Radar apparatus and radar signal processing method

Abstract

To improve angle measurement accuracy or resolution in a radar apparatus.SOLUTION: In a radar apparatus, an r1-th antenna and an r2-th antenna in a first antenna group are arranged adjacent to each other in a third direction different from both a first direction and a second direction, a t1-th antenna and a t2-th antenna in a second antenna group are arranged adjacent to each other in the third direction, an r3-th antenna in the first antenna group is arranged at a position shifted to a position wider than a prescribed value based on a wavelength of a transmission signal toward each of the first direction and the second direction from the third direction, an absolute value of a difference between an interval between the r1-th antenna and the r2-th antenna and an interval between the t1-th antenna and the t2-th antenna is a prescribed value, or the absolute value of the difference between 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 is an integer multiple of the prescribed value that is two or more, and either one of 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 is the prescribed value.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a radar device and a radar signal processing method. [Background technology]

[0002] In recent years, radar devices using short-wavelength radar transmission signals, including microwaves and millimeter waves, which can provide high resolution, have been studied. Furthermore, to improve outdoor safety, there is a demand for the development of radar devices that can detect small objects, such as pedestrians, over a wide angle range (e.g., called wide-angle radar devices).

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

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

[0005] Furthermore, a radar device has been proposed that includes, for example, a receiver and a transmitter that has multiple antennas (array antennas), and performs beam scanning by signal processing using the transmitting and receiving array antennas (sometimes referred to as MIMO (Multiple Input Multiple Output) radar) (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] J. Li, and P. Stoica, "MIMO Radar with Colocated Antennas", Signal Processing Magazine, IEEE Vol. 24, Issue: 5, pp. 106-114, 2007 [Non-patent document 2] Kazuo Shirakawa et al., "Automotive 3D Scanning Millimeter-Wave Radar," Fujitsu Ten Technical Report, Vol. 30, No. 1, 2012. [Non-patent document 3] M. Kronauge, H. Rohling, "Fast two-dimensional CFAR procedure", IEEE Trans. Aerosp. Electron. Syst., 2013, 49, (3), pp. 1817-1823 [Non-patent document 4] Direction-of-arrival estimation using signal subspace modeling Cadzow, JA; Aerospace and Electronic Systems, IEEE Transactions on Volume: 28 , Issue: 1 Publication Year: 1992 , Page(s): 64 - 79 Summary of the Invention [Problem to be solved by the invention]

[0007] However, there is room for further study on methods for improving the angle measurement accuracy or resolution in radar devices (for example, MIMO radars).

[0008] Non-limiting examples of the present disclosure contribute to providing a radar device and a radar signal processing method that can improve angle measurement accuracy or resolution. [Means for solving the problem]

[0009] A radar device according to an embodiment of the present disclosure includes a transmitting circuit that transmits a transmission 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 transmission signal reflected by an object using the other of the first antenna group and the second antenna group, wherein an r1 antenna and an r2 antenna of the first antenna group are arranged adjacent to each other in a third direction that is different from both a first direction and a second direction orthogonal to the first direction, a t1 antenna and a t2 antenna of the second antenna group are arranged adjacent to each other in the third direction, and an r3 antenna of the first antenna group is arranged adjacent to each other in the third direction. and the r1 antenna and the r2 antenna are positioned at positions shifted in each of the first direction and the second direction from the r1 antenna to a position wider than a specified value based on the wavelength of the transmission signal, and the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is the specified value, or the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is an integer multiple of the specified value that is 2 or more, and either the distance between the r1 antenna and the r2 antenna or the distance between the t1 antenna and the t2 antenna is the specified value.

[0010] These comprehensive or specific embodiments may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0011] According to an embodiment of the present disclosure, it is possible to improve the angle measurement accuracy or resolution in a radar device.

[0012] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0013] [Figure 1] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 2] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 3] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 4] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 5] Block diagram showing an example of the configuration of a radar device [Figure 6] FIG. 1 shows an example of a transmitted signal and a reflected wave signal when a chirp pulse is used. [Figure 7] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 8] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 9] Diagram showing an example of MIMO antenna placement [Figure 10] A diagram showing an example of a subarray configuration. [Figure 11] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 12] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 13] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 14] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 15] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 16] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 17] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 18] FIG. 10 is a diagram showing an example of a direction estimation result. [Figure 19] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. [Figure 20] A diagram showing an example of the arrangement of MIMO antennas and virtual receiving antennas. DETAILED DESCRIPTION OF THE INVENTION

[0014] A MIMO radar transmits signals (radar transmission waves) multiplexed using, for example, time division, frequency division, Doppler multiplexing, or code division from multiple transmission antennas (also called transmission array antennas).The MIMO radar then receives signals (radar reflected waves) reflected by surrounding objects using multiple reception antennas (also called reception array antennas), and separates and receives the multiplexed transmission signals from each received signal.By performing this processing, the MIMO radar can extract a propagation path response expressed as the product of the number of transmission antennas and the number of reception antennas, and performs array signal processing on these received signals as a virtual reception array.

[0015] In MIMO radar, by devising the arrangement of antenna elements in the transmitting and receiving array antennas, it is possible to configure a virtual receiving array antenna (hereinafter referred to as a virtual receiving array, MIMO virtual receiving array, virtual receiving antenna, or virtual receiving array antenna) whose maximum number is equal to the product of the number of transmitting antenna elements and the number of receiving antenna elements. This has the effect of increasing the effective aperture length of the array antenna with a small number of elements, thereby improving the angle measurement accuracy or resolution.

[0016] Furthermore, in addition to one-dimensional scanning (angle measurement) in the vertical or horizontal direction, MIMO radar can also be applied to two-dimensional beam scanning (angle measurement) in the vertical and horizontal directions (see, for example, Non-Patent Document 2).

[0017] Two-dimensional angle measurement can be used, for example, to determine obstacles, including their height, in ADAS (Advanced Driver Assistance Systems) applications, improving radar detection performance. However, because two-dimensional angle measurement uses antennas arranged two-dimensionally in the vertical and horizontal directions, more antennas are used than in one-dimensional angle measurement.

[0018] For example, by improving the accuracy of two-dimensional angle measurement in a MIMO radar configured with a small number of antennas, it is expected that the cost of a high-performance radar detection system will be reduced. Also, by using multiple MIMO radars configured with a small number of antennas, it is expected that the coverage area will be expanded and the cost of an ADAS system that monitors the entire surroundings of a vehicle, for example, will be reduced.

[0019] In one non-limiting embodiment of the present disclosure, a method (e.g., antenna arrangement) for improving the two-dimensional angle measurement accuracy of a MIMO radar configured using a small number of antennas (a limited number of antennas, for example, two transmitting antennas and three receiving antennas) will be described.

[0020] FIG. 1 shows an example of a transmitting and receiving antenna arrangement (hereinafter also referred to as a MIMO antenna arrangement) of a MIMO radar and a virtual receiving antenna arrangement. FIG. 1(a) shows two transmitting antennas (Tx#1 to Tx#2) arranged in the vertical direction (longitudinal direction in FIG. 1(a)) and three receiving antennas (Rx#1 to Rx#3) arranged in the horizontal direction (horizontal direction in FIG. 1(a)). In FIG. 1(a), the transmitting antennas are spaced apart at equal intervals (D V ) and the receiving antennas are arranged at equal intervals in the horizontal direction (D H ) is located.

[0021] FIG. 1(b) shows a virtual receiving antenna configured based on the antenna arrangement shown in FIG. 1(a). Note that a virtual receiving antenna arrangement configured based on a MIMO antenna arrangement is disclosed, for example, in Non-Patent Document 1. For example, the virtual receiving antenna shown in FIG. 1(b) is configured from six virtual antenna elements (VA#1 to VA#6) in which three antenna elements are arranged in the horizontal direction and two antenna elements are arranged in the vertical direction in a rectangular shape. In FIG. 1(b), the element spacings of the virtual receiving antenna in the horizontal and vertical directions are D H , D V The horizontal and vertical aperture lengths A of the virtual receiving array are H , A V are, respectively, A H =3D H , A V =D V This becomes:

[0022] Figure 2 shows the horizontal element spacing D in the antenna arrangement of the MIMO radar shown in Figure 1(a). H = 0.5λ, and the vertical element spacing D V = 0.5λ, the angle measurement results for a target in the horizontal 0° and vertical 0° directions are shown using the 2D Fourier method, using the received signal at the virtual receiving antenna shown in Figure 1(b). Assuming that each antenna is omnidirectional, Figure 2 shows the spatial profile representing the normalized received power in the horizontal and vertical directions, with the direction of the peak received power representing the target direction according to the 2D angle measurement. Note that λ is the wavelength of the radar carrier wave.

[0023] As shown in Figure 2, a main beam (main lobe) is formed in the horizontal 0° and vertical 0° directions, and the target direction is detected. Here, the narrower the beam width of the main beam, the more accurate the angle measurement and the better the angle separation performance for multiple targets. For example, in Figure 2, the 3 dB beam width (half-power width) in the horizontal direction is about 37°, and the 3 dB beam width (half-power width) in the vertical direction is about 59°.

[0024] In two-dimensional angle measurement using a MIMO radar configured with a smaller number of antennas (e.g., a limited number of antennas), the horizontal and vertical aperture lengths are not sufficiently secured, and the two-dimensional angle measurement accuracy is likely to be insufficient. For example, in the example antenna arrangement shown in Figure 1, the vertical aperture is narrower than the horizontal aperture, so the 3 dB beam width in the vertical direction is likely to be wide, and the angle measurement accuracy in the vertical direction is likely to be lower than the angle measurement accuracy in the horizontal direction. Also, for example, in Figure 1, if the antenna spacing in the vertical direction is increased, the 3 dB beam width in the vertical direction will narrow, improving the angle measurement accuracy, but grating lobes may occur.

[0025] For example, in the antenna arrangement of the MIMO radar shown in Fig. 1(a), the vertical antenna spacing D V =0.7λ, horizontal antenna spacing D H = 0.5λ, an example of the angle measurement result obtained by the 2D Fourier method using the received signal at the virtual receiving antenna in Figure 1(b) is shown. The example in Figure 3 shows the angle measurement result obtained by the 2D Fourier method for a target in the horizontal 0° and vertical 40° directions. As shown in Figure 3, main lobes are formed in the horizontal 0° and vertical 40° directions, and the target direction is detected. On the other hand, as shown in Figure 3, grating lobes (in the horizontal 0° and vertical -51° directions) occur in addition to the main beam. In Figure 3, the peak level of the grating lobes is equivalent to that of the main beam, making it difficult for the radar device to distinguish the true target direction.

[0026] Similarly, for example, in the antenna arrangement of the MIMO radar shown in FIG. 1(a), the antenna spacing in the vertical direction is D V = λ, horizontal antenna spacing D H= 0.5λ, an example of the angle measurement result by the 2D Fourier method using the received signal at the virtual receiving antenna of Fig. 1(b) is shown. The example of Fig. 4 shows the angle measurement result by the 2D Fourier method for a target in the horizontal 0° and vertical 40° directions, as in Fig. 3. As shown in Fig. 4, grating lobes occur along with the main lobe pointing in the target direction (horizontal 0° and vertical 40° directions). In the example of Fig. 4, the angular interval at which the main lobe and grating lobe occur is narrower than in Fig. 3. From Figs. 3 and 4, it can be seen that the antenna spacing D in the vertical direction V It can be seen that the larger the angle, the narrower the angular interval at which grating lobes occur.

[0027] Here, the vertical antenna spacing D V =0.7λ, horizontal antenna spacing D H = 0.5λ, the 3 dB beam width (half power width) for targets in the horizontal 0° and vertical 0° directions is about 37° in the horizontal direction and about 41° in the vertical direction. V = λ, horizontal antenna spacing D H = 0.5λ, the 3 dB beam width (half power width) for a target in the horizontal 0° and vertical 0° directions is approximately 37° in the horizontal direction and approximately 29° in the vertical direction.

[0028] In this way, when the antenna spacing in the vertical direction is increased beyond 0.5λ, the 3 dB beam width narrows and the vertical angle measurement accuracy improves, but grating lobes occur. For example, if the expected detection angle range is wider than the angle at which grating lobes occur, the radar device is more likely to erroneously detect false peaks caused by grating lobes within the detection angle range as targets, which can lead to a deterioration in radar detection performance. Furthermore, even if a grating lobe is outside the expected detection angle range, if the power of the reflected wave arriving from the grating lobe direction is sufficiently large, the radar device may erroneously detect a target as having arrived within the field of view, which can lead to a deterioration in radar detection performance.

[0029] Furthermore, when the antenna spacing in the horizontal direction is increased, the horizontal beam width is narrowed, as in the vertical direction described above, and the effect of improving the horizontal angle measurement accuracy or angular resolution is obtained. However, when the horizontal spacing is increased beyond 0.5 wavelengths, grating lobes occur, which can easily degrade radar detection performance.

[0030] For example, an antenna arrangement that can suppress grating lobes while widening the antenna spacing in the vertical or horizontal direction is expected.

[0031] In a non-limiting example embodiment of the present disclosure, an antenna arrangement that can suppress grating lobes while increasing the element spacing in at least one of the vertical and horizontal directions is described. By realizing such an antenna arrangement, it is possible to improve the angle measurement accuracy or resolution with a smaller number of antennas.

[0032] The radar device according to an embodiment of the present disclosure may be mounted on a moving object such as a vehicle. The radar device mounted on the moving object can be used, for example, as an advanced driver assistance system (ADAS) that improves collision safety, or as a sensor used to monitor the surroundings of the moving object during autonomous driving.

[0033] Furthermore, a radar device according to an embodiment of the present disclosure may be attached to a relatively high structure, such as a roadside utility pole or a traffic light, and can be used as a sensor in an assistance system that improves the safety of passing vehicles or pedestrians.

[0034] The radar device is not limited to these uses, and may be used for other purposes.

[0035] Hereinafter, an embodiment according to an example of the present disclosure will be described in detail with reference to the drawings. In the embodiment, the same components are denoted by the same reference numerals, and redundant descriptions thereof will be omitted.

[0036] Below, a radar device will be described in which a transmitting branch transmits different code-division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch separates each transmit signal and performs reception processing (for example, a MIMO radar configuration). However, the radar device configuration is not limited to this, and a configuration in which a transmitting branch transmits different frequency-division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch separates each transmit signal and performs reception processing. Similarly, a radar device configuration in which a transmitting branch transmits time-division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch performs reception processing.

[0037] Similarly, a configuration may be adopted in which a transmitting branch transmits different Doppler division multiplexed transmit signals from multiple transmitting antennas, and a receiving branch separates each transmit signal for reception processing.Similarly, a configuration may be adopted in which a transmitting branch transmits transmit signals multiplexed using a combination of at least two of code division multiplexing, time division multiplexing, and Doppler division multiplexing from multiple transmitting antennas, and a receiving branch separates each transmit signal for reception processing.

[0038] In the following, as an example, a configuration of a radar system using a frequency-modulated pulse wave such as a chirp pulse (also called fast chirp modulation) will be described. However, the modulation system is not limited to frequency modulation. For example, an embodiment of the present disclosure can also be applied to a radar system using a single pulse or a coded pulse.

[0039] [Radar device configuration] FIG. 5 is a block diagram showing an example of the configuration of a radar device 10 according to this embodiment.

[0040] The radar device 10 includes a radar transmitter (transmitting branch) 100 and a radar receiver (receiving branch) 200.

[0041] The radar transmitter 100 generates a radar signal (radar transmission signal) and transmits it to a plurality of transmitting antennas 106 (e.g., N txThe radar transmit signal is transmitted at a specified transmission period using a transmitting array antenna composed of 1000 MHz and 1000 MHz.

[0042] The radar receiver 200 receives reflected wave signals, which are radar transmission signals reflected by a target (object, not shown), using a receiving array antenna including a plurality (e.g., Na) of receiving antennas 202. The radar receiver 200 performs signal processing on the reflected wave signals received by each receiving antenna 202, for example, to detect the presence or absence of a target or estimate the arrival distance, Doppler frequency (e.g., relative velocity), and arrival direction of the reflected wave signals, and outputs information related to the estimation results (e.g., positioning information).

[0043] The target is an object to be detected by the radar device 10, and includes, for example, a vehicle (including two-wheeled and four-wheeled vehicles), a person, a block, or a curb.

[0044] [Configuration of radar transmitter 100] The radar transmitter 100 includes a radar transmission signal generator 101, a code generator 104, a phase rotator 105, and a transmission antenna .

[0045] The radar transmission signal generation unit 101 generates a radar transmission signal. The radar transmission signal generation unit 101 includes, for example, a modulation signal generation unit 102 and a VCO (Voltage Controlled Oscillator) 103. Each component of the radar transmission signal generation unit 101 will be described below.

[0046] The modulation signal generating unit 102 generates a sawtooth modulation signal (for example, a modulation signal for VCO control) for each radar transmission period Tr.

[0047] The VCO 103 generates a frequency modulation signal (hereinafter, referred to as a frequency chirp signal or chirp signal, for example) based on the modulation signal output from the modulation signal generating unit 102, as shown in (a) of FIG. 6, and outputs it to the phase rotation unit 105 and the radar receiving unit 200 (a mixer unit 204, which will be described later).

[0048] The code generation unit 104 generates a different code for each transmitting antenna 106 that performs code multiplexing transmission. The code generation unit 104 outputs the amount of phase rotation corresponding to the generated code to the phase rotation unit 105. The code generation unit 104 also outputs information about the generated code to the radar receiving unit 200 (the output switching unit 209, which will be described later).

[0049] The phase rotation unit 105 applies the phase rotation amount input from the code generation unit 104 to the chirp signal input from the VCO 103, and outputs the phase-rotated signal to the transmitting antenna 106. For example, the phase rotation unit 105 includes, for example, a phase shifter and a phase modulator (not shown). The output signal from the phase rotation unit 105 is amplified to a specified transmission power and radiated into space from each transmitting antenna 106. For example, a radar transmission signal is code-multiplexed and transmitted from the multiple transmitting antennas 106 by applying a phase rotation amount corresponding to the code.

[0050] Next, an example of a code (for example, an orthogonal code) set in the radar device 10 will be described.

[0051] The code generator 104 generates, for example, a different code for each transmitting antenna 106 that performs code-multiplexed transmission.

[0052] For example, in the following description, the number of transmitting antennas 106 that perform code multiplexing transmission is set to "Nt", and the number of code multiplexing is set to "N CM In Figure 5, N CM =Nt.

[0053] The code generation unit 104 generates N sigma-based codes (N sigma-based codes) included in a code sequence (for example, an orthogonal code sequence (also simply called a code or an orthogonal code) that are orthogonal to each other) having a code length (for example, the number of code elements) Loc. allcode (hereinafter, N allcode Of the N orthogonal codes (sometimes referred to as Loc), CM These orthogonal codes are set as codes for code multiplexing transmission.

[0054] For example, the number of code multiplexes NCM is the number of orthogonal codes N allcode The following, N CM ≦N allcode For example, N of the code length Loc CM Code ncm =[OC ncm (1), OC ncm (2), ~, OC ncm (Loc)]. Here, "OC ncm (noc)" is the ncm-th orthogonal code ncm In addition, "ncm" represents the index of the orthogonal code used for code multiplexing, and ncm=1,~, N CM Also, "noc" is the index of the code element, and noc=1,~,Loc.

[0055] As described above, N generated in the code generator 104 CM The orthogonal codes are, for example, codes that are orthogonal to each other (for example, codes that are uncorrelated). For example, a Walsh-Hadamard code may be used for the orthogonal code sequence.

[0056] In the following, as an example, the code number N CM The code length Loc of the orthogonal code sequences is set so as to satisfy the following equation (1).

number

[0057] Here, ceil[x] is an operator (ceil function) that outputs the smallest integer equal to or greater than the real number x. The code generation unit 104 generates, for example, N allcode Of the (Loc) codes, N CM orthogonal codes are used.

[0058] The elements constituting the orthogonal code sequence are not limited to real numbers, but may include complex values.

[0059] The codes may also be other orthogonal codes other than Walsh-Hadamard codes, for example, orthogonal M-sequence codes or pseudo-orthogonal codes.

[0060] Above, each code multiplex number N CM An example of orthogonal codes in the above has been described.

[0061] Next, an example of the amount of phase rotation based on the code for code multiplexing transmission generated in the code generating unit 104 will be described.

[0062] The radar device 10 performs code-multiplexed transmission using different orthogonal codes for the transmitting antennas Tx#1 to Tx#Nt that perform code-multiplexed transmission. Therefore, the code generator 104 generates an orthogonal code Code ncm The phase rotation amount ψ based on ncm (m) is set and output to the phase rotation unit 105. Here, ncm=1, ~, N CM is.

[0063] For example, the phase rotation amount ψ ncm As shown in the following equation (2), (m) is an orthogonal code Code ncm Loc code elements OC ncm (1), ~, OC ncm A phase amount corresponding to (Loc) is given cyclically.

number

[0064] Here, angle(x) is an operator that outputs the radian phase of real number x, and angle(1) = 0, angle(-1) = π, angle(j) = π / 2, and angle(-j) = -π / 2. j is the imaginary unit. Also, OC_INDEX is the orthogonal code sequence Code ncm is an orthogonal code element index indicating an element of, and varies cyclically within the range of 1 to Loc for each transmission period (Tr) as shown in the following equation (3).

number

[0065] Here, mod(x, y) is a modulo operator, which is a function that outputs the remainder after dividing x by y. Also, m=1, ∼, Nc. Nc is a predetermined number of transmission periods (hereinafter referred to as the "radar transmission signal transmission count") that the radar device 10 uses for radar positioning. Also, the radar device 10 transmits the radar transmission signal Nc times, which is, for example, an integer multiple of Loc (for example, Ncode times). For example, Nc=Loc×Ncode.

[0066] Furthermore, the code generator 104 outputs the orthogonal code element index OC_INDEX to the output switch 209 of the radar receiver 200 for each transmission period (Tr).

[0067] The phase rotation unit 105 may be, for example, N tx The phase rotation unit 105 includes a phase shifter or a phase modulator corresponding to each of the transmitting antennas 106. For example, the phase rotation unit 105 rotates the phase ψ input from the code generation unit 104 with respect to the chirp signal input from the radar transmission signal generation unit 101 every transmission period Tr. ncm (m) is assigned to each.

[0068] For example, the phase rotation unit 105 generates an orthogonal code Code ncm The phase rotation amount ψ based on ncm (m) is assigned, where ncm=1,~,N CM and m=1,~,Nc.

[0069] N tx The outputs from the phase rotation units 105 for the transmitting antennas 106 are, for example, amplified to a predetermined transmission power and then tx The signal is radiated into space from transmitting antennas 106 (for example, transmitting array antennas).

[0070] For example, the phase rotation amount ψ ncm (m) is output from the code generator 104 to the phase rotator 105 for each m-th transmission period Tr.

[0071] For example, the first (ncm=1) phase rotation unit 105 (e.g., a phase shifter corresponding to the first transmitting antenna 106 (e.g., Tx#1)) applies phase rotation to the chirp signal generated in the radar transmission signal generation unit 101 for each transmission period Tr, as shown in the following equation (4). The output of the first phase rotation unit 105 is transmitted from the transmitting antenna Tx#1. Here, cp(t) represents the chirp signal for the mth transmission period Tr.

number

[0072] An example of the configuration of the radar transmitter 100 has been described above.

[0073] [Configuration of radar receiver 200] 5, the radar receiver 200 includes Na receiving antennas 202 (e.g., Rx#1 to Rx#Na) forming an array antenna. The radar receiver 200 also includes Na antenna system processors 201-1 to 201-Na, a CFAR (Constant False Alarm Rate) unit 211, a code demultiplexer 212, and a direction estimator 213.

[0074] Each receiving antenna 202 receives a reflected wave signal, which is a radar transmission signal reflected by a target, and outputs the received reflected wave signal to the corresponding antenna system processing unit 201 as a received signal.

[0075] Each antenna system processing unit 201 includes a receiving radio unit 203 and a signal processing unit 206 .

[0076] The radio reception unit 203 includes a mixer unit 204 and an LPF (low pass filter) 205. The mixer unit 204 mixes the received reflected wave signal with a chirp signal, which is a transmission signal input from the radar transmission signal generation unit 101. The LPF 205 performs LPF processing on the output signal of the mixer unit 204, thereby outputting a beat signal with a frequency corresponding to the delay time of the reflected wave signal. For example, as shown in FIG. 6(b), the difference frequency between the frequency of the transmitted chirp signal (transmitted frequency modulated wave) and the frequency of the received chirp signal (received frequency modulated wave) can be obtained as the beat frequency.

[0077] The signal processing unit 206 of each antenna system processing unit 201-z (where z=1 to Na) has an AD conversion unit 207, a beat frequency analysis unit 208, an output switching unit 209, and a Doppler analysis unit 210.

[0078] The signal (for example, a beat signal) output from the LPF 205 is converted into discrete sample data by the AD conversion unit 207 in the signal processing unit 206, which is discretely sampled.

[0079] The beat frequency analysis unit 208 analyzes N data The discrete sample data are subjected to FFT processing. As a result, the signal processing unit 206 outputs a frequency spectrum in which a peak appears at the beat frequency corresponding to the delay time of the reflected wave signal (radar reflected wave). Note that the beat frequency analysis unit 208 may perform FFT processing by multiplying a window function coefficient such as a Han window or a Hamming window. Note that by using the window function coefficient, the radar device 10 can suppress side lobes that appear around the beat frequency peak. In addition, data If the number of discrete sampling data is not a power of two, the beat frequency analysis unit 208 may perform FFT processing as an FFT size of a power of two by including zero-padded data, for example.

[0080] Here, the beat frequency response output from the beat frequency analysis unit 208 in the z-th signal processing unit 206 obtained by transmitting the m-th chirp pulse is called RFT z (f b , m), where f b represents the beat frequency index, which corresponds to the FFT index (bin number). For example, f b =0,~,(N data / 2)-1, z=1,~,Na, m=1,~,N C The beat frequency index f b The smaller the beat frequency, the shorter the delay time of the reflected wave signal (for example, the closer the distance to the target).

[0081] Also, the beat frequency index f b is calculated using the following equation (5): b ) can be converted into the beat frequency index f b Let "distance index f b " is also called.

number

[0082] where B w represents the frequency modulation bandwidth within the range gate of the chirp signal, and C0 represents the speed of light.

[0083] The output switching unit 209 selectively switches the output of the beat frequency analysis unit 208 for each transmission period to the OC_INDEX-th Doppler analysis unit 210 out of the Loc Doppler analysis units 210 based on the orthogonal code element index OC_INDEX output from the code generation unit 104. For example, the output switching unit 209 selects the OC_INDEX-th Doppler analysis unit 210 in the m-th transmission period Tr.

[0084] The signal processing unit 206 has Loc Doppler analysis units 210-1 to 210-Loc. For example, data is input to the noc-th Doppler analysis unit 210 every Loc transmission periods (Loc×Tr) by the output switching unit 209. Therefore, the noc-th Doppler analysis unit 210 receives data (for example, beat frequency response RFT output from the beat frequency analysis unit 208) for Ncode transmission periods out of the Nc transmission periods. z (f b , m)) to obtain the distance index f b Doppler analysis is performed for each, where noc is the index of the code element, noc=1, ~, Loc.

[0085] For example, if Ncode is a power of 2, FFT processing may be applied in Doppler analysis. In this case, the FFT size is Ncode, and the maximum Doppler frequency at which aliasing does not occur, as derived from the sampling theorem, is ±1 / (2Loc×Tr). Also, the Doppler frequency index f s The Doppler frequency interval is 1 / (Ncode×Loc×Tr), and the Doppler frequency index f s The range of f s = -Ncode / 2, ~, 0, ~, Ncode / 2-1.

[0086] For example, the output VFT of the Doppler analysis unit 210 of the z-th signal processing unit 206 z noc (f b , f s ) is expressed by the following equation (6): where j is the imaginary unit and z=1 to Na.

number

[0087] Furthermore, if Ncode is not a power of 2, for example, FFT processing may be performed with a data size (FFT size) that is a power of 2 by including zero-padded data.

[0088] In the following, as an example, a case where Ncode is a power of 2 will be described.

[0089] Furthermore, the Doppler analysis unit 210 may multiply the signal by a window function coefficient such as a Han window or a Hamming window during the FFT process. By applying the window function, the radar device 10 can suppress side lobes that occur around the beat frequency peak.

[0090] The processing in each component of the signal processing unit 206 has been described above.

[0091] In FIG. 5, the CFAR unit 211 performs CFAR processing (for example, adaptive threshold determination) using the outputs of the Loc Doppler analyzers 210 of the first to Na-th signal processors 206, and calculates the distance index f that gives the peak signal. b_cfar and the Doppler frequency index f s_cfar Extract.

[0092] The CFAR unit 211 calculates the output VFT of the Doppler analysis unit 210 of the first to Na-th signal processing units 206 as shown in the following equation (7), for example. z noc (f b , f s ) are power-added, and two-dimensional CFAR processing consisting of a distance axis and a Doppler frequency axis (corresponding to relative velocity) or CFAR processing combining one-dimensional CFAR processing is performed. As for the two-dimensional CFAR processing or the CFAR processing combining one-dimensional CFAR processing, the processing disclosed in Non-Patent Document 3, for example, may be applied.

number

[0093] The CFAR unit 211 adaptively sets a threshold value and calculates a distance index f that has a received power greater than the threshold value. b_cfar , the Doppler frequency index f s_cfar , and received power information PowerFT(f b_cfar , f s_cfar) to the code demultiplexing unit 212.

[0094] Next, an example of the operation of the code demultiplexing unit 212 will be described.

[0095] The code demultiplexing unit 212 demultiplexes, for example, the distance index f extracted in the CFAR unit 211. b_cfar and the Doppler frequency index f s_cfar The code-multiplexed signal is demultiplexed based on the above.

[0096] For example, the code demultiplexing unit 212 calculates the distance index f extracted in the CFAR unit 211 as shown in the following equation (8). b_cfar and the Doppler frequency index f s_cfar The Doppler component VFTALL, which is the output of the Doppler analysis unit 210, corresponds to z (f b_cfar , f s_cfar ) is subjected to code separation processing.

number

[0097] Here, DeMul z ncm (f b_cfar , f s_cfar ) is the distance index f of the Doppler analysis unit 210 in the z-th antenna system processing unit 201. b_cfar and the Doppler frequency index f s_cfar Orthogonal code for the output of Code ncm is the output (e.g., the code separation result) of the code-multiplexed signal obtained by code separation using z=1,~,Na and ncm=1,~,N CM is. Furthermore, in equation (8),

number

number

number

[0098] In equation (8), α(f s_cfar ) represents the "Doppler phase correction vector." The Doppler phase correction vector α(f s_cfar ) is, for example, the Doppler frequency index f extracted in the CFAR unit 211. s_cfar is set to an output range (for example, a Doppler range) of the Doppler analyzer 210 that does not include Doppler aliasing, the Doppler phase rotation caused by the time difference in Doppler analysis between the Loc Doppler analyzers 210 is corrected.

[0099] For example, the Doppler phase correction vector α(f s_cfar ) is expressed as the following equation (10). The Doppler phase correction vector α(f s_cfar ) is, for example, the output VFT of the first Doppler analysis unit 210. z 1 (f b_cfar , f s_cfar ) as a reference for the Doppler analysis time, the output VFT of the second Doppler analysis unit 210 z 2 (f b_cfar , f s_cfar ) to the output VFT of the Loc-th Doppler analyzer 210 z Loc (f b_cfar , f s_cfar The Doppler frequency index f caused by the time delays of Tr, 2Tr, ~, (Loc-1)Tr at each s_cfar is a vector whose elements are Doppler phase correction coefficients that correct the phase rotation in the Doppler component of

number

[0100] Also, in equation (8), VFTALL z (f b_cfar , f s_cfar ) is, for example, the output VFT of the Loc Doppler analyzers 210 in the z-th antenna system processor 201, as shown in the following equation (11): z noc (f b , f s ), the distance index f extracted by the CFAR unit 211 b_cfar and the Doppler frequency index f s_cfar The component VFT corresponding to z noc (f b_cfar , f s_cfar ) (where noc=1,~,Loc) is expressed in vector form.

number

[0101] The above describes an example of the operation of the code demultiplexing unit 212. In the configuration shown in Fig. 5, the maximum Doppler frequency at which aliasing does not occur, which is derived from the sampling theorem, is ±1 / (2Loc × Tr), and the operation of the code demultiplexing unit 212 has been described on the assumption that targets detected by the radar device 10 are within this range.

[0102] The radar device 10 may adopt an arrangement of the transmitting antenna 106 and the receiving antenna 202 that can suppress grating lobes or side lobes and increase angular resolution by, for example, improving the array gain and increasing the aperture length using a virtual receiving antenna.

[0103] An example of the antenna arrangement of the transmitting antenna 106 and the receiving antenna 202, and an example of the direction estimation process in the direction estimation unit 213 when each example of the arrangement is applied will be described below.

[0104] In the following arrangement examples and modifications, the arrangement of the transmitting antenna 106 may be replaced with the arrangement of the receiving antenna 202, and the arrangement of the receiving antenna 202 may be replaced with the arrangement of the transmitting antenna 106. In the radar device 10, even if the antenna arrangements of the transmitting antenna 106 and the receiving antenna 202 are swapped, the same virtual receiving antenna arrangement can be obtained (the numbers of the virtual receiving antennas are changed), and the same effects as those in the following arrangement examples (for example, similar angle measurement performance) can be obtained.

[0105] Furthermore, the horizontal and vertical directions in the following arrangement examples and modifications may be interchanged. When the horizontal and vertical directions are interchanged in the antenna arrangement, the radar device 10 obtains an arrangement in which the horizontal and vertical directions are interchanged as the arrangement of the virtual receiving antennas, and can obtain the effect (for example, angular separation performance) of interchange of the horizontal and vertical directions in the following arrangement examples.

[0106] Furthermore, the horizontal and vertical directions in the layout example do not need to strictly match the horizontal and vertical directions, and the entire layout example may be tilted at a predetermined angle while maintaining the relative positional relationship between the transmitting antennas and receiving antennas included in the layout example. Even in this case, the relative positional relationship between the transmitting antennas and receiving antennas included in the layout example is maintained, and therefore the same effect can be obtained.

[0107] The antenna arrangement (for example, MIMO antenna arrangement) of the radar device 10 may be an arrangement that satisfies the following arrangement conditions, for example.

[0108] [Placement condition A] The virtual receiving antennas are arranged in a diagonal direction ψ. Here, the arrangement in the diagonal direction ψ is an arrangement in the direction of the angle ψ formed with the horizontal direction. The angle ψ formed with the horizontal direction may be set in the range of 30°≦ψ≦60°, for example. The spacing between the virtual receiving antennas arranged in the diagonal direction ψ includes a spacing Dd of 0.5λ.

[0109] For example, the virtual receiving antennas configured by the transmitting and receiving 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 are arranged in an oblique direction (e.g., a third direction) different from both the horizontal direction (e.g., corresponding to a first direction) and the vertical direction (e.g., corresponding to a second direction orthogonal to the first direction) and that satisfy arrangement condition A, in which at least one of the intervals between two adjacent virtual receiving antennas is 0.5λ (e.g., a specified value based on the wavelength of the radar transmission signal). For example, t and receiving antenna spacing D r is D t and D r Absolute value of the difference D d (=|Dt-Dr|) is about 0.5λ (1x the specified value), or D t and D r Absolute value of the difference D d (=|Dt-Dr|) is an integer multiple of 2 or more at intervals of about 0.5λ (an integer multiple of 2 or more of the specified value), and D t and D r If either one of the virtual receiving antennas is spaced apart by approximately 0.5λ (single times the specified value), then at least one of the spaces between two adjacent virtual receiving antennas will be 0.5λ (for example, a specified value based on the wavelength of the radar transmission signal).

[0110] Although the interval Dd is set to 0.5λ here, it may be set to, for example, approximately 0.5λ to 0.8λ. The interval Dd may be set, for example, according to the horizontal or vertical viewing angle of the radar device 10. For example, when the horizontal or vertical viewing angle is a wide viewing angle in the range of approximately ±70 degrees to 90 degrees, the interval Dd may be set to approximately 0.5λ. Alternatively, when the horizontal or vertical viewing angle is a narrow viewing angle in the range of approximately ±20 degrees to 40 degrees, the interval Dd may be set to an interval wider than 0.5λ (for example, approximately 0.7λ). The same applies to the subsequent arrangement examples (or modified examples).

[0111] Here, λ represents the wavelength of the carrier frequency of the radar transmission signal. For example, if a chirp signal is used as the radar transmission signal, λ is the wavelength of the center frequency in the frequency sweep band of the chirp signal.

[0112] By placing the virtual receiving antenna in the diagonal direction ψ according to placement condition A, it is possible to expand the aperture in both the horizontal and vertical directions. Furthermore, placement condition A includes a spacing Dd of about 0.5λ so that no uncertainty occurs when detecting phase fluctuations using the virtual receiving antenna placed in the diagonal direction ψ.

[0113] Since the virtual receiving antenna arranged in the diagonal direction ψ detects phase information that depends on the target arrival angles in both the horizontal and vertical directions, the radar device 10 uses phase information resulting from the target arrival angles in the horizontal and vertical directions when acquiring two-dimensional angle measurement information. Therefore, in addition to arrangement condition A, at least one of arrangement condition B and arrangement condition C, which will be described later, is used in combination.

[0114] [Placement condition B] At least two of the virtual receiving antennas include a virtual antenna arrangement aligned in the horizontal direction, and the distance between them is D H (Hereinafter, this will be referred to as "horizontal spacing") Horizontal spacing D H For example, λ / (2sinψ)≧D H >λ / 2.

[0115] For example, the virtual receiving antennas formed by the transmitting and receiving antennas of the radar device 10 may include a virtual receiving antenna that is arranged horizontally and satisfies arrangement condition B, in which at least one of the distances between two adjacent virtual receiving antennas in the horizontal direction is wider than 0.5λ.

[0116] In addition, D H> λ / (2sinψ), grating lobes may occur in a specific azimuth or elevation angle (azimuth / elevation angle) range. If the radar detection area is a wide-angle range, there is a possibility that the grating lobes may cause false detections. However, if the radar detection area is a relatively narrow area near the front, there is no effect from the grating lobes, and there is no impact on radar detection performance. H >λ / (2 sin ψ).

[0117] [Placement condition C] At least two of the virtual receiving antennas include a virtual antenna arrangement aligned in a vertical direction, and the spacing between them is D V (Hereinafter, this will be referred to as "vertical spacing") Vertical spacing D V For example, λ / (2cosψ)≧D V >λ / 2.

[0118] For example, the virtual receiving antennas formed by the transmitting and receiving antennas of the radar device 10 may include a virtual receiving antenna that is arranged vertically and satisfies arrangement condition C, in which at least one of the distances between two adjacent virtual receiving antennas in the vertical direction is wider than 0.5λ.

[0119] In addition, D V > λ / (2cosψ), grating lobes may occur in a specific azimuth / elevation angle range. If the radar detection area is a wide-angle range, there is a possibility that the grating lobes may cause false detections. However, if the radar detection area is a relatively narrow area near the front, there is no effect of grating lobes, and there is no degradation in radar detection performance. Therefore, D H >λ / (2cosψ).

[0120] The arrangement condition B allows the radar device 10 to detect information on the horizontal arrival angle of the target. The arrangement condition C allows the radar device 10 to detect information on the vertical arrival angle of the target. In addition, in the arrangement conditions B and C, the horizontal interval D H >λ / 2 and vertical spacing D V>λ / 2, the aperture lengths in the horizontal and vertical directions can be expanded. Furthermore, although grating lobes may be present in the horizontal and vertical directions due to placement condition B and placement condition C, the radar device 10 can eliminate the grating lobes by satisfying placement condition A and either placement condition B or placement condition C.

[0121] An example of the above-mentioned arrangement conditions will be described below. An example of a MIMO antenna arrangement that satisfies the above-mentioned arrangement conditions and an example of a direction estimation result by computer simulation for this arrangement example will be described below.

[0122] <Layout example 1> 7A is a diagram showing an example of the arrangement of the transmitting antenna 106 (for example, represented as Tx) and the receiving antenna 202 (for example, represented as Rx) (for example, an example of MIMO antenna arrangement) according to the above-mentioned arrangement conditions. In the example shown in FIG. 7A, the number of transmitting antennas N Tx is two (for example, Tx#1 and Tx#2), and the number of receiving antennas Na is three (for example, Rx#1, Rx#2, and Rx#3).

[0123] In FIG. 7(a), N Tx The two transmitting antennas Tx#1 to Tx#2 are spaced apart at an angle D in the diagonal direction at an angle ψ (ψ=45° in FIG. 7(a)) with respect to the horizontal direction. t are arranged in

[0124] In addition, in FIG. 7(a), at least two of the Na=3 receiving antennas, Rx#1 to #2, are arranged at intervals D in the same diagonal direction ψ as the diagonal direction in which the transmitting antennas Tx#1 to #2 are arranged. r are arranged in

[0125] Here, the distance between the transmitting antennas is D t and receiving antenna spacing D r is D t and D r Absolute value of the difference D d (=|D t -D r |) is spaced at intervals of about 0.5λ (D d7(a), for example, the interval D t =1.5λ, spacing D r By setting =λ, the spacing D of the virtual receiving antenna is set to about 0.5λ (1x the specified value). d and satisfies placement condition A.

[0126] In addition, in FIG. 7A, with respect to the receiving antennas Rx#1 to Rx#2 that are arranged in the same diagonal direction as the transmitting antennas Tx#1 to Tx#2, at least one of the other receiving antennas (Rx#3 in the case of FIG. 7A) is spaced apart horizontally by a distance D from the receiving antenna that is arranged in the diagonal direction ψ. H or vertically spaced apart by D V are arranged in

[0127] For example, in FIG. 7(a), the receiving antenna Rx#3 is spaced horizontally apart from the receiving antenna Rx#2 by a distance D H The distance D in the vertical direction from the receiving antenna Rx#1 is V where the horizontal spacing is D H is λ / (2sinψ)≧D H By setting the vertical spacing D > λ / 2, the placement condition B is satisfied. V is λ / (2cosψ)≧D V By setting the horizontal spacing D > λ / 2, the arrangement condition C is satisfied. H =λ×cosψ(≒0.7λ), vertical spacing D V =λ×sinψ(≈0.7λ), both placement conditions B and C are satisfied.

[0128] In this way, in (a) of FIG. 7, 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 arranged in the diagonal direction ψ (e.g., corresponding to the third direction). Also, in (a) of FIG. 7, the 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 arranged in the diagonal direction ψ, and the distance D between the receiving antennas Rx#1 and Rx#2 isr (for example, distance dr) and distance D between transmitting antennas Tx#1 and Tx#2 t (For example, the absolute value of the difference D d In FIG. 7A, Rx#3 (corresponding to the r3 antenna, for example) and Rx#2 are spaced apart by a distance D in the horizontal direction (corresponding to the second direction, for example). H (D d = 0.5λ) (for example, also represented as a distance dh), and Rx#3 and Rx#1 are arranged at a distance D V (D d = 0.5λ) (for example, also expressed as spacing dv).

[0129] In addition, the number of transmitting antennas is N Tx If the number of receiving antennas Na is three or more, at least two (e.g., Tx#1 and Tx#2) must satisfy the above placement condition. Also, if the number of receiving antennas Na is three or more, at least three (e.g., Rx#1, Rx#2, and Rx#3) must satisfy the above placement condition.

[0130] FIG. 7(b) is a diagram showing an example of the arrangement of virtual receiving antennas obtained by the antenna arrangement shown in FIG. 7(a).

[0131] Here, the arrangement of the virtual receiving antennas may be expressed as in the following equation (12), based on the position of the transmitting antenna 106 (e.g., the position of the feed point or the phase center of each antenna) and the position of the receiving antenna 202 (e.g., the position of the feed point or the phase center of each antenna).

number

[0132] Here, the horizontal and vertical position coordinates of the transmitting antenna 106 (for example, Tx#n) are (X T_#n ,Y T_#n ) (e.g., n=1,~,N Tx ), and the position coordinates of the receiving antenna 202 (for example, Rx#m) are expressed as (X R_#m ,YR_#m ) (for example, m=1,~,Na), and the position coordinates of the virtual receiving antenna VA#k are expressed as (X V_#k ,Y V_#k ) (e.g., k=1,~,N Tx ×Na).

[0133] In equation (12), for example, VA#1 is expressed as the position reference (0,0) of the virtual receiving array.

[0134] In FIG. 7(a), the arrangement of the transmitting antennas Tx#1 and Tx#2 is such that the position coordinates of the transmitting antenna Tx#1 (X T_#1 ,Y T_#1 ) as the reference, the position coordinate of Tx#2 (X T_#2 ,Y T_#2 )=(X T_#1 +D t ×cosψ, Y T_#1 +D t In addition, in FIG. 7(a), the arrangement of the receiving antennas Rx#1 to Rx#3 is such that the position coordinates of the receiving antenna Rx#1 (X R_#1 ,Y R_#1 ) as the standard, (X 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 For example, in (a) and (b) of FIG. 7, when ψ=45°, the horizontal interval D H =λ×cosψ(≒0.7λ), vertical spacing 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 VA#6 can be calculated using equation (12). For example, the position coordinates of the virtual antennas VA#1 to VA#6 are (X V_#1 ,YV_#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).

[0135] As shown in (b) of Fig. 7, VA#1, VA#2, VA#4, and VA#5 are arranged in the diagonal direction ψ, and the distance between two adjacent VA#2 and VA#4 is Dd (=0.5λ). Also, as shown in (b) of Fig. 7, VA#5 and VA#6 (or VA#2 and VA#3) are arranged in the horizontal direction, and the distance between VA#5 and VA#6 (or the distance between VA#2 and VA#3) in the horizontal direction is D d Wider D H As shown in FIG. 7(b), VA#1 and VA#3 (or VA#4 and VA#6) are arranged in the vertical direction, and the distance between VA#1 and VA#3 (or the distance between VA#4 and VA#6) in the vertical direction is D d Wider D V is.

[0136] For example, in (b) of Fig. 7, the virtual receiving antennas include VA#3 and VA#6 (e.g., corresponding to the second virtual receiving antenna group) that are arranged in a direction parallel to the diagonal direction ψ (e.g., corresponding to the fifth direction), unlike VA#1, VA#2, VA#4, and VA#5 (e.g., corresponding to the first virtual receiving antenna group) that are arranged in the diagonal direction ψ and satisfy the arrangement condition A. Also, in (b) of Fig. 7, the vertical distance Dv between one virtual antenna (e.g., VA#1 or VA#5) included in VA#1, VA#2, VA#4, and VA#5 (the first virtual receiving antenna group) and one virtual receiving antenna included in VA#3 and VA#6 (e.g., the second virtual receiving antenna group) is wider than a specified value (e.g., 0.5λ). Also, for example, in (b) of Figure 7, the horizontal distance Dv between one virtual antenna (e.g., VA#2 or VA#5) included in VA#1, VA#2, VA#4 and VA#5 (first virtual receiving antenna group) and one virtual receiving antenna included in VA#3 and VA#6 (e.g., second virtual receiving antenna group) is wider than a specified value (e.g., 0.5λ).

[0137] From the above, the virtual receiving antenna shown in FIG.

[0138] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described arrangement example 1 is applied will be described.

[0139] For example, the direction estimation unit 213 performs code separation processing on the code-multiplexed signal transmitted from the transmission antenna 106 to obtain a received signal DeMul z ncm (f b_cfar ,f s_cfar ), the virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) is generated and direction estimation processing is performed.

[0140] Virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) is the number of transmit antennas N Tx and the number of receiving antennas Na,Tx ×Na elements. The virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) is used to perform a process of estimating the direction of a reflected wave signal from a target based on the phase difference between the receiving antennas 202. Here, z=1, ∼, Na.

[0141] In the MIMO antenna arrangement of arrangement example 1, N Tx = 2, Na = 3, the virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) includes six elements, each of which corresponds to a received signal at VA#1 to VA#6 in the virtual receiving antenna arrangement shown in FIG. 7(b). For example, VA#1 is h(f b_cfar ,f s_cfar ) the first element of the column vector element DeMul1 1 (f b_cfar ,f s_cfar ) Similarly, the second to sixth elements correspond to the received signals VA#2 to VA#6, respectively.

number

[0142] Next, the direction estimation unit 213 calculates the virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) is used to perform horizontal and vertical direction estimation processing as follows.

[0143] The direction estimation unit 213 calculates the virtual array correlation vector h(f b_cfar ,f s_cfar ) is used to calculate the array correction value h_cal, which corrects the phase and amplitude deviations between the transmitting and receiving array antennas. [y] By multiplying by , the virtual receiving array correlation vector h after_cal (f b_cfar ,f s_cfar) and performs horizontal and vertical direction estimation processing based on the phase difference between the receiving antennas of the arriving reflected waves. Here, y=1,~,(N Tx ×Na).

[0144] The CA shown in equation (15) includes an array correction coefficient that corrects the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas, and a coefficient that reduces the influence of inter-element coupling between the antennas (N Tx ×Na) order square matrix. When the coupling between the antennas of the virtual receiving array is negligible, CA becomes a diagonal matrix, and the diagonal elements contain the array correction values ​​h_cal that correct for the phase deviation and amplitude deviation between the transmitting antennas and the receiving antennas. [y] Includes:

[0145] Virtual receiving array correlation vector h corrected for deviations between antennas _after_cal (f b_cfar ,f s_cfar ) is N Tx ×Na elements. Below, we will define each element as h1(f b_cfar ,f s_cfar ), ~, h NTr×Na (f b_cfar ,f s_cfar ) and will be used to explain the direction estimation process.

number

number

[0146] The direction estimation unit 213 calculates the virtual receiving array correlation vector h after_cal (f b_cfar ,f s_cfar ) to estimate the horizontal and vertical directions. In estimating the horizontal and vertical directions, the direction estimator 213 estimates the direction of arrival estimation evaluation function value P(θ, φ, f b_cfar ,f s_cfarThe azimuth direction θ and elevation direction φ in the target are varied within a predetermined angle range to calculate a spatial profile, a predetermined number of maximum peak directions are extracted in descending order, and the azimuth direction and elevation direction of each maximum peak are output as estimated directions of arrival. Here, θ and φ represent the azimuth angle and elevation angle relative to the target. For example, when the antenna is arranged on the XZ plane (e.g., the X axis is the horizontal direction and the Z axis is the vertical direction), the radar axis in the front direction of the radar (the direction perpendicular to the XZ plane) is the Y axis, and the direction cosines of the X, Y, and Z axes relative to the target can be expressed as sinθcosφ, cosθcosφ, and sinφ, respectively.

[0147] The direction of arrival estimation evaluation function value P(θ, φ, f b_cfar ,f s_cfar ) can be calculated using various 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 beamformer method can be expressed as in the following equation (16). Here, the superscript H is the Hermitian transpose operator. Other methods such as Capon and MUSIC can also be applied.

number

[0148] where θ u is a value obtained by varying the azimuth range for estimating the direction of arrival at a predetermined azimuth interval β1. For example, θ u may be set as follows: θ u =θmin+uβ1. u=0,~,NU. NU=floor[(θmax-θmin) / β1]. Here, floor(x) is a function that returns the largest integer value that does not exceed the real number x.

[0149] Also, φ v is a value obtained by varying the elevation angle range for estimating the direction of arrival at a predetermined elevation angle interval β2. For example, Φ v may be set as follows: φ v =φmin+vβ2. v=0,~,NV. NV=floor[(φmax-φmin) / β2].

[0150] Here, the direction vector α(θ u , φ v ) is a complex response of a virtual receiving antenna when radar reflections arrive from the azimuth direction θ and the elevation direction φ (N Tx ×Na) order column vector. The complex response of the virtual receiving antenna, α(θ u , φ v ) represents the phase difference calculated geometrically from the element spacing between the antennas. Note that the direction perpendicular to the front of the antenna plane shown in Arrangement Example 1 is used as the reference (azimuth θ = 0°, elevation angle φ = 0°).

[0151] <Example of direction estimation result for layout example 1> Next, an example of a direction estimation result (a computer simulation result) when the antenna arrangement according to the above-described Arrangement Example 1 is applied will be described.

[0152] Figures 8(a) and 8(b) show examples of angle measurement results using the beamformer method when receiving target reflection waves from a horizontal 0° and vertical 40° direction in the MIMO radar antenna arrangement shown in Figure 7(a). The direction estimation results shown in Figures 8(a) and 8(b) plot the output of the direction-of-arrival estimation evaluation function value in a horizontal ±90° range and a vertical ±90° range. In Figure 8(a), the horizontal axis represents the horizontal angle and the vertical angle, and the vertical axis represents the normalized power value in these two-dimensional directions in a three-dimensional manner. Figure 8(b) is a top view of Figure 8(a), showing an example of a heat map display of normalized power values ​​in two-dimensional directions with the horizontal axis as the horizontal direction and the vertical axis as the vertical direction, with the power values ​​shown in grayscale.

[0153] 8(a) and 8(b) show that the main beam is oriented in the horizontal 0° and vertical 40° directions, and that no grating lobes are generated. Furthermore, in the case of the MIMO radar antenna arrangement shown in FIG. 7(a), the horizontal beam width is approximately 23° and the vertical beam width is approximately 24° (in the case of a Fourier beam pattern oriented in the horizontal 0° and vertical 0° directions). Therefore, with the antenna arrangement in FIG. 7(a), compared to the antenna arrangement in FIG. 1, the 3-dB beam width in the horizontal direction is reduced by 6.2% (= 23 / 37) and the 3-dB beam width in the vertical direction is reduced by 4.1% (= 24 / 59), which is expected to improve the accuracy of two-dimensional angle measurement in the horizontal and vertical directions (for example, an improvement in accuracy of approximately 1.6 to 2.5 times).

[0154] An example of the direction estimation result (computer simulation result) in Arrangement Example 1 and the effects of Arrangement Example 1 have been described above.

[0155] In FIG. 5, the direction estimation unit 213 outputs, for example, the direction estimation result, and further outputs a distance index f b_cfar (e.g., information converted based on Equation (5)), the Doppler frequency index f b_cfar may output target Doppler velocity information based on

[0156] Doppler frequency index f s_cfar The relative velocity component v d (f s_cfar ), the following equation (17) may be used. Here, λ is the wavelength of the carrier frequency of the RF signal output from the transmitting radio unit (not shown). f is the Doppler frequency interval in the FFT processing in the Doppler analysis unit 210. For example, in this embodiment, Δ f =1 / {Loc×N code ×T r}.

number

[0157] As described above, in Arrangement Example 1, by satisfying Arrangement Condition A and either Arrangement Condition B or Arrangement Condition C in the MIMO antenna arrangement, it is possible to obtain two-dimensional arrival angle information of a target with grating lobes suppressed (or removed). Furthermore, in Arrangement Example 1, by arranging the MIMO antennas so as to expand the virtual antenna in the diagonal direction ψ, it is possible to expand the aperture surfaces in the vertical and horizontal directions, thereby improving the two-dimensional angle measurement accuracy in the horizontal and vertical directions. As a result, even under conditions where the number of antennas is a predetermined number, it is possible to arrange the antennas in a way that can suppress grating lobes while widening the element spacing in at least one of the vertical and horizontal directions, thereby improving the angle measurement accuracy (or resolution) in the horizontal and vertical directions of the radar device 10.

[0158] Furthermore, in the MIMO antenna arrangement of arrangement example 1, in addition to the virtual receiving antennas (VA#1, #2, #4, and #5 in FIG. 7(b)) arranged in the diagonal direction ψ that satisfy arrangement condition A, virtual receiving antennas (VA#3 and VA#6 in FIG. 7(b)) arranged in the diagonal direction ψ at positions different from the arrangement positions of these virtual receiving antennas are also included. This makes it possible to apply a simplified method of two-dimensional angle measurement in the direction estimation unit 213 (hereinafter referred to as the "simplified two-dimensional angle measurement method"), and it is possible to significantly reduce the amount of two-dimensional angle measurement processing compared to the above-mentioned two-dimensional Fourier beamformer angle measurement method. An example of the simplified two-dimensional angle measurement method will be described later.

[0159] It should be noted that the antenna arrangement of Arrangement Example 1 is not limited to the antenna arrangement shown in (a) of FIG. 7. For example, in Arrangement Example 1, an antenna may be further added to at least one of the transmitting antenna 106 and the receiving antenna 202 with respect to the antenna arrangement shown in (a) of FIG. 7. When the transmitting antenna 106 or the receiving antenna 202 is increased, for example, a relationship is established in which a virtual receiving antenna is additively added at the position shown in Equation (12). For example, an arrangement in which another virtual receiving antenna is further added to the virtual receiving antenna arrangement shown in (b) of FIG. 7 is achieved. Even in the case of such an antenna arrangement including Arrangement Example 1, the effects described in Arrangement Example 1 above are maintained, and the same effects as those of Arrangement Example 1 can be obtained.

[0160] Furthermore, for example, by adding an antenna to the antenna configuration of Arrangement Example 1, in addition to the effects described in Arrangement Example 1 above, the level of grating lobes or side lobes to be suppressed can be further reduced, thereby reducing erroneous detections during angle measurement in the radar device 10 and improving angle measurement performance. Note that the addition of an antenna can be similarly applied to the subsequent arrangement examples or modified examples, and similar effects can be obtained.

[0161] Below, an example will be described in which at least one of the transmitting antenna 106 and the receiving antenna 202 is further added to the antenna arrangement of Arrangement Example 1 (for example, (a) of FIG. 7). Note that the addition of an antenna can be similarly applied to the following arrangement examples or modifications, and similar effects can be obtained.

[0162] 9A shows an example of an arrangement in which a transmitting antenna Tx#3 is further added to the antenna arrangement shown in FIG. 7A. In FIG. 9A, Tx#3 is spaced apart from Tx#2 in the diagonal direction ψ by a distance D t2 9(b) is an example of an arrangement in which a receiving antenna Rx#4 is further added to the antenna arrangement shown in FIG. 7(a). In FIG. 9(b), Rx#4 is spaced apart from Rx#2 in the diagonal direction ψ by a distance D r2 are arranged in

[0163] The antenna arrangements in FIGS. 9(a) and 9(b) increase the number of virtual receiving antennas (not shown) arranged in the diagonal direction ψ that satisfy arrangement condition A, and further expand the apertures in both the horizontal and vertical directions, thereby improving the angle measurement performance in both the horizontal and vertical directions.

[0164] In FIG. 9(a), the interval D between Tx#3 and Tx#2 t2 is the distance D between Tx#1 and Tx#2 t However, the case where the interval D t2 is the interval D tSimilarly, in FIG. 9(b), the distance D between Rx#4 and Rx#2 is r2 is the distance D between Rx#1 and Rx#2 r However, the case where the interval D r2 is the interval D r A similar effect can be obtained with a different interval.

[0165] 9(c) is an example of an arrangement in which a receiving antenna Rx#4 is further added to the antenna arrangement shown in FIG. 7(a). In FIG. 9(c), Rx#4 is arranged in a line in the horizontal direction relative to Rx#3 at an interval D H2 For example, the spacing D H2 9(c), the number of virtual receiving antennas arranged in the horizontal direction that satisfy arrangement condition B can be increased, and the aperture in the horizontal direction can be further enlarged, thereby improving the angle measurement performance in the horizontal direction.

[0166] In FIG. 9(c), the distance D between Rx#4 and Rx#3 H2 is the distance D between Rx#2 and Rx#3 H Although the case of a different interval is shown, it is not limited to this, and the interval D H2 is the interval D H The same effect can be obtained with the same interval as H2 and spacing D H By setting the intervals and the intervals to be relatively prime, the intervals at which grating lobes occur can be made different, the grating lobe suppression effect can be improved, and a more preferable arrangement can be achieved.

[0167] 9(c) is an antenna arrangement in which a receiving antenna 202 (Rx#4) is added to the antenna arrangement in FIG. 7(a), but is not limited to this. For example, a transmitting antenna 106 may be added. For example, a transmitting antenna Tx#3 (not shown) may be arranged at an interval D so as to be aligned horizontally with respect to the transmitting antenna Tx#1 or Tx#2. H2 The same effect can be achieved with the placement added in

[0168] 9(d) is an example of an arrangement in which a receiving antenna Rx#4 is further added to the antenna arrangement shown in FIG. 7(a). In FIG. 9(d), Rx#4 is arranged in a line in the vertical direction relative to Rx#3 at an interval D V2 For example, the spacing D V2 9(d), the number of virtual receiving antennas arranged in the vertical direction that satisfy arrangement condition C can be increased, and the aperture in the vertical direction can be further enlarged, thereby improving the angle measurement performance in the vertical direction.

[0169] In FIG. 9(d), the distance D between Rx#4 and Rx#3 V2 is the distance D between Rx#1 and Rx#3 V Although the case of a different interval is shown, it is not limited to this, and the interval D V2 is the interval D V The same effect can be obtained with the same interval as V2 and spacing D V By setting the intervals and the intervals to be relatively prime, the intervals at which grating lobes occur can be made different, the grating lobe suppression effect can be improved, and a more preferable arrangement can be achieved.

[0170] 9(d) is an antenna arrangement in which a receiving antenna 202 (Rx#4) is added to the antenna arrangement in FIG. 7(a), but is not limited to this. For example, a transmitting antenna 106 may be added. For example, a transmitting antenna Tx#3 (not shown) may be arranged vertically in a line with respect to the transmitting antennas Tx#1 or Tx#2 at an interval D V2 The same effect can be achieved with the placement added in

[0171] 9(e) is an example of an arrangement in which a receiving antenna Rx#4 is further added to the antenna arrangement shown in FIG. 7(a). In FIG. 9(e), Rx#4 is arranged in a line in the diagonal direction ψ with respect to another receiving antenna Rx#3 different from Rx#1 and Rx#2 that constitute the virtual receiving antennas that satisfy the arrangement condition A, at an interval D. s For example, the spacing D s9(e), the number of virtual receiving antennas arranged in the diagonal direction ψ can be increased, and the apertures in both the horizontal and vertical directions can be further enlarged, thereby improving the angle measurement performance in both the horizontal and vertical directions.

[0172] In FIG. 9(e), the distance D between Rx#3 and Rx#4 s is the distance D between Tx#1 and Tx#2 t The case of a different interval from, but not limited to, the interval D s is the interval D t The same effect can be obtained with the same spacing as s and spacing D t By setting the intervals and the intervals to be relatively prime, the intervals at which grating lobes occur can be made different, the grating lobe suppression effect can be improved, and a more preferable arrangement can be achieved.

[0173] 9(e) is an antenna arrangement in which a receiving antenna 202 (Rx#4) is added to the antenna arrangement shown in FIG. 7(a), but is not limited to this. For example, the receiving antennas 202 and 202 are arranged in a line in the diagonal direction ψ with a spacing D from the transmitting antennas 106 other than the transmitting antennas constituting the virtual receiving antenna that satisfies the arrangement condition A. s The same effect can be obtained with an arrangement in which a transmitting antenna is added at D d is 1 times the specified value.

[0174] In order to extend the detection distance of the radar device 10, it is effective to use an antenna with high gain. For example, narrowing the antenna's directivity (beam width) can improve the antenna gain. The wider the antenna's aperture, the narrower the antenna's directivity becomes. Therefore, the narrower the antenna's directivity, the larger the antenna size tends to be. For example, in a radar device mounted on a vehicle (also called an on-board radar), a sub-array antenna configured by arranging multiple antenna elements in the vertical direction may be used to narrow the vertical directivity. Narrowing the vertical directivity using a sub-array antenna can improve the antenna gain in the vertical direction and reduce reflected waves 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 straight-ahead direction, a direction perpendicular to the vehicle's straight-ahead direction, or a direction perpendicular to the vehicle's height direction.

[0175] Figure 10(a) shows an example of a subarray in which four planar patch antenna elements are arranged in the vertical direction (longitudinal direction in Figure 10(a)) and one element is arranged in the horizontal direction (horizontal direction in Figure 10(a)). Figure 10(b) shows an example of a subarray in which one planar patch antenna element is arranged in the vertical direction (longitudinal direction in Figure 10(b)) and four elements in the horizontal direction (horizontal direction in Figure 10(b)). Figure 10(c) shows an example of a subarray in which four planar patch antenna elements are arranged in the vertical direction (longitudinal direction in Figure 10(c)) and two elements in the horizontal direction (horizontal direction in Figure 10(c)).

[0176] In Figure 10, H ANT indicates the antenna size in the vertical direction, and W ANT indicates the antenna size in the horizontal direction. Note that the configuration of the subarray is not limited to the configuration shown in Fig. 10, and for example, the number of elements in each of the vertical and horizontal directions may differ from the number shown in Fig. 10.

[0177] When such a subarray antenna is used as a single antenna for the transmitting antenna 106 or the receiving antenna 202, it is difficult to arrange the antennas at intervals narrower than the size of the subarray antenna.

[0178] For example, when arranging the subarray antennas shown in Fig. 10(a), the size of the subarray antennas can be one wavelength or more in the vertical direction, so an antenna arrangement in which the antenna spacing in the vertical direction is wider by one wavelength or more can be applied. For example, in Fig. 11, Fig. 14, Fig. 16, and Fig. 17 described below, the transmitting antennas 106 do not overlap in the vertical direction, and the receiving antennas 202 do not overlap in the vertical direction, so it is possible to arrange subarray antennas with a large vertical size as shown in Fig. 10(a).

[0179] For example, when arranging the subarray antennas shown in Fig. 10(b), the size of the subarray antennas can be one wavelength or more in the horizontal direction, so an antenna arrangement in which the antenna spacing in the horizontal direction is one wavelength or more wider can be applied. For example, the transmitting antennas in the antenna arrangements described below, or the receiving antennas shown in Figs. 13, 17, and 19 described below, are arranged so that the transmitting antennas 106 do not overlap in the horizontal direction and the receiving antennas 202 do not overlap in the horizontal direction, so it is possible to arrange subarray antennas with a large horizontal size as shown in Fig. 10(b).

[0180] For example, when arranging the subarray antenna shown in FIG. 10(c), the size of the subarray antenna can be one wavelength or more in both the horizontal and vertical directions. Therefore, an antenna arrangement in which the antenna spacing in the horizontal and vertical directions is wider by one wavelength or more can be applied. For example, since the transmitting antennas in each antenna arrangement described below can be arranged with wide spacing in the horizontal and vertical directions, it is possible to arrange a subarray antenna with a large size in both the horizontal and vertical directions as shown in FIG. 10(c).

[0181] As described above, when the sub-array antenna is used as the transmitting antenna 106 or the receiving antenna 202, in addition to the above-mentioned effects, the effect of improving the directional gain of the antenna can be obtained.

[0182] [Modification of Arrangement Example 1] The same effect can be obtained by modifying Arrangement Example 1 as follows: Modifications of Arrangement Example 1 will be described below.

[0183] 11(a) is a diagram showing a modified example of the MIMO antenna arrangement of the transmitting antennas 106 and the receiving antennas 202 according to arrangement condition 1. In the example shown in FIG. 11(a), the number of transmitting antennas N Tx is two (for example, Tx#1 and Tx#2), and the number of receiving antennas Na is three (for example, Rx#1, Rx#2, and Rx#3).

[0184] Figure 11(b) is a diagram showing an example of the arrangement of virtual receiving antennas obtained by the antenna arrangement shown in Figure 11(a). The arrangement of each virtual receiving antenna is calculated by applying equation (12) based on the antenna arrangement shown in Figure 11(a).

[0185] In FIG. 11(a), N Tx The two transmitting antennas Tx#1 to Tx#2 are spaced apart by a distance D in the diagonal direction at an angle ψ (ψ=45° in the example of FIG. 11) with respect to the horizontal direction. t Furthermore, at least two of the Na=3 receiving antennas 202, namely, receiving antennas Rx#1 and Rx#2, are arranged at intervals D in the same diagonal direction ψ as the direction in which the transmitting antennas Tx#1 and Tx#2 are arranged. r are arranged in

[0186] Here, the distance between the transmitting antennas is D t and receiving antenna spacing D r is D t and D r Absolute value of the difference D d (=|D t -D r In FIG. 11, for example, the interval D t =2λ, spacing D r = 1.5λ, the virtual receiving antenna arrangement has a spacing D of about 0.5λd and satisfies placement condition A.

[0187] In addition, in FIG. 11(a), the receiving antenna Rx#3 is spaced apart from the receiving antenna Rx#2 in the horizontal direction by a distance D H The receiving antenna Rx#3 is placed at a position in a fourth direction different from the horizontal, vertical and diagonal directions from the receiving antenna Rx#1. The receiving antenna Rx#3 is placed at a distance D in the horizontal direction from the diagonal direction ψ. H and at a vertical distance of D V where the horizontal spacing is D H =λ / (2 sinψ)≈0.7λ, thereby satisfying placement condition B. In FIG. 11(a), the receiving antenna Rx#3 is spaced apart from the receiving antenna Rx#1 or Rx#2 by a distance D in the vertical direction. V Since they are not arranged in a line, placement condition C is not met.

[0188] Also, for example, in (b) of Figure 11, the difference between the aperture length of VA#1, VA#2, VA#4 and VA#5 (e.g., the first virtual receiving antenna group) and the aperture length of VA#3 and VA#6 (e.g., the second virtual receiving antenna group) (e.g., the difference between VA3 to VA6 and VA1 to VA5) may be set equal to a predetermined multiple of a specified value (e.g., 0.5λ).

[0189] In addition, the number of transmitting antennas is N Tx If there are three or more receiving antennas Na, it is sufficient that at least two of them (for example, Tx#1 and Tx#2) satisfy the above-mentioned placement condition. Also, if there are three or more receiving antennas Na, it is sufficient that at least three of them (for example, Rx#1, Rx#2, and Rx#3) satisfy the above-mentioned placement condition.

[0190] An example of direction estimation processing in the direction estimation unit 213 when the above-described antenna arrangement is applied will be described. For example, the direction estimation unit 213 performs code separation processing on the code-multiplexed signal transmitted from the transmission antenna 106 to obtain a received signal DeMul z ncm (f b_cfar ,f s_cfar), the virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) is generated and direction estimation processing is performed. The operation of the direction estimation processing unit is the same as the operation when Arrangement Example 1 is used, and the description thereof will be omitted.

[0191] <Example of direction estimation result for a variation of Arrangement Example 1> Next, an example of a direction estimation result (computer simulation result) when an antenna arrangement according to a modification of the above-described Arrangement Example 1 is applied will be described.

[0192] Figures 12(a) and (b) show examples of angle measurement results using the beamformer method when target reflected waves are received from a horizontal direction of 0° and a vertical direction of 40° in the MIMO radar antenna arrangement shown in Figure 11(a). Figures 12(a) and (b) show the angle measurement results for arrangement example 1 (e.g., Figures 8(a) and (b)) under the same target conditions, and are plotted using the same graphs.

[0193] 12(a) and 12(b) show that the main beam is oriented in the horizontal 0° and vertical 40° directions, and that no grating lobes are generated. Furthermore, in the case of the MIMO radar antenna arrangement shown in FIG. 11(a), the horizontal beam width is approximately 17° and the vertical beam width is approximately 18° (in the case of a Fourier beam pattern oriented in the horizontal 0° and vertical 0° directions). Therefore, with the antenna arrangement in FIG. 11(a), compared to the antenna arrangement in FIG. 1, the 3-dB beam width in the horizontal direction is reduced by 4.6% (= 17 / 37) and the 3-dB beam width in the vertical direction is reduced by 3.1% (= 18 / 59), which is expected to improve the accuracy of two-dimensional angle measurement in the horizontal and vertical directions (for example, an improvement in accuracy of approximately 2.2 to 3.3 times).

[0194] In this way, in the antenna arrangement according to the modified example of Arrangement Example 1, by satisfying Arrangement Condition A and Arrangement Condition B, the same effect as in Arrangement Example 1 can be obtained.

[0195] 11 has been described in connection with the case where placement conditions A and B are satisfied, but the present invention is not limited to this, and it is sufficient if at least one of placement conditions B and C is satisfied in addition to placement condition A. FIG. 13(a) is an example of an antenna placement that satisfies placement conditions A and C. For example, as shown in FIG. 13(a), Rx#2 (e.g., corresponding to the r2 antenna) and Rx#3 (e.g., corresponding to the r3 antenna) are placed in a direction different from the vertical direction, horizontal direction, and diagonal direction ψ (e.g., corresponding to the fourth direction). Rx#1 (e.g., corresponding to the r1 antenna) and Rx#3 (e.g., corresponding to the r3 antenna) are placed in the vertical direction (e.g., corresponding to the second direction). Receiving antenna Rx#3 is spaced apart horizontally from the diagonal direction ψ by a distance D. H and at a vertical distance of D V 13(b) is a diagram showing an example of the arrangement of virtual receiving antennas obtained by the antenna arrangement shown in FIG. 13(a). For example, in FIG. 13(b), the difference between the aperture length of VA#1, VA#2, VA#4, and VA#5 (e.g., first virtual receiving antenna group) and the aperture length of VA#3 and VA#6 (e.g., second virtual receiving antenna group) (e.g., the difference between VA3 to VA6 and VA1 to VA5) may be set equal to a predetermined multiple of a specified value (e.g., 0.5λ). The antenna arrangement shown in FIG. 13 also provides the same effect as Arrangement Example 1, and can suppress grating lobes.

[0196] [Example of simplified 2D angle measurement method in action] An example of operation when the simplified two-dimensional angle measurement method is applied in direction estimation section 213 will be described below.

[0197] (1) The direction estimation unit 213 performs one-dimensional FFT processing using the received signals of the virtual receiving antennas arranged in the diagonal direction ψ that satisfies the arrangement condition A, and obtains the spatial spectrum H A Calculate (m) where m=1,~,N FFT indicates N FFT indicates the FFT size.

[0198] Then, the direction estimation unit 213 calculates the spatial spectrum HA FFT index m that is the peak on (m) peakA where m peakA is H A For example, the virtual receiving antennas VA#1, VA#2, VA#4, and VA#5 shown in FIG. 7B satisfy the placement condition A, and the distance between VA#2 and VA#4 is D. d (for example, 0.5λ). The direction estimation unit 213 d is set as the spatial sampling interval, and the received signals of the virtual receiving antennas arranged in the diagonal direction ψ that satisfies the arrangement condition A are subjected to one-dimensional FFT processing.

[0199] In addition, the interval D d If there is no virtual receiving antenna, the direction estimator 213 may perform FFT processing after padding with zeros. For example, in FIG. 7B, the received signals h of the virtual receiving antennas VA#1, VA#2, VA#4, and VA#5 in the diagonal arrangement that satisfies the arrangement condition A are VA#1, h VA#2, h VA#4, h VA#5 Based on this, the received vector h A The received signal h VA#n is the virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) element.

number

[0200] The direction estimation unit 213 may, for example, set the FFT size to a predetermined power-of-two size N FFT The received vector h is zero-padded until Azeropad In this case, the spatial spectrum H A (m) is expressed by the following equation (19): where m represents the FFT index. m=-N FFT / 2~N FFT / 2+1, where h AZeroPad,n is the received vector h AZeropad represents the nth element of .

number

[0201] The direction estimation unit 213 calculates the spatial spectrum H A FFT index m that is the peak on (m) peakA Phase change in FFTpeakPhase(m PeakA ) is calculated, where the spatial spectrum H A FFT index m that is the peak on (m) peakA Phase change in FFTpeakPhase(m PeakA ) is the spatial sampling interval D d It represents the phase change for each wave and depends on the azimuth and elevation angles at which the target reflected wave arrives. For example, when the FFT processing expressed by the above equation (19) is performed, FFTpeakPhase(m PeakA ) is expressed as the following equation (20):

number

[0202] In this way, the direction estimation unit 213 uses the received signal of a virtual receiving antenna (for example, a virtual receiving antenna arranged in the diagonal direction ψ) among the multiple virtual receiving antennas that satisfies the arrangement condition A to estimate the distance D d The phase change for each interval is calculated.

[0203] (2) The direction estimation unit 213 calculates the horizontal phase difference diffPhase using the received signals of at least two of the virtual receiving antennas arranged in the horizontal direction that satisfy the arrangement condition B. H For example, in the virtual receiving antenna of FIG. 7B, the virtual receiving antennas arranged in the horizontal direction that satisfy the arrangement condition B are VA#5 and VA#6, and the horizontal phase difference diffPhase H (θ0) is calculated. Here, arg[x] is an operator that represents the argument of the complex number x. Also, the superscript * (asterisk) is an operator that represents the complex conjugate.

number

[0204] In addition, an integer N that satisfies the phase difference conditions shown in the above equation (21) and the following equation (22) ambiguityH For example, in equation (22), N ambiguityH = 0, it corresponds to equation (21). This allows calculation of phase difference candidates in the horizontal direction, including the true value direction and the grating lobe direction.

number

[0205] In FIG. 7B, in addition to VA#5 and VA#6, the combination of virtual receiving antennas arranged in the horizontal direction that satisfies arrangement condition B also includes VA#2 and VA#3. The direction estimator 213 calculates the horizontal phase difference diffPhase H Alternatively, multiple phase differences diffPhase H The average of these may also be used.

[0206] (3) The direction estimation unit 213 calculates the phase difference diffPhase in the vertical direction using the received signals of at least two of the virtual receiving antennas arranged in the vertical direction that satisfy the arrangement condition C. V For example, in the virtual receiving antenna of FIG. 7B, the virtual receiving antennas arranged in the vertical direction that satisfy the arrangement condition C are VA#1 and VA#3, and the phase difference diffPhase V (φ0) is calculated.

number

[0207] In addition, an integer N that satisfies the phase difference conditions shown in the above equation (23) and the following equation (24) ambiguityV For example, in equation (24), NambiguityV = 0, it corresponds to equation (23). This allows calculation of phase difference candidates in the vertical direction, including the true value direction and the grating lobe direction.

number

[0208] In FIG. 7B, in addition to VA#1 and VA#3, there are also VA#4 and VA#6 as combinations of virtual receiving antennas arranged in the vertical direction that satisfy arrangement condition C. The direction estimator 213 calculates the phase difference diffPhase V (φ) may be calculated, or multiple phase differences diffPhase V The average of these may also be used.

[0209] Furthermore, if there is no vertically arranged virtual receiving antenna that satisfies the placement condition C, the radar device 10 may apply interpolation processing to a virtual receiving antenna that is arranged in the diagonal direction ψ, excluding a virtual receiving antenna that satisfies the placement condition A, to find the received signal of the vertically arranged virtual receiving antenna that satisfies the placement condition C.

[0210] 11(b) is an example of an arrangement in which there is no vertically arranged virtual receiving antenna that satisfies the arrangement condition C. In this case, for example, the direction estimation unit 213 may use interpolation processing to find the received signal of the vertically arranged virtual receiving antenna (position of point P in FIG. 11(b); hereinafter referred to as "VA#P") that satisfies the arrangement condition C for VA#1.

[0211] For example, if at least two virtual receiving antennas are not arranged in either the vertical or horizontal direction (the vertical direction in Figure 11), the direction estimation unit 213 may calculate the phase difference in either direction (the vertical direction in Figure 11) by interpolation processing using the received signal of one of the virtual receiving antennas in the second virtual receiving antenna group (VA#3 and VA#6 in (b) of Figure 11).

[0212] For example, in FIG. 11(b), VA#3 and point P are located on the diagonal direction ψ, and VA#3 and point P are separated by a distance D d Therefore, as shown in the following equation (25), the received signal h VA#P is the received signal h of VA#3 VA#3 The spatial sampling interval D of the target arrival wave calculated based on the virtual receiving antenna that satisfies the arrangement condition A for d Phase change FFTpeakPhase(m PeakA ) can be calculated by interpolation processing.

number

[0213] Alternatively, for example, in FIG. 11(b), VA#6 and point P are located on the diagonal direction ψ, and VA#6 and point P are spaced apart by a distance of 5D. d Therefore, as shown in the following equation (26), the received signal h VA#P is the received signal h of VA#6 VA#6 For FFTpeakPhase(m PeakA ) can be calculated by interpolation processing.

number

[0214] Alternatively, the direction estimation unit 213 may further add and output signals that have been interpolated for the received signals of multiple virtual receiving antennas (e.g., VA#3 and VA#6 in (b) of FIG. 11) located in the diagonal direction ψ, as shown in the following equation (27). In this case, the SNR (signal-to-noise power ratio) of the received signal is improved by the averaging process, and the accuracy of the interpolation can be improved.

number

[0215] Although the case where there is no vertically arranged virtual receiving antenna that satisfies placement condition C has been described, if there is no horizontally arranged virtual receiving antenna that satisfies placement condition B, the received signal of the vertically arranged virtual receiving antenna that satisfies placement condition B may be calculated by applying interpolation processing using virtual receiving antennas that are arranged in the diagonal direction ψ, excluding the virtual receiving antenna that satisfies placement condition A. Furthermore, if there is no virtual receiving antenna that satisfies placement condition B or placement condition C, similar interpolation processing can be applied to the placement examples and modified examples described below.

[0216] (4) The direction estimation unit 213 calculates the horizontal phase difference diffPhase calculated based on the virtual receiving antenna that satisfies the placement condition B. H (θ NambiguityH ), and the vertical phase difference diffPhase calculated based on the virtual receiving antenna that satisfies the placement condition C. V (φ NambiguityV ) among the combinations, the spatial sampling interval D of the target arrival wave calculated based on the virtual receiving antenna that satisfies the arrangement condition A d Phase change FFTpeakPhase(m PeakA ), the horizontal and vertical angles of arrival are extracted based on corresponding (e.g., matching) combinations.

[0217] For example, the horizontal phase difference diffPhase calculated based on the virtual receiving antenna that satisfies the placement condition B H (θ NambiguityH ) and the vertical phase difference diffPhase calculated based on the virtual receiving antenna that satisfies the placement condition C. V (φ NambiguityV ) spatial sampling interval D d The phase change for each phase is expressed as HVPhase(θ N_ambiguityH , φ N_ambiguityV ) The direction estimation unit 213 is expressed by, for example, FFTpeakPhase(m PeakA ) and HVPhase(θ N_ambiguityH , φ N_ambiguityV ) and the absolute value of the difference between the horizontal phase difference diffPhase H (θNambiguityH ) and vertical phase difference diffPhase V (φ NambiguityV ) may be used as an estimated value of the target direction.

number

[0218] The operation of the simplified two-dimensional angle measurement method in direction estimation section 213 has been described above.

[0219] Arrangement example 1 and the modified example of arrangement example 1 have been described above.

[0220] <Layout example 2> 14(a) is a diagram showing an example of the arrangement of MIMO antennas, ie, the transmitting antennas 106 and the receiving antennas 202, according to the above-mentioned arrangement conditions. In the example shown in FIG. 14(a), the number of transmitting antennas N Tx is two (for example, Tx#1 and Tx#2), and the number of receiving antennas Na is three (for example, Rx#1, Rx#2, and Rx#3).

[0221] Figure 14(b) is a diagram showing an example of the arrangement of virtual receiving antennas obtained by the antenna arrangement shown in Figure 14(a). The arrangement of each virtual receiving antenna is calculated by applying equation (12) based on the antenna arrangement shown in Figure 14(a).

[0222] In FIG. 14(a), N Tx The two transmitting antennas Tx#1 to Tx#2 are spaced apart at an angle D in the diagonal direction at an angle ψ (ψ=45° in FIG. 14(a)) with respect to the horizontal direction. t The diagonal direction is not limited to ψ=45°, and may be set to, for example, about ψ=30° to 60°.

[0223] In addition, in FIG. 14(a), at least two of the Na=3 receiving antennas, Rx#1 to #2, are arranged at intervals D in the same diagonal direction ψ as the diagonal direction in which the transmitting antennas Tx#1 to #2 are arranged. r are arranged in

[0224] Here, the distance between the transmitting antennas is D t is set to four times the spacing of about 0.5λ, and the receiving antenna spacing D r Therefore, the distance between the transmitting antennas D t and receiving antenna spacing D r is D t and D r Absolute value of the difference D d (=|Dt-Dr|) is an integer multiple (3 times) of the spacing of about 0.5λ, and the receiving antenna spacing D r = 0.5λ, the virtual receiving antenna arrangement has a spacing D of about 0.5λ. d and satisfies placement condition A.

[0225] In addition, in FIG. 14(a), the receiving antenna Rx#3 is spaced apart from the receiving antenna Rx#1 in the horizontal direction (horizontal spacing) D H The receiving antenna Rx#3 is placed at a distance D H and at a vertical distance of D V where the horizontal spacing is D H =λ / (2 sinψ)≒0.7λ (when ψ is 45°), thereby satisfying placement condition B. In FIG. 14(a), the receiving antenna Rx#3 is spaced D apart from the receiving antenna Rx#1 or Rx#2 in the vertical direction. V Therefore, the virtual receiving antenna arrangement shown in Fig. 14(b) is a vertical line with an interval D V This does not include the antenna arrangement in which the antenna is arranged as shown in FIG.

[0226] In this way, in (a) of Fig. 14, the transmitting antennas Tx#1 and Tx#2 are arranged in the diagonal direction ψ. Also, in (a) of Fig. 14, the two receiving antennas Rx#1 and Rx#2 are arranged in the diagonal direction ψ with an interval D r In FIG. 14(a), Rx#3 and Rx#1 are spaced apart by a distance D in the horizontal direction. H (D r= 0.5λ or wider spacing).

[0227] 14(b), VA#1, VA#2, VA#4, and VA#5 are arranged in the diagonal direction ψ, and the distance between two adjacent VA#1 and VA#2 is Dd (=0.5λ). Also, as shown in FIG. 14(b), VA#1 and VA#3 (or VA#4 and VA#6) are arranged in the horizontal direction, and the distance between VA#1 and VA#3 (or the distance between VA#4 and VA#6) in the horizontal direction is D d Wider D H 14(b) satisfies the arrangement conditions A and B.

[0228] In addition, the number of transmitting antennas is N Tx If there are three or more receiving antennas Na, it is sufficient that at least two of them (for example, Tx#1 and Tx#2) satisfy the above-mentioned placement condition. Also, if there are three or more receiving antennas Na, it is sufficient that at least three of them (for example, Rx#1, Rx#2, and Rx#3) satisfy the above-mentioned placement condition.

[0229] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described arrangement example 2 is applied will be described.

[0230] For example, the direction estimation unit 213 performs code separation processing on the code-multiplexed signal transmitted from the transmission antenna 106 to obtain a received signal DeMul z ncm (f b_cfar ,f s_cfar ), the virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) and performs direction estimation processing. Note that the operation of direction estimation unit 213 is the same as the operation when arrangement example 1 is used, and therefore a description thereof will be omitted.

[0231] <Example of direction estimation result for arrangement example 2> Next, an example of a direction estimation result (computer simulation result) when the antenna arrangement according to the above-described Arrangement Example 2 is applied will be described.

[0232] Figures 15(a) and (b) show angle measurement results using the beamformer method when target reflected waves are received from a horizontal direction of 0° and a vertical direction of 40° in the MIMO radar antenna arrangement shown in Figure 14(a). Figures 15(a) and (b) show the angle measurement results for arrangement example 1 (e.g., Figures 8(a) and (b)) under the same target conditions, and are plotted using the same graphs.

[0233] 15(a) and 15(b) show that the main beam is oriented in the horizontal 0° and vertical 40° directions, and that no grating lobes are generated. Furthermore, in the case of the MIMO radar antenna arrangement shown in FIG. 14(a), the horizontal beam width is approximately 18° and the vertical beam width is approximately 20° (in the case of a Fourier beam pattern oriented in the horizontal 0° and vertical 0° directions). Therefore, with the antenna arrangement in FIG. 14(a), compared to the antenna arrangement in FIG. 1, the 3-dB beam width in the horizontal direction is reduced by 6.6% (= 18 / 37) and the 3-dB beam width in the vertical direction is reduced by 3.4% (= 20 / 59), which is expected to improve the accuracy of two-dimensional angle measurement in the horizontal and vertical directions (for example, an improvement in accuracy of approximately 1.5 to 3 times).

[0234] In this way, in Arrangement Example 2, by satisfying Arrangement Conditions A and B, the same effect as in Arrangement Example 1 can be obtained.

[0235] The antenna arrangement shown in (a) of Figure 14 is an example of an antenna arrangement that satisfies arrangement conditions A and B, but is not limited to this and may be an antenna arrangement that satisfies arrangement condition A and at least one of arrangement conditions B and C.

[0236] For example, the antenna arrangement shown in Fig. 16(a) is a modified example of arrangement example 2 that satisfies arrangement conditions A, B, and C. Fig. 16(b) is a diagram showing an example of the arrangement of virtual receiving antennas obtained by the antenna arrangement shown in Fig. 16(a). Even when the antenna arrangement shown in Fig. 16(a) is used, the same effect as arrangement example 2 can be obtained, and grating lobes can be removed.

[0237] In the antenna arrangement shown in FIG. 16(a), Rx#3 is spaced apart from Rx#1 or Rx#2 by a distance D in the vertical direction. V 16(b), in the virtual receiving antenna arrangement, the virtual receiving antennas VA#2 and VA#6 are arranged in a line in the vertical direction at an interval D V In this way, depending on the positional relationship between the placement of the transmitting antenna 106 and the placement of the receiving antenna 202, a placement that satisfies placement condition B or placement condition C is possible.

[0238] Arrangement Example 2 and the modified example of Arrangement Example 2 have been described above.

[0239] <Layout example 3> In the above-described Arrangement Examples 1 and 2, an antenna configuration has been described in which one receiving antenna 202 is arranged in a line in the horizontal direction relative to another receiving antenna 202 arranged in an oblique direction in order to satisfy Arrangement Condition B. Also, in the above-described Arrangement Examples 1 and 2, an antenna configuration has been described in which one receiving antenna 202 is arranged in a line in the vertical direction relative to another receiving antenna 202 arranged in an oblique direction in order to satisfy Arrangement Condition C.

[0240] In Arrangement Example 3, instead of the MIMO antenna arrangement according to the above-described arrangement examples, a method will be described in which a MIMO antenna arrangement that satisfies the following arrangement conditions can be used to obtain the same effect as that achieved by satisfying arrangement condition B or arrangement condition C. Note that, hereinafter, the arrangement conditions corresponding to arrangement condition B and arrangement condition C, respectively, will be referred to as "arrangement condition B1" and "arrangement condition C1."

[0241] In Arrangement Example 3, Arrangement Condition A may be the same as Arrangement Examples 1 and 2.

[0242] [Placement condition B1] At least one of the receiving antennas different from the receiving antenna arranged in the diagonal direction ψ according to the arrangement condition A is arranged at a horizontal distance D from the receiving antenna arranged in the diagonal direction ψ. H On the diagonal line ψ passing through point P, a distance Dd The data are placed at positions shifted by an interval that is an integer multiple of .

[0243] For example, among the plurality of receiving antennas 202, at least two receiving antennas (for example, corresponding to the first receiving antenna) arranged in the diagonal direction ψ and other receiving antennas (for example, corresponding to the second receiving antenna) different from the at least one of the first receiving antennas are spaced apart from each other by an interval D in the horizontal direction. H (D d In the diagonal direction ψ passing through the position P (which is a wider distance), d are placed at positions that are an integer multiple of .

[0244] For example, at least one of the receiving antennas (for example, Rx#3 in FIG. 17(a)) except for the receiving antennas arranged in the diagonal direction ψ (for example, Rx#1 and Rx#2 in FIG. 17(a) described later) is spaced apart from the receiving antenna arranged in the diagonal direction ψ (for example, Rx#2 in FIG. 17(a)) by a horizontal distance D in the horizontal direction. H On the straight line of the diagonal direction ψ passing through the point P (point P1 in FIG. 17(a)), a distance Ds (Ds=2D d ) shifted position, where the horizontal spacing D H is λ / (2sinψ)≧D H >λ / 2.

[0245] In addition, D H > λ / (2sinψ), grating lobes may occur in a specific azimuth / elevation angle range. If the radar detection area is a wide-angle range, there is a possibility that the grating lobes may cause false detections. However, if the radar detection area is a relatively narrow area near the front, there is no effect of grating lobes, and there is no degradation in radar detection performance. Therefore, D H >λ / (2 sin ψ).

[0246] [Placement condition C1] At least one of the receiving antennas different from the receiving antenna arranged in the diagonal direction ψ according to the arrangement condition A is arranged at a vertical distance D in the vertical direction from the receiving antenna arranged in the diagonal direction ψ. V On the diagonal line ψ passing through point P, a distance D d The data are placed at positions shifted by an interval that is an integer multiple of .

[0247] For example, among the plurality of receiving antennas 202, at least two receiving antennas (e.g., corresponding to the first receiving antennas) arranged in the diagonal direction ψ and other receiving antennas (e.g., corresponding to the second receiving antennas) are arranged at an interval D in the vertical direction from at least one of the first receiving antennas. H (D d In the diagonal direction ψ passing through the position P (which is a wider distance), d are placed at positions that are an integer multiple of .

[0248] For example, at least one of the receiving antennas (for example, Rx#3 in FIG. 17(a)) other than the receiving antennas arranged in the diagonal direction ψ (for example, Rx#1 and Rx#2 in FIG. 17(a) described later) is spaced apart from the receiving antenna arranged in the diagonal direction ψ by a vertical distance D in the vertical direction from the receiving antenna (for example, Rx#1 in FIG. 17(a)). V On the diagonal line ψ passing through point P (point P2 in FIG. 17(a)), a distance Ds (Ds=D d ) shifted position, where the vertical spacing D V is λ / (2cosψ)≧D V The receiving antenna Rx#3 may be set to a distance D H and at a vertical distance of D V is placed at the position.

[0249] In addition, D V> λ / (2cosψ), grating lobes may occur in a specific azimuth / elevation angle range. If the radar detection area is a wide-angle range, there is a possibility that the grating lobes may cause false detections. However, if the radar detection area is a relatively narrow area near the front, there is no effect of grating lobes, and there is no degradation in radar detection performance. Therefore, D H >λ / (2cosψ).

[0250] The above has explained the placement conditions B1 and C1.

[0251] With this antenna arrangement, a virtual receiving antenna (hereinafter referred to as a "first diagonal virtual receiving antenna") is arranged, which is composed of a receiving antenna arranged in the diagonal direction ψ according to arrangement condition A and a transmitting antenna arranged in the diagonal direction ψ.

[0252] In addition to the first diagonal virtual receiving antenna, a virtual receiving antenna (hereinafter referred to as a "second diagonal virtual receiving antenna") consisting of receiving antennas other than the receiving antenna placed in the diagonal direction ψ according to placement condition A and a transmitting antenna placed in the diagonal direction ψ is placed in the diagonal direction ψ.

[0253] Here, the second diagonal virtual receiving antennas (for example, VA#3 and VA#6 in FIG. 17(b)) are spaced apart horizontally by a horizontal distance D from the first diagonal virtual receiving antennas (for example, VA#1, #4, #2, and #5 in FIG. 17(b) to be described later). H , or vertical spacing D V It is shifted and positioned.

[0254] In this way, the virtual receiving antennas configured by the transmitting and receiving antennas of the radar device 10 are arranged at a horizontal distance D from at least one virtual receiving antenna among the virtual receiving antennas (for example, corresponding to the first virtual receiving antenna group) that satisfy the arrangement condition A. H (For example, D d Wider spacing) or vertical spacing D V (For example, Dd In the diagonal direction ψ passing through the position P (which is a wider distance), d The virtual receiving antennas (corresponding to the second antenna group, for example) are arranged at positions spaced apart by an integer multiple of the distance between the first and second receiving antennas.

[0255] Therefore, the phase of the received signal when the receiving antenna 202 is placed on point P (point P1 or point P2 in FIG. 17(b) described later) can be calculated by interpolation processing that uses phase information of the receiving antenna 202 that is placed at a position shifted by the distance Ds from point P and phase change information of the received signal obtained at the first diagonal virtual receiving antenna. By such interpolation processing, Arrangement Example 3 can obtain the same effect as when the receiving antenna 202 is placed at point P (for example, Arrangement Example 1 or Arrangement Example 2), and therefore can also be applied to the simplified two-dimensional angle measurement method. Therefore, when arrangement condition B1 or arrangement condition C1 is satisfied, the same effect as when arrangement condition B or arrangement condition C is satisfied can be obtained.

[0256] In addition, the interval D s is the interval D d This enables the interpolation process in the simplified two-dimensional angle measurement method described above. By applying the simplified two-dimensional angle measurement method, the amount of calculation in the direction estimation unit 213 can be reduced.

[0257] Also, for example, the interval D s is the interval D d The distance between the two-dimensional angles may be set to an interval equal to a reasonable multiple of the distance between the two-dimensional angles. This enables the interpolation process to be performed using the simplified two-dimensional angle measurement method described above. By applying the simplified two-dimensional angle measurement method, the amount of calculation in the direction estimation unit 213 can be reduced.

[0258] 17(a) is a diagram showing an example of the arrangement of MIMO antennas, ie, the transmitting antennas 106 and the receiving antennas 202, according to the above-mentioned arrangement conditions. In the example shown in FIG. 17(a), the number of transmitting antennas N Tx is two (for example, Tx#1 and Tx#2), and the number of receiving antennas Na is three (for example, Rx#1, Rx#2, and Rx#3).

[0259] Figure 17(b) is a diagram showing an example of the arrangement of virtual receiving antennas obtained by the antenna arrangement shown in Figure 17(a). The arrangement of each virtual receiving antenna is calculated by applying equation (12) based on the antenna arrangement shown in Figure 17(a).

[0260] In FIG. 17(a), N Tx The two transmitting antennas Tx#1 to Tx#2 are spaced apart at an angle D in the diagonal direction at an angle ψ (ψ=45° in FIG. 17(a)) with respect to the horizontal direction. t are arranged in

[0261] In addition, in FIG. 17(a), at least two of the Na=3 receiving antennas, Rx#1 to #2, are arranged at intervals D in the same diagonal direction ψ as the diagonal direction in which the transmitting antennas Tx#1 to #2 are arranged. r are arranged in

[0262] Here, the distance between the transmitting antennas is D t and receiving antenna spacing D r is D t and D r Absolute value of the difference D d (=|Dt-Dr|) is about 0.5λ (1x the specified value) d 17(a), for example, the interval D t = 2λ, and spacing Dr = 2.5λ. As a result, as shown in (b) of FIG. 17, in the virtual receiving antenna arrangement, spacing D d Since it contains, placement condition A is satisfied.

[0263] In addition, in FIG. 17(a), the receiving antenna Rx#3 is spaced horizontally apart from the receiving antenna Rx#2 arranged in the diagonal direction ψ by a horizontal distance D H On the diagonal line ψ passing through point P1, there is a line spaced apart from point P1 by Ds1=2D d The horizontal spacing D H =λ / (2 sinψ)≈0.7λ (when ψ is 45°), which satisfies the placement condition B1.

[0264] In addition, in FIG. 17(a), the receiving antenna Rx#3 is arranged at a vertical distance D in the vertical direction from the receiving antenna Rx#1 arranged in the diagonal direction ψ. V On the diagonal line ψ passing through point P2, there is a line spaced apart from point P2 by Ds2=D d The vertical spacing D V =λ / (2cosψ)≈0.7λ (when ψ is 45°), which satisfies the placement condition C1.

[0265] The diagonal direction is not limited to ψ=45°, and may be set to, for example, about ψ=30° to 60°.

[0266] In addition, the number of transmitting antennas N Tx If there are three or more receiving antennas Na, it is sufficient that at least two of them (for example, Tx#1 and Tx#2) satisfy the above-mentioned placement condition. Also, if there are three or more receiving antennas Na, it is sufficient that at least three of them (for example, Rx#1, Rx#2, and Rx#3) satisfy the above-mentioned placement condition.

[0267] Next, an example of the direction estimation process in the direction estimation unit 213 when the above-described arrangement example 3 is applied will be described.

[0268] For example, the direction estimation unit 213 performs code separation processing on the code-multiplexed signal transmitted from the transmission antenna 106 to obtain a received signal DeMul z ncm (f b_cfar ,f s_cfar ), the virtual receiving array correlation vector h(f b_cfar ,f s_cfar ) and performs direction estimation processing. Note that the operation of direction estimation unit 213 is the same as the operation when arrangement example 1 is used, and therefore a description thereof will be omitted.

[0269] <Example of direction estimation result for layout example 3> Next, an example of a direction estimation result (computer simulation result) when the antenna arrangement according to the above-described Arrangement Example 3 is applied will be described.

[0270] Figures 18(a) and (b) show angle measurement results using the beamformer method when target reflected waves are received from a horizontal direction of 0° and a vertical direction of 40° in the MIMO radar antenna arrangement shown in Figure 17(a). Figures 18(a) and (b) show the angle measurement results for arrangement example 1 (e.g., Figures 8(a) and (b)) under the same target conditions, and are plotted using the same graphs.

[0271] 18(a) and 18(b) show that the main beam is oriented in the horizontal 0° and vertical 40° directions, and that no grating lobes are generated. Furthermore, in the case of the MIMO radar antenna arrangement shown in FIG. 17(a), the horizontal beam width is approximately 14° and the vertical beam width is approximately 15° (in the case of a Fourier beam pattern oriented in the horizontal 0° and vertical 0° directions). Therefore, with the antenna arrangement in FIG. 17(a), compared to the antenna arrangement in FIG. 1, the 3-dB beam width in the horizontal direction is reduced by 3.8% (= 14 / 37) and the 3-dB beam width in the vertical direction is reduced by 2.5% (= 15 / 59), and an improvement in the accuracy of two-dimensional angle measurement in the horizontal and vertical directions (for example, an improvement in accuracy of approximately 2.6 to 3.9 times) is expected.

[0272] In this way, in Arrangement Example 3, by satisfying Arrangement Condition A and at least one of Arrangement Condition B1 and Arrangement Condition C1, the same effect as in Arrangement Example 1 can be obtained.

[0273] The antenna arrangement in Arrangement Example 3 is not limited to the antenna arrangement example shown in FIG. 17(a).

[0274] For example, the antenna arrangement shown in (a) of FIG. 19 is a modified example of arrangement example 3 that satisfies arrangement conditions A, B1, and C1. The antenna arrangement shown in (a) of FIG. 19 has a D r =3D d , Ds1=D d 19(a) is a diagram showing an example of the arrangement of virtual receiving antennas obtained by the antenna arrangement shown in FIG. 19(a).

[0275] Even when the antenna arrangement shown in (a) of FIG. 19 is used, the same effect as in Arrangement Example 1 can be obtained. In the case of the antenna arrangement shown in (a) of FIG. 19, the intervals Ds1 and Ds2 are D d / 2, D d The interval is a rational multiple (1 / 2) of .

[0276] Furthermore, the antenna arrangements of the above-described Arrangement Example 3 (for example, (a) of FIG. 17) and the modified example (for example, (a) of FIG. 19) are examples of antenna arrangements that satisfy the arrangement conditions A, B1, and C1 for Arrangement Example 1, but are not limited to this. For example, for Arrangement Example 2, an antenna arrangement that satisfies the arrangement conditions A, B1, and C1 (for example, receiving antenna spacing D r In this case, the same effect as in Arrangement Example 2 can be obtained.

[0277] In addition, in Arrangement Example 3, the distance D between the transmitting antennas 106 is t is the interval D d The distance D between the receiving antennas 202 may be an integer multiple or a rational multiple of r is the interval D d The distance Ds between the point P on the straight line in the diagonal direction ψ and the receiving antenna 202 is the distance D d It can be an integer or rational multiple of .

[0278] Arrangement example 3 has been described above.

[0279] Note that, in the above-mentioned Arrangement Examples 1, 2, and 3, the arrangement examples where the diagonal direction ψ=45° under arrangement condition A have been described, but the value of the diagonal direction ψ is not limited to this. For example, (a) and (b) of Figure 20 show an example of a MIMO antenna arrangement and an example of a virtual receiving antenna arrangement when the diagonal direction ψ=30° under arrangement condition A. The antenna arrangement shown in (a) of Figure 20 is an antenna arrangement that satisfies arrangement condition A and arrangement condition B, and can obtain the same effects as the above-mentioned arrangement examples.

[0280] For example, by setting the diagonal direction ψ=30°, the horizontal aperture length is wider than the vertical aperture length, resulting in a greater improvement in the accuracy of horizontal direction estimation. For example, in the case of the MIMO radar antenna arrangement shown in FIG. 20(a), the horizontal beam width is approximately 16° and the vertical beam width is approximately 51° (in the case of a Fourier beam pattern oriented in the horizontal 0° and vertical 0° directions) (not shown). Therefore, with the antenna arrangement shown in FIG. 20(a), compared to the antenna arrangement shown in FIG. 1, the 3-dB beam width in the horizontal direction is reduced by 4.3% (=16 / 37) and the 3-dB beam width in the vertical direction is reduced by 8.6% (=51 / 59). As a result, the improvement in horizontal angle measurement accuracy (an expected improvement of approximately 2.3 times) is greater than the improvement in vertical angle measurement accuracy (an expected improvement of approximately 1.2 times).

[0281] An embodiment of the present disclosure has been described above.

[0282] The configuration of the radar device according to an embodiment of the present disclosure is not limited to the configuration shown in Fig. 5. For example, the radar device does not need to include the CFAR unit 211.

[0283] In addition, the number of transmitting antennas in the antenna arrangement described in the embodiment of the present disclosure, N Tx The parameters such as the number of receiving antennas Na, the spacing between antennas (for example, transmitting antennas, receiving antennas or virtual receiving antennas), and the angle ψ of the diagonal direction are merely examples, and other different values ​​may be used.

[0284] In addition, in the embodiment of the present disclosure, an example has been described in which 0.5λ is used as one of the antenna spacings, but the antenna spacing is not limited to 0.5λ and may be another spacing of about 0.5λ. For example, spacing of about 0.5λ to 0.8λ may be applied.

[0285] In a radar device according to an embodiment of the present disclosure, the radar transmitter and the radar receiver may be individually located at physically separate locations. Also, in a radar receiver according to an embodiment of the present disclosure, the direction estimator and other components may be individually located at physically separate locations.

[0286] Although not shown, a radar device according to an embodiment of the present disclosure includes, for example, a central processing unit (CPU), a storage medium such as a read-only memory (ROM) storing a control program, and a working memory such as a random access memory (RAM). In this case, the functions of the above-described units are realized by the CPU executing the control program. However, the hardware configuration of the radar device is not limited to this example. For example, each functional unit of the radar device may be realized as an integrated circuit (IC). Each functional unit may be individually implemented on a single chip, or a single chip may include some or all of the functional units.

[0287] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the disclosure.

[0288] Furthermore, the notation "... section" in the above-described embodiments may be replaced with other notations such as "... circuitry," "... assembly," "... device," "... unit," or "... module."

[0289] In each of the above embodiments, the present disclosure has been described as an example configured using hardware, but the present disclosure can also be realized by software in cooperation with hardware.

[0290] Furthermore, each functional block used in the description of each of the above embodiments is typically realized as an LSI, which is an integrated circuit. The integrated circuit controls each functional block used in the description of the above embodiments and may have input and output terminals. These may be individually integrated into single chips, or some or all of them may be integrated into a single chip. While the term LSI is used here, it may also be called an IC, system LSI, super LSI, or ultra LSI depending on the level of integration.

[0291] Furthermore, the method of integration is not limited to LSI, but may be realized using a dedicated circuit or a general-purpose processor. It is also possible to use a field programmable gate array (FPGA) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connections or settings of circuit cells inside the LSI.

[0292] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology may be used to integrate functional blocks. The application of biotechnology, etc. is also a possibility.

[0293] Summary of this disclosure A radar device according to an embodiment of the present disclosure includes a transmitting circuit that transmits a transmission 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 transmission signal reflected by an object using the other of the first antenna group and the second antenna group, wherein an r1 antenna and an r2 antenna of the first antenna group are arranged adjacent to each other in a third direction that is different from both a first direction and a second direction orthogonal to the first direction, a t1 antenna and a t2 antenna of the second antenna group are arranged adjacent to each other in the third direction, and an r3 antenna of the first antenna group is arranged adjacent to each other in the third direction. and the r1 antenna and the r2 antenna are positioned at positions shifted in each of the first direction and the second direction from the r1 antenna to a position wider than a specified value based on the wavelength of the transmission signal, and the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is the specified value, or the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is an integer multiple of the specified value that is 2 or more, and either the distance between the r1 antenna and the r2 antenna or the distance between the t1 antenna and the t2 antenna is the specified value.

[0294] In a radar device according to an embodiment of the present disclosure, when the first direction is a horizontal direction, the second direction is a vertical direction, and when the first direction is a vertical direction, the second direction is a horizontal direction.

[0295] In a radar device according to an embodiment of the present disclosure, the number of antennas in the first antenna group is three or four, and the number of antennas in the second antenna group is two or three.

[0296] In a radar device according to one embodiment of the present disclosure, the r1 antenna and the r3 antenna are arranged in the second direction, and the distance between the r1 antenna and the r3 antenna in the second direction is wider than the specified value.

[0297] In a radar device according to an embodiment of the present disclosure, the r1 antenna and the r3 antenna are arranged in a fourth direction different from the first direction, the second direction, and the third direction.

[0298] In a radar device according to one embodiment of the present disclosure, the multiple virtual receiving antennas constituted by the first antenna group and the second antenna group include a first virtual receiving antenna group arranged in the third direction and a second virtual receiving antenna group that is different from the first virtual receiving antenna group and arranged in a fifth direction parallel to the third direction, at least one of the spacings between two adjacent virtual receiving antennas included in the first virtual receiving antenna group is a specified value based on the wavelength of the transmitted signal, and the spacing in the first direction between one virtual antenna included in the first virtual receiving antenna group and one virtual receiving antenna included in the second virtual receiving antenna group is wider than the specified value.

[0299] In a radar device according to an embodiment of the present 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 a predetermined number times the specified value.

[0300] In a radar device according to an embodiment of the present disclosure, the specified value is 0.5 wavelength.

[0301] In a radar device according to an embodiment of the present disclosure, the distance between the r1 antenna and the r2 antenna is equal to or less than the wavelength / (2×sinψ) with respect to the angle ψ formed by the first direction and the third direction.

[0302] In a radar device according to an embodiment of the present disclosure, the distance between the r1 antenna and the r3 antenna is equal to or less than the wavelength / (2×cos ψ) with respect to the angle ψ formed by the first direction and the third direction.

[0303] In a radar device according to an embodiment of the present disclosure, the receiving circuit calculates a phase change for each interval of the specified value using a received signal from a virtual receiving antenna that is arranged in the third direction among the plurality of virtual receiving antennas, calculates a phase difference in the first direction using received signals from at least two virtual receiving antennas that are arranged in the first direction among the plurality of virtual receiving antennas, calculates a phase difference in the second direction using received signals from at least two virtual receiving antennas that are arranged in the second direction among the plurality of virtual receiving antennas, and extracts an arrival angle in the first direction and an arrival angle 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 for each interval of the specified value from among combinations of the phase difference in the first direction and the phase difference in the second direction.

[0304] In a radar device according to one embodiment of the present disclosure, when the at least two virtual receiving antennas are not arranged in either the first direction or the second direction, the receiving circuit calculates the phase difference in either one of the directions by interpolation processing using the received signal of one of the virtual receiving antennas in the second virtual receiving antenna group.

[0305] In a radar device according to one embodiment of the present disclosure, the distance between the r1 antenna and the r2 antenna is a predetermined multiple of at least twice the specified value, and the distance between the t1 antenna and the t2 antenna is a predetermined multiple of at least twice the specified value.

[0306] In the radar device according to the embodiment of the present disclosure, the angle formed between the first direction and the third direction is within a range of 30° or less and 60° or less.

[0307] A radar signal processing method according to an embodiment of the present disclosure includes transmitting a transmission signal using one of a first antenna group and a second antenna group, and receiving a reflected wave signal of the transmission signal reflected by an object using the other of the first antenna group and the second antenna group, wherein the r1 antenna and the r2 antenna of the first antenna group are arranged adjacent to each other in a third direction that is different from both a first direction and a second direction orthogonal to the first direction, the t1 antenna and the t2 antenna of the second antenna group are arranged adjacent to each other in the third direction, and the r3 antenna of the first antenna group is arranged adjacent to each other in the third direction. and the r1 antenna and the r2 antenna are arranged at positions shifted from the r1 antenna to a position wider than a specified value based on the wavelength of the transmission signal in each of the first direction and the second direction, and the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is the specified value, or the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is an integer multiple of the specified value that is two or more, and either the distance between the r1 antenna and the r2 antenna or the distance between the t1 antenna and the t2 antenna is the specified value.

[0308] In a radar signal processing method according to one embodiment of the present disclosure, when the first direction is a horizontal direction, the second direction is a vertical direction, and when the first direction is a vertical direction, the second direction is a horizontal direction.

[0309] In a radar signal processing method according to an embodiment of the present disclosure, the number of antennas in the first antenna group is three or four, and the number of antennas in the second antenna group is two or three.

[0310] In a radar signal processing method according to one embodiment of the present disclosure, the r2 antenna and the r3 antenna are arranged in the second direction, and the distance between the r2 antenna and the r3 antenna in the second direction is wider than the specified value.

[0311] In a radar signal processing method according to an embodiment of the present disclosure, the r1 antenna and the r3 antenna are arranged in a fourth direction different from the first direction, the second direction, and the third direction.

[0312] In a radar signal processing method according to one embodiment of the present disclosure, the multiple virtual receiving antennas constituted by the first antenna group and the second antenna group include a first virtual receiving antenna group arranged in the third direction and a second virtual receiving antenna group that is different from the first virtual receiving antenna group and arranged in a fifth direction parallel to the third direction, at least one of the spacings between two adjacent virtual receiving antennas included in the first virtual receiving antenna group is a specified value based on the wavelength of the transmitted signal, and the spacing in the first direction between one virtual antenna included in the first virtual receiving antenna group and one virtual receiving antenna included in the second virtual receiving antenna group is wider than the specified value. [Industrial Applicability]

[0313] The present disclosure is suitable for a radar device that detects a wide angle range. [Explanation of symbols]

[0314] 10 Radar equipment 100 Radar transmitter 101 Radar transmission signal generator 102 Modulation signal generator 103 VCO 104 Code generator 105 Phase Rotation Unit 106 Transmitting Antenna 200 Radar receiver 201 Antenna system processing unit 202 Receiving antenna 203 Receiving Radio Unit 204 Mixer section 205 LPF 206 Signal Processing Unit 207 AD conversion section 208 Beat Frequency Analysis Unit 209 Output switching unit 210 ドップラ Analysis Department 211 CFAR Department 212 Symbol Multiple Separation Part 213 Direction estimation section

Claims

1. a transmitting circuit that transmits a transmission signal using one of the first antenna group and the second antenna group; a receiving circuit that receives a reflected wave signal resulting from the transmission signal being reflected by an object, using the other of the first antenna group and the second antenna group; Equipped with an r1 antenna and an r2 antenna of the first antenna group are arranged adjacent to each other in a third direction different from both a first direction and a second direction orthogonal to the first direction; the t1-th antenna and the t2-th antenna of the second antenna group are arranged adjacent to each other in the third direction, an r3-th antenna of the first antenna group is disposed at a position shifted from the third direction in each of the first direction and the second direction by a distance greater than a specified value based on a wavelength of the transmission signal; the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is the specified value, or an absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is an integer multiple of the specified value that is 2 or more, and either the distance between the r1 antenna and the r2 antenna or the distance between the t1 antenna and the t2 antenna is the specified value; Radar equipment.

2. when the first direction is horizontal, the second direction is vertical; If the first direction is vertical, the second direction is horizontal. The radar device according to claim 1 .

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

4. the r1 antenna and the r3 antenna are arranged in the second direction, a distance between the r1 antenna and the r3 antenna in the second direction is wider than the specified value; The radar device according to claim 1 .

5. the r1 antenna and the r3 antenna are arranged in a fourth direction different from the first direction, the second direction, and the third direction; The radar device according to claim 1 .

6. The plurality of virtual receiving antennas constituted by the first antenna group and the second antenna group include: a first virtual receiving antenna group arranged in the third direction; a second virtual receiving antenna group that is different from the first virtual receiving antenna group and is arranged in a fifth direction parallel to the third direction, at least one of the intervals between two adjacent virtual receiving antennas included in the first virtual receiving antenna group is a specified value based on the wavelength of the transmission signal; a distance in the first direction 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 is wider than the specified value; The radar device according to claim 1 .

7. a 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 a predetermined number times the specified value; The radar device according to claim 6.

8. The specified value is 0.5 wavelengths. The radar device according to claim 1 .

9. With respect to the angle ψ formed by the first direction and the third direction, the distance between the r1 antenna and the r2 antenna is equal to or less than the wavelength / (2 × sinψ). The radar device according to claim 1 .

10. With respect to the angle ψ formed by the first direction and the third direction, the distance between the r1 antenna and the r3 antenna is equal to or less than the wavelength / (2 × cosψ). The radar device according to claim 4.

11. The receiving circuit calculating a phase change for each interval of the specified value using a received signal of a virtual receiving antenna arranged in the third direction among the plurality of virtual receiving antennas; calculating a phase difference in the first direction using received signals of at least two virtual receiving antennas arranged in the first direction among the plurality of virtual receiving antennas; calculating a phase difference in the second direction using received signals of at least two virtual receiving antennas arranged in the second direction among the plurality of virtual receiving antennas; extracting an arrival angle in the first direction and an arrival angle 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 a phase change at each interval of the specified value; The radar device according to claim 6.

12. When the at least two virtual receiving antennas are not arranged in either the first direction or the second direction, The receiving circuit calculating the phase difference in either one of the directions by interpolation processing using a received signal of any one of the virtual receiving antennas in the second virtual receiving antenna group; The radar device according to claim 11.

13. the distance between the r1 antenna and the r2 antenna is a predetermined number times greater than or equal to twice the specified value, The distance between the t1 antenna and the t2 antenna is a predetermined number times greater than or equal to twice the specified value. The radar device according to claim 1 .

14. an angle formed between the first direction and the third direction is in a range of 30° or less and 60° or less; The radar device according to claim 1 .

15. Transmitting a transmission signal using one of the first antenna group and the second antenna group; receiving a reflected wave signal resulting from the transmission signal being reflected by an object, using the other of the first antenna group and the second antenna group; A radar signal processing method, comprising: the r1 antenna and the r2 antenna of the first antenna group are arranged adjacent to each other in a third direction different from both the first direction and a second direction orthogonal to the first direction, the t1-th antenna and the t2-th antenna of the second antenna group are arranged adjacent to each other in the third direction, an r3-th antenna of the first antenna group is disposed at a position shifted from the third direction in each of the first direction and the second direction by a distance greater than a specified value based on a wavelength of the transmission signal; the absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is the specified value, or an absolute value of the difference between the distance between the r1 antenna and the r2 antenna and the distance between the t1 antenna and the t2 antenna is an integer multiple of the specified value that is 2 or more, and either the distance between the r1 antenna and the r2 antenna or the distance between the t1 antenna and the t2 antenna is the specified value; Radar signal processing method.

16. when the first direction is horizontal, the second direction is vertical; If the first direction is vertical, the second direction is horizontal.

16. The radar signal processing method of claim 15.

17. The number of antennas in the first antenna group is three or four, and the number of antennas in the second antenna group is two or three.

16. The radar signal processing method of claim 15.

18. the r2 antenna and the r3 antenna are arranged in the second direction, a distance between the r2 antenna and the r3 antenna in the second direction is wider than the specified value; 16. The radar signal processing method of claim 15.

19. the r1 antenna and the r3 antenna are arranged in a fourth direction different from the first direction, the second direction, and the third direction; 16. The radar signal processing method of claim 15.

20. The plurality of virtual receiving antennas constituted by the first antenna group and the second antenna group include: a first virtual receiving antenna group arranged in the third direction; a second virtual receiving antenna group that is different from the first virtual receiving antenna group and is arranged in a fifth direction parallel to the third direction, at least one of the intervals between two adjacent virtual receiving antennas included in the first virtual receiving antenna group is a specified value based on the wavelength of the transmission signal; a distance in the first direction 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 is wider than the specified value; 16. The radar signal processing method of claim 15.

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