Radar system

Abstract

To provide a radar system capable of improving the angle measurement accuracy or resolution.SOLUTION: The radar system includes: a transmission circuit that transmits transmission signals using multiple transmission antennas; and a receiving circuit that receives reflected wave signals that are transmission signals reflected by an object using multiple receiving antennas. Either multiple transmission antennas or multiple receiving antennas include a first antenna group arranged in a first direction and a second antenna group arranged in a second direction different from the first direction. The remaining one of multiple transmission antennas or multiple receiving antennas includes: a third antenna group arranged in a third direction with the spacing between adjacent antennas being at least one wavelength of the transmission signal, and a fourth antenna group arranged in a fourth direction different from the third direction, with the spacing between adjacent antennas being at least one wavelength of the transmission signal. The third direction is the same as the first direction, and the fourth direction is different from the second 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 short-wavelength radar transmission signals, including microwaves and millimeter waves, which can provide high resolution, have been studied. Furthermore, to improve outdoor safety, there is a demand for the development of radar devices that can detect small objects, such as pedestrians, over a wide angle range (e.g., called wide-angle radar devices).

[0003] A radar device having a wide detection range may be configured to receive reflected waves from a target (or object) using an array antenna composed of multiple antennas (also called antenna elements), and estimate the direction (or angle of arrival) of the reflected waves based on the received phase difference relative to the element spacing (antenna spacing) (Direction of Arrival (DOA) estimation).

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

[0005] Furthermore, a radar device has been proposed that includes, for example, multiple antennas (array antennas) on the transmitting side as well as the receiving side, and performs beam scanning by signal processing using the transmitting and receiving array antennas (sometimes called MIMO (Multiple Input Multiple Output) radar) (see, for example, 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., "Automotive 3D Scanning Millimeter-Wave Radar," Fujitsu Ten Technical Report, Vol. 30, No. 1, 2012. [Non-patent document 3] M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 [Non-patent document 4] Direction-of-arrival estimation using signal subspace modeling Cadzow, 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 radar devices (for example, MIMO radars).

[0009] Non-limiting examples of the present disclosure contribute to providing a radar device that can improve 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 both the first direction and the second direction, with a spacing between adjacent antennas being equal to or greater than one wavelength of the transmission signal.

[0011] 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. [Effects 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 explanation of the drawings]

[0014] [Figure 1] Diagram showing an example of MIMO antenna placement [Figure 2] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 3] A diagram showing an example of an antenna with a subarray configuration. [Figure 4] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 5] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 6] Block diagram showing an example of the configuration of a radar device [Figure 7] FIG. 1 shows an example of a transmitted signal and a reflected wave signal when a chirp pulse is used. [Figure 8] FIG. 1 is a diagram showing an example of arrangement of MIMO antennas according to 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. 10 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 a MIMO antenna arrangement according to comparative arrangement 1. [Figure 12] FIG. 10 is a diagram showing an example of a direction estimation result according to comparative arrangement 1. [Figure 13] FIG. 10 is a diagram showing an example of MIMO antenna arrangement according to comparative arrangement 2. [Figure 14] FIG. 10 is a diagram showing an example of a direction estimation result according to comparative arrangement 2. [Figure 15] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a first modification of the first arrangement example. [Figure 16] FIG. 10 is a diagram showing an example of the arrangement of a virtual receiving array according to a first modification of the first arrangement example. [Figure 17] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 1 of Arrangement Example 1. [Figure 18] FIG. 10 is a diagram showing another example of the arrangement of MIMO antennas according to Modification 1 of Arrangement Example 1. [Figure 19] FIG. 10 is a diagram showing another example of the arrangement of the virtual receiving array according to Modification 1 of Arrangement Example 1. [Figure 20] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a first modification of the first arrangement example. [Figure 21] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a second modification of the first arrangement example. [Figure 22]FIG. 10 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. 10 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. 10 is a diagram showing an example of a direction estimation result according to Modification 2 of Arrangement Example 1. [Figure 25] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 2 of Arrangement Example 1. [Figure 26] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a third modification of arrangement example 1. [Figure 27] FIG. 10 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. 10 is a diagram showing an example of a direction estimation result according to Modification 3 of Arrangement Example 1. [Figure 29] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fourth modification of arrangement example 1. [Figure 30] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fourth modification of arrangement example 1. [Figure 31] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fourth modification of arrangement example 1. [Figure 32] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fourth modification of arrangement example 1. [Figure 33] FIG. 10 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 34] FIG. 10 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 35] FIG. 10 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 36] FIG. 10 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. 10 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Figure 38] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Figure 39] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Figure 40] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 4 of Arrangement Example 1. [Figure 41]FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fifth modification of arrangement example 1. [Figure 42] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fifth modification of arrangement example 1. [Figure 43] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fifth modification of arrangement example 1. [Figure 44] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fifth modification of arrangement example 1. [Figure 45] FIG. 10 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. 10 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. 10 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. 10 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. 10 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 50] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 51] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 52] FIG. 10 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 53] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fifth modification of arrangement example 1. [Figure 54] FIG. 10 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. 10 is a diagram showing an example of a direction estimation result according to Modification 5 of Arrangement Example 1. [Figure 56] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a sixth modification of arrangement example 1. [Figure 57] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a sixth modification of arrangement example 1. [Figure 58] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a sixth modification of arrangement example 1. [Figure 59] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a seventh modification of arrangement example 1. [Figure 60] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a seventh modification of arrangement example 1. [Figure 61] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a seventh modification of arrangement example 1. [Figure 62] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a seventh modification of arrangement example 1. [Figure 63] FIG. 10 shows an example of the arrangement of a virtual receiving array according to a seventh modification of the first arrangement example. [Figure 64] FIG. 10 shows an example of the arrangement of a virtual receiving array according to a seventh modification of the first arrangement example. [Figure 65] FIG. 10 shows an example of the arrangement of a virtual receiving array according to a seventh modification of the first arrangement example. [Figure 66] FIG. 10 shows 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 arrangement of MIMO antennas according to Modification 8 of Arrangement Example 1. [Figure 72] FIG. 13 shows an example of the arrangement of a virtual receiving array according to Modification 8 of Arrangement Example 1. [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. 10 is a diagram showing an example of MIMO antenna arrangement according to Arrangement Example 2. [Figure 81] FIG. 10 is a diagram showing an example of the arrangement of a virtual receiving array according to Arrangement Example 2. [Figure 82] FIG. 10 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 a MIMO antenna arrangement and an example of a direction estimation result according to comparative arrangement 2a. [Figure 84] FIG. 10 is a diagram showing an example of an arrangement of MIMO antennas according to comparative arrangement 2b and an example of a direction estimation result. [Figure 85] FIG. 2 is a diagram showing an example of a MIMO antenna arrangement and an example of a direction estimation result according to comparative arrangement 2c. [Figure 86] FIG. 10 is a diagram showing an example of an arrangement of MIMO antennas according to comparative arrangement 2d and an example of a direction estimation result. [Figure 87] FIG. 10 is a diagram showing an example of MIMO antenna arrangement according to arrangement example 2a. [Figure 88] FIG. 10 is a diagram showing an example of the arrangement of a virtual receiving array according to arrangement example 2a. [Figure 89] FIG. 10 is a diagram showing an example of a direction estimation result according to arrangement example 2a. [Figure 90] FIG. 10 is a diagram showing an example of MIMO antenna arrangement according to arrangement example 2b. [Figure 91] FIG. 10 is a diagram showing an example of the arrangement of a virtual receiving array according to Arrangement Example 2b. [Figure 92] FIG. 10 is a diagram showing an example of a direction estimation result according to arrangement example 2b. [Figure 93] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fourth modification of the second arrangement example. [Figure 94] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fourth modification of the second arrangement example. [Figure 95] FIG. 10 is a diagram showing an example of arrangement of MIMO antennas according to a fourth modification of the second arrangement example. [Figure 96] FIG. 10 is a diagram showing an example of 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 INVENTION

[0015] A MIMO radar transmits signals (radar transmission waves) multiplexed using, for example, time division, frequency division, or code division from multiple transmitting antennas (also called transmitting array antennas).The MIMO radar then receives signals (radar reflected waves) reflected by surrounding objects using multiple receiving antennas (also called receiving array antennas), and separates and receives the multiplexed transmission signals from each received signal.By performing this processing, the MIMO radar can extract a propagation path response expressed as the product of the number of transmitting antennas and the number of receiving antennas, and performs array signal processing on these received signals as a virtual receiving 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) whose maximum number is equal to the product of the number of transmitting antenna elements and 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, 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 (longitudinal 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] Figure 1(b) shows a virtual receiving array including the transmitting and receiving array antennas with the antenna arrangement shown in Figure 1(a). The virtual receiving array shown in Figure 1(b) is composed of 16 virtual antenna elements (VA#1 to VA#16) with four antennas in the horizontal direction and four antennas in the vertical direction arranged in a rectangular shape. In Figure 1(b), the element spacings in the horizontal and vertical directions of the virtual receiving array are 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 This becomes:

[0020] Figures 2(a) and 2(b) show the horizontal element spacing d in the antenna arrangement of the MIMO radar shown in Figure 1(a). 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 Figures 2(a) and 2(b), 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 angular separation performance for multiple targets. For example, in Figures 2(a) and 2(b), the beam width at a power value of 3 dB is approximately 26°. Also, as shown in Figures 2(a) and 2(b), side lobes are generated around the main beam. In radar devices, side lobes can cause false detection as virtual images. 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 Figures 2(a) and 2(b), for example, the power ratio of the side lobe to the peak level normalized by the peak level of the main beam (Peak Sidelobe Level Ratio (PSLR)) is approximately -13 dB (when equal-amplitude beam weights are 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 antenna's directivity (beam width). The directivity of an antenna becomes narrower, for example, as the antenna aperture becomes wider. Therefore, narrowing the antenna's directivity tends to require an increase in antenna size.

[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. Narrowing the vertical directivity using a sub-array antenna can improve the antenna gain in the vertical direction and reduce reflected waves in unwanted directions such as the road surface.

[0024] The vertical direction refers to the height direction of the vehicle on which the radar device is mounted (or installed), and the horizontal direction refers to 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, Figure 3 shows an example of a subarray in which eight planar patch antenna elements are arranged in the vertical direction (longitudinal direction in Figure 3) and one element is arranged in the horizontal direction (horizontal direction in Figure 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 the configuration shown in Fig. 3, and for example, the number of elements in each of the vertical and horizontal directions may differ from the number shown in Fig. 3.

[0027] Here, when a subarray 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 subarray antenna. For example, when the antenna elements constituting the subarray antenna are arranged vertically, the size of the subarray antenna may be one wavelength or more. Therefore, for example, when a subarray antenna is used in the vertical direction in the MIMO radar shown in FIG. 1(a) (when subarraying is performed in the vertical direction), the vertical element interval d V is extended 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 be 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 Figure 4, the vertical element spacing d v = λ, horizontal element spacing d H =0.5λ, and in Figure 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 compared to the side lobes in Figures 2(a) and 2(b), for example, high-level side lobes (e.g., grating lobes) are generated in the vertical direction around the main beam. 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 at which high-level side lobes (e.g., grating lobes) occur in the vertical direction is narrower. That is, the vertical element spacing d V It can be seen that the wider the angle, the narrower the angular interval at which side lobes (for example, grating lobes) occur.

[0031] As described above, in a radar device, the larger the antenna size in the vertical direction, the wider the vertical element spacing becomes, which makes it more likely that grating lobes will 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 will be more likely to erroneously detect false peaks caused by grating lobes as targets within the detection angle range, which may degrade the detection performance of the radar device.

[0032] Furthermore, even if a grating lobe is outside the radar device's expected detection angle range, 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 radar device's field of view, which may result in a deterioration of the radar device's detection performance.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 field of view is likely to experience a 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 accurate or more accurate the vertical angle measurement or angular resolution of the radar device can be. For example, comparing the vertical element spacings in Figures 2, 4, and 5, which 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. Thus, the narrower the vertical beam width, the more accurate or accurate the vertical angle measurement or angular resolution of the radar device can be.

[0034] Similarly, for example, the wider the horizontal element spacing, the narrower the horizontal beam width, and the more accurate or more accurate the horizontal angle measurement or angular resolution of the radar device can be. On the other hand, the wider the horizontal element spacing, the more likely grating lobes are to 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 is more likely to erroneously detect false peaks due to grating lobes as targets within the detection angle range, which may degrade the detection performance of the radar device.

[0035] Therefore, in a non-limiting embodiment of the present disclosure, an antenna arrangement that can suppress 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 body such as a vehicle. The radar device mounted on the moving body can be used as, for example, an advanced driver assistance system (ADAS) that improves collision safety, or as a sensor used to monitor the surroundings of the moving body during autonomous driving.

[0037] Furthermore, a 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, and can be used as a sensor in an assistance system that improves the safety of passing vehicles or pedestrians.

[0038] The radar device is not limited to these uses, and 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 redundant descriptions thereof will be omitted.

[0040] Below, a radar device will be described that has a configuration in which a transmitting branch transmits different code-division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch separates each transmit signal and performs reception processing (in other words, a MIMO radar configuration). However, the radar device configuration is not limited to this, and may also have a configuration in which a transmitting branch transmits different frequency-division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch separates each transmit signal and performs reception processing. Similarly, a radar device may also have a configuration in which a transmitting branch transmits time-division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch performs reception processing.

[0041] Similarly, a configuration may be adopted in which a transmitting branch transmits different Doppler division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch separates each transmit signal for reception processing.Similarly, a configuration may be adopted in which a transmitting branch transmits transmit signals multiplexed using a combination of 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 for reception processing.

[0042] In the following, as an example, a configuration of a radar system using a frequency-modulated pulse wave such as a chirp pulse (also called fast chirp modulation) will be described. However, the modulation system is not limited to frequency modulation. For example, an embodiment of the present disclosure can also be applied 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 it 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 composed of 1000 MHz and 1000 MHz.

[0046] The radar receiver 200 receives reflected wave signals, which are radar transmission signals reflected by a target (object, not shown), using a receiving array antenna including a plurality (e.g., Na) of receiving antennas 202. The radar receiver 200 performs signal processing on the reflected wave signals received by each receiving antenna 202, for example, to detect the presence or absence of a target or estimate the arrival distance, Doppler frequency (in other words, relative speed), and arrival direction of the reflected wave signals, and outputs information related to the estimation results (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 transmission antenna .

[0049] The radar transmission signal generation unit 101 generates a radar transmission signal. The radar transmission signal generation unit 101 includes, for example, a modulation signal generation unit 102 and a VCO (Voltage Controlled Oscillator) 103. Each component of the radar transmission signal generation 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 modulation signal (hereinafter, referred to as a frequency chirp signal or chirp signal, for example) based on the modulation signal output from the modulation signal generating unit 102, as shown in (a) of FIG. 7, and outputs it to the phase rotation unit 105 and the radar receiving unit 200 (a mixer unit 204, which will be 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 about the generated code to the radar receiving unit 200 (the output switching unit 209, which will be described later).

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

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

[0055] The code generator 104 generates, for example, a different code for each transmitting antenna 106 that performs code-multiplexed 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 sigma-based codes (N sigma-based codes) included in a code sequence (for example, an orthogonal code sequence (also simply called a code or an orthogonal code) that are orthogonal to each other) of a code length (in other words, the number of code elements) Loc. allcode (hereinafter, N allcode Of the N orthogonal codes (sometimes referred to as 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, N of the code length Loc CM Code ncm =[OC ncm (1), OC ncm (2),…, OC ncm (Loc)]. ncm (noc)" is the ncm-th orthogonal code ncm In addition, "ncm" represents the index of the orthogonal code used for code multiplexing, and ncm=1,..., N CM In addition, "noc" is the index of the code element, noc=1,...,Loc.

[0059] As described above, N generated in 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 a Walsh-Hadamard code is a power of 2, and an orthogonal code of each code length includes the same number of orthogonal codes as the code length. For example, a 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, a Walsh-Hadamard code with a code length Loc=2, 4, 8, or 16 contains 2, 4, 8, or 16 orthogonal codes, respectively. allcode (2)=2, N allcode (4)=4, N allcode (8)=8 and N allcode (16)=16. For example, the code generation unit 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 orthogonal codes in the above will be described.

[0063] For example, the number of code multiplexes N CM If Loc=3, the code generation unit 104 determines, for example, three orthogonal codes from among the Walsh-Hadamard codes with a code length of Loc=4 as codes for code-multiplexed 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 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 other than Walsh-Hadamard codes, for example, 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-multiplexed transmission using different orthogonal codes for the transmitting antennas Tx#1 to Tx#Nt that perform code-multiplexed transmission. Therefore, the code generator 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 is.

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

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 Nc times, which is, for example, an integer multiple of Loc (for example, Ncode times). For example, Nc=Loc×Ncode.

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

[0074] The phase rotation unit 105 may be, for example, N txThe phase rotation unit 105 includes a phase shifter or a phase modulator corresponding to each of the transmitting antennas 106. For example, the phase rotation unit 105 rotates the phase ψ input from the code generation unit 104 with respect to the chirp signal input from the radar transmission signal generation unit 101 every transmission period Tr. ncm (m) is assigned to each.

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

[0076] N tx The outputs from the phase rotation units 105 for the transmitting antennas 106 are, 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 is N Tx = 3, and the number of code multiplexes N CM Here, we will explain the case where code multiplexing transmission is performed when the number of transmitting antennas is Nt and the number of code multiplexing N 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 generator 104 to the phase rotator 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 by 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 by 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 every radar positioning (for example, every Nc transmission periods (Nc×Tr)). ncm The code used may be set variably.

[0083] An example of the 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 demultiplexer 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 processing unit 201 as a received signal.

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

[0087] The radio reception unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with a chirp signal, 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, thereby outputting a beat signal with 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) can be obtained as the beat frequency.

[0088] The signal processing unit 206 of each antenna system processing unit 201-z (where z=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 (for example, a beat signal) output from the LPF 205 is converted into discrete sample data by the AD conversion unit 207 in the signal processing unit 206, which is discretely sampled.

[0090] The beat frequency analysis unit 208 analyzes 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 the 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 FFT processing by multiplying a window function coefficient such as a Han window or a Hamming window. Note that by using the window function coefficient, the radar device 10 can suppress side lobes that appear around the beat frequency peak. In addition, data If 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 called 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, and m = 1, …, N C The beat frequency index f b The smaller the beat frequency, the shorter 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 using the following equation (8): b ) can be converted into the beat frequency index f b Let "distance index f b " is also called.

number

[0093] where 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 the output of the beat frequency analysis unit 208 for each transmission period to the OC_INDEX-th Doppler analysis unit 210 out of 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 for each Loc, 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 Doppler analysis. In this case, the FFT size is Ncode, and the maximum Doppler frequency at which aliasing does not occur, as derived from the sampling theorem, is ±1 / (2Loc×Tr). Also, the Doppler frequency index f s The Doppler frequency interval 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 z-th signal processing unit 206 z noc (f b , f s ) is expressed by the following equation (9): where j is the imaginary unit and z=1 to Na.

number

[0098] Furthermore, 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, when zero-padded data is included, the FFT size in the Doppler analysis unit 210 is 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. 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 the first to Na-th signal processors 206, and determines the distance index f that gives the peak signal. b_cfar and the Doppler frequency index f s_cfar Extract.

[0104] The CFAR unit 211 calculates the output VFT of the Doppler analysis unit 210 of the first to Na-th signal processing units 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 that has a received power greater than the threshold value. b_cfar , the Doppler frequency index f s_cfar , and received power information PowerFT(f b_cfar , f s_cfar ) to the code 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 demultiplexes, for example, the distance index f extracted in the CFAR unit 211. b_cfar and the Doppler frequency index f s_cfar The code-multiplexed signal is demultiplexed based on the above.

[0108] For example, the code demultiplexing unit 212 demultiplexes 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 analysis unit 210 in the z-th antenna system processing unit 201. b_cfar and the Doppler frequency index f s_cfar Orthogonal code for the output of Code ncm is the output (for example, the code separation result) of the code-multiplexed signal obtained by code separation using z=1,...,Na and ncm=1,...,N CM is. Furthermore, in equation (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 that does not include Doppler aliasing (in other words, the Doppler range), the Doppler phase rotation caused by the time difference in Doppler analysis between 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 ) as a reference for 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 Loc-th Doppler analyzer 210 z Loc (f b_cfar , f s_cfar ) and the Doppler frequency index f s_cfar is a vector whose elements are Doppler phase correction coefficients that correct 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, the output VFT of the Loc Doppler analyzers 210 in the z-th antenna system processor 201, as shown in the following equation (15). 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 component VFT corresponding to 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 targets detected by the radar device 10 are within this range.

[0114] The configuration of the radar device 10 is not limited to the configuration shown in Fig. 6, and the detectable Doppler frequency range can also be 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 use the determination result to perform code demultiplexing.

[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 bigger than.

[0116] By using such a configuration, the detectable Doppler range can be further expanded, for example, the maximum detectable Doppler frequency can be set to ±1 / (2×Tr). Therefore, it becomes possible to operate the code demultiplexer assuming that the targets detected by the radar device are 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] An example of the antenna arrangement of the transmitting antenna 106 and the receiving antenna 202, and an example of the direction estimation process in the direction estimation unit 213 when each example of the arrangement is applied will be described below.

[0119] Furthermore, in the following arrangement examples and modifications, the arrangement of the transmitting antenna 106 may be replaced with the 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 modifications may be interchanged. When the horizontal and vertical directions are interchanged in the antenna arrangement, the radar device 10 can achieve the same effect as when the horizontal and vertical directions in the following arrangement examples are interchanged.

[0121] The horizontal and vertical directions in the layout example do not have to strictly match the horizontal and vertical directions, and the entire layout example may be tilted at a predetermined angle while maintaining the relative positional relationship between the transmitting antennas and receiving antennas included in the layout example. Even in this case, the relative positional relationship between the transmitting antennas and receiving antennas included in the layout example is maintained, and therefore 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 arranged at different intervals. Tx It may include transmit antennas other than transmit antenna 106.

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

[0125] The first diagonal antenna group and the second diagonal antenna group may each 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 antennas 106. In other words, a first oblique direction (e.g., corresponding to the first direction) in which a first oblique antenna group (e.g., corresponding to the first antenna group) is arranged, a second oblique direction (e.g., corresponding to the second direction) in which a second oblique antenna group (e.g., corresponding to the second antenna group) is arranged, and a plurality of (e.g., N Tx The directions in which the transmitting antennas 106 are arranged (for example, corresponding to the 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 in any positions that satisfy Arrangement Condition 1. 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, antenna elements with large vertical sizes can be arranged.

[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 obtained by computer simulation for that placement example.

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

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

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

[0132] In Figure 8, N Tx The six transmitting antennas Tx#1 to Tx#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 Arrangement Example 1, a plurality of (for example, N Tx All of the transmitting antennas 106 (number of transmitting antennas) may be arranged in a predetermined direction (e.g., corresponding to the third direction). In Arrangement Example 1, 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] 8, Na=8 receiving antennas Rx#1 to #8 include a first group of oblique antennas Rx#1 to #4 arranged in a first oblique direction and a second group of oblique antennas Rx#5 to #8 arranged in a second oblique direction. Here, in FIG. 8, the first and second oblique directions are not parallel but different directions, and satisfy Arrangement Condition 1. Also, as shown in FIG. 8, the first and second oblique directions are not parallel but different from the arrangement direction of the transmitting antenna 106 (for example, the horizontal direction). Also, for example, as shown in FIG. 8, the first and second oblique directions are different from the vertical and horizontal directions.

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

[0135] 8, the antenna arrangement of the first oblique antenna group arranged in the first oblique direction and the antenna arrangement of the second oblique antenna group arranged in the second oblique 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 oblique antenna group Rx#1 to #4 and the second oblique antenna group Rx#5 to #8 are arranged in horizontal inversion symmetry (also called left-right inversion symmetry or mirror symmetry).

[0136] In FIG. 8, adjacent antennas are spaced equally apart in each of the plurality of 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.

[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, the basic interval D H , and the basic vertical spacing D V The scales on the horizontal and vertical axes are the same for the virtual receiving array arrangements in the other examples below.

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

number

[0139] Here, the position coordinates of the 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 expressed as (X R_#m ,Y R_#m ) (for example, m=1,..,Na), and the position coordinates of the virtual antenna VA#k that constitutes the virtual receiving array are expressed as (X V_#k ,Y V_#k ) (e.g., k=1,.., N Tx ×Na).

[0140] 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 receiving antennas Rx#1 to Rx#8 as shown in FIG. 8, the position coordinates of virtual antennas VA#1 to VA#48 constituting a virtual receiving array antenna are calculated by equation (16). As an example, the position coordinates of virtual antennas VA#1 to VA#16 are calculated by (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 Although the case where λ is set to 0.5λ will be described, λ may be set to a value of approximately 0.45λ to 0.8λ (for example, any value in the 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 same setting applies to the subsequent arrangement examples (or modified examples). Note that λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, if a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency in the frequency sweep band of the chirp signal.

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

[0145] In FIG. 1, the direction estimation unit 213 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 ) and performs target direction estimation processing.

[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 transmit 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 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 the received signals 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 ) the first element of the column vector element DeMul1 1 (f b_cfar , f s_cfar ) Similarly, the second 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 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.

[0150] For example, the direction estimator 213 calculates the virtual receiving array correlation vector h(f b_cfar , f s_cfar ) is used to calculate the array correction value h_cal, which corrects the phase and amplitude deviations between the transmitting and receiving array antennas. [y] By multiplying by , the virtual receiving array correlation vector h _after_cal (f b_cfar , f s_cfar ) is output. Then, the direction estimation unit 213 performs processing to estimate the horizontal and vertical directions based on the phase difference between the receiving antennas of the arriving reflected waves. 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 influence of inter-element coupling between the antennas (N Tx ×Na) order square matrix. When the coupling between the antennas of the virtual receiving array can be ignored, CA becomes a diagonal matrix, and the diagonal elements contain 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 corrected for deviations between antennas _after_cal (f b_cfar , f s_cfar ) is N Tx ×Na elements. In the following, the elements are expressed as follows and are 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 ) to estimate the horizontal and vertical directions. 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 The direction estimation unit 213 calculates a spatial profile by varying the azimuth direction θ and elevation angle direction Φ in the calculated spatial profile within a specified angle range. The direction estimation unit 213 extracts a predetermined number of maximum peak directions in descending order of magnitude from the calculated spatial profile, and outputs the azimuth direction and elevation angle direction of each maximum peak as an arrival direction estimate (e.g., positioning output).

[0154] The direction of arrival 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 follows: where the superscript H is the Hermitian transpose operator. Other methods such as Capon and MUSIC can also be applied.

number

[0156] Here, the azimuth direction θ u is a vector obtained by varying the azimuth range θmin to θmax within 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] Also, the elevation angle Φ v is a vector obtained by varying the azimuth range Φmin to Φmax for which 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 a complex response of a virtual receiving array antenna when radar reflections arrive from the azimuth direction θ and the elevation 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] Here, 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-described 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 the beamformer method is used as the direction of arrival estimation algorithm of the direction estimation unit 213. As an example, Fig. 10 plots the output of the direction of arrival estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically. Here, the results are shown for the case where each transmitting antenna and receiving antenna is omnidirectional, and the direction estimation results (computer simulation results) in other examples below also show results for the case where each antenna is omnidirectional.

[0162] 10(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. Also, FIG. 10(b) is a diagram showing the normalized power values ​​in FIG. 10(a), with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values, in a grayscale color map. In FIG. 10, the normalized power values ​​may be shown as decibel values ​​(dB) normalized by 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, and the receiving antennas 202 are arranged at intervals of six wavelengths or more in the horizontal direction, while the virtual antennas in the virtual receiving array arrangement shown in Fig. 9 are arranged at intervals of one wavelength or more in the horizontal direction, which is an antenna spacing at which grating lobes can occur. For example, when the target direction is 0 degrees in the horizontal direction, grating lobes can occur at -41.8 degrees and 41.8 degrees in the horizontal direction.

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

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

[0166] For comparison with Arrangement Example 1, Fig. 11 shows an antenna arrangement (hereinafter referred to as "Comparative Arrangement 1") in which the first oblique antenna group Rx#1 to #4 of receiving antennas 202 in Arrangement Example 1 shown in Fig. 8 is used. Fig. 12 shows the direction estimation results using the beamformer method in the case where Comparative Arrangement 1 is applied. As with Fig. 10, Fig. 12 plots the output of the direction-of-arrival estimation evaluation function value in the horizontal ±90 degree range and the vertical ±90 degree range when the target true value is set to 0 degree horizontally and 0 degree vertically.

[0167] As in comparative arrangement 1, the virtual receiving array arrangement when the first oblique 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, for comparison with Arrangement Example 1, Fig. 13 shows an antenna arrangement (hereinafter referred to as "Comparative Arrangement 2") in which the second oblique antenna group Rx#5 to #8 of the receiving antennas 202 in Arrangement Example 1 shown in Fig. 8 are used. Fig. 14 shows the direction estimation results using the beamformer method in the case where Comparative Arrangement 2 is applied. As with Fig. 10, Fig. 14 plots the output of the direction-of-arrival estimation evaluation function value in the horizontal ±90 degree range and the vertical ±90 degree range when the target true value is set to 0 degree horizontally and 0 degree vertically.

[0169] As in comparative arrangement 2, when the second diagonal antenna group Rx#5 to #8 of the receiving antennas 202 in arrangement example 1 are used, the virtual receiving array arrangement 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, when using the first oblique antenna group Rx#1 to #4 of the receiving antennas 202 of Arrangement Example 1 shown in FIG. 8, as in Comparative Arrangement 1 shown in FIG. 11, 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 (e.g., (a) and (b) in FIG. 12) obtained by using the beamformer method as the direction of arrival estimation algorithm of the direction estimation unit 213 relative to the target true value (e.g., 0 degrees horizontally, 0 degrees vertically).

[0171] Furthermore, for example, when using the second oblique antenna group Rx#5 to #8 of the receiving antennas 202 of Arrangement Example 1 shown in FIG. 8, 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 from 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, and is not parallel to each other. 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 but are shifted.

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

[0174] Therefore, in Arrangement Example 1 including the first and second oblique antennas, the directions (two-dimensional angular directions) of the grating lobes generated in Comparison Arrangement 1 including the first oblique antenna group and the grating lobes generated in Comparison Arrangement 2 including the second oblique antenna group do not match and are likely to be dispersed, as shown in Fig. 8. For this reason, in Arrangement Example 1, the peak level in the grating lobe direction is likely 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 oblique antenna group and the second oblique antenna group are horizontally inverted and symmetrical as shown in Fig. 8, the virtual receiving array arrangements corresponding to comparison arrangements 1 and 2 are horizontally inverted and symmetrical. As a result, in comparison arrangements 1 and 2, the horizontal and vertical two-dimensional directions in which grating lobes occur are horizontally inverted and symmetrical, and as shown in Figs. 12 and 14, it can be seen that the deviations in the horizontal and vertical two-dimensional angular directions in which grating lobes occur become larger.

[0176] Therefore, in Arrangement Example 1, for example, when the arrangement directions (e.g., diagonal directions) of the first oblique antenna group and the second oblique 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 the 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 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 used in direction estimation tends to be. Therefore, when the directions of 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, which can cause grating lobe power to overlap and increase the grating lobe power. Therefore, the fewer the number of antennas in 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 in 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] 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 vertical size (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 making it possible to improve the antenna gain in the vertical direction.

[0180] The distance between the transmitting antenna 106 and the receiving antenna 202 may be set to be sufficiently wider than the size of the antenna elements, or they may be shifted horizontally 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 is also an antenna arrangement that can suppress grating lobes that occur in the virtual receiving array.

[0182] 8 can be arranged in any location and still achieve the same grating lobe suppression effect. 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 larger vertical sizes.

[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, the direction estimation result, and further outputs a distance index f b_cfar (e.g., 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 (not shown) in the case of an in-vehicle radar, or to an infrastructure control device (not shown) in the case of an infrastructure radar.

[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). 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 antennas 202 of the radar device 10 include, 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 addition, in the antenna arrangement of the radar device 10, the first oblique direction, the second oblique direction, and a predetermined direction (for example, the 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 the MIMO array arrangement, and also allows grating lobes occurring in the virtual receiving array to be suppressed.

[0189] Furthermore, in Arrangement Example 1, as described above, a grating lobe suppression effect can be obtained by differentiating the arrangement directions of the first diagonal antenna group and the second diagonal antenna group in the receiving antenna 202. Therefore, 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. This allows the aperture length of the virtual receiving array to be expanded depending on the setting of at least one of the element spacing of the transmitting antenna 106 and the spacing between the first diagonal antenna group and the second diagonal antenna group, thereby improving the angle measurement accuracy and angle separation performance in the vertical and horizontal directions of the radar device 10.

[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 Arrangement Example 1, at least one of the transmitting antenna 106 and the receiving antenna 202 may further include an antenna element in the antenna configuration shown in Fig. 8. In other words, it is sufficient that each of the transmitting antenna 106 and the receiving antenna 202 of the radar device 10 includes 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 at the position shown in Equation (16). For example, by adding an antenna element to at least one of the transmitting antenna 106 and the receiving antenna 202, another virtual antenna is added to the virtual receiving array arrangement shown in Fig. 9. Even in the case of an antenna arrangement including Arrangement Example 1, the effects of Arrangement Example 1 described above are maintained, and effects similar to those of Arrangement Example 1 can be obtained.

[0192] For example, an antenna may be added to the antenna configuration of Arrangement Example 1. Adding 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. Note that adding an antenna can be similarly applied to the following 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 and vertical directions are swapped may be applied. In this case, the virtual receiving array arrangement is obtained by swapping the horizontal and vertical directions, and angular separation performance is obtained by swapping the horizontal and vertical directions. Note that swapping the horizontal and vertical directions 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 and vertical directions.

[0194] A modification of Arrangement Example 1 will be described below.

[0195] [Modification 1 of Arrangement Example 1] In the first modification of the first arrangement example, for example, the distance (for example, the minimum distance) between the first diagonal antenna group and the second diagonal antenna group 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 distance between the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 (for example, the distance between Rx#4 and Rx#8) is N Tx This is narrower than the aperture length of the transmitting antennas 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 distance between the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 (for example, the distance between Rx#4 and Rx#8) is N Tx It may be wider than the aperture length (for example, the distance between Tx#1 and Tx#6) of the transmitting antennas 106 (for example, corresponding to the third antenna group).

[0198] For example, in the case of 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 TxThe spacing is set to be wider than the aperture length (for example, the spacing between Tx#1 and Tx#6) of the six transmitting antennas 106. 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 be the same as that in Arrangement Example 1 (for example, 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 that make up the 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 (computer simulation result) when the antenna arrangement according to the above-described 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 results when a beamformer method is used as the direction of arrival estimation algorithm in direction estimation unit 213, using a wavelength of λ = 0.5λ. As an example, Fig. 17 plots the output of the direction of arrival estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

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

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

[0205] Furthermore, 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 compared to Arrangement Example 1. Therefore, as shown in FIG. 17, the peak in the target true value direction is sharper in the horizontal direction compared to 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 beside (in the horizontal direction) the peak in the target true value direction, compared to 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 oblique antenna group and the second oblique 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 oblique antenna group and the second oblique antenna group, it is possible to improve the horizontal angle measurement accuracy or estimation accuracy, while increasing the side lobe level beside (in the horizontal direction) the peak in the target true value direction. For example, the distance (e.g., the minimum distance) between the first oblique antenna group and the second oblique antenna group 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 reversed relative to the arrangement shown in Fig. 15, or the respective arrangements may be inverted left to right (e.g., horizontally), or up to down (e.g., vertically). In these cases, the same effect as in Arrangement Example 1-1 described above can be obtained. Note that changing 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.

[0210] In 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 reversed 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 reversed 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 from 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 (for example, on both sides in the horizontal direction), thereby achieving the effect of reducing the antenna mounting area.

[0213] [Modification 2 of Arrangement Example 1] In Variation 2 of Arrangement Example 1, for example, the distance (e.g., the minimum distance) between the first diagonal antenna group and the second diagonal antenna group may be closer than in Arrangement Example 1. Also, in Variation 2 of Arrangement Example 1, 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 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 distance between the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 (for example, the distance between Rx#4 and Rx#8) is N Tx This is narrower than the aperture length of the transmitting antennas 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 to #4 and the second diagonal antenna group Rx#5 to #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 variation 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 arrangement example 1-2a shown in FIG. 20, N 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) is set in the horizontal direction. H ) is the element spacing of the transmitting antenna 106 (for example, 9D H ) is narrower than

[0218] In addition, for example, in the case of the arrangement example 1-2b shown in FIG. 21, N 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, Rx#1 to #4 are included in the first diagonal antenna group, and Rx#4 to #7 are included in the second diagonal antenna group. 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 from the antenna arrangement shown in Fig. 20.

[0220] Furthermore, 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 from 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-described Arrangement Example 1-2a and Arrangement Example 1-2b are applied will be described.

[0222] 24 and 25 show the MIMO array layouts (D H = 0.5λ, D V = 0.5λ), and the beamformer method is used as the arrival direction estimation algorithm of the 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 range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

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

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

[0225] In arrangements such as arrangement example 1-2a and arrangement example 1-1b, 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] Furthermore, in arrangements such as Arrangement Example 1-2a and Arrangement Example 1-1b, the virtual antennas are arranged without overlapping, so 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 of the target true value direction becomes sharper in the horizontal direction, and the angle measurement accuracy or resolution in the horizontal direction is improved. Furthermore, 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 reduce the variation in the horizontal spacing of the virtual antennas, and also have the effect of further reducing the rise of side lobes near the main lobe.

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

[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 of the radar device 10 and can suppress grating lobes.

[0229] Although FIG. 21 illustrates a case where the antennas at the ends of the first and second diagonal antenna groups (e.g., Rx#4) overlap, the present invention is not limited to this. For example, the antennas overlapping the first and second diagonal antenna groups may be antennas different from the antennas at the ends of the diagonal antenna groups.

[0230] [Modification 3 of Arrangement Example 1] The inclinations of the first and second oblique antenna groups (for example, positional changes 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 Modification 3 of Arrangement Example 1, an example will be described in which the inclinations of the first diagonal antenna group and the second diagonal antenna group are set to be gentler than those in Arrangement Example 1.

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

[0233] In Modification 3 of Arrangement Example 1, for example, as shown in Fig. 26 (hereinafter referred to as "Arrangement Example 1-3"), the first oblique antenna group Rx#1-#4 are arranged so as to be shifted horizontally from left to right in the drawing at intervals of one wavelength, and also shifted downward in the vertical direction at intervals of 0.5 wavelengths. Also, as shown in Fig. 26, the second oblique antenna group Rx#5-#8 are arranged so as to be shifted horizontally from right to left in the drawing at intervals of one wavelength, and also shifted downward in the vertical direction at intervals of 0.5 wavelengths. Note that in Arrangement Example 1-3 shown in Fig. 26, the inclinations of the first and second oblique antenna groups may be set in the same manner as in Arrangement Example 1 (e.g., Fig. 8).

[0234] As described above, in Fig. 26, the change in vertical position relative to the horizontal position between adjacent antennas in 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 that make up the 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 (computer simulation result) when the antenna arrangement according to the above-described Arrangement Example 1-3 is applied will be described.

[0238] Figure 28 shows the MIMO array layout of layout 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. As an example, Fig. 28 plots the output of the arrival direction estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0239] Note that (a) of Fig. 28 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. Also, (b) of Fig. 28 is a diagram showing (a) of Fig. 28, 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. 28, the normalized power values ​​may be shown, for example, as decibel values ​​(dB) normalized by peak power.

[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] Furthermore, in Arrangement Example 1-3, compared to Arrangement Example 1, the virtual receiving array arrangement (for example, the aperture length of the virtual receiving array) is wider in the horizontal direction, and therefore, as shown in FIG. 28, the peak of 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.

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

[0243] 28, in Arrangement Example 1-3, a side lobe of about −10 dB may occur beside (in the horizontal direction) the peak in the target true value direction, compared to 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 oblique antenna group and the second oblique antenna group is wider than that in Arrangement Example 1.

[0244] For example, by increasing the distance between the first oblique antenna group and the second oblique antenna group, the horizontal angle measurement accuracy or estimation accuracy can be improved, while the side lobe level beside (in the horizontal direction) the peak of the target true value direction increases. For example, the distance (e.g., the minimum distance) between the first oblique antenna group and the second oblique 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] Furthermore, in FIG. 26, the 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 limiting, 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 shorter 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 oblique antenna groups is set to be gentler than in Arrangement Example 1, but the present invention is not limited to this, and the inclination of the first and second oblique antenna groups may be set to be steeper than in Arrangement Example 1. When the inclination of the first and second oblique antenna groups is made steeper, the fourth variation of Arrangement Example 1 or Arrangement Example 2 described below may be applied.

[0247] [Modification 4 of Arrangement Example 1] For example, in Arrangement Example 1 shown in Fig. 8, the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #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 rather than parallel.

[0248] For example, as shown in FIG. 29 (hereinafter referred to as "arrangement example 1-4a"), the first diagonal antenna group Rx#1 to #4 and the second diagonal antenna group Rx#5 to #8 may have asymmetric inclinations (for example, a change in position in the vertical direction relative to the horizontal direction), or different antenna spacings may be set in 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 Arrangement Example 1-4a (asymmetric tilt), Arrangement Example 1-4b (vertically shifted position), and Arrangement Example 1-2c (number of antennas) may be combined. For example, Figure 32 (hereinafter referred to as "Arrangement Example 1-4d") shows an arrangement that combines Arrangement Example 1-4a, Arrangement Example 1-4b, and Arrangement Example 1-4c.

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

[0253] Such an arrangement in which the arrangement directions of the first oblique antenna group and the second oblique antenna group are rotationally symmetric about 90 degrees to each other 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 used in direction estimation tends to be. Therefore, when the directions of suppressed grating lobes are close to each other, the fewer the number of antennas in the radar device 10, the wider the beam width becomes, which can cause the power of the suppressed grating lobes to overlap, increasing the power of the grating lobes. Therefore, the fewer the number of antennas in 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 in the radar device 10 is small, for example, an arrangement in which the arrangement directions of the first oblique antenna group and the second oblique antenna group are rotationally symmetric about 90 degrees to each other can suppress the overlap of 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 make up the 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-described 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 shows the direction estimation results when the beamformer method is used as the direction of arrival estimation algorithm in direction estimation section 213. As an example, Figures 37 to 40 plot the output of the direction of arrival estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 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 being the horizontal direction and the vertical axis being the vertical direction, as a grayscale color map. Also, 37 to 40(b) are diagrams showing the normalized power values ​​in 37 to 40(a) as a grayscale color map, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value. In 37 to 40, the normalized power value may be shown as a decibel value (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 Arrangement Example 1 and Modifications 1 to 4, for example, the interval between transmitting antennas is set to the basic interval D H and the tilt of the receiving antenna 202 in the diagonal direction is set to an integer multiple of the basic interval D H and set the basic interval D in the vertical direction. V The case where the value is set to an integer multiple of .

[0261] That is, N Tx The transmitting antennas 106 are spaced apart horizontally by dT×D H are arranged 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 width of dRH1×D H and shifts vertically at intervals of D V The second diagonal antenna group is arranged in a diagonal direction with a shift interval of dRH2×D H and shifts vertically at intervals of D V 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 VFor example, dRH1 may be 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. dRH1 and dRH2 may also 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 when dRH1 = dRH2 and dT = 2, 4, 5, or 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 of 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 grating lobes generated due to the relationship between the transmitting antenna 106 and the first oblique antenna group will coincide with the direction of grating lobes generated due to the relationship between the transmitting antenna 106 and the second oblique antenna group. Therefore, for example, as shown in Figures 41 to 44, the larger dT is, the closer the first oblique antenna group and the second oblique antenna group may be arranged. By arranging the first oblique antenna group and the second oblique antenna group closer to each other, the distance between adjacent virtual antennas in the virtual receiving array can be narrowed, thereby enabling grating lobe suppression.

[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 make up the virtual receiving array antenna are calculated based on equation (16).

[0267] 45 to 48 are diagrams showing examples of the arrangement of virtual receiving arrays 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-described Arrangement Example 1-5a to Arrangement Example 1-5d are applied will be described.

[0269] 49 to 52 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 unit 213. As an example, Figures 49 to 52 plot the output of the arrival direction estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction 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 being the horizontal direction and the vertical axis being the vertical direction, as a grayscale color map. Also, FIGS. 49 to 52(b) are diagrams showing the normalized power values ​​in FIGS. 49 to 52(a), with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values, as a grayscale color map. In FIGS. 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, the peak level in the grating lobe direction is suppressed compared to the peak in the target true value direction, similar to Arrangement Example 1 (FIG. 10).

[0272] Furthermore, as shown in 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) becomes 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 more 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 grating lobes are suppressed to approximately -3 dB to 6 dB.

[0274] The tilt 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 integer multiple of the interval (e.g., dRV×D V When the azimuth angle θ is shifted by 1 / (dRV) (where dRV is an integer equal to or greater than 2), the direction of the vertical grating lobe generated by the relationship between transmitting antenna 106 and the first diagonal antenna group tends to coincide with the direction of the vertical grating lobe generated by 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 shifted by dRH2×D H and shifts vertically at intervals of D V Interval (or dRV×D V and dRV=1), they may be arranged in a diagonal direction shifting by

[0276] In addition, the tilt of the first diagonal antenna group and the second diagonal antenna group is dRH1×D in the horizontal direction. 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 modifications described below may be applied. A virtual receiving array configured using Arrangement Example 2 and its modifications 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 (examples will be described later).

[0277] In Arrangement Example 1 and Modifications 1 to 5, the spacing between 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 spacing D V Although an example in which an interval set to an integer multiple of D is used has been described, the present invention is not limited to this. V , D H The arrangement may not be an integer multiple of .

[0278] For example, N Tx The transmitting antennas 106 are arranged horizontally at an interval of αD 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 βD H and shifts vertically at intervals of γD V The pixels may be arranged diagonally shifted at intervals of .

[0279] where α, β, and γ are positive real values, and αD H is one wavelength or more, and βD H and γD V may be a real value of 0.45 to 0.8 wavelength or more, and the same effect as that 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 wavelength.

[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 that configure 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 from the antenna arrangement shown in Fig. 53.

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

[0283] Figure 55 shows the MIMO array arrangement (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. 55 plots the output of the arrival direction estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

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

[0285] As shown in FIG. 55, according to Arrangement Example 1-5e, 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.

[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 uneven intervals). In Fig. 56, the setting different from the arrangement intervals of the transmitting antennas 106 may be the same as in Arrangement Example 1 (for example, Fig. 8).

[0288] In addition, in the antenna arrangement example shown in Fig. 57 (hereinafter referred to as "Arrangement Example 1-6b"), the first diagonal antenna group and the second diagonal antenna group may be arranged at unequal intervals (or uneven 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 (for example, Fig. 8).

[0289] In addition, in the antenna arrangement example shown in Fig. 58 (hereinafter referred to as "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 uneven 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 (for example, 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] The arrangement is not limited to the above-described example, and for example, either the first diagonal antenna group or the second diagonal antenna group may be arranged at uneven intervals, or either 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 transmitting antennas 106 are arranged in two vertical stages, a configuration in which transmitting antennas 106 are arranged in two horizontal stages, a configuration in which the first and second diagonal antenna groups of receiving antennas 202 are arranged in two vertical stages, and a configuration in which the first and second diagonal antenna groups of receiving antennas 202 are arranged in two horizontal stages. 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] Below, 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, which are arranged in the same manner as Tx #1 to Tx #6, are arranged in multiple stages, shifted vertically. That is, in Fig. 59, the multiple transmitting antennas 106 have multiple sets of six antennas arranged horizontally (for example, a set of Tx #1 to #6 and a set of Tx #7 to #12).

[0298] 60 (hereinafter referred to as "arrangement example 1-7b"), Rx#1 to Rx#8 and Rx#9 to Rx#16, which are arranged in the same manner as Rx#1 to Rx#8, are arranged in multiple stages, shifted horizontally. That is, in FIG. 60, the plurality of receiving antennas 202 includes a plurality of pairs of first diagonal antenna groups and second diagonal antenna groups (for example, a pair of Rx#1 to #8 and a pair of Rx#9 to #16).

[0299] 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 plurality of receiving antennas 202 includes a plurality of pairs of first diagonal antenna groups and second diagonal antenna groups (for example, a pair of Rx#1 to #8 and a pair of Rx#9 to #16).

[0300] Also, for example, in FIG. 62 (hereinafter, "Arrangement Example 1-7d"), Tx#1 to Tx#6 and Tx#7 to Tx#8, which are arranged in the same manner as Tx#1 to Tx#6, are arranged in multiple stages, shifted vertically, and 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 vertically. That is, in FIG. 62, the multiple transmitting antennas 106 include multiple sets of six antennas arranged in the horizontal direction (e.g., a set of Tx#1 to #6 and a set of Tx#7 to #12). Also, in FIG. 62, the multiple receiving antennas 202 include multiple sets of first diagonal antenna groups and second diagonal antenna groups (e.g., a set of Rx#1 to #8 and a set of Rx#9 to #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 that make up 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-described 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 unit 213. As an example, Figures 67 to 70 plot the output of the arrival direction estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 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 being the horizontal direction and the vertical axis being the vertical direction, as a grayscale color map. Also, 67 to 70(b) are diagrams showing the normalized power values ​​in 67 to 70(a), with the horizontal axis being the horizontal direction and the vertical axis being the normalized power value, as a grayscale color map. In 67 to 70, the normalized power value may be shown as a decibel value (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, the peak level in the grating lobe direction is suppressed compared to the peak in the target true value direction, similar to Arrangement Example 1 (FIG. 10).

[0307] Furthermore, 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 increased, so that the peak of 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] Furthermore, 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 increased, 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] Furthermore, 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 increased, so that the peak of 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] Furthermore, 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 vertically and arranged in multiple stages. Therefore, in Arrangement Example 1-7d, the aperture length in the vertical direction of the virtual receiving array is increased, 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 it is possible to improve the angle measurement accuracy or estimation accuracy in the vertical direction of the radar device 10.

[0311] Note that different antenna elements (e.g., antenna elements of different sizes) may be used in the multi-stage configurations of Arrangement Examples 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 narrower directivity in the vertical direction, the horizontal direction, or both, than the SR antenna element, thereby increasing the directional gain of the antenna element. By using the LR antenna element, the radar device 10 can increase the received signal level of reflected waves from targets located farther away compared to when using the SR antenna element, thereby enabling detection of targets located farther away. Since the LR antenna element increases the 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-range (LR) antenna element may be applied to the first stage, and a short-range (SR) antenna element may be used in combination with the first stage. For example, as shown in Fig. 59, when transmitting antennas 106 are arranged in a two-stage multi-stage configuration in the vertical direction, a long-range (LR) antenna element may be applied to the first stage (e.g., Tx#1 to Tx#6), and a short-range (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 antenna 106 and the second stage transmitting antenna 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 with 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] [Modification 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 direction of the transmitting antennas 106 does not have 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 horizontally at intervals of one wavelength from left to right in the drawing (for example, 2D H ) and vertically at intervals of 0.25 wavelengths (e.g., 0.5D V ) and may be arranged with an upward shift. 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 arrangements that satisfy 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 from the antenna arrangement shown in Fig. 71.

[0318] Next, an example of a direction estimation result (computer simulation result) when the antenna arrangement according to the above-described 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 estimation unit 213. As an example, Fig. 73 plots the output of the arrival direction estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

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

[0321] As shown in FIG. 73, in Arrangement Example 1-8, 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.

[0322] Furthermore, in Arrangement Example 1-8, the transmitting antennas 106 are arranged at a gentle angle relative 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 extension. Therefore, 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 enables improvement in the angle measurement accuracy or estimation accuracy in the vertical direction of the radar device 10. Note that in Arrangement Example 1-8, the transmission beam direction is gently tilted, so the range in which grating lobes occur tends to be wider in the horizontal direction.

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

[0324] [Example of minimum antenna configuration and layout with few antennas for layout condition 1] Below, we will explain the minimum antenna configuration that satisfies Arrangement Condition 1, and an arrangement example in which the number of antennas that satisfies Arrangement Condition 1 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 1 described above.

[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 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 addition, in FIG. 74, the scales of the horizontal and vertical axes are, for example, D H , D V Let's say.

[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 Figs. 75 to 79 shows an example of a MIMO antenna arrangement, and (b) of Figs. 75 to 79 shows an example of a virtual receiving array arrangement configured using the MIMO antenna arrangement shown in (a) of Figs. 75 to 79. In Figs. 75 to 79, the scales of the horizontal and vertical axes are, for example, D H , D V Let's say.

[0329] For example, Figures 75 and 76 show the number of transmitting antennas N Tx76 shows an example of antenna arrangement when the number of receiving antennas Na is 2 and the number of receiving antennas Na is 4. In Figures 75 and 76, the first diagonal antenna group includes Rx#1 and Rx#2, and the second diagonal antenna group includes Rx#3 and Rx#4.

[0330] Also, for example, FIG. 77 shows the number of transmitting antennas 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] 78 and 79 show the case where the number of transmitting antennas is N Tx 78 and 79 show examples of antenna arrangements when the number of receiving antennas Na is 3 and the number of receiving antennas Na is 4. In Figures 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 antennas 106 include a "first oblique antenna group" arranged in a "first oblique direction" and a "second oblique antenna group" arranged in a "second oblique direction," and the first oblique direction and the second oblique direction are not parallel. In other words, the first oblique direction and the second oblique direction are different directions from each other. The Na receiving antennas 202 include a "third oblique antenna group" arranged in a "third oblique direction" and a "fourth oblique antenna group" arranged in a "fourth oblique direction," and the third oblique direction and the fourth oblique direction are not parallel. In other words, the third oblique direction and the fourth oblique 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 at any positions that satisfy Arrangement Condition 2. 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 becomes 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 and fourth oblique antenna groups, which satisfy Arrangement Condition 2, at arbitrary positions. For example, as shown in the following arrangement example or modification, by arranging the third and fourth oblique antenna groups so that their horizontal positions do not overlap each other, it becomes possible to arrange receiving antenna elements with large vertical sizes.

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

[0338] Furthermore, under arrangement condition 2, it is possible to suppress grating lobes in the vertical direction that occur when the inclinations of the first to fourth oblique directions are made steeper with respect to the horizontal direction, for example. This grating lobe suppression effect can further increase the aperture length in the vertical direction, and further improve the angle measurement accuracy or resolution in the vertical direction 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 obtained by computer simulation for that placement example.

[0340] <Layout example 2> 80 is a diagram showing an example of arrangement (for example, an example of 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, the basic interval D in the horizontal direction. H , and the basic vertical spacing D V The scales on the horizontal and vertical axes are the same for the MIMO antenna arrangements in the other examples below. H and D V may be spaced at intervals of 0.5 wavelengths.

[0341] In the example shown in Figure 80, the number of transmitting antennas is N Tx is six (for example, Tx#1, Tx#2, Tx#3, Tx#4, Tx#5, and Tx#6), and the number of receiving antennas Na is eight (for example, 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 oblique antennas Tx#1 to #3 arranged in a first oblique direction and a second group of oblique antennas Tx#4 to #6 arranged in a second oblique direction. In Fig. 80, the first and second oblique directions are not parallel to each other but are different from each other.

[0343] 80, Na=8 receiving antennas Rx#1 to #8 include a third group of oblique antennas Rx#1 to #4 arranged in a third oblique direction and a fourth group of oblique antennas Rx#5 to #8 arranged in a fourth oblique direction. In Fig. 80, the third oblique direction and the fourth oblique 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. 80 satisfies Arrangement Condition 2.

[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 by 1.5 wavelengths from left to right in the figure and are simultaneously shifted upward by 0.5 wavelengths in the vertical direction. Also, the second diagonal antenna group Tx#4-#6 shown in Fig. 80 are shifted horizontally by 1.5 wavelengths from left to right in the figure and are simultaneously shifted downward by 0.5 wavelengths in the vertical direction.

[0347] 80, the antenna arrangement of the first oblique antenna group arranged in the first oblique direction and the antenna arrangement of the second oblique antenna group arranged in the second oblique 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 oblique antenna group Tx#1 to #3 and the second oblique antenna group Tx#4 to #6 are arranged in inversion symmetry in the horizontal direction (or in left-right inversion symmetry or mirror symmetry).

[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, the aperture in the vertical direction can be enlarged more in Arrangement Example 2 than in Arrangement Example 1.

[0349] 80, the third diagonal antenna group Rx#1-#4 are shifted horizontally by 0.5 wavelength intervals from right to left in the drawing and also shifted downward by 1 wavelength intervals in the vertical direction. The fourth diagonal antenna group Rx#5-#8 are shifted horizontally by 0.5 wavelength intervals from left to right in the drawing and also shifted downward by 1 wavelength intervals in the vertical direction.

[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 to #4 and the fourth diagonal antenna group Rx#5 to #8 are arranged in a horizontally inverted symmetrical 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 further enlarged.

[0352] 80, the third diagonal antenna group Rx#1 to #4 and the fourth diagonal antenna group Rx#5 to #8 are arranged at intervals of one wavelength or more in the vertical direction. Therefore, the element spacing of the third diagonal antenna group and the fourth diagonal antenna group is 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, and therefore, by varying the two-dimensional directions (vertical and horizontal) in which grating lobes occur, it is 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 as shown in equation (16) based on, for example, the positions of transmitting antennas 106 constituting the transmitting array antenna (e.g., the positions of the feed points) and the positions of receiving antennas 202 constituting the receiving array antenna (e.g., the positions of the feed points).

[0355] The position coordinates of the 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,.., NTx ), and the position coordinates of the receiving antenna 202 (for example, Rx#m) constituting the receiving array antenna are expressed as (X R_#m ,Y R_#m ) (for example, m=1,..,Na), and the position coordinates of the virtual antenna VA#k that constitutes 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: (X V_#1 ,Y V_#1 )=(0,0), (X V_#2 ,Y V_#2 )=(-D H ,-2D V ), (X V_#3 ,Y V_#3 )=(-2D H , -4D V ), (X V_#4 ,Y V_#4 )=(-3D H ,-6D V ), (X V_#5 ,Y V_#5 )=(17D H , 0), (X V_#6 ,Y V_#6 )=(18D H , -2D V ), (X V_#7 ,Y V_#7 )=(19D H , -4D V ), (X V_#8 ,Y V_#8 )=(20 D H , -6D V ), (X V_#9 ,Y V_#9 )=(3D H , D V ), (X V_#10 ,YV_#10 )=(2D H , -D V ), (X V_#11 ,Y V_#11 )=(D H , -3D V ), (X V_#12 ,Y V_#12 )=(0, -5D V ), (X V_#13 ,Y V_#13 )=(20D H , D V ), (X V_#14 ,Y V_#14 )=(21D H , -D V ), (X V_#15 ,Y V_#15 )=(22D H , -3D V ), (X V_#16 ,Y V_#16 )=(23D H , -5D V )

[0357] Here, in the case of Figures 80 and 81, D H and D V In the following description, a case will be described in which λ is set to 0.5λ, but they may also be set to values ​​of approximately 0.45λ to 0.8λ. λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, if a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency in the frequency sweep band of the chirp signal.

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

[0359] For example, the direction estimation unit 213 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 transmit 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 a reflected wave signal from a target based on the phase difference between the receiving antennas 202.

[0361] For example, in the MIMO antenna arrangement example of 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 direction estimation processing in the horizontal and vertical directions. Note that the subsequent operation of direction estimation section 213 is the same as the operation when Arrangement Example 1 is used, and therefore a description thereof will be omitted.

[0363] Next, an example of a direction estimation result (computer simulation result) when the antenna arrangement according to the above-described 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 the direction estimation unit 213. As an example, Fig. 82 plots the output of the arrival direction estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0365] Note that (a) of Figure 82 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. Also, (b) of Figure 82 is a diagram showing the normalized power values ​​in a grayscale color map, similar to (a) of Figure 82, with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values. Also, (c) of Figure 82 is a diagram showing the normalized power values ​​in a grayscale color map, similar to (a) of Figure 82, with the horizontal axis being the vertical direction and the vertical axis being the normalized power values. Note that in Figure 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] 80, the antenna spacing between the first diagonal antenna group Tx#1 to #3 and the second diagonal antenna group Tx#4 to #6 in the transmitting antenna 106 of Arrangement Example 2 is equal to or greater than one wavelength, which means that grating lobes may occur. Also, as shown in Fig. 80, the antenna spacing between the third diagonal antenna group Rx#1 to #4 and the fourth diagonal antenna group Rx#5 to #8 in the receiving antenna 202 of Arrangement Example 2 is equal to or greater than one wavelength, which means that grating lobes may occur.

[0367] 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 grating lobes are suppressed to about -7.5 dB or less in directions different from the peak direction of the target true value direction.

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

[0370] For example, (a) of Figure 83 shows an antenna arrangement (hereinafter referred to as "comparative arrangement 2a") in which the first oblique antenna group Tx#1 to #3 and the third oblique antenna group Rx#1 to #4 of Arrangement Example 2 shown in Figure 80 are used for comparison with Arrangement Example 2. (b), (c), and (d) of Figure 83 show direction estimation results using the beamformer method in the antenna arrangement shown in (a) of Figure 83. (b), (c), and (d) of Figure 83 plot the output of the direction-of-arrival estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically, as in Figure 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 Figure 84 shows an antenna arrangement (hereinafter referred to as "comparative arrangement 2b") in which the second oblique antenna group Tx #4 to #6 and the fourth oblique antenna group Rx #5 to #8 of Arrangement Example 2 shown in Figure 80 are used, for comparison with Arrangement Example 2. (b), (c), and (d) of Figure 84 show direction estimation results using the beamformer method in the antenna arrangement shown in (a) of Figure 84. (b), (c), and (d) of Figure 84 plot the output of the direction-of-arrival estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically, as in Figure 82.

[0373] 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] 85(a) shows an antenna arrangement in which the first oblique antenna group Tx#1-#3 and the fourth oblique 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. Similarly to FIG. 82, (b), (c), and (d) of FIG. 85 plot the output of the direction-of-arrival estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0375] 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] 86(a) shows an antenna arrangement (hereinafter referred to as "comparative arrangement 2d") in which the first oblique antenna group Tx#4 to #6 and the third oblique antenna group Rx#1 to #4 of Arrangement Example 2 shown in FIG. 80 are used 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. Similarly to FIG. 82, (b), (c), and (d) of FIG. 86 plot the output of the direction-of-arrival estimation evaluation function value in a range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0377] 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 where a first group of diagonal antennas Tx#1 to #3 and a third group of diagonal antennas Rx#1 to #4 are used as in comparative arrangement 2a shown in FIG. 83(a), and a case where a second group of diagonal antennas Tx#4 to #6 and a fourth group of diagonal antennas Rx#5 to #8 are used as in comparative arrangement 2b shown in FIG. 84(a) will be described.

[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. Furthermore, 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), the horizontal and vertical two-dimensional angular directions in which grating lobes occur in comparison arrangement 2a and comparison arrangement 2b do not match and are shifted.

[0380] On the other hand, as shown in (b) of Figure 83 and (b) of Figure 84, 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] 80, in Arrangement Example 2 including the first to fourth oblique antenna groups, the directions (two-dimensional angular directions) of grating lobes that occur in comparison arrangement 2a including the first and third oblique antenna groups and grating lobes that occur in comparison arrangement 2b including the second and fourth oblique antenna groups do not match and tend to be dispersed. 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 (a) of FIG.

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

[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 (e.g., corresponding to the second diagonal antenna group). Furthermore, 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 (e.g., corresponding to the third diagonal antenna group). Therefore, as shown in Fig. 85(b) and Fig. 86(b), comparison arrangements 2c and 2d have the tendency that the horizontal and vertical two-dimensional angular directions in which grating lobes occur do not coincide with each other and are shifted.

[0384] On the other hand, as shown in (b) of Figure 85 and (b) of Figure 86, 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] 80, in Arrangement Example 2 including the first to fourth oblique antenna groups, the directions (two-dimensional angular directions) of the grating lobes that occur in comparison arrangement 2c including the first and fourth oblique antenna groups and the grating lobes that occur in comparison arrangement 2d including the second and third oblique antenna groups do not match and tend to be dispersed. 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 (a) of FIG.

[0386] Here, the virtual receiving array arrangement shown in FIG. 81 is the same as the virtual receiving array partially composed of virtual receiving arrays corresponding to the comparative arrangements 2a, 2b, 2c, and 2d. Therefore, the direction estimation result using the virtual receiving array arrangement shown in FIG. 81 suppresses grating lobes in directions different from the peak direction of the target true value direction, as shown in FIG. 82(a). In other words, in Arrangement Example 2, the angular directions in which grating lobes are generated by the multiple oblique antenna groups included in each of the transmitting antenna 106 and the receiving antenna 202 are dispersed in different directions. For this reason, in Arrangement Example 2, for example, as shown in FIG. 82(b), the normalized power value of the grating lobe is likely to be suppressed 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 peaks in directions different from the peak direction of the target true value direction are suppressed to approximately −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, as shown in Fig. 85(b) and Fig. 86(b), for example, 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 is larger.

[0389] Therefore, in Arrangement Example 2, when 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, for example, the closer the inclination of the oblique direction of each of the first to fourth oblique antenna groups is to 45 degrees with respect to the horizontal direction, the larger the spacing (or deviation) in the horizontal and vertical two-dimensional angular directions at which grating lobes occur is likely to become.

[0390] Furthermore, for example, if the arrangement directions of the first and second oblique antenna groups are not horizontally inverted symmetrical, or if the arrangement directions of the third and fourth oblique antenna groups are not horizontally inverted symmetrical, the closer the inclination of the oblique direction of each of the first to fourth oblique antenna groups is to 45 degrees with respect to the horizontal, the larger the spacing in the horizontal and vertical two-dimensional angular directions at which grating lobes occur is likely to be.

[0391] An antenna arrangement that increases the spacing between the horizontal and vertical two-dimensional angular directions in which grating lobes occur 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 used in direction estimation tends to be. Therefore, when the directions of 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, which can cause grating lobe power to overlap and increase the grating lobe power. Therefore, the fewer the number of antennas in 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 in the radar device 10 is small, for example, by using Arrangement Example 2 in which the arrangement directions of the first oblique antenna group and the second oblique antenna group are horizontally inverted symmetrical and the arrangement directions of the third oblique antenna group and the fourth oblique antenna group are horizontally inverted symmetrical, the overlap of grating lobe power can be suppressed, thereby improving the grating lobe suppression performance.

[0392] As described above, under placement condition 2, the transmitting antenna 106 includes a first group of oblique antennas arranged in a first oblique direction and a second group of oblique antennas arranged in a second oblique direction. Therefore, compared to placement condition 1, the vertical aperture length of the virtual receiving array can be further increased, and the vertical angle measurement accuracy or resolution of the radar device 10 can be improved.

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

[0394] For example, the same grating lobe suppression effect can be obtained even if the second and fourth diagonal antenna groups of comparison arrangement 2b are arranged at arbitrary locations relative to the first and third diagonal antenna groups of comparison arrangement 2a. Similarly, the same grating lobe suppression effect can be obtained even if the second and third diagonal antenna groups of comparison arrangement 2d are arranged at arbitrary locations relative to the first and fourth diagonal antenna groups of comparison arrangement 2c.

[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, and it is possible to arrange transmitting antenna elements with larger vertical sizes (for example, sizes of one wavelength or more).

[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, and it is possible to arrange receiving antenna elements with larger vertical sizes (for example, sizes of one wavelength or more).

[0397] Therefore, in arrangement example 2, the antenna elements of the transmitting antenna 106 and the receiving antenna 202 can be arranged in a diagonal line, 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] Note that the same virtual receiving array layout can be configured even if the relative positional relationship between the transmitting antenna 106 and the receiving antenna 202 is different in the layout of the virtual receiving array. Therefore, the positional relationship between the transmitting antenna 106 and the receiving antenna 202 is not limited to the example of the antenna layout shown in Fig. 80, and may be set arbitrarily. This also applies to other layout 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 shifted horizontally so as not to overlap vertically.

[0399] As described above, in Arrangement Example 2, the radar device 10 includes a transmitting antenna 106 that includes, for example, a first group of oblique antennas arranged in a first oblique direction and a second group of oblique antennas arranged in a second oblique direction. The receiving antenna 202 includes, for example, a third group of oblique antennas arranged in a third oblique direction and a fourth group of oblique antennas arranged in a fourth oblique direction. In the antenna arrangement of the radar device 10, the first and second oblique directions are different from each other, and the third and fourth oblique directions 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] Furthermore, in Arrangement Example 2, as described above, a grating lobe suppression effect can be obtained by differentiating the arrangement directions of the first to fourth oblique antenna groups in the transmitting antenna 106 and the receiving antenna 202. Therefore, in Arrangement Example 2, for example, the element spacing of the transmitting antenna 106 and the receiving antenna 202 can be set arbitrarily. This makes it possible to increase the aperture length of the virtual receiving array depending on the setting of at least one of the element spacing of the transmitting antenna 106 and the element spacing of the receiving antenna 202, thereby improving the angle measurement accuracy and angle separation performance in the vertical and horizontal directions of the radar device 10.

[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 grating lobes.

[0403] In Arrangement Example 2, at least one of the transmitting antenna 106 and the receiving antenna 202 may further include an antenna element in the antenna configuration shown in Fig. 80. In other words, it is sufficient that each of the transmitting antenna 106 and the receiving antenna 202 of the radar device 10 includes 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, by adding an antenna element to at least one of the transmitting antenna 106 and the receiving antenna 202, another virtual antenna is added to the virtual receiving array arrangement shown in Fig. 80. Even in the case of an antenna arrangement including Arrangement Example 2, the effects of Arrangement Example 2 described above can be maintained, and effects similar to those of Arrangement Example 2 can be obtained.

[0404] For example, an antenna may be added to the antenna configuration of Arrangement Example 2. Adding 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. Note that adding an antenna can be similarly applied to the following 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 and vertical directions are swapped may be applied. In this case, the virtual receiving array arrangement is obtained by swapping the horizontal and vertical directions, and angular separation performance is obtained by swapping the horizontal and vertical directions. Note that swapping the horizontal and vertical directions 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 and vertical directions.

[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, and therefore similar effects 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 other arrangement examples or modified examples.

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

[0408] In the example shown in Figure 87, the number of transmitting antennas is N Tx is six (for example, Tx#1, Tx#2, Tx#3, Tx#4, Tx#5, and Tx#6), and the number of receiving antennas Na is eight (for example, 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 oblique antennas Tx#1 to #3 arranged in a first oblique direction and a second group of oblique antennas Tx#4 to #6 arranged in a second oblique direction. In Fig. 87, the first oblique direction and the second oblique direction are not parallel to each other but are different directions from each other.

[0410] 87, Na=8 receiving antennas Rx#1 to #8 include a third group of oblique antennas Rx#1 to #4 arranged in a third oblique direction and a fourth group of oblique antennas Rx#5 to #8 arranged in a fourth oblique direction. In Fig. 87, the third oblique direction and the fourth oblique 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. 87 satisfies arrangement condition 2.

[0412] 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, as shown in Fig. 87. 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, as shown in Fig. 87. That is, in Fig. 87, the first diagonal direction and the fourth diagonal direction are aligned in the same direction, and the second diagonal direction and the third diagonal direction are aligned in 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 shifted horizontally by two wavelengths from left to right in the figure, and are simultaneously shifted upward by two wavelengths in the vertical direction. The second diagonal antenna group Tx#4-#6 shown in Fig. 87 are shifted horizontally by two wavelengths from left to right in the figure, and are simultaneously shifted downward by two wavelengths 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 in a horizontally inverted symmetrical manner.

[0415] Here, the transmitting antennas 106 in Arrangement Example 1 (for example, FIG. 8) are arranged in the horizontal direction. On the other hand, the transmitting antennas 106 in Arrangement Example 2a are arranged in the diagonal direction as shown in FIG. 87. In other words, since the transmitting antennas 106 in Arrangement Example 2a are arranged two-dimensionally, horizontally and vertically, the aperture in the vertical direction can be enlarged more in Arrangement Example 2a than in Arrangement Example 1.

[0416] Also, for example, the third diagonal antenna group Rx#1-#4 shown in Fig. 87 are shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths, and are simultaneously shifted upward in the vertical direction at intervals of 0.5 wavelengths. Also, the fourth diagonal antenna group Rx#5-#8 shown in Fig. 87 are shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths, and are simultaneously shifted upward 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 in a horizontally inverted symmetrical manner.

[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 that make up the virtual receiving array antenna are calculated using equation (16).

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

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

[0420] 89(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. Also, FIG. 89(b) is a diagram showing the normalized power values ​​in a grayscale color map, similar to FIG. 89(a), with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values. Also, FIG. 89(c) is a diagram showing the normalized power values ​​in a grayscale color map, similar to FIG. 89(a), with the horizontal axis being the vertical direction and the vertical axis being the normalized power values. Note that 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 that include many intervals that are 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 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 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, with the inclination of the first to fourth oblique directions being 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 angular directions where grating lobes occur are the widest.

[0423] An antenna arrangement that increases the spacing between the horizontal and vertical two-dimensional angular directions in which grating lobes occur 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 beamwidth of the main beam used in direction estimation tends to be. Therefore, when the directions of grating lobes to be suppressed are close to each other, the fewer the number of antennas in the radar device 10, the wider the beamwidth, which can cause grating lobe power to overlap and increase the grating lobe power. Therefore, the fewer the number of antennas in 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 in the radar device 10 is small, for example, Arrangement Example 2, in which the arrangement directions of the first oblique antenna group and the second oblique antenna group are horizontally inverted symmetrical and the arrangement directions of the third oblique antenna group and the fourth oblique antenna group are horizontally inverted symmetrical, can suppress the overlap of grating lobe power and improve the grating lobe suppression performance.

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

[0425] In addition, in arrangement example 2a, as shown in Figure 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, similar to Arrangement Example 2, antenna elements of any lengthwise (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 MIMO antenna arrangement) of the transmitting antenna 106 (eg, represented as Tx) and the receiving antenna 202 (eg, represented as Rx) according to arrangement example 2b.

[0429] In the example shown in Figure 90, the number of transmitting antennas is N Tx is six (for example, Tx#1, Tx#2, Tx#3, Tx#4, Tx#5, and Tx#6), and the number of receiving antennas Na is eight (for example, 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 oblique antennas Tx#1 to #3 arranged in a first oblique direction and a second group of oblique antennas Tx#4 to #6 arranged in a second oblique direction. In Fig. 90, the first and second oblique directions are not parallel to each other but are different oblique directions.

[0431] 90, Na=8 receiving antennas Rx#1 to #8 include a third group of oblique antennas Rx#1 to #4 arranged in a third oblique direction and a fourth group of oblique antennas Rx#5 to #8 arranged in a fourth oblique direction. In FIG. 90, the third oblique direction and the fourth oblique 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. 90 satisfies arrangement condition 2.

[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 when either the first diagonal direction or the second diagonal direction is set to have an inclination that matches the third diagonal direction or the fourth diagonal direction, arrangement condition 2 is satisfied.

[0435] For example, the first diagonal antenna group Tx#1-#3 shown in Fig. 90 are shifted horizontally by two wavelengths from left to right in the figure, and are simultaneously shifted upward by two wavelengths in the vertical direction. The second diagonal antenna group Tx#4-#6 shown in Fig. 90 are shifted horizontally by two wavelengths from left to right in the figure, and are simultaneously shifted downward by two wavelengths 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 in a horizontally inverted symmetrical manner.

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

[0437] Also, for example, the third diagonal antenna group Rx#1-#4 shown in Fig. 90 are shifted horizontally from right to left in the figure at intervals of 0.5 wavelengths, and are simultaneously shifted upward in the vertical direction at intervals of 0.5 wavelengths. Also, the fourth diagonal antenna group Rx#5-#8 shown in Fig. 90 are shifted horizontally from left to right in the figure at intervals of 0.5 wavelengths, and are simultaneously shifted upward 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 not arranged in a horizontally inverted symmetrical manner.

[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 that make up the virtual receiving array antenna are calculated using equation (16).

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

[0440] Figure 92 shows the MIMO array layout of layout 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 range of ±90 degrees in the horizontal direction and a range of ±90 degrees in the vertical direction when the target true value is set to 0 degrees horizontally and 0 degrees vertically.

[0441] 92(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. Also, FIG. 92(b) is a diagram showing the normalized power values ​​in a grayscale color map, similar to FIG. 92(a), with the horizontal axis being the horizontal direction and the vertical axis being the normalized power values. Also, FIG. 92(c) is a diagram showing the normalized power values ​​in a grayscale color map, similar to FIG. 92(a), with the horizontal axis being the vertical direction and the vertical axis being the normalized power values. 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 such that grating lobes can occur. In contrast, as shown in Fig. 92, it can be seen that grating lobes are suppressed to approximately -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 oblique antenna group and the arrangement direction of the fourth oblique antenna group do not match but are different directions, while the arrangement direction of the second oblique antenna group matches and is parallel to the arrangement direction of the third oblique antenna group. In this way, even if either the first oblique direction or the second oblique direction has an inclination that matches the third oblique direction or the fourth oblique 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 Figure 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, similar to Arrangement Example 2, antenna elements of any lengthwise (e.g., vertical) size can be applied to 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, Modifications 1 to 4, 6, and 7 of Arrangement Example 1 may be similarly applied to the receiving antennas of Arrangement Example 2 (or Arrangement Examples 2a and 2b). Even when Modifications 1 to 4, 6, and 7 of Arrangement Example 1 are applied to Arrangement Example 2, the same effects as those of Arrangement Example 2 can be obtained. For example, in the descriptions of Modifications 1 to 4, 6, and 7 of Arrangement Example 1, "Arrangement Example 1" may be replaced with "Arrangement Example 2," and further, the "first diagonal antenna group" and the "second diagonal antenna group" of Arrangement Example 1 may be replaced (read as) with the "third diagonal antenna group" and the "fourth diagonal antenna group" of Arrangement Example 2, respectively. In this way, Arrangement Example 2 can also obtain the same effects as those of Modifications 1 to 4, 6, and 7 of Arrangement Example 1. Note that a description of the same applications of Modifications 1 to 4, 6, and 7 of Arrangement Example 1 to Arrangement Example 2 will be omitted.

[0448] Below, additional parts will be described for the case where 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 "second diagonal antenna group" included in transmitting antenna 106 of Arrangement Example 2.

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

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

[0451] For example, in the case of Arrangement Example 2, as shown in FIG. 80, the minimum distance between the first diagonal antenna group and the second diagonal antenna group (for example, the distance between Tx#3 and Tx#4) is N a The spacing is set to be narrower than the horizontal aperture length of the receiving antennas 202 (for example, the spacing between Rx#4 and Rx#8). In the first modification of the second arrangement example, for example, the minimum spacing between the first diagonal antenna group and the second diagonal antenna group (for example, the spacing between Tx#3 and Tx#4) is set to be N 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 increasing the minimum distance between the first oblique antenna group and the second oblique antenna group, the peak of the target true value direction in the horizontal direction becomes sharper, thereby improving the horizontal angle measurement accuracy or estimation accuracy of the radar device 10. Note that in Modification 1 of Arrangement Example 2, similarly to Modification 1 of Arrangement Example 1, the side lobe level to the side (horizontal direction) of the peak of the target true value direction may increase, so the distance (e.g., minimum distance) between the first oblique antenna group and the second oblique antenna group 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 distance (e.g., the minimum distance) 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 the first diagonal antenna group and the second diagonal antenna group may overlap.

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

[0455] In a 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 distance between them (the distance between Tx#3 and Tx#4) is even closer.

[0456] Alternatively, in Modification 2 of Arrangement Example 2, for example, the antennas of 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 Example 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 oblique antenna group and the second oblique 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 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 in horizontally inverted symmetry, but this is not limiting, 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 first diagonal direction and the second diagonal direction may be different directions, not parallel. This provides the same effect as 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 spacings may be set in 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 any two or three of the above-mentioned arrangements: a) an arrangement in which the first diagonal antenna group and the second diagonal antenna group have asymmetric inclinations; b) an arrangement in which the first diagonal antenna group and the second diagonal antenna group each include a different number of antennas; and c) an arrangement in which the positions of the first diagonal antenna group and the second diagonal antenna group are shifted in the vertical direction.

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

[0465] In addition, the above-described 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 (referred to as "Arrangement Example 2-4a") in which the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 are arranged with symmetrical 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 asymmetrical inclinations in the horizontal direction. Even in Arrangement Example 2-4a, the same effects as in Arrangement Example 2 can be obtained.

[0467] 94 shows an example (referred to as "Arrangement Example 2-4b") in which the first diagonal antenna group Tx#1-#3 and the second diagonal antenna group Tx#4-#6 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 symmetry in the horizontal direction. Even in Arrangement Example 2-4b, the same effects as in Arrangement Example 2 can be obtained.

[0468] 95 shows an example (e.g., referred to as "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 Arrangement Example 2-4c, the same effects as those in Arrangement Example 2 can be obtained.

[0469] In addition, under arrangement condition 2, either the first diagonal direction or the second diagonal direction may be arranged horizontally. In addition, under 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 (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 third diagonal antenna group Rx#1-#4 and the fourth diagonal antenna group Rx#5-#8 are arranged in a horizontally inverted symmetrical manner. In this way, even if either the first diagonal direction or the second diagonal direction is arranged in a 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, but 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 also provides the same effect as in Arrangement Example 2.

[0473] [Modification 7 of Arrangement Example 2] In the seventh modification of the second arrangement example, for example, the multi-stage configuration of the antenna arrangement described in the second arrangement example and the first to fourth and sixth modifications of the second arrangement example 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 vertical stages or two horizontal stages, and a configuration in which the third and fourth diagonal antenna groups included in receiving antenna 202 are arranged in two vertical stages or two horizontal stages. 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 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, a 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, a 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.

[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-range (LR) antenna element may be used in the first stage, and a short-range (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-range (LR) antenna element may be used in the first stage, and a short-range (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 antenna 106 and the second stage transmitting antenna 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 with 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 above describes the modified example of Arrangement Example 2.

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

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

[0484] That is, N Tx Among 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 spacing 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 at intervals of dTV2×D V 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 interval of dRH2×D H and shifts vertically at intervals of dRV2×D V 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 arranged symmetrically in the horizontal direction. Also, for example, when dRH1≠dRH2 or dRV1≠dRV2, the third and fourth diagonal antenna groups are arranged asymmetrically in the horizontal direction.

[0489] In Arrangement Example 2 and the modified example of Arrangement Example 2, the tilt 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] [Example of minimum antenna configuration and layout with few antennas for layout condition 2] Below, we will explain the 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 under placement condition 2 (number of transmitting antennas N Tx 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 addition, in FIG. 97, the scales of the horizontal and vertical axes are, for example, D H , D V Let's say.

[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 Figs. 98 to 101 shows an example of a MIMO antenna arrangement, and (b) of Figs. 98 to 101 show an example of a virtual receiving array arrangement configured using the MIMO antenna arrangement shown in (a) of Figs. 98 to 101. In Figs. 98 to 101, the scales of the horizontal and vertical axes are, for example, D H , D V Let's say.

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

[0496] For example, in the antenna arrangement example shown in 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] Furthermore, for example, in the antenna arrangement example 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 the antenna mounting area can be reduced.

[0498] 100 and 101 show the case where the number of transmitting antennas is N Tx 100 and 101 show examples of antenna arrangements when the number of receiving antennas Na=4 and the number of receiving antennas Na=4. In Figures 100 and 101, the first diagonal antenna group includes Tx#1 and Tx#2, the second diagonal antenna group includes Tx#3 and Tx#4, the third diagonal antenna group includes Rx#1 and Rx#2, and the fourth diagonal antenna group includes Rx#3 and Rx#4.

[0499] For example, in the antenna arrangement examples shown in FIGS. 100 and 101, even 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 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, although the case where the arrangement directions (e.g., diagonal directions) of the receiving antenna 202 are two different directions in arrangement condition 1 (e.g., FIG. 8) has been described, the arrangement directions of the receiving antenna 202 may be three or more different directions. Similarly, although the case where 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) has been described, 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, and therefore, 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] Furthermore, 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 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 individually located at physically separate locations. Also, in a radar receiver according to an embodiment of the present disclosure, the direction estimator and other components may be individually located at physically separate locations.

[0506] Although not shown, a 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 the above-described 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 on a single chip, or a single chip may include 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 conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the disclosure.

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

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

[0510] Furthermore, 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 controls each functional block used in the description of the above embodiments and may have input and output terminals. These may be individually integrated into single chips, or some or all of them may be integrated into a single chip. While the term LSI is used here, it may also be called an IC, system LSI, super LSI, or ultra LSI depending on the level of integration.

[0511] Furthermore, the method of integration is not limited to LSI, but may be realized using a dedicated circuit or a general-purpose processor. It is also possible to use 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.

[0512] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology may be used to integrate functional blocks. The application of biotechnology, etc. 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 both the first direction and the second direction, with a spacing between adjacent antennas being equal to or greater than 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-ahead direction of the vehicle and a direction perpendicular to the straight-ahead direction of the vehicle.

[0515] In one embodiment of the present disclosure, the first direction and the second direction are different from a vertical direction, which is the 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, the minimum spacing between the first antenna group and the second antenna group is greater than the aperture length of the third antenna group.

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

[0519] In an embodiment of the present disclosure, the arrangement of the antennas included in the first antenna group and the arrangement of the antennas 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 included 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 included in the second antenna group in the vertical direction is dRV×D V and D H and the above 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 dRH1 and dRH2 are each a value of 1 or more.

[0521] In one 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 one embodiment of the present disclosure, in at least one of the third antenna group, the first antenna group, and the second antenna group, the 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 one 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 with 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 an 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 from 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 of the third antenna group in the horizontal direction is dTH1×D H and the spacing between adjacent antennas included 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 included in the fourth antenna group in the vertical direction is dTV2×D V and the interval between adjacent antennas included in the first antenna group in the horizontal direction is dRH1×D H and the spacing between adjacent antennas included in the first antenna group in the vertical direction is dRV1×D V and the interval between adjacent antennas included in the second antenna group in the horizontal direction is dRH2×D H and the spacing between adjacent antennas included in the second antenna group in the vertical direction is dRV2×D V and D H and the above D Vis a value within a 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 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, with an interval 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, with an interval between adjacent antennas being one or more wavelengths of the transmission signal, and the third direction is the same direction as the first direction, and the fourth direction is the same direction 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 Unit 207 AD conversion section 208 Beat Frequency Analysis Unit 209 Output switching unit 210 Doppler analysis unit 211 CFAR Department 212 Code demultiplexer 213 Direction estimation part

Claims

1. a transmitting circuit that transmits a transmission signal using a plurality of transmitting antennas; a receiving circuit that receives, using a plurality of receiving antennas, reflected wave signals resulting from the transmission signals being reflected by an object; Equipped with 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; the remaining one of the plurality of transmitting antennas or the plurality of receiving antennas includes a third antenna group, the spacing between adjacent antennas being equal to or greater than one wavelength of the transmission signal, and arranged in a third direction, and a fourth antenna group, the spacing between adjacent antennas being equal to or greater than one wavelength of the transmission signal, and arranged in a fourth direction different from the third direction; the third direction is the same as the first direction, The fourth direction is different from the second direction. 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 that is a height direction of the vehicle and a horizontal direction that is a straight traveling direction of the vehicle and a direction perpendicular to the straight traveling 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 the 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. One of the third direction and the fourth direction is a direction that coincides with the horizontal direction. The radar device according to claim 2 or 3.

5. the third direction and the fourth direction are different directions from the horizontal direction and the vertical direction, The radar device according to claim 2 or 3.

6. a minimum distance between the first antenna group and the second antenna group is greater than an aperture length of the third antenna group or the fourth antenna group; The radar device according to claim 1 .

7. the first antenna group and the second antenna group include one or more shared antennas; The radar device according to claim 1 .

8. the third antenna group and the fourth antenna group include one or more shared antennas; The radar device according to claim 1 .

9. the arrangement of the antennas included in the first antenna group and the arrangement of the antennas included in the second antenna group are in a line-symmetric relationship with respect to the vertical direction; The radar device according to claim 2 or 3.

10. a distance between adjacent antennas included in the first antenna group in the horizontal direction is a first integer multiple of D; a distance between adjacent antennas included in the second antenna group in the horizontal direction is a second integer multiple of D; a distance between adjacent antennas in the third antenna group in the horizontal direction is a third integer multiple of D; a spacing between adjacent antennas in the fourth antenna group in the horizontal direction is a fourth integer multiple of D; a spacing between adjacent antennas included in the first antenna group in the vertical direction is a fifth integer multiple of DV; a spacing between adjacent antennas included in the second antenna group in the vertical direction is a sixth integer multiple of DV; a spacing between adjacent antennas included in the third antenna group in the vertical direction is a seventh integer multiple of DV; a spacing between adjacent antennas included in the fourth antenna group in the vertical direction is an eighth integer multiple of DV; The DH and the DV are values ​​within a range of 0.45 to 0.8 times the wavelength of the transmission signal. The radar device according to claim 2 or 3.

11. In each of the first antenna group, the second antenna group, the third antenna group, and the fourth antenna group, adjacent antennas are spaced equally apart. The radar device according to claim 1 .

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

13. 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 .

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

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