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 technology]

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

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

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

[0005] Furthermore, as a radar device, for example, a configuration has been proposed in which multiple antennas (array antennas) are provided on the transmitting side in addition to the receiving side, and beam scanning is performed by signal processing using the transmitting and receiving array antennas (sometimes called a MIMO (Multiple Input Multiple Output) radar) (for example, see Non-Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-081282 [Non-patent literature]

[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., “3D Scanning Millimeter-Wave Radar for Automotive Applications”, 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, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28 , Issue: 1 Publication Year: 1992 , Page(s): 64 - 79 Summary of the Invention [Problem to be solved by the invention]

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

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

[0010] A radar device according to one embodiment of the present disclosure includes a transmitting circuit that transmits a transmission signal using a plurality of transmitting antennas, and a receiving circuit that receives a reflected wave signal of the transmission signal reflected by an object using a plurality of receiving antennas, wherein either the plurality of transmitting antennas or the plurality of receiving 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 transmitting antennas or the plurality of receiving antennas includes a third antenna group arranged in a third direction different from each of the first direction and the second direction, with adjacent antennas spaced apart by a distance of at least one wavelength of the transmission signal.

[0011] In addition, these comprehensive or specific embodiments may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0012] According to an embodiment of the present disclosure, it is possible to improve the angle measurement accuracy or resolution in a radar device.

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

[0014] [Figure 1] Diagram showing an example of MIMO antenna arrangement [Diagram 2] FIG. 13 is a diagram showing an example of a direction estimation result. [Diagram 3] FIG. 1 shows an example of an antenna having a subarray configuration. [Figure 4] FIG. 13 is a diagram showing an example of a direction estimation result. [Diagram 5] FIG. 13 is a diagram showing an example of a direction estimation result. [Figure 6] A block diagram showing a configuration example of a radar device. [Figure 7] FIG. 1 shows an example of a transmission signal and a reflected wave signal when a chirp pulse is used. [Figure 8] FIG. 1 is a diagram showing an example of an arrangement of MIMO antennas according to an arrangement example 1. [Figure 9] FIG. 1 shows an example of the arrangement of a virtual receiving array according to Arrangement Example 1. [Figure 10] FIG. 13 is a diagram showing an example of a direction estimation result according to Arrangement Example 1. [Figure 11] FIG. 1 is a diagram showing an example of an arrangement of MIMO antennas according to a comparative arrangement 1. [Figure 12] FIG. 13 is a diagram showing an example of a direction estimation result according to the comparison arrangement 1. [Figure 13] FIG. 1 shows an example of an arrangement of MIMO antennas according to comparative arrangement 2. [Figure 14] FIG. 13 is a diagram showing an example of a direction estimation result according to a comparison arrangement 2. [Figure 15] FIG. 1 is a diagram showing an example of an arrangement of MIMO antennas according to a first modification of the first arrangement example; [Figure 16] FIG. 1 shows an example of the arrangement of a virtual receiving array according to a first modification of the first arrangement example. [Figure 17] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 1 of Arrangement Example 1. [Figure 18] FIG. 13 is a diagram showing another example of the arrangement of MIMO antennas according to Modification 1 of Arrangement Example 1. [Figure 19] FIG. 13 is a diagram showing another example of the arrangement of the virtual receiving array according to the first modification of the first arrangement example. [Figure 20] FIG. 1 is a diagram showing an example of an arrangement of MIMO antennas according to a first modification of the first arrangement example; [Figure 21] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a second modification of the first arrangement example; [Figure 22]FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a second modification of the first arrangement example. [Figure 23] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a second modification of the first arrangement example. [Figure 24] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 2 of Arrangement Example 1. [Diagram 25] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 2 of Arrangement Example 1. [Figure 26] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a third modification of the first arrangement example. [Figure 27] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a third modification of the first arrangement example. [Figure 28] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 3 of Arrangement Example 1. [Figure 29] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the first arrangement example. [Diagram 30] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the first arrangement example. [Diagram 31] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the first arrangement example. [Diagram 32] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the first arrangement example. [Diagram 33] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a fourth modification of the first arrangement example. [Diagram 34] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a fourth modification of the first arrangement example. [Diagram 35] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a fourth modification of the first arrangement example. [Diagram 36] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a fourth modification of the first arrangement example. [Figure 37] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Figure 38] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Figure 39] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Diagram 40] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Diagram 41]FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fifth modification of the first arrangement example. [Diagram 42] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fifth modification of the first arrangement example. [Diagram 43] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fifth modification of the first arrangement example. [Diagram 44] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fifth modification of the first arrangement example. [Diagram 45] FIG. 5 is a diagram showing an example of the arrangement of a virtual receiving array according to a fifth modification of the first arrangement example. [Figure 46] FIG. 5 is a diagram showing an example of the arrangement of a virtual receiving array according to a fifth modification of the first arrangement example. [Figure 47] FIG. 5 is a diagram showing an example of the arrangement of a virtual receiving array according to a fifth modification of the first arrangement example. [Figure 48] FIG. 5 is a diagram showing an example of the arrangement of a virtual receiving array according to a fifth modification of the first arrangement example. [Figure 49] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 50] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 51] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 52] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 53] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fifth modification of the first arrangement example. [Figure 54] FIG. 5 is a diagram showing an example of the arrangement of a virtual receiving array according to a fifth modification of the first arrangement example. [Figure 55] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 56] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a sixth modification of the first arrangement example. [Figure 57] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a sixth modification of the first arrangement example. [Figure 58] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a sixth modification of the first arrangement example. [Figure 59] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a seventh modification of the first arrangement example. [Figure 60] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a seventh modification of the first arrangement example. [Figure 61] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a seventh modification of the first arrangement example. [Figure 62] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a seventh modification of the first arrangement example. [Figure 63] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a seventh modification of the first arrangement example. [Figure 64] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a seventh modification of the first arrangement example. [Figure 65] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a seventh modification of the first arrangement example. [Figure 66] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to a seventh modification of the first arrangement example. [Figure 67] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 7 of Arrangement Example 1. [Figure 68] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 7 of Arrangement Example 1. [Figure 69] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 7 of Arrangement Example 1. [Figure 70] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 7 of Arrangement Example 1. [Figure 71] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to an eighth modification of the first arrangement example. [Figure 72] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to an eighth modification of the first arrangement example. [Figure 73] FIG. 13 is a diagram showing an example of a direction estimation result according to Modification 8 of Arrangement Example 1. [Figure 74] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 1. [Figure 75] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 1. [Figure 76] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 1. [Figure 77] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 1. [Figure 78]A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 1. [Figure 79] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 1. [Figure 80] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to an arrangement example 2. [Figure 81] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to Arrangement Example 2. [Figure 82] FIG. 13 is a diagram showing an example of a direction estimation result according to Arrangement Example 2. [Figure 83] FIG. 2 is a diagram showing an example of an arrangement of MIMO antennas according to a comparative arrangement 2a and an example of a direction estimation result. [Figure 84] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a comparative arrangement 2b and an example of a direction estimation result. [Figure 85] FIG. 2 shows an example of an arrangement of MIMO antennas according to a comparative arrangement 2c and an example of a direction estimation result. [Figure 86] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a comparative arrangement 2d and an example of a direction estimation result. [Figure 87] FIG. 2 is a diagram showing an example of an arrangement of MIMO antennas according to an arrangement example 2a; [Figure 88] FIG. 2 shows an example of the arrangement of a virtual receiving array according to Arrangement Example 2a. [Figure 89] FIG. 13 is a diagram showing an example of a direction estimation result according to arrangement example 2a. [Figure 90] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to arrangement example 2b. [Figure 91] FIG. 13 is a diagram showing an example of the arrangement of a virtual receiving array according to Arrangement Example 2b. [Figure 92] FIG. 13 is a diagram showing an example of a direction estimation result according to arrangement example 2b. [Figure 93] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the second arrangement example. [Figure 94] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the second arrangement example. [Figure 95] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the second arrangement example. [Figure 96] FIG. 13 is a diagram showing an example of an arrangement of MIMO antennas according to a fourth modification of the second arrangement example. [Figure 97] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 2. [Figure 98] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 2. [Figure 99] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 2. [Figure 100] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 2. [Figure 101] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving arrays under arrangement condition 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A MIMO radar transmits signals (radar transmission waves) multiplexed using, for example, time division, frequency division, or code division from multiple transmission antennas (or called transmission array antennas). Then, for example, the MIMO radar receives signals (radar reflected waves) reflected by surrounding objects using multiple reception antennas (or called reception array antennas), and separates and receives the multiplexed transmission signals from each received signal. Through this processing, the MIMO radar can extract a propagation path response represented 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 MIMO radar, by devising the arrangement of antenna elements in the transmitting and receiving array antennas, it is possible to configure a virtual receiving array antenna (hereinafter referred to as a virtual receiving array, MIMO virtual receiving array, virtual receiving antenna, or virtual receiving array antenna) that is equal to the maximum number of transmitting antenna elements multiplied by the number of receiving antenna elements. This has the effect of increasing the effective aperture length of the array antenna with a small number of elements, thereby improving the angle measurement accuracy or resolution.

[0017] Furthermore, in addition to one-dimensional scanning (angle measurement) in the vertical or horizontal direction, the MIMO radar can also be applied to two-dimensional beam scanning (angle measurement) 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 (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 (horizontal direction in FIG. 1(a)). In FIG. 1(a), the transmitting antennas are arranged at equal intervals (d V ) and the receiving antennas are arranged at equal intervals (d H ) (see, for example, non-patent document 2).

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

[0020] Figures 2(a) and 2(b) show the antenna arrangement of the MIMO radar shown in Figure 1(a) with horizontal element spacing d H = 0.5λ, and the vertical element spacing d V = 0.5λ, where λ is the wavelength of the radar carrier wave.

[0021] As shown in (a) and (b) of FIG. 2, a main beam (main lobe) is formed in the horizontal 0° and vertical 0° directions. Here, the narrower the beam width of the main beam, the better the angle separation performance for multiple targets. For example, in (a) and (b) of FIG. 2, the beam width with a power value of 3 dB is about 26°. Also, as shown in (a) and (b) of FIG. 2, side lobes are generated around the main beam. In a radar device, the side lobes are a cause of false detection as a virtual image. Therefore, the lower the peak level of the side lobe, the lower the probability of false detection as a virtual image in the radar device. In (a) and (b) of FIG. 2, for example, the power ratio (peak side lobe level ratio (PSLR: Peak Sidelobe Level Ratio)) of the side lobe normalized by the peak level of the main beam is about -13 dB (however, when an equal amplitude beam weight is used).

[0022] In order to increase the detection distance of a radar device, it is effective to use an antenna with high gain. For example, the antenna gain can be improved by narrowing the directivity (beam width) of the antenna. The directivity of the antenna becomes narrower, for example, as the aperture surface of the antenna is widened. 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 called an on-board radar), a sub-array antenna configured by arranging multiple antenna elements in the vertical direction may be used to narrow the vertical directivity. By narrowing the vertical directivity using a 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] The vertical direction is the height direction of the vehicle on which the radar device is mounted (or installed), and the horizontal direction is the straight-ahead direction of the vehicle, a direction perpendicular to the straight-ahead direction of the vehicle, or a direction perpendicular to the height direction of the vehicle.

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

[0026] For example, FIG. 3 shows an example of a subarray in which eight planar patch antenna elements are arranged in the vertical direction (vertical direction in FIG. 3) and one element is arranged in the horizontal direction (horizontal direction in FIG. 3). ANT indicates the antenna size in the vertical direction, and W ANT indicates the antenna size in the horizontal direction. Note that the configuration of the subarray is not limited to that shown in Fig. 3, and for example, the number of elements in each of the vertical and horizontal directions may be different from the number shown in Fig. 3.

[0027] Here, when a 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 may be one wavelength or more. Therefore, for example, when a sub-array antenna is used in the vertical direction in the MIMO radar shown in FIG. 1(a) (when the sub-array antenna is arranged in the vertical direction), the vertical element interval d V is expanded to more than one wavelength.

[0028] 4 and 5 show the vertical element spacing d V The following shows an example of a Fourier beam pattern oriented in the horizontal 0° and vertical 0° directions when is set to one wavelength (λ) or more. Note that in Figures 4 and 5, the directivity of each antenna element sub-arrayed in the vertical direction is not taken into consideration.

[0029] In Fig. 4, the vertical element spacing d v = λ, horizontal element spacing d H = 0.5λ, and in Fig. 5, the vertical element spacing d V = 2λ, horizontal element spacing d H = 0.5λ.

[0030] As shown in Figures 4 and 5, the main beam (main lobe) is directed in the horizontal 0° and vertical 0° directions, and a high-level side lobe (e.g., grating lobe) is generated in the vertical direction around the main beam, compared to the side lobes in Figures 2(a) and 2(b). In Figures 4 and 5, the ratio of the peak level of the grating lobe to the peak level of the main lobe (peak-to-side lobe ratio) is 0 dB. Also, in Figure 5(d), V = 2λ), Fig. 4(d V = λ), the angular interval where high-level side lobes (e.g., grating lobes) occur in the vertical direction is narrower. In other words, the vertical element spacing d V It can be seen that the wider the angle, the narrower the angular interval at which side lobes (e.g., grating lobes) occur.

[0031] In this way, the larger the antenna size in the vertical direction of a radar device, the wider the element spacing in the vertical direction becomes, and therefore, grating lobes are more likely to occur at angles relatively close to the main beam. Therefore, if the detection angle range assumed by the radar device is wider than the angle at which grating lobes occur, the radar device is more likely to erroneously detect false peaks caused by grating lobes as targets within the detection angle range, and the detection performance of the radar device may deteriorate.

[0032] Furthermore, even if a grating lobe is outside the detection angle range assumed by a radar device, if the power of the reflected wave arriving from the grating lobe direction is sufficiently large, the radar device may easily 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 spacing is one wavelength or more, grating lobes always occur within a range of ±90 degrees, so even a radar device with a narrow viewing angle is likely to experience deterioration in radar detection performance due to erroneous detection caused by grating lobes.

[0033] On the other hand, for example, the wider the vertical element spacing, the narrower the vertical beam width, and the more the radar device can improve its vertical angle measurement accuracy or angular resolution. For example, comparing the vertical element spacings in Figures 2, 4, and 5, they are 0.5λ, λ, and 2λ, respectively, and comparing the main lobes in the Fourier beam patterns, it can be seen that the wider the vertical element spacing, the narrower the vertical beam width, and a sharper beam is formed. In this way, the narrower the vertical beam width, the more the radar device can improve its vertical angle measurement accuracy or angular resolution.

[0034] Similarly, for example, the wider the horizontal element spacing, the narrower the horizontal beam width, and the more the radar device can improve its horizontal angle measurement accuracy or angular resolution. On the other hand, the wider the horizontal element spacing, the more likely it is that grating lobes will occur. For example, if the detection angle range assumed by the radar device is wider than the angle at which grating lobes occur, the radar device will be more likely to erroneously detect false peaks caused by grating lobes as targets within the detection angle range, and the detection performance of the radar device may deteriorate.

[0035] In view of this, 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, it is possible to improve the angle measurement accuracy or resolution with a smaller number of antennas.

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

[0037] Furthermore, 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 a traffic light, etc. Such a radar device can be used as a sensor in an assistance system for improving the safety of passing vehicles or pedestrians, for example.

[0038] The uses of the radar device are not limited to these, and the device may be used for other purposes.

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

[0040] Below, a radar device having a configuration in which a transmission branch transmits different code division multiplexed transmission signals from multiple 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 a transmission branch transmits different frequency division multiplexed transmission signals from multiple transmission antennas, and a reception branch separates each transmission signal and performs reception processing. Similarly, a radar device may have a configuration in which a transmission branch transmits time division multiplexed transmission signals from multiple transmission antennas, and a reception branch performs reception processing.

[0041] Similarly, a configuration may be adopted in which a transmitting branch transmits different transmit signals that have been Doppler division multiplexed from multiple transmitting antennas, and a receiving branch separates each transmit signal and performs receive processing.Similarly, a transmitting branch may transmit transmit signals that have been multiplexed by combining at least two of code division multiplexing, time division multiplexing, and Doppler division multiplexing from multiple transmitting antennas, and a receiving branch separates each transmit signal and performs receive processing.

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

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

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

[0045] The radar transmitter 100 generates a radar signal (radar transmission signal) and transmits the signal to a plurality of transmitting antennas 106 (e.g., N tx The radar transmit signal is transmitted at a specified transmission period using a transmitting array antenna consisting of three antennas.

[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 receiving array antenna including a plurality of (e.g., Na) receiving antennas 202. The radar receiver 200 processes the reflected wave signal received by each receiving antenna 202, and, for example, detects the presence or absence of a target or estimates the arrival distance, Doppler frequency (in other words, relative speed), and arrival direction of the reflected wave signal, and outputs information related to the estimation result (in other words, positioning information).

[0047] The target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including four-wheeled and two-wheeled vehicles), a person, a block, or a curb.

[0048] [Configuration of radar transmitter 100] The radar transmitter 100 includes a radar transmission signal generator 101, a code generator 104, a phase rotator 105, and a transmitting antenna .

[0049] The radar transmission signal generating unit 101 generates a radar transmission signal. The radar transmission signal generating unit 101 includes, for example, a modulation signal generating unit 102 and a VCO (Voltage Controlled Oscillator) 103. Each component of the radar transmission signal generating unit 101 will be described below.

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

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

[0052] The code generation unit 104 generates a different code for each transmitting antenna 106 that performs code multiplexing transmission. The code generation unit 104 outputs the amount of phase rotation corresponding to the generated code to the phase rotation unit 105. The code generation unit 104 also outputs information related to the generated code to the radar receiving unit 200 (output switching unit 209 described later).

[0053] The phase rotation unit 105 imparts the amount of phase rotation 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 from 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 given a phase rotation amount corresponding to the code, and is then code-multiplexed and transmitted from the multiple transmission antennas 106.

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

[0055] The code generator 104 generates, for example, a different code for each transmitting antenna 106 that performs code multiplexing transmission.

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

[0057] The code generation unit 104 generates N allcode (hereinafter, N allcode Of the N orthogonal codes (sometimes called Loc), CM These orthogonal codes are set as codes for code multiplexing transmission.

[0058] For example, the number of code multiplexes N CM is the number of orthogonal codes N allcode The following, N CM ≦N allcode For example, the code length Loc of N CM Let Code ncm =[OC ncm (1), O.C. ncm (2),…, O.C. ncm (Loc)]. Here, "OC ncm (noc)" is the ncm-th orthogonal code ncm In addition, "ncm" represents the index of the orthogonal code used for code multiplexing, ncm=1,...,N CM In addition, “noc” is the index of the code element, noc=1,…,Loc.

[0059] As described above, N generated by the code generator 104 CMThe orthogonal codes are, for example, codes that are orthogonal to each other (in other words, codes that are uncorrelated). For example, a Walsh-Hadamard code 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 code of a code length of 2, 4, 8, or 16 includes 2, 4, 8, or 16 orthogonal codes, respectively.

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

number

[0061] Here, ceil[x] is an operator (ceil function) that outputs the smallest integer equal to or greater than the real number x. In the case of a Walsh-Hadamard code with a code length of Loc, N allcode For example, Walsh-Hadamard codes with code lengths Loc=2, 4, 8, and 16 contain 2, 4, 8, and 16 orthogonal codes, respectively, so N allcode (2)=2, N allcode (4)=4, N allcode (8)=8 and N allcode (16)=16. The code generator 104 generates N allcode Of the (Loc) codes, N CM orthogonal codes are used.

[0062] Below, each code multiplex number N CM An example of an orthogonal code in the above will be described.

[0063] For example, the number of code multiplexes N CM In the case where Loc=3, the code generation unit 104 determines, for example, three orthogonal codes from among the Walsh-Hadamard codes with a code length Loc=4 as codes for code multiplexing 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 generates N CM N orthogonal codes may be selected as codes for code multiplexing. In this case, N CM ≦Loc=N allcode (Loc).

number

[0065] The elements constituting the orthogonal code sequence are not limited to real numbers, but may include complex values.

[0066] The codes may also be other orthogonal codes different from Walsh-Hadamard codes, for example, the codes may be orthogonal M-sequence codes or pseudo-orthogonal codes.

[0067] Above, each code multiplex number N CM An example of orthogonal codes in the above has been described.

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

[0069] The radar device 10 performs code-multiplexing transmission using different orthogonal codes for the transmitting antennas Tx#1 to Tx#Nt that perform code-multiplexing transmission. Therefore, the code generating unit 104 generates an orthogonal code Code ncm The phase rotation amount ψ based on ncm (m) is set and output to the phase rotation unit 105. Here, ncm=1,...,N CM It is.

[0070] For example, the phase rotation amount ψ ncm As shown in the following equation (3), (m) is an orthogonal code Code ncm Each of the Loc code elements OC ncm (1),…, O.C. ncm A phase amount equivalent to (Loc) is cyclically assigned.

number

[0071] Here, angle(x) is an operator that outputs the radian phase of real number x, and 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 sequence Code ncm and varies cyclically within the range of 1 to Loc for each transmission period (Tr) as shown in the following equation (4).

number

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

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

[0074] The phase rotation unit 105 is, for example, N txThe phase rotation unit 105 includes a phase shifter or a phase modulator corresponding to each of the transmitting antennas 106. The phase rotation unit 105 rotates the phase of the chirp signal input from the radar transmission signal generation unit 101 by an amount of phase rotation ψ ncm (m) is assigned to each.

[0075] For example, the phase rotation unit 105 assigns an orthogonal code Code ncm The phase rotation amount ψ based on ncm (m) is added, where ncm=1,…,N CM where m=1,..,Nc.

[0076] N tx The output from the phase rotation unit 105 for the transmitting antennas 106 is, for example, amplified to a predetermined transmission power and then tx The signal is radiated into space from transmitting antennas 106 (for example, transmitting array antennas).

[0077] As an example, the number of transmitting antennas N Tx = 3, and the number of code multiplexes N CM Here, we will explain the case where code multiplexing is performed at Nt=3. CM is not limited to these values.

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

[0079] The first (ncm=1) phase rotation unit 105 (in other words, the phase shifter corresponding to the first transmitting antenna 106 (e.g., Tx#1)) applies phase rotation to the chirp signal generated in the radar transmission signal generation unit 101 for each transmission period Tr, as shown in the following equation (5). The output of the first phase rotation unit 105 is transmitted from the transmitting antenna Tx#1. Here, cp(t) represents the chirp signal for the mth transmission period Tr.

number

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

number

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

number

[0082] When radar positioning is performed continuously, the radar device 10 generates the orthogonal code Code ncm The code used may be set variably.

[0083] An example configuration of the radar transmitter 100 has been described above.

[0084] [Configuration of radar receiver 200] 6, the radar receiver 200 includes Na receiving antennas 202 (e.g., Rx#1 to Rx#Na) forming an array antenna. The radar receiver 200 also includes Na antenna system processors 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a code multiplexing / demultiplexing unit 212, and a direction estimator 213.

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

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

[0087] The receiving radio unit 203 has 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, which is a transmission signal, input from the radar transmission signal generation unit 101. The LPF 205 performs LPF processing on the output signal of the mixer unit 204, to output a beat signal having a frequency corresponding to the delay time of the reflected wave signal. For example, as shown in the lower part of Fig. 7, the difference frequency between the frequency of the transmitted chirp signal (transmitted frequency modulated wave) and the frequency of the received chirp signal (received frequency modulated wave) is obtained as the beat frequency.

[0088] The signal processing unit 206 of each antenna system processing unit 201-z (where z=any of 1 to Na) has 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 (eg, beat signal) output from the LPF 205 is converted by the AD conversion unit 207 in the signal processing unit 206 into discrete sample data that has been discretely sampled.

[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 of the chirp signal, and C0 represents the speed of light.

[0094] 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 based on the orthogonal code element index OC_INDEX output from the code generation unit 104. 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 has 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 receives data (for example, beat frequency response RFT output from the beat frequency analysis unit 208) for Ncode transmission periods out of the Nc transmission periods. z (f b , m) to obtain the distance index f b Doppler analysis is performed every 100 ms, where noc is the code element index, noc=1, …, Loc.

[0096] For example, if 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 aliasing does not occur, which is derived from the sampling theorem, is ±1 / (2Loc×Tr). Also, the Doppler frequency index f s The Doppler frequency interval of is 1 / (Ncode×Loc×Tr), and the Doppler frequency index f s The range of f s = -Ncode / 2, …, 0, …, Ncode / 2-1.

[0097] For example, the output VFT of the Doppler analysis unit 210 of the zth signal processing unit 206 z noc (f b , f s ) is expressed by the following formula (9), where j is the imaginary unit and z=1 to Na.

number

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

number

[0099] where noc is the index of the code element, noc=1,…,Loc, and the FFT size is N codewzero The maximum Doppler frequency at which aliasing does not occur, derived from the sampling theorem, is ±1 / (2Loc×Tr). Also, the Doppler frequency index f s The Doppler frequency interval is 1 / (N codewzero × Loc × Tr), and the Doppler frequency index f s The range of f s =-N codewzero / 2,…,0,…, N codewzero / 2-1.

[0100] In the following, as an example, a case where Ncode is a power of 2 will be described. Note that, when zero padding is used in the Doppler analysis unit 210, Ncode is set to N in the following description. codewzerocan be similarly applied and the same effect can be obtained by replacing

[0101] Furthermore, the Doppler analysis unit 210 may multiply the signal by a window function coefficient such as a Han window or a Hamming window during the FFT process. By applying the window function, the radar device 10 can suppress side lobes that occur around the beat frequency peak.

[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 analyzers 210 of each of the first to Na-th signal processors 206, and calculates the distance index f b_cfar and the Doppler frequency index f s_cfar Extract.

[0104] The CFAR unit 211 calculates the output VFT of the Doppler analyzer 210 of the first to Na-th signal processors 206 as shown in the following equation (11), for example. z noc (f b , f s ) are power-added, and two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity) or CFAR processing combining one-dimensional CFAR processing is performed. For the two-dimensional CFAR processing or the CFAR processing combining one-dimensional CFAR processing, the processing disclosed in Non-Patent Document 3, for example, may be applied.

number

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

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

[0107] The code demultiplexing unit 212 extracts, for example, the distance index f b_cfar and the Doppler frequency index f s_cfar Based on this, the code-multiplexed signal is demultiplexed.

[0108] For example, the code demultiplexing unit 212 calculates the distance index f extracted in the CFAR unit 211 as shown in the following equation (12). b_cfar and the Doppler frequency index f s_cfar The Doppler component VFTALL, which is the output of the Doppler analysis unit 210, corresponds to z (f b_cfar , f s_cfar ) is subjected to code separation processing.

number

[0109] Here, DeMul z ncm (f b_cfar , f s_cfar ) is the distance index f of the Doppler analyzer 210 in the z-th antenna system processor 201. b_cfar and the Doppler frequency index f s_cfar Orthogonal code for the output of ncm The output (e.g., the code separation result) of the code-multiplexed signal is decoded using z=1,…,Na, and ncm=1,…,N CM It is. Furthermore, in formula (12),

number

number

number

[0110] In equation (12), α(f s_cfar ) represents the "Doppler phase correction vector". The Doppler phase correction vector α(f s_cfar ) is, for example, the Doppler frequency index f extracted in the CFAR unit 211. s_cfar is the output range of the Doppler analyzer 210 not including Doppler aliasing (in other words, the Doppler range), the Doppler phase rotation caused by the time difference in Doppler analysis among the Loc Doppler analyzers 210 is corrected.

[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 ) is, for example, the output VFT of the first Doppler analysis unit 210 z 1 (f b_cfar , f s_cfar ) based on the Doppler analysis time, the output VFT of the second Doppler analysis unit 210 z 2 (f b_cfar , f s_cfar ) to the output VFT of the Doppler analysis unit 210 at Loc z Loc (f b_cfar , f s_cfar The Doppler frequency index f s_cfar is a vector whose elements are Doppler phase correction coefficients for correcting the phase rotation in the Doppler component of

number

[0112] In addition, in equation (12), VFTALL z (f b_cfar , f s_cfar ) is, for example, as shown in the following equation (15), the output VFT of the Loc Doppler analyzers 210 in the z-th antenna system processor 201. z noc (f b , f s ), the distance index f extracted by the CFAR unit 211 b_cfar and the Doppler frequency index f s_cfar The corresponding component VFT z noc (f b_cfar , f s_cfar ) (where noc=1,…,Loc) is expressed in vector form.

number

[0113] The above describes an example of the operation of the code demultiplexing unit 212. In the configuration shown in Fig. 6, the maximum Doppler frequency at which aliasing does not occur, which is derived from the sampling theorem, is ±1 / (2Loc×Tr), and the operation of the code demultiplexing unit 212 has been described on the assumption that the target detected by the radar device 10 is within this range.

[0114] The configuration of the radar device 10 is not limited to that shown in Fig. 6, and the detectable Doppler frequency range can be expanded. For example, a folding determination unit that determines whether the output of the Doppler analysis unit disclosed in Fig. 1 of Patent Document 1 contains a Doppler frequency component exceeding the maximum Doppler frequency ±1 / (2Loc×Tr) may be provided to perform folding determination processing, and the code demultiplexing unit may perform code demultiplexing using the determination result.

[0115] However, in order to perform the aliasing determination process in the aliasing 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 is CM is the number of orthogonal codes N allcode Less than N CM <N allcode In other words, the code length Loc of the orthogonal code is CM Make it larger than.

[0116] By using such a configuration, the detectable Doppler range can be expanded, for example, the maximum detectable Doppler frequency can be set to ±1 / (2×Tr). Therefore, it becomes possible to operate the code multiplexing / demultiplexing unit assuming that the target detected by the radar device is within the Doppler frequency range of ±1 / (2×Tr).

[0117] The radar device 10 may adopt an arrangement of the transmitting antenna 106 and the receiving antenna 202 that can suppress grating lobes or side lobes and increase angular resolution by, for example, improving the array gain and increasing the aperture length using a virtual receiving array.

[0118] Hereinafter, examples of antenna arrangements of the transmitting antenna 106 and the receiving antenna 202 and examples of direction estimation processing in the direction estimator 213 when each example of the antenna arrangement is applied will be described.

[0119] Furthermore, in the following arrangement examples and modifications, the arrangement of the transmitting antenna 106 may be replaced with the antenna arrangement of the receiving antenna 202, and the arrangement of the receiving antenna 202 may be replaced with the arrangement of the transmitting antenna 106. In the radar device 10, even if the antenna arrangements of the transmitting antenna 106 and the receiving antenna 202 are swapped, the same effects as those of the following arrangement examples can be obtained.

[0120] In addition, the horizontal and vertical directions in the following arrangement examples and modified examples may be interchanged. When the horizontal and vertical directions are interchanged in the antenna arrangement, the radar device 10 can obtain the effect of interchange of the horizontal and vertical directions in the following arrangement examples.

[0121] In addition, the horizontal direction and the vertical direction in the layout example do not have to be strictly horizontal and vertical, and the entire layout example may be arranged at a predetermined angle while maintaining the relative positional relationship between the transmitting antenna and the receiving antenna included in the layout example. Even in this case, the relative positional relationship between the transmitting antenna and the receiving antenna included in the layout example is maintained, so 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] [Placement condition 1] N Tx The 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. Tx Some of the transmitting antennas 106 may be spaced apart from one another. Tx 106. The system may include transmit antennas other than transmit antenna 106.

[0124] The Na receiving antennas 202 include a "first diagonal antenna group" arranged in a "first diagonal direction" and a "second diagonal antenna group" arranged in a "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. The radar device 10 may include receiving antennas other than the Na receiving antennas 202. Also, some of the Na receiving antennas 202 may be arranged at different intervals.

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

[0126] Furthermore, each of the first oblique direction and the second oblique direction may be a direction that does not coincide with a predetermined arrangement direction of the transmitting antenna 106. In other words, a first oblique direction (e.g., corresponding to a first direction) in which a first oblique antenna group (e.g., corresponding to a first antenna group) is arranged, a second oblique direction (e.g., corresponding to a second direction) in which a second oblique antenna group (e.g., corresponding to a second antenna group) is arranged, and a plurality of (e.g., N Tx The directions in which the second (number of) transmitting antennas 106 are arranged (for example, corresponding to a third direction) may be different from each other.

[0127] Grating lobes can be suppressed by arranging the first diagonal antenna group and the second diagonal antenna group that satisfy the arrangement condition 1 at any position. For example, as shown in the following arrangement example or modification, antenna elements with a large vertical size can be arranged by arranging the first diagonal antenna group and the second diagonal antenna group so that their horizontal positions do not overlap each other.

[0128] The following describes an example of placement condition 1. The following describes a placement example that satisfies placement condition 1, and an example of a direction estimation result by computer simulation in that placement example.

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

[0130] <Layout example 1> 8 is a diagram showing an example of an arrangement (for example, an example of a MIMO antenna arrangement) of the transmitting antenna 106 (for example, represented as Tx) and the receiving antenna 202 (for example, represented as Rx) according to the arrangement condition 1. In FIG. 8, the scales of the horizontal and vertical axes are, for example, a basic interval D in the horizontal direction. H , and the basic vertical spacing D VThe scales of the horizontal and vertical axes are the same for the MIMO antenna arrangements in the following other examples. H and D. V may be spaced at intervals of 0.5 wavelengths.

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

[0132] In FIG. 8, N Tx The six transmitting antennas Tx#1 to #6 are arranged at equal intervals of 1.5 wavelengths in the horizontal direction (for example, in a predetermined arrangement direction). In other words, in the arrangement example 1, a plurality of (for example, N Tx All of the transmitting antennas 106 (number of transmitting antennas 106) may be arranged in a predetermined direction (e.g., corresponding to a third direction). In addition, in Arrangement Example 1, for example, the interval between adjacent transmitting antennas of the multiple transmitting antennas 106 may be equal to or greater than one wavelength of the radar transmission signal.

[0133] In addition, in Fig. 8, Na=8 receiving antennas Rx#1-#8 include a first diagonal antenna group Rx#1-#4 arranged in a first diagonal direction and a second diagonal antenna group Rx#5-#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, and satisfy the arrangement condition 1. Also, as shown in Fig. 8, the first diagonal direction, the second diagonal direction, and the arrangement direction of the transmitting antenna 106 (for example, the horizontal direction) are not parallel but different from each other. Also, for example, as shown in Fig. 8, the first diagonal direction and the second diagonal direction are different directions from the vertical direction and the horizontal direction.

[0134] For example, the first diagonal antenna group Rx#1-#4 shown in Fig. 8 are shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths, and are also shifted downwards in the vertical direction at intervals of 0.5 wavelengths. The second diagonal antenna group Rx#5-#8 shown in Fig. 8 are shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths, and are also shifted downwards in the vertical direction at intervals of 0.5 wavelengths.

[0135] 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-symmetric 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 group Rx#1-#4 and the second diagonal antenna group Rx#5-#8 are arranged in a horizontally inverted symmetrical manner (also called left-right inverted symmetrical manner or mirror symmetrical manner).

[0136] In FIG. 8, adjacent antennas in each of the multiple transmitting antennas Tx#1 to #6, the first diagonal antenna group Rx#1 to #4, and the second diagonal antenna group Rx#5 to #8 are spaced equally apart.

[0137] Fig. 9 is a diagram showing an example of the arrangement of a virtual receiving array obtained by the antenna arrangement shown in Fig. 8. In Fig. 9, the scales of the horizontal and vertical axes are, for example, a basic interval D H , and the basic vertical spacing D V The scales of the horizontal and vertical axes are the same for the virtual receiving array arrangements in the other examples described below.

[0138] Here, the arrangement of the virtual receiving array may be expressed, for example, as in equation (16) below, based on the position (e.g., the position of the feed point) of transmitting antenna 106 constituting the transmitting array antenna and the position (e.g., the position of the feed point) of receiving antenna 202 constituting the receiving array antenna.

number

[0139] Here, the position coordinates of a transmitting antenna 106 (for example, Tx#n) constituting the transmitting array antenna are expressed as (X T_#n ,Y T_#n ) (e.g., n=1,.., N Tx ), and the position coordinates of the receiving antenna 202 (for example, Rx#m) constituting the receiving array antenna are represented as (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 expressed as (X V_#k ,Y V_#k ) (e.g., k=1,.., N Tx ×Na).

[0140] In addition, in equation (16), for example, VA#1 is expressed as the position reference (0,0) of the virtual receiving array.

[0141] For example, from the arrangement of transmitting antennas Tx#1 to Tx#6 and the arrangement of receiving antennas Rx#1 to Rx#8 as shown in FIG. 8, the position coordinates of virtual antennas VA#1 to #48 constituting a virtual receiving array antenna are calculated from equation (16). As an example, the position coordinates of virtual antennas VA#1 to #16 are calculated as follows: (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 )=(15 D 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 )

[0142] 9, VA#16 and VA#44 are arranged overlapping at the same position, and VA#8 and VA#36 are arranged overlapping at the same position.

[0143] Here, in the case of Figs. 8 and 9, D H and D. V In the following description, a case will be described in which 0.5λ is set for each of D and D1, but they may be set to values ​​of approximately 0.45λ to 0.8λ (for example, any value within a range of 0.5 to 0.8 times the wavelength of the radar transmission signal). H and D. V may be set according to the horizontal or vertical viewing angle of the radar device 10. For example, when the horizontal or vertical viewing angle is a wide viewing angle in the range of about ±70 degrees to ±90 degrees, D H Or D VAlternatively, when the horizontal or vertical viewing angle is a narrow viewing angle in the range of about ±20 degrees to ±40 degrees, D H Or D V may be set to a wider interval, for example, about 0.7λ. H and D. V The setting of is the same for the subsequent 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-mentioned antenna arrangement is applied will be described.

[0145] In FIG. 1, the direction estimation unit 213 receives a distance index f b_cfar and the Doppler frequency index f s_cfar The code separation result DeMul for the output of the Doppler analyzer 210 corresponding to z ncm (f b_cfar , f s_cfar ) to estimate the direction of the target.

[0146] For example, the direction estimator 213 calculates the virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is generated and direction estimation processing is performed.

[0147] Virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is the number of transmitting antennas N Tx and the number of receiving antennas Na, Tx ×Na elements. The virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is used for processing to estimate the direction of the reflected wave signal from the target based on the phase difference between the receiving antennas 202. Here, z=1,...,Na.

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

number

[0149] Next, the direction estimator 213 calculates, for example, a virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is used to perform horizontal and vertical direction estimation processing.

[0150] For example, the direction estimator 213 calculates a virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is used to correct the phase and amplitude deviations between the transmitting and receiving array antennas. [y] The virtual receiving array correlation vector h with the deviation between antennas corrected is obtained by multiplying _after_cal (f b_cfar , f s_cfar ), and the direction estimation unit 213 performs processing for estimating the horizontal and vertical directions based on the phase difference between the receiving antennas of the arriving reflected wave. Here, y=1,..,(N Tx ×Na).

number

number

[0151] CA includes an array correction coefficient that corrects the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas, and a coefficient that reduces the effect of inter-element coupling between the antennas (N Tx When the coupling between the antennas of the virtual receiving array can be ignored, CA becomes a diagonal matrix, and the diagonal elements are the array correction values ​​h_cal that correct the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas. [y] Includes:

[0152] Virtual receiving array correlation vector h with correction for deviation between antennas _after_cal (f b_cfar , f s_cfar ) is N Tx ×Na elements. In the following, each element is represented as follows and used to explain the direction estimation process. Each element is a complex value, and represents the amplitude component and phase component received by each virtual receiving antenna.

number

[0153] The direction estimation unit 213 calculates the virtual receiving array correlation vector h _after_cal (f b_cfar , f s_cfar In estimating the horizontal and vertical directions, the direction estimator 213 estimates the direction of arrival estimation evaluation function value P(θ, Φ, f b_cfar , f s_cfar ) is varied within a specified angle range to calculate a spatial profile. The direction estimation unit 213 extracts a predetermined number of maximum peak directions in the calculated spatial profile in descending order, and outputs the azimuth direction and elevation angle direction of each maximum peak as an arrival direction estimate (e.g., positioning output).

[0154] The arrival direction estimation evaluation function value P(θ, Φ, f b_cfar , f s_cfar There are various methods for estimating the direction of arrival (DOA) depending on the algorithm. 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.

number

[0156] Here, the azimuth direction θ u is a vector obtained by varying the azimuth range θmin to θmax for which the direction of arrival estimation is performed at azimuth intervals 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 maximum integer value that does not exceed the real number x.

[0157] In addition, the elevation angle Φ v is a vector obtained by varying the azimuth range Φmin to Φmax for which the direction of arrival estimation is performed at azimuth intervals β2. For example, Φ v is set as follows: Φ v =Φmin + vβ2, v=0,…, NV NV=floor[(Φmax-Φmin) / β2]

[0158] In this embodiment, the radar device 10 has, for example, virtual receiving array arrangements VA#1, . . . , VA#(N Tx ×Na) based on the direction vector a(θ u ,Φ v ) may be calculated in advance. Here, the direction vector a(θ u,Φ v ) is the complex response of a virtual receiving array antenna when radar reflections arrive from the azimuth direction θ and the elevation angle direction Φ (N Tx ×Na) order column vector. The complex response a(θ u ,Φ v ) represents the phase difference calculated geometrically at the element spacing between the antennas.

[0159] In this case, as an example, the direction of the normal to the front of the antenna plane shown in Arrangement Example 1 is taken as the reference (azimuth θ=0 degrees, elevation angle Φ=0 degrees).

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

[0161] Figure 10 shows the MIMO array layout for layout example 1 (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation unit 213. As an example, Fig. 10 plots the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically. Here, the results are shown for a case where each transmitting antenna and receiving antenna is non-directional, and the direction estimation results (computer simulation results) in the other examples below also show results for a case where each antenna is non-directional.

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

[0163] In arrangement example 1 shown in Fig. 8, the transmitting antennas 106 are arranged at intervals of 1.5 wavelengths (1.5λ) in the horizontal direction, the receiving antennas 202 are arranged at intervals of 6 wavelengths or more in the horizontal direction, and the virtual antennas in the virtual receiving array arrangement shown in Fig. 9 are arranged at intervals of 1 wavelength or more in the horizontal direction, which is an antenna interval at which grating lobes may occur. For example, when the target direction is 0 degrees in the horizontal direction, grating lobes may occur at -41.8 degrees and 41.8 degrees in the horizontal direction.

[0164] In addition, in Arrangement Example 1, even if the receiving antennas 202 are arranged at intervals of, for example, 6.5 wavelengths or more in the horizontal direction and the virtual antennas in the virtual receiving array arrangement are arranged at intervals of one wavelength or more in the horizontal direction, grating lobes can be suppressed. For example, as shown in Fig. 10, it can be seen that 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 an antenna arrangement (hereinafter referred to as "comparative arrangement 1") in which the first oblique antenna group Rx#1-#4 of the receiving antennas 202 in arrangement example 1 shown in Fig. 8 is used, for comparison with arrangement example 1. Fig. 12 shows a direction estimation result using the beamformer method in the case where comparative arrangement 1 is applied. In Fig. 12, as in Fig. 10, the output of the direction-of-arrival estimation evaluation function value is plotted in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0167] As in comparative arrangement 1, the virtual receiving array arrangement when the first diagonal antenna group Rx#1 to #4 of the receiving antennas 202 in arrangement example 1 is used corresponds to VA#1 to #4, #9 to #12, #17 to #20, #25 to #28, #33 to #36, and #41 to #44 in FIG. 9.

[0168] Similarly, Fig. 13 shows an antenna arrangement in which the second oblique antenna group Rx#5-#8 of the receiving antennas 202 in Arrangement Example 1 shown in Fig. 8 are used (hereinafter referred to as "Comparative Arrangement 2") for comparison with Arrangement Example 1. Fig. 14 shows a direction estimation result using the beamformer method in the case where Comparative Arrangement 2 is applied. In Fig. 14, as in Fig. 10, the output of the direction-of-arrival estimation evaluation function value is plotted in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0169] As in comparative arrangement 2, the virtual receiving array arrangement when the second diagonal antenna group Rx#5 to #8 of the receiving antennas 202 in arrangement example 1 is used corresponds to VA#5 to #8, #13 to #16, #21 to #24, #29 to #32, #37 to #40, and #45 to #48 in FIG. 9.

[0170] For example, as in comparative arrangement 1 shown in FIG. 11, when the first oblique antenna group Rx#1-#4 of the receiving antenna 202 of arrangement example 1 shown in FIG. 8 is used, 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) in the direction estimation results (for example, (a) and (b) in FIG. 12) using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213 for the target true value (for example, 0 degrees horizontal, 0 degrees vertical).

[0171] Furthermore, for example, when the second oblique antenna group Rx #5 to #8 of the receiving antenna 202 of Arrangement Example 1 shown in FIG. 8 is used as in Comparative Arrangement 2 shown in FIG. 13, grating lobes occur in two directions (−41.8 degrees horizontally, +41.8 degrees vertically) and (+41.8 degrees horizontally, −41.8 degrees vertically) in the direction estimation results (for example, (a) and (b) in FIG. 14) using the beamformer method as the arrival direction estimation algorithm of the direction estimation unit 213 relative to the target true value (for example, 0 degrees horizontally, 0 degrees vertically).

[0172] Here, the arrangement direction of receiving antennas Rx#1 to #4 (e.g., corresponding to the first diagonal antenna group) in comparative arrangement 1 shown in Fig. 11 is different and not parallel to the arrangement direction of receiving antennas Rx#5 to #8 (e.g., corresponding to the second diagonal antenna group) in comparative arrangement 2 shown in Fig. 13. Therefore, as shown in Figs. 12 and 14, comparative arrangements 1 and 2 have the property that the horizontal and vertical two-dimensional angular directions in which grating lobes occur do not match and are shifted.

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

[0174] Therefore, in Arrangement Example 1 including the first and second diagonal antennas, the directions (two-dimensional angular directions) of the grating lobes generated in Comparison Arrangement 1 including the first diagonal antenna group and the grating lobes generated in Comparison Arrangement 2 including the second diagonal antenna group do not match and tend to be dispersed, as shown in Fig. 8. For this reason, in Arrangement Example 1, the peak level in the grating lobe direction tends to be suppressed compared to the peak in the target true value direction, as shown in Fig. 10(a) and (b).

[0175] For example, when the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inverted and symmetrical as shown in Fig. 8, the virtual receiving array arrangements corresponding to each of comparison arrangements 1 and 2 are horizontally inverted and symmetrical. As a result, in each of comparison arrangements 1 and 2, the horizontal and vertical two-dimensional directions in which grating lobes occur are horizontally inverted and symmetrical, and it can be seen that the deviation in the horizontal and vertical two-dimensional angular directions in which grating lobes occur becomes larger, as shown in Figs.

[0176] Therefore, in arrangement example 1, for example, when the arrangement directions (e.g., diagonal directions) of the first diagonal antenna group and the second diagonal antenna group are horizontally inverted and symmetrical as shown in FIG. 8, the directions in which grating lobes occur are horizontally inverted and symmetrical as shown in FIG. 10, and the interval (or deviation) between the directions of suppressed grating lobes is likely to become larger.

[0177] Such an arrangement in which the directions of the first oblique antenna group and the second oblique antenna group are horizontally inverted and symmetrical is more suitable, for example, when the number of antennas of the radar device 10 is smaller. For example, the fewer the number of antennas of the radar device 10, the wider the beam width of the main beam in direction estimation tends to be. For this reason, when the directions of grating lobes to be suppressed are close to each other, the fewer the number of antennas of the radar device 10, the wider the beam width is, and the more likely the grating lobe power is to overlap and increase in the grating lobe power. For this reason, the fewer the number of antennas of the radar device 10, the more the grating lobe suppression performance is degraded, and the more likely the probability of false detection in the radar device 10 is to increase. Therefore, when the number of antennas of the radar device 10 is small, for example, an arrangement in which the directions of the first oblique antenna group and the second oblique antenna group are horizontally inverted and symmetrical can suppress the overlap of grating lobe power, thereby improving the grating lobe suppression performance.

[0178] Also, as shown in Fig. 8, in Arrangement Example 1, the transmitting antennas 106 are arranged in a row in the horizontal direction, and the receiving antennas 202 are arranged in a row in the diagonal direction. In other words, as shown in Fig. 8, in Arrangement Example 1, the antenna elements of both the transmitting antennas 106 and the receiving antennas 202 do not overlap in the vertical direction. Therefore, in Arrangement Example 1, it is possible to arrange antenna elements with a larger size in the vertical direction (for example, a size of one wavelength or more).

[0179] Therefore, in Arrangement Example 1, for example, a sub-array antenna configured by arranging a plurality of antenna elements in the vertical direction is used to narrow the directivity in the vertical direction, thereby improving the antenna gain in the vertical direction.

[0180] The distance between the transmitting antenna 106 and the receiving antenna 202 may be sufficiently wider than the size of the antenna elements, or they may be shifted in the horizontal direction so as not to overlap in the vertical direction.

[0181] As described above, Arrangement Example 1 is an antenna arrangement that allows the use of antenna elements of any lengthwise (for example, vertical) size, and also allows the suppression of grating lobes that occur in the virtual receiving array.

[0182] It should be noted that the same grating lobe suppression effect can be obtained even if the first diagonal antenna group and the second diagonal antenna group shown in Fig. 8 are arranged in any location. For example, in Arrangement Example 1, the first diagonal antenna group Rx#1 to Rx#4 and the second diagonal antenna group Rx#5 to Rx#8 are arranged so that their horizontal positions do not overlap each other, which makes it possible to arrange antenna elements with a larger vertical size.

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

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

[0185] Doppler frequency index f s_cfar The relative velocity component v d (f s_cfar), the following equation (20) may be used. Here, λ is the wavelength of the carrier frequency of the RF signal output from the transmitting radio unit (not shown). Also, Δ f is the Doppler frequency interval in the FFT processing in the Doppler analysis unit 210. For example, in this embodiment, Δ f =1 / {Loc×N code ×T r}.

number

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

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

[0188] This antenna arrangement configuration allows the radar device 10 to use antenna elements of any lengthwise size (for example, vertical size) in a MIMO array arrangement, and also allows grating lobes occurring in a virtual receiving array to be suppressed.

[0189] In addition, in Arrangement Example 1, as described above, a grating lobe suppression effect is obtained by the difference in the arrangement directions of the first diagonal antenna group and the second diagonal antenna group in the receiving antenna 202. For this reason, in Arrangement Example 1, for example, the element spacing of the transmitting antenna 106 can be set arbitrarily. Similarly, in Arrangement Example 1, the spacing between the first diagonal antenna group and the second diagonal antenna group can be set arbitrarily. As a result, the aperture length of the virtual receiving array can be expanded depending on at least one of the settings of the element spacing of the transmitting antenna 106 and the spacing between the first diagonal antenna group and the second diagonal antenna group, and therefore the vertical and horizontal angle measurement accuracy and angle separation performance of the radar device 10 can be improved.

[0190] Therefore, according to Arrangement Example 1, it is possible to suppress grating lobes and improve the angle measurement accuracy or resolution of the radar device 10.

[0191] In addition, in Arrangement Example 1, at least one of the transmitting antenna 106 and the receiving antenna 202 may further include an antenna element with respect 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 may include antenna elements arranged as shown in FIG. 8. In this case, for example, a relationship is established in which a virtual antenna is added additively to the position shown in Equation (16). For example, by adding an antenna element of 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 an antenna arrangement including such Arrangement Example 1, the effect of the above-mentioned Arrangement Example 1 is maintained, and the same effect as that of Arrangement Example 1 can be obtained.

[0192] For example, an antenna may be further added to the antenna configuration of Arrangement Example 1. The addition of an antenna makes it easier to further reduce the grating lobe or side lobe level suppressed by Arrangement Example 1 described above, thereby reducing erroneous detections during angle measurement in the radar device 10 and improving angle measurement performance. The addition of an antenna can be similarly applied to the subsequent arrangement examples or modified examples, and similar effects can be obtained.

[0193] Furthermore, in the MIMO array arrangement of arrangement example 1, an arrangement in which the horizontal direction and the vertical direction are swapped may be applied. In this case, the virtual receiving array arrangement is obtained by swapping the horizontal direction and the vertical direction, and angle separation performance is obtained by swapping the horizontal direction and the vertical direction. Note that the swapping of the horizontal direction and the vertical direction of the MIMO array arrangement can be similarly applied to the subsequent arrangement examples or modified examples, and the virtual receiving array arrangement in the subsequent arrangement examples is obtained by swapping the horizontal direction and the vertical direction.

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

[0195] [Modification 1 of Arrangement Example 1] In the first modification of the first arrangement example, for example, the distance between the first diagonal antenna group and the second diagonal antenna group (for example, the minimum distance) is N Tx It may be wider than the aperture length of the transmitting antenna 106 .

[0196] 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 This is narrower than the aperture length of each transmitting antenna 106 (for example, the distance between Tx#1 and Tx#6).

[0197] In a first modification of the first arrangement example, as shown in FIG. 15 (hereinafter also referred to as “arrangement example 1-1”), 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 It may be wider than the aperture length (eg, the distance between Tx#1 and Tx#6) of one transmitting antenna 106 (eg, corresponding to the third antenna group).

[0198] For example, in the case of the arrangement example 1-1 shown in FIG. 15, the minimum distance between the first diagonal antenna group and the second diagonal antenna group (the distance between Rx#4 and Rx#8) is N Tx= set to a spacing wider than the aperture length (e.g., the spacing between Tx#1 and Tx#6) of the six transmitting antennas 106. Note that in Arrangement Example 1-1 shown in Fig. 15, the spacing between the first diagonal antenna group and the second diagonal antenna group may be set to the same spacing as in Arrangement Example 1 (e.g., Fig. 8).

[0199] From the arrangement of transmitting antennas Tx#1 to Tx#6 and the arrangement of receiving antennas Rx#1 to Rx#8 as shown in FIG. 15, the position coordinates of virtual antennas VA#1 to #48 constituting a virtual receiving array antenna are calculated based on equation (16).

[0200] Fig. 16 is a diagram showing an example of the arrangement of a virtual receiving array obtained by the antenna arrangement shown in Fig. 15. As shown in Fig. 16, the horizontal aperture length of the virtual receiving array is wider than that in Fig. 9.

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

[0202] Figure 17 shows the MIMO array layout of layout example 1-1 (D H = 0.5λ, D V 17 shows the direction estimation result when a beamformer method is used as the direction of arrival estimation algorithm of direction estimator 213, using a lambda angle λ=0.5λ. As an example, Fig. 17 plots the output of the direction of arrival estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0203] Fig. 17(a) is a diagram showing normalized power values ​​in two dimensions, with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction, in a grayscale color map. Fig. 17(b) is a diagram showing Fig. 17(a) as a grayscale color map, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value. In Fig. 17, the normalized power value may be shown as a decibel value (dB) normalized by the peak power, for example.

[0204] As shown in (a) and (b) of FIG. 17, in Arrangement Example 1-1, similarly to Arrangement Example 1 (eg, FIG. 10), the peak level in the grating lobe direction is suppressed compared to the peak in the target true value direction.

[0205] In addition, in Arrangement Example 1-1, the virtual receiving array arrangement (e.g., the aperture length of the virtual receiving array) is wider in the horizontal direction than in Arrangement Example 1. Therefore, as shown in FIG. 17, the peak in the target true value direction is sharper in the horizontal direction than in FIG. 10, which makes it possible to improve the horizontal angle measurement accuracy or estimation accuracy of the radar device 10.

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

[0207] In this manner, in Arrangement Example 1-1, by increasing the distance between the first and second oblique antenna groups, the horizontal angle measurement accuracy or estimation accuracy can be improved, while the side lobe level to the side (horizontal direction) of the peak in the target true value direction increases. For example, the distance (e.g., minimum distance) between the first and second oblique antenna groups may be set within a suitable range depending on requirements such as the target to be detected by the radar device 10.

[0208] The respective arrangement directions (e.g., diagonal directions) of the first diagonal antenna group and the second diagonal antenna group may be mutually reversed with respect to the arrangement in Fig. 15, or the respective arrangements may be inverted left to right (e.g., horizontally), or up to down (e.g., vertically). Even in these cases, the same effect as in the above-mentioned Arrangement Example 1-1 can be obtained. The change in the respective arrangement directions 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 of Arrangement Example 1-1 shown in FIG. 15 are reversed to 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 arranged horizontally symmetrically. Therefore, Arrangement Example 1-1a shown in Fig. 18 is an arrangement in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group of Arrangement Example 1-1 are respectively inverted horizontally, and also an arrangement in which the first diagonal antenna group and the second diagonal antenna group of Arrangement Example 1-1 are respectively inverted vertically.

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

[0212] Furthermore, in an arrangement such as arrangement example 1-1 or arrangement example 1-1a, even if the vertical size of the transmitting antenna 106 is large, the receiving antenna 202 can be arranged on both sides of the transmitting antenna 106 (e.g., both sides in the horizontal direction), thereby achieving the effect of reducing the antenna mounting area.

[0213] [Modification 2 of Arrangement Example 1] In the second variation of the first arrangement example, for example, the interval (e.g., the minimum interval) between the first diagonal antenna group and the second diagonal antenna group may be closer than that in the first arrangement example. Also, in the second variation of the first arrangement example, for example, one antenna included in the plurality of receiving antennas 202 may be included in both the first diagonal antenna group and the second diagonal antenna group in a duplicated manner. In other words, the first diagonal antenna group and the second diagonal antenna group may include one or more shared antennas.

[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 This is narrower than the aperture length of each transmitting antenna 106 (for example, the distance between Tx#1 and Tx#6).

[0215] In a second variation of the first arrangement example, as shown in FIG. 20 (hereinafter referred to as "arrangement example 1-2a"), the first diagonal antenna group Rx#1-#4 and the second diagonal antenna group Rx#5-#8 may be arranged so that the minimum distance between them (for example, the distance between Rx#4 and Rx#8) is even closer than in FIG. 8.

[0216] Alternatively, in variant example 2 of arrangement example 1, for example, as shown in FIG. 21 (hereinafter referred to as "arrangement example 1-2b"), some antennas (e.g., 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 the arrangement example 1-2a shown in FIG. Tx The transmitting antennas Tx#1 to #6 are spaced apart by 4.5 wavelengths (for example, 9D H ) are arranged at equal intervals in the horizontal direction, 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 the basic horizontal interval D H In FIG. 20, the aperture length (for example, 7D) of the receiving antennas 202 (Rx#1 to #8) in the horizontal direction is set to H ) is the element spacing of the transmitting antenna 106 (for example, 9D H ) is narrower than

[0218] For example, in the case of the arrangement example 1-2b shown in FIG. Tx The transmitting antennas Tx#1 to #6 are spaced apart by 3.5 wavelengths (for example, 7D H) are arranged at equal intervals in the horizontal direction, and among Na=7 receiving antennas Rx#1 to #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, the aperture length (for example, 6D H ) is the element spacing of the transmitting antenna 106 (for example, 7D H ) is narrower than

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

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

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

[0222] 24 and 25 show the MIMO array arrangements of Arrangement Example 1-2a and Arrangement Example 1-2b (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation unit 213. As an example, Fig. 24 and Fig. 25 plot the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

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

[0224] As shown in FIGS. 24 and 25, in Arrangement Example 1-2a and Arrangement Example 1-2b, similar to Arrangement Example 1 (eg, FIG. 10), the peak level in the grating lobe direction is suppressed compared to 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 if the vertical size of the transmitting antenna 106 is large, the receiving antenna 202 can be arranged between the elements of the transmitting antenna 106, thereby achieving the effect of reducing the antenna mounting area.

[0226] In addition, in the arrangements such as Arrangement Example 1-2a and Arrangement Example 1-1b, since the virtual antennas are arranged without overlapping, the element spacing of the transmitting antenna 106 is arranged to be wider than the horizontal aperture length of the receiving antenna 202. As a result, the horizontal aperture length of the virtual antenna is wider, the peak in the target true value direction becomes sharper in the horizontal direction, and the horizontal angle measurement accuracy or resolution is improved. In addition, compared to the case where the element spacing of the transmitting antenna 106 is wider in Arrangement Example 1, the arrangements of Arrangement Example 1-2a and Arrangement Example 1-1b can further suppress the variation in the horizontal spacing of the virtual antennas, and can also obtain the effect of further reducing the rise of the side lobe near the main lobe.

[0227] In addition, in Arrangement Example 1-2a, the element spacing of the transmitting antenna 106 is wider than that in Arrangement Example 1-2b, and the horizontal aperture length in the virtual receiving array arrangement is expanded. Therefore, in Arrangement Example 1-2a, the peak in the target true value direction becomes sharper in the horizontal direction due to the increased element spacing of the transmitting antenna 106, and therefore the horizontal angle measurement accuracy or estimation accuracy of the radar device 10 can be improved. Note that, although the increased element spacing of the transmitting antenna 106 may cause more grating lobes, it can be confirmed that the grating lobes are suppressed by Arrangement Example 1-2a, as shown in Fig. 24.

[0228] Furthermore, compared to Arrangement Example 1-2a, Arrangement Example 1-2b has a smaller number of receiving antennas 202. Therefore, in Arrangement Example 1-2b, the reduction in the number of receiving antennas 202 simplifies the antenna configuration in the radar device 10 and can suppress grating lobes.

[0229] Note that in FIG. 21, a case has been described in which the end antennas of the first diagonal antenna group and the second diagonal antenna group (e.g., Rx#4) overlap; however, this is not limited thereto. For example, the antennas overlapping in the first diagonal antenna group and the second diagonal antenna group may be antennas different from the end antennas of each diagonal antenna group.

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

[0231] For example, in a third variation of the first arrangement example, the inclinations of the first and second diagonal antenna groups are set to be gentler than those in the first arrangement example.

[0232] For example, in the case of arrangement example 1, as shown in FIG. 8, the first diagonal antenna group Rx#1-#4 are arranged so as to be shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths and also shifted downwards in the vertical direction at intervals of 0.5 wavelengths, and the second diagonal antenna group Rx#5-#8 are arranged so as to be shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths and also shifted downwards in the vertical direction at intervals of 0.5 wavelengths.

[0233] In the third variation of the first arrangement example, as shown in FIG. 26 (hereinafter referred to as "arrangement example 1-3"), the first diagonal antenna group Rx#1-#4 is shifted horizontally from left to right in the figure by an interval of one wavelength, and is also shifted downwards by an interval of 0.5 wavelengths in the vertical direction. Also, as shown in FIG. 26, the second diagonal antenna group Rx#5-#8 is shifted horizontally from right to left in the figure by an interval of one wavelength, and is also shifted downwards by an interval of 0.5 wavelengths in the vertical direction. In the first and second diagonal antenna groups in the arrangement example 1-3 shown in FIG. 26, the inclinations of the first and second diagonal antenna groups may be set in the same manner as in the first arrangement example (for example, FIG. 8).

[0234] As described above, in Fig. 26, the change in vertical position with respect to the horizontal direction between adjacent antennas in each of the first diagonal antenna group and the second diagonal antenna group is smaller than in Fig. 8. In other words, the inclination of the first diagonal antenna group and the second diagonal antenna group is gentler in Fig. 26 than in Fig. 8.

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

[0236] Fig. 27 is a diagram showing an example of the arrangement of a virtual receiving array obtained by the antenna arrangement shown in Fig. 26. The aperture length of the virtual receiving array shown in Fig. 27 is wider than that of Arrangement Example 1 (Fig. 9) due to the gentler inclination of the first diagonal antenna group and the second diagonal antenna group.

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

[0238] FIG. 28 shows the MIMO array arrangement of arrangement example 1-3 (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation unit 213. Fig. 28 shows, as an example, the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0239] Fig. 28(a) is a diagram showing normalized power values ​​in two dimensions, with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction, in a grayscale color map. Fig. 28(b) is a diagram showing Fig. 28(a) as a grayscale color map, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value. In Fig. 28, the normalized power value may be shown as a decibel value (dB) normalized by the peak power, for example.

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

[0241] In addition, in Arrangement Example 1-3, compared to Arrangement Example 1, the virtual receiving array arrangement (e.g., the aperture length of the virtual receiving array) is wider in the horizontal direction, so that the peak of the target true value direction becomes sharper in the horizontal direction as shown in FIG. 28, which makes it possible to improve the horizontal angle measurement accuracy or estimation accuracy of the radar device 10.

[0242] Furthermore, in Arrangement Example 1-3, for example, an effect is obtained that an antenna arrangement is possible when the antenna size in the horizontal direction is large (e.g., one wavelength or more) in addition to when the antenna size in the vertical direction of the transmitting antenna 106 is large (e.g., one wavelength or more). For example, the larger the antenna size in the horizontal direction, the narrower the horizontal viewing angle can be, and the more directional gain can be improved, thereby improving the radar performance for detecting targets further away within a narrower (e.g., limited) horizontal viewing angle.

[0243] 28, in Arrangement Example 1-3, a side lobe of about -10 dB may occur next to (in the horizontal direction) the peak in the target true value direction, as compared with Arrangement Example 1 (e.g., FIG. 10). The occurrence of this side lobe is caused by, for example, the fact that the interval (e.g., the minimum interval) between the first diagonal antenna group and the second diagonal antenna group is larger than that in Arrangement Example 1.

[0244] For example, by increasing the distance between the first diagonal antenna group and the second diagonal antenna group, the horizontal angle measurement accuracy or estimation accuracy can be improved, while the side lobe level to the side (horizontal direction) of the peak in the target true value direction increases. For example, the distance (e.g., minimum distance) between the first diagonal antenna group and the second diagonal antenna group may be set within a suitable range depending on requirements such as the target to be detected by the radar device 10.

[0245] In addition, in FIG. 26, a case has been described in which the distance (e.g., the minimum distance) between the first diagonal antenna group and the second diagonal antenna group is wider than the aperture length of the transmitting antenna 106; however, this is not limited thereto, and the distance (e.g., the minimum distance) 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 transmitting antenna 106.

[0246] In addition, in the third variation of Arrangement Example 1, the inclination of the first and second diagonal antenna groups is set to be gentler than that of Arrangement Example 1, but the present invention is not limited thereto, and the inclination of the first and second diagonal antenna groups may be set to be steeper than that of Arrangement Example 1. When the inclination of the first and second diagonal antenna groups is to be steeper, the fourth variation of Arrangement Example 1 or Arrangement Example 2 described later may be applied.

[0247] [Modification 4 of Arrangement Example 1] For example, in the arrangement example 1 shown in Fig. 8, the first diagonal antenna group Rx#1-#4 and the second diagonal antenna group Rx#5-#8 are arranged in horizontally inverted symmetry, but 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 horizontally inverted symmetry. For example, the arrangement directions of the first diagonal antenna group and the second diagonal antenna group may be different directions and not parallel to each other.

[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 inclination (e.g., a change in position in the vertical direction relative to the horizontal direction), or different antenna spacing may be set in each of the horizontal and vertical directions.

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

[0250] Furthermore, for example, as shown in FIG. 31 (hereinafter, "Arrangement Example 1-4c"), the number of antennas included in the first diagonal antenna group and the number of antennas included in the second diagonal antenna group may differ.

[0251] Also, for example, any two or three of the arrangement examples 1-4a (asymmetric inclination), 1-4b (vertically shifted position), and 1-2c (number of antennas) may be combined. For example, FIG. 32 (hereinafter referred to as "arrangement example 1-4d") shows an arrangement that combines arrangement examples 1-4a, 1-4b, and 1-4c.

[0252] 29, when the first diagonal antenna group and the second diagonal antenna group have asymmetric inclinations, the arrangement direction of the first diagonal antenna group and the arrangement direction of the second diagonal antenna group may be rotationally symmetric with each other by about 90 degrees. In this case, for example, the direction in which grating lobes are generated due to the relationship between the transmitting antenna 106 and the first diagonal antenna group and the direction in which grating lobes are generated due to the relationship between the transmitting antenna 106 and the second diagonal antenna group are rotationally symmetric with each other by about 90 degrees in a horizontal and vertical two-dimensional plane, so that the interval between the grating lobes is likely to become larger.

[0253] Such an arrangement in which the arrangement direction of the first oblique antenna group and the arrangement direction of the second oblique antenna group are rotationally symmetrical to each other by about 90 degrees is more suitable, for example, when the number of antennas of the radar device 10 is smaller. For example, the fewer the number of antennas of the radar device 10, the wider the beam width of the main beam in direction estimation tends to be. For this reason, when the directions of the suppressed grating lobes are close to each other, the fewer the number of antennas of the radar device 10, the wider the beam width is, and the more likely it is that the suppressed grating lobe power will overlap and the grating lobe power will increase. For this reason, the fewer the number of antennas of the radar device 10, the more likely it is that the grating lobe suppression performance will deteriorate and the probability of false detection in the radar device 10 will increase. Therefore, when the number of antennas of the radar device 10 is small, for example, an arrangement in which the arrangement direction of the first oblique antenna group and the arrangement direction of the second oblique antenna group are rotationally symmetrical to each other by about 90 degrees can suppress the overlap of the grating lobe power, thereby improving the grating lobe suppression performance.

[0254] From the arrangement of transmitting antennas Tx#1 to Tx#6 and the arrangement of receiving antennas Rx#1 to Rx#8 or receiving antennas Rx#1 to Rx#7 as shown in Figures 29 to 32, the position coordinates of virtual antennas VA#1 to VA#48 or VA#1 to VA#42 that constitute a virtual receiving array antenna are calculated based on equation (16).

[0255] 33 to 36 are diagrams showing examples of virtual receiving array arrangements obtained by the antenna arrangements shown in FIGS. 29 to 32, respectively.

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

[0257] 37 to 40 show the MIMO array arrangements (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation section 213. As an example, Figs. 37 to 40 plot the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0258] 37 to 40(a) are diagrams showing normalized power values ​​in two dimensions with the horizontal axis in the horizontal direction and the vertical axis in the vertical direction, as a grayscale color map. Also, FIG. 37 to 40(b) are diagrams showing the normalized power values ​​in FIG. 37 to 40(a), as a grayscale color map, with the horizontal axis in the horizontal direction and the vertical axis as normalized power values. In FIG. 37 to 40, the normalized power values ​​may be shown as decibel values ​​(dB) normalized by peak power, for example.

[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 compared to the peak in the target true value direction.

[0260] [Modification 5 of Arrangement Example 1] In the arrangement example 1 and the modifications 1 to 4, for example, the interval between the transmitting antennas is set to the basic interval D H and the inclination of the receiving antenna 202 in the diagonal direction is set to an integer multiple of the basic interval D H In the vertical direction, the basic interval D V In the above, the case where the frequency is set to an integer multiple of .

[0261] That is, N Tx The transmitting antennas 106 are arranged in the horizontal direction with a transmitting antenna spacing of dT×D H are placed in.

[0262] In addition, among the Na receiving antennas 202, the first diagonal antenna group and the second diagonal antenna group are arranged in different diagonal directions. In addition, the first diagonal antenna group is arranged in a horizontal direction with a distance of dRH1×D H and shifts vertically at intervals of D V The second diagonal antenna group is arranged in a diagonal direction shifted at intervals of dRH2×D H and shifts vertically at intervals of D V The pixels are arranged diagonally, shifting at intervals of .

[0263] Here, dT is an integer of 2 or more, and dRH1 and dRH2 are each an integer of 1 or more. H and basic interval D Vmay be, for example, a value within a 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 arranged symmetrically in the horizontal direction. When dRH1≠dRH2, the first diagonal antenna group and the second diagonal antenna group are arranged asymmetrically in the horizontal direction.

[0264] For example, each of Figures 41 to 44 shows an example of antenna arrangement where dRH1 = dRH2 and dT = 2, 4, 5, 7. Also, Figures 41 to 43 show the case where dRH1 = dRH2 = 1, and Figure 44 shows the case where dRH1 = dRH2 = 2. Hereinafter, the antenna arrangement examples in Figures 41 to 44 will also be 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 it is that the direction of a grating lobe generated due to the relationship between transmitting antenna 106 and the first diagonal antenna group will coincide with the direction of a grating lobe generated due to the relationship between transmitting antenna 106 and the second diagonal antenna group. Therefore, for example, as shown in Figures 41 to 44, the larger dT is, the closer the first diagonal antenna group and the second diagonal antenna group may be arranged. By arranging the first diagonal antenna group and the second diagonal antenna group closer to each other, the distance between adjacent virtual antennas in the virtual receiving array can be narrowed, making it possible to suppress grating lobes.

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

[0267] 45 to 48 are diagrams showing examples of virtual receiving array arrangements obtained by the antenna arrangements shown in FIGS. 41 to 44, respectively.

[0268] Next, an example of a direction estimation result (a computer simulation result) when the antenna arrangements according to the above-mentioned Arrangement Example 1-5a to Arrangement Example 1-5d are applied will be described.

[0269] 49 to 52 are diagrams showing the MIMO array arrangements (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation section 213. As an example, Figs. 49 to 52 plot the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0270] 49 to 52(a) are diagrams showing normalized power values ​​in two dimensions with the horizontal axis in the horizontal direction and the vertical axis in the vertical direction, as a grayscale color map. Also, FIG. 49 to 52(b) are diagrams showing FIG. 49 to 52(a) with the horizontal axis in the horizontal direction and the vertical axis as normalized power values, as a grayscale color map. In FIG. 49 to 52, the normalized power values ​​may be shown as decibel values ​​(dB) normalized by peak power, for example.

[0271] As shown in Figs. 49 to 52, according to Arrangement Example 1-5a to Arrangement Example 1-5d, similar to Arrangement Example 1 (Fig. 10), the peak level in the grating lobe direction is suppressed compared to the peak in the target true value direction.

[0272] Furthermore, as shown in, for example, arrangement example 1-5a (dT=2), arrangement example 1-5b (dT=4), arrangement example 1-5c (dT=5), and arrangement example 1-5d (dT=7), the larger dT is, the wider the virtual receiving array arrangement (e.g., the aperture length of the virtual receiving array) is in the horizontal direction. As a result, as shown in Figures 49 to 52, the peak in the target true value direction becomes sharper in the horizontal direction, which makes it possible to improve the horizontal angle measurement accuracy or estimation accuracy of the radar device 10.

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

[0274] The inclination of the first and second diagonal antenna groups is dRH1×D in the horizontal direction. H Or dRH2×D H and shifts vertically at intervals of D V An interval that is an integer multiple larger than the interval (for example, dRV×D V When the shift is made by dRV (where dRV is an integer equal to or greater than 2), the direction of the vertical grating lobes generated due to the relationship between transmitting antenna 106 and the first diagonal antenna group tends to coincide with the direction of the vertical grating lobes generated due to the relationship between transmitting antenna 106 and the second diagonal antenna group.

[0275] Therefore, for example, the first diagonal antenna group is dRH1×D in the horizontal direction. H and shifts vertically at intervals of D V Interval (or dRV×D V and dRV=1), and the second diagonal antenna group is arranged in a diagonal direction shifting by dRH2×D H and shifts vertically at intervals of D V Interval (or dRV×D V and dRV=1), the pixel may be arranged in a diagonal direction shifting the pixel by 1.

[0276] In addition, the inclination of the first diagonal antenna group and the second diagonal antenna group is dRH1×D H Or dRH2×D H and shifts vertically at intervals of D VWhen the antennas are shifted by an interval that is an integer multiple larger than the interval between the antennas, for example, Arrangement Example 1-4a, or Arrangement Example 2 and its modified examples described below may be applied. A virtual receiving array configured using Arrangement Example 2 and its modified examples described below can increase the antenna interval in the vertical direction and the aperture length in the vertical direction, thereby improving the angle measurement accuracy or resolution in the radar device 10 in the vertical direction (examples will be described later).

[0277] In addition, in Arrangement Example 1 and Modifications 1 to 5, the spacing between the transmitting antennas is set to the horizontal basic spacing D H The horizontal direction is set to an integer multiple of the horizontal basic interval D H The vertical direction is set to an integer multiple of the basic vertical interval D V Although an example in which the interval is set to an integer multiple of D V , D H The arrangement may be other than an integer multiple of .

[0278] For example, N Tx The transmitting antennas 106 are arranged horizontally at intervals of α H For example, the Na receiving antennas 202 may be arranged such that the first diagonal antenna group and the second diagonal antenna group are arranged in different diagonal directions that are not parallel to each other, and the horizontal direction is determined by β H and shifts vertically at intervals of γD V The pixels may be arranged in a diagonal direction shifted at intervals of .

[0279] Here, α, β, and γ are positive real values, and αD H is one or more wavelengths, and βD H and γD V may be a real value of 0.45 to 0.8 wavelengths or more, and the same effects as those of the 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"), D V =0.5 wavelength, D H = 0.5 wavelength, αD H =2.7 wavelength, βD V=0.45 wavelength, γD H = 0.6 wavelengths.

[0281] From the arrangement of transmitting antennas Tx#1 to Tx#6 and the arrangement of receiving antennas Rx#1 to Rx#8 as shown in Fig. 53, the position coordinates of virtual antennas VA#1 to #48 constituting a virtual receiving array antenna are calculated based on equation (16). Fig. 54 is a diagram showing an example of the arrangement of a virtual receiving array obtained by the antenna arrangement shown in Fig. 53.

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

[0283] FIG. 55 shows the MIMO array arrangement of the arrangement example 1-5e shown in FIG. H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation unit 213. As an example, Fig. 55 plots the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0284] Note that Fig. 55(a) is a diagram showing normalized power values ​​in two dimensions, with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction, in a grayscale color map. Fig. 55(b) is a diagram showing Fig. 55(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. Note that 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 Example 1-5e, similarly to Arrangement Example 1 (FIG. 10), the peak level in the grating lobe direction is suppressed compared to the peak in the target true value direction.

[0286] [Modification 6 of Arrangement Example 1] In at least one of the transmitting antenna 106 and the receiving antenna 202 (e.g., the first diagonal antenna group and the second diagonal antenna group), the spacing between adjacent antennas is not limited to being equal, and may include one or more unequal spacings.

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

[0288] In addition, in the antenna arrangement example shown in Fig. 57 (hereinafter, "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 arrangement intervals of the first diagonal antenna group and the second diagonal antenna group may be different from those of Arrangement Example 1 (e.g., Fig. 8).

[0289] In addition, in an antenna arrangement example shown in Fig. 58 (hereinafter, "arrangement example 1-6c"), the transmitting 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 different arrangement intervals of the transmitting antenna 106, the first diagonal antenna group, and the second diagonal antenna group may be the same as in arrangement example 1 (e.g., Fig. 8).

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

[0291] In addition, the arrangement is not limited to the above-mentioned example, and for example, either one of the first diagonal antenna group or the second diagonal antenna group may be arranged at uneven intervals, or either one of the first diagonal antenna group or the second diagonal antenna group and the transmitting antenna 106 may be arranged at uneven intervals.

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

[0293] Examples of the multi-stage configuration include a configuration in which the transmitting antennas 106 are arranged in two stages in the vertical direction, a configuration in which the transmitting antennas 106 are 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 receiving 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 receiving 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 of Arrangement Example 1 described above can be maintained. Furthermore, the horizontal multi-stage configuration increases the aperture length of the virtual receiving array in the horizontal direction, thereby improving the horizontal angle measurement accuracy or resolution of the radar device 10. Furthermore, for example, the vertical multi-stage configuration increases the aperture length of the virtual receiving array in the vertical direction, thereby improving the vertical angle measurement accuracy or resolution of the radar device 10. Furthermore, for example, the vertical and horizontal multi-stage configuration increases the aperture length of the virtual receiving array in the vertical and horizontal directions, thereby improving the vertical and horizontal angle measurement accuracy or resolution of the radar device 10.

[0295] In the case of a multi-stage configuration, a common arrangement of transmitting antennas Tx or receiving antennas Rx may be configured in multiple stages in at least one of the vertical and horizontal directions, or different arrangements of transmitting antennas Tx or receiving antennas Rx may be configured in multiple stages in at least one of the vertical and horizontal directions.

[0296] Hereinafter, examples of antenna arrangements in Arrangement Examples 1-7 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 in the same arrangement as Tx #1 to Tx #6 are shifted vertically and arranged in multiple stages. That is, in Fig. 59, the multiple transmitting antennas 106 have multiple sets of six antennas arranged in the horizontal direction (for example, a set of Tx #1 to #6 and a 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 in the same arrangement as Rx#1 to Rx#8 are shifted in the horizontal direction and arranged in multiple stages. That is, in Fig. 60, the multiple receiving antennas 202 have multiple sets of the first diagonal antenna group and the second diagonal antenna group (for example, a set of Rx#1 to #8 and a 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, which are arranged differently from Rx#1 to Rx#8, are arranged in multiple stages in the vertical direction. That is, in Fig. 61, the multiple receiving antennas 202 have multiple sets of the first diagonal antenna group and the second diagonal antenna group (for example, a set of Rx#1 to #8 and a set of Rx#9 to #16).

[0300] Also, for example, in FIG. 62 (hereinafter, "arrangement example 1-7d"), Tx#1-Tx#6 and Tx#7-Tx#8 in the same arrangement as Tx#1-Tx#6 are arranged in multiple stages by shifting them vertically, and Rx#1-Rx#8 and Rx#9-Rx#16 in a different arrangement from Rx#1-Rx#8 are arranged in multiple stages vertically. That is, in FIG. 62, the multiple transmitting antennas 106 have multiple sets of six antennas arranged in the horizontal direction (for example, a set of Tx#1-#6 and a set of Tx#7-#12). Also, in FIG. 62, the multiple receiving antennas 202 have multiple sets of first diagonal antenna groups and second diagonal antenna groups (for example, a set of Rx#1-#8 and a set of Rx#9-#16).

[0301] From the arrangement of transmitting antennas and the arrangement of receiving antennas as shown in FIGS. 59 to 62, the position coordinates of the virtual antennas constituting the virtual receiving array antenna are calculated based on equation (16).

[0302] 63 to 66 are diagrams showing examples of virtual receiving array arrangements obtained by the antenna arrangements shown in FIGS. 59 to 62, respectively.

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

[0304] 67 to 70 show the MIMO array arrangements (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation section 213. As an example, Figs. 67 to 70 plot the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0305] 67 to 70(a) are diagrams showing normalized power values ​​in two dimensions with the horizontal axis in the horizontal direction and the vertical axis in the vertical direction, as a grayscale color map. Also, FIG. 67 to 70(b) are diagrams showing FIG. 67 to 70(a) with the horizontal axis in the horizontal direction and the vertical axis as normalized power values, as a grayscale color map. In FIG. 67 to 70, the normalized power values ​​may be shown as decibel values ​​(dB) normalized by peak power, for example.

[0306] As shown in Figs. 67 to 70, in Arrangement Example 1-7a to Arrangement Example 1-7d, similarly to Arrangement Example 1 (Fig. 10), the peak level in the grating lobe direction is suppressed compared to the peak in the target true value direction.

[0307] In addition, in Arrangement Example 1-7a (Fig. 59), the number of transmitting antennas Tx is increased compared to Arrangement Example 1 (Fig. 8), and the elements of the transmitting antenna 106 are shifted in the vertical direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7a, the aperture length in the vertical direction of the virtual receiving array is expanded, so that the peak in the target true value direction becomes sharper in the vertical direction as shown in Fig. 67, and it is possible to improve the angle measurement accuracy or estimation accuracy in the vertical direction of the radar device 10.

[0308] In addition, in Arrangement Example 1-7b (Fig. 60), the number of receiving antennas Rx is increased compared to Arrangement Example 1 (Fig. 8), and the elements of the receiving antenna 202 are shifted in the horizontal direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7b, the horizontal aperture length of the virtual receiving array is expanded, so that the peak of the target true value direction becomes sharper in the horizontal direction as shown in Fig. 68, and it is possible to improve the horizontal angle measurement accuracy or estimation accuracy of the radar device 10.

[0309] In addition, in Arrangement Example 1-7c (Fig. 61), the number of receiving antennas Rx is increased compared to Arrangement Example 1 (Fig. 8), and the elements of the receiving antenna 202 are shifted in the vertical direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7c, the aperture length in the vertical direction of the virtual receiving array is expanded, so that the peak in the target true value direction becomes sharper in the vertical direction as shown in Fig. 69, and it is possible to improve the angle measurement accuracy or estimation accuracy in the vertical direction of the radar device 10.

[0310] Moreover, in Arrangement Example 1-7d (Fig. 62), the number of transmitting antennas Tx and receiving antennas Rx is increased compared to Arrangement Example 1 (Fig. 8), and the elements of both the transmitting antenna 106 and the receiving antenna 202 are shifted in the vertical direction and arranged in multiple stages. Therefore, in Arrangement Example 1-7d, the aperture length in the vertical direction of the virtual receiving array is expanded, so that, as shown in Fig. 70, the peak of the target true value direction becomes sharper in the vertical direction compared to Arrangement Example 1-7a (e.g., Fig. 59), and the vertical angle measurement accuracy or estimation accuracy of the radar device 10 can be improved.

[0311] In addition, different antenna elements (for example, antenna elements of different sizes) may be used in combination in the multi-stage configuration in Arrangement Example 1-7. For example, the multiple transmitting 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 directional gain than the SR antenna element by narrowing the directivity in the vertical direction, the horizontal direction, or both. 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 longer distance compared to when the SR antenna element is used, and enables detection of a target at a longer distance. Since the LR antenna element has a higher directional gain in the vertical direction, the horizontal direction, or both, its physical size is larger in the vertical direction, the horizontal direction, or both than the size of the SR antenna element.

[0312] For example, in a multi-stage configuration, a long-distance (LR) antenna element may be applied to the first stage, and a short-distance (SR) antenna element may be used in combination with the second stage. For example, as shown in Fig. 59, when the transmitting antennas 106 are arranged in a two-stage multi-stage configuration in the vertical direction, a long-distance (LR) antenna element may be applied to the first stage (e.g., Tx#1 to Tx#6), and a short-distance (SR) antenna element may be applied to the second stage (e.g., Tx#7 to Tx#12).

[0313] In addition, if the vertical and horizontal sizes of the long-distance (LR) antenna elements are large, the elements of one stage may be shifted horizontally so that the first stage transmitting antennas 106 and the second stage transmitting antennas 106 do not overlap.

[0314] In this way, when an antenna for LR and an antenna for SR are used for the transmitting antenna 106, for example, an antenna for SR (for example, an antenna having a characteristic of having a wide viewing angle) may be applied to the receiving antenna 202. This makes it possible to accommodate the detection ranges of both the LR and SR modes while maintaining the effect of Arrangement Example 1.

[0315] [Variation 8 of Arrangement Example 1] Regarding placement condition 1, N Tx The case where the arrangement direction of the transmitting antennas 106 is horizontal has been described. Tx The arrangement directions of the transmitting antennas 106 do not need to strictly coincide with the horizontal direction.

[0316] For example, as shown in FIG. 71 (hereinafter referred to as "Arrangement Example 1-8"), the transmitting antenna groups Tx#1 to #6 are arranged at intervals of one wavelength (for example, 2D H ) and vertically at intervals of 0.25 wavelengths (e.g., 0.5D V ) may be arranged with a shift upward. For example, if the inclination of the transmitting 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 arrangement of the receiving antennas Rx#1 to Rx#8 is not limited to the example shown in Fig. 71, and other arrangements may be used.

[0317] From the arrangement of transmitting antennas Tx#1 to Tx#6 and the arrangement of receiving antennas Rx#1 to Rx#8 as shown in Fig. 71, the position coordinates of virtual antennas VA#1 to #48 constituting a virtual receiving array antenna are calculated based on equation (16). Fig. 72 is a diagram showing an example of the arrangement of a virtual receiving array obtained by the antenna arrangement shown in Fig. 71.

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

[0319] Figure 73 shows the MIMO array layout of layout example 1-8 (D H = 0.5λ, D V= 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimator 213. As an example, Fig. 73 plots the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0320] Note that Fig. 73(a) is a diagram showing normalized power values ​​in two dimensions, with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction, in a grayscale color map. Fig. 73(b) is a diagram showing Fig. 73(a) as normalized power values, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values, in a grayscale color map. Note that in Fig. 73, the normalized power values ​​may be shown, for example, as decibel values ​​(dB) normalized by peak power.

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

[0322] Moreover, in Arrangement Example 1-8, the transmitting antennas 106 are arranged at a gentle incline with respect to the horizontal direction, compared to Arrangement Example 1 (e.g., FIG. 8). In other words, in Arrangement Example 1-8, the arrangement of the transmitting antennas 106 also has a vertical expansion. For this reason, in the virtual receiving array arrangement, the aperture length in the vertical direction is wider, and as shown in FIG. 73, the peak of the target true value direction becomes sharper in the vertical direction, which makes it possible to improve the vertical angle measurement accuracy or estimation accuracy of the radar device 10. Note that, in Arrangement Example 1-8, the transmitting beam direction is gently inclined, so that the range in which grating lobes occur tends to expand in the horizontal direction.

[0323] The modified examples of Arrangement Example 1 have been described above.

[0324] [Minimum antenna configuration for layout condition 1 and layout example with a small number of antennas] Below, we will explain the minimum antenna configuration that satisfies the placement condition 1, and a placement example in which the number of antennas that satisfies the placement condition 1 is small. Note that the same effect can be obtained by modifying the antenna placement described below in accordance with the modification of the above-mentioned placement example 1.

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

[0326] Figure 74 shows the minimum number of antennas for placement condition 1 (number of transmitting antennas N Tx FIG. 74(a) shows an example of a MIMO antenna arrangement, and FIG. 74(b) shows an example of a virtual receiving array arrangement configured by the MIMO antenna arrangement shown in FIG. 74(a). In FIG. 74, the scales of the horizontal and vertical axes are, for example, D H , D V Let us assume that.

[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] 75 to 79 show examples of antenna arrangements when the number of antennas that satisfy arrangement condition 1 is small. (a) of Fig. 75 to 79 shows an example of a MIMO antenna arrangement, and (b) of Fig. 75 to 79 shows an example of a virtual receiving array arrangement configured by the MIMO antenna arrangement shown in (a) of Fig. 75 to 79. In Fig. 75 to 79, the scales of the horizontal and vertical axes are, for example, D H , D V Let us assume that.

[0329] For example, Figs. 75 and 76 show the case where the number of transmitting antennas is N Tx76 shows an example of antenna arrangement when the number of receiving antennas Na=2 and the number of receiving antennas Na=4. In Fig. 75 and Fig. 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] For example, FIG. 77 shows the case where the number of transmitting antennas is N Tx 77 shows an example of antenna arrangement when the number of receiving antennas Na=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] For example, FIG. 78 and FIG. 79 show the case where the number of transmitting antennas is N Tx 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] An example of placement condition 1 has been described above.

[0333] [Placement condition 2] N Tx The transmitting antenna 106 includes a "first diagonal antenna group" arranged in a "first diagonal direction" and a "second diagonal antenna group" arranged in a "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 from each other. The Na receiving antennas 202 include a "third diagonal antenna group" arranged in a "third diagonal direction" and a "fourth diagonal antenna group" arranged in a "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 directions from each other.

[0334] Each of the first diagonal antenna group (e.g., corresponding to the third antenna group) and the second diagonal antenna group (e.g., corresponding to the fourth antenna group) may include at least two transmitting antennas 106. Also, each of the third diagonal antenna group (e.g., corresponding to the first antenna group) and the fourth diagonal antenna group (e.g., corresponding to the second antenna group) may include at least two receiving antennas 202.

[0335] Grating lobes can be suppressed by arranging the first diagonal antenna group and the second diagonal antenna group that satisfy the arrangement condition 2 at arbitrary positions. For example, as shown in the following arrangement example or modification, by arranging the first diagonal antenna group and the second diagonal antenna group so that their horizontal positions do not overlap each other, it is possible to arrange transmitting antenna elements that are large in size in the vertical direction.

[0336] Similarly, grating lobes can be suppressed by arranging the third diagonal antenna group and the fourth diagonal antenna group, which satisfy the arrangement condition 2, at arbitrary positions. For example, as shown in the following arrangement example or modification, by arranging the third diagonal antenna group and the fourth diagonal antenna group so that their horizontal positions do not overlap each other, it is possible to arrange receiving antenna elements with a large vertical size.

[0337] In placement condition 2, for example, the transmitting antenna 106 includes a first diagonal antenna group arranged in a first diagonal direction and a second diagonal antenna group arranged in a second diagonal direction. Therefore, compared to placement condition 1, the vertical aperture length of the virtual receiving array can be further enlarged, thereby improving the vertical angle measurement accuracy or resolution of the radar device 10.

[0338] Moreover, in the arrangement condition 2, for example, it is possible to suppress grating lobes in the vertical direction that are generated when the inclinations of the first to fourth oblique directions are made steeper with respect to the horizontal direction. This grating lobe suppression effect can further increase the aperture length in the vertical direction, and further improve the vertical angle measurement accuracy or resolution of the radar device 10.

[0339] The following describes an example of placement condition 2. The following describes a placement example that satisfies placement condition 2, and an example of a direction estimation result by computer simulation in that placement example.

[0340] <Layout example 2> 80 is a diagram showing an example of arrangement (for example, an example of a MIMO antenna arrangement) of the transmitting antenna 106 (for example, represented as Tx) and the receiving antenna 202 (for example, represented as Rx) according to Arrangement Example 2. In FIG. 80, the scales of the horizontal and vertical axes are, for example, a basic interval D in the horizontal direction. H , and the basic vertical spacing D V The scales of the horizontal and vertical axes are the same for the MIMO antenna arrangements in the following other examples. H and D. V may be spaced at intervals of 0.5 wavelengths.

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

[0342] In Figure 80, N Tx The six transmitting antennas Tx#1 to #6 include a first group of diagonal antennas Tx#1 to #3 arranged in a first diagonal direction and a second group of diagonal antennas Tx#4 to #6 arranged in a second diagonal direction. In Fig. 80, the first and second diagonal directions are not parallel to each other but are different from each other.

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

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

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

[0346] For example, the first diagonal antenna group Tx #1-#3 shown in Fig. 80 are shifted horizontally from left to right in the figure at intervals of 1.5 wavelengths, and are also shifted upwards in the vertical direction at intervals of 0.5 wavelengths. The second diagonal antenna group Tx #4-#6 shown in Fig. 80 are shifted horizontally from left to right in the figure at intervals of 1.5 wavelengths, and are also shifted downwards in the vertical direction at intervals of 0.5 wavelengths.

[0347] 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 to the vertical direction (a line perpendicular to the horizontal direction). In other words, the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 are arranged in a horizontally inverted symmetrical (or left-right inverted symmetrical or mirror symmetrical) arrangement.

[0348] Here, the transmitting antenna 106 in Arrangement Example 1 (for example, FIG. 8) is arranged in the horizontal direction. On the other hand, the transmitting antenna 106 in Arrangement Example 2 is arranged in the diagonal direction as shown in FIG. 80. In other words, since the transmitting antenna 106 in Arrangement Example 2 is arranged two-dimensionally, horizontally and vertically, compared to Arrangement Example 1, Arrangement Example 2 can have a larger aperture in the vertical direction.

[0349] Also, for example, the third diagonal antenna group Rx#1-#4 shown in Fig. 80 are shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths, and are also shifted downwards in the vertical direction at intervals of one wavelength. Also, the fourth diagonal antenna group Rx#5-#8 shown in Fig. 80 are shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths, and are also shifted downwards in the vertical direction at intervals of one wavelength.

[0350] In this way, 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 inverted symmetric manner.

[0351] For example, the third diagonal antenna group Rx#1 to #4 and the fourth diagonal antenna group Rx#5 to #8 of arrangement example 2 shown in FIG. 80 have a steeper inclination with respect to the horizontal direction compared to the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 of arrangement example 1 (e.g., FIG. 8), and therefore the aperture in the vertical direction can be made larger.

[0352] Also, 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 are 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 such that grating lobes may occur in the vertical direction. In Arrangement Example 2, for example, the first to fourth diagonal directions are not parallel but different from each other, so that the vertical and horizontal two-dimensional directions in which grating lobes occur are made different, thereby making it possible to suppress grating lobes in the vertical direction.

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

[0354] Here, the arrangement of the virtual receiving array may be expressed, for example, as shown in equation (16) based on the position (e.g., the position of the feed point) of transmitting antenna 106 constituting the transmitting array antenna and the position (e.g., the position of the feed point) of receiving antenna 202 constituting the receiving array antenna.

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

[0356] For example, from the arrangement of transmitting antennas Tx#1 to Tx#6 and receiving antennas Rx#1 to Rx#8 as shown in FIG. 80, the position coordinates of virtual antennas VA#1 to #48 constituting a virtual receiving array antenna are calculated from equation (16). For example, the position coordinates of virtual antennas VA#1 to #16 are calculated as follows: 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 )

[0357] Here, in the case of Fig. 80 and Fig. 81, D H and D. V In the following description, a case will be described in which 0.5λ is set for each of the wavelengths, but they may be set to values ​​of approximately 0.45λ to 0.8λ, for example. Here, 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-mentioned antenna arrangement is applied will be described.

[0359] For example, the direction estimation unit 213 performs code separation processing on the code-multiplexed signal transmitted from the transmission antenna 106 to obtain a received signal (or a code separation result) DeMul z ncm (f b_cfar ,f s_cfar ), the virtual receiving array correlation vector h(f b_cfar , f s_cfar) is generated and direction estimation processing is performed.

[0360] Virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is the number of transmitting antennas N Tx and the number of receiving antennas Na, Tx ×Na elements. The virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is used to perform a process of estimating the direction of the reflected wave signal from the target based on the phase difference between the receiving antennas 202.

[0361] For example, in the example of the MIMO antenna arrangement of the arrangement example 2, in the example of FIG. Tx = 6, Na = 8, the virtual receiving array correlation vector h(f b_cfar , f s_cfar ) includes 48 elements, each of which corresponds to the received signals at VA#1 to VA48 in the virtual receiving array arrangement shown in FIG.

[0362] The direction estimation unit 213 calculates, for example, a virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is used to perform horizontal and vertical direction estimation processing. Note that the subsequent operation of direction estimation section 213 is similar to the operation in the case of using Arrangement Example 1, and description thereof will be omitted.

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

[0364] Figure 82 shows the MIMO array layout of layout example 2 (D H = 0.5λ, D V= 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation unit 213. As an example, Fig. 82 plots the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0365] FIG. 82(a) is a diagram showing normalized power values ​​in two-dimensional directions, with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction, in a grayscale color map. FIG. 82(b) is a diagram showing the normalized power values ​​in a grayscale color map in the same way, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values, as shown in FIG. 82(a). FIG. 82(c) is a diagram showing the normalized power values ​​in a grayscale color map in the same way, with the horizontal axis being the vertical direction and the vertical axis being the normalized power values, as shown in FIG. 82(a). In FIG. 82, the normalized power values ​​may be shown, for example, as decibel values ​​(dB) normalized by peak power, and the same applies to plots of direction estimation results in other examples below.

[0366] Here, as shown in Fig. 80, the antenna spacing between the first diagonal antenna group Tx #1-#3 and the second diagonal antenna group Tx #4-#6 in the transmitting antenna 106 of Arrangement Example 2 is equal to or greater than one wavelength, which is an antenna spacing at which grating lobes may occur. Also, as shown in Fig. 80, the antenna spacing between the third diagonal antenna group Rx #1-#4 and the fourth diagonal antenna group Rx #5-#8 in the receiving antenna 202 of Arrangement Example 2 is equal to or greater than one wavelength, which is an antenna spacing at which grating lobes may occur.

[0367] Also, as shown in FIG. 81, in the virtual receiving array arrangement, the virtual antennas are arranged at intervals of one wavelength or more in both the horizontal and vertical directions, which is an interval at which grating lobes may occur.

[0368] In Arrangement Example 2, such grating lobes are suppressed by devising the arrangement of the transmitting antenna 106 and the receiving antenna 202. 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 of the target true value direction.

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

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

[0371] The virtual receiving array arrangement when the comparative arrangement 2a is used corresponds to VA#1 to #4, #9 to #12, and #17 to #20 in FIG.

[0372] Similarly, (a) of Fig. 84 shows an antenna arrangement (hereinafter referred to as "comparative arrangement 2b") in the case where the second diagonal antenna group Tx #4-#6 and the fourth diagonal antenna group Rx #5-#8 of Arrangement Example 2 shown in Fig. 80 are used for comparison with Arrangement Example 2. (b), (c) and (d) of Fig. 84 show direction estimation results using the beamformer method in the antenna arrangement shown in (a) of Fig. 84. (b), (c) and (d) of Fig. 84 plot the output of the direction-of-arrival estimation evaluation function value in the horizontal direction ±90 degree range and the vertical direction ±90 degree range when the target true value is set to 0 degree horizontally and 0 degree vertically, as in Fig. 82.

[0373] It should be noted that the virtual receiving array arrangements when the comparative arrangement 2b is used correspond to #29 to #32, #37 to #40, and #45 to #48 in FIG.

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

[0375] It should be noted that the virtual receiving array arrangements when the comparative arrangement 2c is used correspond to #5 to #8, #13 to #16, and #21 to #24 in FIG.

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

[0377] It should be noted that the virtual receiving array arrangements when the comparative arrangement 2d is used correspond to #25 to #28, #33 to #36, and #41 to #44 in FIG.

[0378] For example, a case will be described in which a first diagonal antenna group Tx #1 to #3 and a third diagonal antenna group Rx #1 to #4 are used as in comparative arrangement 2a shown in (a) of FIG. 83, and a case in which a second diagonal antenna group Tx #4 to #6 and a fourth diagonal antenna group Rx #5 to #8 are used as in comparative arrangement 2b shown in (a) of FIG. 84.

[0379] The arrangement direction of transmitting antennas Tx#1 to #3 (e.g., corresponding to the first diagonal antenna group) in comparison arrangement 2a shown in Fig. 83(a) is different from the arrangement direction of transmitting antennas Tx#4 to #6 (e.g., corresponding to the second diagonal antenna group) in comparison arrangement 2b shown in Fig. 84(a) and is not parallel. Also, the arrangement direction of receiving antennas Rx#1 to #4 (e.g., corresponding to the third diagonal antenna group) in comparison arrangement 2a is different from the arrangement direction of receiving antennas Rx#5 to #8 (e.g., corresponding to the fourth diagonal antenna group) in comparison arrangement 2b and is not parallel. For this reason, as shown in Fig. 83(b) and Fig. 84(b), comparison arrangement 2a and comparison arrangement 2b have the property that the horizontal and vertical two-dimensional angular directions in which grating lobes occur do not match and are shifted.

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

[0381] Therefore, in Arrangement Example 2 including the first to fourth diagonal antenna groups, the directions (two-dimensional angular directions) of the grating lobes occurring in comparison arrangement 2a including the first and third diagonal antenna groups and the grating lobes occurring in comparison arrangement 2b including the second and fourth diagonal antenna groups do not match and tend to be dispersed, as shown in Fig. 80. For this reason, in Arrangement Example 2, the peak level in the grating lobe direction tends to be suppressed compared to the peak in the target true value direction, as shown in Fig. 82(a).

[0382] Next, for example, a case where a first diagonal antenna group Tx #1 to #3 and a fourth diagonal antenna group Rx #5 to #8 are used as in comparative arrangement 2c shown in (a) of FIG. 85, and a case where a second diagonal antenna group Tx #4 to #6 and a third diagonal antenna group Rx #1 to #4 are used as in comparative arrangement 2d shown in (a) of FIG. 86 will be described.

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

[0384] On the other hand, as shown in FIG. 85(b) and FIG. 86(b), the angular directions of the main lobes corresponding to the target true values ​​(for example, horizontal 0 degrees, vertical 0 degrees) are the same in comparison arrangements 2c and 2d.

[0385] Therefore, in Arrangement Example 2 including the first to fourth diagonal antenna groups, the directions (two-dimensional angular directions) of the grating lobes occurring in comparison arrangement 2c including the first and fourth diagonal antenna groups and the grating lobes occurring in comparison arrangement 2d including the second and third diagonal antenna groups do not match and tend to be dispersed, as shown in Fig. 80. For this reason, in Arrangement Example 2, the peak level in the grating lobe direction tends to be suppressed compared to the peak in the target true value direction, as shown in Fig. 82(a).

[0386] Here, the virtual receiving array arrangement shown in FIG. 81 is the same arrangement as the virtual receiving array partially constituted by the virtual receiving arrays corresponding to the comparative arrangements 2a, 2b, 2c, and 2d. Therefore, in the direction estimation result by the virtual receiving array arrangement shown in FIG. 81, as shown in FIG. 82(a), the grating lobes in the direction different from the peak direction of the target true value direction are suppressed. In other words, in the arrangement example 2, the angular directions in which the grating lobes are generated are distributed in different directions by the multiple oblique antenna groups included in each of the transmitting antenna 106 and the receiving antenna 202. Therefore, for example, as shown in FIG. 82(b), in the arrangement example 2, the normalized power value of the grating lobe is easily suppressed to be lower than the normalized power value of the main lobe for the target true value. For example, in FIG. 82(b), it can be seen that the peak in the direction different from the peak direction of the target true value direction is suppressed to about -7.5 dB or less.

[0387] For example, in the antenna arrangement of Arrangement Example 2 shown in Fig. 80, the arrangement directions of the first and second oblique antenna groups are horizontally inverted and symmetrical, and the arrangement directions of the third and fourth oblique antenna groups are horizontally inverted and symmetrical. In this case, the virtual receiving array arrangements corresponding to Comparison Arrangements 2a and 2b are horizontally inverted and symmetrical. As a result, as shown in Fig. 83(b) and Fig. 84(b), for example, in Comparison Arrangements 2a and 2b, the horizontal and vertical two-dimensional directions in which grating lobes occur are horizontally inverted and symmetrical, and the deviation in the horizontal and vertical two-dimensional angular directions in which grating lobes occur becomes larger.

[0388] Similarly, for example, in the antenna arrangement of Arrangement Example 2 shown in Fig. 80, the arrangement directions of the first and second oblique antenna groups are horizontally inverted and symmetrical, and the arrangement directions of the third and fourth oblique antenna groups are horizontally inverted and symmetrical. In this case, the virtual receiving array arrangements corresponding to Comparison Arrangements 2c and 2d are horizontally inverted and symmetrical. As a result, for example, as shown in Fig. 85(b) and Fig. 86(b), in Comparison Arrangements c and d, the horizontal and vertical two-dimensional directions in which grating lobes occur are horizontally inverted and symmetrical, and 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 the first diagonal antenna group and the second diagonal antenna group are horizontally inverted and symmetrical and the arrangement directions of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inverted and symmetrical, 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 larger the horizontal and vertical two-dimensional angular spacing (or deviation) at which grating lobes occur is likely to become.

[0390] Furthermore, for example, if the arrangement directions of the first and second diagonal antenna groups are not horizontally inverted symmetrical, or if the arrangement directions of the third and fourth diagonal antenna groups are not horizontally inverted symmetrical, 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 larger the intervals in the horizontal and vertical two-dimensional angular directions at which grating lobes occur are likely to be.

[0391] The antenna arrangement in which the intervals in the horizontal and vertical two-dimensional angular directions in which such grating lobes occur are larger is more suitable, for example, when the number of antennas in the radar device 10 is smaller. For example, the fewer the number of antennas in the radar device 10, the wider the beam width of the main beam in direction estimation tends to be. For this reason, when the directions of the grating lobes to be suppressed are close to each other, the fewer the number of antennas in the radar device 10, the wider the beam width is, and the more likely the grating lobe power is to overlap and increase in the grating lobe power. For this reason, the fewer the number of antennas in the radar device 10, the more likely the grating lobe suppression performance is to deteriorate and the more likely the probability of false detection in the radar device 10 is to increase. Therefore, when the number of antennas in the radar device 10 is smaller, for example, by using Arrangement Example 2 in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inverted symmetrical and the arrangement directions of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inverted symmetrical, the overlap of the grating lobe power can be suppressed, and the grating lobe suppression performance can be improved.

[0392] As described above, under placement condition 2, the transmitting 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. Therefore, compared to placement condition 1, the vertical aperture length of the virtual receiving array can be further enlarged, and the vertical angle measurement accuracy or resolution of the radar device 10 can be improved.

[0393] In addition, in the arrangement condition 2, as described above, the directions in which the grating lobes occur are dispersed in a two-dimensional plane consisting of horizontal and vertical directions, thereby making it possible to suppress grating lobes in the vertical direction that occur when the inclinations of the first to fourth oblique directions are set steeper with respect to the horizontal direction. This makes it possible to further increase the aperture length in the vertical direction of the virtual receiving array, thereby improving the vertical angle measurement accuracy or resolution of the radar device 10.

[0394] For example, even if the second and fourth diagonal antenna groups of comparison arrangement 2b are arranged at arbitrary positions relative to the first and third diagonal antenna groups of comparison arrangement 2a, a similar grating lobe suppression effect can be obtained. Similarly, even if the second and third diagonal antenna groups of comparison arrangement 2d are arranged at arbitrary positions relative to the first and fourth diagonal antenna groups of comparison 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 transmitting antenna elements 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 it is possible to arrange receiving antenna elements with larger vertical sizes (for example, sizes greater than or equal to one wavelength).

[0397] Therefore, in arrangement example 2, the antenna elements of the transmitting antenna 106 and the receiving antenna 202 can be arranged in a line in a diagonal direction, making it possible to arrange antenna elements with a large vertical size (for example, antenna elements with a size of one wavelength or more).

[0398] In addition, even if the relative positional relationship between the transmitting antenna 106 and the receiving antenna 202 is different in the arrangement of the virtual receiving array, the same virtual receiving array arrangement can be configured. Therefore, the positional relationship between the transmitting antenna 106 and the receiving 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 arrangement configuration examples described below. For example, the distance between the transmitting antenna 106 and the receiving antenna 202 may be sufficiently wider than the antenna element size, or they may be arranged to be shifted in the horizontal direction so as not to overlap in the vertical direction.

[0399] As described above, in the radar device 10 in the second arrangement example, the transmitting 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. The receiving 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] This antenna arrangement configuration allows antenna elements of any lengthwise (for example, vertical) size to be applied in the MIMO array arrangement of the radar device 10, and also makes it possible to suppress grating lobes that occur in the virtual receiving array.

[0401] In addition, in Arrangement Example 2, as described above, a grating lobe suppression effect can be obtained by the difference in the arrangement directions of the first to fourth oblique antenna groups in the transmitting antenna 106 and the receiving antenna 202. For this reason, in Arrangement Example 2, for example, the element spacing of the transmitting antenna 106 and the receiving antenna 202 can be set arbitrarily. As a result, the aperture length of the virtual receiving array can be expanded according to the setting of at least one of the element spacing of the transmitting antenna 106 and the element spacing of the receiving antenna 202, and therefore the vertical and horizontal angle measurement accuracy and angle separation performance of the radar device 10 can be improved.

[0402] Therefore, according to Arrangement Example 2, it is possible to improve the angle measurement accuracy or resolution of the radar device 10 while suppressing the grating lobes.

[0403] In addition, in Arrangement Example 2, at least one of the transmitting antenna 106 and the receiving antenna 202 may further include an antenna element with respect to the antenna configuration shown in FIG. 80. In other words, each of the transmitting antenna 106 and the receiving antenna 202 of the radar device 10 may include at least the antenna elements arranged as shown in FIG. 80. In this case, for example, a relationship is established in which the virtual antenna is additively added to the virtual receiving array arrangement shown in Equation (16). For example, the addition of an antenna element to at least one of the transmitting antenna 106 and the receiving antenna 202 results in an arrangement in which another virtual antenna is added to the virtual receiving array arrangement shown in FIG. 80. Even in the case of an antenna arrangement including such Arrangement Example 2, the effect of Arrangement Example 2 described above is maintained, and the same effect as that of Arrangement Example 2 can be obtained.

[0404] For example, an antenna may be further added to the antenna configuration of Arrangement Example 2. The addition of an antenna makes it easier to further reduce the grating lobe or side lobe level suppressed by Arrangement Example 2 described above, thereby reducing erroneous detections during angle measurement in the radar device 10 and improving angle measurement performance. The addition of an antenna can be similarly applied to the subsequent arrangement examples or modified examples, and similar effects can be obtained.

[0405] Furthermore, in the MIMO array arrangement of arrangement example 2, an arrangement in which the horizontal direction and the vertical direction are swapped may be applied. In this case, the virtual receiving array arrangement is obtained by swapping the horizontal direction and the vertical direction, and angle separation performance is obtained by swapping the horizontal direction and the vertical direction. Note that the swapping of the horizontal direction and the vertical direction of the MIMO array arrangement can be similarly applied to the subsequent arrangement examples or modified examples, and the virtual receiving array arrangement in the subsequent arrangement examples is obtained by swapping the horizontal direction and the vertical direction.

[0406] Furthermore, in the MIMO antenna arrangement of Arrangement Example 2, the arrangement of the transmitting antenna 106 and the arrangement of the receiving antenna 202 may be interchanged. In this case, for example, the arrangement of the receiving antenna 202 shown in Arrangement Example 2 may be used as the arrangement of the transmitting antenna 106, and the arrangement of the transmitting antenna 106 shown in Arrangement Example 2 may be used as the arrangement of the receiving antenna 202. Even if the arrangement of the transmitting antenna 106 and the arrangement of the receiving antenna 202 are interchanged, the arrangement of the virtual receiving array will be the same, so that a similar effect can be obtained. Note that the interchange of the arrangement of the transmitting antenna 106 and the arrangement of the receiving antenna 202 can be similarly applied to the subsequent arrangement examples or modified examples.

[0407] <Layout example 2a> FIG. 87 is a diagram showing an example of arrangement (eg, an example of a MIMO antenna arrangement) of a transmitting antenna 106 (eg, represented as Tx) and a receiving antenna 202 (eg, represented as Rx) according to arrangement example 2a.

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

[0409] In Figure 87, N Tx The six transmitting antennas Tx#1 to #6 include a first group of diagonal antennas Tx#1 to #3 arranged in a first diagonal direction and a second group of diagonal antennas Tx#4 to #6 arranged in a second diagonal direction. In Fig. 87, the first and second diagonal directions are not parallel to each other but are different from each other.

[0410] In Fig. 87, Na=8 receiving antennas Rx#1-#8 include a third diagonal antenna group Rx#1-#4 arranged in a third diagonal direction and a fourth diagonal antenna group Rx#5-#8 arranged in a fourth diagonal direction. In Fig. 87, the third diagonal direction and the fourth diagonal direction are not parallel to each other but are different from each other.

[0411] From these, the antenna arrangement of arrangement example 2a shown in FIG.

[0412] In Arrangement Example 2a, the arrangement direction of the first diagonal antenna group and the arrangement direction of the fourth diagonal antenna group match and are parallel, as shown in Fig. 87. In Arrangement Example 2a, the arrangement direction of the second diagonal antenna group match and are parallel, as shown in Fig. 87. 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] In this way, in an antenna arrangement that satisfies arrangement condition 2, the first diagonal direction may be set to an inclination that matches the third diagonal direction or the fourth diagonal direction, and the second diagonal direction may be set to an inclination that matches the third diagonal direction or the fourth diagonal direction.

[0414] For example, the first diagonal antenna group Tx#1-#3 shown in Fig. 87 are arranged so as to be shifted horizontally by two wavelength intervals from left to right in the figure, and also shifted upward by two wavelength intervals in the vertical direction. The second diagonal antenna group Tx#4-#6 shown in Fig. 87 are arranged so as to be shifted horizontally by two wavelength intervals from left to right in the figure, and also shifted downward by two wavelength intervals in the vertical direction. In other words, the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 are arranged so as to be inverted symmetrically in the horizontal direction.

[0415] Here, the transmitting antenna 106 in Arrangement Example 1 (for example, FIG. 8) is arranged in the horizontal direction. On the other hand, the transmitting antenna 106 in Arrangement Example 2a is arranged in the diagonal direction as shown in FIG. 87. In other words, since the transmitting antenna 106 in Arrangement Example 2a is arranged two-dimensionally, horizontally and vertically, compared to Arrangement Example 1, Arrangement Example 2a can have a larger aperture in the vertical direction.

[0416] Also, for example, the third diagonal antenna group Rx#1-#4 shown in Fig. 87 are arranged so as to be shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths, and also shifted upwards in the vertical direction at intervals of 0.5 wavelengths. Also, the fourth diagonal antenna group Rx#5-#8 shown in Fig. 87 are arranged so as to be shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths, and also shifted upwards in the vertical direction at intervals of 0.5 wavelengths. In other words, the third diagonal antenna group Rx#1-#4 and the fourth diagonal antenna group Rx#5-#8 are arranged so as to be inverted symmetrically in the horizontal direction.

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

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

[0419] Figure 89 shows the MIMO array arrangement of arrangement example 2a (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation unit 213. As an example, Fig. 89 plots the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0420] FIG. 89(a) is a diagram showing normalized power values ​​in two-dimensional directions, with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction, in a grayscale color map. FIG. 89(b) is a diagram showing the normalized power values ​​in a grayscale color map in the same way, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values, as shown in FIG. 89(a). FIG. 89(c) is a diagram showing the normalized power values ​​in a grayscale color map in the same way, with the horizontal axis being the vertical direction and the vertical axis being the normalized power values, as shown in FIG. 89(a). In FIG. 89, the normalized power values ​​may be shown as decibel values ​​(dB) normalized by peak power, and the same applies to plots of direction estimation results in other examples below.

[0421] As shown in the virtual receiving array arrangement in Fig. 88, the virtual antennas are arranged at intervals including 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 the grating lobes are suppressed to about -6 dB or less in directions different from the peak direction of the target true value direction.

[0422] For example, in the antenna arrangement of arrangement example 2a shown in Fig. 87, the arrangement directions of the first and second diagonal antenna groups are horizontally inverted and symmetrical, and the arrangement directions of the third and fourth diagonal antenna groups are horizontally inverted and symmetrical, and the inclinations of the first to fourth diagonal directions are, for example, 45 degrees with respect to the horizontal direction. In this case, as shown in Fig. 89(a), the arrangement is such that the intervals in the horizontal and vertical two-dimensional angle directions where grating lobes occur are the widest.

[0423] An antenna arrangement in which the intervals in the horizontal and vertical two-dimensional angular directions in which such grating lobes occur are larger is more suitable, for example, when the number of antennas in the radar device 10 is smaller. For example, the fewer the number of antennas in the radar device 10, the wider the beam width of the main beam in direction estimation tends to be. For this reason, when the directions of the grating lobes to be suppressed are close to each other, the fewer the number of antennas in the radar device 10, the wider the beam width is, and the more likely the grating lobe power is to overlap and increase in the grating lobe power. For this reason, the fewer the number of antennas in the radar device 10, the more likely the grating lobe suppression performance is to deteriorate and the more likely the probability of false detection in the radar device 10 is to increase. Therefore, when the number of antennas in the radar device 10 is smaller, for example, by using Arrangement Example 2 in which the arrangement directions of the first diagonal antenna group and the second diagonal antenna group are horizontally inverted symmetrical and the arrangement directions of the third diagonal antenna group and the fourth diagonal antenna group are horizontally inverted symmetrical, the overlap of the grating lobe power can be suppressed, and the grating lobe suppression performance can be improved.

[0424] In Arrangement Example 2a, the arrangement direction of the first diagonal antenna group and the arrangement direction of the fourth diagonal antenna group are aligned and parallel to each other. In Arrangement Example 2a, the arrangement direction of the second diagonal antenna group and the arrangement direction of the third diagonal antenna group are aligned and parallel to each other. In this manner, in Arrangement Example 2a, the first diagonal direction is set to have an inclination that matches the third diagonal direction or the fourth diagonal direction, and the second diagonal direction is set to have an inclination that matches the third diagonal direction or the fourth diagonal direction, thereby achieving the same grating lobe suppression effect as in Arrangement Example 2.

[0425] In addition, in arrangement example 2a, as shown in FIG. 87, the antenna elements of the transmitting antenna 106 and the receiving antenna 202 can be arranged in a row in a diagonal direction, making it possible to arrange antenna elements with a large vertical size (for example, antenna elements with a size of one wavelength or more).

[0426] As described above, in Arrangement Example 2a, like Arrangement Example 2, antenna elements of any longitudinal (e.g., vertical) size can be applied in the MIMO array arrangement of the radar device 10, and grating lobes occurring in the virtual receiving array can be suppressed.

[0427] <Layout example 2b> In arrangement example 2b, for example, one of the first diagonal direction and the second diagonal direction that satisfy 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 not coincide with the third diagonal direction or the fourth diagonal direction but may be different.

[0428] FIG. 90 is a diagram showing an example of arrangement (eg, an example of a MIMO antenna arrangement) of a transmitting antenna 106 (eg, represented as Tx) and a receiving antenna 202 (eg, represented as Rx) according to arrangement example 2b.

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

[0430] In Figure 90, N Tx The six transmitting antennas Tx#1 to #6 include a first group of diagonal antennas Tx#1 to #3 arranged in a first diagonal direction and a second group of diagonal antennas Tx#4 to #6 arranged in a second diagonal direction. In Fig. 90, the first and second diagonal directions are not parallel but different from each other.

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

[0432] From these, the antenna arrangement of arrangement example 2b shown in FIG.

[0433] In arrangement example 2b, the arrangement direction of the first diagonal antenna group and the arrangement direction of the fourth diagonal antenna group do not match but are different directions, as shown in Fig. 90. On the other hand, the arrangement direction of the second diagonal antenna group and the arrangement direction of the third diagonal antenna group match but are parallel, as shown in Fig. 90. 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] In this way, even if one of the first diagonal direction and the second diagonal direction is set to have an inclination that matches the third diagonal direction or the fourth diagonal direction, the arrangement condition 2 is satisfied.

[0435] For example, the first diagonal antenna group Tx#1-#3 shown in Fig. 90 are arranged so as to be shifted horizontally by two wavelength intervals from left to right in the figure, and also shifted upward by two wavelength intervals in the vertical direction. The second diagonal antenna group Tx#4-#6 shown in Fig. 90 are arranged so as to be shifted horizontally by two wavelength intervals from left to right in the figure, and also shifted downward by two wavelength intervals in the vertical direction. In other words, the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 are arranged so as to be inverted symmetrically in the horizontal direction.

[0436] Here, the transmitting antenna 106 in Arrangement Example 1 (for example, FIG. 8) is arranged in the horizontal direction. On the other hand, the transmitting antenna 106 in Arrangement Example 2b is arranged in the diagonal direction as shown in FIG. 90. In other words, since the transmitting antenna 106 in Arrangement Example 2b is arranged two-dimensionally, horizontally and vertically, compared to Arrangement Example 1, Arrangement Example 2b can have a larger aperture in the vertical direction.

[0437] Also, for example, the third diagonal antenna group Rx#1-#4 shown in Fig. 90 are arranged so as to be shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths, and also shifted upwards in the vertical direction at intervals of 0.5 wavelengths. Also, the fourth diagonal antenna group Rx#5-#8 shown in Fig. 90 are arranged so as to be shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths, and also shifted upwards in the vertical direction at intervals of 1 wavelength. In other words, the third diagonal antenna group Rx#1-#4 and the fourth diagonal antenna group Rx#5-#8 are arranged not inverted symmetrically in the horizontal direction.

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

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

[0440] FIG. 92 shows the MIMO array arrangement of arrangement example 2b (D H = 0.5λ, D V = 0.5λ) and uses a beamformer method as the arrival direction estimation algorithm of direction estimation unit 213. As an example, Fig. 92 plots the output of the arrival direction estimation evaluation function value in a horizontal range of ±90 degrees and a vertical range of ±90 degrees when the target true value is 0 degrees horizontally and 0 degrees vertically.

[0441] FIG. 92(a) is a diagram showing normalized power values ​​in two-dimensional directions, with the horizontal axis being the horizontal direction and the vertical axis being the vertical direction, in a grayscale color map. FIG. 92(b) is a diagram showing the normalized power values ​​in a grayscale color map in the same way, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values, as shown in FIG. 92(a). FIG. 92(c) is a diagram showing the normalized power values ​​in a grayscale color map in the same way, with the horizontal axis being the vertical direction and the vertical axis being the normalized power values, as shown in FIG. 92(a). In FIG. 92, the normalized power values ​​may be shown as decibel values ​​(dB) normalized by peak power, and the same applies to plots of direction estimation results in other examples below.

[0442] As shown in the virtual receiving array arrangement in Fig. 91, the virtual antennas are arranged at 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. 92, it can be seen that the grating lobes are suppressed to about -4 dB or less in directions 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 but are different directions, but the arrangement direction of the second diagonal antenna group matches and is parallel to the arrangement direction of the third diagonal antenna group. In this way, even if either the first diagonal direction or 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] In addition, in arrangement example 2b, as shown in FIG. 90, the antenna elements of the transmitting antenna 106 and the receiving antenna 202 can be arranged in a row in a diagonal direction, making it possible to arrange antenna elements with a large vertical size (for example, antenna elements with a size of one wavelength or more).

[0445] As described above, in Arrangement Example 2b, like Arrangement Example 2, antenna elements of any longitudinal (e.g., vertical) size can be applied in the MIMO array arrangement of the radar device 10, and grating lobes occurring in the virtual receiving array can be suppressed.

[0446] A modification of Arrangement Example 2 will be described below.

[0447] For example, the modified examples 1 to 4, 6, and 7 of the arrangement example 1 may be applied to the receiving antenna of the arrangement example 2 (or the arrangement examples 2a and 2b). Even when the modified examples 1 to 4, 6, and 7 of the arrangement example 1 are applied to the arrangement example 2, the same effect as that of the arrangement example 2 can be obtained. For example, the "arrangement example 1" in the explanation of the modified examples 1 to 4, 6, and 7 of the arrangement example 1 may be replaced with "arrangement example 2", and further, the "first diagonal antenna group" and the "second diagonal antenna group" of the arrangement example 1 may be replaced with the "third diagonal antenna group" and the "fourth diagonal antenna group" of the arrangement example 2, respectively. As a result, the same effect as that of the modified examples 1 to 4, 6, and 7 of the arrangement example 1 can be obtained in the arrangement example 2. Note that the explanation of the application of the modified examples 1 to 4, 6, and 7 of the arrangement example 1 to the arrangement example 2 is omitted.

[0448] The following describes additional parts when the same contents as those of Modifications 1 to 4, 6, and 7 of Arrangement Example 1 are applied to the “first diagonal antenna group” and the “second diagonal antenna group” included in the transmitting antenna 106 of Arrangement Example 2.

[0449] The following describes additional portions of Modifications 1 to 4, 6, and 7 of Arrangement Example 2, which correspond to Modifications 1 to 4, 6, and 7 of Arrangement Example 1.

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

[0451] For example, in the case of the arrangement example 2, as shown in FIG. 80, the minimum interval between the first diagonal antenna group and the second diagonal antenna group (for example, the interval between Tx#3 and Tx#4) is N a In the first modification of the second arrangement example, the minimum interval between the first diagonal antenna group and the second diagonal antenna group (for example, the interval between Tx#3 and Tx#4) is set to be smaller than the horizontal aperture length of the receiving antennas 202 (for example, the interval between Rx#4 and Rx#8). a The horizontal aperture length may be set to be wider than the horizontal aperture length of each receiving antenna 202. Even in this case, the same effect as in Arrangement Example 2 can be obtained.

[0452] Furthermore, by widening the minimum interval between the first and second oblique antenna groups, the peak in the target true value direction in the horizontal direction becomes sharper, which improves the horizontal angle measurement accuracy or estimation accuracy of the radar device 10. Note that in the first modification of Arrangement Example 2, as in the first modification of Arrangement Example 1, the side lobe level to the side (horizontal direction) of the peak in the target true value direction may increase, so that the interval (e.g., minimum interval) between the first and second oblique antenna groups may be set within a suitable range depending on requirements such as the target to be detected by the radar device 10.

[0453] [Modification 2 of Arrangement Example 2] In Variation 2 of Arrangement Example 2, for example, the interval (for example, the minimum interval) between the first diagonal antenna group and the second diagonal antenna group may be closer than in Arrangement Example 2 (or Arrangement Examples 2a and 2b). Also, in Variation 2 of Arrangement Example 2, for example, some 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 interval between the first diagonal antenna group Tx#1 to #3 and the second diagonal antenna group Tx#4 to #6 (the interval between Tx#3 and Tx#4) is N a This is narrower than the horizontal aperture length of each receiving antenna 202 (for example, the distance between Rx#4 and Rx#8).

[0455] In the second modification of the second arrangement example, for example, the first diagonal antenna group Tx#1 to #3 and the second diagonal antenna group Tx#4 to #6 may be arranged so that the minimum interval (the interval between Tx#3 and Tx#4) is further reduced.

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

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

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

[0459] [Modification 4 of Arrangement Example 2] For example, in the arrangement example 2 shown in Fig. 80, the first diagonal antenna group Tx #1 to #3 and the second diagonal antenna group Tx #4 to #6 are arranged symmetrically in the horizontal direction, but 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 symmetrically in the horizontal direction. For example, the first diagonal direction and the second diagonal direction may be different directions, not parallel. This provides the same effect as the arrangement example 2.

[0460] For example, a) the first diagonal antenna group and the second diagonal antenna group may be asymmetrically inclined, or different antenna intervals may be set in each of the horizontal and vertical directions.

[0461] Also, for example, b) the first diagonal antenna group and the second diagonal antenna group may be arranged such that their positions are shifted in the vertical direction.

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

[0463] Furthermore, for example, the arrangement of the first diagonal antenna group and the second diagonal antenna group may be a combination of two or three of the above-mentioned a) arrangement in which the first diagonal antenna group and the second diagonal antenna group have an asymmetric inclination, b) arrangement in which the first diagonal antenna group and the second diagonal antenna group each include a different number of antennas, and c) arrangement in which the positions of the first diagonal antenna group and the second diagonal antenna group are shifted in the vertical direction.

[0464] As a result, the same effects as those of Arrangement Example 2 and Modification 4 of Arrangement Example 1 can be obtained.

[0465] In addition, the modified arrangement of the first and second diagonal antenna groups included in the transmitting antenna 106 may be combined with the modified arrangement of the third and fourth diagonal antenna groups included in the receiving antenna 202.

[0466] 93 shows an example (for example, called "Arrangement Example 2-4a") in which the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 are arranged with symmetric inclinations in the horizontal direction, and the third diagonal antenna group Rx#1-#4 and the fourth diagonal antenna group Rx#5-#8 are arranged asymmetrically in the horizontal direction. Even in the case of Arrangement Example 2-4a, the same effect as in Arrangement Example 2 can be obtained.

[0467] 94 shows an example of an arrangement (for example, called "arrangement example 2-4b") in which the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 are arranged with asymmetric inclinations in the horizontal direction, and the third diagonal antenna group Rx#1-#4 and the fourth diagonal antenna group Rx#5-#8 are arranged symmetrically in the horizontal direction. Even in the case of arrangement example 2-4b, the same effect as in arrangement example 2 can be obtained.

[0468] 95 shows an example (for example, called "Arrangement Example 2-4c") in which the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 are arranged with asymmetric inclinations in the horizontal direction, and the third diagonal antenna group Rx#1-#4 and the fourth diagonal antenna group Rx#5-#8 are arranged with asymmetric inclinations in the horizontal direction. Even in the case of Arrangement Example 2-4c, the same effect as in Arrangement Example 2 can be obtained.

[0469] In addition, in the arrangement condition 2, either the first diagonal direction or the second diagonal direction may be arranged horizontally. In addition, in the arrangement condition 2, either the third diagonal direction or the fourth diagonal direction may be arranged horizontally.

[0470] For example, Fig. 96 shows an example (for example, referred to as "Arrangement Example 2-4d") in which the first diagonal antenna group Tx#1-#3 is arranged in a diagonal direction and the second diagonal antenna group Tx#4-#6 is arranged in a horizontal direction. In Fig. 96, for example, the arrangement of the third diagonal antenna group Rx#1-#4 and the fourth diagonal antenna group Rx#5-#8 is arranged symmetrically in the horizontal direction. In this way, even if either the first diagonal direction or the second diagonal direction is arranged in the horizontal direction, the same effect as in Arrangement Example 2 can be obtained.

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

[0472] For example, 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 arranged with uneven antenna spacing, which can also provide the same effect as in Arrangement Example 2.

[0473] [Modification 7 of Arrangement Example 2] In the seventh modification of the second arrangement, for example, the multi-stage configuration of the antenna arrangement described in the second arrangement and the first to fourth and sixth modifications of the second arrangement may be applied.

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

[0475] Even in the case of a multi-stage configuration, the effects of Arrangement Example 2 described above can be maintained. Furthermore, for example, a multi-stage configuration in the horizontal direction increases the aperture length of the virtual receiving array in the horizontal direction, thereby improving the horizontal angle measurement accuracy or resolution of the radar device 10. Furthermore, for example, a multi-stage configuration in the vertical direction increases the aperture length of the virtual receiving array in the vertical direction, thereby improving the vertical angle measurement accuracy or resolution of the radar device 10. Furthermore, for example, a multi-stage configuration in both the vertical and horizontal directions increases the aperture length of the virtual receiving array in the vertical and horizontal directions, thereby improving the vertical and horizontal angle measurement accuracy or resolution of the radar device 10.

[0476] In the case of a multi-stage configuration, a common arrangement of transmitting antennas Tx or receiving antennas Rx may be configured in multiple stages in at least one of the vertical and horizontal directions, or different arrangements of transmitting antennas Tx or receiving antennas 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 above-described multi-stage configuration. For example, the multiple transmitting antennas 106 may include a long range (LR) antenna element and a short range (SR) antenna element.

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

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

[0480] In this way, when an antenna for LR and an antenna for SR are used for the transmitting antenna 106, for example, an antenna for SR (for example, an antenna having a characteristic of having a wide viewing angle) may be applied to the receiving antenna 202. This makes it possible to accommodate the detection ranges of both the LR and SR modes while maintaining the effect of Arrangement Example 2.

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

[0482] Next, a modification specific to the arrangement condition 2 will be described.

[0483] [Modification of placement condition 2] In the arrangement example 2 and the modified example of the arrangement example 2, for example, the inclination of each of the transmitting antenna 106 and the receiving antenna 202 in the diagonal direction is set to a basic interval D H In the vertical direction, the basic interval D V In the above, the case where the frequency is set to an integer multiple of .

[0484] That is, N Tx In the transmitting antennas 106, the first diagonal antenna group and the second diagonal antenna group are arranged in different diagonal directions. The first diagonal antenna group is arranged in a horizontal direction with a distance of dTH1×D H and shifts vertically at intervals of dTV1×D VThe second diagonal antenna group is arranged in a diagonal direction with a shift interval of dTH2×D H Shifts vertically at intervals of dTV2×D V The pixels are arranged diagonally, shifting at intervals of .

[0485] In addition, among the Na receiving antennas 202, the third diagonal antenna group and the fourth diagonal antenna group are arranged in different diagonal directions. In addition, the third diagonal antenna group is arranged in a horizontal direction with a diagonal angle of dRH1×D H and shifts vertically at intervals of dRV1×D V The fourth diagonal antenna group is arranged in a diagonal direction with a shift of dRH2×D H and shifts vertically at intervals of dRV2×D V The pixels are arranged diagonally, shifting at intervals of .

[0486] Here, dTH1 and dTV1 are integers equal to or greater than 1, and dTH2 and dTV2 are integers equal to or greater than 1. In addition, dRH1 and dRV1 are integers equal to or greater than 1, and dRH2 and dRV2 are integers equal to or greater than 1.

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

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

[0489] In the arrangement example 2 and the modified example of the arrangement example 2, the inclination of the transmitting antenna 106 and the receiving antenna 202 in the diagonal direction is the basic interval D HThe vertical spacing is set to an integer multiple of the basic spacing D V It is not limited to being set to an integer multiple of D V , D H Even in this arrangement, the arrangement condition 2 is satisfied, and the same effect as in the arrangement example 2 can be obtained.

[0490] [Minimum antenna configuration for layout condition 2 and layout example with a small number of antennas] The following describes a minimum antenna configuration that satisfies Arrangement Condition Example 2, and an arrangement example in which the number of antennas that satisfies Arrangement Condition 2 is small. Note that the same effect can be obtained by modifying the antenna arrangement described below in accordance with the modified example of Arrangement Example 2 described above.

[0491] The minimum number of antennas in placement condition 2 is, for example, the number of transmitting antennas N Tx = 3, and the number of receiving antennas Na = 3. In other words, the total number of antennas in the first diagonal antenna group and the second diagonal antenna group is three, and the total number of antennas in the third diagonal antenna group and the fourth diagonal antenna group is three.

[0492] Figure 97 shows the minimum number of antennas for placement condition 2 (number of transmitting antennas N Tx FIG. 97(a) shows an example of a MIMO antenna arrangement, and FIG. 97(b) shows an example of a virtual receiving array arrangement configured by the MIMO antenna arrangement shown in FIG. 97(a). In FIG. 97, the scales of the horizontal and vertical axes are, for example, D H , D V Let us assume that.

[0493] In Fig. 97, 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#2 and Rx#3.

[0494] 98 to 101 show examples of antenna arrangements when the number of antennas that satisfy arrangement condition 2 is small. (a) of Fig. 98 to 101 shows an example of a MIMO antenna arrangement, and (b) of Fig. 98 to 101 shows an example of a virtual receiving array arrangement configured by the MIMO antenna arrangement shown in (a) of Fig. 98 to 101. In Fig. 98 to 101, the scales of the horizontal and vertical axes are, for example, D H , D V Let us assume that.

[0495] For example, FIG. 98 and FIG. 99 show the case where the number of transmitting antennas is N Tx 98 and 99 show examples of antenna arrangements when the number of receiving antennas Na=3 and the number of receiving antennas Na=4. In Fig. 98 and Fig. 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 FIG. 98, even if the vertical size of the transmitting antenna 106 is large, the receiving antennas 202 are arranged on both sides of the transmitting antenna 106, so that the antenna mounting area can be reduced.

[0497] Also, for example, in the example antenna arrangement shown in FIG. 99, even if the vertical size of the transmitting antenna 106 is large, the transmitting antenna 106 is arranged on both sides of the receiving antenna 202, so that the mounting area of ​​the antenna can be reduced.

[0498] 100 and 101 show an example of a case where the number of transmitting antennas is N Tx 100 and 101 show examples of antenna arrangements when the number of receiving antennas is 4 and the number of receiving antennas Na=4. In Fig. 100 and Fig. 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 if the vertical size of the transmitting antenna 106 is large, the receiving antennas 202 are arranged on both sides of the transmitting antenna 106, so that the antenna mounting area can be reduced.

[0500] An embodiment of the present disclosure has been described above.

[0501] In the embodiment of the present disclosure, a case has been described in which the arrangement directions (e.g., diagonal directions) of the receiving antenna 202 are two different directions in arrangement condition 1 (e.g., FIG. 8), but the arrangement directions of the receiving antenna 202 may be three or more different directions. Similarly, a case has been described in which the arrangement directions (e.g., diagonal directions) of the transmitting antenna 106 and the receiving antenna 202 are two different directions in arrangement condition 2 (e.g., FIG. 80), but the 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 directions in which grating lobes occur corresponding to the respective arrangement directions tend to be dispersed, so that grating lobes can be suppressed in the same manner as described above.

[0502] Furthermore, the configuration of the radar device according to an embodiment of the present disclosure is not limited to the configuration shown in Fig. 6. For example, the radar device does not need to include the CFAR unit 211.

[0503] In addition, the number of transmitting antennas in the antenna arrangement described in the embodiment of the present disclosure, N Tx , the number of receiving antennas Na, or the antenna spacing are merely examples, and other different values ​​may be used.

[0504] Also, at least two of the modified examples of Arrangement Example 1 described in the embodiment of the present disclosure may be combined and implemented. Similarly, at least two of the modified examples of Arrangement Example 2 may be combined and implemented. For example, the settings of the number of antennas, the inclination, the element spacing, or the spacing between the oblique antenna groups of the first and second oblique antenna groups in Arrangement Example 1 and the first to fourth oblique antenna groups in Arrangement Example 2 may be determined by combining at least two of the modified examples 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 disposed separately in physically separate locations. Also, in a radar receiver according to an embodiment of the present disclosure, the direction estimator and other components may be disposed separately in physically separate locations.

[0506] Although not shown, the radar device according to an embodiment of the present disclosure includes, for example, a central processing unit (CPU), a storage medium such as a read only memory (ROM) storing a control program, and a working memory such as a random access memory (RAM). In this case, the functions of each of the above-mentioned units are realized by the CPU executing the control program. However, the hardware configuration of the radar device is not limited to this example. For example, each functional unit of the radar device may be realized as an integrated circuit (IC). Each functional unit may be individually implemented as a single chip, or may be implemented as a single chip that includes some or all of the functional units.

[0507] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or amended examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure. In addition, the components in the above embodiments may be arbitrarily combined within the scope of the disclosure.

[0508] In addition, the notation "... part" in the above-mentioned 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 as an example configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

[0510] Moreover, 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 have input terminals and output terminals. These may be individually integrated into one chip, or may be integrated into one chip that includes some or all of them. Here, the term LSI is used, but depending on the degree of integration, it may also be called an IC, a system LSI, a super LSI, or an ultra LSI.

[0511] The method of integration is not limited to LSI, but may be realized using a dedicated circuit or a general-purpose processor. A field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections or settings of circuit cells inside the LSI may also be used.

[0512] Furthermore, if a new integrated circuit technology that can replace LSI appears due to the progress of semiconductor technology or a derivative technology, it is possible to integrate the functional blocks using that technology. The application of biotechnology is also a possibility.

[0513] <Summary of this disclosure> A radar device according to one embodiment of the present disclosure includes a transmitting circuit that transmits a transmission signal using a plurality of transmitting antennas, and a receiving circuit that receives a reflected wave signal of the transmission signal reflected by an object using a plurality of receiving antennas, wherein either the plurality of transmitting antennas or the plurality of receiving 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 transmitting antennas or the plurality of receiving antennas includes a third antenna group arranged in a third direction different from each of the first direction and the second direction, with adjacent antennas spaced apart by a distance of at least one wavelength of the transmission signal.

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

[0515] In one 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 perpendicular to the direction of gravity.

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

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

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

[0519] In an embodiment of the present disclosure, 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.

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

[0521] In an embodiment of the present disclosure, adjacent antennas in each of the third antenna group, the first antenna group, and the second antenna group are spaced equally apart.

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

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

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

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

[0526] In one embodiment of the present disclosure, the remaining 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 remaining 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 shared antennas.

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

[0531] A radar device according to one embodiment of the present disclosure includes a transmitting circuit that transmits a transmission signal using a plurality of transmitting antennas, and a receiving circuit that receives a reflected wave signal of the transmission signal reflected by an object using a plurality of receiving antennas, wherein one of the plurality of transmitting antennas or the plurality of receiving 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 transmitting antennas or the plurality of receiving antennas includes a third antenna group arranged in a third direction, the spacing between adjacent antennas being one or more wavelengths of the transmission signal, and a fourth antenna group arranged in a fourth direction different from the third direction, the spacing between adjacent antennas being one or more wavelengths of the transmission signal, and 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 for a radar device that detects a wide angle range. [Explanation of symbols]

[0533] 10 Radar Equipment 100 Radar transmitter 101 Radar transmission signal generator 102 Modulation signal generator 103 VCO 104 Code generator 105 Phase Rotation Unit 106 Transmitting Antenna 200 Radar receiver 201 Antenna system processing unit 202 Receiving antenna 203 Receiving Radio Unit 204 Mixer section 205 LPF 206 Signal Processing Section 207 AD conversion section 208 Beat Frequency Analysis Section 209 Output switching unit 210 Doppler analysis unit 211 CFAR Department 212 Code demultiplexer 213 Direction estimation part

Claims

1. A transmission circuit that transmits a transmission signal using a plurality of transmission antennas; a receiving circuit that receives a reflected wave signal resulting from the transmission signal being reflected by an object using a plurality of receiving antennas; Equipped with Either the plurality of transmitting antennas or the plurality of receiving antennas A first antenna group including a plurality of first antennas arranged parallel to each other in a first direction; a second antenna group arranged parallel to each other in a second direction different from the first direction; It is divided into The remaining one of the plurality of transmitting antennas or the plurality of receiving antennas is 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 first antenna groups has a first interval between adjacent antennas in the first direction, In each of the plurality of second antenna groups, adjacent antennas are spaced apart by the first distance in the second direction; each of the third antenna groups has a second interval between adjacent antennas in the third direction that is wider than the first interval; the first interval is equal to or greater than 0.5 wavelengths of the transmission signal; the second interval is an interval of one or more wavelengths of the transmission signal; Radar equipment.

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 direction of the vehicle and a direction perpendicular to the straight 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 perpendicular 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. a minimum interval between the first antenna group and the second antenna group is greater than an 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 shared antennas; The radar device according to claim 1 .

7. 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; The radar device according to claim 1 .

8. The spacing between adjacent antennas in the third antenna group in the horizontal direction is dT×D H and The interval between adjacent antennas included in the first antenna group in the horizontal direction is dRH 1 ×D H and The spacing between adjacent antennas in the first antenna group in the vertical direction is dRV×D V and The interval between adjacent antennas included in the second antenna group in the horizontal direction is dRH 2 ×D H and The spacing between adjacent antennas in the second antenna group in the vertical direction is dRV×D V and D H and D V is a value within a range of 0.45 to 0.8 times the wavelength of the transmission signal, The dT is a value equal to or greater than 2, and the dRH 1 and the dRH 2 each of which is equal to or greater than 1; 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, adjacent antennas are spaced equally apart. 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 interval between adjacent antennas includes one or more unequal intervals. The radar device according to claim 1 .

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

12. Either the plurality of transmitting antennas or the plurality of receiving antennas includes a plurality of the first antenna groups and a plurality of the second antenna groups. 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 a vertical direction which is a height direction of the vehicle, and a horizontal direction which is a straight direction of the vehicle and a direction perpendicular to the straight direction of the vehicle, All of the plurality of transmitting antennas are disposed 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 a vertical direction which is a height direction of the vehicle, and a horizontal direction which is a straight direction of the vehicle and a direction perpendicular to the straight direction of the vehicle, All of the plurality of receiving antennas are disposed at different positions with respect to the horizontal direction. The radar device according to claim 1 .

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