Radar device

Abstract

To provide a radar device that is able to determine whether a signal corresponding to a target is a real image or a false image, while curbing a calculation load required to detect the target.SOLUTION: A radar device 1 includes a transmission antenna group Tx, a reception antenna group Rx, a distance calculation unit 51, a speed calculation unit 52, and an azimuth inference unit 53. The radar device 1 includes a signal determination unit 54 that determines whether a signal corresponding to a target is a real image or a false image. A plurality of first antenna elements and a plurality of second antenna elements are arranged so that some of the multiple antenna elements that receive radio waves in a MIMO antenna virtually overlap. The signal determination unit 54 extracts, as a comparison component, a signal component that changes in accordance with the positional relation between the antenna elements, from distance information and speed information based on the reception signals at the antenna elements that virtually overlap each other in the MIMO antenna; and determines whether the signal corresponding to the target is a real image or a false image, on the basis of the comparison component.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a radar device that detects targets using radio waves. [Background technology]

[0002] In this type of radar device, a technique is known for identifying whether a signal corresponding to a target detected based on radio waves received by multiple antenna elements is a real image or a virtual image (see, for example, Patent Document 1). Patent Document 1 discloses a technique for identifying a virtual image by comparing a target detection result by radio waves transmitted from one antenna element and received by multiple antenna elements with a target detection result by radio waves transmitted from multiple antenna elements and received by multiple antenna elements. In the following, a configuration in which radio waves transmitted from multiple antennas are received by multiple antennas may be referred to as "MIMO" or "MIMO antenna". Also, a configuration in which radio waves transmitted from one antenna are received by multiple antennas may be referred to as "SIMO". Note that MIMO is an abbreviation for Multi Input Multi Output. SIMO is an abbreviation for Single Input Multi Output. MISO is an abbreviation for Multi Input Single Output. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-136232 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, target detection processing including azimuth estimation is performed with each of the SIMO and MINO antenna configurations, and the detection results are compared to identify signals corresponding to targets as false images, which increases the computational load required for target detection. For example, performing azimuth estimation with the SIMO antenna configuration to determine false images increases computational resources.

[0005] An object of the present disclosure is to provide a radar device capable of determining whether a signal corresponding to a target is a real image or a false image while reducing the computational load required for target detection. [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 (Tx) including a plurality of first antenna elements; a receiving antenna group (Rx) including a plurality of second antenna elements; a distance calculation unit (51) that calculates distance information having a correlation with a distance to a target based on a reception signal received by a MIMO antenna using a plurality of first antenna elements and a plurality of second antenna elements; a speed calculation unit (52) that calculates speed information having a correlation with a relative speed with respect to a target based on a reception signal received by a MIMO antenna; an azimuth estimating unit (53) that estimates an azimuth of a target based on a reception result at a plurality of second antenna elements of a reflected wave corresponding to a radio wave transmitted from a plurality of first antenna elements; a signal determination unit (54) that determines whether a signal corresponding to a target obtained based on a reception signal received by the MIMO antenna is a real image or a false image, the first antenna elements and the second antenna elements are arranged such that a portion of the antenna elements receiving radio waves in the MIMO antenna virtually overlaps with another portion of the antenna elements; Before the direction estimation unit estimates the direction of the target, the signal determination unit extracts, as comparison components, signal components that change depending on the positional relationship between the antenna elements from distance information and speed information based on received signals received by each of the virtually overlapping antenna elements in the MIMO antenna, and determines whether the signal corresponding to the target is a real image or a false image based on the comparison result of the comparison signals.

[0007] The distance information and speed information based on the received signals of each of the virtually overlapping antenna elements in the MIMO antenna contain signal components that change depending on the relative positions of the antenna elements. When the signal components are used as comparison signals, if the outbound and inbound paths of the radio waves between the radar device and the target coincide, the comparison components extracted from the distance information and speed information based on the received signals of each of the virtually overlapping antenna elements in the MIMO antenna will be approximately the same.

[0008] On the other hand, when the outgoing and return paths of radio waves between the radar device and the target do not match, the comparison components extracted from the distance information and speed information based on the received signals of each of the virtually overlapping antenna elements in the MIMO antenna will be different. Therefore, by comparing the comparison components extracted from the distance information and speed information based on the received signals received by each of the virtually overlapping antenna elements in the MIMO antenna, it is possible to determine whether the signal corresponding to the target is a real image or a false image.

[0009] In addition, the radar device of the present disclosure determines whether a signal corresponding to a target is a real image or a false image during target detection processing using a MIMO antenna, making azimuth estimation in a SIMO antenna configuration unnecessary. Therefore, the computation load required for target detection can be reduced compared to conventional techniques that require azimuth estimation in a SIMO antenna configuration.

[0010] 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]

[0011] [Figure 1] 1 is a schematic configuration diagram of a radar device according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram for explaining an antenna configuration of the radar device according to the first embodiment. [Diagram 3] 3 is an explanatory diagram for explaining antenna elements that virtually overlap in a MIMO antenna based on the antenna configuration shown in FIG. 2. [Figure 4] 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. [Diagram 5] 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 6] 10 is an explanatory diagram for explaining an example of a distance spectrum obtained by distance FFT executed by a control unit. FIG. [Figure 7] 10 is an explanatory diagram for explaining an example of a velocity spectrum obtained by a velocity FFT executed by a control unit. FIG. [Figure 8] FIG. 4 is an explanatory diagram for explaining an example of an RV map obtained by a control unit. [Figure 9] FIG. 13 is an explanatory diagram for explaining an image corresponding to a target in an RV map. [Figure 10] 10 is an explanatory diagram for explaining the path difference at virtually overlapping antenna elements when the outgoing path and the return path of the radio wave coincide and when the outgoing path and the return path of the radio wave do not coincide. FIG. [Figure 11] FIG. 11 is an explanatory diagram for explaining an antenna configuration of a radar device according to a second embodiment. [Figure 12] FIG. 11 is an explanatory diagram for explaining an antenna configuration of a radar device that is a modified example of the second embodiment. [Figure 13] FIG. 11 is an explanatory diagram for explaining an antenna configuration of a radar device according to a third embodiment. [Figure 14] FIG. 13 is an explanatory diagram for explaining an antenna configuration of a radar device according to a fourth embodiment. [Figure 15]13 is a flowchart showing the flow of a target detection process executed by a control unit of a radar device according to a fourth embodiment. [Figure 16] FIG. 13 is an explanatory diagram for explaining an antenna configuration of a radar device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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.

[0013] (First embodiment) The present embodiment will be described with reference to Figures 1 to 10. 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.

[0014] 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.

[0015] 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.

[0016] 1, the radar device 1 includes a sensor housing (not shown), multiple radar units RU1 and RU2 constituting a radio wave transmission / reception unit, and a control unit 50. In this embodiment, the radar device 1 includes a first radar unit RU1 and a second radar unit RU2, but may include three or more radar units RU.

[0017] The sensor housing is a member that constitutes the outer shell of the radar device 1. The sensor housing includes a first radar unit RU1, a second radar unit RU2, and a control unit 50. Note that the control unit 50 may be provided outside the sensor housing.

[0018] The first radar unit RU1 constitutes a first transceiver 20, and includes a first transmitter 21, an actual first antenna element Tx1, a plurality of actual second antenna elements Rx1 and Rx2, and a first receiver 22. The first radar unit RU1 is implemented on a semiconductor chip such as an MMIC. Note that MMIC is an abbreviation for Monolithic Microwave Integrated Circuit.

[0019] The second radar unit RU2 constitutes a second transceiver unit 30, and includes a second transmitter unit 31, an existing first antenna element Tx2, a plurality of existing second antenna elements Rx3, Rx4, Rx5, and a second receiver unit 32. The second radar unit RU2 is implemented on a semiconductor chip such as an MMIC.

[0020] In this embodiment, the first antenna element Tx1 of the first radar unit RU1 and the first antenna element Tx2 of the second radar unit RU2 constitute a "transmitting antenna group Tx." Additionally, the second antenna elements Rx1 and Rx2 of the first radar unit RU1 and the second antenna elements Rx3, Rx4, and Rx5 of the second radar unit RU2 constitute a "receiving antenna group Rx." Details of the "transmitting antenna group Tx" and the "receiving antenna group Rx" will be described later.

[0021] The first transmitting unit 21 of the first radar unit RU1 generates a signal to be transmitted from the first antenna element Tx1 and transmits the signal to the first antenna element Tx1. Specifically, the first transmitting unit 21 includes a local oscillator 211 that generates a local signal, and transmits the local signal generated by the local oscillator 211 to the first receiving unit 22. The first transmitting unit 21 also generates a chirp signal whose frequency changes continuously, and provides the generated chirp signal to the first antenna element Tx1. Then, the first antenna element Tx1 transmits radio waves corresponding to the chirp signal provided from the first transmitting unit 21 toward the front of the vehicle.

[0022] Furthermore, the first receiving unit 22 generates a beat signal based on the reception signal received by the second antenna element Rx1 and the local signal transmitted from the first transmitting unit 21, samples the beat signal, and provides it to the control unit 50. Although not shown, the first receiving unit 22 is configured to include a mixer, an amplifier, an AD converter, and the like.

[0023] The second transmitting unit 31 of the second radar unit RU2 generates a signal to be transmitted from the first antenna element Tx2 and transmits it to the first antenna element Tx2. The second transmitting unit 31 also generates a chirp signal whose frequency changes continuously and provides the generated chirp signal to the first antenna element Tx2. The first antenna element Tx2 then transmits radio waves corresponding to the chirp signal provided from the second transmitting unit 31 toward the front of the vehicle. The second receiving unit 32 also generates a beat signal based on the reception signals received by the second antenna elements Rx3, Rx4, and Rx5 and the local signal provided from the second transmitting unit 31, samples the beat signal, and provides it to the control unit 50. Although not shown, the second receiving unit 32 is configured to include a mixer, an amplifier, an AD converter, and the like.

[0024] The second transceiver unit 30 of this embodiment is connected to the local oscillator 211 of the first transmitter unit 21, and is provided with a local signal generated by the local oscillator 211. In other words, the first transceiver unit 20 and the second transceiver unit 30 are provided with a local signal generated by the common local oscillator 211.

[0025] Here, the transmitting antenna group Tx and the receiving antenna group Rx of this example will be described with reference to Fig. 2. As shown in Fig. 2, the transmitting antenna group Tx of this example has two actual first antenna elements Tx1 and Tx2. Also, the receiving antenna group Rx of this example has five actual second antenna elements Rx1 to Rx5.

[0026] The two first antenna elements Tx1, Tx2 constituting the transmitting antenna group Tx are arranged side by side in a horizontal direction U when the radar device 1 is mounted on a vehicle. In this embodiment, the horizontal direction U corresponding to the width direction of the vehicle corresponds to the "predetermined direction" and the "predetermined first direction".

[0027] In the transmitting antenna group Tx, two first antenna elements Tx1 and Tx2 are arranged along the horizontal direction U at a predetermined first interval. The first antenna elements Tx1 and Tx2 arranged in the horizontal direction U are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance "dh" (in this example, the first interval = 2dh). The interval between the first antenna elements Tx1 and Tx2 may be a strict 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 Rx5 arranged in the horizontal direction U.

[0028] The horizontal reference distance "dh" 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·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.

[0029] 1 / sin(θfov / 180 π) 2 <dh ···(F1) The first antenna elements Tx1 and Tx2 of this embodiment are arranged at an interval smaller than the interval between the second antenna elements Rx1 to Rx4 by the horizontal reference distance "dh". This arrangement has the advantage that the virtual antenna elements in the MIMO antenna are easily arranged at the horizontal reference distance "dh". This contributes to suppressing the occurrence of side lobes in the MIMO antenna.

[0030] The receiving antenna group Rx receives radio waves and the like transmitted from the transmitting antenna group Tx and reflected by a target. In this example, the receiving antenna group Rx is composed of five actual second antenna elements Rx1 to Rx5. The five second antenna elements Rx1 to Rx5 constituting the receiving antenna group Rx are arranged in a row in the horizontal direction U when the radar device 1 is mounted on a vehicle.

[0031] Of the five second antenna elements Rx1 to Rx5, the four second antenna elements Rx1 to Rx4 at one end of the horizontal direction U are equally spaced apart at "3dh", which is three times the horizontal reference distance "dh". Also, of the five second antenna elements Rx1 to Rx5, the second antenna elements Rx4 and Rx5 at the other end of the horizontal direction U are spaced apart at "2dh", which is twice the predetermined horizontal reference distance "dh". In this way, the receiving antenna group Rx includes the second antenna elements Rx4 and Rx5 that are spaced apart at the same interval as the first interval, which is the arrangement interval of the first antenna elements Tx1 and Tx2.

[0032] Here, the second antenna element Rx5 is added to virtually overlap some of the multiple antenna elements constituting the MIMO antenna described later. The second antenna element Rx5 is arranged at the same interval as the interval between the first antenna elements Tx1 and Tx2 adjacent to each other in the horizontal direction U with respect to the second antenna element Rx4 so that some antenna elements in the MIMO antenna virtually overlap.

[0033] The control unit 50 is an electronic control device mainly composed of a microcomputer having a processor and a memory M. The memory M 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.

[0034] The first radar unit RU1 and the second radar unit RU2 are connected to the control unit 50. The control unit 50 detects a signal corresponding to a target based on radio waves received by the receiving antenna group Rx after a reflected wave corresponding to a radio wave transmitted from the transmitting antenna group Tx.

[0035] Specifically, the control unit 50 obtains a distance spectrum correlating with the distance to the target as distance information based on a signal received by a MIMO antenna using multiple first antenna elements Tx1, Tx2 and multiple second antenna elements Rx1 to Rx5. In this embodiment, the software and hardware of the control unit 50 that obtains the distance information based on radio waves received when radio waves are transmitted and received using the MIMO antenna constitutes the "distance calculation unit 51." The distance spectrum is a frequency spectrum correlating with the distance to the target.

[0036] The control unit 50 also obtains a speed spectrum correlating with the speed of the target as speed information based on the signal received by the MIMO antenna. In this embodiment, the software and hardware of the control unit 50 that obtains the speed information based on the radio waves received when transmitting and receiving radio waves using the MIMO antenna constitutes the "speed calculation unit 52." The speed spectrum is a frequency spectrum correlating with the relative speed with the target.

[0037] Furthermore, the control unit 50 estimates the azimuth of the target based on the reception results of the reflected waves corresponding to the radio waves transmitted from the first antenna elements Tx1, Tx2 at the second antenna elements Rx1 to Rx5. In this embodiment, the software and hardware of the control unit 50 that estimates the azimuth of the target constitutes an "azimuth estimation unit 53."

[0038] Here, we will explain about MIMO antennas. MIMO antennas are virtual array antennas that are generated based on the reception results when radio waves transmitted from multiple antenna elements are received by multiple antenna elements. MIMO antennas are equipped with virtual receiving antennas that are greater than or equal to the number of actual receiving antennas.

[0039] 2, the radar device 1 of this embodiment includes, as actual antenna elements, two first antenna elements Tx1, Tx1 spaced apart by "2dh". The radar device 1 also includes, as actual antenna elements, four second antenna elements Rx1 to Rx4 spaced apart by "3dh", and a second antenna element Rx5 spaced apart by "2dh" from the second antenna element Rx4.

[0040] When the arrival angle of the radio waves with respect to the front direction of the second antenna elements Rx1 to Rx5 is "θ", the path difference between adjacent second antenna elements Rx1 to Rx4 is "3dsinθ", and the path difference between second antenna elements Rx4 and Rx5 is "2dsinθ".

[0041] When the wavelength of the radio wave is λ, the phase difference between adjacent second antenna elements Rx1 to Rx4 is "(2π / λ) 3dsinθ", which is the path difference multiplied by "2π / λ". In addition, the phase difference between second antenna elements Rx4 and Rx5 is "(2π / λ) 2dsinθ". When multiplexing from the two first antenna elements Tx1 and Tx2, the path difference corresponding to the first distance, which is the distance between the two first antenna elements Tx1 and Tx2, is also added.

[0042] As a result, the MIMO antenna of this embodiment is configured as a virtual array antenna having nine virtual antenna elements Vx, as shown in the lower part of Fig. 2. In this embodiment, the second antenna element Rx5 is arranged at a distance from the second antenna element Rx4 that is the same as the first distance, which is the distance between the first antenna elements Tx1 and Tx2.

[0043] The MIMO antenna configured in this way has an antenna configuration in which a part of the virtual antenna element Vx virtually overlaps. Specifically, as shown in Fig. 3, the MIMO antenna has an antenna configuration in which the second antenna element Rx4 that receives the radio wave transmitted from the first antenna element Tx1 and the second antenna element Rx5 that receives the radio wave transmitted from the first antenna element Tx2 virtually overlap.

[0044] Incidentally, a MIMO antenna is premised on the assumption that the outgoing and return paths of radio waves are approximately the same, as shown in the upper part of Fig. 4 for the direct wave and the mirror-image reflected wave. When the outgoing and return paths of radio waves do not match, as shown in the lower part of Fig. 4, a MIMO 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 occur not only when detecting the direction in the horizontal direction U, but also when detecting 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] According to the study by the inventors, the distance information and the speed information based on the received signals of the antenna elements virtually overlapping in the MIMO antenna contain signal components that change depending on the positional relationship of the antenna elements. When the signal components are used as comparison signals, if the outward and return paths of the radio waves between the radar device 1 and the target coincide, the comparison components extracted from the distance information and the speed information based on the received signals of the antenna elements virtually overlapping in the MIMO antenna are substantially the same.

[0046] On the other hand, if the outbound and return paths of the radio waves between the radar device 1 and the target do not coincide, the comparison components extracted from the distance information and speed information based on the received signals of each of the virtually overlapping antenna elements in the MIMO antenna will be different.

[0047] In consideration of these, the radar device 1 extracts comparison components from distance information and speed information based on the received signals received by each of the virtually overlapping antenna elements in the MIMO antenna, and judges whether the signal corresponding to the target is a real image or a false image based on the comparison result of the comparison components. In this embodiment, the software and hardware of the control unit 50 that judges whether the signal corresponding to the target is a real image or a false image constitutes the "signal judgment unit 54."

[0048] Next, the target detection process executed by the control unit 50 of the radar device 1 will be described with reference to Fig. 5. The process shown in Fig. 5 is executed by the control unit 50 periodically or irregularly when chirp signals are transmitted from the transmitting antenna group Tx at a predetermined transmission period.

[0049] 5, in step S100, the control unit 50 receives reflected waves from a target using the receiving antenna group Rx. The received signals are mixed with local signals in the mixers of the receiving units 22 and 32 of the radar units RU1 and RU2. After that, desired frequency components are extracted by a low-pass filter, and the frequency components are provided to the control unit 50 from the receiving units 22 and 32 as beat signals.

[0050] Next, the control unit 50 performs distance FFT processing in step S110. The control unit 50 performs frequency analysis of the beat signal using FFT to obtain a distance spectrum that has a correlation with the distance to the target. The control unit 50 analyzes the signals received by each of the antenna elements that make up the MIMO antenna, and obtains a distance spectrum for each of the antenna elements that make up the MIMO antenna, for example, as shown in Fig. 6. Note that FFT is an abbreviation for Fast Fourier Transform.

[0051] Next, the control unit 50 performs a velocity FFT process in step S120. The control unit 50 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. The control unit 50 analyzes the signals received by each antenna element constituting the MIMO antenna, and obtains a velocity spectrum for each antenna element constituting the MIMO antenna, for example, as shown in FIG.

[0052] Next, in step S130, the control unit 50 uses the distance spectrum and the velocity spectrum to obtain an RV map, which is a two-dimensional image of the position and velocity of the target. For example, as shown in Fig. 8, the control unit 50 obtains an RV map for each antenna element constituting the MIMO antenna. Note that the RV map is a two-dimensional map in which the horizontal axis represents the distance to the target and the vertical axis represents the relative velocity to the target.

[0053] For example, as shown in the upper left of FIG. 4, in case C1 where the outbound and inbound waves are direct waves, the distance to the target is shorter than in cases C2 and C3 where the outbound and inbound paths of the radio waves do not match.

[0054] On the other hand, as shown in the upper right of Figure 4, in route case C4 where both the outbound and inbound paths are mirror-image reflected waves, the distance to the target is longer than in cases C2 and C3 where the outbound and inbound paths of the radio wave do not match.

[0055] For this reason, in an RV map in which reflected waves are mixed where the outbound and inbound radio waves match and where they do not match, three peak components appear corresponding to each of the cases C1, C2, C3, and C4, as shown in Figure 9, for example.

[0056] Next, the control unit 50 judges whether the signal corresponding to the target is a real image or a false image before estimating the azimuth of the target. In step S140, the control unit 50 of this embodiment extracts, as a comparison component, a signal component that changes depending on the positional relationship between antenna elements from distance information and speed information based on the received signals at each of the antenna elements virtually overlapping in the MIMO antenna. For example, a peak component is extracted from the RV map by using CFAR (Constant False Alarm Rate) processing. Then, based on the comparison result of the comparison component, it judges whether the signal corresponding to the target is a real image or a false image.

[0057] Here, the peak components appearing in the RV map are complex signals, and contain phase information, which is one of the signal components that changes depending on the positional relationship between antenna elements. When the peak components appearing in the RV map are obtained for each antenna element, azimuth information at a certain distance and speed, that is, a signal having a phase difference, is obtained.

[0058] In cases where the outbound and return paths are the same, such as direct waves and specularly reflected waves, the phase difference between signals received by virtually overlapping antenna elements in a MIMO antenna is approximately the same. In other words, if there is no path mismatch of radio waves, the phase difference based on the peak components that appear in the RV map will be approximately the same.

[0059] On the other hand, when the outbound and return paths do not match, the phase difference between the signals received by the virtually overlapping antenna elements in the MIMO antenna will be different. In other words, when the radio wave paths do not match, the phase difference based on the peak components that appear in the RV map will be different.

[0060] Taking this into consideration, the control unit 50 uses the phase difference based on the peak component appearing in the RV map as a comparison component, and judges whether the signal corresponding to the target is a real image or a false image based on the comparison result of the comparison component. That is, the control unit 50 performs the false image judgment by comparing the phase difference based on the peak component on the RV map when the radio wave from the first antenna element Tx1 is received by the second antenna element Rx5 with the phase difference based on the peak component on the RV map when the radio wave from the first antenna element Tx2 is received by the second antenna element Rx4.

[0061] Here, the state of radio waves at the first antenna elements Tx1, Tx2 and the second antenna elements Rx4, Rx5 when the mirror image of the target object is in the azimuth of "θ" will be described with reference to FIG.

[0062] As shown on the left side of FIG. 10, in case C4 where the outgoing path and the return path of the radio waves coincide with each other, the phase difference between the signals when the radio waves transmitted from the first antenna elements Tx1 and Tx2 are received by the second antenna element Rx4 is "L / λ 2π."

[0063] The above-mentioned "L" is calculated by the following formula F2. Note that "L" is also the path difference between the signal when the radio wave from the first antenna element Tx1 is received by the second antenna element Rx4 and the signal when it is received by the second antenna element Rx5.

[0064] L=sin(θ / 180·π)·2dh···(F2)

[0065] For example, assume that the signal obtained when the radio wave transmitted from the first antenna element Tx1 is received by the second antenna element Rx4 is used as the reference signal. In this case, in case C4, the phase difference between the signal obtained when the radio wave from the first antenna element Tx1 is received by the second antenna element Rx5 and the reference signal is approximately the same as the phase difference between the signal obtained when the radio wave from the first antenna element Tx2 is received by the second antenna element Rx4 and the reference signal.

[0066] On the other hand, as shown on the right side of Fig. 10, in case C2 where the outgoing path and return path of the radio wave do not match, the phase difference between the signal received by the second antenna element Rx5 from the radio wave transmitted from the first antenna element Tx1 and the reference signal is "L / λ 2π". Also, the phase difference between the signal received by the second antenna element Rx4 from the radio wave transmitted from the first antenna element Tx2 and the reference signal is "0".

[0067] In this way, in case C2, the phase difference is different between when the radio wave transmitted from the first antenna element Tx1 is received by the second antenna element Rx5 and when the radio wave transmitted from the first antenna element Tx2 is received by the second antenna element Rx4. Therefore, in case C2, unlike when the outbound and return paths of the radio wave coincide, the signal components indicating the phase difference contained in the peak components on the RV map based on the signals received by the second antenna elements Rx4 and Rx5 that virtually overlap in the MIMO antenna are different. This is also true in case C3 where the outbound and return paths of the radio wave do not coincide.

[0068] Taking these factors into consideration, the control unit 50 of this embodiment determines whether the signal corresponding to the target is a real image or a false image based on whether the signal components indicating the phase difference contained in the peak components on the RV map based on the received signals at the virtually overlapping second antenna elements Rx4 and Rx5 match.

[0069] Specifically, the control unit 50 determines that the signal corresponding to the target is a real image when the signal components indicating the phase difference contained in the peak components on the RV map based on the received signals at the virtually overlapping second antenna elements Rx4 and Rx5 coincide.

[0070] On the other hand, if the signal components indicating the phase difference contained in the peak components on the RV map based on the received signals at the virtually overlapping second antenna elements Rx4 and Rx5 do not match, the control unit 50 determines in step S150 that the signal corresponding to the target is a false image.

[0071] Note that when the path difference "L" is a multiple of "λ", the phase difference becomes "2π". A phase difference of "2π" cannot be distinguished from a phase difference of "0". For this reason, in cases C2 and C3, the phase difference when the radio wave from the first antenna element Tx1 is received by the second antenna element Rx5 matches the phase difference when the radio wave from the first antenna element Tx2 is received by the second antenna element Rx4, making it impossible to properly judge false images.

[0072] For example, if the horizontal reference distance "dh" is "3 / 2·λ" and the distance between the second antenna elements Rx4 and R5 is "dh", then "θ≒42°" and "L" is "λ", and the phase difference when the radio wave from the first antenna element Tx1 is received by the second antenna element Rx5 is "2π", which is the same as "0". In addition, the phase difference when the radio wave from the first antenna element Tx2 is received by the second antenna element Rx4 is also "0". In this way, the phase difference when the radio wave from the first antenna element Tx1 is received by the second antenna element Rx5 and the phase difference when the radio wave from the first antenna element Tx2 is received by the second antenna element Rx4 may be the same.

[0073] The larger the horizontal reference distance "dh", the greater the number of cases where the path difference "L" is a multiple of "λ", so it is desirable for the horizontal reference distance "dh" to be a value close to "1 / 2·λ" or "1 / 2·λ". Also, the greater the spacing between the virtually overlapping second antenna elements Rx4 and R5, the greater the number of cases where the path difference "L" is a multiple of "λ", so it is desirable for the spacing between the virtually overlapping second antenna elements Rx4 and R5 to be small.

[0074] In this embodiment, taking the above-mentioned matters into consideration, the distance between the virtually overlapping second antenna elements Rx4 and R5 is set to be the distance (i.e., the minimum distance) that is the minimum distance between the first antenna elements Tx1 and Tx2 adjacent to each other in the horizontal direction U.

[0075] In this manner, the control unit 50 performs the process of determining whether the signal corresponding to the target is a real image or a false image. Next, in step S160, the control unit 50 selects signals to be used for estimating the azimuth of the target. From among the signals determined to be real images, the control unit 50 selects a number of signals equal to or less than a predetermined upper limit number as signals to be used for estimating the azimuth of the target. The upper limit number is determined according to the signal processing capability of the control unit 50, etc.

[0076] Here, estimating the target direction based on the signal determined to be a false image in step S150 does not contribute to target detection, and instead increases the computation load required for target detection. For this reason, the control unit 50 of this embodiment selects signals to be used for target direction estimation from among the signals excluding the signals determined to be false images.

[0077] Next, in step S170, the control unit 50 estimates the azimuth of the target based on the signal determined to be a real image. Specifically, the control unit 50 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 MIMO antenna differs depending on the arrival angle of the reflected wave.

[0078] Next, in step S180, the control unit 50 detects a target object based on the distance spectrum correlating with the distance to the target obtained so far, the speed spectrum correlating with the speed of the target, and the azimuth of the target.

[0079] The above-described radar device 1 extracts, as a comparison component, a signal component that changes according to the positional relationship between antenna elements from distance information and speed information based on the received signals received by each of the virtually overlapping antenna elements in the MIMO antenna, and then compares the comparison components to determine whether the signal corresponding to the target is a real image or a false image.

[0080] Furthermore, the radar device 1 determines whether a signal corresponding to a target is a real image or a false image during target detection processing using a MIMO antenna, so direction estimation in a SIMO antenna configuration is not required.

[0081] Therefore, the computation load required for target detection can be reduced compared to the conventional technology that requires azimuth estimation using a SIMO antenna configuration. That is, the radar device 1 of this embodiment can determine whether a signal corresponding to a target is a real image or a false image while reducing the computation load required for target detection.

[0082] Moreover, the radar device 1 of this embodiment has the following features.

[0083] (1) In the radar device 1 of this embodiment, the azimuth estimation unit 53 estimates the azimuth of a target based on a signal determined to be a real image by the signal determination unit 54. In this way, if the radar device 1 is configured to estimate the azimuth of a target based on a signal determined to be a real image, unnecessary azimuth estimation is suppressed compared to a configuration in which the azimuth of a target is estimated including a signal determined to be a false image. This contributes to suppressing the calculation load required for target detection.

[0084] (2) Specifically, the transmitting antenna group Tx includes first antenna elements Tx1, Tx2 arranged at a first interval in a predetermined direction. The receiving antenna group Rx includes second antenna elements Rx1 to Rx4 arranged at an interval different from the first interval in the predetermined direction, as well as a second antenna element Rx5 arranged at a first interval in the predetermined direction. In this way, if an antenna configuration is adopted in which the interval between the first antenna elements Tx1, Tx2 and the interval between the second antenna elements Rx4, Rx5 are partially the same, a MIMO antenna in which multiple antenna elements virtually overlap can be realized.

[0085] (3) In the radar device 1 of this embodiment, the above-mentioned first interval is set to the minimum interval between the first antenna elements Tx1, Tx2 adjacent to each other in a predetermined direction. This makes it difficult for comparison components extracted from distance information and speed information based on the received signals of the virtually overlapping antenna elements to match when the outbound and inbound paths of radio waves do not match, making it possible to appropriately determine whether a signal corresponding to a target is a real image or a false image.

[0086] (4) The radar device 1 includes a plurality of transceivers 20, 30, each including first antenna elements Tx1, Tx2 and second antenna elements Rx1 to Rx5. The radar device 1 is configured such that a local signal generated by a common local oscillator 211 is supplied to the plurality of transceivers 20, 30. This makes it possible to suppress phase shifts in the signals received by the antenna elements, which are caused by different local oscillators 211. This not only contributes to detection of targets, but also to improved accuracy in determining whether a signal corresponding to a target is a real image or a false image.

[0087] Second embodiment Next, a second embodiment will be described with reference to Fig. 11. In this embodiment, differences from the first embodiment will be mainly described.

[0088] As shown in the upper part of FIG. 11, the transmitting antenna group Tx of this embodiment includes four first antenna elements Tx1 to Tx4 arranged in the horizontal direction U.

[0089] The first antenna elements Tx1 and Tx2 on one side of the horizontal direction U and the first antenna elements Tx3 and Tx4 on the other side of the horizontal direction U are arranged at a first interval in the horizontal direction U. Specifically, the first antenna elements Tx1 and Tx2 on one side of the horizontal direction U are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance "dh", as in the first embodiment (in this example, the first interval = 2dh). The first antenna elements Tx3 and Tx4 on the other side of the horizontal direction U, which have been added this time, are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance "dh", as in the first antenna elements Tx1 and Tx2. The first antenna elements Tx2 and Tx3 in the center of the horizontal direction U are arranged at an interval shorter than the antenna aperture length "9dh" of the receiving antenna group Rx by the horizontal reference distance "dh". The first antenna elements Tx2 and Tx3 of this embodiment are arranged at an interval of "8dh", which is eight times the predetermined horizontal reference distance "dh".

[0090] Moreover, the receiving antenna group Rx of this embodiment includes five second antenna elements Rx1 to Tx5 arranged in the horizontal direction U. The receiving antenna group Rx is similar to that of the first embodiment, and therefore a description thereof will be omitted.

[0091] A MIMO antenna based on such an antenna configuration is configured as a virtual array antenna having 16 virtual antenna elements Vx, as shown in the lower part of Fig. 11. In the receiving antenna group Rx of this embodiment, some of the second antenna elements Tx1 to Tx5 are arranged at a first interval. Therefore, the MIMO antenna of this embodiment has an antenna configuration in which some of the virtual antenna elements Vx virtually overlap, similar to the first embodiment.

[0092] 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.

[0093] Moreover, the radar device 1 of this embodiment has the following features.

[0094] (1) The radar device 1 of this embodiment includes first antenna elements Tx2 and Tx3 that are arranged at an interval shorter than the antenna aperture length of the receiving antenna group Rx, which is "9dh", by the horizontal reference distance "dh". This makes it easier for the interval between virtual antenna elements in the MIMO antenna to be the horizontal reference distance "dh". This contributes to suppressing the occurrence of side lobes in the MIMO antenna.

[0095] (Modification of the second embodiment) In the second embodiment, in order to arrange some of the virtual antenna elements in the MIMO antenna so as to overlap, a second antenna element Rx5 is added that is arranged at a minimum distance from the second antenna element Rx4 to the first antenna elements Tx1 to Tx4, but this is not limited to this.

[0096] 12, the radar device 1 may be configured such that the second antenna element Rx5 is eliminated and the interval between the first antenna elements Tx2, Tx3 located in the center of the horizontal direction U is set to "9dh", which is the antenna aperture length of the receiving antenna group Rx. In this example, the interval between the first antenna elements Tx2, Tx3 located in the center of the horizontal direction U will be described as the "first interval".

[0097] The MIMO antenna of this modification is configured as a virtual array antenna having 15 virtual antenna elements Vx, as shown in the lower part of Fig. 12. In addition, in the receiving antenna group Rx, some of the second antenna elements Tx1 to Tx5 are arranged at a first interval. Therefore, in a configuration with fewer antenna elements than the second embodiment, an antenna configuration in which some of the virtual antenna elements Vx virtually overlap can be obtained.

[0098] Third embodiment Next, a third embodiment will be described with reference to Fig. 13. In this embodiment, differences from the second embodiment will be mainly described.

[0099] The radar device 1 of this embodiment does not include the second antenna element Rx5 of the receiving antenna group Rx, and instead adds a first antenna element Tx5 to the transmitting antenna group Tx.

[0100] As shown in the upper part of FIG. 13, the transmitting antenna group Tx of this embodiment includes five first antenna elements Tx1 to Tx5 arranged in the horizontal direction U.

[0101] The four first antenna elements Tx1 to Tx4 on one side of the horizontal direction U are spaced apart at intervals similar to those in the first embodiment. The newly added first antenna element Tx5 on the other end of the horizontal direction U is spaced apart at a first interval from the adjacent first antenna element Tx4. In this embodiment, the first interval is set to the minimum interval (3dh in this example) between adjacent second antenna elements Rx1 to R4.

[0102] The receiving antenna group Rx of this embodiment includes four second antenna elements Rx1 to Rx4 aligned in the horizontal direction U. The four second antenna elements Rx1 to Rx4 are equally spaced apart at "3dh", which is three times the horizontal reference distance "dh".

[0103] A MIMO antenna based on such an antenna configuration is configured as a virtual array antenna including a large number of virtual antenna elements Vx, as shown in the lower part of Fig. 13. In the receiving antenna group Rx, some of the second antenna elements Tx1 to Tx4 are arranged at a first interval in the horizontal direction U. The MIMO antenna of this embodiment has an antenna configuration in which some of the virtual antenna elements Vx virtually overlap, similar to the second embodiment.

[0104] 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.

[0105] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Figures 14 and 15. In this embodiment, differences from the first embodiment will be mainly described.

[0106] As shown in the upper part of Fig. 14, the transmitting antenna group Tx has six actual first antenna elements Tx1 to Tx6. The six first antenna elements Tx1 to Tx6 constituting the transmitting antenna group Tx 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. 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".

[0107] In the transmitting antenna group Tx, three first antenna elements Tx1, Tx2, and Tx6 are arranged along the vertical direction V at a predetermined interval. The first antenna elements Tx1, Tx2, and Tx6 arranged in the vertical direction V are arranged at an interval of "dv", which is one time the predetermined vertical reference distance "dv". The first antenna elements Tx1 and Tx6 at both ends of the vertical direction V are arranged at an interval of "2dv", which is twice the vertical reference distance "dv". In this embodiment, the "second interval" is the interval between the first antenna elements Tx1 and Tx6 at both ends of the vertical direction V (2dv in this example). Note that the intervals between the first antenna elements Tx1, Tx2, and Tx6 may be strictly multiples of the vertical reference distance "dv", or may include an error that is generally permitted 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 aligned in the vertical direction V.

[0108] The vertical reference distance "dv" in this example is set so as to satisfy the following formula F3 when the detection range of the radar device 1 is "±1 / 2·φfov". In this embodiment, φfov is set to "40°", and the vertical reference distance "dv" is set to "1 / 2·λ", where λ is the wavelength of the radio wave.

[0109] 1 / sin(φfov / 180 π) 2 <dv ···(F3) In addition, in the transmitting antenna group Tx, four first antenna elements Tx2 to Tx5 are arranged substantially in the center in the vertical direction V along the horizontal direction U at predetermined intervals.

[0110] The first antenna elements Tx2 and Tx3 on one side of the horizontal direction U and the first antenna elements Tx4 and Tx5 on the other side of the horizontal direction U are arranged at a predetermined first interval. Specifically, the first antenna elements Tx2 and Tx3 on one side of the horizontal direction U are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance "dh". The first antenna elements Tx4 and Tx5 on the other side of the horizontal direction U are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance "dh". The first antenna elements Tx3 and Tx4 in the center of the horizontal direction U are arranged at an interval equal to "9dh", which is the antenna aperture length of the receiving antenna group Rx. The first antenna elements Tx3 and Tx4 of this embodiment are arranged at an interval of "9dh", which is nine times the predetermined horizontal reference distance "dh".

[0111] Moreover, the receiving antenna group Rx in this embodiment is composed of eight actually existing second antenna elements Rx1 to Rx8. The eight second antenna elements Rx1 to Rx8 constituting the receiving antenna group Rx 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.

[0112] Specifically, the receiving antenna group Rx includes four second antenna elements Rx1 to Rx4 aligned along the horizontal direction U at a position close to a first antenna element Tx1 which is one end of the transmitting antenna group Tx in the vertical direction V. The receiving antenna group Rx also includes four second antenna elements Rx5 to Rx8 aligned along the horizontal direction U at a position close to a first antenna element Tx6 which is the other end of the transmitting antenna group Tx 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 "3dh", which is three times the horizontal reference distance "dh".

[0113] Additionally, 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 "2dv", which is twice the vertical reference distance "dv".

[0114] In the radar device 1 of this embodiment, the spacing between the second antenna elements Rx1 to Rx8 arranged in the vertical direction V is the same as the second spacing ("2dv" in this example), which is the spacing between the first antenna elements Tx1, Tx6 at both ends of the vertical direction V.

[0115] In addition, in the radar device 1 of this embodiment, the distance between the second antenna elements Rx1, Rx4, R5, and Rx8 at both ends of the horizontal direction U is the same as the first distance (in this example, "9dh"), which is the distance between the first antenna elements Tx3 and Tx4 at the center of the horizontal direction U.

[0116] A MIMO antenna based on such an antenna configuration is configured as a virtual array antenna in which a large number of virtual antenna elements Vx are arranged in both the horizontal direction U and the vertical direction V, as shown in the lower part of FIG.

[0117] The MIMO antenna of this embodiment includes a first MIMO antenna generated in a horizontal direction U and a second MIMO antenna generated in a vertical direction V. The first MIMO antenna is a virtual array antenna using a plurality of first antenna elements Tx2 to Tx5 aligned in the horizontal direction U and a plurality of second antenna elements Rx1 to Rx8 aligned in the horizontal direction U. The second MIMO antenna is a virtual array antenna using a plurality of first antenna elements Tx1, Tx2, Tx6 aligned in the vertical direction V and a plurality of second antenna elements Rx1 to Rx8 aligned in the vertical direction V.

[0118] In the receiving antenna group Rx of this embodiment, some of the second antenna elements Tx1 to Tx8 are arranged at a first interval in the horizontal direction U, and at a second interval in the vertical direction V. Therefore, the MIMO antenna of this embodiment has an antenna configuration in which some of the virtual antenna elements Vx virtually overlap. For example, the first MIMO antenna generated in the horizontal direction U has an antenna configuration in which, of the virtual antenna elements Vx, the antenna element Vx1 located at approximately the center in the horizontal direction U virtually overlaps. Moreover, the second MIMO antenna generated in the vertical direction V has an antenna configuration in which, of the virtual antenna elements Vx, the antenna element Vx2 located at approximately the center in the vertical direction V virtually overlaps.

[0119] Next, the target detection process executed by the control unit 50 of the radar device 1 will be described with reference to Fig. 15. The process shown in Fig. 15 is executed by the control unit 50 periodically or irregularly when chirp signals are transmitted from the transmitting antenna group Tx at a predetermined transmission period.

[0120] 15, in step S100A, the control unit 50 receives reflected waves from a target using the receiving antenna group Rx. The received signals are provided to the control unit 50 from the receiving units 22 and 32.

[0121] Next, the control unit 50 performs distance FFT processing in step S110A. The control unit 50 obtains distance spectra as distance information for each of the antenna elements constituting the first MIMO antenna and the second MIMO antenna.

[0122] Next, the control unit 50 performs a rate FFT process in step S120A. The control unit 50 obtains a rate spectrum as rate information for each antenna element constituting the first MIMO antenna and the second MIMO antenna.

[0123] Next, in step S130A, the control unit 50 obtains an RV map of the position and velocity of the target in the horizontal direction U and an RV map of the position and velocity of the target in the vertical direction V, using the distance spectrum and the velocity spectrum.

[0124] Next, in step S140A, the control unit 50 uses the phase difference based on the peak components on the RV map corresponding to the antenna elements virtually overlapping in the horizontal direction U as a comparison component, and determines whether the signal corresponding to the target is a real image or a false image based on the comparison result of the comparison component. Specifically, the control unit 50 performs the false image determination by comparing the phase difference based on the peak components on the RV map corresponding to the position indicated by "Vx1" in Fig. 14.

[0125] Furthermore, in step S145A, the control unit 50 uses the phase difference based on the peak components on the RV map corresponding to the antenna elements virtually overlapping in the vertical direction V as a comparison component, and determines whether the signal corresponding to the target is a real image or a false image based on the comparison result of the comparison component. Specifically, the control unit 50 performs the false image determination by comparing the phase difference based on the peak components on the RV map corresponding to the position shown by "Vx2" in Fig. 14.

[0126] Next, in the control unit 50, if the phase differences based on the peak components on the RV map based on the received signals at virtually overlapping antenna elements do not match, in step S150A, it is determined that the signal corresponding to the target is a false image.

[0127] Next, in step S160A, the control unit 50 selects a signal to be used for estimating the azimuth of the target. The control unit 50 selects a signal to be used for estimating the azimuth of the target from among the signals excluding the signals determined to be false images.

[0128] Next, in step S170A, the control unit 50 estimates the azimuth of the target based on the signal determined to be a real image. Specifically, the control unit 50 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 MIMO antenna differs depending on the arrival angle of the reflected wave. Also, the control unit 50 estimates the azimuth of the target in the vertical direction V based on the fact that the phase of the received signal received by the antenna elements constituting the second MIMO antenna differs depending on the arrival angle of the reflected wave.

[0129] Next, in step S180A, control unit 50 detects a target object based on the distance spectrum correlated with the distance to the target obtained so far, the speed spectrum correlated with the speed of the target, and the azimuth of the target.

[0130] 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.

[0131] Moreover, the radar device 1 of this embodiment has the following features.

[0132] (1) The radar device 1 obtains distance information and speed information based on the received signals received by each of the virtually overlapping antenna elements in the first MIMO antenna. Then, from the distance information and speed information corresponding to each of the virtually overlapping antenna elements, a signal component that changes depending on the positional relationship between the antenna elements is extracted as a comparison component. Then, based on the comparison result of the comparison component, it is determined whether the signal corresponding to the target based on the received signal received by the first MIMO antenna is a real image or a false image. In addition, the radar device 1 obtains distance information and speed information based on the received signal received by each of the virtually overlapping antenna elements in the second MIMO antenna. Then, from the distance information and speed information corresponding to each of the virtually overlapping antenna elements, a signal component that changes depending on the positional relationship between the antenna elements is extracted as a comparison component. Then, based on the comparison result of the comparison component, it is determined whether the signal corresponding to the target based on the received signal received by the second MIMO antenna is a real image or a false image. This makes it possible to determine whether the signals corresponding to the target in two different directions are real images or false images while suppressing the computational load required for target detection.

[0133] (2) The transmitting antenna group Tx includes first antenna elements Tx3, Tx4 arranged at a first interval in the horizontal direction U, while the receiving antenna group Rx also includes second antenna elements Rx1, Rx4, Rx5, Rx8 arranged at a first interval in the horizontal direction U. In addition, the transmitting antenna group Tx includes first antenna elements Tx1, Tx2, Tx6 arranged at a second interval in the vertical direction V, while the receiving antenna group Rx also includes second antenna elements Rx1 to Rx8 arranged at a second interval in the vertical direction V.

[0134] In this way, the radar device 1 of this embodiment has an antenna configuration in which the intervals between the first antenna elements Tx1 to Tx6 and the intervals between the second antenna elements Rx1 to Rx8 are partially the same in both the horizontal direction U and the vertical direction V. This makes it possible to realize a MIMO antenna in which multiple antenna elements virtually overlap in both the horizontal direction U and the vertical direction V.

[0135] Fifth embodiment Next, a fifth embodiment will be described with reference to Fig. 16. In this embodiment, differences from the fourth embodiment will be mainly described.

[0136] 16, the transmitting antenna group Tx has eight actual first antenna elements Tx1 to Tx8. The eight first antenna elements Tx1 to Tx8 constituting the transmitting antenna group Tx are arranged side by side in both the horizontal direction U and the vertical direction V when the radar device 1 is mounted on a vehicle.

[0137] In the transmitting antenna group Tx, three first antenna elements Tx1, Tx3, and Tx7 are arranged at a predetermined second interval in the vertical direction V. The first antenna elements Tx1, Tx3, and Tx7 arranged in the vertical direction V are arranged at an interval of "dv" that is one time the predetermined vertical reference distance "dv". The intervals between the first antenna elements Tx1, Tx3, and Tx7 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.

[0138] In addition, the transmitting antenna group Tx has four first antenna elements Tx3 to Tx6 located approximately in the center of the vertical direction V, which are arranged in the horizontal direction U at a predetermined interval. The first antenna elements Tx3 and Tx4 on one side of the horizontal direction U and the first antenna elements Tx5 and Tx6 on the other side of the horizontal direction U are arranged at a predetermined first interval in the horizontal direction U. Specifically, the first antenna elements Tx3 and Tx4 on one side of the horizontal direction U are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance "dh". The first antenna elements Tx5 and Tx6 on the other side of the horizontal direction U are arranged at an interval of "2dh", which is twice the predetermined horizontal reference distance "dh". The first antenna elements Tx4 and Tx5 in the center of the horizontal direction U are arranged at an interval smaller than the horizontal reference distance, "9dh", which is the antenna aperture length of the receiving antenna group Rx. The first antenna elements Tx4 and Tx5 of this embodiment are arranged at an interval of "8dh", which is eight times the predetermined horizontal reference distance "dh".

[0139] The receiving antenna group Rx is composed of nine actual second antenna elements Rx1 to R9. The nine second antenna elements Rx1 to Rx9 constituting the receiving antenna group Rx 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.

[0140] Specifically, the receiving antenna group Rx includes four second antenna elements Rx1 to Rx4 aligned along the horizontal direction U at positions close to a first antenna element Tx1 that is one end of the transmitting antenna group Tx in the vertical direction V. The receiving antenna group Rx also includes four second antenna elements Rx5 to Rx8 aligned along the horizontal direction U at positions close to a first antenna element Tx7 that is the other end of the transmitting antenna group Tx in the vertical direction V.

[0141] The second antenna elements Rx1 to Rx4 in the first row and the second antenna elements Rx5 to Rx8 in the second row are spaced apart by "3dh", which is three times the horizontal reference distance "dh". The second antenna elements Rx1 and Rx5 in the first row are spaced apart by "3 / 2·dv", which is 3 / 2 times the horizontal reference distance "dh", from the first antenna elements Tx1, Tx3, and Tx7 on one side of the horizontal direction U in the transmitting antenna group Tx. Similarly, the second antenna elements Rx4 and Rx8 in the fourth row are spaced apart by "3 / 2·dv", which is 3 / 2 times the horizontal reference distance "dh", from the first antenna elements Tx2, Tx6, and Tx8 on the other side of the horizontal direction U in the transmitting antenna group Tx.

[0142] 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 "3dv", which is three times the vertical reference distance "dv". The second antenna elements Rx1 to Rx4 in the second 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 Tx 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 Tx7, which is the other end of the transmitting antenna group Tx in the vertical direction V.

[0143] In addition, the receiving antenna group Rx includes a second antenna element Rx9 that is arranged at a first interval in the horizontal direction and a second interval in the vertical direction relative to some of the antenna elements in the receiving antenna group Rx (in this example, the second antenna element Rx2). The second antenna element Rx9 is arranged with a minimum interval (2dh in this example) between the adjacent second antenna element Rx2 and the first antenna elements Tx1 to Tx8 aligned in the horizontal direction U. The second antenna element Rx9 is also arranged with a minimum interval (dv in this example) between the adjacent second antenna element Rx2 and the first antenna elements Tx1 to Tx8 aligned in the vertical direction V.

[0144] In this embodiment, the smallest interval among the first antenna elements Tx1 to Tx8 aligned in the horizontal direction U corresponds to the "first minimum interval", and the smallest interval among the first antenna elements Tx1 to Tx8 aligned in the vertical direction V corresponds to the "second minimum interval". In this example, the "first interval" becomes the "first minimum interval", and the "second interval" becomes the "second minimum interval".

[0145] A MIMO antenna based on such an antenna configuration is configured as a virtual array antenna (that is, a first MIMO antenna and a second MIMO antenna) in which a large number of virtual antenna elements Vx are arranged in both the horizontal direction U and the vertical direction V.

[0146] 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.

[0147] Moreover, the radar device 1 of this embodiment has the following features.

[0148] (1) The transmitting antenna group Tx includes first antenna elements Tx3 to Tx6 that are arranged at a first interval in the horizontal direction U, and first antenna elements Tx1 to Tx3 and Tx6 to Tx8 that are arranged at a second interval in the vertical direction V. The receiving antenna group also includes second antenna elements Rx2 and Rx5 that are arranged at a first interval in the horizontal direction U, and at a second interval in the vertical direction V. With this antenna configuration, it is possible to realize a MIMO antenna in which multiple antenna elements partially virtually overlap.

[0149] (2) In addition, in the radar device 1, the above-mentioned first interval is set to the minimum interval between the first antenna elements Tx3 to Tx6 adjacent to each other in the horizontal direction U, and the second interval is set to the minimum interval between the first antenna elements Tx1 to Tx3 and Tx6 to Tx8 adjacent to each other in the vertical direction V. With this, when the outbound path and the inbound path of the radio wave do not match, the comparison components extracted from the distance information and the speed information based on the received signals of the virtually overlapping antenna elements are unlikely to match, so it is possible to appropriately determine whether the signal corresponding to the target is a real image or a false image.

[0150] (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.

[0151] 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 Rx1 to Rx9 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.

[0152] In the above embodiment, in the false image determination, the phase difference included in the peak component on the RV map generated based on the received signals at each of the virtually overlapping antenna elements is extracted as the comparison component, but the present invention is not limited to this. The radar device 1 may be configured to extract, as the comparison component, a signal component that changes depending on the positional relationship between the antenna elements from distance information and speed information based on the received signals received at each of the virtually overlapping antenna elements by a method different from the above.

[0153] In the first, third and fifth embodiments, at least one of the first and second antenna elements that actually exist is added so that the antenna elements virtually overlap in the MIMO antenna.

[0154] The added antenna elements can be set at any position as long as the antenna elements virtually overlap in the MIMO antenna. However, if it is desired to increase the resolution of the MIMO antenna, it is desirable to place the added antenna elements at the ends of the horizontal direction U or the vertical direction V. Also, if it is desired to prevent the sensor housing from becoming too large, it is desirable to place the added antenna elements at any position other than the ends of the horizontal direction U or the vertical direction V.

[0155] The additional antenna elements are used to determine whether a signal corresponding to a target is a real image or a false image, but since they are not essential for estimating the target's azimuth, they do not have to be used to estimate the target's azimuth.

[0156] As in the above embodiment, the radar device 1 is preferably configured to estimate the azimuth of the target based on the signal determined to be a real image, but is not limited to this. For example, the radar device 1 may estimate the azimuth of the target using a part of the signal determined to be a false image in addition to the signal determined to be a real image.

[0157] Here, as explained in the first embodiment, when the path difference "L" is a multiple of "λ", the phases of the signals received by the virtually overlapping antenna elements are aligned, making it impossible to perform appropriate false image detection. Considering this, it is desirable for the radar device 1 to perform false image detection based on a signal received when the condition that the path difference "L" is a multiple of "λ" is not met, for example.

[0158] The radar device 1 of the above-described embodiment is configured such that the local oscillator 211 provided in the first transmitter 21 is connected to the second transmitter 31 and the second receiver 32, but is not limited thereto. The radar device 1 may be configured such that the local oscillator provided in the second transmitter 31 is connected to the first transmitter 21 and the first receiver 22. The radar device 1 may be configured such that local oscillators provided outside the radar units RU1 and RU2 are connected to the transmitters 21 and 31 and the receivers 22 and 32. It is preferable that the radar device 1 is configured such that a local signal generated by a common local oscillator 211 is supplied to the multiple transmitters and receivers 20 and 30, but is not limited thereto. The radar device 1 may be configured such that a local signal generated by a different local oscillator is supplied to the transmitters and receivers 20 and 30.

[0159] The radar device 1 of the above-described embodiment is configured to include a first transceiver unit 20 and a second transceiver unit 30 (e.g., a configuration including multiple ICs), but is not limited thereto and may also be configured to include a single transceiver unit (e.g., a configuration including a single IC).

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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]

[0165] 1. Radar equipment 51 Distance calculation section 52 Speed ​​calculation section 53 Orientation estimation part 54 Signal Judgment Section Tx Transmitting antenna group Rx receiving antennas

Claims

1. A radar device that detects targets using radio waves, a transmitting antenna group (Tx) including a plurality of first antenna elements; a receiving antenna group (Rx) including a plurality of second antenna elements; a distance calculation unit (51) that calculates distance information having a correlation with a distance to the target based on a reception signal received by a MIMO antenna using a plurality of the first antenna elements and a plurality of the second antenna elements; a speed calculation unit (52) that calculates speed information having a correlation with a relative speed with respect to the target based on a signal received by the MIMO antenna; an azimuth estimation unit (53) that estimates an azimuth of the target based on a reception result at the second antenna elements of a reflected wave corresponding to an electric wave transmitted from the first antenna elements; and a signal determination unit (54) that determines whether a signal corresponding to the target obtained based on a reception signal received at the MIMO antenna is a real image or a false image, the first antenna elements and the second antenna elements are arranged such that a portion of the antenna elements receiving radio waves in the MIMO antenna virtually overlaps with another portion of the antenna elements; the signal determination unit extracts, as a comparison component, a signal component that changes depending on a positional relationship between antenna elements from the distance information and the velocity information based on received signals received by each of virtually overlapping antenna elements in the MIMO antenna, before the orientation estimation unit estimates the orientation of the target, and determines whether the signal corresponding to the target is a real image or a false image based on a comparison result of the comparison components.

2. The radar device according to claim 1 , wherein the direction estimating unit estimates the direction of the target based on the signal determined to be a real image by the signal determining unit.

3. the transmitting antenna group includes the first antenna elements arranged at a first interval in a predetermined direction, 3. The radar device according to claim 1, wherein the receiving antenna group includes, in addition to the second antenna elements arranged at an interval different from the first interval in the predetermined direction, the second antenna elements arranged at the first interval in the predetermined direction.

4. 4. The radar device according to claim 3, wherein the first interval is the minimum interval between the first antenna elements adjacent to each other in the predetermined direction.

5. the transmitting antenna group includes the first antenna elements arranged in a predetermined first direction and the first antenna elements arranged in a second direction intersecting the first direction, the receiving antenna group includes the second antenna elements aligned in the first direction and the second antenna elements aligned in the second direction, The signal determination unit extracting the comparison component from the distance information and the velocity information based on reception signals received by each of virtually overlapping antenna elements in a first MIMO antenna using a plurality of the first antenna elements aligned in the first direction and a plurality of the second antenna elements aligned in the first direction, and determining whether a signal corresponding to the target based on the reception signal received by the first MIMO antenna is a real image or a false image based on a comparison result of the comparison component; 3. The radar device according to claim 1, further comprising: a second MIMO antenna using 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, the comparison components being extracted from the distance information and the velocity information based on received signals received by each of virtually overlapping antenna elements; and a determination is made based on a comparison result of the comparison components as to whether a signal corresponding to the target based on the received signal received by the second MIMO antenna is a real image or a false image.

6. the transmitting antenna group includes the first antenna elements arranged at a predetermined first interval in the first direction and the first antenna elements arranged at a predetermined second interval in the second direction, 6. The radar device according to claim 5, wherein the group of receiving antennas includes the second antenna elements arranged at the first interval in the first direction and the second antenna elements arranged at the second interval in the second direction.

7. 7. The radar device according to claim 6, wherein a first minimum interval is a minimum interval between the first antenna elements adjacent to each other in the first direction, and a second minimum interval is a minimum interval between the first antenna elements adjacent to each other in the second direction, the first interval being the first minimum interval and the second interval being the second minimum interval.

8. 3. The radar device according to claim 1, further comprising a plurality of transceiver units (20, 30) including a plurality of the first antenna elements and a plurality of the second antenna elements, and a local signal generated by a common local oscillator (211) is supplied to the plurality of transceiver units.

Images