 of Arrangement Example 1, for example, the multi-stage configuration of the antenna arrangement described in Arrangement Example 1 and Modification Examples 1 to 6 of Arrangement Example 1 may be applied.

[0293] Examples of the multi-stage configuration include, for example, a configuration in which the transmission antenna 106 is arranged in two stages in the vertical direction, a configuration in which the transmission antenna 106 is arranged in two stages in the horizontal direction, a configuration in which the first diagonal antenna group and the second diagonal antenna group of the reception antenna 202 are arranged in two stages in the vertical direction, and a configuration in which the first diagonal antenna group and the second diagonal antenna group of the reception antenna 202 are arranged in two stages in the horizontal direction. Alternatively, the multi-stage configuration may be a combination of these configurations.

[0294] Even in the case of a multi-stage configuration, the effects according to Arrangement Example 1 described above can be maintained. Further, due to the multi-stage configuration in the horizontal direction, the aperture length of the virtual reception array in the horizontal direction is expanded, and the azimuth angle measurement accuracy or resolution in the horizontal direction of the radar device 10 can be improved. Also, for example, due to the multi-stage configuration in the vertical direction, the aperture length of the virtual reception array in the vertical direction is expanded, and the azimuth angle measurement accuracy or resolution in the vertical direction of the radar device 10 can be improved. Also, for example, due to the multi-stage configuration in the vertical and horizontal directions, the aperture lengths of the virtual reception arrays in the vertical and horizontal directions are expanded, and the azimuth angle measurement accuracies or resolutions in the vertical and horizontal directions of the radar device 10 can be improved.

[0295] Note that in the case of a multi-stage configuration, the common arrangement of the transmission antenna Tx or the reception antenna Rx may be configured in multiple stages in at least one of the vertical and horizontal directions, or different arrangements of the transmission antenna Tx or the reception antenna Rx may be configured in multiple stages in at least one of the vertical and horizontal directions.

[0296] Hereinafter, examples of the antenna arrangement in Arrangement Examples 1 to 7 will be described.

[0297] For example, in FIG. 59 (hereinafter referred to as "Arrangement Example 1-7a"), Tx#1 to Tx#6 and Tx#7 to Tx#12 having the same arrangement as Tx#1 to Tx#6 are arranged in multiple stages with a vertical shift. That is, in FIG. 59, the plurality of transmission antennas 106 have a plurality of sets of six antennas arranged horizontally (for example, the set of Tx#1 to #6 and the set of Tx#7 to #12).

[0298] Also, for example, in FIG. 60 (hereinafter referred to as "Arrangement Example 1-7b"), Rx#1 to Rx#8 and Rx#9 to Rx#16 having the same arrangement as Rx#1 to Rx#8 are arranged in multiple stages with a horizontal shift. That is, in FIG. 60, the plurality of reception antennas 202 have a plurality of sets of a first diagonal antenna group and a second diagonal antenna group (for example, the set of Rx#1 to #8 and the set of Rx#9 to #16).

[0299] Also, for example, in FIG. 61 (hereinafter "Arrangement Example 1-7c"), Rx#1 to Rx#8 and Rx#9 to Rx#16 having an arrangement different from Rx#1 to Rx#8 are arranged in multiple stages vertically. That is, in FIG. 61, the plurality of reception antennas 202 have a plurality of sets of a first diagonal antenna group and a second diagonal antenna group (for example, the set of Rx#1 to #8 and the set of Rx#9 to #16).

[0300] Also, for example, in FIG. 62 (hereinafter "Arrangement Example 1-7d"), Tx#1 to Tx#6 and Tx#7 to Tx#8 having the same arrangement as Tx#1 to Tx#6 are arranged in multiple stages with a vertical shift, and Rx#1 to Rx#8 and Rx#9 to Rx#16 having an arrangement different from Rx#1 to Rx#8 are arranged in multiple stages vertically. That is, in FIG. 62, the plurality of transmission antennas 106 have a plurality of sets of six antennas arranged horizontally (for example, the set of Tx#1 to #6 and the set of Tx#7 to #12). Also, in FIG. 62, the plurality of reception antennas 202 have a plurality of sets of a first diagonal antenna group and a second diagonal antenna group (for example, the set of Rx#1 to #8 and the set of Rx#9 to #16).

[0301] Based on the arrangements of the transmission antennas and the reception antennas as shown in FIGS. 59 to 62, the position coordinates of the virtual antennas that constitute the virtual reception array antenna are calculated based on Equation (16).

[0302] Each of FIGS. 63 to 66 is a diagram showing an example of the arrangement of the virtual reception array obtained by the antenna arrangements shown in FIGS. 59 to 62.

[0303] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangements according to each of the above-described Arrangement Examples 1-7a to 1-7d are applied will be described.

[0304] Each of FIGS. 67 to 70 shows the MIMO array arrangement (D H = 0.5λ, D V = 0.5λ) shown in FIGS. 59 to 62, and shows the direction estimation result when the beamformer method is used as the arrival direction estimation algorithm of the direction estimation unit 213. In FIGS. 67 to 70, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction range of ±90 degrees and the vertical direction range of ±90 degrees when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0305] Note that (a) of FIGS. 67 to 70 is a diagram showing the normalized power value in the two-dimensional direction where the horizontal axis is the horizontal direction and the vertical axis is the vertical direction in a grayscale color map. Also, (b) of FIGS. 67 to 70 is a diagram showing (a) of FIGS. 67 to 70, where the horizontal axis is the horizontal direction and the vertical axis is the normalized power value, and the normalized power value is shown in a grayscale color map. Note that in FIGS. 67 to 70, the normalized power value may be represented, for example, by a decibel value (dB) normalized by the peak power.

[0306] As shown in FIGS. 67 to 70, in Arrangement Examples 1-7a to 1-7d, similar to Arrangement Example 1 (FIG. 10), the peak level in the grating lobe direction is suppressed as compared with the peak in the target true value direction.

[0307] Also, in Arrangement Example 1-7a (Fig. 59), compared with Arrangement Example 1 (Fig. 8), the number of transmission antennas Tx increases, and the elements of the transmission antenna 106 are shifted in the vertical direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7a, since the aperture length of the virtual reception array in the vertical direction expands, as shown in Fig. 67, the peak in the target true value direction becomes sharper in the vertical direction, and it becomes possible to improve the angular measurement accuracy or estimation accuracy in the vertical direction in the radar device 10.

[0308] Also, in Arrangement Example 1-7b (Fig. 60), compared with Arrangement Example 1 (Fig. 8), the number of reception antennas Rx increases, and the elements of the reception antenna 202 are shifted in the horizontal direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7b, since the aperture length of the virtual reception array in the horizontal direction expands, as shown in Fig. 68, the peak in the target true value direction becomes sharper in the horizontal direction, and it becomes possible to improve the angular measurement accuracy or estimation accuracy in the horizontal direction in the radar device 10.

[0309] Also, in Arrangement Example 1-7c (Fig. 61), compared with Arrangement Example 1 (Fig. 8), the number of reception antennas Rx increases, and the elements of the reception antenna 202 are shifted in the vertical direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7c, since the aperture length of the virtual reception array in the vertical direction expands, as shown in Fig. 69, the peak in the target true value direction becomes sharper in the vertical direction, and it becomes possible to improve the angular measurement accuracy or estimation accuracy in the vertical direction in the radar device 10.

[0310] Also, in Arrangement Example 1-7d (Fig. 62), compared with Arrangement Example 1 (Fig. 8), the number of both the transmission antenna Tx and the reception antenna Rx increases, and the elements of both the transmission antenna 106 and the reception antenna 202 are shifted in the vertical direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7d, since the aperture length of the virtual reception array in the vertical direction expands, as shown in Fig. 70, compared with Arrangement Example 1-7a (for example, Fig. 59), the peak in the target true value direction becomes sharper in the vertical direction, and it becomes possible to improve the angular measurement accuracy or estimation accuracy in the vertical direction in the radar device 10.

[0311] In addition, in the multi-stage configuration in Arrangement Examples 1-7, different antenna elements (for example, antenna elements with different sizes) may be used in combination. For example, the plurality of transmission antennas 106 may include a long-range (LR) antenna element and a short-range (SR) antenna element. Here, the LR antenna element has a higher directivity gain of the antenna element by narrowing the directivity in the vertical direction, the horizontal direction, or both compared to the SR antenna element. By using the LR antenna element, the radar device 10 can increase the reception signal level of the reflected wave from a target at a farther distance compared to the case of using the SR antenna element, enabling detection of a target at a farther distance. Since the LR antenna element increases the directivity gain in the vertical direction, the horizontal direction, or both, its physical size is larger in the vertical direction, the horizontal direction, or both compared to the SR antenna element size.

[0312] For example, in the multi-stage configuration, a long-range (LR) antenna element may be applied in the first stage, and a short-range (SR) antenna element may be used in combination in the second stage. For example, as shown in FIG. 59, when the transmission antenna 106 is arranged in a two-stage multi-stage configuration in the vertical direction, a long-range (LR) antenna element may be applied in the first stage (for example, Tx#1 to Tx#6), and a short-range (SR) antenna element may be applied in the second stage (for example, Tx#7 to Tx#12).

[0313] Note that when the vertical and horizontal sizes of the long-range (LR) antenna element are large, one stage of elements may be shifted horizontally so that the first-stage transmission antenna 106 and the second-stage transmission antenna 106 do not overlap.

[0314] Thus, when using the LR antenna and the SR antenna for the transmission antenna 106, for example, an SR antenna (for example, an antenna having a characteristic of a wide viewing angle) may be applied to the reception antenna 202. Thereby, while maintaining the effect of Arrangement Example 1, it is possible to cope with the detection ranges of both the LR and SR modes.

[0315] [Modification Example 8 of Arrangement Example 1] Regarding Arrangement Condition 1, for the case where the arrangement directions of N Tx transmission antennas 106 are in the horizontal direction, an explanation has been given. However, for N Tx the arrangement directions of the transmission antennas 106 do not necessarily have to exactly match the horizontal direction.

[0316] For example, as shown in FIG. 71 (hereinafter referred to as "Arrangement Example 1-8"), the transmission antenna groups Tx#1 to #6 are shifted in the horizontal direction by an interval of one wavelength (e.g., 2D H ) from left to right in the figure, and at the same time, they may be shifted upward by an interval of 0.25 wavelengths (e.g., 0.5D V ) in the vertical direction. For example, if the inclination of the transmission antenna 106 with respect to the horizontal direction is as gentle as that shown in FIG. 71, the antenna arrangement shown in FIG. 71 may be included in the arrangement that satisfies Arrangement Condition 1. Note that the arrangements of the reception antennas Rx#1 to Rx#8 are not limited to the example shown in FIG. 71, and other arrangements may also be used.

[0317] From the arrangements of the transmission antennas Tx#1 to Tx#6 and the reception antennas Rx#1 to Rx#8 as shown in FIG. 71, the position coordinates of the virtual antennas VA#1 to #48 that constitute the virtual reception array antenna are calculated based on Equation (16). FIG. 72 is a diagram showing an example of the arrangement of the virtual reception array obtained by the antenna arrangement shown in FIG. 71.

[0318] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangement according to Arrangement Example 1-8 described above is applied will be described.

[0319] FIG. 73 shows the MIMO array arrangement of Arrangement Example 1-8 (D H = 0.5λ, D VThe direction estimation result when using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213 is shown using ( = 0.5λ). In FIG. 73, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction range of ±90 degrees and the vertical direction range of ±90 degrees when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0320] Note that FIG. 73(a) is a diagram showing the normalized power value in a two-dimensional direction with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction using a grayscale color map. Further, FIG. 73(b) is a diagram showing FIG. 73(a) with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value, and showing the normalized power value using a grayscale color map. In FIG. 73, the normalized power value may be represented, for example, by a decibel value (dB) normalized by the peak power.

[0321] As shown in FIG. 73, in Arrangement Examples 1-8, similar to Arrangement Example 1 (for example, FIG. 10), the peak level in the grating lobe direction is suppressed compared to the peak in the target true value direction.

[0322] Also, in Arrangement Examples 1-8, compared to Arrangement Example 1 (for example, FIG. 8), the transmission antenna 106 is arranged gently obliquely with respect to the horizontal direction. In other words, in Arrangement Examples 1-8, the arrangement of the transmission antenna 106 also has an expansion in the vertical direction. For this reason, in the virtual reception array arrangement, the aperture length in the vertical direction expands more, so as shown in FIG. 73, the peak in the target true value direction becomes sharper in the vertical direction, and the angular measurement accuracy or estimation accuracy in the vertical direction in the radar device 10 can be improved. Note that in Arrangement Examples 1-8, since the transmission beam direction gently tilts obliquely, the occurrence range of the grating lobe tends to expand in the horizontal direction.

[0323] The above describes the modification example of Arrangement Example 1.

[0324] [Arrangement Example when the minimum antenna configuration and the number of antennas in Arrangement Condition 1 are small] Hereinafter, the minimum antenna configuration that satisfies the arrangement condition 1 and an arrangement example in the case where the number of antennas that satisfies the arrangement condition 1 is small will be described. Note that the same effect can be obtained by applying a modification similar to the modification example of the above-described arrangement example 1 to the antenna arrangement described below.

[0325] The minimum number of antennas for the arrangement condition 1 is, for example, the number of transmission antennas N Tx = 2, and the number of reception antennas Na = 3. In other words, the number of transmission antennas 106 is 2, and the total number of antennas in the first diagonal antenna group and the second diagonal antenna group is 3.

[0326] FIG. 74 shows an antenna arrangement example of the minimum number of antennas (the number of transmission antennas N Tx = 2, and the number of reception antennas Na = 3) for the arrangement condition 1. FIG. 74(a) shows an example of a MIMO antenna arrangement, and FIG. 74(b) shows an example of a virtual reception array arrangement configured by the MIMO antenna arrangement shown in FIG. 74(a). Also, in FIG. 74, the scales of the horizontal axis and the vertical axis are, for example, D H and D V respectively.

[0327] In FIG. 74, the first diagonal antenna group includes Rx#1 and Rx#2, and the second diagonal antenna group includes Rx#2 and Rx#3.

[0328] Also, FIGS. 75 to 79 show antenna arrangement examples in the case where the number of antennas that satisfies the arrangement condition 1 is small. FIGS. 75 to 79(a) show examples of MIMO antenna arrangements, and FIGS. 75 to 79(b) show examples of virtual reception array arrangements configured by the MIMO antenna arrangements shown in FIGS. 75 to 79(a). Also, in FIGS. 75 to 79, the scales of the horizontal axis and the vertical axis are, for example, D H and D V respectively.

[0329] For example, FIGS. 75 and 76 show the number of transmission antennas N Tx= 2, and shows an antenna arrangement example when the number of receiving antennas Na = 4. In FIGS. 75 and 76, the first diagonal antenna group includes Rx#1 and Rx#2, and the second diagonal antenna group includes Rx#3 and Rx#4.

[0330] Also, for example, FIG. 77 shows an antenna arrangement example when the number of transmitting antennas N Tx = 3, and the number of receiving antennas Na = 3. In FIG. 77, the first diagonal antenna group includes Rx#1 and Rx#2, and the second diagonal antenna group includes Rx#2 and Rx#3.

[0331] Also, for example, FIGS. 78 and 79 show an antenna arrangement example when the number of transmitting antennas N Tx = 3, and the number of receiving antennas Na = 4. In FIGS. 78 and 79, the first diagonal antenna group includes Rx#1 and Rx#2, and the second diagonal antenna group includes Rx#3 and Rx#4.

[0332] The example of arrangement condition 1 has been described above.

[0333] [Arrangement condition 2] N Tx The N transmitting antennas 106 include a "first diagonal antenna group" arranged in the "first diagonal direction" and a "second diagonal antenna group" arranged in the "second diagonal direction", and the first diagonal direction and the second diagonal direction are not parallel. In other words, the first diagonal direction and the second diagonal direction are different from each other. The Na receiving antennas 202 include a "third diagonal antenna group" arranged in the "third diagonal direction" and a "fourth diagonal antenna group" arranged in the "fourth diagonal direction", and the third diagonal direction and the fourth diagonal direction are not parallel. In other words, the third diagonal direction and the fourth diagonal direction are different from each other.

[0334] Note that each of the first diagonal antenna group (for example, corresponding to the third antenna group) and the second diagonal antenna group (for example, corresponding to the fourth antenna group) may include at least two transmission antennas 106. Also, each of the third diagonal antenna group (for example, corresponding to the first antenna group) and the fourth diagonal antenna group (for example, corresponding to the second antenna group) may include at least two reception antennas 202.

[0335] By arranging the first diagonal antenna group and the second diagonal antenna group that satisfy the arrangement condition 2 at arbitrary positions, it is possible to suppress grating lobes. For example, as shown in the following arrangement example or modified example, by arranging the first diagonal antenna group and the second diagonal antenna group such that their horizontal positions do not overlap, it is possible to arrange a transmission antenna element having a large vertical size.

[0336] Similarly, by arranging the third diagonal antenna group and the fourth diagonal antenna group that satisfy the arrangement condition 2 at arbitrary positions, it is possible to suppress grating lobes. For example, as shown in the following arrangement example or modified example, by arranging the third diagonal antenna group and the fourth diagonal antenna group such that their horizontal positions do not overlap, it is possible to arrange a reception antenna element having a large vertical size.

[0337] In the arrangement condition 2, for example, since the transmission antenna 106 includes the first diagonal antenna group arranged in the first diagonal direction and the second diagonal antenna group arranged in the second diagonal direction, compared with the arrangement condition 1, the vertical aperture length of the virtual reception array can be further expanded, so that the vertical angle measurement accuracy or resolution in the radar device 10 can be improved.

[0338] Also, in the arrangement condition 2, for example, it is possible to suppress the vertical grating lobes generated when making the inclination of the first to fourth diagonal directions steeper, for example, with respect to the horizontal direction. Due to this grating lobe suppression effect, the vertical aperture length can be further expanded, and the vertical angle measurement accuracy or resolution in the radar device 10 can be further improved.

[0339] Next, an example of Arrangement Condition 2 will be described. Hereinafter, an arrangement example that satisfies Arrangement Condition 2 and an example of a direction estimation result by computer simulation in the arrangement example will be described.

[0340] <Arrangement Example 2> FIG. 80 is a diagram showing an arrangement example (for example, a MIMO antenna arrangement example) of a transmission antenna 106 (for example, represented as Tx) and a reception antenna 202 (for example, represented as Rx) according to Arrangement Example 2. In FIG. 80, the scales on the horizontal axis and the vertical axis are, for example, the basic interval D in the horizontal direction H , and the basic interval D in the vertical direction V . Note that the scales on the horizontal axis and the vertical axis are the same for the MIMO antenna arrangements in the following other examples. As an example, D H and D V may be at an interval of 0.5 wavelength.

[0341] In the example shown in FIG. 80, the number of transmission antennas N Tx is six (for example, Tx#1, Tx#2, Tx#3, Tx#4, Tx#5, and Tx#6), and the number of reception antennas Na is eight (for example, Rx#1, Rx#2, Rx#3, Rx#5, Rx#6, Rx#7, and Rx#8).

[0342] In FIG. 80, the six transmission antennas Tx#1 to #6 of N Tx = 6 include a first diagonal antenna group Tx#1 to #3 arranged in a first diagonal direction and a second diagonal antenna group Tx#4 to #6 arranged in a second diagonal direction. In FIG. 80, the first diagonal direction and the second diagonal direction are not parallel and are different from each other.

[0343] Also, in FIG. 80, the eight reception antennas Rx#1 to #8 of Na = 8 include a third diagonal antenna group Rx#1 to #4 arranged in a third diagonal direction and a fourth diagonal antenna group Rx#5 to #8 arranged in a fourth diagonal direction. In FIG. 80, the third diagonal direction and the fourth diagonal direction are not parallel and are different from each other.

[0344] From these, the antenna arrangement of Arrangement Example 2 shown in FIG. 80 satisfies Arrangement Condition 2.

[0345] Also, in Arrangement Example 2, as shown in FIG. 80, the first to fourth diagonal directions are not parallel to each other but are different from each other.

[0346] For example, the first diagonal antenna groups Tx#1 to #3 shown in FIG. 80 are shifted horizontally at intervals of 1.5 wavelengths from left to right in the figure and simultaneously shifted upward at intervals of 0.5 wavelengths vertically. Also, the second diagonal antenna groups Tx#4 to #6 shown in FIG. 80 are shifted horizontally at intervals of 1.5 wavelengths from left to right in the figure and simultaneously shifted downward at intervals of 0.5 wavelengths vertically.

[0347] Thus, in FIG. 80, the antenna arrangement of the first diagonal antenna group arranged in the first diagonal direction and the antenna arrangement of the second diagonal antenna group arranged in the second diagonal direction are in a line-symmetric relationship with respect to a line parallel in the vertical direction (a line perpendicular to the horizontal direction). In other words, the first diagonal antenna groups Tx#1 to #3 and the second diagonal antenna groups Tx#4 to #6 are arranged in a horizontally inversion-symmetric (or left-right inversion-symmetric or mirror-symmetric) manner.

[0348] Here, the transmission antenna 106 of Arrangement Example 1 (for example, FIG. 8) is arranged horizontally. On the other hand, the transmission antenna 106 of Arrangement Example 2 is arranged in a diagonal direction as shown in FIG. 80. In other words, since the transmission antenna 106 of Arrangement Example 2 is arranged two-dimensionally in the horizontal and vertical directions, Arrangement Example 2 can expand the vertical aperture more than Arrangement Example 1.

[0349] Also, for example, the third diagonal antenna groups Rx#1 to #4 shown in FIG. 80 are shifted horizontally at intervals of 0.5 wavelengths from right to left in the figure and simultaneously shifted downward at intervals of 1 wavelength vertically. Also, the fourth diagonal antenna groups Rx#5 to #8 shown in FIG. 80 are shifted horizontally at intervals of 0.5 wavelengths from left to right in the figure and simultaneously shifted downward at intervals of 1 wavelength vertically.

[0350] Thus, the antenna arrangement of the third diagonal antenna group arranged in the third diagonal direction and the antenna arrangement of the fourth diagonal antenna group arranged in the fourth diagonal direction are in a line-symmetric relationship with respect to a line parallel to the vertical direction (a line perpendicular to the horizontal direction). In other words, the third diagonal antenna group Rx#1~#4 and the fourth diagonal antenna group Rx#5~#8 are arranged in a horizontally inversion-symmetric manner.

[0351] For example, the third diagonal antenna group Rx#1~#4 and the fourth diagonal antenna group Rx#5~#8 in Arrangement Example 2 shown in FIG. 80 have a steeper slope with respect to the horizontal direction compared to the first diagonal antenna group Rx#1~#4 and the second diagonal antenna group Rx#5~#8 in Arrangement Example 1 (e.g., FIG. 8), so the vertical aperture can be further expanded.

[0352] Also, for example, each of the third diagonal antenna group Rx#1~#4 and the fourth diagonal antenna group Rx#5~#8 in Arrangement Example 2 shown in FIG. 80 is arranged at intervals of one wavelength or more in the vertical direction. Therefore, the element intervals of the third diagonal antenna group and the fourth diagonal antenna group are intervals at which grating lobes can occur in the vertical direction. In Arrangement Example 2, for example, since the first to fourth diagonal directions are not parallel but different directions, by making the two-dimensional directions in the vertical and horizontal directions where grating lobes occur different, the grating lobes in the vertical direction can be suppressed.

[0353] FIG. 81 is a diagram showing an arrangement example of a virtual reception array obtained by the antenna arrangement shown in FIG. 80.

[0354] Here, the arrangement of the virtual reception array may be expressed as in Equation (16) based on the positions (e.g., the positions of the feeding points) of the transmission antennas 106 constituting the transmission array antenna and the positions (e.g., the positions of the feeding points) of the reception antennas 202 constituting the reception array antenna.

[0355] The position coordinates of the transmission antenna 106 (e.g., Tx#n) constituting the transmission array antenna are (X T_#n , Y T_#n )(e.g., n = 1,.., NTx ) is represented as, and the position coordinates of the receiving antenna 202 (for example, Rx#m) constituting the receiving array antenna are (X R_#m , Y R_#m )(for example, m = 1,.., Na), and the position coordinates of the virtual antenna VA#k constituting the virtual receiving array are (X V_#k , Y V_#k )(for example, k = 1,.., N Tx ×Na). In Equation (16), for example, VA#1 is represented as the position reference (0,0) of the virtual receiving array.

[0356] For example, from the arrangements of the transmitting antennas Tx#1~Tx#6 and the receiving antennas Rx#1~Rx#8 as shown in FIG. 80, the position coordinates of the virtual antennas VA#1~#48 constituting the virtual receiving array antenna are calculated from Equation (16). For example, the position coordinates of the virtual antennas VA#1~#16 are (X V_#1 , Y V_#1 ) = (0,0), (X V_#2 , Y V_#2 ) = (-D H , -2D V ), (X V_#3 , Y V_#3 ) = (-2D H , -4D V ), (X V_#4 , Y V_#4 ) = (-3D H , -6D V ), (X V_#5 , Y V_#5 ) = (17D H , 0), (X V_#6 , Y V_#6 ) = (18D H , -2D V ), (X V_#7 , Y V_#7 ) = (19D H , -4D V ), (X V_#8 , Y V_#8 ) = (20 D H , -6D V ), (X V_#9 , Y V_#9 ) = (3D H , D V ), (X V_#10 , YV_#10 ) = (2D H , -D V )、(X V_#11 , Y V_#11 ) = (D H , -3D V )、(X V_#12 , Y V_#12 ) = (0, -5D V )、(X V_#13 , Y V_#13 ) = (20D H , D V )、(X V_#14 , Y V_#14 ) = (21D H , -D V )、(X V_#15 , Y V_#15 ) = (22D H , -3D V )、(X V_#16 , Y V_#16 ) = (23D H , -5D V ) is obtained.

[0357] Here, in the cases of FIGS. 80 and 81, for D H and D V , the case where 0.5λ is set for each will be described. For example, values in the range of about 0.45λ to 0.8λ may be set for each. Note that λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, when a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency in the frequency sweep band of the chirp signal.

[0358] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described antenna arrangement is applied will be described.

[0359] For example, the direction estimation unit 213 uses the received signal (or the code separation result) DeMul z ncm (f b_cfar , f s_cfar ) obtained by code separation processing of the code multiplexed signal transmitted from the transmission antenna 106 to calculate the virtual reception array correlation vector h(f b_cfar , f s_cfar) is generated and direction estimation processing is performed.

[0360] The virtual reception array correlation vector h(f b_cfar , f s_cfar ) is the product of the number of transmission antennas N Tx and the number of reception antennas Na, which is N Tx ×Na and contains Na elements. The virtual reception array correlation vector h(f b_cfar , f s_cfar ) is used for the process of performing direction estimation based on the phase difference between each reception antenna 202 with respect to the reflected wave signal from the target.

[0361] For example, in the MIMO antenna arrangement example of Arrangement Example 2, in the example of FIG. 80, N Tx = 6, Na = 8, so the virtual reception array correlation vector h(f b_cfar , f s_cfar ) contains 48 elements, each corresponding to the received signal at VA#1 to VA48 in the virtual reception array arrangement shown in FIG. 81.

[0362] The direction estimation unit 213 performs horizontal and vertical direction estimation processing using, for example, the virtual reception array correlation vector h(f b_cfar , f s_cfar ) which is the received signal of the virtual reception array composed of the above-described transmission and reception antenna arrangements. Note that the operation of the direction estimation unit 213 hereafter is the same as the operation when Arrangement Example 1 is used, and the description thereof is omitted.

[0363] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangement according to Arrangement Example 2 described above is applied will be described.

[0364] FIG. 82 shows the MIMO array arrangement of Arrangement Example 2 (D H = 0.5λ, D VThe direction estimation result when using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213 is shown using (where \(d = 0.5\lambda\)). In FIG. 82, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction range of ±90 degrees and the vertical direction range of ±90 degrees when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0365] Note that FIG. 82(a) is a diagram showing the normalized power value in a two-dimensional direction with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction using a grayscale color map. Also, FIG. 82(b) is a diagram showing FIG. 82(a) with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value, and the normalized power value is also shown using a grayscale color map. Further, FIG. 82(c) is a diagram showing FIG. 82(a) with the horizontal axis being the vertical direction and the vertical axis being the normalized power value, and the normalized power value is also shown using a grayscale color map. In FIG. 82, the normalized power value may be represented, for example, by a decibel value (dB) normalized by the peak power, and the same applies to the plots of the direction estimation results in the following other examples.

[0366] Here, as shown in FIG. 80, in the transmitting antenna 106 of arrangement example 2, the antenna intervals of the first diagonal antenna group Tx#1~#3 and the second diagonal antenna group Tx#4~#6 are intervals of 1 wavelength or more, so they are antenna intervals at which grating lobes can occur. Also, as shown in FIG. 80, in the receiving antenna 202 of arrangement example 2, the antenna intervals of the third diagonal antenna group Rx#1~#4 and the fourth diagonal antenna group Rx#5~#8 are intervals of 1 wavelength or more, so they are antenna intervals at which grating lobes can occur.

[0367] Also, as shown in FIG. 81, in the virtual receiving array arrangement, each virtual antenna is arranged at an interval of 1 wavelength or more in both the horizontal direction and the vertical direction, which is an interval at which grating lobes can occur.

[0368] In Configuration Example 2, by devising the arrangements of the transmission antenna 106 and the reception antenna 202, such grating lobes are suppressed. For example, as shown in FIG. 82, it can be seen that the grating lobes are suppressed to about -7.5 dB or less in a direction different from the peak direction in the target true value direction.

[0369] Hereinafter, the principle of suppressing grating lobes by the MIMO antenna arrangement in Configuration Example 2 will be described.

[0370] For example, FIG. 83(a) shows the antenna arrangement (hereinafter referred to as "comparative arrangement 2a") when using the first diagonal antenna group Tx#1 to #3 and the third diagonal antenna group Rx#1 to #4 of the arrangement example 2 shown in FIG. 80 for comparison with the arrangement example 2. FIGS. 83(b), (c), and (d) show the direction estimation results using the beamformer method in the antenna arrangement shown in FIG. 83(a). In FIGS. 83(b), (c), and (d), similar to FIG. 82, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0371] Note that the virtual reception array arrangement when using the comparative arrangement 2a corresponds to VA#1 to #4, #9 to #12, and #17 to #20 in FIG. 81.

[0372] Similarly, FIG. 84(a) shows the antenna arrangement (hereinafter referred to as "comparative arrangement 2b") when using the second diagonal antenna group Tx#4 to #6 and the fourth diagonal antenna group Rx#5 to #8 of the arrangement example 2 shown in FIG. 80 for comparison with the arrangement example 2. FIGS. 84(b), (c), and (d) show the direction estimation results using the beamformer method in the antenna arrangement shown in FIG. 84(a). In FIGS. 84(b), (c), and (d), similar to FIG. 82, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0373] Note that the virtual reception array arrangement when using the comparative arrangement 2b corresponds to #29 to #32, #37 to #40, and #45 to #48 in FIG. 81.

[0374] Also, FIG. 85(a) shows the antenna arrangement when using the first diagonal antenna group Tx#1 to #3 and the fourth diagonal antenna group Rx#5 to #8 of the arrangement example 2 shown in FIG. 80 for comparison with the arrangement example 2 (hereinafter referred to as "comparative arrangement 2c"). FIGS. 85(b), (c), and (d) show the direction estimation results using the beamformer method in the antenna arrangement shown in FIG. 85(a). Note that in FIGS. 85(b), (c), and (d), similar to FIG. 82, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0375] Note that the virtual reception array arrangement when using the comparative arrangement 2c corresponds to #5 to #8, #13 to #16, and #21 to #24 in FIG. 81.

[0376] Also, FIG. 86(a) shows the antenna arrangement when using the first diagonal antenna group Tx#4 to #6 and the third diagonal antenna group Rx#1 to #4 of the arrangement example 2 shown in FIG. 80 for comparison with the arrangement example 2 (hereinafter referred to as "comparative arrangement 2d"). FIGS. 86(b), (c), and (d) show the direction estimation results using the beamformer method in the antenna arrangement shown in FIG. 86(a). Note that in FIGS. 86(b), (c), and (d), similar to FIG. 82, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0377] Note that the virtual reception array arrangement when using the comparative arrangement 2d corresponds to #25 to #28, #33 to #36, and #41 to #44 in FIG. 81.

[0378] For example, when using the first diagonal antenna group Tx#1 to #3 and the third diagonal antenna group Rx#1 to #4 as in the comparative arrangement 2a shown in Fig. 83(a), and when using the second diagonal antenna group Tx#4 to #6 and the fourth diagonal antenna group Rx#5 to #8 as in the comparative arrangement 2b shown in Fig. 84(a), they will be described.

[0379] The arrangement directions of the transmitting antennas Tx#1 to #3 (for example, corresponding to the first diagonal antenna group) in the comparative arrangement 2a shown in Fig. 83(a) and the arrangement directions of the transmitting antennas Tx#4 to #6 (for example, corresponding to the second diagonal antenna group) in the comparative arrangement 2b shown in Fig. 84(a) are not parallel but different. Also, the arrangement directions of the receiving antennas Rx#1 to #4 (for example, corresponding to the third diagonal antenna group) in the comparative arrangement 2a and the arrangement directions of the receiving antennas Rx#5 to #8 (for example, corresponding to the fourth diagonal antenna group) in the comparative arrangement 2b are not parallel but different. Therefore, as shown in Fig. 83(b) and Fig. 84(b), the comparative arrangement 2a and the comparative arrangement 2b have the property that the horizontal and vertical two-dimensional angular directions in which grating lobes occur do not coincide and are shifted.

[0380] On the other hand, as shown in Fig. 83(b) and Fig. 84(b), the angular directions (for example, horizontal 0 degrees, vertical 0 degrees) of the main lobes corresponding to the target true values in the comparative arrangement 2a and the comparative arrangement 2b are the same.

[0381] Therefore, as shown in Fig. 80, in the arrangement example 2 including the first to fourth diagonal antenna groups, the grating lobes generated in the comparative arrangement 2a including the first diagonal antenna group and the third diagonal antenna group, and the grating lobes generated in the comparative arrangement 2b including the second diagonal antenna group and the fourth diagonal antenna group do not have the same generation direction (two-dimensional angular direction) and are likely to be dispersed. For this reason, in the arrangement example 2, as shown in Fig. 82(a), the peak level in the grating lobe direction is likely to be suppressed compared to the peak in the target true value direction.

[0382] Next, for example, when using the first diagonal antenna groups Tx#1 to #3 and the fourth diagonal antenna groups Rx#5 to #8 as in the comparative arrangement 2c shown in Fig. 85(a), and when using the second diagonal antenna groups Tx#4 to #6 and the third diagonal antenna groups Rx#1 to #4 as in the comparative arrangement 2d shown in Fig. 86(a), an explanation will be given.

[0383] The arrangement directions of the transmitting antennas Tx#1 to #3 (for example, corresponding to the first diagonal antenna group) in the comparative arrangement 2c shown in Fig. 85(a) and the arrangement directions of the transmitting antennas Tx#4 to #6 (for example, corresponding to the second diagonal antenna group) in the comparative arrangement 2d shown in Fig. 86 are not parallel but different. Also, the arrangement directions of the receiving antennas Rx#5 to #8 (for example, corresponding to the fourth diagonal antenna group) in the comparative arrangement 2c and the arrangement directions of the receiving antennas Rx#1 to #4 (for example, corresponding to the third diagonal antenna group) in the comparative arrangement 2d are not parallel but different. For this reason, as shown in Fig. 85(b) and Fig. 86(b), the comparative arrangement 2c and the comparative arrangement 2d have the property that the horizontal and vertical two-dimensional angular directions in which grating lobes are generated do not coincide but are shifted.

[0384] On the other hand, as shown in Fig. 85(b) and Fig. 86(b), in the comparative arrangement 2c and the comparative arrangement 2d, the angular directions (for example, horizontal 0 degrees, vertical 0 degrees) of the main lobes corresponding to the target true values coincide.

[0385] Therefore, as shown in Fig. 80, in the arrangement example 2 including the first to fourth diagonal antenna groups, the grating lobes generated in the comparative arrangement 2c including the first diagonal antenna group and the fourth diagonal antenna group, and the grating lobes generated in the comparative arrangement 2d including the second diagonal antenna group and the third diagonal antenna group do not have the same generation direction (two-dimensional angular direction), and are likely to be dispersed. For this reason, in the arrangement example 2, as shown in Fig. 82(a), the peak level in the grating lobe direction is likely to be suppressed compared to the peak in the target true value direction.

[0386] Here, the virtual receiving array arrangement shown in FIG. 81 is the same as the virtual receiving array partially constituted by virtual receiving arrays corresponding to the comparison arrangements 2a, 2b, 2c, and 2d. Therefore, as shown in FIG. 82(a), the direction estimation result by the virtual receiving array arrangement shown in FIG. 81 suppresses the grating lobes in directions different from the peak direction of the target true value direction. In other words, in Arrangement Example 2, the angular directions in which grating lobes are generated by the plurality of diagonal antenna groups included in each of the transmitting antenna 106 and the receiving antenna 202 are dispersed in different directions. For this reason, for example, as shown in FIG. 82(b), in Arrangement Example 2, the normalized power value of the grating lobe is more likely to be suppressed to be low with respect to the normalized power value of the main lobe with respect to the target true value. For example, in FIG. 82(b), it can be seen that the peaks in directions different from the peak direction of the target true value direction are suppressed to about -7.5 dB or less.

[0387] Note that, for example, in the antenna arrangement of Arrangement Example 2 shown in FIG. 80, the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion symmetric, and the arrangement directions of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inversion symmetric. In this case, the virtual receiving array arrangements corresponding to the comparison arrangements 2a and 2b are horizontally inversion symmetric. As a result, for example, as shown in FIGS. 83(b) and 84(b), in each of the comparison arrangements 2a and 2b, the horizontal and vertical two-dimensional directions in which grating lobes are generated are horizontally inversion symmetric, and it can be seen that the deviation of the horizontal and vertical two-dimensional angular directions in which grating lobes are generated becomes larger.

[0388] Similarly, for example, in the antenna arrangement of Arrangement Example 2 shown in FIG. 80, the arrangement directions of each of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion symmetric, and the arrangement directions of each of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inversion symmetric. In this case, the virtual receiving array arrangements corresponding to Comparative Arrangement 2c and Comparative Arrangement 2d are horizontally inversion symmetric. As a result, for example, as shown in FIGS. 85(b) and 86(b), in each of Comparative Arrangement c and Comparative Arrangement d, the horizontal and vertical two-dimensional directions in which grating lobes occur are horizontally inversion symmetric, and it can be seen that the deviation in the horizontal and vertical two-dimensional angular directions in which grating lobes occur becomes larger.

[0389] Therefore, in Arrangement Example 2, when the arrangement directions of each of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion symmetric, and the arrangement directions of each of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inversion symmetric, for example, the closer the inclination of the diagonal direction of each of the first to fourth diagonal antenna groups is to 45 degrees with respect to the horizontal direction, the more likely the interval (or deviation) in the horizontal and vertical two-dimensional angular directions in which grating lobes occur becomes larger.

[0390] Also, for example, when the arrangement directions of each of the first diagonal antenna group and the second diagonal antenna group are not horizontally inversion symmetric, or when the arrangement directions of each of the third diagonal antenna group and the fourth diagonal antenna group are not horizontally inversion symmetric, the closer the inclination of the diagonal direction of each of the first to fourth diagonal antenna groups is to 45 degrees with respect to the horizontal direction, the more likely the interval in the horizontal and vertical two-dimensional angular directions in which grating lobes occur becomes larger.

[0391] An antenna arrangement in which the intervals in the horizontal and vertical two-dimensional angular directions where such grating lobes occur are larger is more suitable, for example, as the number of antennas of the radar device 10 is smaller. For example, as the number of antennas of the radar device 10 is smaller, the beam width of the main beam in direction estimation tends to be wider. Therefore, when the directions of the grating lobes to be suppressed are close, as the number of antennas of the radar device 10 is smaller, due to the spread of the beam width, the grating lobe powers overlap, and the power of the grating lobes can increase. For this reason, as the number of antennas of the radar device 10 is smaller, the suppression performance of the grating lobes deteriorates, and the probability of false detection in the radar device 10 tends to increase. Therefore, when the number of antennas of the radar device 10 is small, for example, according to Arrangement Example 2 in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion-symmetric, and the arrangement directions of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inversion-symmetric, the overlap of the grating lobe powers can be suppressed, so that the suppression performance of the grating lobes can be improved.

[0392] As described above, in Arrangement Condition 2, since the transmission antenna 106 includes the first diagonal antenna group arranged in the first diagonal direction and the second diagonal antenna group arranged in the second diagonal direction, compared with Arrangement Condition 1, the aperture length in the vertical direction of the virtual receiving array can be further expanded, and the angular measurement accuracy or resolution in the vertical direction in the radar device 10 can be improved.

[0393] Also, in Arrangement Condition 2, as described above, by dispersing the directions in which the grating lobes occur within the two-dimensional plane composed of the horizontal and vertical directions, it is possible to suppress the vertical grating lobes generated when the slopes in the first to fourth diagonal directions are set to be steeper with respect to the horizontal direction. Thereby, the aperture length in the vertical direction of the virtual receiving array can be further expanded, and the angular measurement accuracy or resolution in the vertical direction in the radar device 10 can be improved.

[0394] For example, even if the second diagonal antenna group and the fourth diagonal antenna group of the comparative arrangement 2b are arranged at arbitrary positions with respect to the first diagonal antenna group and the third diagonal antenna group of the comparative arrangement 2a, a similar grating lobe suppression effect can be obtained. Similarly, even if the second diagonal antenna group and the third diagonal antenna group of the comparative arrangement 2d are arranged at arbitrary positions with respect to the first diagonal antenna group and the fourth diagonal antenna group of the comparative arrangement 2c, a similar grating lobe suppression effect can be obtained.

[0395] Therefore, in Arrangement Example 2, for example, the first diagonal antenna group and the second diagonal antenna group can be arranged so that their horizontal positions do not overlap with each other, and a transmission antenna element with a larger vertical size (for example, a size of one wavelength or more) can be arranged.

[0396] Similarly, in Arrangement Example 2, for example, the third diagonal antenna group and the fourth diagonal antenna group can be arranged so that their horizontal positions do not overlap with each other, and a reception antenna element with a larger vertical size (for example, a size of one wavelength or more) can be arranged.

[0397] Therefore, in Arrangement Example 2, since the antenna elements of the transmission antenna 106 and the reception antenna 202 can be arranged in a row in the diagonal direction, an antenna element with a large vertical size (for example, an antenna element with a size of one wavelength or more) can be arranged.

[0398] Note that even when the relative positional relationship between the transmission antenna 106 and the reception antenna 202 is different in the arrangement of the virtual reception array, the same virtual reception array arrangement can be configured. Therefore, the positional relationship between the transmission antenna 106 and the reception antenna 202 is not limited to the example of the antenna arrangement shown in FIG. 80 and may be set arbitrarily. This also applies to other example arrangement configurations described below. For example, the distance between the transmission antenna 106 and the reception antenna 202 may be a distance sufficiently wider than the antenna element size, or may be an arrangement shifted horizontally so that the vertical directions do not overlap.

[0399] As described above, in Arrangement Example 2, in the radar device 10, the transmission antenna 106 includes, for example, a first diagonal antenna group arranged in a first diagonal direction and a second diagonal antenna group arranged in a second diagonal direction. Further, the reception antenna 202 includes, for example, a third diagonal antenna group arranged in a third diagonal direction and a fourth diagonal antenna group arranged in a fourth diagonal direction. In the antenna arrangement of the radar device 10, the first diagonal direction and the second diagonal direction are different from each other, and the third diagonal direction and the fourth diagonal direction are different from each other.

[0400] With this antenna arrangement configuration, in the MIMO array arrangement of the radar device 10, antenna elements of any vertical direction (for example, the vertical direction) size can be applied, and grating lobes generated in the virtual reception array can be suppressed.

[0401] Also, in Arrangement Example 2, as described above, due to the difference in the arrangement direction of each of the first to fourth diagonal antenna groups in the transmission antenna 106 and the reception antenna 202, a grating lobe suppression effect can be obtained. Therefore, in Arrangement Example 2, for example, the element intervals of the transmission antenna 106 and the reception antenna 202 can be arbitrarily set. Thereby, for example, according to the setting of at least one of the element interval of the transmission antenna 106 and the element interval of the reception antenna 202, the aperture length of the virtual reception array can be expanded, so that the angle measurement accuracy and angle separation performance in the vertical and horizontal directions in the radar device 10 can be improved.

[0402] Therefore, according to Arrangement Example 2, while suppressing grating lobes, the angle measurement accuracy or resolution in the radar device 10 can be improved.

[0403] In addition, in Arrangement Example 2, in at least one of the transmission antenna 106 and the reception antenna 202, antenna elements may be further added to the antenna configuration shown in FIG. 80. In other words, each of the transmission antenna 106 and the reception antenna 202 of the radar device 10 only needs to include at least the antenna elements in the arrangement shown in FIG. 80. In this case, for example, a virtual antenna is added additively to the virtual reception array arrangement shown in Equation (16). For example, by adding antenna elements to at least one of the transmission antenna 106 and the reception antenna 202, another virtual antenna is added to the virtual reception array arrangement shown in FIG. 80. Even in the case of the antenna arrangement including such Arrangement Example 2, the effects of Arrangement Example 2 described above are maintained, and the same effects as those of Arrangement Example 2 can be obtained.

[0404] For example, antennas may be further added to the antenna configuration of Arrangement Example 2. By adding antennas, it becomes easier to further reduce the grating lobes or side lobe levels suppressed by Arrangement Example 2 described above. Therefore, false detections during angle measurement in the radar device 10 can be reduced, and the angle measurement performance can be improved. Note that the addition of antennas can be similarly applied to subsequent arrangement examples or modification examples, and the same effects can be obtained.

[0405] Also, in the MIMO array arrangement of Arrangement Example 2, an arrangement in which the horizontal direction and the vertical direction are interchanged may be applied. In this case, a virtual reception array arrangement in which the horizontal direction and the vertical direction are interchanged is obtained, and angle separation performance in which the horizontal direction and the vertical direction are interchanged is obtained. Note that the interchange of the horizontal direction and the vertical direction in the MIMO array arrangement can be similarly applied to subsequent arrangement examples or modification examples, and in the subsequent arrangement examples, a virtual reception array arrangement in which the horizontal direction and the vertical direction are interchanged is obtained.

[0406] In the MIMO antenna arrangement of Arrangement Example 2, the arrangement of the transmission antenna 106 and the arrangement of the reception antenna 202 may be swapped. In this case, for example, the arrangement of the reception antenna 202 shown in Arrangement Example 2 may be used as the arrangement of the transmission antenna 106, and the arrangement of the transmission antenna 106 shown in Arrangement Example 2 may be used as the arrangement of the reception antenna 202. Even if the arrangement of the transmission antenna 106 and the arrangement of the reception antenna 202 are swapped, since the arrangement of the virtual reception array remains the same, the same effects can be obtained. Note that the swapping of the arrangement of the transmission antenna 106 and the arrangement of the reception antenna 202 can be similarly applied to the transitional arrangement example or the modified example.

[0407] <Arrangement Example 2a> FIG. 87 is a diagram showing an arrangement example (for example, a MIMO antenna arrangement example) of a transmission antenna 106 (for example, represented as Tx) and a reception antenna 202 (for example, represented as Rx) according to Arrangement Example 2a.

[0408] In the example shown in FIG. 87, the number of transmission antennas N Tx is six (for example, Tx#1, Tx#2, Tx#3, Tx#4, Tx#5, and Tx#6), and the number of reception antennas Na is eight (for example, Rx#1, Rx#2, Rx#3, Rx#5, Rx#6, Rx#7, and Rx#8).

[0409] In FIG. 87, N Tx = The six transmission antennas Tx#1 to #6 include a first diagonal antenna group Tx#1 to #3 arranged in a first diagonal direction and a second diagonal antenna group Tx#4 to #6 arranged in a second diagonal direction. In FIG. 87, the first diagonal direction and the second diagonal direction are not parallel and are different from each other.

[0410] Also, in FIG. 87, the eight reception antennas Rx#1 to #8 include a third diagonal antenna group Rx#1 to #4 arranged in a third diagonal direction and a fourth diagonal antenna group Rx#5 to #8 arranged in a fourth diagonal direction. In FIG. 87, the third diagonal direction and the fourth diagonal direction are not parallel and are different from each other.

[0411] From these, the antenna arrangement of Arrangement Example 2a shown in FIG. 87 satisfies Arrangement Condition 2.

[0412] Also, in Arrangement Example 2a, as shown in FIG. 87, the arrangement direction of the first diagonal antenna group and the arrangement direction of the fourth diagonal antenna group are the same and parallel. Also, in Arrangement Example 2a, as shown in FIG. 87, the arrangement direction of the second diagonal antenna group and the arrangement direction of the third diagonal antenna group are the same and parallel. That is, in FIG. 87, the first diagonal direction and the fourth diagonal direction are the same direction, and the second diagonal direction and the third diagonal direction are the same direction.

[0413] Thus, in an antenna arrangement that satisfies Arrangement Condition 2, the first diagonal direction may be set to a slope that coincides with the third diagonal direction or the fourth diagonal direction, and the second diagonal direction may be set to a slope that coincides with the third diagonal direction or the fourth diagonal direction.

[0414] For example, the first diagonal antenna groups Tx#1 to #3 shown in FIG. 87 are shifted horizontally at intervals of two wavelengths from left to right in the figure, and are also shifted upward at intervals of two wavelengths vertically at the same time. Also, the second diagonal antenna groups Tx#4 to #6 shown in FIG. 87 are shifted horizontally at intervals of two wavelengths from left to right in the figure, and are also shifted downward at intervals of two wavelengths vertically at the same time. In other words, the first diagonal antenna groups Tx#1 to #3 and the second diagonal antenna groups Tx#4 to #6 are arranged in horizontal direction reversal symmetry.

[0415] Here, the transmission antenna 106 of Arrangement Example 1 (for example, FIG. 8) is arranged horizontally. On the other hand, the transmission antenna 106 of Arrangement Example 2a is arranged diagonally as shown in FIG. 87. In other words, since the transmission antenna 106 of Arrangement Example 2a is arranged two-dimensionally in the horizontal and vertical directions, Arrangement Example 2a can expand the vertical aperture more than Arrangement Example 1.

[0416] Also, for example, the third diagonal antenna groups Rx#1 to #4 shown in FIG. 87 are shifted horizontally at intervals of 0.5 wavelengths from right to left in the figure, and are also shifted upward at intervals of 0.5 wavelengths vertically at the same time. Further, the fourth diagonal antenna groups Rx#5 to #8 shown in FIG. 87 are shifted horizontally at intervals of 0.5 wavelengths from left to right in the figure, and are also shifted upward at intervals of 0.5 wavelengths vertically at the same time. In other words, the third diagonal antenna groups Rx#1 to #4 and the fourth diagonal antenna groups Rx#5 to #8 are arranged in a horizontally inversion-symmetric manner.

[0417] FIG. 88 is a diagram showing an example of the arrangement of a virtual reception array obtained by the antenna arrangement shown in FIG. 87. From the arrangements of the transmission antennas Tx#1 to Tx#6 and the reception antennas Rx#1 to Rx#8, the position coordinates of the virtual antennas VA#1 to #48 constituting the virtual reception array antenna are calculated from Equation (16).

[0418] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangement according to the above-described arrangement example 2a is applied will be described.

[0419] FIG. 89 is the MIMO array arrangement of Arrangement Example 2a (D H = 0.5λ, D V = 0.5λ). The figure shows the direction estimation result when the beamformer method is used as the arrival direction estimation algorithm of the direction estimation unit 213. In FIG. 89, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0420] Note that Fig. 89(a) is a diagram showing the normalized power values in the two-dimensional directions where the horizontal axis is the horizontal direction and the vertical axis is the vertical direction, presented as a grayscale color map. Also, Fig. 89(b) is a diagram showing Fig. 89(a) with the horizontal axis in the horizontal direction and the vertical axis representing the normalized power values, and the normalized power values are similarly shown as a grayscale color map. Further, Fig. 89(c) is a diagram showing Fig. 89(a) with the horizontal axis in the vertical direction and the vertical axis representing the normalized power values, and the normalized power values are similarly shown as a grayscale color map. Note that in Fig. 89, the normalized power value may be represented by the decibel value (dB) normalized by the peak power, and the same applies to the plots of the direction estimation results in the following other examples.

[0421] As shown in the virtual receiving array arrangement shown in Fig. 88, each virtual antenna is arranged at intervals that include many intervals of one wavelength or more in both the horizontal and vertical directions, and the intervals between the virtual antennas are intervals at which grating lobes can occur. In contrast, as shown in Fig. 89, it can be seen that in a direction different from the peak direction of the target true value direction, the grating lobes are suppressed to about -6 dB or less.

[0422] Note that, for example, in the antenna arrangement of Arrangement Example 2a shown in Fig. 87, the arrangement directions of each of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion-symmetric, and the arrangement directions of each of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inversion-symmetric. For example, the inclinations of the first to fourth diagonal directions are 45 degrees with respect to the horizontal direction. In this case, as shown in Fig. 89(a), the arrangement has the widest intervals in the horizontal and vertical two-dimensional angular directions where grating lobes occur.

[0423] An antenna arrangement in which the intervals in the horizontal and vertical two-dimensional angular directions where such grating lobes occur are larger is more suitable, for example, as the number of antennas of the radar device 10 is smaller. For example, the smaller the number of antennas of the radar device 10, the wider the beam width of the main beam in direction estimation tends to be. Therefore, when the directions of the grating lobes to be suppressed are close, the smaller the number of antennas of the radar device 10, the more the grating lobe powers overlap due to the spread of the beam width, and the power of the grating lobes can increase. For this reason, the smaller the number of antennas of the radar device 10, the more deteriorated the suppression performance of the grating lobes, and the higher the probability of false detection in the radar device 10. Therefore, when the number of antennas of the radar device 10 is small, for example, according to Arrangement Example 2 in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inversion-symmetrical, and the arrangement directions of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inversion-symmetrical, the overlap of the grating lobe powers can be suppressed, so that the suppression performance of the grating lobes can be improved.

[0424] Also, in Arrangement Example 2a, the arrangement direction of the first diagonal antenna group and the arrangement direction of the fourth diagonal antenna group coincide and are parallel. Also, in Arrangement Example 2a, the arrangement direction of the second diagonal antenna group and the arrangement direction of the third diagonal antenna group coincide and are parallel. Thus, in Arrangement Example 2a, the first diagonal direction is set to a slope that coincides with the third diagonal direction or the fourth diagonal direction, and the second diagonal direction is set to a slope that coincides with the third diagonal direction or the fourth diagonal direction, whereby the same suppression effect of the grating lobes as in Arrangement Example 2 can be obtained.

[0425] Also, in Arrangement Example 2a, as shown in FIG. 87, since the antenna elements of the transmission antenna 106 and the reception antenna 202 can be arranged in a row in the diagonal direction, it is possible to arrange antenna elements having a large vertical size (for example, antenna elements having a size of one wavelength or more).

[0426] As described above, in Arrangement Example 2a, as in Arrangement Example 2, in the MIMO array arrangement of the radar device 10, antenna elements of any vertical direction (for example, the vertical direction) size can be applied, and grating lobes generated in the virtual reception array can be suppressed.

[0427] <Arrangement Example 2b> In Arrangement Example 2b, for example, either one of the first diagonal direction and the second diagonal direction that satisfies Arrangement Condition 2 may coincide with and be parallel to the third diagonal direction or the fourth diagonal direction, and the other of the first diagonal direction and the second diagonal direction may be different without coinciding with the third diagonal direction and the fourth diagonal direction.

[0428] FIG. 90 is a diagram showing an arrangement example (for example, a MIMO antenna arrangement example) of the transmission antenna 106 (for example, represented as Tx) and the reception antenna 202 (for example, represented as Rx) according to Arrangement Example 2b.

[0429] In the example shown in FIG. 90, the number of transmission antennas N Tx is six (for example, Tx#1, Tx#2, Tx#3, Tx#4, Tx#5, and Tx#6), and the number of reception antennas Na is eight (for example, Rx#1, Rx#2, Rx#3, Rx#5, Rx#6, Rx#7, and Rx#8).

[0430] In FIG. 90, the N Tx = six transmission antennas Tx#1 to #6 include a first diagonal antenna group Tx#1 to #3 arranged in the first diagonal direction and a second diagonal antenna group Tx#4 to #6 arranged in the second diagonal direction. In FIG. 90, the first diagonal direction and the second diagonal direction are not parallel and are different diagonal directions from each other.

[0431] Also, in FIG. 90, the Na = eight reception antennas Rx#1 to #8 include a third diagonal antenna group Rx#1 to #4 arranged in the third diagonal direction and a fourth diagonal antenna group Rx#5 to #8 arranged in the fourth diagonal direction. In FIG. 90, the third diagonal direction and the fourth diagonal direction are not parallel and are different directions from each other.

[0432] From these, the antenna arrangement of Arrangement Example 2b shown in FIG. 90 satisfies Arrangement Condition 2.

[0433] Also, in Arrangement Example 2b, as shown in FIG. 90, the arrangement direction of the first diagonal antenna group and the arrangement direction of the fourth diagonal antenna group do not coincide and are different directions. On the other hand, as shown in FIG. 90, the arrangement direction of the second diagonal antenna group and the arrangement direction of the third diagonal antenna group coincide and are parallel. That is, in FIG. 90, the first diagonal direction and the fourth diagonal direction are the same direction, and the second diagonal direction and the third diagonal direction are different directions.

[0434] Thus, even when either one of the first diagonal direction and the second diagonal direction is set to an inclination that coincides with the third diagonal direction or the fourth diagonal direction, Arrangement Condition 2 is satisfied.

[0435] For example, the first diagonal antenna groups Tx#1 to #3 shown in FIG. 90 are shifted horizontally at intervals of two wavelengths from left to right in the figure, and simultaneously shifted upward at intervals of two wavelengths vertically. Also, the second diagonal antenna groups Tx#4 to #6 shown in FIG. 90 are shifted horizontally at intervals of two wavelengths from left to right in the figure, and simultaneously shifted downward at intervals of two wavelengths vertically. In other words, the first diagonal antenna groups Tx#1 to #3 and the second diagonal antenna groups Tx#4 to #6 are arranged in a horizontally inversion-symmetric manner.

[0436] Here, the transmission antenna 106 of Arrangement Example 1 (for example, FIG. 8) is arranged horizontally. On the other hand, the transmission antenna 106 of Arrangement Example 2b is arranged diagonally as shown in FIG. 90. In other words, since the transmission antenna 106 of Arrangement Example 2b is arranged two-dimensionally in the horizontal and vertical directions, Arrangement Example 2b can expand the vertical aperture more than Arrangement Example 1.

[0437] Also, for example, the third diagonal antenna groups Rx#1 to #4 shown in FIG. 90 are shifted horizontally at intervals of 0.5 wavelengths from right to left in the figure, and simultaneously shifted upward at intervals of 0.5 wavelengths vertically. Also, the fourth diagonal antenna groups Rx#5 to #8 shown in FIG. 90 are shifted horizontally at intervals of 0.5 wavelengths from left to right in the figure, and simultaneously shifted upward at intervals of 1 wavelength vertically. In other words, the third diagonal antenna groups Rx#1 to #4 and the fourth diagonal antenna groups Rx#5 to #8 are arranged in a non-horizontally inversion-symmetric manner.

[0438] FIG. 91 is a diagram showing an example of the arrangement of a virtual reception array obtained by the antenna arrangement shown in FIG. 90. From the arrangements of the transmission antennas Tx#1 to Tx#6 and the reception antennas Rx#1 to Rx#8, the position coordinates of the virtual antennas VA#1 to #48 constituting the virtual reception array antenna are calculated from Equation (16).

[0439] Next, an example of the direction estimation result (computer simulation result) when the antenna arrangement according to the above-described arrangement example 2b is applied will be described.

[0440] FIG. 92 is the MIMO array arrangement (D H = 0.5λ, D V = 0.5λ) of arrangement example 2b, showing the direction estimation result when the beamformer method is used as the arrival direction estimation algorithm of the direction estimation unit 213. In FIG. 92, as an example, the output of the arrival direction estimation evaluation function value in the horizontal direction ±90-degree range and the vertical direction ±90-degree range when the target true value is horizontal 0 degrees and vertical 0 degrees is plotted.

[0441] Note that Fig. 92(a) is a diagram showing the normalized power values in a two-dimensional direction with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction using a grayscale color map. Fig. 92(b) is a diagram showing Fig. 92(a) with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value, and the normalized power value is also shown using a grayscale color map. Fig. 92(c) is a diagram showing Fig. 92(a) with the horizontal axis being the vertical direction and the vertical axis being the normalized power value, and the normalized power value is also shown using a grayscale color map. In Fig. 92, the normalized power value may be represented by a decibel value (dB) normalized by the peak power, and the same applies to the plots of the direction estimation results in the following other examples.

[0442] As shown in the virtual reception array arrangement shown in Fig. 91, each virtual antenna is arranged at intervals of one wavelength or more in both the horizontal and vertical directions, and the interval between the virtual antennas is an interval at which grating lobes can occur. In contrast, as shown in Fig. 92, it can be seen that the grating lobes are suppressed to about -4 dB or less in a direction different from the peak direction of the target true value direction.

[0443] In Arrangement Example 2b, for example, the arrangement direction of the first diagonal antenna group and the arrangement direction of the fourth diagonal antenna group do not match and are different directions, but the arrangement direction of the second diagonal antenna group and the arrangement direction of the third diagonal antenna group match and are parallel. Thus, even when either one of the first diagonal direction and the second diagonal direction has an inclination that matches the third diagonal direction or the fourth diagonal direction, Arrangement Condition 2 is satisfied, and a grating lobe suppression effect similar to that of Arrangement Example 2 can be obtained.

[0444] Also, in Arrangement Example 2b, as shown in Fig. 90, since the antenna elements of the transmission antenna 106 and the reception antenna 202 can be arranged in a row in the diagonal direction, it is possible to arrange antenna elements having a large size in the vertical direction (for example, antenna elements having a size of one wavelength or more).

[0445] As described above, in Arrangement Example 2b, similar to Arrangement Example 2, in the MIMO array arrangement of the radar device 10, antenna elements of any vertical direction (for example, the vertical direction) size can be applied, and grating lobes generated in the virtual reception array can be suppressed.

[0446] Hereinafter, a modification example of Arrangement Example 2 will be described.

[0447] For the reception antennas of Arrangement Example 2 (or Arrangement Examples 2a and 2b), for example, Modification Examples 1 to 4, 6, and 7 of Arrangement Example 1 may be similarly applied. Even when Modification Examples 1 to 4, 6, and 7 of Arrangement Example 1 are applied to Arrangement Example 2, the same effects as Arrangement Example 2 can be obtained. For example, in the description of each of Modification Examples 1 to 4, 6, and 7 of Arrangement Example 1, "Arrangement Example 1" is replaced with "Arrangement Example 2", and further, the "first diagonal antenna group" and the "second diagonal antenna group" of Arrangement Example 1 are replaced with the "third diagonal antenna group" and the "fourth diagonal antenna group" of Arrangement Example 2, respectively (read and replaced) and applied. Thereby, even in Arrangement Example 2, the same effects as Modification Examples 1 to 4, 6, and 7 of Arrangement Example 1 can be obtained. Note that the description of the same application as Modification Examples 1 to 4, 6, and 7 of Arrangement Example 1 in Arrangement Example 2 will be omitted.

[0448] Hereinafter, an additional part will be described for the case where the same content as Modification Examples 1 to 4, 6, and 7 of Arrangement Example 1 is applied to the "first diagonal antenna group" and the "second diagonal antenna group" included in the transmission antenna 106 of Arrangement Example 2.

[0449] Hereinafter, the additional parts of Modification Examples 1 to 4, 6, and 7 of Arrangement Example 2 corresponding to Modification Examples 1 to 4, 6, and 7 of Arrangement Example 1 will be described.

[0450] [Modification Example 1 of Arrangement Example 2] In Modification Example 1 of Arrangement Example 2, the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group may be wider than that of Arrangement Example 2 (or Arrangement Examples 2a and 2b), for example.

[0451] For example, in the case of Arrangement Example 2, as shown in FIG. 80, the minimum distance (e.g., the distance between Tx#3 and Tx#4) between the first diagonal antenna group and the second diagonal antenna group is N a set to be narrower than the horizontal aperture length of N a reception antennas 202 (e.g., the distance between Rx#4 and Rx#8). In Modification Example 1 of Arrangement Example 2, for example, the minimum distance (e.g., the distance between Tx#3 and Tx#4) between the first diagonal antenna group and the second diagonal antenna group may be set wider than the horizontal aperture length of N

[0452] reception antennas 202. Even in this case, the same effects as those of Arrangement Example 2 can be obtained. Also, by increasing the minimum distance between the first diagonal antenna group and the second diagonal antenna group, the peak in the target true value direction in the horizontal direction becomes sharper, so that the angular measurement accuracy or estimation accuracy in the horizontal direction of the radar device 10 can be improved. Note that in Modification Example 1 of Arrangement Example 2, similar to Modification Example 1 of Arrangement Example 1, the side lobe level in the horizontal direction of the peak in the target true value direction may increase. Therefore, depending on requirements such as the detection target assumed by the radar device 10, the distance (e.g., the minimum distance) between the first diagonal antenna group and the second diagonal antenna group may be set within a suitable range.

[0453] [Modification Example 2 of Arrangement Example 2] In Modification Example 2 of Arrangement Example 2, for example, the distance (e.g., the minimum distance) between the first diagonal antenna group and the second diagonal antenna group may be made closer compared to Arrangement Example 2 (or Arrangement Examples 2a, 2b). Also, in Modification Example 2 of Arrangement Example 2, for example, some of the antennas included in each of the first diagonal antenna group and the second diagonal antenna group may overlap.

[0454] For example, in the case of Arrangement Example 2, as shown in FIG. 80, the minimum distance (the distance between Tx#3 and Tx#4) between the first diagonal antenna group Tx#1~#3 and the second diagonal antenna group Tx#4~#6 is N a narrower than the horizontal aperture length of the reception antennas 202 (e.g., the distance between Rx#4 and Rx#8).

[0455] In Modification Example 2 of Arrangement Example 2, for example, the minimum distance between the first diagonal antenna group Tx#1 to #3 and the second diagonal antenna group Tx#4 to #6 (the distance between Tx#3 and Tx#4) may be arranged to be closer.

[0456] Alternatively, in Modification Example 2 of Arrangement Example 2, for example, some antennas of the first diagonal antenna group and the second diagonal antenna group may be arranged so as to overlap.

[0457] Even in these cases, the same effects as those of Arrangement Example 2 and the same effects as those of Modification Example 2 of Arrangement Example 1 can be obtained.

[0458] [Modification Example 3 of Arrangement Example 2] In Modification Example 3 of Arrangement Example 2, for example, the inclination of the first diagonal antenna group and the second diagonal antenna group (for example, the position change in the vertical direction with respect to the horizontal direction) may be set to be gentler than that in Arrangement Example 2. Even in this case, the same effects as those of Arrangement Example 2 and the same effects as those of Modification Example 3 of Arrangement Example 1 can be obtained.

[0459] [Modification Example 4 of Arrangement Example 2] For example, in Arrangement Example 2 shown in FIG. 80, the case where the first diagonal antenna group Tx#1 to #3 and the second diagonal antenna group Tx#4 to #6 are arranged in horizontal direction inversion symmetry has been described, but it is not limited thereto. The first diagonal antenna group and the second diagonal antenna group do not have to be arranged in horizontal direction inversion symmetry. For example, the first diagonal direction and the second diagonal direction may be different directions instead of being parallel. Thereby, the same effects as those of Arrangement Example 2 can be obtained.

[0460] For example, a) the first diagonal antenna group and the second diagonal antenna group may have an asymmetric inclination, or different antenna intervals may be set in each of the horizontal direction and the vertical direction.

[0461] Also, for example, b) the arrangement in which the positions of the first diagonal antenna group and the second diagonal antenna group are shifted in the vertical direction may be used.

[0462] Further, for example, the number of antennas included in each of the first diagonal antenna group and the second diagonal antenna group may be different.

[0463] Further, for example, the arrangements of the first diagonal antenna group and the second diagonal antenna group may be an arrangement in which any two or three of the following arrangements are combined: a) an arrangement in which the first diagonal antenna group and the second diagonal antenna group have asymmetric inclinations, b) an arrangement in which the number of antennas included in each of the first diagonal antenna group and the second diagonal antenna group is different, and c) an arrangement in which the positions of the first diagonal antenna group and the second diagonal antenna group are shifted in the vertical direction.

[0464] By these, effects similar to those of Arrangement Example 2 and effects similar to those of Modification Example 4 of Arrangement Example 1 can be obtained.

[0465] Further, a modification of the arrangement of the first diagonal antenna group and the second diagonal antenna group included in the transmission antenna 106 as described above may be combined with a modification of the arrangement of the third diagonal antenna group and the fourth diagonal antenna group included in the reception antenna 202.

[0466] FIG. 93 shows an example (for example, referred to as "Arrangement Example 2-4a") in which the first diagonal antenna group Tx#1~#3 and the second diagonal antenna group Tx#4~#6 have a horizontally symmetric inclination arrangement, and the third diagonal antenna group Rx#1~#4 and the fourth diagonal antenna group Rx#5~#8 have a horizontally asymmetric arrangement. Even in the case of Arrangement Example 2-4a, effects similar to those of Arrangement Example 2 can be obtained.

[0467] FIG. 94 shows an example (for example, referred to as "Arrangement Example 2-4b") in which the first diagonal antenna group Tx#1~#3 and the second diagonal antenna group Tx#4~#6 have a horizontally asymmetric inclination arrangement, and the third diagonal antenna group Rx#1~#4 and the fourth diagonal antenna group Rx#5~#8 have a horizontally symmetric arrangement. Even in the case of Arrangement Example 2-4b, effects similar to those of Arrangement Example 2 can be obtained.

[0468] FIG. 95 shows an example (e.g., referred to as "Arrangement Example 2-4c") where the first diagonal antenna groups Tx#1 to #3 and the second diagonal antenna groups Tx#4 to #6 are arranged with an asymmetric inclination in the horizontal direction, and the third diagonal antenna groups Rx#1 to #4 and the fourth diagonal antenna groups Rx#5 to #8 are arranged asymmetrically in the horizontal direction. Even in the case of Arrangement Example 2-4c, the same effects as those of Arrangement Example 2 can be obtained.

[0469] Also, in Arrangement Condition 2, either one of the first diagonal direction and the second diagonal direction may be arranged in the horizontal direction. Also, in Arrangement Condition 2, either one of the third diagonal direction and the fourth diagonal direction may be arranged in the horizontal direction.

[0470] For example, FIG. 96 shows an example (e.g., referred to as "Arrangement Example 2-4d") where the first diagonal antenna groups Tx#1 to #3 are arranged in a diagonal direction and the second diagonal antenna groups Tx#4 to #6 are arranged in the horizontal direction. In FIG. 96, for example, the arrangements of the third diagonal antenna groups Rx#1 to #4 and the fourth diagonal antenna groups Rx#5 to #8 are horizontally inversion-symmetric arrangements. Thus, even if either one of the first diagonal direction and the second diagonal direction is arranged in the horizontal direction, the same effects as those of Arrangement Example 2 can be obtained.

[0471] [Modification Example 6 of Arrangement Example 2] In at least one of the transmitting antenna 106 (e.g., the first diagonal antenna group and the second diagonal antenna group) and the receiving antenna 202 (e.g., the third diagonal antenna group and the fourth diagonal antenna group), the interval between adjacent antennas is not limited to an equal interval and may be an unequal interval.

[0472] For example, the arrangement of at least one of the first diagonal antenna group, the second diagonal antenna group, the third diagonal antenna group, and the fourth diagonal antenna group may be set to an unequal interval antenna arrangement. Also by this, the same effects as those of Arrangement Example 2 can be obtained.

[0473] [Modification Example 7 of Arrangement Example 2] In Modification Example 7 of Configuration Example 2, for example, the multi-stage configuration of the antenna arrangement described in Configuration Example 2 and Modification Examples 1 to 4 and 6 of Configuration Example 2 may be applied.

[0474] Examples of the multi-stage configuration include a configuration in which the first diagonal antenna group and the second diagonal antenna group included in the transmission antenna 106 are arranged in two stages in the vertical direction or in two stages in the horizontal direction, and a configuration in which the third diagonal antenna group and the fourth diagonal antenna group included in the reception antenna 202 are arranged in two stages in the vertical direction or in two stages in the horizontal direction. Alternatively, the multi-stage configuration may be a combination of these configurations.

[0475] Even in the case of the multi-stage configuration, the effects according to Configuration Example 2 described above can be maintained. Further, for example, due to the multi-stage configuration in the horizontal direction, the aperture length of the virtual reception array in the horizontal direction is expanded, and the azimuth angle measurement accuracy or resolution in the horizontal direction of the radar device 10 can be improved. Also, for example, due to the multi-stage configuration in the vertical direction, the aperture length of the virtual reception array in the vertical direction is expanded, and the azimuth angle measurement accuracy or resolution in the vertical direction of the radar device 10 can be improved. Further, for example, due to the multi-stage configuration in the vertical and horizontal directions, the aperture lengths of the virtual reception arrays in the vertical and horizontal directions are expanded, and the azimuth angle measurement accuracies or resolutions in the vertical and horizontal directions of the radar device 10 can be improved.

[0476] Note that in the case of the multi-stage configuration, the common arrangement of the transmission antenna Tx or the reception antenna Rx may be configured in multiple stages in at least one of the vertical and horizontal directions, or different arrangements of the transmission antenna Tx or the reception antenna Rx may be configured in multiple stages in at least one of the vertical and horizontal directions.

[0477] Also, different antenna elements may be used in combination in the multi-stage configuration described above. For example, the plurality of transmission antennas 106 may include an antenna element for long range (LR) and an antenna element for short range (SR).

[0478] For example, in a multi-stage configuration, a long-range (LR) antenna element may be applied in the first stage, and a short-range (SR) antenna element may be used in combination in the second stage. For example, when the transmission antenna 106 is arranged in a two-stage multi-stage configuration in the vertical direction, a long-range (LR) antenna element may be applied in the first stage, and a short-range (SR) antenna element may be applied in the second stage.

[0479] In addition, when the vertical and horizontal sizes of the long-range (LR) antenna element are large, one-stage elements may be shifted horizontally so that the first-stage transmission antenna 106 and the second-stage transmission antenna 106 do not overlap.

[0480] Thus, when using an LR antenna and an SR antenna for the transmission antenna 106, for example, an SR antenna (for example, an antenna having characteristics with a wide viewing angle) may be applied to the reception antenna 202. Thereby, while maintaining the effect of Arrangement Example 2, it is possible to cope with the detection ranges of both the LR and SR modes.

[0481] The modification of Arrangement Example 2 has been described above.

[0482] Next, a modification specific to Arrangement Condition 2 will be described.

[0483] [Modification of Arrangement Condition 2] In Arrangement Example 2 and the modification of Arrangement Example 2, for example, the inclination in the diagonal direction of each of the transmission antenna 106 and the reception antenna 202 is set to an integer multiple of the basic interval D H in the horizontal direction and an integer multiple of the basic interval D V in the vertical direction. The case has been described.

[0484] That is, in the N Tx transmission antennas 106, the first diagonal antenna group and the second diagonal antenna group are arranged in different diagonal directions. Further, the first diagonal antenna group is shifted at intervals of dTH1×D H in the horizontal direction and also simultaneously at intervals of dTV1×D VThey are arranged in a diagonal direction that shifts at intervals of H and shifts in the horizontal direction by dTH2×D and simultaneously in the vertical direction by dTV2×D V They are arranged in a diagonal direction that shifts at intervals of

[0485] Also, in the Na receiving antennas 202, the third diagonal antenna group and the fourth diagonal antenna group are arranged in different diagonal directions. Also, the third diagonal antenna group shifts in the horizontal direction by dRH1×D H and shifts simultaneously in the vertical direction by dRV1×D V They are arranged in a diagonal direction that shifts at intervals of H and shifts simultaneously in the vertical direction by dRV2×D V They are arranged in a diagonal direction that shifts at intervals of

[0486] Here, dTH1 and dTV1 are integers of 1 or more, and dTH2 and dTV2 are integers of 1 or more. Also, dRH1 and dRV1 are integers of 1 or more, and dRH2 and dRV2 are integers of 1 or more.

[0487] For example, when dTH1 = dTH2 and dTV1 = dTV2, the first diagonal antenna group and the second diagonal antenna group are symmetrically arranged in the horizontal direction. Also, for example, when dTH1 ≠ dTH2 or dTV1 ≠ dTV2, the first diagonal antenna group and the second diagonal antenna group are asymmetrically arranged in the horizontal direction.

[0488] Similarly, for example, when dRH1 = dRH2 and dRV1 = dRV2, the third diagonal antenna group and the fourth diagonal antenna group are symmetrically arranged in the horizontal direction. Also, for example, when dRH1 ≠ dRH2 or dRV1 ≠ dRV2, the third diagonal antenna group and the fourth diagonal antenna group are asymmetrically arranged in the horizontal direction.

[0489] Note that in Arrangement Example 2 and the modified example of Arrangement Example 2, the inclination of the transmitting antenna 106 and the receiving antenna 202 in the diagonal direction is the basic interval D in the horizontal direction His set to an integral multiple of, and the basic interval D in the vertical direction V is not limited to the case where it is set to an integral multiple of, and D V , D H may be set to an interval that is not an integral multiple of. Even with such an arrangement, the arrangement condition 2 can be satisfied, and the same effect as in Arrangement Example 2 can be obtained.

[0490] [Arrangement Example in the Case of the Smallest Antenna Configuration and the Smallest Number of Antennas for Arrangement Condition 2] Hereinafter, the smallest antenna configuration that satisfies Arrangement Condition Example 2 and an arrangement example in the case of a small number of antennas that satisfy Arrangement Condition 2 will be described. Note that the same effect can be obtained by applying a modification similar to the modification example of Arrangement Example 2 described above to the antenna arrangement described below.

[0491] The minimum number of antennas for Arrangement Condition 2 is, for example, the number of transmission antennas N Tx = 3 and the number of reception antennas Na = 3. In other words, the total number of antennas in the first diagonal antenna group and the second diagonal antenna group is 3, and the total number of antennas in the third diagonal antenna group and the fourth diagonal antenna group is 3.

[0492] FIG. 97 shows an antenna arrangement example with the minimum number of antennas for Arrangement Condition 2 (the number of transmission antennas N Tx = 3 and the number of reception antennas Na = 3). (a) of FIG. 97 shows an example of a MIMO antenna arrangement, and (b) of FIG. 97 shows an example of a virtual reception array arrangement configured by the MIMO antenna arrangement shown in (a) of FIG. 97. Also, in FIG. 97, the scales (scales) of the horizontal axis and the vertical axis are, for example, D H , D V respectively.

[0493] In FIG. 97, the first diagonal antenna group includes Tx#1 and Tx#2, and the second diagonal antenna group includes Tx#2 and Tx#3. Also, in FIG. 97, the third diagonal antenna group includes Rx#1 and Rx#2, and the fourth diagonal antenna group includes Rx#2 and Rx#3.

[0494] Figures 98 to 101 show antenna arrangement examples when the number of antennas satisfying the arrangement condition 2 is small. (a) of Figures 98 to 101 shows an example of MIMO antenna arrangement, and (b) of Figures 98 to 101 shows an example of a virtual reception array arrangement constituted by the MIMO antenna arrangement shown in (a) of Figures 98 to 101. Also, in Figures 98 to 101, the scales of the horizontal axis and the vertical axis are, for example, D H , D V respectively.

[0495] For example, Figures 98 and 99 show antenna arrangement examples when the number of transmission antennas N Tx = 3 and the number of reception antennas Na = 4. In Figures 98 and 99, the first diagonal antenna group includes Tx#1 and Tx#2, the second diagonal antenna group includes Tx#2 and Tx#3, the third diagonal antenna group includes Rx#1 and Rx#2, and the fourth diagonal antenna group includes Rx#3 and Rx#4.

[0496] For example, in the antenna arrangement example shown in Figure 98, even when the vertical size of the transmission antenna 106 is large, the reception antennas 202 are arranged on both sides of the transmission antenna 106, so that the mounting area of the antenna can be reduced.

[0497] Also, for example, in the antenna arrangement example shown in Figure 99, even when the vertical size of the transmission antenna 106 is large, the transmission antenna 106 is arranged on both sides of the reception antennas 202, so that the mounting area of the antenna can be reduced.

[0498] Also, for example, Figures 100 and 101 show antenna arrangement examples when the number of transmission antennas N Tx = 4 and the number of reception antennas Na = 4. In Figures 100 and 101, the first diagonal antenna group includes Tx#1 and Tx#2, the second diagonal antenna group includes Tx#3 and Tx#4, the third diagonal antenna group includes Rx#1 and Rx#2, and the fourth diagonal antenna group includes Rx#3 and Rx#4.

[0499] For example, in the antenna arrangement examples shown in FIGS. 100 and 101, even when the vertical size of the transmitting antenna 106 is large, the receiving antenna 202 is arranged on both sides of the transmitting antenna 106, so that the mounting area of the antenna can be reduced.

[0500] The above describes one embodiment of the present disclosure.

[0501] In one embodiment of the present disclosure, the case where the arrangement directions (for example, diagonal directions) of the receiving antenna 202 are two different directions under Arrangement Condition 1 (for example, FIG. 8) has been described. However, the arrangement directions of the receiving antenna 202 may be three or more different directions. Similarly, under Arrangement Condition 2 (for example, FIG. 80), the case where the respective arrangement directions (for example, diagonal directions) of the transmitting antenna 106 and the receiving antenna 202 are two different directions has been described. However, the respective arrangement directions of the transmitting antenna 106 and the receiving antenna 202 may be three or more different directions. Even in these cases, as described above, the generation directions of the grating lobes corresponding to each arrangement direction are likely to be dispersed, so that the grating lobes can be suppressed as described above.

[0502] Also, the configuration of the radar device according to one embodiment of the present disclosure is not limited to the configuration shown in FIG. 6. For example, the radar device may not include the CFAR unit 211.

[0503] Also, the number of transmitting antennas N Tx in the antenna arrangement described in one embodiment of the present disclosure, parameters such as the number of receiving antennas Na or the antenna interval are examples, and other different values may also be used.

[0504] Further, at least two modifications of Arrangement Example 1 described in one embodiment of the present disclosure may be combined and implemented. Similarly, at least two modifications of Arrangement Example 2 may be combined and implemented. For example, settings such as the number of antennas, inclination, element spacing, or the spacing between diagonal antenna groups in the first diagonal antenna group and the second diagonal antenna group in Arrangement Example 1, and the first to fourth diagonal antenna groups in Arrangement Example 2 may be determined by a combination of at least two modifications of Arrangement Example 1 or Arrangement Example 2.

[0505] In a radar device according to an embodiment of the present disclosure, the radar transmitter and the radar receiver may be individually arranged at physically separated locations. Further, in a radar receiver according to an embodiment of the present disclosure, the direction estimation unit and other components may be individually arranged at physically separated locations.

[0506] Although not shown, a radar device according to an embodiment of the present disclosure has, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, and a working memory such as a RAM (Random Access Memory). In this case, the functions of the above-described respective units are realized by the CPU executing the control program. However, the hardware configuration of the radar device is not limited to such an example. For example, each functional unit of the radar device may be realized as an IC (Integrated Circuit) which is an integrated circuit. Each functional unit may be individually formed into one chip, or may be formed into one chip so as to include a part or all thereof.

[0507] As described above, various embodiments have been described with reference to the drawings, but it goes without saying that the present disclosure is not limited to such examples. It is obvious that a person skilled in the art can conceive of various modification examples or correction examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present disclosure. Further, within the scope not departing from the gist of the disclosure, the respective components in the above-described embodiments may be arbitrarily combined.

[0508] Also, the notation “··· section” in the above-described embodiments may be replaced with other notations such as “··· circuitry”, “··· assembly”, “··· device”, “··· unit”, or “··· module”.

[0509] In each of the above embodiments, the present disclosure has been described by way of example as being configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

[0510] Also, each functional block used in the description of each of the above embodiments is typically realized as an LSI which is an integrated circuit. The integrated circuit may control each functional block used in the description of the above embodiments and may include an input terminal and an output terminal. These may be individually formed into one chip, or may be formed into one chip so as to include some or all of them. Here, it has been described as an LSI, but depending on the degree of integration, it may also be referred to as an IC, a system LSI, a super LSI, or an ultra LSI.

[0511] Also, the method of integrating into an integrated circuit is not limited to an LSI, and it may be realized using an application specific circuit or a general-purpose processor. After manufacturing the LSI, an FPGA (Field Programmable Gate Array) that can be programmed, or a reconfigurable processor that can reconfigure the connection or setting of circuit cells inside the LSI may be used.

[0512] Furthermore, if a technology for integrating into an integrated circuit that replaces an LSI appears due to the progress of semiconductor technology or another derived technology, naturally, the functional blocks may be integrated using that technology. The application of biotechnology or the like is possible as an example.

[0513] <Summary of the Present Disclosure> A radar device according to an embodiment of the present disclosure includes a transmission circuit that transmits a transmission signal using a plurality of transmission antennas, and a reception circuit that receives a reflected wave signal obtained by reflecting the transmission signal from an object using a plurality of reception antennas. Either one of the plurality of transmission antennas or the plurality of reception antennas includes a first antenna group arranged in a first direction and a second antenna group arranged in a second direction different from the first direction. The remaining one of the plurality of transmission antennas or the plurality of reception antennas includes a third antenna group arranged in a third direction different from each of the first direction and the second direction, where the interval between adjacent antennas is equal to or greater than one wavelength of the transmission signal.

[0514] In an embodiment of the present disclosure, the radar device is installed in a vehicle, and the first direction and the second direction are different directions with respect to a vertical direction, which is a height direction of the vehicle, and a horizontal direction, which is a direction orthogonal to the straight-ahead direction of the vehicle.

[0515] In an embodiment of the present disclosure, the first direction and the second direction are different directions with respect to a vertical direction, which is a direction of gravity, and a horizontal direction, which is a direction orthogonal to the direction of gravity.

[0516] In an embodiment of the present disclosure, the third direction is a direction that coincides with the horizontal direction.

[0517] In an embodiment of the present disclosure, a minimum interval between the first antenna group and the second antenna group is wider than an aperture length of the third antenna group.

[0518] In an embodiment of the present disclosure, the first antenna group and the second antenna group include one or more antennas shared therebetween.

[0519] In an embodiment of the present disclosure, an antenna arrangement included in the first antenna group and an antenna arrangement included in the second antenna group are in a line-symmetric relationship with respect to a line perpendicular to the third direction.

[0520] In one embodiment of the present disclosure, the distance between adjacent antennas in the third antenna group in the horizontal direction is dT×D H wherein the distance between adjacent antennas included in the first antenna group in the horizontal direction is dRH1×D H wherein the distance between adjacent antennas included in the first antenna group in the vertical direction is dRV×D V wherein the distance between adjacent antennas included in the second antenna group in the horizontal direction is dRH2×D H wherein the distance between adjacent antennas included in the second antenna group in the vertical direction is dRV×D V wherein the D H and the D V are values within the range of 0.45 times to 0.8 times the wavelength of the transmission signal, the dT is a value of 2 or more, and each of the dRH1 and the dRH2 is a value of 1 or more

[0521] In one embodiment of the present disclosure, in each of the third antenna group, the first antenna group, and the second antenna group, the distance between adjacent antennas is equally spaced.

[0522] In one embodiment of the present disclosure, in at least one of the third antenna group, the first antenna group, and the second antenna group, the distance between adjacent antennas includes one or more unequal intervals.

[0523] In one embodiment of the present disclosure, the third antenna group includes a plurality of sets of at least some of the antennas arranged in the third direction.

[0524] In one embodiment of the present disclosure, either one of the plurality of transmitting antennas or the plurality of receiving antennas includes a plurality of the first antenna group and the second antenna group.

[0525] In one embodiment of the present disclosure, the plurality of transmitting antennas include at least two types of antenna elements having different sizes.

[0526] In one embodiment of the present disclosure, the other one of the plurality of transmitting antennas or the plurality of receiving antennas includes a fourth antenna group arranged in a fourth direction different from the third direction.

[0527] In one embodiment of the present disclosure, the other one of the plurality of transmitting antennas or the plurality of receiving antennas includes a fourth antenna group arranged in a fourth direction different from the third direction, the third direction and the fourth direction are different directions with respect to the horizontal direction and the vertical direction.

[0528] In one embodiment of the present disclosure, the first direction, the second direction, the third direction, and the fourth direction are different from each other.

[0529] In one embodiment of the present disclosure, the third antenna group and the fourth antenna group include one or more antennas shared therebetween.

[0530] In one embodiment of the present disclosure, the interval between adjacent antennas in the third antenna group in the horizontal direction is dTH1×D H and the interval between adjacent antennas included in the third antenna group in the vertical direction is dTV1×D V and the interval between adjacent antennas in the fourth antenna group in the horizontal direction is dTH2×D H and the interval between adjacent antennas included in the fourth antenna group in the vertical direction is dTV2×D V and the interval between adjacent antennas included in the first antenna group in the horizontal direction is dRH1×D H and the interval between adjacent antennas included in the first antenna group in the vertical direction is dRV1×D V and the interval between adjacent antennas included in the second antenna group in the horizontal direction is dRH2×D H and the interval between adjacent antennas included in the second antenna group in the vertical direction is dRV2×D V where the D H and the D Vis a value within the range of 0.45 times to 0.8 times the wavelength of the transmission signal, and each of the dTH1, dTV1, dTH2, dTV2, dRH1, dRV1, dRH2, and dRV2 is a value of 1 or more.

[0531] A radar device according to an embodiment of the present disclosure includes a transmission circuit that transmits a transmission signal using a plurality of transmission antennas, and a reception circuit that receives a reflected wave signal obtained by reflecting the transmission signal from an object using a plurality of reception antennas. Either one of the plurality of transmission antennas or the plurality of reception antennas includes a first antenna group arranged in a first direction and a second antenna group arranged in a second direction different from the first direction. The remaining one of the plurality of transmission antennas or the plurality of reception antennas includes a third antenna group arranged in a third direction, where the interval between adjacent antennas is an interval of one wavelength or more of the transmission signal, and a fourth antenna group arranged in a fourth direction different from the third direction, where the interval between adjacent antennas is an interval of one wavelength or more of the transmission signal. The third direction is the same as the first direction, and the fourth direction is the same as the second direction.

Industrial Applicability

[0532] The present disclosure is suitable as a radar device for detecting a wide-angle range.

Explanation of Signs

[0533] 10 Radar device 100 Radar transmission unit 101 Radar transmission signal generation unit 102 Modulation signal generation unit 103 VCO 104 Code generation unit 105 Phase rotation unit 106 Transmission antenna 200 Radar reception unit 201 Antenna system processing unit 202 Reception antenna 203 Reception radio unit 204 Mixer unit 205 LPF 206 Signal processing unit 207 AD conversion unit 208 Beat frequency analysis unit 209 Output switching unit 210 Doppler analysis unit 211 CFAR unit 212 Symbol multiplexing separation unit 213 Direction estimation unit

Claims

1. A transmission circuit that transmits a transmission signal using a plurality of transmission antennas, A reception circuit that receives a reflected wave signal obtained by reflecting the transmission signal from an object using a plurality of reception antennas, Comprising: Either one of the plurality of transmission antennas or the plurality of reception antennas Is divided into a plurality of first antenna groups arranged parallel to each other in a first direction, A plurality of second antenna groups arranged parallel to each other in a second direction different from the first direction, And is divided into, The remaining one of the plurality of transmission antennas or the plurality of reception antennas Is divided into a plurality of third antenna groups arranged parallel to each other in a third direction different from each of the first direction and the second direction, Each of the plurality of first antenna groups has a first interval between adjacent antennas in the first direction, Each of the plurality of second antenna groups has the first interval between adjacent antennas in the second direction, Each of the plurality of third antenna groups has a second interval wider than the first interval between adjacent antennas in the third direction, The first interval is an interval of 0.5 wavelengths or more of the transmission signal, The second interval is an interval of 1 wavelength or more of the transmission signal, A radar device.

2. The radar device is installed in a vehicle, The first direction and the second direction are different directions with respect to a vertical direction which is a height direction of the vehicle, and a horizontal direction which is a straight-ahead direction of the vehicle and a direction orthogonal to the straight-ahead direction of the vehicle, The radar device according to claim 1.

3. The first direction and the second direction are different directions with respect to a vertical direction which is a direction of gravity, and a horizontal direction which is a direction orthogonal to the direction of gravity, The radar device according to claim 1.

4. The third direction is a direction that coincides with the horizontal direction, The radar device according to claim 2 or 3.

5. The minimum interval between the first antenna group and the second antenna group is wider than the aperture length of the third antenna group, The radar device according to claim 1.

6. The first antenna group and the second antenna group include one or more antennas in common, The radar device according to claim 1.

7. The antenna arrangement included in the first antenna group and the antenna arrangement included in the second antenna group are in a line-symmetric relationship with respect to a line perpendicular to the third direction, The radar device according to claim 1.

8. The interval between adjacent antennas of the third antenna group in the horizontal direction is dT×D H where The interval between adjacent antennas included in the first antenna group in the horizontal direction is dRH 1 ×D H and The interval between adjacent antennas included in the first antenna group in the vertical direction is dRV×D V where The interval between adjacent antennas included in the second antenna group in the horizontal direction is dRH 2 ×D H and The interval between adjacent antennas included in the second antenna group in the vertical direction is dRV×D V where Said D H and said D V are values within the range of 0.45 times to 0.8 times the wavelength of said transmission signal, The dT is a value of 2 or more, and the dRH 1 and the dRH 2 each has a value of 1 or more, The radar device according to claim 2 or 3.

9. In each of the third antenna group, the first antenna group, and the second antenna group, the intervals between adjacent antennas are equal. The radar device according to claim 1.

10. In at least one of the third antenna group, the first antenna group, and the second antenna group, the intervals between adjacent antennas include one or more unequal intervals. The radar device according to claim 1.

11. The third antenna group includes a plurality of sets of at least some antennas arranged in the third direction. The radar device according to claim 1.

12. Either one of the plurality of transmitting antennas or the plurality of receiving antennas includes a plurality of the first antenna group and the second antenna group. The radar device according to claim 1.

13. The plurality of transmitting antennas include at least two types of antenna elements having different sizes. The radar device according to claim 1.

14. The radar device is installed in a vehicle. With respect to the vertical direction which is the height direction of the vehicle, and the horizontal direction which is the straight-ahead direction of the vehicle and the direction orthogonal to the straight-ahead direction of the vehicle, All of the plurality of transmitting antennas are arranged at different positions with respect to the horizontal direction. The radar device according to claim 1.

15. The radar device is installed in a vehicle. With respect to the vertical direction which is the height direction of the vehicle, and the horizontal direction which is the straight-ahead direction of the vehicle and the direction orthogonal to the straight-ahead direction of the vehicle, All of the plurality of receiving antennas are arranged at different positions with respect to the horizontal direction. The radar device according to claim 1.

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