Radar system

Abstract

To provide a radar system capable of accurately detecting a target direction in two directions intersecting each other.SOLUTION: A radar system 1 comprises a transmission antenna group 3 and a receiving antenna group 4. The radar system 1 comprises a first direction detection part 61 detecting a target direction in a horizontal direction U using a first virtual array antenna including a first antenna element and a second antenna element disposed in the horizontal direction U. The radar system 1 further comprises a second direction detection part 62 detecting the target direction in a vertical direction V using a second virtual array antenna including a first antenna element and a second antenna element disposed in the vertical direction V. The radar system 1 still further comprises a signal determination part 63 determining whether a signal corresponding to the target detected by the second direction detection part 62 is a real image a false image on the basis of detection result of the first direction detection part 61.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, there is known a radar device that detects the azimuth of a target in both the horizontal and vertical directions by MIMO array technology using multiple transmitting and receiving antennas arranged in the horizontal and vertical directions (see, for example, Patent Document 1). Note that MIMO is an abbreviation for Multi Input Multi Output. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7027579 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when estimating direction by MIMO, the outbound and return paths of radio waves between the radar device and the target object may not match due to the influence of multipath. In this case, a false peak occurs in a direction where the target object does not exist. The occurrence of such false images significantly reduces the accuracy of direction estimation in a radar device that detects the direction of a target object in two mutually intersecting directions as in Patent Document 1, but Patent Document 1 does not mention this at all, and there is still room for improvement.

[0005] An object of the present disclosure is to provide a radar device capable of detecting the azimuth of a target in two intersecting directions with high accuracy. [Means for solving the problem]

[0006] The invention described in claim 1 is A radar device that detects targets using radio waves, a transmitting antenna group (3) including a plurality of first antenna elements arranged side by side in a predetermined first direction and a second direction intersecting the first direction; a receiving antenna group (4) including a plurality of second antenna elements arranged in a line in the first direction and the second direction; a first azimuth detection unit (61) that detects an azimuth of a target in a first direction using a first virtual array antenna including a plurality of the first antenna elements arranged in a first direction and a plurality of second antenna elements arranged in the first direction; a second azimuth detection unit (62) that detects the azimuth of the target in the second direction using a second virtual array antenna including a plurality of first antenna elements arranged in the second direction and a plurality of second antenna elements arranged in the second direction; and a signal determination section (63) that determines whether a signal corresponding to a target detected by each of the first and second direction detection sections is a real image or a false image.

[0007] In this manner, if the signal determination unit is configured to determine whether the signal corresponding to the target is a real image or a false image, the target azimuth can be detected using the signal determined to be a real image by the signal determination unit, thereby suppressing a decrease in detection accuracy of the target azimuth caused by a false image. Therefore, the radar device of the present disclosure can accurately detect the azimuth of the target in two intersecting directions.

[0008] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a radar device according to a first embodiment. [Diagram 2] 1 is a schematic diagram showing a transmitting antenna group including a plurality of actual transmitting antenna elements and a receiving antenna group including a plurality of actual receiving antenna elements in a radar device according to a first embodiment. FIG. [Diagram 3]FIG. 2 is an explanatory diagram for explaining a detection model for the azimuths of a target in two intersecting directions. [Figure 4] FIG. 2 is an explanatory diagram for explaining a method for detecting the azimuths of a target in two intersecting directions. [Diagram 5] FIG. 2 is an explanatory diagram for explaining a first virtual array antenna in the radar device according to the first embodiment. [Figure 6] 1A and 1B are explanatory diagrams for explaining a case where the outgoing path and the return path of the radio wave coincide with each other and a case where the outgoing path and the return path of the radio wave do not coincide with each other. [Figure 7] 5 is a flowchart showing the flow of a target detection process executed by a control unit of the radar device according to the first embodiment. [Figure 8] 5 is a flowchart showing a flow of horizontal direction detection executed by a control unit of the radar device according to the first embodiment. [Figure 9] 5 is a flowchart showing a flow of azimuth detection in the vertical direction executed by a control unit of the radar device according to the first embodiment. [Figure 10] FIG. 2 is an explanatory diagram for explaining an antenna configuration realized by first antenna elements arranged in a vertical direction and second antenna elements arranged in a row in the horizontal direction. [Figure 11] FIG. 2 is an explanatory diagram for explaining an antenna configuration realized by first antenna elements arranged in a vertical direction and second antenna elements in two rows arranged in a horizontal direction. [Figure 12] FIG. 2 is an explanatory diagram for explaining positions and power levels of three targets in one embodiment. [Figure 13] FIG. 13 is a spectrum diagram showing a simulation result when estimating the horizontal directions of the three targets shown in FIG. 12 in a case where the outgoing path and the return path of the radio wave coincide with each other. [Figure 14] FIG. 13 is a spectrum diagram showing a simulation result when the vertical direction of a target is estimated in the direction corresponding to the first peak detected in the horizontal direction estimation. [Figure 15]FIG. 13 is a spectrum diagram showing a simulation result when the vertical direction of a target is estimated in the direction corresponding to the second peak detected in the horizontal direction estimation. [Figure 16] FIG. 13 is a spectrum diagram showing the simulation results for the vertical azimuth under conditions in which reflected waves are mixed, where the outgoing and return paths of radio waves coincide and where they do not coincide. [Figure 17] 10 is a flowchart showing a flow of a vertical direction detection process executed by a control unit of a radar device according to a second embodiment. [Figure 18] FIG. 13 is a spectrum diagram showing the simulation results for the vertical azimuth under conditions in which reflected waves are mixed, where the outgoing and return paths of radio waves coincide and where they do not coincide. [Figure 19] FIG. 11 is an explanatory diagram for explaining an extended array antenna in a radar device according to a third embodiment. [Figure 20] FIG. 11 is an explanatory diagram for explaining a covariance matrix of an extension array antenna in a radar device according to a third embodiment. [Figure 21] FIG. 11 is an explanatory diagram for explaining a window function. [Figure 22] FIG. 13 is a schematic diagram showing a transmitting antenna group including a plurality of actual transmitting antenna elements and a receiving antenna group including a plurality of actual receiving antenna elements in a radar device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same reference numerals are used for parts that are the same as or equivalent to those described in the preceding embodiments, and the description thereof may be omitted. In addition, in the embodiments, when only a part of the components is described, the components described in the preceding embodiments can be applied to the other parts of the components. In the following embodiments, each embodiment can be partially combined with each other, even if not specifically stated, as long as it does not cause any trouble in combination.

[0011] (First embodiment) The present embodiment will be described with reference to Fig. 1 to Fig. 16. In the present embodiment, an example will be described in which a radar device 1 of the present disclosure is applied to a target detection device that is mounted on a vehicle and detects various targets existing around the vehicle.

[0012] The radar device 1 emits radio waves ahead of the vehicle and receives radio waves reflected by a target ahead of the vehicle to determine the distance to the target, the relative speed with respect to the vehicle, the direction with respect to the vehicle, etc.

[0013] The radar device 1 employs the FMCW method as a signal modulation method. The radar device 1 operates at a radio frequency in a frequency band corresponding to millimeter waves (e.g., 76.5 GHz). Note that the operating frequency of the radio waves transmitted and received by the radar device 1 is not limited to a frequency corresponding to millimeter waves, and may be a frequency other than millimeter waves.

[0014] As shown in FIG. 1, the radar device 1 includes a transmitter 2, a transmitting antenna group 3 including a plurality of actual first antenna elements Tx, a receiving antenna group 4 including a plurality of actual second antenna elements Rx, a receiver 5, and a control unit 6.

[0015] The transmitter 2 generates a signal to be transmitted from the transmitting antenna group 3 and transmits it to the transmitting antenna group 3. Specifically, the transmitter 2 generates a local signal and transmits the generated local signal to the receiver 5. The transmitter 2 also generates a chirp signal whose frequency changes continuously and provides the generated chirp signal to the transmitting antenna group 3. The transmitting antenna group 3 then transmits radio waves corresponding to the chirp signal provided from the transmitter 2 toward the front of the vehicle.

[0016] The transmitting antenna group 3 in this example has eight actual first antenna elements Tx1 to Tx8. The eight first antenna elements Tx1 to Tx8 constituting the transmitting antenna group 3 are arranged side by side in the horizontal direction U and the vertical direction V in a state in which the radar device 1 is mounted on a vehicle, as shown in Fig. 2. In this embodiment, the horizontal direction U corresponding to the width direction of the vehicle corresponds to the "predetermined first direction", and the vertical direction V corresponding to the height direction of the vehicle corresponds to the "second direction intersecting with the first direction".

[0017] In the transmitting antenna group 3, seven first antenna elements Tx1 to Tx4, Tx6 to Tx8 are arranged along the vertical direction V at a predetermined interval. The first antenna elements Tx1 to Tx4, Tx6 to Tx8 arranged in the vertical direction V are arranged at an interval of "1dv" which is one time the predetermined vertical reference distance dv. The intervals between the first antenna elements Tx1 to Tx4, Tx6 to Tx8 may be strictly multiples of the vertical reference distance dv, or may include an error that is generally acceptable in the technical field to which the technology of the present disclosure belongs and does not go against the spirit of the technology of the present disclosure. The same applies to the intervals between the second antenna elements Rx1 to Rx8 arranged in the vertical direction V.

[0018] The vertical reference distance dv in this example is set so as to satisfy the following formula F1 when the detection range of the radar device 1 is "±1 / 2·φfov". In this embodiment, φfov is set to "180°" and the vertical reference distance dv is set to "1 / 2·λ", where λ is the wavelength of the radio wave.

[0019] 1 / sin(φfov / 180 π) 2 <dv ···(F1) In addition, in the transmitting antenna group 3, two first antenna elements Tx4 and Tx5 located approximately in the center of the vertical direction V are arranged along the horizontal direction U at a predetermined interval. The first antenna elements Tx4 and Tx5 arranged in the horizontal direction U are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance dh. The interval between the first antenna elements Tx4 and Tx5 may be strictly a multiple of the horizontal reference distance dh, or may include an error that is generally acceptable in the technical field to which the technology of the present disclosure belongs and does not go against the spirit of the technology of the present disclosure. The same applies to the interval between the second antenna elements Rx1 to Rx8 arranged in the horizontal direction U.

[0020] The horizontal reference distance dh in this example is set so as to satisfy the following formula F2 when the detection range of the radar device 1 is "±1 / 2·θfov". In this embodiment, θfov is set to "180°" and the horizontal reference distance dh is set to "1 / 2·λ", where λ is the wavelength of the radio wave.

[0021] 1 / sin(θfov / 180 π) 2 <dh ···(F2) The receiving antenna group 4 receives radio waves and the like transmitted from the transmitting antenna group 3 and reflected by a target. In this example, the receiving antenna group 4 is composed of eight actual second antenna elements Rx1 to Rx8. The eight second antenna elements Rx1 to Rx8 constituting the receiving antenna group 4 are arranged in a row in the horizontal direction U and the vertical direction V when the radar device 1 is mounted on a vehicle.

[0022] Specifically, the receiving antenna group 4 includes four second antenna elements Rx1 to Rx4 aligned along the horizontal direction U at a position close to the first antenna element Tx1 which is one end of the vertical direction V of the transmitting antenna group 3. The receiving antenna group 4 also includes four second antenna elements Rx5 to Rx8 aligned along the horizontal direction U at a position close to the first antenna element Tx8 which is the other end of the vertical direction V of the transmitting antenna group 3. The second antenna elements Rx1 to Rx4 in the first row and the second antenna elements Rx5 to Rx8 in the second row are arranged at an interval of "3dh", which is three times the horizontal reference distance dh.

[0023] In addition, the second antenna elements Rx1 to Rx4 in the first row and the second antenna elements Rx5 to Rx8 in the second row are arranged to face each other in the vertical direction V. The second antenna elements Rx1 to Rx4 in the first row and the second antenna elements Rx5 to Rx8 in the second row are arranged at an interval of "7dv", which is seven times the vertical reference distance dv. The second antenna elements Rx1 to Rx4 in the first row are arranged at an interval of "1 / 2·dv" in the vertical direction V from the first antenna element Tx1, which is one end of the transmitting antenna group 3 in the vertical direction V. The second antenna elements Rx5 to Rx8 in the second row are arranged at an interval of "1 / 2·dv" in the vertical direction V from the first antenna element Tx8, which is the other end of the transmitting antenna group 3 in the vertical direction V.

[0024] Here, the MMIC used in the radar device 1 has, for example, four channels for transmission and four channels for reception. The radar device 1 of this embodiment requires eight channels for transmission and eight channels for reception, so it can be realized with two MMICs. Note that MMIC is an abbreviation for Monolithic Microwave Integrated Circuit.

[0025] The receiving unit 5 generates a beat signal based on the reception signals received by the receiving antenna group 4 and the local signal transmitted from the transmitting unit 2, samples the beat signal, and provides it to the control unit 6. Although not shown, the receiving unit 5 is configured to include a mixer, an amplifier, an AD converter, etc.

[0026] The control unit 6 is an electronic control device mainly composed of a microcomputer equipped with a processor and a memory. The memory is, for example, a ROM, a RAM, etc. Various functions of the microcomputer are realized by the processor executing a program stored in a non-transient physical storage medium.

[0027] The control unit 6 detects the azimuth of the target in two directions intersecting with each other by MIMO using a plurality of first antenna elements Tx1 to Tx8 and second antenna elements Rx1 to Rx8 aligned in the horizontal direction U and vertical direction V.

[0028] Hereinafter, a method for detecting the azimuth of a target will be described with reference to the detection model shown in FIG. 3 and the equations shown in FIG.

[0029] The detection model shown in FIG. 3 is a model that detects the azimuth of the target trg based on the received signals x11, x12, x21, and x22 received by four antenna elements arranged in the horizontal direction U and vertical direction V, such as “a11”, “a12”, “a21”, and “a22”. “a11”, “a12”, “a21”, and “a22” shown in FIG. 3 are array vectors indicating the arrangement of the antenna elements. In the following, the array vectors a11, a12, a21, and a22 and the received signals x11, x12, x21, and x22 shown in FIG. 3 may be written as “alm” or “xlm”. In “alm” and “xlm”, “l” indicates an index corresponding to the first antenna elements Tx1 to Tx8, and “m” indicates an index corresponding to the second antenna elements Rx1 to Rx8.

[0030] In this example, the azimuth of the target trg relative to the radar device 1 is θ1 in the horizontal direction U and φ1 in the vertical direction V. Furthermore, regarding the position of each antenna element, the position in the horizontal direction U is designated as “dum” and the position in the vertical direction V is designated as “dvl.”

[0031] When the array vector a11 is the origin, the received signal xlm received by each antenna element is subjected to a phase change due to the optical path difference according to the distance in the horizontal direction U and the vertical direction V, as shown in (1.1) of Figure 4.

[0032] In this case, the array vector alm is as shown in (1.2) of Fig. 4. Also, the spectrum signal Sp obtained by digital beamforming (DBF) with each received signal xlm as vector X is as shown in (1.3) of Fig. 4.

[0033] For example, suppose that the antenna elements are arranged at half-wavelength (=1 / 2 λ) intervals in the horizontal direction U and vertical direction V, and that the target trg exists in an orientation where θ1=0, φ1=0.

[0034] In this case, first, when the control unit 6 detects the azimuth in the horizontal direction U using the antenna elements corresponding to "a11" and "a12", the spectrum signal Spu1 in the horizontal direction U becomes as shown by (1.4) in FIG.

[0035] In (1.4) of Fig. 4, when θ = 0, the terms reinforce each other, and the absolute value of the spectrum signal Spu1 becomes maximum as shown in (1.5) of Fig. 4. Therefore, the control unit 6 can detect that the orientation of the horizontal direction U of the target trg is θ = 0.

[0036] Next, for "a21" and "a22" that are opposite "a11" and "a12" in the vertical direction V, if the azimuth in the horizontal direction U is set to θ=0 and the signal is reproduced according to (1.3) of Figure 4, the spectrum signal Spu2 in the horizontal direction U will be as shown in (1.6) of Figure 4.

[0037] Then, if the spectral signals Spu1 and Spu2 are defined as a signal vector X in the vertical direction V and the array vector A in the vertical direction V is defined as shown in (1.7) of FIG. 4, the spectral signal Spv in the vertical direction V will be as shown in (1.8) of FIG. 4.

[0038] In (1.8) of Fig. 4, the absolute value of the spectrum signal Spv becomes maximum as each term reinforces each other when φ = 0. This allows the control unit 6 to detect that the orientation of the vertical direction V of the target trg is φ = 0.

[0039] In this way, the orientation of the target trg in the horizontal direction U is detected using antenna elements aligned in the horizontal direction U, and the orientation of the target trg in the vertical direction V is detected based on the spectrum signal Spu corresponding to the detected orientation, making it possible to detect the orientation of the target trg in two intersecting directions.

[0040] Here, the radar device 1 of this embodiment has a plurality of first antenna elements Tx4, Tx5 aligned in the horizontal direction U and a plurality of second antenna elements Rx1 to Rx4 aligned in the horizontal direction U. Therefore, the control unit 6 is configured to detect the azimuth of the target with respect to the horizontal direction U using a first virtual array antenna including the plurality of first antenna elements Tx4, Tx5 aligned in the horizontal direction U and the plurality of second antenna elements Rx1 to Rx4 aligned in the horizontal direction U.

[0041] Moreover, the radar device 1 of this embodiment has a plurality of first antenna elements Tx1 to Tx4, Tx6 to Tx8 aligned in the vertical direction V and a plurality of second antenna elements Rx1 to Rx8 aligned in the vertical direction V. Therefore, the control unit 6 detects the azimuth of the target with respect to the vertical direction V using a second virtual array antenna including the plurality of first antenna elements Tx1 to Tx4, Tx6 to Tx8 aligned in the vertical direction V and the plurality of second antenna elements Rx1 to Rx8 aligned in the vertical direction V. In this embodiment, the configuration in the control unit 6 for detecting the azimuth of the target in the horizontal direction U corresponds to the "first azimuth detection unit 61," and the configuration in the control unit 6 for detecting the azimuth of the target with respect to the vertical direction V corresponds to the "second azimuth detection unit 62."

[0042] The first virtual array antenna of this embodiment has an antenna configuration in which four second antenna elements Rx1, Rx2, Rx3, and Rx4 are added with four virtual antenna elements by using MIMO array technology, as shown in Fig. 5. The first virtual array antenna is obtained by receiving radio waves transmitted from two first antenna elements Tx4 and Tx5 by four second antenna elements Rx1, Rx2, Rx3, and Rx4, and performing predetermined signal processing on the received signals.

[0043] The first virtual array antenna of this embodiment has an antenna aperture length of "11dh". On the other hand, the antenna aperture length in SIMO is "9dh", which is more than half the antenna aperture length of the first virtual array antenna. The first virtual array antenna of this embodiment has an antenna configuration in which the antenna elements are unevenly spaced.

[0044] The first virtual array antenna thus configured is premised on the premise that the outgoing and return paths of the radio waves are substantially the same, as shown in the upper part of Fig. 6 for the direct wave and the mirror-image reflected wave. When the outgoing and return paths of the radio waves are not the same, as shown in the lower part of Fig. 6, the first virtual array antenna detects not only a signal corresponding to the target, but also a signal corresponding to a direction different from the target's direction as a false image. Such false images are generated not only in the first virtual array antenna that detects the direction in the horizontal direction U, but also in the second virtual array antenna that detects the direction in the vertical direction V. Note that mirror-image reflected waves are generated when objects on the side of the road, such as guardrails and walls, or the road surface act as mirrors.

[0045] On the other hand, peaks in azimuths where no target exists (i.e., peaks resulting from false images) tend to have different forms between each virtual array antenna for MIMO and an antenna configuration different from the virtual array antenna.

[0046] In consideration of these, the radar device 1 of this embodiment detects signals corresponding to targets using both each virtual array antenna and an antenna configuration different from the virtual array antenna, and determines whether the signal corresponding to the target is a real image or a false image based on the detection result. In this embodiment, the configuration in the control unit 6 that determines whether the signal corresponding to the target is a real image or a false image corresponds to the "signal determination unit."

[0047] Specifically, the control unit 6 detects a signal corresponding to a target in the horizontal direction U with the first virtual array antenna, and detects a signal corresponding to the target in the horizontal direction U with a SIMO antenna configuration different from the first virtual array antenna. Then, the control unit 6 compares the signals corresponding to the target with the different antenna configurations, and identifies whether the signal corresponding to the target in the horizontal direction U is a real image or a false image based on the comparison result. In this embodiment, the configuration in the control unit 6 that detects a signal corresponding to the target with the first virtual array antenna corresponds to the "first detection unit 611", and the configuration that detects a signal corresponding to the target with an antenna configuration different from the first virtual array antenna corresponds to the "second detection unit 612".

[0048] Furthermore, the control unit 6 detects a signal corresponding to a target in the vertical direction V with the second virtual array antenna, and detects a signal corresponding to a target in the vertical direction V with an antenna configuration of MISO different from the second virtual array antenna. The control unit 6 then compares the signals corresponding to the target with the different antenna configurations, and identifies whether the signal corresponding to the target in the vertical direction V is a real image or a false image based on the comparison result. In this embodiment, the configuration of the control unit 6 that detects a signal corresponding to a target with the second virtual array antenna corresponds to the "third detection unit 621", and the configuration that detects a signal corresponding to a target with an antenna configuration different from the second virtual array antenna corresponds to the "fourth detection unit 622". Note that MISO is an abbreviation for Multi Input Single Output.

[0049] Next, the target detection process executed by the control unit 6 of the radar device 1 will be described with reference to Fig. 7. The process shown in Fig. 7 is executed by the control unit 6 periodically or irregularly when chirp signals are transmitted from the transmitting antenna group 3 at a predetermined transmission period.

[0050] 7, in step S100, the control unit 6 receives a reflected wave from a target at the receiving antenna group 4. This received signal is mixed with a local signal by the mixer of the receiving unit 5. After that, a desired frequency component is extracted by a low-pass filter, and the frequency component is provided from the receiving unit 5 to the control unit 6 as a beat signal.

[0051] Next, the control unit 6 performs distance FFT processing in step S110. The control unit 6 obtains the distance to the target by performing frequency analysis of the beat signal using FFT. Note that FFT is an abbreviation for Fast Fourier Transform.

[0052] Next, the control unit 6 performs a velocity FFT process in step S120. The control unit 6 performs an FFT for each beat frequency component to obtain a Doppler frequency, and obtains the relative velocity of the target based on the Doppler frequency.

[0053] Next, in step S130, the control unit 6 executes a horizontal direction detection process to detect the direction of the target in the horizontal direction U. This horizontal direction detection process will be described with reference to FIG.

[0054] 8, in step S131, the control unit 6 estimates the azimuth of the target in the horizontal direction U by a first virtual array antenna (horizontal MIMO) obtained by MIMO in the horizontal direction U. Specifically, the control unit 6 estimates the azimuth of the target in the horizontal direction U based on the fact that the phase of the received signal received by the antenna elements constituting the first virtual array antenna differs depending on the angle of arrival of the reflected wave.

[0055] Next, in step S132, the control unit 6 estimates the azimuth of the target in the horizontal direction U by an antenna configuration (horizontal SIMO) of SIMO in the horizontal direction U shown in the upper part of Fig. 5. Specifically, the control unit 6 estimates the azimuth of the target in the horizontal direction U based on the fact that the phase of the received signal received by the antenna elements constituting the SIMO differs depending on the arrival angle of the reflected wave.

[0056] Unlike the MIMO antenna configuration, the SIMO antenna configuration does not have a mismatch between the outgoing and return paths of the radio waves, so there is no false image, which is a problem with the MIMO antenna configuration. SIMO is an abbreviation for Single Input Multi Output.

[0057] Next, in step S133, the control unit 6 selects a signal to be determined as to whether it is a real image or an artificial image from among the spectrum signals Spu ​​detected in one of the horizontal MIMO and horizontal SIMO. For example, the control unit 6 selects a spectrum signal Spu in the horizontal MIMO whose peak level exceeds a predetermined selection threshold as the determination target. The selection threshold is set by experiment or simulation. For example, the selection threshold is set to the minimum value of the peak of the spectrum signal Spu when the signal corresponding to the target is a real image. Note that the control unit 6 may select the spectrum signal Spu to be determined based on the spectrum signal Spu in the horizontal SIMO.

[0058] Next, in step S134, the control unit 6 determines whether or not the peak positions and peak levels of the spectrum signals Spu ​​in the horizontal SIMO and horizontal MIMO are within a predetermined determination region JA. For example, the control unit 6 determines whether or not the spectrum signal Spu in the horizontal SIMO, whose difference in peak levels is equal to or smaller than a predetermined threshold, is present within a predetermined range including the peak position of the spectrum signal Spu in the horizontal MIMO to be determined.

[0059] The predetermined range and the predetermined threshold used in this determination are set by experiments and simulations. The predetermined range is set to, for example, the maximum value between the peak position of the spectrum signal Spu in horizontal SIMO and the peak position of the spectrum signal Spu in horizontal MIMO when the signal corresponding to the target is a real image. The predetermined threshold is set to, for example, the maximum value of the difference between the peak level of the spectrum signal Spu in horizontal SIMO and the peak level of the spectrum signal Spu in horizontal MIMO when the signal corresponding to the target is a real image. The predetermined range may be set to the half-width of the peak of the spectrum signal Spu in horizontal MIMO.

[0060] If the peak position and peak level of the spectrum signal Spu in the horizontal SIMO and horizontal MIMO are within a predetermined judgment region JA, the control unit 6 judges in step S135 that the signal corresponding to the target to be judged is a “real image”.

[0061] On the other hand, if the peak position and peak level of the spectrum signal Spu in the horizontal SIMO and horizontal MIMO are outside the predetermined judgment region JA, the control unit 6 determines in step S136 that the signal corresponding to the target to be judged is a “false image.”

[0062] When there are multiple signals to be determined, such a signal determination process is performed for each of the signals to be determined. When the signal determination process is completed, the control unit 6 proceeds to step S140 in Fig. 7 and executes a vertical direction detection process to detect the direction of the target in the vertical direction V. This vertical direction detection process will be described with reference to Fig. 9.

[0063] 9, in step S141, the control unit 6 estimates the azimuth of the target in the vertical direction V by an antenna configuration (vertical MISO) obtained by MISO in the vertical direction V. The control unit 6 estimates the azimuth of the target in the vertical direction V by using first antenna elements Tx1 to Tx4, Tx6 to Tx8 and second antenna elements Rx1 to Rx4 arranged in the horizontal direction U.

[0064] Here, in Fig. 10, the second antenna elements Rx1 to Rx4 aligned in the horizontal direction U are aligned in the vertical direction V so as to correspond to the first antenna elements Tx1 to Tx4, Tx6 to Tx8 aligned in the vertical direction V. The antenna configuration shown in Fig. 10 includes an MISO antenna configuration in the vertical direction V having seven first antenna elements Tx1 to Tx4, Tx6 to Tx8 and one second antenna element Rx1 to Rx4.

[0065] In such an antenna configuration, when a signal is reproduced according to (1.3) in Fig. 4 at the target's azimuth in the horizontal direction U obtained by the horizontal azimuth detection process, a spectrum signal Spv at the target's azimuth in the vertical direction V is obtained. The control unit 6 of this embodiment obtains the spectrum signal Spv obtained as described above as the target's azimuth by vertical MISO as an estimation result. Note that in an antenna configuration using MISO, unlike an antenna configuration using MIMO, there is no mismatch between the outgoing and return paths of radio waves, and therefore no false images, which are a problem in an antenna configuration using MIMO, are generated.

[0066] Next, in step S142, the control unit 6 estimates the azimuth of the target in the vertical direction V by an antenna configuration (vertical MIMO) obtained by MIMO in the vertical direction V. The control unit 6 estimates the azimuth of the target in the vertical direction V by using first antenna elements Tx1-Tx4, Tx6-Tx8 and two rows of second antenna elements Rx1-Rx4, Rx5-Rx8 aligned in the horizontal direction U.

[0067] Here, in Fig. 11, two rows of second antenna elements Rx1-Rx4, Rx5-Rx8 aligned in a horizontal direction U are aligned in a vertical direction V so as to correspond to the first antenna elements Tx1-Tx4, Tx6-Tx8 aligned in the vertical direction V, respectively. The antenna configuration shown in Fig. 11 includes a MIMO antenna configuration having seven first antenna elements Tx1-Tx4, Tx6-Tx8 and two second antenna elements Rx1-Rx4 in the vertical direction V. In this embodiment, the MIMO antenna configuration shown in Fig. 11 is used as a second virtual array antenna.

[0068] In such an antenna configuration, when a signal is reproduced according to (1.3) in Fig. 4 at the target's azimuth in the horizontal direction U obtained by the horizontal azimuth detection process, a spectrum signal Spv at the target's azimuth in the vertical direction V is obtained. The control unit 6 of this embodiment obtains the spectrum signal Spv obtained as described above as the target's azimuth estimated by vertical MIMO. Note that in an antenna configuration using MIMO, a mismatch occurs between the outbound and return paths of radio waves, and thus a false image occurs due to the path mismatch.

[0069] Next, in step S143, the control unit 6 selects a signal to be determined as to whether it is a real image or an artifact from among the spectrum signals Spv detected in one of the vertical MISO and vertical MIMO. For example, the control unit 6 selects, as the determination target, a spectrum signal Spv in the vertical MIMO whose peak level exceeds a predetermined selection threshold. The selection threshold is set by experiment or simulation. Note that the control unit 6 may be configured to select the spectrum signal Spv to be determined based on the spectrum signal Spv in the vertical MISO.

[0070] Next, in step S144, the control unit 6 determines whether the peak positions and peak levels of the spectrum signals Spv in the vertical MISO and vertical MIMO are within a predetermined judgment region JA. For example, the control unit 6 determines whether the spectrum signal Spv in the vertical MISO, whose peak level difference is equal to or smaller than a predetermined threshold, is present within a predetermined range including the peak position of the spectrum signal Spv in the vertical MIMO to be judged. The predetermined range and the predetermined threshold used for this judgment are set by the same concept as that described in the horizontal azimuth detection process.

[0071] If the peak position and peak level of the spectrum signal Spv in the vertical MISO and vertical MIMO are within a predetermined judgment region JA, the control unit 6 judges in step S145 that the signal corresponding to the target to be judged is a “real image”.

[0072] On the other hand, if the peak position and peak level of the spectrum signal Spv in the vertical MISO and vertical MIMO are outside the predetermined judgment region JA, the control unit 6 determines in step S146 that the signal corresponding to the target to be judged is a “false image.”

[0073] When there are multiple signals to be determined, such signal determination processing is performed for each of the signals to be determined. When the signal determination processing is completed, the control unit 6 proceeds to step S150 in Fig. 7 and detects targets based on the signals identified as real images in the signal determination processing.

[0074] The above is an explanation of the flow of the target detection process. Below, a description will be given of the results of a simulation of detection of the azimuths in the horizontal direction U and vertical direction V of the target, which is the target trg.

[0075] First, a simulation result in the case where there are three targets that serve as targets trg will be described with reference to Figs. 12 to 15. In the simulation of this example, as shown in Fig. 12, the first target trg1 is assumed to be present at approximately the center position (U=0, V=0) in the horizontal direction U and the vertical direction V. In addition, in this example, the second target trg2 is assumed to be present at a position shifted by "0.17" in the horizontal direction U from the first target trg1, and the third target trg3 is assumed to be present at a position shifted by "0.17" in the vertical direction V from the first target trg1. Note that "0.17" is converted to an angle of approximately "10°" as shown in the following formula F3.

[0076] sin(10° / 180°·π)≒0.17 ···(F3) Figure 13 shows the simulation results when estimating the azimuth of a target in the horizontal direction U by horizontal MIMO under the condition that the outgoing path and the return path of the radio wave are aligned. As shown in Figure 13, under the condition that the outgoing path and the return path of the radio wave are aligned, the result was that the peaks of the spectrum signal were detected at the positions corresponding to the first target trg1 and the second target trg2.

[0077] Moreover, Fig. 14 shows the simulation results when the azimuth of a target in the vertical direction V is estimated by reproducing the spectrum signal in the azimuth (U=0.02 in this example) corresponding to the first target trg1 detected in the azimuth estimation in the horizontal direction U. As shown in Fig. 14, under the condition that the outbound and inbound paths of the radio waves are aligned, the spectrum signal peaks were detected at positions corresponding to the first target trg1 and the third target trg3.

[0078] Moreover, Fig. 15 shows the simulation results when the azimuth of a target in the vertical direction V is estimated by reproducing the spectrum signal in the azimuth (U=0.23 in this example) corresponding to the second target trg2 detected in the azimuth estimation in the horizontal direction U. As shown in Fig. 15, under the condition that the outbound and inbound paths of the radio waves are aligned, the result was that a peak of the spectrum signal was detected at the position corresponding to the second target trg2.

[0079] In this way, under conditions where the outbound and inbound radio waves are aligned, it is possible to properly detect the azimuth of a target in the horizontal direction U and vertical direction V using horizontal MIMO and vertical MIMO.

[0080] However, in an actual radar device 1, three types of reflected waves are received: a direct wave, a specular reflected wave, and a reflected wave with a mismatched path, as shown in Fig. 6. The signals of these three types of reflected waves have random phases because they follow different paths.

[0081] In addition, the reflectivity of the target TRG varies, and there may be a weak reflector such as the road surface near a strong reflector such as a car. In such cases, it may not be possible to separate the three types of reflected wave signals, i.e., direct wave, specular reflected wave, and reflected wave with mismatched paths, due to the difference in path distance.

[0082] Fig. 16 shows the results of a simulation of a spectrum signal when a weak reflector exists near a strong reflector, and the signals of three types of reflected waves, namely, a direct wave, a specular reflected wave, and a reflected wave with a mismatched path, cannot be separated by the difference in path distance. In the simulation shown in Fig. 16, the target trg is located at approximately the center position (U=0, V=0), and below it is a specular reflection (U=0, V=-0.17) with a power reflectance of 1 / 10. In this case, the power of the specular reflected wave is 1 / 100 (=1 / 10 x 1 / 10) in a round trip, which is -20 dB smaller than the power of the direct wave. Note that Fig. 16 shows the results when the phase of the signal source of the target trg is random and a certain phase relationship is established.

[0083] As shown in Fig. 16, in the case of vertical MIMO, a position peak corresponding to the target trg is detected. In addition, there is a peak near V = -0.2, but since the power of the specular reflected wave should be -20 dB smaller than the power of the direct wave, this peak is a false image caused by a reflected wave with a mismatched path. Therefore, in the case of vertical MIMO only, the reflected wave with a mismatched path is detected as a real image.

[0084] In contrast, in the vertical MISO, a peak is detected at a position corresponding to the target trg, and no peak is detected at a position corresponding to a reflected wave with a mismatched path. In the radar device 1 of this embodiment, the spectrum signals Spv in the vertical MISO and vertical MIMO are compared to determine whether the signal corresponding to the target is a real image or a false image.

[0085] According to this judgment, the peak at the position relative to the target trg can be determined as a real image, while the peak at the position corresponding to the reflected wave of the path mismatch can be determined as a false image. Note that the reflected power of the specular reflected wave where the outward and return paths of the radio wave match is 1 / 100, which is sufficiently smaller than the reflected power when the outward and return paths of the radio wave do not match. Therefore, the peak at the position corresponding to the specular reflection in the vertical MIMO can be determined to be a false image caused by the path mismatch, not a specular reflected wave where the outward and return paths of the radio wave match.

[0086] The above-described radar device 1 detects the azimuth of a target in the horizontal direction U in the control unit 6 using a first virtual array antenna including a plurality of first antenna elements Tx4, Tx5 and a plurality of second antenna elements Rx1 to Rx4 aligned in the horizontal direction U. The control unit 6 also detects the azimuth of a target in the vertical direction V using a second virtual array antenna including a plurality of first antenna elements Tx1 to Tx4, Tx6 to Tx8 aligned in the vertical direction V and a plurality of second antenna elements Rx1 to Rx4, Rx5 to Rx8 aligned in the vertical direction V. The control unit 6 is configured to determine whether the signals corresponding to the target detected in each of the horizontal direction U and the vertical direction V are real images or false images.

[0087] In this way, if a configuration is adopted in which it is possible to determine whether the signals corresponding to a target detected in each of the horizontal direction U and the vertical direction V are real images or false images, the target orientation can be detected using the signals determined to be real images, thereby suppressing a decrease in the detection accuracy of the target orientation caused by false images.

[0088] Therefore, the radar device 1 of the present disclosure can accurately detect the azimuth of a target in two directions that intersect with each other.

[0089] Moreover, the radar device 1 of this embodiment has the following features.

[0090] (1) The control unit 6 detects the azimuth of a target in the horizontal direction U with an antenna configuration different from the first virtual array antenna, in addition to the first virtual array antenna, and compares the respective detection results to determine whether a signal corresponding to a target detected in the horizontal direction U is a real image or a false image. In this configuration, the output of another sensor such as a camera is not used, and the functional configuration of the radar device 1 determines whether a signal corresponding to a target in the horizontal direction U is a real image or a false image, so that the device configuration can be simplified.

[0091] (2) In addition to the second virtual array antenna, the control unit 6 detects the azimuth of the target in the vertical direction V with an antenna configuration different from the second virtual array antenna, and compares the respective detection results to determine whether the signal corresponding to the target detected in the vertical direction V is a real image or a false image. In this configuration, the output of another sensor such as a camera is not used, and it is determined whether the signal corresponding to the target in the vertical direction V is a real image or a false image by the functional configuration of the radar device 1, so that the device configuration can be simplified.

[0092] (3) In the radar device 1, the second antenna elements Rx1 to Rx4 arranged in the horizontal direction U are arranged at equal intervals at a reference interval (3dh in this example) that is multiple times the predetermined horizontal reference distance dh. The first antenna elements Tx4, Tx5 arranged in the horizontal direction U include elements arranged at an interval (2dh in this example) that is smaller than the reference interval by the horizontal reference distance dh. This makes it possible to reduce the interval between antenna elements in MIMO. In this case, the side lobes in MIMO tend to be small, and erroneous detection of the side lobes as real images is suppressed.

[0093] (4) In the radar device 1, objects to the side of the device, such as guardrails and side walls, act as mirrors and reflect radio waves in the horizontal direction U, which can cause a situation in which the outbound path and the return path of the radio waves do not match in the horizontal direction U. In particular, in the radar device 1 mounted on a vehicle, the road surface acts as a mirror and reflects radio waves in the vertical direction V, which can easily cause a situation in which the outbound path and the return path of the radio waves do not match in the vertical direction V as well. For this reason, it is preferable that the radar device 1, like the device shown in the present disclosure, be configured to determine whether a signal corresponding to a target is a real image or a false image in both the horizontal direction U corresponding to the width direction of the vehicle and the vertical direction V corresponding to the height direction of the vehicle.

[0094] (5) In addition, in the radar device 1 of this embodiment, the first antenna elements Tx4, Tx5 and the second antenna elements Rx1 to Rx4 are arranged so that the antenna aperture length of the horizontal SIMO is larger than half the antenna aperture length of the horizontal MIMO. Such an antenna configuration can be obtained by making the interval between the first antenna elements Tx4, Tx5 smaller than the antenna aperture length of the horizontal SIMO.

[0095] This reduces the difference in resolution between horizontal SIMO and horizontal MIMO, making it possible to suppress a decrease in accuracy in determining whether a real image or a false image is caused by the difference in resolution between horizontal SIMO and horizontal MIMO. As a result, it is possible to appropriately identify whether a signal corresponding to a target is a real image or a false image.

[0096] (Modification of the first embodiment) As in the above embodiment, the second antenna elements Rx1 to Rx4 are preferably arranged at equal intervals with a reference interval that is multiple times the horizontal reference distance dh, but are not limited to this. The second antenna elements Rx1 to Rx4 may be arranged such that at least some of them are unevenly spaced. The first antenna elements Tx4 and Tx5 are preferably arranged at an interval that is smaller than the reference interval by the horizontal reference distance dh, but this is not essential.

[0097] The control unit 6 in the above embodiment compares the detection results of the azimuths in the horizontal SIMO and the horizontal MIMO to determine whether the signal corresponding to the target is a real image or a false image, but is not limited to this. For example, the control unit 6 may compare the detection results of the azimuths in the first virtual array antenna (horizontal MIMO1) and the antenna configuration (horizontal MIMO2) with a higher resolution than the first virtual array antenna to determine whether the signal corresponding to the target is a real image or a false image. This also applies to the following embodiments.

[0098] The control unit 6 in the above embodiment compares the detection results of the azimuths in the vertical MISO and vertical MIMO to determine whether the signal corresponding to the target is a real image or a false image, but is not limited to this. For example, the control unit 6 may compare the detection results of the azimuths in the second virtual array antenna (vertical MIMO1) and an antenna configuration (vertical MIMO2) with a higher resolution than the second virtual array antenna to determine whether the signal corresponding to the target is a real image or a false image.

[0099] Second embodiment Next, a second embodiment will be described with reference to Figures 17 and 18. In this embodiment, differences from the first embodiment will be mainly described.

[0100] In a MIMO antenna configuration, the shape of the peak that appears in a direction where there is no target is not always constant and tends to fluctuate. Therefore, by tracking the peak that appears in a direction where there is no target, it is possible to determine whether the peak is a real image or a false image.

[0101] Therefore, in the vertical orientation detection process, the control unit 6 of this embodiment performs a process of determining whether a signal corresponding to a target in the vertical direction V is a real image or a false image by comparing multiple direction detection results in the vertical direction V.

[0102] Hereinafter, the vertical orientation detection process of this embodiment will be described with reference to Fig. 17. The vertical orientation detection process shown in Fig. 17 is executed after the horizontal orientation detection process described in the first embodiment is executed.

[0103] 17, in step S141A, the control unit 6 tracks the real image signal determined to be a real image in the horizontal direction detection process as a real image direction. Specifically, the control unit 6 tracks the change in the target direction relative to the peak determined to be a real image in the horizontal direction detection process by storing it in memory.

[0104] Here, in an in-vehicle environment, other vehicles, pedestrians, motorbikes, and bicycles basically only move in the horizontal direction U. Therefore, if an accurate target trg can be detected in the horizontal direction U, the target trg can be tracked. The radar device 1 of the present disclosure is configured to be able to determine whether a signal corresponding to a target in the horizontal direction U is a real image or a false image, and therefore, by using this, it becomes possible to track the target trg.

[0105] Next, in step S142A, the control unit 6 estimates the azimuth of the target in the vertical direction V by vertical MIMO. In the process of step S142A, the azimuth of the target in the vertical direction V is estimated using the real image azimuths determined to be real images in the horizontal azimuth detection process multiple times, and the change in the estimated azimuth is stored in the memory. Note that the specific process related to the azimuth estimation in step S142A is substantially the same as the process of step S142 described in the first embodiment, and therefore the description thereof will be omitted.

[0106] Next, in step S143A, the control unit 6 determines whether or not there are N detection results for the azimuth of the target in the vertical direction V. If there are N detection results, the control unit 6 returns to step S141A, and if there are N detection results, the control unit 6 proceeds to step S144A, where "N" is an integer equal to or greater than 2.

[0107] In step S144A, the control unit 6 compares the N detection results in the vertical direction V to determine whether a signal corresponding to a target in the vertical direction V is a real image or a false image. For example, the control unit 6 determines whether the N detection results of the peak positions and peak levels of the spectrum signal Spv in the vertical direction V are within a predetermined range. If the N detection results of the peak positions and peak levels are within the predetermined range, the control unit 6 determines that the image is a real image in step S145A, and if the N detection results of the peak positions and peak levels are outside the predetermined range, the control unit 6 determines that the image is a false image in step S146A.

[0108] FIG. 18 shows the simulation results of spectrum signals when a weak reflector exists near a strong reflector, and the three types of reflected wave signals, i.e., direct wave, specular reflected wave, and reflected wave with mismatched paths, cannot be separated based on the difference in path distance.

[0109] In the simulation shown in FIG. 18, as in the simulation shown in FIG. 16, the target trg is located at approximately the center (U=0, V=0), and below it is a specular reflection (U=0, V=-0.17) with a power reflectivity of 1 / 10. For example, if the relative speed with respect to the target trg is 10 km / h and the orientation of the vertical direction V is detected at time intervals of 0.05 seconds, the distance from the target trg changes by a maximum of 2.8 mm during that time interval (0.05 seconds). This change corresponds to 1 / 2·λ. In addition, since the road surface is not flat like a mirror, the phase due to reflection changes when the reflection position changes slightly. In other words, the phases of the direct wave, specular reflected wave, and reflected wave with a non-matching path change randomly every time the orientation of the vertical direction V is detected.

[0110] In Fig. 18, the results of three simulations are displayed overlapping each other. As shown in Fig. 18, peaks of the spectrum signal are detected at the position corresponding to the target trg and at the position below the target trg. Note that since the power of the specular reflected wave should be -20 dB smaller than the power of the direct wave, the peak below the target trg is an artifact caused by a reflected wave with a mismatched path.

[0111] However, at the position corresponding to the target trg, three peaks of the spectrum signal are detected corresponding to the three simulations, and therefore the peak at the position corresponding to the target trg is determined to be a real image.

[0112] On the other hand, at the position below the target trg, only two spectrum signal peaks are detected corresponding to three simulations, so the peak below the target trg is determined to be a false image caused by a reflected wave with a mismatched path.

[0113] In this way, according to the vertical direction detection process of this embodiment, the peak at the position relative to the target trg can be determined as a real image, while the peak of the false image due to the reflected wave of the path mismatch can be determined as a false image. Note that the reflected power of the specular reflected wave where the outward path and the return path of the radio wave match is 1 / 100, which is sufficiently smaller than the reflected power when the outward path and the return path of the radio wave do not match. Therefore, the peak at the position corresponding to the specular reflection in the vertical MIMO can be determined to be a false image caused by the path mismatch, not a specular reflected wave where the outward path and the return path of the radio wave match.

[0114] The rest is the same as in the first embodiment. The radar device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0115] Moreover, the radar device 1 of this embodiment has the following features.

[0116] (1) The control unit 6 detects the azimuth of the target in the vertical direction V based on the reception result of the reflected wave arriving from the real image azimuth at the second virtual array antenna. Then, the control unit 6 compares the detection results of the azimuth in the vertical direction V multiple times to determine whether the signal corresponding to the target in the vertical direction V is a real image or a false image. This also makes it possible to determine whether the signals corresponding to the target in each of the horizontal direction U and the vertical direction V are real images or false images.

[0117] In particular, in this configuration, since the output of another sensor such as a camera is not used and the functional configuration of the radar device 1 determines whether the signal corresponding to the target in the first direction is a real image or a false image, the device configuration can be realized simply. In addition, this configuration has an advantage that it is possible to avoid erroneous determination due to differences in resolution that may occur when comparing azimuth detection results with different antenna configurations.

[0118] Third embodiment Next, a third embodiment will be described with reference to Figures 19 to 21. In this embodiment, differences from the first embodiment will be mainly described.

[0119] The first virtual array antenna of this embodiment is configured as an extended array antenna including virtual antenna elements interpolated using a differential signal corresponding to the phase difference between multiple antenna elements caused by radio waves arriving from a direction intersecting the arrangement direction of the multiple antenna elements.

[0120] Such an extended array antenna is obtained by interpolating signals at missing antenna locations in an unevenly spaced array obtained by horizontal MIMO using an extension process that uses differential signals corresponding to the phase differences between multiple antenna elements, as shown in Fig. 19. The extension process in this example is Khatri-Rao product extended array processing.

[0121] The matrix shown on the left side of FIG. 20 is the dispersion matrix e between the received signal at the antenna element and the complex conjugate of the received signal for the antenna configuration shown in FIG. iω The matrix shown in the center of Fig. 20 is the dispersion matrix e iω This matrix shows only the exponent parts of the independent components in the matrix. This matrix corresponds to an arrangement in which the numerical values ​​corresponding to the arrangement positions of the antenna elements of the second array antenna are arranged in the top row, and the numerical values ​​corresponding to the arrangement positions of the antenna elements with their signs inverted are arranged in the leftmost column, and these numerical values ​​are added vertically and horizontally. The numerical values ​​(exponents) arranged in the matrix shown in the center of Fig. 20 correspond to each arrangement position in the extended array antenna. The number of tables shown on the right side of Fig. 20 corresponds to the number of signals corresponding to each antenna element.

[0122] The expanded array antenna obtained by such expansion processing has a large aperture antenna configuration with an antenna aperture length of "22d", as shown in the lower part of FIG.

[0123] In the extended array antenna of this embodiment, the antenna elements are arranged so that they are arranged at equal intervals near the center. Specifically, the extended array antenna has 21 antenna elements, and the antenna elements at both ends are arranged at an interval of "2d", and the central antenna elements excluding both ends are arranged at an interval of "1d". In this way, in the extended array antenna of this example, the indexes of the independent components are not consecutive on both ends. For example, the index of the independent component is "-11" after "-9", and there is no "-10". This is a factor that leads to an increase in side lobes, and is likely to occur when the first antenna elements Tx4, Tx5 or the second antenna elements Rx1 to Rx4 are arranged at equal intervals.

[0124] Considering this, in the extension process, the control unit 6 of this embodiment performs weighting by window function processing on signals corresponding to antenna elements constituting the extension array antenna. In this window function processing, for example, the Hann window or Blackman window shown in Fig. 20 can be used. The Hann window has a narrow dynamic range but a high frequency resolution. On the other hand, the Blackman window has a low frequency resolution but a wide dynamic range.

[0125] In addition, in the extended array antenna of this embodiment, the antenna elements are arranged so that the number of signals (number of overlaps) detected at a position close to the median value of the index of the independent components arranged in a matrix is ​​greater than the number of signals detected at a position farthest from the median value. Specifically, in the extended array antenna, as shown on the right side of FIG. 19, multiple signals are obtained at positions where the index of the independent components is "-9", "-8", "-6" to "0" to "6", "8", and "9". In the extended array antenna of this example, when the position where the index of the independent component is "0" is taken as the reference position, the number of signals does not decrease as it moves away from the reference position, but increases and decreases. For example, the number of signals is 8 at the reference position, but decreases to 3 at "-1", increases to 4 at "-2", increases to 6 at "-3", and decreases to 2 at "-4".

[0126] Considering this, when multiple signals corresponding to the antenna elements constituting the extended array antenna are obtained in the extension process, the control unit 6 adds and averages the multiple signals. In other words, when there are multiple numbers corresponding to the arrangement positions in the extended array antenna, the control unit 6 averages the multiple difference signals obtained at the arrangement positions. This suppresses interference between adjacent targets.

[0127] The rest is the same as in the first embodiment. The radar device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0128] Moreover, the radar device 1 of this embodiment has the following features.

[0129] (1) The first virtual array antenna is configured as an extended array antenna including virtual antenna elements that are interpolated using a differential signal corresponding to the phase difference between the multiple antenna elements caused by radio waves arriving from a direction intersecting the arrangement direction of the multiple antenna elements. In this way, by configuring the first virtual array antenna as an extended array antenna, appropriate resolution is ensured by expanding the antenna aperture length, and the occurrence of side lobes that cause false images can be sufficiently suppressed. As a result, it is possible to more appropriately distinguish between real and false images.

[0130] (2) When two targets are treated as targets, interference between the targets may cause a signal with a large peak to appear between the two main lobes corresponding to the real image. Such a signal may affect the results of identifying whether the image is real or false.

[0131] Considering these points, in the radar device 1 of this embodiment, when multiple signals corresponding to the antenna elements constituting the extended array antenna are obtained in the extension process, the multiple signals are averaged. This makes it possible to reduce the influence of interference between the targets trg, so that even when two targets trg, it is possible to properly distinguish whether the image is real or false.

[0132] (3) In the extension process, the radar device 1 performs weighting by window function processing on signals corresponding to antenna elements constituting the extension array antenna. This reduces side lobes that cause false images, so that even when two targets are targeted, it is possible to properly distinguish whether the image is real or false.

[0133] (Modification of the third embodiment) When multiple signals corresponding to antenna elements constituting the extended array antenna are obtained in the extension process, the radar device 1 is preferably configured to average the multiple signals, but is not limited to this. For example, when multiple signals corresponding to antenna elements constituting the extended array antenna are obtained in the extension process, the radar device 1 may be configured to select the maximum or minimum signal from the multiple signals.

[0134] The radar device 1 is preferably configured to weight signals corresponding to antenna elements constituting the extended array antenna by window function processing in the extension processing, but is not limited to this. The radar device 1 may not weight signals corresponding to antenna elements constituting the extended array antenna by window function processing in the extension processing.

[0135] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Fig. 22. In this embodiment, differences from the first embodiment will be mainly described.

[0136] The radar device 1 of this embodiment has eight first antenna elements Tx1 to Tx8 and eight second antenna elements Rx1 to Rx8, but as shown in FIG. 22, the arrangement of the first antenna elements Tx1 to Tx8 is different from that of the first embodiment.

[0137] 22, two first antenna elements Tx1, Tx2 are arranged side by side in the horizontal direction U above the vertical direction V, and two first antenna elements Tx7, Tx8 are arranged side by side in the horizontal direction U below the vertical direction V. Then, four first antenna elements Tx3 to Tx6 are arranged side by side in the horizontal direction U approximately in the center of the vertical direction V.

[0138] The two upper first antenna elements Tx1, Tx2 and the four first antenna elements Tx3 to Tx6 at approximately the center in the vertical direction V are spaced apart by "1dv", which is one time the vertical reference distance dv, in the vertical direction V. Similarly, the two lower first antenna elements Tx7, Tx8 and the four first antenna elements Tx3 to Tx6 at approximately the center in the vertical direction V are spaced apart by "1dv", which is one time the vertical reference distance dv, in the vertical direction V.

[0139] Moreover, the two upper first antenna elements Tx1, Tx2 are spaced apart by a distance equal to the antenna aperture length ("9d" in this example) of the second antenna elements Rx1 to R4 plus a reference distance ("3d" in this example) that is a multiple of the horizontal reference distance dh. Specifically, the two upper first antenna elements Tx1, Tx2 are spaced apart by "12dh", which is 12 times the horizontal reference distance dh in the horizontal direction U.

[0140] Similarly, the two lower first antenna elements Tx7 and Tx8 are arranged at an interval (12dh in this example) obtained by adding a reference interval that is a multiple of the horizontal reference distance dh to the antenna aperture length of the second antenna elements Rx1 to R4.

[0141] The four first antenna elements Tx3 to Tx6 located approximately in the center include those that are arranged at intervals (12dh in this example) that are obtained by adding a reference interval that is a multiple of the horizontal reference distance dh to the antenna aperture length of the second antenna elements Rx1 to R4.

[0142] Specifically, the first antenna elements Tx3 and Tx6 at both ends of the horizontal direction U are spaced apart by an interval (12dh in this example) that is the sum of the antenna aperture length of the second antenna elements Rx1 to R4 and a reference interval that is a multiple of the horizontal reference distance dh. The first antenna elements Tx3 and Tx4 at one end of the horizontal direction U are spaced apart by an interval of "2dh", which is twice the horizontal reference distance dh. The first antenna elements Tx5 and Tx6 at the other end of the horizontal direction U are spaced apart by an interval of "2dh", which is twice the horizontal reference distance dh.

[0143] The rest is the same as in the first embodiment. The radar device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0144] Moreover, the radar device 1 of this embodiment has the following features.

[0145] (1) Among the first antenna elements Tx1 to Tx8, those aligned in the horizontal direction U include those arranged at intervals of a value equal to the antenna aperture length of the second antenna elements Rx1 to Rx4 plus a reference interval. With such an antenna configuration, it becomes easier to arrange virtual antenna elements between real antenna elements in horizontal MIMO. This contributes to suppressing the occurrence of side lobes in horizontal MIMO.

[0146] (Modification of the fourth embodiment) In the fourth embodiment, two first antenna elements Tx1 and Tx2 are arranged on the upper side, and two first antenna elements Tx7 and Tx8 are arranged on the lower side, but the present invention is not limited to this. For example, one first antenna element Tx1 may be arranged on the upper side, and one first antenna element Tx7 may be arranged on the lower side.

[0147] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as described below.

[0148] In the above embodiment, a specific antenna configuration of the radar device 1 is exemplified, but the antenna configuration of the radar device 1 is not limited to the above, and may be an antenna configuration different from the above. The radar device 1 may have an antenna configuration in which the arrangement of the first antenna elements Tx1 to Tx8 and the second antenna elements Rx1 to Rx8 is reversed. In the above embodiment, the two different directions are the horizontal direction U and the vertical direction V, but they may be different directions. It is preferable that one of the first antenna elements Tx1 to Tx8 and the second antenna elements Rx to Rx is arranged at equal intervals with a reference interval that is multiple times a predetermined reference distance, but this is not necessary. It is preferable that the other of the first antenna elements Tx1 to Tx8 and the second antenna elements Rx1 to Rx8 includes an antenna element arranged at an interval smaller than the reference interval by the reference distance, but this is not necessary.

[0149] In the above embodiment, an example has been described in which the radar device 1 of the present disclosure is applied to a target detection device that is mounted on a vehicle and detects various targets present around the vehicle, but the application of the radar device 1 is not limited to this. The radar device 1 can also be applied to, for example, moving objects other than vehicles and stationary devices.

[0150] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is particularly expressly stated that they are essential or where they are clearly considered to be essential in principle.

[0151] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless it is specifically stated as required or unless it is clearly limited to a specific number in principle.

[0152] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., there is no limitation to those shapes, positional relationships, etc., unless specifically stated or in principle limited to a specific shape, positional relationship, etc.

[0153] The control unit and the method of the present disclosure may be implemented in a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. The control unit and the method of the present disclosure may be implemented in a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. The control unit and the method of the present disclosure may be implemented in one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. The computer program may also be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0154] 1. Radar equipment 3 Transmitting antennas 4 Receiving antennas 61 First direction detection unit 62 Second direction detection unit 63 Signal Judgment Unit

Claims

1. A radar device that detects targets using radio waves, A transmitting antenna group (3) including a plurality of first antenna elements arranged side by side in a predetermined first direction and a second direction intersecting the first direction; a receiving antenna group (4) including a plurality of second antenna elements arranged side by side in the first direction and the second direction; a first azimuth detection unit (61) that detects an azimuth of the target in the first direction using a first virtual array antenna including a plurality of the first antenna elements arranged in the first direction and a plurality of the second antenna elements arranged in the first direction; a second azimuth detection unit (62) that detects an azimuth of the target in the second direction using a second virtual array antenna including a plurality of the first antenna elements arranged in the second direction and a plurality of the second antenna elements arranged in the second direction; a signal determination unit (63) that determines whether a signal corresponding to the target detected by each of the first and second direction detection units is a real image or a false image.

2. The first direction detection unit is A first detection unit (611) that detects an azimuth of the target in the first direction by the first virtual array antenna; a second detection unit (612) including the first antenna elements arranged in the first direction and the second antenna elements arranged in the first direction, the second detection unit detecting the azimuth of the target in the first direction with an antenna configuration different from the first virtual array antenna; 2. The radar device according to claim 1, wherein the signal determination unit compares a detection result from the first detection unit with a detection result from the second detection unit to determine whether a signal corresponding to the target in the first direction is a real image or a false image.

3. The second direction detection unit is A third detection unit (621) that detects an azimuth of the target in the second direction by the second virtual array antenna; a fourth detection unit (622) including the first antenna elements arranged in the second direction and the second antenna elements arranged in the second direction and detecting the azimuth of the target in the second direction with an antenna configuration different from the second virtual array antenna; 3. The radar device according to claim 1, wherein the signal determination unit compares a detection result by the third detection unit in the first direction with a detection result by the fourth detection unit to determine whether a signal corresponding to the target in the second direction is a real image or a false image.

4. When the azimuth of the target in the first direction corresponding to the real image signal determined to be a real image by the signal determination unit is defined as a real image azimuth, the second azimuth detection unit detects an azimuth of the target in the second direction based on a reception result of a reflected wave arriving from the real image azimuth at the second virtual array antenna, 3. The radar device according to claim 1, wherein the signal determination unit compares a plurality of detection results from the second azimuth detection unit to determine whether a signal corresponding to the target in the second direction is a real image or a false image.

5. Among the first antenna elements arranged in the first direction and the second antenna elements arranged in the first direction, one antenna element is arranged at equal intervals at a reference interval that is multiple times a predetermined reference distance, 3. The radar device according to claim 1, wherein among the plurality of first antenna elements arranged in the first direction and the plurality of second antenna elements arranged in the first direction, the other antenna element includes one that is arranged at an interval that is smaller than the reference interval by the reference distance.

6. 6. The radar device according to claim 5, wherein the other antenna element includes a plurality of antenna elements arranged at intervals equal to an antenna aperture length of the one antenna element plus the reference interval.

7. 3. The radar device according to claim 1, wherein the first virtual array antenna is configured as an extended array antenna including virtual antenna elements interpolated using a differential signal corresponding to a phase difference between a plurality of antenna elements caused by radio waves arriving from a direction intersecting an arrangement direction of the plurality of antenna elements.

8. It is mounted on a vehicle, the first direction is a horizontal direction corresponding to a width direction of the vehicle, The radar device according to claim 1 , wherein the second direction is a vertical direction corresponding to a height direction of the vehicle.

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