Radar device and radar signal processing method

Abstract

In a radar apparatus in a radar apparatus and a radar signal processing method, an r1th antenna and an r2th antenna in a first antenna group are disposed adjacent to each other in a third direction different from a first direction and a second direction, and a t1th antenna and a t2th antenna in a second antenna group are disposed adjacent to each other in the third direction. The r3-th antenna in the first antenna group is disposed at a position shifted from the third direction to the first direction and the second direction by an offset amount greater than a prescribed value based on the wavelength of the transmission signal, and the absolute value of the difference between the two intervals is the prescribed value, or the absolute value of the difference between the two intervals is the prescribed value. The absolute value of the difference between the two intervals is an integer multiple of two or more times of a prescribed value, one of the two intervals is a prescribed value, and the two intervals are the interval between the r1-th antenna and the r2-th antenna and the interval between the t1-th antenna and the t2-th antenna.

Description

Technical Field

[0001] This disclosure relates to radar devices and radar signal processing methods. Background Technology

[0002] In recent years, research has been advancing on radar devices that utilize short-wavelength radar signals capable of transmitting high-resolution microwave or millimeter-wave signals. Furthermore, to improve safety outdoors, there is a demand for radar devices that can detect not only vehicles but also small objects such as pedestrians over a wide field of view (e.g., wide-angle radar devices).

[0003] As a radar device with a wide-angle detection range, there is a structure that uses a method called Direction of Arrival (DOA) estimation, which receives reflected waves from a target (or object) through an array of antennas consisting of multiple antennas (or antenna elements), and estimates the direction of arrival (also known as the angle of arrival) of the reflected waves based on the received phase difference with respect to the element spacing (antenna spacing).

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

[0005] In addition, as a radar device, for example, a structure has been proposed (sometimes also called "MIMO (Multiple Input Multiple Output) radar") in which multiple antennas (array antennas) are provided in the transmitter in addition to the receiver, and beam scanning is performed by using signal processing of the transceiver array antennas (for example, see Non-Patent Document 1).

[0006] Existing technical documents

[0007] Non-patent literature

[0008] Non-patent literature 1: J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007

[0009] Non-patent literature 2: Kazuo Shirakawa et al., "3D-Scan Millimeter-Wave Radar for Automotive Application", Fujitsu Ten technical report, Vol.30, No.1, 2012.

[0010] Non-patent literature 3: M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823

[0011] Non-patent literature 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

[0012] However, there is still room for research into methods to improve the angle measurement accuracy or resolution of radar devices (e.g., MIMO radar).

[0013] The non-limiting embodiments disclosed herein help to provide radar devices and radar signal processing methods that can improve angle measurement accuracy or resolution.

[0014] A radar device according to an embodiment of this disclosure includes: a transmitting circuit that transmits a transmitting signal using one of a first antenna group and a second antenna group; and a receiving circuit that receives a reflected wave signal of the transmitted signal reflected from an object using the other of the first antenna group and the second antenna group. The r1 and r2 antennas in the first antenna group are arranged adjacent to each other in a third direction, which is different from a first direction and different from a second direction orthogonal to the first direction. The t1 and t2 antennas in the second antenna group are arranged adjacent to each other in the third direction. The r3 antenna in the first antenna group is located at a position offset from the third direction towards both the first and second directions by an amount greater than a predetermined value based on the wavelength of the transmitted signal, wherein the absolute value of the difference between two intervals is the predetermined value, or the absolute value of the difference between the two intervals is an integer multiple of twice or more of the predetermined value and one of the two intervals is the predetermined value, wherein the two intervals are the interval between the r1 and r2 antennas and the interval between the t1 and t2 antennas.

[0015] Furthermore, these broad or specific embodiments can be implemented by systems, apparatuses, methods, integrated circuits, computer programs, or recording media, or by any combination of systems, apparatuses, methods, integrated circuits, computer programs, and recording media.

[0016] According to one embodiment of this disclosure, the angle measurement accuracy or resolution of a radar device can be improved.

[0017] Further advantages and effects of one embodiment of this disclosure will be clearly presented by the specification and accompanying drawings. These advantages and / or effects are provided by various embodiments and the features described in the specification and drawings, but not all of them need to be provided to obtain one or more of the same features. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0019] Figure 2 This is a diagram showing an example of the direction estimation result.

[0020] Figure 3 This is a diagram showing an example of the direction estimation result.

[0021] Figure 4 This is a diagram showing an example of the direction estimation result.

[0022] Figure 5 This is a block diagram illustrating an example of the structure of a radar device.

[0023] Figure 6 This is a diagram illustrating an example of the transmitted and reflected wave signals when using a chirped pulse.

[0024] Figure 7 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0025] Figure 8 This is a diagram showing an example of the direction estimation result.

[0026] Figure 9 This is a diagram showing an example of a MIMO antenna configuration.

[0027] Figure 10 This is a diagram illustrating an example of the structure of a subarray.

[0028] Figure 11 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0029] Figure 12 This is a diagram showing an example of the direction estimation result.

[0030] Figure 13 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0031] Figure 14 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0032] Figure 15 This is a diagram showing an example of the direction estimation result.

[0033] Figure 16 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0034] Figure 17 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0035] Figure 18 This is a diagram showing an example of the direction estimation result.

[0036] Figure 19 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0037] Figure 20 This is a diagram illustrating an example of the configuration of a MIMO antenna and a virtual receiving antenna.

[0038] Explanation of reference numerals in the attached figures

[0039] 10. Radar Equipment

[0040] 100 Radar Transmission Unit

[0041] 101 Radar Transmitting Signal Generation Unit

[0042] 102 Modulation signal generation unit

[0043] 103VCO

[0044] 104 code generation department

[0045] 105 Phase Rotation Unit

[0046] 106 transmitting antennas

[0047] 200 Radar Receiving Unit

[0048] 201 Antenna System Processing Department

[0049] 202 Receiving Antenna

[0050] 203 Receiving Wireless Unit

[0051] 204 Mixer Section

[0052] 205LPF

[0053] 206 Signal Processing Department

[0054] 207 AD Conversion Section

[0055] 208 Beat Frequency Analysis Department

[0056] 209 Output Switching Unit

[0057] 210 Doppler Analysis Department

[0058] 211CFAR Department

[0059] Demultiplexing unit of 2^12 code multiplexing

[0060] 213 Direction Estimation Department Detailed Implementation

[0061] MIMO radar, for example, transmits signals (radar transmit waves) multiplexed using time division, frequency division, Doppler division, or code division from multiple transmit antennas (or, referred to as "transmit array antennas"). Furthermore, MIMO radar, for example, uses multiple receive antennas (or, referred to as "receive array antennas") to receive signals reflected from surrounding objects (radar reflect waves), and demultiplexes these received signals to receive the multiplexed transmit signal. Through this processing, MIMO radar can acquire the propagation path response represented by the product of the number of transmit antennas and the number of receive antennas, and perform array signal processing on these received signals as a virtual receive array.

[0062] In MIMO radar, by studying and adjusting the configuration of the antenna elements of the transmit and receive array antenna, it is possible to construct a virtual receive array antenna (hereinafter referred to as a virtual receive array, MIMO virtual receive array, virtual receive antenna, or virtual receive array antenna) that is equal to the product of the number of transmit antenna elements and the number of receive antenna elements. This allows for an increase in the effective aperture length of the array antenna with a smaller number of elements, thereby improving angular measurement accuracy or resolution.

[0063] In addition to one-dimensional scanning (angle measurement) in the vertical or horizontal direction, MIMO radar can also be applied when performing two-dimensional beam scanning (angle measurement) in both the vertical and horizontal directions (for example, see Non-Patent Document 2).

[0064] Two-dimensional angle measurement can be used, for example, for obstacle detection in ADAS (Advanced Driver Assistance Systems) applications that require height information, thereby improving radar detection performance. On the other hand, two-dimensional angle measurement uses antennas arranged in two dimensions, both vertically and horizontally, thus requiring more antennas compared to one-dimensional angle measurement.

[0065] For example, it is anticipated that improving the accuracy of two-dimensional angle measurement in MIMO radars with fewer antennas will reduce the cost of high-performance radar detection systems. Additionally, it is anticipated that expanding the coverage area by using multiple MIMO radars with fewer antennas will reduce the cost of ADAS systems that monitor the entire surroundings, such as vehicles.

[0066] In one non-limiting embodiment of this disclosure, a method (e.g., antenna configuration) for improving the two-dimensional angle measurement accuracy of a MIMO radar configured with a relatively small number of antennas (a limited number of antennas, for example, two transmit antennas and three receive antennas) is described.

[0067] Figure 1 This is an example of the configuration of the transmitting and receiving antennas of a MIMO radar (hereinafter also referred to as the MIMO antenna configuration) and the configuration of the virtual receiving antenna. Figure 1 (a) indicates in the vertical direction (in) Figure 1 (a) shows two transmitting antennas (Tx#1 to Tx#2) arranged longitudinally, and in the horizontal direction (in Figure 1 In (a), three receiving antennas (Rx#1 to Rx#3) are arranged horizontally. Figure 1 In (a), the transmitting antennas are spaced equally (D) in the vertical direction. V The receiving antennas are configured with equal intervals (D) in the horizontal direction. H Configuration.

[0068] Figure 1 (b) indicates based on Figure 1 The virtual receiving antenna is configured based on the antenna configuration shown in (a). Furthermore, the virtual receiving antenna configuration based on the MIMO antenna configuration is, for example, as disclosed in Non-Patent Document 1. For example, Figure 1 The virtual receiving antenna shown in (b) consists of six virtual antennas (VA#1 to VA#6) arranged in a rectangle, with three antennas arranged horizontally and two antennas arranged vertically. Figure 1 In (b), the element spacing in the horizontal and vertical directions of the virtual receiving antenna is D, respectively. H D V The horizontal and vertical aperture lengths A of the virtual receiver array. H A V A respectively H =3D H A V =D V .

[0069] Figure 2 Indicates in Figure 1 In the antenna configuration of the MIMO radar shown in (a), the element spacing is set to horizontally. H =0.5λ, vertical component spacing D V When =0.5λ, use Figure 1 (b) shows the angle measurement results based on the two-dimensional Fourier method for the received signal of the virtual receiving antenna with respect to an object in the horizontal and vertical directions of 0°. Furthermore, it is assumed that each antenna is omnidirectional. Figure 2 The diagram shows the spatial distribution of normalized received power in the horizontal and vertical directions, with the peak direction of received power representing the target direction based on two-dimensional angle measurement. Additionally, λ represents the wavelength of the radar carrier.

[0070] like Figure 2 As shown, the main beam (main lobe) is formed in the horizontal and vertical directions at 0° to detect the target orientation. Here, the narrower (smaller) the beamwidth of the main beam, the higher the angle measurement accuracy and the better the angle resolution performance for multiple targets. For example, in... Figure 2 In the middle, the 3dB beamwidth (power half-amplitude) in the horizontal direction is about 37°, and the 3dB beamwidth (power half-amplitude) in the vertical direction is about 59°.

[0071] In two-dimensional angle measurement of MIMO radar with a limited number of antennas (e.g., a restricted number of antennas), the horizontal and vertical aperture lengths cannot be adequately guaranteed, and the accuracy of two-dimensional angle measurement can easily become insufficient. For example, in Figure 1In the example of the antenna configuration, because the vertical aperture is smaller than the horizontal aperture, the 3dB beamwidth in the vertical direction tends to be larger, and the angular measurement accuracy in the vertical direction tends to be lower than that in the horizontal direction. Additionally, for example, in... Figure 1 If the vertical antenna spacing is increased, the 3dB beamwidth in the vertical direction will decrease. Although the angle measurement accuracy will improve, grating lobes may be generated.

[0072] For example, Figure 3 Indicates in Figure 1 In the antenna configuration of the MIMO radar shown in (a), the antenna spacing D in the vertical direction is... V =0.7λ, horizontal antenna spacing D H When =0.5λ, it was used Figure 1 Example of angle measurement results based on two-dimensional Fourier method for the received signal of the virtual receiving antenna in (b). Figure 3 The example shows the angle measurement results based on the two-dimensional Fourier method for an object in a horizontal direction of 0° and a vertical direction of 40°. For example... Figure 3 As shown, the main lobe is formed in the horizontal 0° and vertical 40° direction to detect the object orientation. On the other hand, as... Figure 3 As shown, grating lobes (horizontal 0° and vertical -51°) are generated outside the main beam. Figure 3 In radar, the peak level of the grating lobe is at the same level as the peak level of the main beam, making it difficult to distinguish the true direction of the target in radar devices.

[0073] Similarly, for example, Figure 4 Indicates in Figure 1 In the antenna configuration of the MIMO radar shown in (a), the antenna spacing D in the vertical direction is... V =λ, horizontal antenna spacing D H When =0.5λ, it was used Figure 1 Example of angle measurement results based on two-dimensional Fourier method for the received signal of the virtual receiving antenna in (b). Figure 4 Examples and Figure 3 Similarly, this represents the angle measurement results based on the two-dimensional Fourier method for an object in a horizontal direction of 0° and a vertical direction of 40°. For example... Figure 4 As shown, grating lobes are also generated along with the main lobe oriented towards the target direction (0° horizontally and 40° vertically). Figure 4 In the example, with Figure 3 In comparison, the angular spacing between the main lobe and the grating lobe becomes smaller. According to Figure 3 and Figure 4 The following can be confirmed: the antenna spacing D in the vertical direction V The larger the value, the smaller the angular spacing of the generated grating lobes.

[0074] Here, the antenna spacing D in the vertical direction V =0.7λ, horizontal antenna spacing D H With a beamwidth of 0.5λ, the 3dB beamwidth (power half-amplitude) for targets at 0° horizontally and 0° vertically is approximately 37° horizontally and approximately 41° vertically. Furthermore, with the antenna spacing D set to the vertical direction... V =λ, horizontal antenna spacing D H With a beamwidth of 0.5λ, the 3dB beamwidth (power half-amplitude) for a target in both the horizontal and vertical directions is approximately 37° in the horizontal direction and approximately 29° in the vertical direction.

[0075] As mentioned above, increasing the vertical antenna spacing to greater than 0.5λ reduces the 3dB beamwidth and improves vertical angle measurement accuracy, but introduces grating lobes. For example, if the envisioned detection angle range is above the angle where grating lobes occur, the probability of the radar device mistakenly detecting spurious peaks caused by grating lobes within the detection angle range as targets increases, easily degrading the radar's detection performance. Furthermore, even if the grating lobes are outside the envisioned detection angle range, if the power of the reflected wave arriving from the direction of the grating lobes is sufficiently high, the radar device may still misdetect the target as having entered the field of view, easily degrading the radar's detection performance.

[0076] In addition, when the horizontal antenna spacing is increased, the horizontal beamwidth decreases, just like in the vertical case, which can improve the horizontal angle measurement accuracy or angular resolution. However, since the horizontal spacing is greater than 0.5 wavelengths, grating lobes are generated, which can easily degrade radar detection performance.

[0077] For example, an antenna configuration that can suppress grating lobes while increasing antenna spacing in the vertical or horizontal direction is desirable.

[0078] In one non-limiting embodiment of this disclosure, an antenna configuration that can increase element spacing and suppress grating lobes in at least one of the vertical and horizontal directions is described. By implementing such an antenna configuration, angular measurement accuracy or resolution can be improved with fewer antennas.

[0079] Furthermore, the radar device of one embodiment of this disclosure can be mounted on a mobile body such as a vehicle. The radar device mounted on a mobile body can also be used, for example, as an advanced driver assistance system (ADAS) to improve collision safety or as a sensor to monitor the surroundings of a mobile body during autonomous driving.

[0080] Additionally, the radar device of one embodiment of this disclosure can be installed on high structures such as roadside utility poles or traffic lights. Such a radar device can be used, for example, as a sensor in an auxiliary system to improve the safety of passing vehicles or pedestrians.

[0081] Furthermore, radar devices are not limited to this purpose and can also be used for other purposes.

[0082] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the embodiment, the same constituent elements are labeled with the same reference numerals, and their descriptions are omitted to avoid repetition.

[0083] The following describes a radar device with a structure in which the transmitting branch transmits different transmitted signals subject to code division multiplexing from multiple transmitting antennas, and the receiving branch demultiplexes each transmitted signal for reception processing (e.g., a MIMO radar structure). However, the structure of the radar device is not limited to this; it can also be a structure in which the transmitting branch transmits different transmitted signals subject to frequency division multiplexing from multiple transmitting antennas, and the receiving branch demultiplexes each transmitted signal for reception processing. Similarly, the radar device can also be a structure in which the transmitting branch transmits transmitted signals subject to time division multiplexing from multiple transmitting antennas, and the receiving branch performs reception processing.

[0084] Similarly, the transmission branch can transmit different transmitted signals that have undergone Doppler division multiplexing from multiple transmit antennas, and the receiving branch can demultiplex each transmitted signal for reception processing. Likewise, the transmission branch can transmit transmitted signals multiplexed by combining at least two of code division multiplexing, time division multiplexing, and Doppler division multiplexing from multiple transmit antennas, and the receiving branch can demultiplex each transmitted signal for reception processing.

[0085] Furthermore, the following description, as an example, illustrates a radar configuration using frequency-modulated pulse waves such as chirped pulses (e.g., also referred to as "fast chirp modulation"). However, the modulation method is not limited to frequency modulation. For example, one embodiment of this disclosure can also apply radar configurations utilizing single pulses or coded pulses.

[0086] [Structure of a radar device]

[0087] Figure 5 This is a block diagram illustrating a structural example of the radar device 10 according to this embodiment.

[0088] The radar device 10 includes a radar transmitter (transmitter branch) 100 and a radar receiver (receiver branch) 200.

[0089] The radar transmitter 100 generates radar signals (radar transmission signals) and uses multiple transmitting antennas 106 (e.g., N) to transmit the signals. tx A transmitting array antenna consisting of ( ) transmits radar signals at a specified transmission period.

[0090] The radar receiver 200 uses a receiver array antenna comprising multiple receiver antennas 202 (e.g., Na) to receive radar-transmitted signals, i.e., reflected wave signals, reflected from a target (object, not shown). The radar receiver 200 performs signal processing on the reflected wave signals received in each receiver antenna 202, such as detecting the presence or absence of an object, or estimating the arrival distance, Doppler frequency (e.g., relative velocity), and direction of arrival of the reflected wave signal, and outputs information related to the estimation results (e.g., location information).

[0091] In addition, the target is an object that is detected by the radar device 10, such as vehicles (including four-wheeled and two-wheeled vehicles), people, boulders or curbs, etc.

[0092] [Structure of Radar Transmitter 100]

[0093] The radar transmitter 100 includes a radar signal generator 101, a code generator 104, a phase rotation unit 105, and a transmitting antenna 106.

[0094] 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. The components of the radar transmission signal generation unit 101 will be described below.

[0095] The modulation signal generation unit 102 generates a sawtooth-shaped modulation signal (e.g., a modulation signal for VCO control) according to the radar transmission period Tr.

[0096] VCO103 is based on the modulation signal output from the modulation signal generation unit 102, for example, such as Figure 6 As shown in (a), a frequency modulation signal (hereinafter, for example, referred to as a frequency chirp signal or chirp signal) is generated and output to the phase rotation unit 105 and the radar receiver unit 200 (the mixer unit 204 described later).

[0097] The code generation unit 104 generates a different code for each transmit antenna 106 that performs code multiplexing. The code generation unit 104 outputs the phase rotation amount corresponding to the generated code to the phase rotation unit 105. In addition, the code generation unit 104 outputs information related to the generated code to the radar receiver 200 (output switching unit 209 described later).

[0098] The phase rotation unit 105 applies a 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 may include a phase converter and a phase modulator (not shown). The output signal of the phase rotation unit 105 is amplified to a predetermined transmission power and radiated into space from each transmitting antenna 106. For example, a radar transmission signal is given a phase rotation amount corresponding to a code, and is transmitted via code multiplexing from multiple transmitting antennas 106.

[0099] Next, an example of a code (e.g., an orthogonal code) set in the radar device 10 will be described.

[0100] The code generation unit 104 generates different codes for each transmitting antenna 106 that performs code multiplexing.

[0101] For example, in the following text, let the number of transmit antennas 106 for code multiplexing transmission be “Nt”, and the number of code multiplexing be “N”. CM ".exist Figure 5 N CM =Nt.

[0102] The code generation unit 104 generates N from the code sequence (e.g., orthogonal code sequence that is orthogonal to each other (or simply called a code or orthogonal code)) with a code length (e.g., number of code elements) Loc. allcode (hereinafter, sometimes referred to as N) allcode (Loc) of the orthogonal codes, N CM An orthogonal code is set as the code used for code multiplexing transmission.

[0103] For example, let N be the code multiplexing number. CM N is the orthogonal code number allcode The following, i.e., N CM ≦N allcode For example, N of the code length Loc CM An orthogonal code is represented as Code. ncm ={OC ncm (1), OC ncm (2), ..., OC ncm (Loc)}. Here, "OC" ncm "(noc)" represents the nth orthogonal key Code. ncm The noc-th code element in the code. Additionally, "ncm" represents the index of the orthogonal code used for code multiplexing, ncm = 1, ..., N. CM In addition, "noc" is the index of the code element, noc = 1, ..., Loc.

[0104] As described above, the N generated in the code generation unit 104 CMAn orthogonal code is, for example, a code that is orthogonal to each other (e.g., a code that is uncorrelated with each other). Walsh-Hadamard codes can be used as a sequence of orthogonal codes, for example.

[0105] The following is an example of setting the code number N in a manner that satisfies the following formula (1). CM The code length Loc of an orthogonal code sequence.

[0106]

[0107] Here, ceil[x] is the operator (float function) that outputs the smallest integer greater than or equal to the real number x. The code generation section 104, for example, uses N contained in the Walsh-Hadamard code with a code length of loc. allcode N in (Loc) codes CM An orthogonal code.

[0108] Furthermore, the elements constituting the orthogonal code sequence are not limited to real numbers, but may also include complex values.

[0109] Furthermore, the code can also be other orthogonal codes different from Walsh-Hadamard codes. For example, the code can also be an orthogonal M-sequence code or a pseudo-orthogonal code.

[0110] The above explains the multiplexing number N for each code. CM An example of an orthogonal code.

[0111] Next, an example based on the phase rotation amount of the code generated in the code generation unit 104 for code multiplexing transmission will be described.

[0112] For example, the radar device 10 performs code multiplexing transmission using different orthogonal codes on each of the transmitting antennas Tx#1 to Tx#Nt that are performing code multiplexing transmission. Here, the code generation unit 104, for example, sets the orthogonal code Code assigned to the ncm-th transmitting antenna Tx#ncm in the m-th transmission period Tr. ncm Phase rotation ψ ncm (m), and output to the phase rotation unit 105. Here, ncm = 1, ..., N CM .

[0113] For example, as shown in equation (2) below, for each period of a transmission cycle of code length Loc, the phase rotation amount ψ is... ncm (m), cyclically assigned to the orthogonal code Code ncm The Loc elements of each OC ncm (1), ..., OC ncm (Loc) represents the phase quantity respectively.

[0114] ψ ncm (m)=angle[OCncm (OC_INDEX)] (2)

[0115] Here, `angle(x)` is the operator that outputs the radian phase of the real number `x`, where `angle(1) = 0`, `angle(-1) = π`, `angle(j) = π / 2`, and `angle(-j) = -π / 2`. `j` is the imaginary unit. Additionally, `OC_INDEX` indicates the orthogonal code sequence `Code`. ncm The orthogonal code element index of the element changes cyclically from 1 to Loc according to the transmission period (Tr), as shown in equation (3) below.

[0116] OC_INDEX = mod(m-1, Loc) + 1 (3)

[0117] Here, mod(x, y) is the modulo operator, a function that outputs the remainder after dividing x by y. Furthermore, m = 1, ..., Nc. Nc is the predetermined number of transmission cycles (hereinafter referred to as "radar signal transmission count") used by the radar device 10 for radar positioning. Additionally, the radar device 10 transmits radar signals for a number of times Nc is an integer multiple of Loc (e.g., Ncode times). For example, Nc = Loc × Ncode.

[0118] In addition, the code generation unit 104 outputs the orthogonal code element index OC_INDEX to the output switching unit 209 of the radar receiver unit 200 according to the transmission period (Tr).

[0119] The phase rotation unit 105, for example, has N tx Each of the transmitting antennas 106 has its own corresponding phaser or phase modulator. The phase rotation unit 105, for example, assigns a phase rotation amount ψ, input from the code generation unit 104, to the chirp signal input from the radar transmitting signal generation unit 101 according to the transmission period Tr. ncm (m).

[0120] The phase rotation unit 105, for example, according to the transmission period Tr, assigns a chirp signal input from the radar transmission signal generation unit 101 with a code based on orthogonal code Code assigned to the nth transmission antenna Tx#ncm. ncm Phase rotation ψ ncm (m). Here, ncm = 1, ..., N CM And, m = 1, ..., Nc.

[0121] The self-phase rotation unit 105 is aimed at N tx The output of each transmitting antenna 106, after being amplified to a specified transmitting power, is from N tx One transmitting antenna 106 (e.g., a transmitting array antenna) radiates into space.

[0122] For example, the phase rotation ψ is calculated in each m-th transmission cycle Tr. ncm (m) is output from the code generation unit 104 to the phase rotation unit 105.

[0123] For example, the first (ncm=1) phase rotation unit 105 (e.g., the phaser corresponding to the first transmitting antenna 106 (e.g., Tx#1)) performs phase rotation according to the transmission period Tr for the chirp signal generated in the radar transmitting signal generation unit 101 according to the transmission period Tr, as shown in equation (4) below. The output of the first phase rotation unit 105 is transmitted from the transmitting antenna Tx#1. Here, cp(t) represents the chirp signal of the m-th transmission period Tr.

[0124] exp[jψ1(1)]cp(t),exp[jψ1(2)]cp(t),exp[jψ1(3)]cp(t),...,exp[jψ1(Nc)]cp(t)(4)

[0125] The above describes a structural example of the radar transmitter 100.

[0126] [Structure of Radar Receiver 200]

[0127] exist Figure 5 In this configuration, the radar receiver 200 comprises Na receiving antennas 202 (e.g., also referred to as Rx#1 to Rx#Na) forming an array antenna. Additionally, the radar receiver 200 includes Na antenna system processing units 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a code multiplexing demultiplexing unit 212, and a direction estimation unit 213.

[0128] Each receiving antenna 202 receives the radar transmitted signal reflected by the target, i.e., the reflected wave signal, and outputs the received reflected wave signal as the received signal to the corresponding antenna system processing unit 201.

[0129] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206.

[0130] The receiving radio unit 203 includes a mixer unit 204 and an LPF (low-pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with a chirp signal input from the radar transmit signal generation unit 101, which serves as the transmit signal. The LPF 205, for example, applies LPF processing to the output signal of the mixer unit 204, thereby outputting a beat signal whose frequency corresponds to the time delay of the reflected wave signal. For example, such as... Figure 6As shown in (b), the difference frequency between the frequency of the transmitted chirped signal (transmitted frequency modulated wave) and the frequency of the received chirped signal (received frequency modulated wave) is obtained as the beat frequency.

[0131] The signal processing unit 206 in each antenna system processing unit 201-z (where z = 1 to Na) includes an AD conversion unit 207, a beat frequency analysis unit 208, an output switching unit 209, and a Doppler analysis unit 210.

[0132] The signal output from LPF205 (e.g., beat signal) is converted into discrete sample data by AD conversion unit 207 in signal processing unit 206.

[0133] The beat frequency analysis unit 208 analyzes the N values ​​obtained within a specified time range (distance gate) according to the transmission period Tr. data The discrete sample data is processed using FFT. As a result, the signal processing unit 206 outputs the spectrum showing a peak at the beat frequency corresponding to the time delay of the reflected wave signal (radar reflected wave). Furthermore, as part of the FFT processing, the beat frequency analysis unit 208 can multiply by window function coefficients such as a Hanning window or a Hamming window. Additionally, by using window function coefficients, the radar device 10 can suppress side lobes generated around the beat frequency peak. Furthermore, in N... data When the number of discrete sample data is not a power of 2, the beat frequency analysis unit 208 can, for example, perform FFT processing with an FFT size that is a power of 2 by including zero-padded data.

[0134] Here, the beat frequency response obtained by transmitting the m-th chirped pulse and output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 is determined by RFT. z (f b , m) represents. Here, f b This represents the beat frequency index, which corresponds to the index (window (bin) number) of the FFT. For example, f b =0,...,(N) data / 2)-1, z=1, ..., Na, m=1, ..., N C Beat frequency index f b The smaller the value, the smaller the time delay of the reflected wave signal (e.g., the closer the distance to the target).

[0135] Additionally, the beat frequency index f b It can be converted into distance information R(f) using the following formula (5). b Therefore, the beat frequency index f will be used below. b Also known as "distance index f" b".

[0136]

[0137] Here, B w C0 represents the frequency modulation bandwidth within the distance gate of the chirped signal, and C0 represents the speed of light.

[0138] The output switching unit 209 selectively switches to the OC_INDEX-th Doppler analysis unit 210 among the Loc Doppler analysis units 210 based on the orthogonal code element index OC_INDEX output from the code generation unit 104, and outputs the output of the beat frequency analysis unit 208 for each transmission period. For example, in the m-th transmission period Tr, the output switching unit 209 selects the OC_INDEX-th Doppler analysis unit 210.

[0139] The signal processing unit 206 has Loc Doppler analysis units 210-1 to 210-Loc. For example, through the operation of the output switching unit 209, the noc-th Doppler analysis unit 210 is input with data once in every Loc transmission cycle (Loc×Tr). Therefore, the noc-th Doppler analysis unit 210 uses the data from the Ncode transmission cycles in the Nc transmission cycles (e.g., the beat frequency response RFT output from the beat frequency analysis unit 208). z (f b ,m)), according to each distance index f b Perform Doppler analysis. Here, noc is the index of the code element, noc = 1, ..., Loc.

[0140] For example, when Ncode is a power of 2, FFT processing can be applied in Doppler analysis. In this case, the FFT size is Ncode, and the maximum Doppler frequency without aliasing, derived from the sampling theorem, is ±1 / (2Loc×Tr). Additionally, the Doppler frequency index f... s The Doppler frequency interval is 1 / (Ncode×Loc×Tr), and the Doppler frequency index is f. s The range is f s =-Ncode / 2,...,0,...,Ncode / 2-1.

[0141] 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 represented by the following equation (6). In addition, j is the imaginary unit, z = 1, ..., Na.

[0142]

[0143] Additionally, if the Ncode is not a power of 2, for example, FFT processing can be performed with a data size (FFT size) that is a power of 2 by including zero-padding data.

[0144] The following example illustrates the case where Ncode is a power of 2.

[0145] Furthermore, when performing FFT processing, the Doppler analysis unit 210 can multiply by window function coefficients, such as Hanning or Hamming windows. By applying window functions, the radar device 10 can suppress sidelobes generated around the beat frequency peak.

[0146] The above describes the processing in each component of the signal processing unit 206.

[0147] exist Figure 5 In this process, the CFAR unit 211 uses the outputs of the Loc Doppler analysis units 210 of each of the 1st to Nath signal processing units 206 to perform CFAR processing (e.g., adaptive threshold determination) and extracts the distance index f of the given peak signal. b_cfar and Doppler frequency index f s_cfar .

[0148] For example, the CFAR unit 211 performs the following formula (7) on the output VFT of the Doppler analysis unit 210 of the first to Nath signal processing units 206. z noc (f b f s The power is added, and a two-dimensional CFAR process consisting of a distance axis and a Doppler frequency axis (equivalent to relative velocity) or a combination of one-dimensional CFAR processes is performed. For example, the process disclosed in Non-Patent Document 3 can be applied to the two-dimensional CFAR process or the CFAR process combining one-dimensional CFAR processes.

[0149]

[0150] CFAR unit 211 adaptively sets a threshold and indexes the distance f where the received power is greater than the threshold. b_cfar Doppler frequency index f s_cfar and received power information PowerFT(f b_cfar f s_cfar Output to the demultiplexing unit 212 of the code multiplexing.

[0151] Next, an example of the operation of the demultiplexing unit 212 of code multiplexing will be explained.

[0152] The demultiplexing unit 212 of code multiplexing is, for example, based on the distance index f extracted in the CFAR unit 211.b_cfar and Doppler frequency index f s_cfar The code multiplexing signal is demultiplexed.

[0153] For example, the demultiplexing unit 212 of code multiplexing is as shown in equation (8), for the distance index f extracted in the CFAR unit 211. b_cfar and Doppler frequency index f s_cfar The corresponding Doppler component VFTALL output from the Doppler analysis unit 210 z (f b_cfar f s_cfar ), and perform demultiplexing processing for code multiplexing.

[0154]

[0155] 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 Doppler frequency index f s_cfar The output uses orthogonal codes. ncm The output obtained by demultiplexing a code-multiplexed signal (e.g., the demultiplexing result of code multiplexing). Where z = 1, ..., Na, and ncm = 1, ..., N CM Furthermore, in equation (8), the following operator represents the product obtained by multiplying the elements of two vectors with equal number of elements:

[0156] Operators

[0157] For example, an nth-order vector A = [a1, ..., a2] n ] and B = [b1, ..., b n The product of the elements of ] is represented by the following formula (9).

[0158]

[0159] Additionally, in equation (8), the following operator represents the vector dot product operator:

[0160] The operator "·".

[0161] In addition, in equation (8), the superscript T represents vector transpose, and the superscript * (asterisk) represents the complex conjugate operator.

[0162] In equation (8), α(f s_cfar ) represents the "Doppler phase correction vector". For example, the Doppler frequency index f extracted from CFAR section 211 is used to represent this vector.s_cfar When the output range of the Doppler analysis unit 210, which does not contain Doppler aliasing, is set to (e.g., the Doppler range), the Doppler phase correction vector α(f) is... s_cfar Correction is made for the Doppler phase rotation caused by the time difference of Doppler analysis between Loc Doppler analysis units 210.

[0163] Doppler phase correction vector α(f) s_cfar For example, it can be represented by the following equation (10). The Doppler phase correction vector α(f) shown in equation (10) s_cfar ) is a vector whose elements are Doppler phase correction coefficients, such as the output VFT of the first Doppler analysis unit 210. z 1 (f b_cfar f s_cfar Based on the Doppler analysis time, the output VFT of the second Doppler analysis unit 210 is analyzed. z 2 (f b_cfar f s_cfar The output VFT of the Loc Doppler analysis unit 210 z Loc (f b_cfar f s_cfar The Doppler frequency index f caused by the time delays of their respective Tr, 2Tr, ..., (Loc-1)Tr s_cfar The phase rotation in the Doppler component is corrected.

[0164]

[0165] Furthermore, in equation (8), for example, as shown in equation (11) below, VFTALL z (f b_cfar f s_cfar The output VFT of Loc Doppler analysis units 210 in the z-th antenna system processing unit 201 is represented in vector form. z noc (f b f s The distance index f extracted in CFAR section 211 is compared with the distance index f in CFAR section 211. b_cfar and Doppler frequency index f s_cfar Corresponding component VFT z noc (f b_cfar f s_cfar (where noc = 1, ..., Loc).

[0166] VFTALL z (f b_cfar ,fs_cfar ) = [VFT z 1 (f b_cfar ,f s_cfar VFT z 2 (f b_cfar ,f s_cfar ...,VFT z Loc (f b_cfar ,f s_cfar (11)

[0167] The above describes an example of the operation of the demultiplexing unit 212 for code multiplexing. Figure 5 In the structure shown, the maximum Doppler frequency that does not produce aliasing, derived from the sampling theorem, is ±1 / (2Loc×Tr). The operation of the demultiplexing unit 212 for code multiplexing is explained above, assuming that the object detected by the radar device 10 is within this range.

[0168] In the radar device 10, for example, a configuration of transmitting antenna 106 and receiving antenna 202 can be adopted, which suppresses grating lobes or sidelobes and improves angular resolution by increasing array gain and increasing the aperture length based on the virtual receiving antenna.

[0169] Hereinafter, an example of the antenna configuration of the transmitting antenna 106 and the receiving antenna 202, and an example of the direction estimation processing in the direction estimation unit 213 when each configuration example is applied will be described.

[0170] Furthermore, in the following configuration examples and variations, the configuration of the transmitting antenna 106 can be replaced with the configuration of the receiving antenna 202, and vice versa. In the radar device 10, even if the antenna configurations of the transmitting antenna 106 and the receiving antenna 202 are interchanged, the same virtual receiving antenna configuration can be obtained (the numbering of the virtual receiving antenna will change), and the same effect as the following configuration examples (e.g., the same angle measurement performance) can be achieved.

[0171] Alternatively, the horizontal and vertical directions can be interchanged in the following configuration examples and variations. In the radar device 10, when the horizontal and vertical directions are interchanged in the antenna configuration, the configuration as a virtual receiving antenna results in a configuration where the horizontal and vertical directions are interchanged, achieving the effect of interchanged horizontal and vertical directions in the following configuration examples (e.g., improved angle resolution).

[0172] Alternatively, the horizontal and vertical directions in the configuration example may not strictly correspond to the horizontal and vertical directions. Instead, the configuration example can be tilted at a predetermined angle while maintaining the relative positional relationship between the transmitting and receiving antennas. In this case, the same effect can be achieved because the relative positional relationship between the transmitting and receiving antennas in the configuration example is maintained.

[0173] The antenna configuration of radar device 10 (e.g., MIMO antenna configuration) may be a configuration that satisfies the following configuration conditions.

[0174] [Configuration Condition A]

[0175] The virtual receiving antenna is configured in an oblique direction ψ. Here, "configured in an oblique direction ψ" means configured in a direction with an angle ψ to the horizontal. For example, the angle ψ to the horizontal can be set within the range of 30° ≤ ψ ≤ 60°. Furthermore, the spacing of the virtual receiving antennas configured in an oblique direction ψ includes a spacing D. d The interval D d It is 0.5λ.

[0176] For example, the virtual receiving antennas formed by the transceiver antennas of the radar device 10 may include a plurality of virtual receiving antennas (e.g., corresponding to a first virtual receiving antenna group) that satisfy configuration condition A. Configuration condition A is that the virtual receiving antennas are arranged in an oblique direction (e.g., a third direction), which is different from both a horizontal direction (e.g., corresponding to a first direction) and a vertical direction (e.g., corresponding to a second direction orthogonal to the first direction), and at least one of the intervals between adjacent virtual receiving antennas is 0.5λ (e.g., a predetermined value based on the wavelength of the radar transmitted signal). For example, in the transmitting antenna interval D... t and receiving antenna spacing D r Satisfy D t With D r The absolute value of the difference D d (=|D t -D r |) is an interval of approximately 0.5λ (1 times the specified value), or satisfies D t With D r The absolute value of the difference D d (=|D t -D r |) is an integer multiple of 2 or more (an integer multiple of 2 or more of the specified value) of the interval approximately 0.5λ and D t and D rWhen one of the intervals is approximately 0.5λ (1 times the specified value), at least one of the intervals between two adjacent virtual receiving antennas becomes 0.5λ (e.g., a specified value based on the wavelength of the radar transmitted signal).

[0177] Additionally, although the interval is set to D here... d =0.5λ, but it can also be an interval of about 0.5λ to 0.8λ. For example, the interval D can be set according to the field of view angle in the horizontal or vertical direction of the radar device 10. d For example, in the case of a wide field of view with a horizontal or vertical field of view ranging from ±70 degrees to 90 degrees, the interval D d It can be set to around 0.5λ. Alternatively, in the case of a narrow field of view with a horizontal or vertical field of view ranging from ±20 degrees to 40 degrees, the interval D... d The interval can be set to be larger than 0.5λ (e.g., around 0.7λ). Regarding the interval D... d The same setting applies to the configuration examples (or variations) that follow.

[0178] Additionally, λ represents the wavelength of the carrier frequency of the radar signal. For example, when using a chirped signal as the radar signal, λ is the wavelength of the center frequency of the frequency scan band of the chirped signal.

[0179] By configuring a virtual receiving antenna along the oblique ψ according to configuration condition A, the aperture in both the horizontal and vertical directions can be enlarged. Furthermore, in configuration condition A, to prevent uncertainty when performing phase change detection based on the virtual receiving antenna configured along the oblique ψ, an interval D of approximately 0.5λ is included. d .

[0180] Furthermore, the virtual receiving antenna configured along the oblique ψ direction detects phase information that depends on both the horizontal and vertical angles of arrival of the target. Therefore, when the radar device 10 acquires two-dimensional angle measurement information, it uses the phase information derived from the horizontal and vertical angles of arrival of the target. Thus, in addition to configuration condition A, at least one of configuration conditions B and C, described later, is also used.

[0181] [Configuration Condition B]

[0182] At least two of the virtual receiving antennas are configured to be arranged in a horizontal row, with an interval of D. H (Hereinafter also referred to as "horizontal interval"). Horizontal interval D H For example, it is set at λ / (2sinψ)≧D H Within the range of >λ / 2.

[0183] For example, the virtual receiving antenna formed by the transceiver antenna of the radar device 10 may include a virtual receiving antenna that satisfies configuration condition B, wherein the virtual receiving antenna is configured in the horizontal direction, and at least one of the intervals between two adjacent virtual receiving antennas in the horizontal direction is greater than 0.5λ.

[0184] Additionally, if set to D H If the value is greater than λ / (2sinψ), then grating lobes may be generated within a specific azimuth or elevation angle (azimuth / elevation) range. When the radar detection area is wide-angle, false detections due to grating lobes may occur, affecting performance. However, when the radar detection area is a relatively narrow region near the front, the radar detection performance is unaffected by grating lobes, so it can also be set to D. H >λ / (2sinψ).

[0185] [Configuration Condition C]

[0186] At least two of the virtual receiving antennas are configured to be arranged in a vertical row, with an interval of D. V (Hereinafter also referred to as "vertical spacing"). Vertical spacing D V For example, it is set at λ / (2cosψ)≧D V Within the range of >λ / 2.

[0187] For example, the virtual receiving antenna formed by the transceiver antenna of the radar device 10 may include a virtual receiving antenna that satisfies configuration condition C, wherein the virtual receiving antenna is configured in the vertical direction, and at least one of the intervals between two adjacent virtual receiving antennas in the vertical direction is greater than 0.5λ.

[0188] Additionally, if set to D V If the value is greater than λ / (2cosψ), then grating lobes may be generated within a specific azimuth / elevation range. When the radar detection area is wide-angle, false detections may occur due to grating lobes. However, when the radar detection area is a relatively narrow region near the front, it is not affected by grating lobes and has no negative impact on radar detection performance. Therefore, it can also be set to D. V >λ / (2cosψ).

[0189] By satisfying configuration condition B, radar device 10 can detect the horizontal angle of arrival information of the target. Furthermore, by satisfying configuration condition C, radar device 10 can detect the vertical angle of arrival information of the target. Additionally, in configuration conditions B and C, since the horizontal interval D is set... H >λ / 2, Vertical Spacing D VThe aperture length is greater than λ / 2, thus enabling the expansion of the aperture length in both the horizontal and vertical directions. Furthermore, although grating lobes may be present in the horizontal and vertical directions due to configuration conditions B and C, these lobes can be removed from the radar device 10 by satisfying configuration condition A and either configuration condition B or configuration condition C.

[0190] The following describes examples of the configuration conditions described above. An example of a MIMO antenna configuration that meets the above conditions, and an example of the direction estimation results based on computer simulation for that configuration, will be described below.

[0191] <Configuration Example 1>

[0192] Figure 7 Figure (a) is a diagram illustrating a configuration example (e.g., a MIMO antenna configuration example) of the transmitting antenna 106 (e.g., denoted as Tx) and the receiving antenna 202 (e.g., denoted as Rx) under the above configuration conditions. Figure 7 In the example shown in (a), the number of transmitting antennas N Tx There are 2 antennas (e.g., Tx#1 and Tx#2), and the number of receiving antennas Na is 3 (e.g., Rx#1, Rx#2 and Rx#3).

[0193] exist Figure 7 In (a), N Tx =The angle ψ between the two transmitting antennas Tx#1 and #2 and the horizontal direction is (in Figure 7 In (a), ψ = 45°, the angle is upward at interval D. t Configuration.

[0194] In addition, Figure 7 In (a), Na = at least two of the three receiving antennas Rx#1 to #2 are positioned in the same direction as the oblique ψ along which the transmitting antennas Tx#1 to #2 are arranged, with a spacing of D. r Configuration.

[0195] Here, it could be such that D t and D r The absolute value of the difference D d (=|D t -D r |) becomes an interval of approximately 0.5λ (D) d The transmitting antenna spacing D is set in the manner of ≒0.5λ). t and receiving antenna spacing D r .exist Figure 7 In (a), for example, by setting the interval D t =1.5λ, Interval D r =λ, thus in the virtual receiving antenna configuration, there is an interval D of approximately 0.5λ (1 times the specified value). dConfiguration condition A is met.

[0196] In addition, Figure 7 In (a), relative to the receiving antennas Rx#1 to Rx#2 arranged in the same direction as the oblique ψ on which the transmitting antennas Tx#1 to #2 are arranged, at least one of the other receiving antennas (in Figure 7 In (a), Rx#3) is the receiving antenna positioned relative to the oblique ψ, with a horizontal spacing of D. H Configuration, or in the vertical direction at intervals D V Configuration.

[0197] For example, in Figure 7 In (a), the receiving antenna Rx#3 is positioned horizontally at a distance D from the receiving antenna Rx#2. H And in the vertical direction, it is separated from the receiving antenna Rx#1 by a distance D. V The position. Here, by using the horizontal interval D H Set as λ / (2sinψ)≧D H >λ / 2, thus satisfying configuration condition B. Additionally, by adjusting the vertical spacing D... V Set as λ / (2cosψ)≧D V >λ / 2, thus satisfying configuration condition C. In Figure 7 In (a), for example, when set to horizontal interval D H =λ×cosψ(≒0.7λ), vertical interval D V When =λ×sinψ(≒0.7λ), both configuration conditions B and configuration condition C are satisfied.

[0198] Thus, in Figure 7 In (a), the transmitting antennas Tx#1 (e.g., corresponding to the t1-th antenna) and Tx#2 (e.g., corresponding to the t2-th antenna) are configured in the oblique direction ψ (e.g., corresponding to the third direction). Additionally, in Figure 7 In (a), two receiving antennas Rx#1 (e.g., corresponding to the r1-th antenna) and Rx#2 (e.g., corresponding to the r2-th antenna) are configured obliquely in the direction ψ, and the spacing D between the receiving antennas Rx#1 and Rx#2 is D. r (For example, also represented as spacing dr) and the spacing D between transmitting antennas Tx#1 and Tx#2. t (For example, also denoted as interval dt) The absolute value D of the difference between these two intervals. d It is set to 0.5λ. Additionally, in Figure 7 In (a), Rx#3 (e.g., corresponding to the r3rd antenna) and Rx#2 are spaced D apart in the horizontal direction (e.g., corresponding to the second direction). H (by D) d=0.5λ large interval (e.g., also denoted as interval dh) configuration, Rx#3 and Rx#1 are spaced at interval D in the vertical direction (e.g., corresponding to the first direction). V (by D) d =0.5λ large interval (e.g., also represented as interval dv) configuration.

[0199] Additionally, in the number of transmitting antennas N Tx If there are three or more antennas, at least two (e.g., Tx#1 and Tx#2) need to meet the above configuration conditions. Additionally, if there are three or more receiving antennas Na, at least three (e.g., Rx#1, Rx#2, and Rx#3) need to meet the above configuration conditions.

[0200] Figure 7 (b) indicates through Figure 7 The diagram shows an example of the configuration of the virtual receiving antenna obtained by the antenna configuration shown in (a).

[0201] Here, for example, the configuration of the virtual receiving antenna can be based on the location of the transmitting antenna 106 (e.g., the location of the feed point or the phase center of each antenna) and the location of the receiving antenna 202 (e.g., the location of the feed point or the phase center of each antenna), and is represented by the following equation (12).

[0202] (12)

[0203] Here, the horizontal and vertical position coordinates of the transmitting antenna 106 (e.g., Tx#n) are represented as (X T_#n Y T_#n (For example, n = 1, ..., N) Tx The position coordinates of the receiving antenna 202 (e.g., Rx#m) are represented as (X R_#m Y R_#m (For example, m = 1, ..., Na), the position coordinates of the virtual receiving antenna VA#k are represented as (X V_#k Y V_#k (For example, k = 1, ..., N) Tx ×Na).

[0204] In addition, in equation (12), VA#1 is represented, for example, as the location reference (0, 0) of the virtual receiving array.

[0205] exist Figure 7 In (a), in the configuration of transmitting antennas Tx#1 to Tx#2, the position coordinates (X) of transmitting antenna Tx#1 are... T_#1 Y T_#1 With ) set as the reference, the position coordinates (X) of Tx#2 T_#2 Y T_#2)=(X T_#1 +D t ×cosψ,Y T_#1 +D t ×sinψ). Additionally, in Figure 7 In (a), in the configuration of receiving antennas Rx#1 to Rx#3, the position coordinates (X...) of receiving antenna Rx#1 are... R_#1 Y R_#1 When (X) is set as the baseline, R_#2 Y R_#2 )=(X R_#1 +D r ×cosψ,Y R_#1 +D r ×sinψ), and (X R_#3 Y R_#3 )=(X R_#1 +D r ×cosψ-D H Y R_#1 +D V Additionally, for example, in Figure 7 In (a) and (b), when ψ = 45°, the horizontal interval D H =λ×cosψ(≒0.7λ), vertical interval D V =λ×sinψ(≒0.7λ). Therefore, (X R_#3 Y R_#3 )=(X R_#1 Y R_#1 +λ×sinψ). Therefore, the position coordinates of the virtual antennas VA#1 to #6 can be calculated according to equation (12). For example, the position coordinates of the virtual antennas VA#1 to #6 are (X V_#1 Y V_#1 ) = (0, 0), (X V_#2 Y V_#2 )=(D r ×cosψ,D r ×sinψ), (X) V_#3 Y V_#3 )=(0,D V ), (X V_#4 Y V_#4 )=((D r +D d )×cosψ,(D r +D d )×sinψ),(X V_#5 Y V_#5 )=((2D r +D d )×cosψ,(2D r +D d)×sinψ),(X V_#6 Y V_#6 )=((2D r +D d )×cosψ-D H , (2D r +D d )×sinψ).

[0206] like Figure 7 As shown in (b), VA#1, VA#2, VA#4 and VA#5 are arranged diagonally along ψ, with the interval between two adjacent VA#2 and VA#4 being D. d (=0.5λ). Additionally, such as... Figure 7 As shown in (b), VA#5 and VA#6 (or VA#2 and VA#3) are arranged horizontally, and the spacing between VA#5 and VA#6 (or the spacing between VA#2 and VA#3) in the horizontal direction is greater than D. d Big D H Additionally, such as Figure 7 As shown in (b), VA#1 and VA#3 (or VA#4 and VA#6) are arranged in the vertical direction, and the spacing between VA#1 and VA#3 (or the spacing between VA#4 and VA#6) in the vertical direction is greater than D. d Big D V .

[0207] For example, in Figure 7 In (b), the virtual receiving antennas include VA#3 and VA#6 (e.g., corresponding to the second virtual receiving antenna group), which are different from VA#1, VA#2, VA#4, and VA#5 (e.g., corresponding to the first virtual receiving antenna group) configured in the oblique direction ψ (e.g., corresponding to the fifth direction) and configured in a direction parallel to the oblique direction ψ (e.g., corresponding to the fifth direction). Additionally, in Figure 7 In (b), the vertical spacing D between one virtual antenna (e.g., VA#1 or VA#5) contained in VA#1, VA#2, VA#4 and VA#5 (the first virtual receiving antenna group) and one virtual receiving antenna contained in VA#3 and VA#6 (e.g., the second virtual receiving antenna group) is... V Larger than the specified value (e.g., 0.5λ). Additionally, for example, in... Figure 7 In (b), the horizontal spacing D between one virtual antenna (e.g., VA#2 or VA#5) contained in VA#1, VA#2, VA#4 and VA#5 (the first virtual receiving antenna group) and one virtual receiving antenna contained in VA#3 and VA#6 (e.g., the second virtual receiving antenna group) is... H It is larger than the specified value (e.g., 0.5λ).

[0208] As mentioned above, Figure 7The virtual receiving antenna shown in (b) satisfies configuration conditions A, B and C.

[0209] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described configuration example 1 is applied will be described.

[0210] For example, the direction estimation unit 213 uses the received signal DeMul, which has undergone code multiplexing and demultiplexing processing on the code multiplexed signal transmitted from the transmitting antenna 106. z ncm (f b_cfar f s_cfar ), to generate the virtual receiver array correlation vector h(f) of the transmitting antenna 106 shown in equation (13). b_cfar f s_cfar ), and perform direction estimation processing.

[0211] Virtual receiver array correlation vector h(f) b_cfar f s_cfar (Includes the number of transmitting antennas N) Tx The product of this and the number of receiving antennas Na is N. Tx ×Na elements. Virtual receiver array correlation vector h(f) b_cfar f s_cfar This is used for processing the reflected wave signal from the target to estimate the direction based on the phase difference between each receiving antenna 202. Here, z = 1, ..., Na.

[0212] In the MIMO antenna configuration of Configuration Example 1, N Tx =2, Na=3, so the virtual receiver array correlation vector h(f) b_cfar f s_cfar It contains 6 elements, each element corresponding to Figure 7 The received signals in VA#1 to VA#6 of the virtual receiving antenna configuration shown in (b). For example, VA#1 corresponds to 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 2nd to 6th elements correspond to the received signals VA#2 to VA#6, respectively.

[0213]

[0214] Next, the direction estimation unit 213 uses the received signal of the virtual receiving array configured by the above-described transceiver antennas, i.e., the virtual receiving array correlation vector h(f) b_cfar f s_cfar The horizontal and vertical directions are estimated in the following manner.

[0215] As shown in equations (14) and (15) below, the direction estimation unit 213 estimates the virtual array correlation vector h(f) b_cfar f s_cfar The array correction value h_cal is multiplied by the array correction value h_cal used to correct the phase and amplitude deviations between the transmitting and receiving array antennas. [y] Output the virtual receiver array correlation vector h after correcting for inter-antenna misalignment. after_cal (f b_cfar f s_cfar The direction estimation process in the horizontal and vertical directions is performed based on the phase difference between the receiving antennas receiving the reflected wave. Here, y = 1, ..., (N) Tx ×Na).

[0216] Furthermore, the CA shown in equation (15) is an array correction coefficient that includes the phase and amplitude deviations between transmitting and receiving antennas, as well as a coefficient that reduces the influence of inter-element coupling between antennas (N). Tx A square matrix of dimensions (×Na). If the coupling between the antennas of the virtual receiver array is negligible, then CA is a diagonal matrix, and its diagonal elements contain array correction values ​​h_cal to correct for phase and amplitude deviations between the transmitting and receiving antennas. [y] .

[0217] The virtual receiver array correlation vector h after correcting for inter-antenna misalignment _after_cal (f b_cfar f s_cfar ) becomes N Tx A column vector consisting of ×Na elements. Hereinafter, each element is represented as h1(f b_cfar f s_cfar ), ..., h NTx×Na (f b_cfar f s_cfar This section explains the direction estimation process.

[0218]

[0219] Direction estimation unit 213 uses the virtual receiver array correlation vector h after correcting for inter-antenna misalignment. after_cal (f b_cfar f s_cfar The direction estimation unit 213 performs direction estimation in both the horizontal and vertical directions. In the horizontal and vertical direction estimation, the direction estimation unit 213 changes the arrival direction estimation evaluation function value within a specified angle range. The azimuth direction θ and elevation direction in the middle To calculate the spatial distribution, a specified number of maximum peak directions are extracted from them in descending order. The azimuth and elevation directions of each maximum peak are then output as estimated directions of arrival. Here, θ, This represents the azimuth and elevation angles relative to the target. For example, when an antenna is configured in the XZ plane (e.g., let the X-axis be horizontal and the Z-axis be vertical), the radar axis in the direction of the radar's front (vertical relative to the XZ plane) is the Y-axis, and the direction cosines of the X, Y, and Z axes relative to the target are respectively... express.

[0220] Additionally, regarding the evaluation function value for the arrival direction estimation Various methods exist based on direction-of-arrival estimation algorithms. For example, the estimation method using an array antenna disclosed in Non-Patent Document 4 can be used. For example, the beamforming method can be represented by the following equation (16). Here, the superscript H is the Hermitian transpose operator. In addition, methods such as Capon and MUSIC are also applicable. P(θ u ,φ v ,f b_cfar ,f s_cfar )=|a H (θ u ,φ v )h _after_cal (f b_cfar ,f s_cfar )| 2 (16)

[0221] Here, θ u This is a value that varies within the azimuth range used for arrival direction estimation, based on a specified azimuth interval β1. For example, θ is set as follows: u θ u =θmin + uβ1. u = 0, ..., NU. NU = floor[(θmax - θmin) / β1]. Here, floor(x) is a function that returns the largest integer value not exceeding the real number x.

[0222] in addition, This is a value that varies within the specified elevation angle interval β2, within the elevation angle range used for direction of arrival estimation. For example, it can be set as follows: v = 0, ..., NV.

[0223] Here, direction vector Therefore, the radar reflected wave travels from the azimuth direction θ and the elevation direction. The complex response of the virtual receiving antenna upon arrival is the element (N) Tx A column vector of (×Na) dimensions. The complex response of the virtual receiving antenna. This represents the phase difference calculated geometrically and optically based on the element spacing between antennas. Furthermore, relative to the antenna surface shown in Configuration Example 1, the vertical direction of the front is set as the reference (azimuth θ = 0°, elevation angle...). ).

[0224] <Example of orientation estimation results in Configuration Example 1>

[0225] Next, an example of the directional estimation result (computer simulation result) when the antenna configuration of the above configuration example 1 is applied will be explained.

[0226] Figure 8 (a) and (b) indicate that in Figure 7 The example shown in (a) illustrates an antenna configuration for a MIMO radar receiving angle measurements based on beamforming when a reflected wave from a target at 0° horizontally and 40° vertically is received. Figure 8 The direction estimation results shown in (a) and (b) plot the output of the arrival direction estimation evaluation function values ​​for the horizontal ±90 degree range and the vertical ±90 degree range. Additionally, in Figure 8 In (a), the horizontal axis represents the angles in the horizontal and vertical directions, while the vertical axis represents the normalized power values ​​in the aforementioned two-dimensional directions in three dimensions. Furthermore, Figure 8 (b) is viewed from above. Figure 8 Figure (a) is an example of a heatmap display of normalized power values ​​in two dimensions, with the horizontal axis as the horizontal direction and the vertical axis as the vertical direction, and the power values ​​are displayed in grayscale.

[0227] Depend on Figure 8 As shown in (a) and (b), the main beam is oriented at 0° horizontally and 40° vertically, and no grating lobes are generated. Furthermore, in... Figure 7 In the case of the MIMO radar antenna configuration shown in (a), the horizontal beamwidth is approximately 23° and the vertical beamwidth is approximately 24° (when using a Fourier beam pattern oriented towards 0° horizontally and 0° vertically). Therefore, in Figure 7 In antenna configuration (a), with Figure 1 Compared to the previous antenna configuration, the 3dB beamwidth in the horizontal direction is reduced to 6.2% (=23 / 37), and the 3dB beamwidth in the vertical direction is reduced to 4.1% (=24 / 59). Therefore, it is expected to improve the two-dimensional angle measurement accuracy in both the horizontal and vertical directions (for example, to achieve an accuracy improvement of about 1.6 to 2.5 times).

[0228] The above provides an example of the orientation estimation result (computer simulation result) of Configuration Example 1 and the effect of Configuration Example 1.

[0229] exist Figure 5 In the process, the direction estimation unit 213 outputs, for example, the direction estimation result as the positioning result, and may also output a result based on the distance index f. b_cfar Distance information (e.g., information derived from Equation (5)), target-based Doppler frequency index f b_cfar Doppler velocity information of the target.

[0230] To index the Doppler frequency f s_cfar Converted to relative velocity component v d (f s_cfar Alternatively, the following equation (17) can be used for conversion. Here, λ is the wavelength of the carrier frequency of the RF signal output from the transmitting wireless unit (not shown). Additionally, Δ f This refers to the Doppler frequency interval in the FFT processing of the Doppler analysis unit 210. For example, in this embodiment, Δ f =1 / {Loc×N code ×T r}

[0231]

[0232] The above describes an example of the operation of radar device 10.

[0233] As described above, in Configuration Example 1, in the MIMO antenna configuration, by satisfying both configuration condition A and configuration condition B or configuration condition C, two-dimensional angle-of-arrival information of the target with suppressed (or removed) grating lobes can be obtained. Furthermore, in Configuration Example 1, by configuring the MIMO antenna in a manner that extends the virtual antenna along the oblique ψ direction, the opening surfaces in the vertical and horizontal directions can be expanded, thereby improving the two-dimensional angle measurement accuracy in both the horizontal and vertical directions. Thus, even when the number of antennas is a predetermined number, it is possible to perform an antenna configuration that expands the element spacing in at least one direction in the vertical and horizontal directions and suppresses grating lobes, thereby improving the angle measurement accuracy (or resolution) of the radar device 10 in both the horizontal and vertical directions.

[0234] Additionally, in the MIMO antenna configuration of Configuration Example 1, besides the virtual receiving antennas arranged obliquely in the direction ψ that satisfy configuration condition A (in... Figure 7 In addition to VA#1, #2, #4, and #5 in (b), there are also virtual receiving antennas arranged obliquely in the ψ direction at locations different from the configuration positions of these virtual receiving antennas. Figure 7(in (b) VA#3 and VA#6). Therefore, in the direction estimation unit 213, a simplified two-dimensional angle measurement method (hereinafter referred to as the "simplified two-dimensional angle measurement method") can be applied, which can significantly reduce the amount of two-dimensional angle measurement processing compared with the two-dimensional Fourier beamforming angle measurement method described above. Examples of the simplified two-dimensional angle measurement method will be described later.

[0235] Furthermore, the antenna configuration in Configuration Example 1 is not limited to... Figure 7 The antenna configuration shown in (a) is also possible. For example, in configuration example 1, it is also possible to... Figure 7 In the antenna configuration shown in (a), at least one of the transmitting antenna 106 and the receiving antenna 202 is further additionally antennaed. When the transmitting antenna 106 or the receiving antenna 202 is added, for example, it becomes an additive addition of a virtual receiving antenna based on the position shown in equation (12). For example, it becomes... Figure 7 Based on the virtual receiving antenna configuration shown in (b), further configurations of other virtual receiving antennas are added. When using such an antenna configuration including Configuration Example 1, the effects described in Configuration Example 1 are also maintained, and the same effects as in Configuration Example 1 can be obtained.

[0236] Furthermore, for example, by adding an antenna to the antenna structure of Configuration Example 1, while achieving the same effect as described in Configuration Example 1, it is easy to further reduce the level of the suppressed grating lobe or sidelobe, thereby reducing false detections during angle measurement in the radar device 10 and improving angle measurement performance. Additionally, the same effect can be obtained by adding an antenna to the configuration examples or variations described below.

[0237] The following describes the antenna configuration in Configuration Example 1 (for example, Figure 7 The example described in (a) is an example in which at least one of the transmitting antenna 106 and the receiving antenna 202 is further added. Furthermore, the addition of antennas can also be applied to the configuration examples or variations described below, achieving the same effect.

[0238] Figure 9 (a) is in Figure 7 The antenna configuration shown in (a) is further supplemented with a configuration example of transmitting antenna Tx#3. Figure 9 In (a), relative to Tx#2, along the oblique ψ at intervals D t2 Configure Tx#3. Additionally... Figure 9 (b) is in Figure 7 An example of the configuration of receiving antenna Rx#4 is further added to the antenna configuration shown in (a). Figure 9 In (b), relative to Rx#2, along the oblique ψ at intervals D r2Configure Rx#4.

[0239] By adopting Figure 9 The antenna configurations of (a) and (b) satisfy configuration condition A. The addition of a virtual receiving antenna (not shown) configured in the oblique direction ψ can further expand the aperture in both the horizontal and vertical directions, thus improving the angle measurement performance in both the horizontal and vertical directions.

[0240] In addition, Figure 9 In (a), the interval D between Tx#3 and Tx#2 is shown. t2 The interval D between Tx#1 and Tx#2 t The cases where they are equal, but not limited to this, even if the interval D t2 It is with interval D t Different intervals can achieve the same effect. Similarly, in Figure 9 In (b), the interval D between Rx#4 and Rx#2 is shown. r2 The interval D between Rx#1 and Rx#2 r The cases where they are equal, but not limited to this, even if the interval D r2 It is with interval D r Different intervals can achieve the same effect.

[0241] Figure 9 (c) is in Figure 7 An example of the configuration of receiving antenna Rx#4 is further added to the antenna configuration shown in (a). Figure 9 In (c), relative to Rx#3, arranged in a horizontal column with an interval of D H2 Configure Rx#4. For example, it can be set to interval D. H2 >λ. By adopting Figure 9 The antenna configuration shown in (c) can add a virtual receiving antenna configured in the horizontal direction that satisfies configuration condition B, which can further expand the aperture in the horizontal direction and thus improve the angle measurement performance in the horizontal direction.

[0242] In addition, Figure 9 In (c), the interval D between Rx#4 and Rx#3 is shown. H2 It is the interval D between Rx#2 and Rx#3. H Different intervals, but not limited to these, even if the interval D H2 It is with interval D H The same interval can achieve the same effect. Additionally, for example, by using interval D... H2 and interval D H Setting the interval to coprime allows for different intervals in the grid lobes, which can improve the suppression effect of the grid lobes and is a better configuration.

[0243] in addition, Figure 9 The antenna configuration shown in (c) is Figure 7 The antenna configuration shown in (a) includes an additional receiving antenna 202 (Rx#4), but is not limited to this; for example, a transmitting antenna 106 could also be added. For instance, if the antennas are arranged in a horizontal row relative to transmitting antennas Tx#1 or Tx#2 with a spacing of D... H2 The same effect can be achieved by adding the configuration of the transmitting antenna Tx#3 (not shown).

[0244] Figure 9 (d) is in Figure 7 An example of the configuration of receiving antenna Rx#4 is further added to the antenna configuration shown in (a). Figure 9 In (d), relative to Rx#3, arranged in a vertical column with an interval of D V2 Configure Rx#4. For example, it can be set to interval D. V2 >λ. By adopting Figure 9 The antenna configuration shown in (d) can increase the number of virtual receiving antennas configured in the vertical direction to meet configuration condition C, which can further expand the aperture in the vertical direction and thus improve the angle measurement performance in the vertical direction.

[0245] In addition, Figure 9 In (d), the interval D between Rx#4 and Rx#3 is shown. V2 It is the interval D between Rx#1 and Rx#3. V Different intervals, but not limited to these, even if the interval D V2 It is with interval D V The same interval can achieve the same effect. Additionally, for example, by using interval D... V2 and interval D V Setting the interval to coprime allows for different intervals in the grid lobes, which can improve the suppression effect of the grid lobes and is a better configuration.

[0246] in addition, Figure 9 The antenna configuration shown in (d) is Figure 7 The antenna configuration shown in (a) includes an additional receiving antenna 202 (Rx#4), but is not limited to this; for example, a transmitting antenna 106 could also be added. For instance, if the antennas are arranged in a vertical row relative to transmitting antennas Tx#1 or Tx#2 with a spacing of D... V2 The same effect can be achieved by adding the configuration of the transmitting antenna Tx#3 (not shown).

[0247] Figure 9 (e) is in Figure 7An example of the configuration of receiving antenna Rx#4 is further added to the antenna configuration shown in (a). Figure 9 In (e), other receiving antennas Rx#3, which are different from the virtual receiving antennas Rx#1 and Rx#2 that satisfy configuration condition A, are arranged in a row along the oblique direction ψ at intervals D. s Configure Rx#4. For example, it can be set to interval D. s >λ. By adopting Figure 9 The antenna configuration shown in (e) can add a virtual receiving antenna configured in the oblique direction ψ, which can further expand the aperture in both the horizontal and vertical directions, thus improving the angle measurement performance in both the horizontal and vertical directions.

[0248] In addition, Figure 9 In (e), the interval D between Rx#3 and Rx#4 is shown. s It is the interval D between Tx#1 and Tx#2. t Different intervals, but not limited to these, even if the interval D s It is with interval D t The same interval can achieve the same effect. Additionally, for example, by using interval D... s and interval D t Setting the interval to coprime allows for different intervals in the grid lobes, which can improve the suppression effect of the grid lobes and is a better configuration.

[0249] in addition, Figure 9 The antenna configuration shown in (e) is Figure 7 The antenna configuration shown in (a) includes the addition of a receiving antenna 202 (Rx#4), but is not limited to this. For example, if other transmitting antennas 106, different from the transmitting antennas constituting the virtual receiving antenna that satisfies configuration condition A, are used, arranged in a row along the oblique direction ψ at intervals D... s Configuring the transmitting antenna will also achieve the same effect. Additionally, Figure 9 In the middle, D d It is 1 times the specified value.

[0250] Furthermore, using a high-gain antenna is effective in extending the detection range of the radar device 10. For example, the antenna gain can be increased by narrowing the antenna's directivity (beamwidth). The antenna's directivity narrows, for example, as the antenna's aperture widens. Therefore, the narrower the antenna's directivity, the easier it is to increase the antenna size. For example, in radar devices mounted on vehicles (e.g., also called vehicle-mounted radar), a subarray antenna composed of multiple antenna elements arranged vertically can be used to narrow the vertical directivity. By using a subarray antenna to narrow the vertical directivity, the vertical antenna gain can be increased, reducing reflected waves from unwanted directions such as the road surface. Here, the vertical direction refers to the height direction of the vehicle on which the radar device is mounted (or installed). The horizontal direction refers to the vehicle's forward direction, a direction orthogonal to the vehicle's forward direction, or a direction orthogonal to the vehicle's height direction.

[0251] Figure 10 (a) indicates that the planar patch antenna is positioned in the vertical direction (in Figure 10 (a) shows four elements arranged vertically, and horizontally (in) Figure 10 (a) is an example of a subarray with one element arranged horizontally. Figure 10 (b) indicates that the planar patch antenna is positioned in the vertical direction (in Figure 10 In (b), one element is arranged vertically, and in the horizontal direction (in... Figure 10 (b) is an example of a subarray with four elements arranged horizontally. Figure 10 (c) indicates that the planar patch antenna is positioned in the vertical direction (in Figure 10 (c) Four elements are arranged vertically, and horizontally (in Figure 10 (c) is an example of a subarray with two elements arranged horizontally.

[0252] exist Figure 10 In the middle, H ANT W represents the antenna size in the vertical direction. ANT This indicates the antenna dimensions in the horizontal direction. Furthermore, the structure of the subarray is not limited to... Figure 10 The structure shown, for example, can also have the same number of elements in the vertical and horizontal directions. Figure 10 The number shown is different.

[0253] When such a subarray antenna is used as a single antenna, either as a transmitting antenna 106 or a receiving antenna 202, it is difficult to configure the individual antennas at intervals smaller than the size of the subarray antenna.

[0254] For example, in configuration Figure 10When using the subarray antenna shown in (a), the size of the subarray antenna may be greater than one wavelength in the vertical direction. Therefore, it is possible to use a larger antenna configuration with an antenna spacing of more than one wavelength in the vertical direction. For example, as described later... Figure 11 , Figure 14 , Figure 16 and Figure 17 In this configuration, since the transmitting antennas 106 and the receiving antennas 202 are arranged so that they do not overlap in the vertical direction, it is possible to configure... Figure 10 Large subarray antennas in the vertical direction, like (a).

[0255] For example, in configuration Figure 10 When using the subarray antenna shown in (b), the size of the subarray antenna may be greater than one wavelength in the horizontal direction. Therefore, it is possible to use a larger antenna configuration with an antenna spacing of more than one wavelength in the horizontal direction. For example, the transmitting antenna in the antenna configurations described later, and the antennas described later... Figure 13 , Figure 17 and Figure 19 The receiving antennas shown are configured such that the transmitting antennas 106 and the receiving antennas 202 do not overlap in the horizontal direction, thus enabling configuration... Figure 10 (b) A subarray antenna with a large horizontal dimension.

[0256] For example, in configuration Figure 10 When using the subarray antenna shown in (c), the size of the subarray antenna may be greater than one wavelength in both the horizontal and vertical directions. Therefore, it is possible to use a larger antenna configuration with an antenna spacing of more than one wavelength in both the horizontal and vertical directions. For example, the transmitting antennas in the antenna configurations described later can be configured with large spacing in both the horizontal and vertical directions, thus enabling configurations... Figure 10 (c) is a subarray antenna with large dimensions in both the horizontal and vertical directions.

[0257] When the subarray antenna is used as a transmitting antenna 106 or a receiving antenna 202 as described above, in addition to the effects mentioned above, the directional gain of the antenna can also be improved.

[0258] [A variation of configuration example 1]

[0259] Furthermore, the same effect can be achieved even if Configuration Example 1 is modified in the following manner. The following is an explanation of a modified version of Configuration Example 1.

[0260] Figure 11 Figure (a) is a modified example of the MIMO antenna configuration of the transmitting antenna 106 and the receiving antenna 202 under configuration condition 1 described above. Figure 11In the example shown in (a), the number of transmitting antennas N Tx There are 2 antennas (e.g., Tx#1 and Tx#2), and the number of receiving antennas Na is 3 (e.g., Rx#1, Rx#2 and Rx#3).

[0261] Figure 11 (b) indicates through Figure 11 The diagram shows an example of a virtual receiving antenna configuration obtained from the antenna configuration shown in (a). The configuration of each virtual receiving antenna is based on... Figure 11 The antenna configuration shown in (a) is calculated by applying equation (12).

[0262] exist Figure 11 In (a), N Tx =The angle ψ between the two transmitting antennas Tx#1 and Tx#2 and the horizontal direction is (in Figure 11 In the example, ψ = 45°) is angled upwards at intervals D. t Configuration. Additionally, at least two of the three receiving antennas 202 (Na = 3) are positioned in the same direction as the oblique ψ along which the transmitting antennas Tx#1 to Tx#2 are arranged, with a spacing of D. r Configuration.

[0263] Here, it could be such that D t and D r The absolute value of the difference D d (=|D t -D r |) becomes an interval of approximately 0.5λ (D) d The transmitting antenna spacing D is set in the manner of ≒0.5λ (1 times the specified value). t and receiving antenna spacing D r .exist Figure 11 In, for example, by setting the interval D t =2λ, Interval D r =1.5λ, thus including an interval D of approximately 0.5λ in the virtual receiving antenna configuration. d Configuration condition A is met.

[0264] In addition, Figure 11 In (a), the receiving antenna Rx#3 is positioned horizontally at a distance D from the receiving antenna Rx#2. H The receiving antenna Rx#3 is positioned in a fourth direction, different from the horizontal, vertical, and oblique directions, relative to the receiving antenna Rx#1. It should be noted that the receiving antenna Rx#3 is positioned horizontally at an oblique distance D from the horizontal direction. H And in the vertical direction, the interval D is separated from the oblique ψ. V The position. Here, it is set to a horizontal interval D.H =λ / (2sinψ)≒0.7λ, thus satisfying configuration condition B. In Figure 11 In (a), the receiving antenna Rx#3 is not perpendicular to the receiving antennas Rx#1 or Rx#2 at a distance D. V They are arranged in a row and therefore do not meet configuration condition C.

[0265] Alternatively, for example, it could be in Figure 11 In (b), the difference between the aperture lengths of VA#1, VA#2, VA#4 and VA#5 (e.g., the first virtual receiving antenna group) and the aperture lengths of VA#3 and VA#6 (e.g., the difference between VA#3 to VA#6 and VA#1 to VA#5) is set to be equal to the value obtained by multiplying a predetermined value (e.g., 0.5λ) by a predetermined number.

[0266] Additionally, in the number of transmitting antennas N Tx If there are three or more antennas, at least two (e.g., Tx#1 and Tx#2) need to meet the above configuration conditions. Additionally, if there are three or more receiving antennas Na, at least three (e.g., Rx#1, Rx#2, and Rx#3) need to meet the above configuration conditions.

[0267] An example of the direction estimation processing in the direction estimation unit 213 when the antenna configuration described above is applied will be explained. For example, the direction estimation unit 213 uses the received signal DeMul, which has undergone code multiplexing and demultiplexing processing on the code multiplexed signal transmitted from the transmitting antenna 106. z ncm (f b_cfar f s_cfar ), to generate the virtual receiver array correlation vector h(f) of the transmitting antenna 106 shown in equation (13). b_cfar f s_cfar The direction estimation unit operates in the same way as in Application Configuration Example 1, and therefore its description is omitted.

[0268] <Example of direction estimation results for a variation of Configuration Example 1>

[0269] Next, an example of the directional estimation result (computer simulation result) when a modified antenna configuration of the above configuration example 1 is applied will be described.

[0270] Figure 12 (a) and (b) indicate that in Figure 11 The example shown in (a) illustrates the angle measurement results based on beamforming when receiving reflected waves from a target in the horizontal direction of 0° and the vertical direction of 40° in the antenna configuration of the MIMO radar. Figure 12 (a) and (b) are the same as the angle measurement results of Configuration Example 1 (e.g., Figure 8 The object conditions of (a) and (b) are the same, and they are plotted using the same chart.

[0271] Depend on Figure 12 As shown in (a) and (b), the main beam is oriented at 0° horizontally and 40° vertically, and no grating lobes are generated. Furthermore, in... Figure 11 In the case of the MIMO radar antenna configuration shown in (a), the horizontal beamwidth is approximately 17° and the vertical beamwidth is approximately 18° (when the Fourier beam pattern is oriented towards 0° horizontally and 0° vertically). Therefore, in Figure 11 In antenna configuration (a), with Figure 1 Compared to the previous antenna configuration, the 3dB beamwidth in the horizontal direction is reduced to 46% (=17 / 37) and the 3dB beamwidth in the vertical direction is reduced to 31% (=18 / 59). Therefore, it is expected to improve the two-dimensional angle measurement accuracy in both the horizontal and vertical directions (for example, to achieve an accuracy improvement of about 2.2 to 3.3 times).

[0272] As described above, in the antenna configuration of the modified example of configuration example 1, by satisfying configuration conditions A and B, the same effect as configuration example 1 can be obtained.

[0273] In addition, Figure 11 The document describes the conditions for meeting configuration conditions A and B, but it is not limited to these conditions. As long as configuration condition A is met, at least one of configuration conditions B and C is also met. Figure 13 (a) is an example of an antenna configuration that satisfies configuration conditions A and C. For example, as... Figure 13 As shown in (a), Rx#2 (e.g., corresponding to the r2nd antenna) and Rx#3 (e.g., corresponding to the r3rd antenna) are arranged in a direction different from the horizontal direction, the vertical direction, and the oblique direction ψ (e.g., corresponding to the fourth direction). Additionally, Rx#1 (e.g., corresponding to the r1st antenna) and Rx#3 (e.g., corresponding to the r3rd antenna) are arranged in the vertical direction (e.g., corresponding to the second direction). Furthermore, the receiving antenna Rx#3 is arranged at a horizontal distance of D from the oblique direction ψ. H And in the vertical direction, the interval D is separated from the oblique ψ. V The location. Furthermore. Figure 13 (b) indicates through Figure 13 The diagram shows an example of a virtual receiving antenna configuration obtained from the antenna configuration shown in (a). For example, it could be in... Figure 13In (b), the difference between the aperture lengths of VA#1, VA#2, VA#4, and VA#5 (e.g., the first virtual receiving antenna group) and the aperture lengths of VA#3 and VA#6 (e.g., the difference between VA#3 to VA#6 and VA#1 to VA#5) is set to be equal to the value obtained by multiplying a predetermined value (e.g., 0.5λ) by a predetermined number. Figure 13 The antenna configuration shown can also achieve the same effect as configuration example 1, which can suppress grating lobes.

[0274] [A simplified example of a two-dimensional angle measurement method]

[0275] The following is an example of operation when a simplified two-dimensional angle measurement method is applied in the direction estimation unit 213.

[0276] (1) The direction estimation unit 213 performs one-dimensional FFT processing on the received signal of the virtual receiving antenna configured in the oblique direction ψ that satisfies the configuration condition A, and calculates the spatial spectrum H. A (m). Here, m = 1, ..., N FFT N FFT Indicates the FFT size.

[0277] Then, the direction estimation unit 213 extracts the spatial spectrum H. A The FFT index m that becomes the peak value on (m) peakA Here, m peakA It is H A (m) is the largest index m. For example, Figure 7 The virtual receiving antennas VA#1, VA#2, VA#4, and VA#5 shown in (b) satisfy configuration condition A. Furthermore, VA#2 and VA#4 are spaced at interval D. d (e.g., 0.5λ) configuration. The direction estimation unit 213, for example, uses interval D... d The spatial sampling interval is set to perform one-dimensional FFT processing on the received signal of the virtual receiving antenna configured on the oblique direction ψ that meets the configuration condition A.

[0278] Furthermore, in the absence of interval D d In the case of a virtual receiving antenna, the direction estimation unit 213 can also perform FFT processing by zero-padding. For example, the receiving vector h shown in equation (18) below... A based on Figure 7 The received signal h of the virtual receiving antennas VA#1, VA#2, VA#4, and VA#5 configured obliquely upwards in (b) satisfies configuration condition A. VA#1 h VA#2 h VA#4 h VA#5 And is represented. Additionally, the received signal h VA#nThe virtual receiver array correlation vector h(f) represents the vector h(f) of the virtual receiver array. b_cfar f s_cfar The nth element of ).

[0279] h A =[h VA#1 0 h VA#2 h VA#4 0 h VA#5 ] T (18)

[0280] The direction estimation unit 213 can, for example, use zero-padding to make the FFT size a specified power of 2, the size N. FFT The received vector h up to date Azeropad To perform FFT processing. The spatial spectrum H in this case... A (m) is represented by the following equation (19). Here, m represents the FFT index. m = -N FFT / 2,…,N FFT / 2+1. Here, h AZeroPad,n Represents the received vector h AZeropad The nth element.

[0281]

[0282] Direction estimation unit 213 calculates the spatial spectrum H A The FFT index m that becomes the peak value on (m) peakA Phase change at FFT peakPhase(m) PeakA Here, the spatial spectrum H A The FFT index m that becomes the peak value on (m) peakA Phase change at FFT peakPhase(m) PeakA ) represents the spatial sampling interval D. d The phase change depends on the azimuth and elevation angles of the reflected wave from the target. For example, in the case of performing the FFT processing shown in equation (19) above, FFTpeakPhase(m PeakA ) is represented by the following formula (20).

[0283]

[0284] Thus, the direction estimation unit 213 uses the received signals from the virtual receiving antennas (e.g., virtual receiving antennas configured in the oblique direction ψ) that satisfy configuration condition A among the multiple virtual receiving antennas to calculate the direction at intervals D. d Phase change.

[0285] (2) The direction estimation unit 213 uses the received signals from at least two of the virtual receiving antennas configured in the horizontal direction that satisfy configuration condition B to calculate the phase difference diffPhase in the horizontal direction. H (θ). For example, in Figure 7 In the virtual receiving antennas of (b), the virtual receiving antennas configured in the horizontal direction that satisfy configuration condition B are VA#5 and VA#6. The phase difference diffPhase in the horizontal direction is calculated according to the following formula (21). H (θ0). Here, arg[x] is the operator representing the argument of the complex number x. Additionally, the superscript * (asterisk) is the operator representing complex conjugation.

[0286]

[0287] Alternatively, the integer N that satisfies the phase difference conditions shown in equation (21) above and equation (22) below can also be used. ambiguityH Included, and considered as a candidate for phase difference in the horizontal direction. For example, when N is in equation (22) ambiguityH When =0, it corresponds to equation (21). Therefore, the phase difference candidates in the horizontal direction, including the true value direction and the grating lobe direction, are calculated.

[0288]

[0289] Where, N ambiguityH It is to satisfy Integers.

[0290] In addition, Figure 7 In (b), in addition to VA#5 and VA#6, VA#2 and VA#3 are also included as a combination of virtual receiving antennas configured in the horizontal direction to satisfy configuration condition B. The direction estimation unit 213 can also use the received signals of VA#2 and VA#3 to calculate the horizontal phase difference diffPhase. H Alternatively, multiple phase differences (diffPhase) can be used. H The average value.

[0291] (3) The direction estimation unit 213 uses the received signals from at least two of the virtual receiving antennas configured in the vertical direction that satisfy the configuration condition C to calculate the phase difference in the vertical direction. For example, in Figure 7 In the virtual receiving antennas of (b), the virtual receiving antennas configured in the vertical direction that satisfy configuration condition C are VA#1 and VA#3. The phase difference in the vertical direction is calculated according to the following formula (23).

[0292]

[0293] Alternatively, the integer N that satisfies the phase difference conditions shown in equation (23) above and equation (24) below can also be used. ambiguityV Included, and considered as a candidate for phase difference in the vertical direction. For example, when N is in equation (24) ambiguityV When =0, it corresponds to equation (23). Therefore, the candidate phase difference in the vertical direction, including the true value direction and the grating lobe direction, is calculated.

[0294]

[0295] Where, N ambiguityV It is to satisfy Integers.

[0296] In addition, Figure 7 In (b), in addition to VA#1 and VA#3, VA#4 and VA#6 are also included as a combination of virtual receiving antennas configured in the vertical direction to satisfy configuration condition C. The direction estimation unit 213 can also use the received signals of VA#4 and VA#6 to calculate the phase difference in the vertical direction. Alternatively, multiple phase differences (diffPhase) can be used. V The average value.

[0297] In addition, if there is no virtual receiving antenna in a vertical configuration that satisfies configuration condition C, the radar device 10 can also use a virtual receiving antenna configured in the oblique direction ψ other than the virtual receiving antenna that satisfies configuration condition A, and apply interpolation processing to obtain the received signal of the virtual receiving antenna in a vertical configuration that satisfies configuration condition C.

[0298] For example, Figure 11 (b) is an example where there is no virtual receiving antenna in the vertical configuration that satisfies configuration condition C. In this case, for example, the direction estimation unit 213 can use interpolation processing to determine the virtual receiving antenna in the vertical configuration that satisfies configuration condition C relative to VA#1 (in Figure 11 In (b), point P is located. Hereinafter, the received signal is denoted as "VA#P".

[0299] For example, when in one of the vertical and horizontal directions (in) Figure 11 When there are not at least two virtual receiving antennas configured in the vertical direction (in the middle), the direction estimation unit 213 can perform a calculation using a second virtual receiving antenna group (in the middle). Figure 11 (b) describes the interpolation processing of the received signal from one of the virtual receiving antennas (VA#3 and VA#6) to calculate the signal in that direction (in Figure 11 The phase difference (in the vertical direction) is shown in the middle.

[0300] For example, in Figure 11In (b), VA#3 and point P are located on the oblique direction ψ, and VA#3 and point P are separated by a distance D. d Configuration. Therefore, as shown in equation (25), it is possible to receive the signal h for VA#3. VA#3 The spatial sampling interval D of the target arrival wave was calculated using a virtual receiving antenna that satisfies configuration condition A. d Phase change FFT peakPhase(m) PeakA The interpolation process is used to calculate the received signal h of VA#P. VA#P .

[0301]

[0302] Or, for example, in Figure 11 In (b), VA#6 and point P are located on the oblique direction ψ, and VA#6 and point P are separated by a distance of 5D. d Configuration. Therefore, as shown in equation (26), it is possible to receive the signal h for VA#6. VA#6 The FFTpeakPhase(m) method was used. PeakA The interpolation process is used to calculate the received signal h of VA#P. VA#P .

[0303]

[0304] Alternatively, the direction estimation unit 213 may, for example, be as shown in equation (27), to estimate the direction of multiple virtual receiving antennas located on the oblique direction ψ (e.g., in...). Figure 11 In (b), the interpolated signals of VA#3 and VA#6 are further summed and output. In this case, by performing summation and averaging to improve the SNR (Signal-to-Noise Power Ratio) of the received signal, the accuracy of interpolation can be improved.

[0305]

[0306] Furthermore, while the case where a vertically configured virtual receiving antenna satisfying configuration condition C is not described here, the same applies when a horizontally configured virtual receiving antenna satisfying configuration condition B is not present. Interpolation using virtual receiving antennas arranged diagonally in the direction ψ (other than the virtual receiving antenna satisfying configuration condition A) can be applied to calculate the received signal of the horizontally configured virtual receiving antenna satisfying configuration condition B. Additionally, for the configuration examples or variations described later, the same interpolation process can be applied even when a virtual receiving antenna satisfying configuration condition B or configuration condition C is not present.

[0307] (4) The direction estimation unit 213 calculates the horizontal phase difference diffPhase based on the virtual receiving antenna that satisfies configuration condition B. H (θ NambiguityH The phase difference in the vertical direction calculated based on a virtual receiving antenna that satisfies configuration condition C. The combination of the spatial sampling interval D of the target arrival wave calculated based on the virtual receiving antenna satisfying configuration condition A. d Phase change FFT peakPhase(m) PeakA Corresponding (e.g., consistent) combinations are used to extract the horizontal and vertical angles of arrival.

[0308] The horizontal phase difference diffPhase is calculated based on the virtual receiving antenna that satisfies configuration condition B. H (θ NambiguityH And the phase difference in the vertical direction calculated based on the virtual receiving antenna that satisfies configuration condition C. The spatial sampling interval D d The phase change is shown by the following equation (28). Indicated. The direction estimation unit 213, for example, can use FFT peakPhase(m) PeakA )and The absolute value of the difference between them is the horizontal phase difference diffPhase with the smallest horizontal direction. H (θ NambiguityH Phase difference in the vertical direction The object direction corresponding to the combination of values ​​is used as the estimated value of the object direction.

[0309]

[0310] The above explains the operation of the simplified two-dimensional angle measurement method in the direction estimation unit 213.

[0311] The above explains Configuration Example 1 and its variations.

[0312] <Configuration Example 2>

[0313] Figure 14 Figure (a) is a diagram illustrating an example configuration of the MIMO antennas for the transmitting antenna 106 and the receiving antenna 202 under the above configuration conditions. Figure 14 In the example shown in (a), the number of transmitting antennas N Tx There are 2 antennas (e.g., Tx#1 and Tx#2), and the number of receiving antennas Na is 3 (e.g., Rx#1, Rx#2 and Rx#3).

[0314] Figure 14 (b) indicates through Figure 14The diagram shows an example of a virtual receiving antenna configuration obtained from the antenna configuration shown in (a). The configuration of each virtual receiving antenna is based on... Figure 14 The antenna configuration shown in (a) is calculated by applying equation (12).

[0315] exist Figure 14 In (a), N Tx =The angle ψ between the two transmitting antennas Tx#1 and #2 and the horizontal direction is (in Figure 14 In (a), ψ = 45° is inclined upwards, with interval D. t Configuration. Additionally, it is not limited to an oblique angle of ψ = 45°; for example, it can also be set to approximately ψ = 30° to 60°.

[0316] In addition, Figure 14 In (a), Na = at least two of the three receiving antennas Rx#1 to #2 are positioned in the same direction as the oblique ψ along which the transmitting antennas Tx#1 to #2 are arranged, with a spacing of D. r Configuration.

[0317] Here, the transmit antenna spacing D can be... t Set the interval to approximately 4 times the spacing of 0.5λ, and set the receiving antenna spacing D. r The interval is set to approximately 0.5λ. This establishes the transmitting antenna interval D. t and receiving antenna spacing D r As far as D is concerned, t and D r The absolute value of the difference D d (=|D t -D r |) becomes an integer multiple (3 times) of the interval approximately 0.5λ, by setting it as the receiving antenna interval D. r =0.5λ, thus including an interval D of approximately 0.5λ in the virtual receiving antenna configuration. d Configuration condition A is met.

[0318] In addition, Figure 14 In (a), the receiving antenna Rx#3 is positioned horizontally at a distance (horizontal distance) D from the receiving antenna Rx#1. H The location. Additionally, the receiving antenna Rx#3 is positioned horizontally at a distance D from the diagonal ψ. H And in the vertical direction, the interval D is separated from the oblique ψ. V The position. Here, it is set to a horizontal interval D. H =λ / (2sinψ)≒0.7λ (where ψ is 45°), thus satisfying configuration condition B. Figure 14 In (a), the receiving antenna Rx#3 is not perpendicular to the receiving antennas Rx#1 or Rx#2 at a distance D.V Arranged in a row, therefore Figure 14 The virtual receiving antenna configuration shown in (b) does not include the vertical direction at intervals D. V An antenna configuration arranged in a row does not meet configuration condition C.

[0319] As mentioned above, in Figure 14 In (a), the transmitting antennas Tx#1 and Tx#2 are configured obliquely along ψ. Additionally, in Figure 14 In (a), the two receiving antennas Rx#1 and Rx#2 are positioned obliquely along ψ at a distance D. r (For example, 0.5λ) configuration. Furthermore, in Figure 14 In (a), Rx#3 and Rx#1 are spaced D apart in the horizontal direction. H (by D) r =0.5λ (larger interval) configuration.

[0320] In addition, such as Figure 14 As shown in (b), VA#1, VA#2, VA#4 and VA#5 are arranged diagonally along ψ, with the interval between two adjacent VA#1 and VA#2 being D. d (=0.5λ). Additionally, such as... Figure 14 As shown in (b), VA#1 and VA#3 (or VA#4 and VA#6) are arranged horizontally, and the spacing between VA#1 and VA#3 (or the spacing between VA#4 and VA#6) in the horizontal direction is greater than D. d Big D H .therefore, Figure 14 The virtual receiving antenna shown in (b) satisfies configuration conditions A and B.

[0321] Additionally, in the number of transmitting antennas N Tx If there are three or more antennas, at least two (e.g., Tx#1 and Tx#2) need to meet the above configuration conditions. Additionally, if there are three or more receiving antennas Na, at least three (e.g., Rx#1, Rx#2, and Rx#3) need to meet the above configuration conditions.

[0322] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described configuration example 2 is applied will be described.

[0323] For example, the direction estimation unit 213 uses the received signal DeMul, which has undergone code multiplexing and demultiplexing processing on the code multiplexed signal transmitted from the transmitting antenna 106. z ncm (f b_cfar f s_cfar ), to generate the virtual receiver array correlation vector h(f) of the transmitting antenna 106 shown in equation (13). b_cfarf s_cfar The direction estimation unit 213 operates in the same way as in the application configuration example 1, and therefore its description is omitted.

[0324] <Example of orientation estimation results in Configuration Example 2>

[0325] Next, an example of the directional estimation result (computer simulation result) when the antenna configuration of the above configuration example 2 is applied will be explained.

[0326] Figure 15 (a) and (b) indicate that in Figure 14 In the antenna configuration of the MIMO radar shown in (a), the angle measurement results based on beamforming method are received when the reflected waves from the target in the horizontal direction of 0° and the vertical direction of 40° are received. Figure 15 (a) and (b) are the same as the angle measurement results of Configuration Example 1 (e.g., Figure 8 The object conditions of (a) and (b) are the same, and they are plotted using the same chart.

[0327] Depend on Figure 15 As shown in (a) and (b), the main beam is oriented at 0° horizontally and 40° vertically, and no grating lobes are generated. Furthermore, in... Figure 14 In the case of the MIMO radar antenna configuration shown in (a), the horizontal beamwidth is approximately 18° and the vertical beamwidth is approximately 20° (when the Fourier beam pattern is oriented towards 0° horizontally and 0° vertically). Therefore, in Figure 14 In antenna configuration (a), with Figure 1 Compared to the previous antenna configuration, the 3dB beamwidth in the horizontal direction is reduced to 66% (=18 / 37) and the 3dB beamwidth in the vertical direction is reduced to 34% (=20 / 59). Therefore, it is expected to improve the two-dimensional angle measurement accuracy in both the horizontal and vertical directions (for example, to achieve an accuracy improvement of about 1.5 to 3 times).

[0328] As described above, in configuration example 2, by satisfying configuration conditions A and B, the same effect as in configuration example 1 can be obtained.

[0329] in addition, Figure 14 The antenna configuration shown in (a) is an example of an antenna configuration that satisfies configuration conditions A and B, but is not limited thereto. Any antenna configuration that satisfies configuration condition A and at least one of configuration conditions B and C is acceptable.

[0330] For example, Figure 16 The antenna configuration shown in (a) is a variation of configuration example 2 that satisfies configuration conditions A, B and C. Figure 16 (b) indicates through Figure 16 The diagram shows an example of a virtual receiving antenna configuration obtained from the antenna configuration shown in (a). Using... Figure 16 The antenna configuration shown in (a) can also achieve the same effect as configuration example 2, and can remove grating lobes.

[0331] In addition, Figure 16 In the antenna configuration shown in (a), although Rx#3 is not perpendicular to Rx#1 or Rx#2 at a distance D V Arranged in a row and configured, but as Figure 16 As shown in (b), in the virtual receiving antenna configuration, virtual receiving antennas VA#2 and VA#6 are spaced D apart in the vertical direction. V They are arranged in a row. In this way, by adjusting the positional relationship between the configuration of the transmitting antenna 106 and the receiving antenna 202, it becomes possible to satisfy either configuration condition B or configuration condition C.

[0332] The above explains configuration example 2 and its variations.

[0333] <Configuration Example 3>

[0334] In Configuration Examples 1 and 2 described above, an antenna structure was described for the obliquely upward-arranged receiving antenna 202, which was arranged in a row with other receiving antennas 202 arranged in the horizontal direction, in order to satisfy configuration condition B. Furthermore, in Configuration Examples 1 and 2, an antenna structure was described for the obliquely upward-arranged receiving antenna 202, which was arranged in a row with other receiving antennas 202 arranged in the vertical direction, in order to satisfy configuration condition C.

[0335] In Configuration Example 3, a method will be described to obtain the same effect as when configuration conditions B and C are met by adopting a MIMO antenna configuration that satisfies the following configuration conditions instead of the MIMO antenna configuration in the above configuration example. Furthermore, in the following text, the configuration conditions corresponding to configuration conditions B and C will be referred to as "Configuration Condition B1" and "Configuration Condition C1," respectively.

[0336] In addition, in configuration example 3, configuration condition A can be the same as in configuration examples 1 and 2.

[0337] [Configuration Condition B1]

[0338] At least one of the other receiving antennas, different from the receiving antenna configured in the oblique direction ψ according to configuration condition A, is configured in a position on a straight line passing through point P in the oblique direction ψ, at a distance D from point P. d The position after an integer multiple of the interval offset, point P is located horizontally at a distance D relative to the receiving antenna configured on the oblique ψ. H point.

[0339] For example, among the plurality of receiving antennas 202, another receiving antenna (e.g., corresponding to the second receiving antenna), which is different from the two receiving antennas (e.g., corresponding to the first receiving antenna) configured on the oblique direction ψ, is configured at a position that is spaced D from position P on the oblique direction ψ passing through position P. d The position P is an integer multiple of the first receiving antenna mentioned above, and is horizontally separated by a distance D. H (by D) d (Larger intervals) in the position.

[0340] For example, a receiving antenna configured along the oblique ψ direction (e.g., described later). Figure 17 At least one of the receiving antennas other than (a) Rx#1 and Rx#2) (e.g., Figure 17 (a) Rx#3) is configured in a position that is offset from point P by an interval D on a straight line diagonally ψ passing through point P. s ( Figure 17 In (a), D is... s =2D d The position after ) is point P( Figure 17 In (a), point P1) is relative to the receiving antenna configured on the oblique ψ direction (e.g., Figure 17 (a) of Rx#2) is separated by a horizontal interval D in the horizontal direction. H The point. Here, the horizontal interval D H It can be set as λ / (2sinψ)≧D H >λ / 2.

[0341] Additionally, if set to D H If the value is greater than λ / (2sinψ), then grating lobes may be generated within a specific azimuth / elevation range. When the radar detection area is wide-angle, false detections may occur due to grating lobes. However, when the radar detection area is a relatively narrow region near the front, it is not affected by grating lobes and has no negative impact on radar detection performance. Therefore, it can also be set to D. H >λ / (2sinψ).

[0342] [Configuration Condition C1]

[0343] At least one of the other receiving antennas, different from the receiving antenna configured in the oblique direction ψ according to configuration condition A, is configured in a position on a straight line passing through point P in the oblique direction ψ, at a distance D from point P. d The position after an integer multiple of the interval offset, point P is located with respect to the receiving antenna configured on the oblique ψ, separated by a vertical interval D in the vertical direction. V point.

[0344] For example, among the plurality of receiving antennas 202, another receiving antenna (e.g., corresponding to the second receiving antenna), which is different from the two receiving antennas (e.g., corresponding to the first receiving antenna) configured on the oblique direction ψ, is configured at a position that is spaced D from position P on the oblique direction ψ passing through position P. d The position P is an integer multiple of the first receiving antenna mentioned above, and is located vertically separated by a distance D. V (by D) d (Larger intervals) in the position.

[0345] For example, a receiving antenna configured along the oblique ψ direction (e.g., described later). Figure 17 At least one of the receiving antennas other than (a) Rx#1 and Rx#2) (e.g., Figure 17 (a) Rx#3) is configured in a position that is offset from point P by an interval D on a straight line diagonally ψ passing through point P. s ( Figure 17 In (a), D is... s =D d The position after ) is point P( Figure 17 In (a), point P2) is relative to the receiving antenna configured on the oblique ψ direction (e.g., Figure 17 (a) of Rx#1) is separated by a vertical interval D in the vertical direction. V The point. Here, the vertical interval D V It can be set as λ / (2cosψ)≧D V >λ / 2. Additionally, the receiving antenna Rx#3 is configured at a horizontal distance of ψ spaced apart by a gap D. H And in the vertical direction, the interval D is separated from the oblique ψ. V The location.

[0346] Additionally, if set to D V If the value is greater than λ / (2cosψ), then grating lobes may be generated within a specific azimuth / elevation range. When the radar detection area is wide-angle, false detections may occur due to grating lobes. However, when the radar detection area is a relatively narrow region near the front, it is not affected by grating lobes and has no negative impact on radar detection performance. Therefore, it can also be set to D. V >λ / (2cosψ).

[0347] The above explains configuration condition B1 and configuration condition C1.

[0348] With this antenna configuration, a virtual receiving antenna (hereinafter referred to as the "first oblique virtual receiving antenna") is configured, consisting of a receiving antenna configured in the oblique direction ψ according to configuration condition A and a transmitting antenna configured in the oblique direction ψ.

[0349] In addition to the first oblique virtual receiving antenna, a virtual receiving antenna (hereinafter referred to as the "second oblique virtual receiving antenna") is also configured on the oblique ψ, consisting of other receiving antennas besides the receiving antenna configured on the oblique ψ according to configuration condition A, and a transmitting antenna configured on the oblique ψ.

[0350] Here, the second oblique virtual receiving antenna (e.g., described later) Figure 17 (b) VA#3, VA#6) relative to the first oblique virtual receiving antenna (e.g., described later) Figure 17 (b) VA#1, VA#4, VA#2, VA#5) are offset horizontally by the horizontal interval D. H Or it was offset by a vertical spacing D in the vertical direction. V And configuration.

[0351] Thus, the virtual receiving antenna formed by the transmitting and receiving antennas of the radar device 10 includes, for example, a virtual receiving antenna positioned (hereinafter, corresponding to the second antenna group) at a distance D from position P along an oblique direction ψ passing through position P. d The position P is an integer multiple of the position, which is relative to at least one virtual receiving antenna in the virtual receiving antenna group (e.g., corresponding to the first virtual receiving antenna group) that satisfies configuration condition A, and is separated by a horizontal interval D. H (by D) d Larger intervals) or intervals D in the vertical direction V (by D) d (Larger intervals) in the position.

[0352] Therefore, the receiving antenna 202 is configured at point P (described later). Figure 17 In (b), the phase of the received signal at point P1 or point P2 can be calculated using the following interpolation process, which is configured to be offset from point P by an interval D. s The interpolation process is performed using the phase information of the receiving antenna 202 at the subsequent position and the phase change information of the received signal obtained in the first oblique virtual receiving antenna. In Configuration Example 3, by performing such interpolation, the same effect as when the receiving antenna 202 is configured at point P (e.g., Configuration Example 1 or Configuration Example 2) can be obtained, and therefore it can also be applied to simplify the two-dimensional angle measurement method. Therefore, when configuration condition B1 or configuration condition C1 is satisfied, the same effect as when configuration condition B or configuration condition C is satisfied can be obtained.

[0353] In addition, interval D s Set to become interval D dThe intervals are integer multiples of each other. Therefore, the interpolation processing in the simplified two-dimensional angle measurement method described above can be performed. By applying the simplified two-dimensional angle measurement method, the computational load in the direction estimation unit 213 can be reduced.

[0354] Alternatively, for example, the interval D can also be... s Set to become interval D d The interval is a rational multiple of the given interval. Therefore, the interpolation processing in the simplified two-dimensional angle measurement method described above can be performed. By applying the simplified two-dimensional angle measurement method, the computational load in the direction estimation unit 213 can be reduced.

[0355] Figure 17 Figure (a) is a diagram illustrating an example configuration of the MIMO antennas for the transmitting antenna 106 and the receiving antenna 202 under the above configuration conditions. Figure 17 In the example shown in (a), the number of transmitting antennas N Tx There are 2 antennas (e.g., Tx#1 and Tx#2), and the number of receiving antennas Na is 3 (e.g., Rx#1, Rx#2 and Rx#3).

[0356] Figure 17 (b) indicates through Figure 17 The diagram shows an example of a virtual receiving antenna configuration obtained from the antenna configuration shown in (a). The configuration of each virtual receiving antenna is based on... Figure 17 The antenna configuration shown in (a) is calculated by applying equation (12).

[0357] exist Figure 17 In (a), N Tx =The angle ψ between the two transmitting antennas Tx#1 and #2 and the horizontal direction is (in Figure 17 In (a), ψ = 45°, the angle is upward at interval D. t Configuration.

[0358] In addition, Figure 17 In (a), Na = at least two of the three receiving antennas Rx#1 to #2 are positioned in the same direction as the oblique ψ along which the transmitting antennas Tx#1 to #2 are arranged, with a spacing of D. r Configuration.

[0359] Here, it could be such that D t and D r The absolute value of the difference D d (=|D t -D r |) becomes an interval of approximately 0.5λ (1 times the specified value) (D) d The transmitting antenna spacing D is set in the manner of ≒0.5λ). t and receiving antenna spacing D r .exist Figure 17 In (a), for example, the interval is set to D. t =2λ, Interval D r =2.5λ. Therefore, as... Figure 17 As shown in (b), in the virtual receiving antenna configuration, there is an interval D of approximately 0.5λ. d Configuration condition A is met.

[0360] In addition, Figure 17 In (a), the receiving antenna Rx#3 is positioned on a straight line diagonally ψ passing through point P1, offset from point P1 by a distance D. s1 =2D d The position after that, point P1 is relative to the receiving antenna Rx#2 configured on the oblique direction ψ, separated by a horizontal interval D in the horizontal direction. H The point. Here, the horizontal interval D H =λ / (2sinψ)≒0.7λ (where ψ is 45°), which satisfies configuration condition B1.

[0361] In addition, Figure 17 In (a), the receiving antenna Rx#3 is positioned on a straight line diagonally ψ passing through point P2, offset from point P2 by a distance D. s2 =D d The position P2 is relative to the receiving antenna Rx#1 configured on the oblique ψ direction, separated by a vertical interval D in the vertical direction. V The point. Here, the vertical interval D V =λ / (2cosψ)≒0.7λ (where ψ is 45°), which satisfies the configuration condition C1.

[0362] In addition, it is not limited to the oblique angle ψ = 45°, for example, it can also be set to about 30° to 60°.

[0363] Additionally, in the number of transmitting antennas N Tx If there are three or more antennas, at least two (e.g., Tx#1 and Tx#2) need to meet the above configuration conditions. Additionally, if there are three or more receiving antennas Na, at least three (e.g., Rx#1, Rx#2, and Rx#3) need to meet the above configuration conditions.

[0364] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described configuration example 3 is applied will be described.

[0365] For example, the direction estimation unit 213 uses the received signal DeMul, which has undergone code multiplexing and demultiplexing processing on the code multiplexed signal transmitted from the transmitting antenna 106. z ncm (f b_cfar f s_cfar), to generate the virtual receiver array correlation vector h(f) of the transmitting antenna 106 shown in equation (13). b_cfar f s_cfar The direction estimation unit 213 operates the same as in the application configuration example 1, and therefore its description is omitted.

[0366] <Example of orientation estimation results in configuration example 3>

[0367] Next, an example of the directional estimation result (computer simulation result) when the antenna configuration of the above configuration example 3 is applied will be explained.

[0368] Figure 18 (a) and (b) indicate that in Figure 17 In the antenna configuration of the MIMO radar shown in (a), the angle measurement results based on beamforming method are received when the reflected waves from the target in the horizontal direction of 0° and the vertical direction of 40° are received. Figure 18 (a) and (b) are the same as the angle measurement results of Configuration Example 1 (e.g., Figure 8 The object conditions of (a) and (b) are the same, and they are plotted using the same chart.

[0369] Depend on Figure 18 As shown in (a) and (b), the main beam is oriented at 0° horizontally and 40° vertically, and no grating lobes are generated. Furthermore, in... Figure 17 In the case of the MIMO radar antenna configuration shown in (a), the horizontal beamwidth is approximately 14° and the vertical beamwidth is approximately 15° (when the Fourier beam pattern is oriented towards 0° horizontally and 0° vertically). Therefore, in Figure 17 In antenna configuration (a), with Figure 1 Compared to the previous antenna configuration, the 3dB beamwidth in the horizontal direction is reduced to 3.8% (=14 / 37) and the 3dB beamwidth in the vertical direction is reduced to 2.5% (=15 / 59). Therefore, it is expected to improve the two-dimensional angle measurement accuracy in both the horizontal and vertical directions (for example, to achieve an accuracy improvement of about 2.6 to 3.9 times).

[0370] As described above, in configuration example 3, by satisfying configuration condition A and at least one of configuration condition B1 and configuration condition C1, the same effect as in configuration example 1 can be obtained.

[0371] Furthermore, the antenna configuration in Example 3 is not limited to... Figure 17 Example of antenna configuration shown in (a).

[0372] For example, Figure 19 The antenna configuration shown in (a) is a variation of configuration example 3 that satisfies configuration conditions A, B1 and C1. Figure 19The antenna configuration shown in (a) is Figure 17 In (a), change them to D respectively. r =3D d D s1 =D d / 2、D s2 =D d The configuration after / 2. Figure 19 (b) indicates through Figure 19 The diagram shows an example of the configuration of the virtual receiving antenna obtained by the antenna configuration shown in (a).

[0373] In use Figure 19 The same effect as in configuration example 1 can be obtained with the antenna configuration shown in (a). Figure 19 In the antenna configuration shown in (a), the spacing D s1 and interval D s2 Set as D d / 2 is D d The interval is a rational multiple (1 / 2 times).

[0374] Additionally, the above configuration example 3 (for example, Figure 17 (a) and variations (e.g., Figure 19 The antenna configuration in (a) is an example of an antenna configuration that satisfies configuration conditions A, B1, and C1 for configuration example 1, but it is not limited to this. For example, it could also be an antenna configuration that satisfies configuration conditions A, B1, and C1 for configuration example 2 (e.g., set as receiving antenna spacing D). r (The interval is approximately 0.5λ). In this case, the same effect as in Configuration Example 2 can be obtained.

[0375] Additionally, in configuration example 3, the spacing D of the transmitting antennas 106 t It can be interval D d The interval D of the receiving antennas 202 is an integer multiple or a rational multiple. r It can be interval D d The distance D between point P on the straight line along the oblique direction ψ and the receiving antenna 202 is an integer multiple or rational multiple of ψ. s It can be interval D d Integer multiples or rational multiples.

[0376] The above explains configuration example 3.

[0377] Furthermore, in the above configuration examples 1, 2, and 3, a configuration example was described where the oblique angle ψ in configuration condition A was set to ψ = 45°, but the value of the oblique angle ψ is not limited to this. For example, Figure 20(a) and (b) represent the MIMO antenna configuration example and the virtual receiving antenna configuration example when the oblique ψ in configuration condition A is set to ψ = 30°. Figure 20 The antenna configuration shown in (a) satisfies configuration conditions A and B, and can achieve the same effect as the configuration example above.

[0378] For example, by setting the oblique angle ψ = 30°, the aperture length in the horizontal direction is increased more than that in the vertical direction, thus resulting in a greater improvement in the accuracy of the horizontal direction estimation. For example, in... Figure 20 In the case of the MIMO radar antenna configuration shown in (a), the horizontal beamwidth is approximately 16° and the vertical beamwidth is approximately 51° (when the Fourier beam pattern is oriented towards 0° horizontally and 0° vertically) (not shown). Therefore, in Figure 20 In antenna configuration (a), with Figure 1 Compared to the previous antenna configuration, the 3dB beamwidth in the horizontal direction is reduced to 43% (=16 / 37), and the 3dB beamwidth in the vertical direction is reduced to 86% (=51 / 59). The improvement in angle measurement accuracy in the horizontal direction (expected to be about 2.3 times the accuracy improvement) is greater than the improvement in angle measurement accuracy in the vertical direction (expected to be about 1.2 times the accuracy improvement).

[0379] The above describes one embodiment of this disclosure.

[0380] Furthermore, the structure of the radar device according to one embodiment of this disclosure is not limited to... Figure 5 The structure shown. For example, a radar device may not have a CFAR unit 211.

[0381] Furthermore, in one embodiment of this disclosure, the number N of transmitting antennas in the antenna configuration is described. Tx Parameters such as the number of receiving antennas Na, the spacing between antennas (e.g., transmitting antennas, receiving antennas, or dummy receiving antennas), and the slant angle ψ are just examples; they can also be set to other values.

[0382] In one embodiment of this disclosure, an example of using 0.5λ is illustrated as an antenna spacing, but the antenna spacing is not limited to 0.5λ and can also be other spacings around 0.5λ. For example, a spacing of around 0.5λ to 0.8λ can also be used.

[0383] Furthermore, in one embodiment of the radar apparatus of this disclosure, the radar transmitting unit and the radar receiving unit may also be configured in physically separate locations. Additionally, in one embodiment of the radar receiving unit of this disclosure, the direction estimation unit and other constituent units may also be independently configured in physically separate locations.

[0384] Although not illustrated, one embodiment of the radar device disclosed herein includes, for example, a CPU (Central Processing Unit), a storage medium such as ROM (Read Only Memory) storing a control program, and an operating memory such as RAM (Random Access Memory). In this case, the functions of the aforementioned parts are implemented by the CPU executing the control program. However, the hardware structure of the radar device is not limited to this example. For example, each functional unit of the radar device can also be implemented as an integrated circuit (IC). Each functional unit can be implemented independently on a single chip, or it can be implemented on a single chip in a manner that includes part or all of it.

[0385] Various embodiments have been described above with reference to the accompanying drawings, but this disclosure is not limited to these examples. Various modifications and alterations will be readily apparent to those skilled in the art within the scope of the claims, and these modifications and alterations should be understood to fall within the technical scope of this disclosure. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the disclosure.

[0386] In addition, the term "part" in the above embodiments can be replaced by other terms such as "...circuitry", "...assembly", "device", "unit" or "module".

[0387] In the above embodiments, examples of using hardware to constitute this disclosure have been described, but this disclosure can also be implemented by software with the cooperation of hardware.

[0388] Furthermore, the functional blocks used in the descriptions of the above embodiments are typically implemented as integrated circuits, i.e., LSIs (Large Scale Integration). Integrated circuits can also control the functional blocks used in the descriptions of the above embodiments and include input terminals and output terminals. These functional blocks can be monolithically implemented independently, or they can be monolithically implemented in a manner that includes some or all of them. Here it is referred to as "LSI," but depending on the level of integration, it can also be called "IC," "system LSI," "super LSI," or "ulira LSI."

[0389] Furthermore, the method of integrating LSIs is not limited to LSIs; dedicated circuits or general-purpose processors can also be used. Alternatively, FPGAs (Field Programmable Gate Arrays) can be used after LSI fabrication, or reconfigurable processors can be used to reconfigure the connections or settings of the circuit blocks within the LSI.

[0390] Furthermore, if advancements in semiconductor technology or other derived technologies lead to the development of integrated circuit technologies that can replace LSIs, these technologies could certainly be used to integrate functional blocks. There are also possibilities for applications such as biotechnology.

[0391] <Summary of this disclosure>

[0392] A radar device according to an embodiment of this disclosure includes: a transmitting circuit that transmits a transmitting signal using one of a first antenna group and a second antenna group; and a receiving circuit that receives a reflected wave signal of the transmitted signal reflected from an object using the other of the first antenna group and the second antenna group. The r1 and r2 antennas in the first antenna group are arranged adjacent to each other in a third direction, which is different from a first direction and different from a second direction orthogonal to the first direction. The t1 and t2 antennas in the second antenna group are arranged adjacent to each other in the third direction. The r3 antenna in the first antenna group is located at a position offset from the third direction towards both the first and second directions by an amount greater than a predetermined value based on the wavelength of the transmitted signal, wherein the absolute value of the difference between two intervals is the predetermined value, or the absolute value of the difference between the two intervals is an integer multiple of twice or more of the predetermined value and one of the two intervals is the predetermined value, wherein the two intervals are the interval between the r1 and r2 antennas and the interval between the t1 and t2 antennas.

[0393] In one embodiment of the radar device disclosed herein, when the first direction is horizontal, the second direction is vertical, and when the first direction is vertical, the second direction is horizontal.

[0394] In a radar device according to one embodiment of this disclosure, the first antenna group has 3 or 4 antennas, and the second antenna group has 2 or 3 antennas.

[0395] In a radar device according to an embodiment of this disclosure, the r1 antenna and the r3 antenna are configured in a second direction, wherein the spacing between the r1 antenna and the r3 antenna in the second direction is greater than the predetermined value.

[0396] In a radar device according to an embodiment of this disclosure, the r1 antenna and the r3 antenna are configured in a fourth direction, which is different from the first direction, the second direction and the third direction.

[0397] In a radar device according to an embodiment of this disclosure, a plurality of virtual receiving antennas composed of a first antenna group and a second antenna group include: a first virtual receiving antenna group configured in the third direction; and a second virtual receiving antenna group, which is different from the first virtual receiving antenna group and configured in a fifth direction parallel to the third direction, wherein at least one of the intervals between two adjacent virtual receiving antennas contained in the first virtual receiving antenna group is the predetermined value, and the interval between a virtual receiving antenna contained in the first virtual receiving antenna group and a virtual receiving antenna contained in the second virtual receiving antenna group in the first direction is larger than the predetermined value.

[0398] In a radar device according to an embodiment of this disclosure, the difference between the aperture length of the first virtual receiving antenna group and the aperture length of the second virtual receiving antenna group is equal to the value obtained by multiplying the predetermined value by a predetermined number.

[0399] In a radar device according to one embodiment of this disclosure, the specified value is 0.5 wavelength.

[0400] In a radar device according to an embodiment of this disclosure, the spacing between the r1 antenna and the r2 antenna is less than the wavelength / (2×sinψ) relative to the angle ψ formed by the first direction and the third direction.

[0401] In a radar device according to an embodiment of this disclosure, the spacing between the r1-th antenna and the r3-th antenna is less than the wavelength / (2×cosψ) relative to the angle ψ formed by the first direction and the third direction.

[0402] In a radar apparatus according to an embodiment of this disclosure, the receiving circuit performs the following processing: using the received signals from the virtual receiving antennas configured in the third direction among the plurality of virtual receiving antennas, calculates the phase change at intervals of a predetermined value; using the received signals from at least two virtual receiving antennas configured in the first direction among the plurality of virtual receiving antennas, calculates the phase difference in the first direction; using the received signals from at least two virtual receiving antennas configured in the second direction among the plurality of virtual receiving antennas, calculates the phase difference in the second direction; and extracts the angle of arrival in the first direction and the angle of arrival in the second direction based on a combination of the phase difference in the first direction and the phase difference in the second direction that corresponds to the phase change at intervals of the predetermined value.

[0403] In a radar device according to an embodiment of this disclosure, when the at least two virtual receiving antennas are not configured in one of the first and second directions, the receiving circuit calculates the phase difference in the certain direction by performing interpolation processing on the received signal using one of the virtual receiving antennas in the second virtual receiving antenna group.

[0404] In a radar device according to an embodiment of this disclosure, the interval between the r1-th antenna and the r2-th antenna is more than twice the predetermined value and is a value obtained by multiplying the predetermined value by a predetermined number; the interval between the t1-th antenna and the t2-th antenna is more than twice the predetermined value and is a value obtained by multiplying the predetermined value by a predetermined number.

[0405] In one embodiment of the radar device disclosed herein, the angle between the first direction and the third direction is a certain angle within the range of 30° or more and 60° or less.

[0406] An embodiment of the radar signal processing method disclosed herein includes the following steps: transmitting a transmitted signal using one of a first antenna group and a second antenna group; and receiving a reflected wave signal of the transmitted signal reflected from an object using the other of the first antenna group and the second antenna group. In the radar signal processing method, the r1 and r2 antennas in the first antenna group are configured adjacent to each other in a third direction, the third direction being different from a first direction and different from a second direction orthogonal to the first direction. The t1 and t2 antennas in the second antenna group are configured adjacent to each other in the third direction. The r3 antenna in the first antenna group is configured at a position offset from the third direction to the first direction and the second direction by an offset greater than a predetermined value based on the wavelength of the transmitted signal, respectively. The absolute value of the difference between the two intervals is the predetermined value, or the absolute value of the difference between the two intervals is an integer multiple of more than twice the predetermined value and one of the two intervals is the predetermined value. The two intervals are the interval between the r1 and r2 antennas and the interval between the t1 and t2 antennas.

[0407] In one embodiment of the radar signal processing method disclosed herein, when the first direction is horizontal, the second direction is vertical, and when the first direction is vertical, the second direction is horizontal.

[0408] In a radar signal processing method according to an embodiment of this disclosure, the first antenna group has 3 or 4 antennas, and the second antenna group has 2 or 3 antennas.

[0409] In a radar signal processing method according to an embodiment of this disclosure, the r2th antenna and the r3th antenna are configured in a second direction, and the spacing between the r2th antenna and the r3th antenna in the second direction is larger than the predetermined value.

[0410] In a radar signal processing method according to an embodiment of this disclosure, the r1 antenna and the r3 antenna are configured in a fourth direction, which is different from the first direction, the second direction and the third direction.

[0411] In a radar signal processing method according to an embodiment of this disclosure, a plurality of virtual receiving antennas composed of a first antenna group and a second antenna group include: a first virtual receiving antenna group configured in the third direction; and a second virtual receiving antenna group, which is different from the first virtual receiving antenna group and configured in a fifth direction parallel to the third direction, wherein at least one of the intervals between two adjacent virtual receiving antennas contained in the first virtual receiving antenna group is a predetermined value, and the interval between a virtual receiving antenna contained in the first virtual receiving antenna group and a virtual receiving antenna contained in the second virtual receiving antenna group in the first direction is larger than the predetermined value.

[0412] While various implementation methods have been described above, it is obvious that various changes in form or detail can be made without departing from the spirit of this disclosure. It should be understood that these modified examples also fall within the technical scope of this disclosure.

[0413] The entire contents of the specification, drawings and abstract of the specification contained in Japanese Patent Application No. 2024-091507, filed on June 5, 2024, are incorporated herein by reference.

[0414] Industrial applicability

[0415] This disclosure is suitable for use as a radar device for detecting wide-angle ranges.

Claims

1. A radar device, characterized by Possessing: a transmission circuit that transmits a transmission signal using one of a first antenna group and a second antenna group; and a reception circuit that receives a reflection wave signal of the transmission signal reflected by an object using the other of the first antenna group and the second antenna group, an r1th antenna and an r2th antenna in the first antenna group are arranged adjacent to each other in a third direction different from a first direction and different from a second direction orthogonal to the first direction, an t1th antenna and an t2th antenna in the second antenna group are arranged adjacent to each other in the third direction, an r3th antenna in the first antenna group is arranged at a position shifted from the third direction by a larger shift amount than a prescribed value based on a wavelength of the transmission signal in the first direction and the second direction, an absolute value of a difference between two intervals is the prescribed value, or the absolute value of the difference between the two intervals is an integer number of times larger than the prescribed value and one of the two intervals is the prescribed value, the two intervals being an interval between the r1th antenna and the r2th antenna and an interval between the t1th antenna and the t2th antenna.

2. The radar apparatus according to claim 1, wherein in a case where the first direction is a horizontal direction, the second direction is a vertical direction, in a case where the first direction is a vertical direction, the second direction is a horizontal direction.

3. The radar apparatus according to claim 1, wherein a number of antennas of the first antenna group is three or four, and a number of antennas of the second antenna group is two or three.

4. The radar apparatus according to claim 1, wherein the r1th antenna and the r3th antenna are arranged in the second direction, in the second direction, an interval between the r1th antenna and the r3th antenna is larger than the prescribed value.

5. The radar apparatus according to claim 1, wherein the r1th antenna and the r3th antenna are arranged in a fourth direction different from the first direction, the second direction, and the third direction.

6. The radar apparatus according to claim 1, wherein a plurality of virtual reception antennas constituted by the first antenna group and the second antenna group includes: a first virtual reception antenna group arranged in the third direction; and a second virtual reception antenna group different from the first virtual reception antenna group and arranged in a fifth direction parallel to the third direction, at least one of intervals between two virtual reception antennas adjacent to each other included in the first virtual reception antenna group is the prescribed value, an interval in the first direction between one virtual reception antenna included in the first virtual reception antenna group and one virtual reception antenna included in the second virtual reception antenna group is larger than the prescribed value.

7. The radar apparatus according to claim 6, wherein a difference between an aperture length of the first virtual reception antenna group and an aperture length of the second virtual reception antenna group is equal to a value obtained by multiplying the prescribed value by a prescribed number.

8. The radar apparatus according to claim 1, wherein The prescribed value is 0.5 wavelengths.

9. The radar device according to claim 1, wherein The interval between the r1th antenna and the r2th antenna is below the wavelength / (2 x sinψ) with respect to an angle ψ that the first direction makes with the third direction.

10. The radar device according to claim 4, wherein The interval between the r1th antenna and the r3th antenna is below the wavelength / (2 x cosψ) with respect to an angle ψ that the first direction makes with the third direction.

11. The radar device according to claim 6, wherein The reception circuitry performs the following processing: The phase change at intervals of the prescribed value is calculated using the reception signals of the virtual reception antennas configured in the third direction among the plurality of virtual reception antennas; The phase difference in the first direction is calculated using the reception signals of at least two virtual reception antennas configured in the first direction among the plurality of virtual reception antennas; The phase difference in the second direction is calculated using the reception signals of at least two virtual reception antennas configured in the second direction among the plurality of virtual reception antennas; and The angle of arrival in the first direction and the angle of arrival in the second direction are extracted based on the combination of the phase difference in the first direction and the phase difference in the second direction, which corresponds to the phase change at intervals of the prescribed value.

12. The radar device according to claim 11, wherein When the at least two virtual reception antennas are not configured in one of the first direction and the second direction, the reception circuitry calculates the phase difference in the one direction by performing an interpolation process using the reception signal of a certain virtual reception antenna among the second virtual reception antenna group.

13. The radar device according to claim 1, wherein The interval between the r1th antenna and the r2th antenna is above 2 times the prescribed value and is a value obtained by multiplying the prescribed value by a prescribed number, The interval between the t1th antenna and the t2th antenna is above 2 times the prescribed value and is a value obtained by multiplying the prescribed value by a prescribed number.

14. The radar device according to claim 1, wherein The angle that the first direction makes with the third direction is a certain angle in a range of above 30° and below 60°. The radar signal processing method includes the steps of:

15. A method of radar signal processing, the method comprising: Transmitting a transmission signal using one of a first antenna group and a second antenna group; And Receiving a reflection wave signal reflected by an object using the other of the first antenna group and the second antenna group, In the radar signal processing method, An r1th antenna and an r2th antenna in the first antenna group are configured adjacent to each other in a third direction, the third direction being different from a first direction and different from a second direction orthogonal to the first direction, An t1th antenna and an t2th antenna in the second antenna group are configured adjacent to each other in the third direction, ​ the r3th antenna of the first antenna group is disposed at a position shifted from the third direction by a larger shift amount than a prescribed value based on a wavelength of the transmission signal, toward the first direction and the second direction, respectively, an absolute value of a difference between two intervals is the prescribed value, or the absolute value of the difference between the two intervals is an integer number of 2 times or more of the prescribed value and one of the two intervals is the prescribed value, the two intervals being an interval between the r1th antenna and the r2th antenna and an interval between the t1th antenna and the t2th antenna. 16.The radar signal processing method according to claim 15, wherein in a case where the first direction is a horizontal direction, the second direction is a vertical direction, in a case where the first direction is a vertical direction, the second direction is a horizontal direction. 17.The radar signal processing method according to claim 15, wherein the number of antennas of the first antenna group is 3 or 4, and the number of antennas of the second antenna group is 2 or 3. 18.The radar signal processing method according to claim 15, wherein the r2th antenna and the r3th antenna are disposed in the second direction, in the second direction, an interval between the r2th antenna and the r3th antenna is larger than the prescribed value. 19.The radar signal processing method according to claim 15, wherein the r1th antenna and the r3th antenna are disposed in a fourth direction, the fourth direction being different from the first direction, the second direction, and the third direction. 20.The radar signal processing method according to claim 15, wherein a plurality of virtual receiving antennas constituted by the first antenna group and the second antenna group includes: a first virtual receiving antenna group disposed in the third direction; and a second virtual receiving antenna group different from the first virtual receiving antenna group and disposed in a fifth direction parallel to the third direction, at least one of intervals between two adjacent virtual receiving antennas included in the first virtual receiving antenna group is the prescribed value, an interval between one virtual receiving antenna included in the first virtual receiving antenna group and one virtual receiving antenna included in the second virtual receiving antenna group in the first direction is larger than the prescribed value.

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