Radar device

Abstract

To provide a radar device that is able to prevent deterioration in the detection accuracy of a target caused by the influence of mutual coupling between a transmission antenna element and a reception antenna element.SOLUTION: A radar device includes: a transmission antenna group Tx including a plurality of transmission antenna elements; a reception antenna group Rx including a plurality of reception antenna elements; a first azimuth estimation unit 51 that estimates an azimuth of a target in a horizontal direction; and a second azimuth estimation unit 52 that estimates an azimuth of a target in a vertical direction. [0171] Among the plurality of transmission antenna elements, an element closest to any of the reception antenna elements is referred to as a first proximity element, and among the plurality of reception antenna elements, an element closest to any of the transmission antenna elements is referred to as a second proximity element. Further, the minimum interval among intervals between the transmission antenna elements and intervals between the reception antenna elements arranged in the horizontal direction is defined as a first minimum interval. In this case, an interval between the first proximity element and the second proximity element in the horizontal direction is set to be equal to or greater than the first minimum interval.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] Conventionally, there is known a radar device that estimates the azimuth of a target in two different directions by MIMO array technology using a plurality of transmitting antenna elements and receiving antenna elements arranged in two different directions, i.e., horizontal and vertical directions (see, for example, Patent Document 1). Patent Document 1 proposes arranging Tx columns consisting of a plurality of transmitting antenna elements arranged in the vertical direction and Rx rows consisting of a plurality of receiving antenna elements arranged in the horizontal direction in a staggered manner in order to reduce missing portions of virtual antenna elements in the center part of the MIMO antenna. Note that MIMO is an abbreviation for Multi Input Multi Output. In the following, the virtual array antenna generated by the MIMO array technology may be referred to as a MIMO antenna. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 049562 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when trying to reduce the number of missing virtual antenna elements in a MIMO antenna using the method described in Patent Document 1, the intervals between the transmitting antenna elements and the receiving antenna elements located at the vertical and horizontal ends may become too small, which may result in a decrease in target detection accuracy due to the influence of mutual coupling between the transmitting antenna elements and the receiving antenna elements.

[0005] An object of the present disclosure is to provide a radar device capable of suppressing a decrease in target detection accuracy caused by the influence of mutual coupling between a transmitting antenna element and a receiving antenna element. [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 transmitting antenna elements arranged in a first direction at intervals that are a multiple of a predetermined first reference distance and arranged in a second direction intersecting the first direction at intervals that are a multiple of a predetermined second reference distance; a receiving antenna group (Rx) including a plurality of receiving antenna elements arranged in a first direction at intervals that are a multiple of a first reference distance and arranged in a second direction at intervals that are a multiple of a second reference distance; a first direction estimation unit (51) that estimates a direction of a target in a first direction by using a plurality of transmitting antenna elements and a plurality of receiving antenna elements that are arranged in a first direction; a second azimuth estimation unit (52) that estimates an azimuth of a target in the second direction by using the plurality of transmitting antenna elements and the plurality of receiving antenna elements that are arranged in the second direction, Among the multiple transmitting antenna elements, the one that is closest to the receiving antenna element is defined as a first neighboring element (NTx), and among the multiple receiving antenna elements, the one that is closest to the transmitting antenna element is defined as a second neighboring element (NRx), and the smallest spacing between the spacing between the transmitting antenna elements and the spacing between the receiving antenna elements arranged in a first direction is defined as a first minimum spacing, The first neighboring element and the second neighboring element have a first direction interval set to be equal to or greater than a first minimum interval.

[0007] If the transmitting antenna element and the receiving antenna element are arranged in this manner, the effect of mutual coupling between the transmitting antenna element and the receiving antenna element in the first direction can be reduced to the level of mutual coupling between the transmitting antenna elements and the receiving antenna elements. Therefore, according to the radar device of the present disclosure, it is possible to suppress a decrease in the detection accuracy of a target caused by the effect of mutual coupling between the transmitting antenna element and the receiving antenna element.

[0008] Here, if the spacing between the transmitting antenna element and the receiving antenna element is made too large in order to suppress the effect of mutual coupling between the transmitting antenna element and the receiving antenna element, the spacing between adjacent antenna elements in the MIMO antenna will become large, which is undesirable because it causes an increase in side lobes.

[0009] Therefore, in the invention described in claim 2, The multiple transmitting antenna elements and the multiple receiving antenna elements are arranged in a first MIMO antenna, which is a MIMO antenna based on multiple antenna elements arranged in a first direction, so that the distance between adjacent antenna elements is less than or equal to twice the first minimum distance.

[0010] In this way, if the spacing between adjacent antenna elements in the first MIMO antenna is limited to less than twice the first minimum spacing, the number of missing antenna elements in the first MIMO antenna will be reduced, thereby suppressing side lobes.

[0011] Therefore, it is possible to appropriately suppress an increase in side lobes while suppressing a decrease in target detection accuracy due to the influence of mutual coupling between the transmitting antenna element and the receiving antenna element.

[0012] 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]

[0013] [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] FIG. 2 is an explanatory diagram for explaining a first MIMO antenna of a radar device serving as a comparative example of the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram for explaining a second MIMO antenna of a radar device serving as a comparative example of the first embodiment. [Diagram 5] FIG. 2 is an explanatory diagram for explaining a first MIMO antenna of the radar device according to the first embodiment. [Figure 6] FIG. 2 is an explanatory diagram for explaining a second MIMO antenna of the radar device according to the first embodiment. [Figure 7] 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 8] 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 9] 10 is a flowchart showing a flow of horizontal orientation estimation executed by a control unit. [Figure 10] 10 is a flowchart showing a flow of vertical orientation estimation executed by a control unit. [Figure 11] FIG. 2 is an explanatory diagram for explaining positions and power levels of three targets in one embodiment. [Figure 12] FIG. 12 is a spectrum diagram showing a simulation result when estimating the horizontal directions of the three targets shown in FIG. 11 in a case where the outgoing path and the return path of the radio wave coincide with each other. [Figure 13] 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 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 second peak detected in the horizontal direction estimation. [Figure 15] FIG. 11 is an explanatory diagram for explaining a first extension array antenna of a radar device according to a second embodiment. [Figure 16] FIG. 2 is an explanatory diagram for explaining features of the first extension array antenna. [Figure 17] FIG. 11 is an explanatory diagram for explaining a window function. [Figure 18] FIG. 11 is an explanatory diagram for explaining a second extension array antenna of a radar device according to a second embodiment. [Figure 19] FIG. 11 is an explanatory diagram for explaining features of the second extension array antenna. [Figure 20] FIG. 12 is a spectrum diagram showing a simulation result when estimating the horizontal directions of the three targets shown in FIG. 11 in a case where the outgoing path and the return path of the radio wave coincide with each other. [Figure 21] 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 22] 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 23] FIG. 11 is a schematic configuration diagram of a radar device according to a third embodiment. [Figure 24] FIG. 11 is an explanatory diagram for explaining an antenna configuration of a radar device according to a third embodiment. [Diagram 25] FIG. 11 is an explanatory diagram for explaining a first MIMO antenna of a radar device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] (First embodiment) The present embodiment will be described with reference to Fig. 1 to Fig. 14. 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.

[0016] 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.

[0017] 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.

[0018] 1, the radar device 1 includes a radar unit RU and a control unit 50. The radar unit RU is implemented on a semiconductor chip such as an MMIC. Note that MMIC is an abbreviation for Monolithic Microwave Integrated Circuit.

[0019] The radar unit RU includes a transmitting antenna group Tx including a plurality of actual transmitting antenna elements Tx1-Tx8, a receiving antenna group Rx including a plurality of actual receiving antenna elements Rx1-Rx8, and a transmitting / receiving unit 20. The transmitting / receiving unit 20 includes a transmitting unit 21 and a receiving unit 22.

[0020] The transmitter 21 generates signals to be transmitted from the transmitting antenna group Tx and transmits them to the transmitting antenna group Tx. Specifically, the transmitter 21 generates local signals and transmits the generated local signals to the receiver 22. The transmitter 21 also generates chirp signals whose frequency changes continuously and provides the generated chirp signals to the transmitting antenna group Tx. The transmitting antenna group Tx then transmits radio waves corresponding to the chirp signals provided from the transmitter 21 toward the front of the vehicle.

[0021] The transmitting antenna group Tx in this example has eight actual transmitting antenna elements Tx1 to Tx8. The eight transmitting antenna elements Tx1 to Tx8 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, 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".

[0022] In the transmitting antenna group Tx, two transmitting antenna elements Tx1, Tx2 are arranged side by side in the horizontal direction U above the vertical direction V, and two transmitting antenna elements Tx7, Tx8 are arranged side by side in the horizontal direction U below the vertical direction V. Then, four transmitting antenna elements Tx3 to Tx6 are arranged side by side in the horizontal direction U approximately in the center of the vertical direction V.

[0023] The two transmitting antenna elements Tx1, Tx2 at the top and the four transmitting antenna elements Tx3 to Tx6 at approximately the center in the vertical direction V are arranged at an interval of "1dv", which is one time the vertical reference distance dv, in the vertical direction V. Similarly, the two transmitting antenna elements Tx7, Tx8 at the bottom and the four transmitting antenna elements Tx3 to Tx6 at approximately the center in the vertical direction V are arranged at an interval of "1dv", which is one time the vertical reference distance dv, in the vertical direction V.

[0024] In this manner, the transmitting antenna group Tx of this embodiment includes transmitting antenna elements Tx1 to Tx8 that are arranged at intervals that are a multiple of the vertical reference distance dv. In this embodiment, the vertical reference distance dv corresponds to the "second reference distance."

[0025] 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 "40°" and the vertical reference distance dv is set to "3 / 2·λ", where λ is the wavelength of the radio wave.

[0026] 1 / sin(φfov / 180 π) 2 <dv ···(F1) Moreover, the two upper transmitting antenna elements Tx1, Tx2 are spaced apart by an interval equal to the antenna aperture length of the receiving antenna elements Rx1 to R4 ("9d" in this example) plus a reference interval that is a multiple of the horizontal reference distance dh ("5d" in this example). Specifically, the two upper transmitting antenna elements Tx1, Tx2 are spaced apart by "14dh", which is 14 times the horizontal reference distance dh in the horizontal direction U.

[0027] Similarly, the two lower transmitting antenna elements Tx7 and Tx8 are spaced apart by an interval (14dh 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 receiving antenna elements Rx1 to R4.

[0028] The four transmitting antenna elements Tx3 to Tx6 located approximately in the center include those that are arranged at intervals (14dh 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 receiving antenna elements Rx1 to R4.

[0029] Specifically, the transmitting antenna elements Tx3 and Tx6 at both ends of the horizontal direction U are spaced apart by an interval (14dh in this example) that is the sum of the antenna aperture length of the receiving antenna elements Rx1 to R4 and a reference interval that is a multiple of the horizontal reference distance dh. The transmitting 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 transmitting 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.

[0030] In this manner, the transmitting antenna group Tx of this embodiment includes transmitting antenna elements Tx1 to Tx8 that are arranged at intervals that are a multiple of the horizontal reference distance dh. In this embodiment, the horizontal reference distance dh corresponds to the "first reference distance."

[0031] 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.

[0032] 1 / sin(θfov / 180 π) 2 <dh ···(F2) Here, the interval between the transmitting antenna elements Tx1 to Tx8 may be strictly a multiple 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 violate the spirit of the technology of the present disclosure. Also, the interval between the transmitting antenna elements Tx1 to Tx8 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 violate the spirit of the technology of the present disclosure. The same applies to the interval between the receiving antenna elements Rx1 to Rx8.

[0033] 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 eight actually existing receiving antenna elements Rx1 to Rx8. The eight receiving 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.

[0034] Specifically, the receiving antenna group Rx includes four receiving antenna elements Rx1 to Rx4 arranged along the horizontal direction U on one side (upper side in this example) of the vertical direction V of the transmitting antenna group Tx. The receiving antenna group Rx also includes four receiving antenna elements Rx5 to Rx8 arranged along the horizontal direction U on the other side (lower side in this example) of the vertical direction V of the transmitting antenna group Tx. The receiving antenna elements Rx1 to Rx4 in the first row and the receiving 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. In this way, the receiving antenna group Rx of this embodiment includes receiving antenna elements Rx1 to Tx8 arranged at an interval that is a multiple of the horizontal reference distance dh.

[0035] Moreover, the receiving antenna elements Rx1 to Rx4 in the first row and the receiving antenna elements Rx5 to Rx8 in the second row are arranged to face each other in the vertical direction V. The receiving antenna elements Rx1 to Rx4 in the first row and the receiving antenna elements Rx5 to Rx8 in the second row are arranged at an interval of "4dv", which is four times the vertical reference distance dv. In this way, the receiving antenna group Rx of this embodiment includes receiving antenna elements Rx1 to Rx8 arranged at an interval that is a multiple of the vertical reference distance dv.

[0036] The multiple transmitting antenna elements Tx1 to Tx8 and the multiple receiving antenna elements Rx1 to Rx8 are arranged such that a substantial quadrangle is formed when adjacent elements are connected with imaginary lines.

[0037] Here, in this embodiment, among the multiple transmitting antenna elements Tx1 to Tx8, the transmitting antenna elements Tx1, Tx2, Tx7, and Tx8 located at both ends in the horizontal direction U and the vertical direction V are located closest to the receiving antenna elements Rx1 to Rx8. In this embodiment, the transmitting antenna elements Tx1, Tx2, Tx7, and Tx8 located at both ends in the horizontal direction U and the vertical direction V correspond to the "first nearest element NTx."

[0038] Among the multiple receiving antenna elements Rx1 to Rx8, the receiving antenna elements Rx1, Rx4, Rx5, and Rx8 located at both ends in the horizontal direction U and the vertical direction V are located closest to the transmitting antenna elements Tx1 to Tx8. In this embodiment, the receiving antenna elements Rx1, Rx4, Rx5, and Rx8 located at both ends in the horizontal direction U and the vertical direction V correspond to the "second nearest element NRx."

[0039] Here, in a MIMO antenna using multiple transmitting antenna elements Tx1 to Tx8 and multiple receiving antenna elements Rx1 to Rx8, it is desirable that the antenna elements are arranged at equal intervals with desired intervals. For this reason, it is desirable to configure the MIMO antenna so that the number of missing virtual antenna elements is as small as possible, but such a configuration may result in the interval between the first nearest element NTx and the second nearest element NRx becoming too small.

[0040] For example, as shown in the comparative example of Fig. 3, the interval in the horizontal direction U between transmitting antenna elements Tx1 to Tx3 and Tx6 to Tx8 at both ends in the horizontal direction U is assumed to be "12dh". In this case, in the first MIMO antenna, which is a MIMO antenna in the horizontal direction U, the interval between virtual antenna elements in the central portion is "1dh", resulting in an antenna configuration with few missing virtual antenna elements.

[0041] On the other hand, the distance in the horizontal direction U between the first nearby elements NTx such as transmitting antenna elements Tx3, Tx6, etc. and the second nearby elements NRx such as receiving antenna elements Rx1, Rx4, etc. is smaller than the distance between each of the antenna elements Tx1 to Tx8, Rx1 to Rx8 in the horizontal direction U. In the comparative example of Fig. 3, the distance between each of the nearby elements NTx, NRx in the horizontal direction U is half the distance between the receiving antenna elements Rx1 to Rx8 adjacent in the horizontal direction U (in this example, "3 / 2·dh"), resulting in an antenna configuration that is susceptible to the effects of mutual coupling.

[0042] 4, for example, assume that the spacing in the vertical direction V between receiving antenna elements Rx1 to Rx8 at both ends of the vertical direction V is "3dv." In this case, in the second MIMO antenna, which is a MIMO antenna in the vertical direction V, the spacing between virtual antenna elements in the central portion is "1dv," resulting in an antenna configuration with fewer missing virtual antenna elements.

[0043] On the other hand, the distance in the vertical direction V between the first neighboring elements NTx, such as transmitting antenna elements Tx1, Tx7, and the second neighboring elements NRx, such as receiving antenna elements Rx1, Rx4, is smaller than the distance in the vertical direction V between each of the antenna elements Tx1 to Tx8, Rx1 to Rx8.

[0044] In the comparative example of Figure 4, the distance between each adjacent element NTx, NRx in the vertical direction V is half the distance between adjacent receiving antenna elements Rx1 to Rx8 in the vertical direction V (in this example, "1 / 2 dv"), resulting in an antenna configuration that is susceptible to the effects of mutual coupling.

[0045] Here, in free space, radio waves attenuate in proportion to the square of the distance. Specifically, when the distance and wavelength are the same, the attenuation of the radio waves is "22 dB." For this reason, for example, if you want to keep the mutual coupling below "20 dB," the spacing between antenna elements must be set to one wavelength or more.

[0046] Taking these factors into consideration, the radar device 1 sets the intervals between the first proximity element NTx and the second proximity element NRx so as to suppress the influence of mutual coupling. Hereinafter, the intervals between the first proximity element NTx and the second proximity element NRx in this embodiment will be described.

[0047] In this embodiment, the interval in the horizontal direction U between the first neighboring element NTx and the second neighboring element NRx is set to be equal to or greater than a first minimum interval, which is the smallest of the intervals between the transmitting antenna elements Tx1 to Tx8 and the intervals between the receiving antenna elements Rx1 to Rx8 aligned in the horizontal direction U. The first minimum interval in this example is "2dh".

[0048] However, if the distance between the adjacent elements NTx, NRx is made too large, the distance between the virtual antenna elements in the central portion of the first MIMO antenna, which is a MIMO antenna in the horizontal direction U, becomes large.

[0049] Taking this into consideration, in this embodiment, the multiple transmitting antenna elements Tx1 to Tx8 and the multiple receiving antenna elements Rx1 to Rx8 are arranged so that the distance between adjacent antenna elements in the first MIMO antenna is equal to or less than twice the first minimum distance.

[0050] Specifically, as shown in the upper part of FIG. 5, the spacing in the horizontal direction U between the transmitting antenna elements Tx1 to Tx3 and Tx6 to Tx8 at both ends of the horizontal direction U is set to "14dh", and the spacing between each of the adjacent elements NTx and NRx is set to "5 / 2 dh", which is larger than the first minimum spacing.

[0051] According to this, as shown in the lower part of Figure 5, the spacing between virtual antenna elements in the central part of the first MIMO antenna is at most "2dh", and can be limited to less than "4dh", which is twice the first minimum spacing.

[0052] Additionally, in this embodiment, the spacing between the first neighboring element NTx and the second neighboring element NRx in the vertical direction V is set to be equal to or greater than a second minimum spacing which is the smallest of the spacing between the transmitting antenna elements Tx1-Tx8 and the spacing between the receiving antenna elements Rx1-Rx8 aligned in the vertical direction V. The second minimum spacing in this example is "1dv".

[0053] However, if the distance between the adjacent elements NTx, NRx is made too large, the distance between the antenna elements in the central portion of the second MIMO antenna, which is a MIMO antenna in the vertical direction V, becomes large.

[0054] Taking this into consideration, in this embodiment, the multiple transmitting antenna elements Tx1 to Tx8 and the multiple receiving antenna elements Rx1 to Rx8 are arranged so that the distance between adjacent antenna elements in the second MIMO antenna is equal to or less than twice the second minimum distance.

[0055] Specifically, as shown on the left side of Figure 6, the spacing in the vertical direction V between the receiving antenna elements Rx1 to Rx8 at both ends of the vertical direction V is set to "4dv", and the spacing between each adjacent element NTx, NRx is set to "1dv", which is larger than the first minimum spacing.

[0056] According to this, as shown on the right side of Figure 6, the spacing between virtual antenna elements in the central part of the second MIMO antenna is at most "2dv", and can be limited to less than "2dv", which is twice the second minimum spacing.

[0057] The receiving unit 22 generates a beat signal based on the reception signals received by the receiving antenna group Rx and the local signal transmitted from the transmitting unit 21, samples the beat signal, and provides it to the control unit 50. Although not shown, the receiving unit 22 is configured to include a mixer, an amplifier, an AD converter, etc.

[0058] 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.

[0059] The control unit 50 estimates the azimuth of the target in two mutually intersecting directions by MIMO using a plurality of transmitting antenna elements Tx1 to Tx8 and receiving antenna elements Rx1 to Rx8 aligned in the horizontal direction U and vertical direction V.

[0060] The radar device 1 of this embodiment has a plurality of transmitting antenna elements Tx3 to Tx6 arranged in the horizontal direction U and a plurality of receiving antenna elements Rx1 to Rx4 arranged in the horizontal direction U. Therefore, the control unit 50 estimates the azimuth of the target with respect to the horizontal direction U using a first MIMO array antenna including a plurality of transmitting antenna elements Tx3 to Tx6 arranged in the horizontal direction U and a plurality of receiving antenna elements Rx1 to Rx4 arranged in the horizontal direction U. The radar device 1 of this embodiment also has a plurality of transmitting antenna elements Tx1 to Tx3, Tx6 to Tx8 arranged in the vertical direction V and a plurality of receiving antenna elements Rx1 to Rx8 arranged in the vertical direction V. Therefore, the control unit 50 estimates the azimuth of the target with respect to the vertical direction V using a second MIMO antenna including a plurality of transmitting antenna elements Tx1 to Tx3, Tx6 to Tx8 arranged in the vertical direction V and a plurality of receiving antenna elements Rx1 to Rx8 arranged in the vertical direction V. In this embodiment, a configuration in the control unit 50 that estimates the azimuth of a target in the horizontal direction U corresponds to a “first azimuth estimation unit 51,” and a configuration in the control unit 50 that estimates the azimuth of a target in the vertical direction V corresponds to a “second azimuth estimation unit 52.”

[0061] Here, the MIMO antenna is premised on the assumption that the outgoing and return paths of the radio waves are substantially the same, as shown in the upper part of Fig. 7 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. 7 for the MIMO antenna, not only a signal corresponding to the target, but also a signal corresponding to a direction different from the target's direction is detected as a false image. Such false images occur in both the first MIMO antenna that estimates the direction in the horizontal direction U and the second MIMO antenna that estimates the direction in the vertical direction V. Note that the mirror-image reflected wave occurs when objects on the side of the road, such as guardrails and walls, or the road surface act as mirrors.

[0062] On the other hand, a MIMO antenna and an antenna configuration different from the MIMO antenna (for example, SIMO, MISO) tend to have different peaks in a direction where no target exists (i.e., false peaks). SIMO is an abbreviation for Single Input Multi Output. MISO is an abbreviation for Multi Input Single Output.

[0063] In consideration of these, the radar device 1 of this embodiment detects a signal corresponding to a target by both the MIMO antenna and an antenna configuration different from the MIMO 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 50 that determines whether the signal corresponding to the target is a real image or a false image corresponds to the "signal determination unit."

[0064] Next, the target detection process executed by the control unit 50 of the radar device 1 will be described with reference to Fig. 8. The process shown in Fig. 8 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.

[0065] 8, in step S100, the control unit 50 receives a reflected wave from a target using the receiving antenna group Rx. This received signal is mixed with a local signal by the mixer of the receiving unit 22. After that, a desired frequency component is extracted by a low-pass filter, and the frequency component is provided from the receiving unit 22 to the control unit 50 as a beat signal.

[0066] Next, the control unit 50 performs distance FFT processing in step S110. The control unit 50 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.

[0067] 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.

[0068] Next, in step S130, the control unit 50 executes a horizontal direction estimation process to estimate the direction of the target in the horizontal direction U. This horizontal direction estimation process will be described with reference to FIG.

[0069] 9, in step S131, the control unit 50 estimates the azimuth of the target in the horizontal direction U by the antenna configuration (horizontal MIMO) of the first MIMO antenna. 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.

[0070] Next, in step S132, the control unit 50 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 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 SIMO differs depending on the angle of arrival of the reflected wave.

[0071] Unlike a MIMO antenna configuration, a SIMO antenna configuration does not cause any mismatch between the outbound and return paths of radio waves, so no false images occur, which is a problem with MIMO antenna configurations.

[0072] Next, in step S133, the control unit 50 selects a signal to be determined as a real image or a false image from among the spectral signals detected in one of the horizontal MIMO and horizontal SIMO. For example, the control unit 50 selects a spectral signal 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 spectral signal when the signal corresponding to the target is a real image. Note that the control unit 50 may select the spectral signal to be determined based on the spectral signal in the horizontal SIMO.

[0073] Next, in step S134, the control unit 50 determines whether the peak positions and peak levels of the spectrum signals in the horizontal SIMO and horizontal MIMO are within a predetermined determination region. For example, the control unit 50 determines whether the spectrum signal in the horizontal SIMO, the difference in peak levels of which is equal to or less than a predetermined threshold, is present within a predetermined range including the peak position of the spectrum signal in the horizontal MIMO to be determined.

[0074] The predetermined range and the predetermined threshold used in this determination are set by experiments and simulations. The predetermined range is set, for example, to the maximum value between the peak position of the spectrum signal in horizontal SIMO and the peak position of the spectrum signal in horizontal MIMO when the signal corresponding to the target is a real image. The predetermined threshold is set, for example, to the maximum value of the difference between the peak level of the spectrum signal in horizontal SIMO and the peak level of the spectrum signal 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 in horizontal MIMO.

[0075] If the peak positions and peak levels of the spectral signals in the horizontal SIMO and horizontal MIMO are within a predetermined judgment region, the control unit 50 judges in step S135 that the signal corresponding to the target to be judged is a "real image."

[0076] On the other hand, if the peak positions and peak levels of the spectral signals in the horizontal SIMO and horizontal MIMO are outside the predetermined judgment region, the control unit 50 determines in step S136 that the signal corresponding to the target to be judged is a “false image”.

[0077] 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 50 proceeds to step S140 in Fig. 8 and executes a vertical orientation estimation processing for estimating the orientation of the target in the vertical direction V. This vertical orientation estimation processing will be described with reference to Fig. 10.

[0078] 10, in step S141, the control unit 50 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 50 estimates the azimuth of the target in the vertical direction V by using transmitting antenna elements Tx1 to Tx3, Tx6 to Tx8 and receiving antenna elements Rx1 to Rx8 arranged in the horizontal direction U.

[0079] Next, in step S142, the control unit 50 estimates the azimuth of the target in the vertical direction V by the antenna configuration of the second MIMO antenna (vertical MIMO). The control unit 50 estimates the azimuth of the target in the vertical direction V by using transmitting antenna elements Tx1-Tx3, Tx6-Tx8 and two rows of receiving antenna elements Rx1-Rx4, Rx5-Rx8 aligned in the horizontal direction U.

[0080] Next, in step S143, the control unit 50 selects a signal to be determined as a real image or an artifact from among the spectral signals detected in either the vertical MISO or vertical MIMO. For example, the control unit 50 selects a spectral signal in the vertical MIMO whose peak level exceeds a predetermined selection threshold as the determination target. The selection threshold is set by experiment or simulation. The control unit 50 may select the spectral signal to be determined based on the spectral signal in the vertical MISO.

[0081] Next, in step S144, the control unit 50 judges whether the peak positions and peak levels of the spectrum signals in the vertical MISO and vertical MIMO are within a predetermined judgment region. For example, the control unit 50 judges whether the spectrum signal in the vertical MISO, the difference of the peak levels of which is equal to or less than a predetermined threshold, is present within a predetermined range including the peak position of the spectrum signal 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 estimation process.

[0082] When the peak positions and peak levels of the spectral signals in the vertical MISO and vertical MIMO are within the predetermined judgment region, the control unit 50 judges in step S145 that the signal corresponding to the target to be judged is a "real image."

[0083] On the other hand, if the peak positions and peak levels of the spectral signals in the vertical MISO and vertical MIMO are outside the predetermined judgment region, the control unit 50 judges in step S146 that the signal corresponding to the target to be judged is a "false image."

[0084] 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 50 proceeds to step S150 in Fig. 8 and detects targets based on the signals identified as real images in the signal determination processing.

[0085] 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.

[0086] First, a simulation result in the case where there are three targets that serve as targets trg will be described with reference to Figs. 11 to 14. In the simulation of this example, as shown in Fig. 11, 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.

[0087] sin(10° / 180°·π)≒0.17···(F3) Figure 12 shows the simulation results when the azimuth of a target in the horizontal direction U is estimated by horizontal MIMO under the condition that the outgoing path and the return path of the radio wave are aligned. As shown in Figure 12, 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.

[0088] Moreover, Fig. 13 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 in this example) corresponding to the first target trg1 detected in the azimuth estimation in the horizontal direction U. As shown in Fig. 13, under the condition that the outbound 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 third target trg3.

[0089] 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=0.185 in this example) corresponding to the second target trg2 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 result was that a peak of the spectrum signal was detected at the position corresponding to the second target trg2.

[0090] 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.

[0091] In this embodiment, the distance between the first adjacent element NTx and the second adjacent element NRx is increased to suppress the influence of mutual coupling between the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8. This generates a side lobe SL, but since the distance between the antenna elements in the MIMO antenna is limited, the size of the side lobe SL becomes sufficiently smaller than the peak of the spectrum signal at the position corresponding to each target trg1 to trg3. This greatly contributes to improving the detection accuracy of targets including azimuth estimation.

[0092] The radar device 1 described above includes a plurality of transmitting antenna elements Tx1-Tx8 and a plurality of receiving antenna elements Rx1-Rx8 arranged in the horizontal direction U at intervals that are a multiple of the horizontal reference distance dh, and arranged in the vertical direction V at intervals that are a multiple of the vertical reference distance dv. In the radar device 1, the interval in the horizontal direction U between a first neighboring element NTx included in the plurality of transmitting antenna elements Tx1-Tx8 and a second neighboring element NRx included in the plurality of receiving antenna elements Rx1-Rx8 is set to be equal to or greater than a first minimum interval in the horizontal direction U.

[0093] If the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 are arranged in this manner, the influence of mutual coupling between the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 in the horizontal direction U can be suppressed.

[0094] Therefore, according to the radar device 1 of this embodiment, it is possible to suppress a decrease in the detection accuracy of a target caused by the influence of mutual coupling between the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8.

[0095] Moreover, the radar device 1 of this embodiment has the following features.

[0096] (1) The transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 are arranged such that the distance between adjacent antenna elements in the first MIMO antenna based on a plurality of antenna elements aligned in the horizontal direction U is equal to or less than twice the first minimum distance. In this way, if the distance between adjacent antenna elements in the first MIMO antenna is limited to equal to or less than twice the first minimum distance, the number of missing antenna elements in the first MIMO antenna is reduced, and the side lobe SL can be suppressed. Therefore, it is possible to appropriately suppress an increase in the side lobe SL while suppressing a decrease in the target detection accuracy due to the influence of mutual coupling between the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8.

[0097] (2) In the radar device 1, the distance in the vertical direction V between the first neighboring element NTx and the second neighboring element NRx is set to be equal to or greater than the second minimum distance in the vertical direction V. This makes it possible to suppress the effects of mutual coupling in the vertical direction V between the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8.

[0098] (3) The transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 are arranged such that the distance between adjacent antenna elements in the second MIMO antenna based on a plurality of antenna elements aligned in the horizontal direction U is equal to or less than twice the second minimum distance. This reduces the number of missing antenna elements in the second MIMO antenna, thereby suppressing the side lobe SL. Therefore, it is possible to appropriately suppress the increase in the side lobe SL while suppressing the deterioration of the target detection accuracy due to the influence of mutual coupling between the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8.

[0099] (4) In the radar device 1 of this embodiment, the control unit 50 estimates the azimuth of the target in the horizontal direction U using the first MIMO antenna, and estimates the azimuth of the target in the vertical direction V using the second MIMO antenna. The control unit 50 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. In this way, if the control unit 50 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, the target azimuth can be estimated using the signals determined to be real images, thereby suppressing a decrease in detection accuracy of the target azimuth caused by false images.

[0100] (5) In addition to the first MIMO antenna, the control unit 50 estimates the azimuth of the target in the horizontal direction U using an antenna configuration different from the first MIMO antenna, and compares the respective estimation results to determine whether a signal corresponding to the 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 the target in the horizontal direction U is a real image or a false image, so that the device configuration can be realized simply.

[0101] Here, in the above embodiment, the target's azimuth estimation result in horizontal MIMO and the target's azimuth estimation result in horizontal SIMO are compared to perform false image judgment of the signal corresponding to the target. When performing such false image judgment, if the difference between the antenna aperture length in horizontal MIMO and the antenna aperture length in horizontal SIMO is too large, the difference in resolution between the two may affect the accuracy of false image judgment. For this reason, it is desirable that the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 are arranged so that the influence of mutual coupling is suppressed and the difference between the antenna aperture length in horizontal MIMO and the antenna aperture length in horizontal SIMO is equal to or less than a predetermined value. This also applies to the case where the target's azimuth estimation result in vertical MIMO and the target's azimuth estimation result in vertical MISO are compared to perform false image judgment of the signal corresponding to the target.

[0102] (6) In addition to the second MIMO antenna, the control unit 50 estimates the azimuth of the target in the vertical direction V using an antenna configuration different from the second MIMO antenna, and compares the respective estimation 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 the functional configuration of the radar device 1 determines whether the signal corresponding to the target in the vertical direction V is a real image or a false image, so that the device configuration can be simplified.

[0103] (7) Incidentally, 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 causes a situation in which the outgoing path and the returning 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 also tends to cause a situation in which the outgoing path and the returning path of the radio waves do not match in the vertical direction V.

[0104] For this reason, it is desirable 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.

[0105] (Modification of the first embodiment) As in the first embodiment, the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 are preferably arranged so that the distance between adjacent antenna elements in the first MIMO antenna is equal to or less than twice the first minimum distance, but is not limited to this. The transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 may be arranged so that the distance between adjacent antenna elements in the first MIMO antenna is greater than twice the first minimum distance. This also applies to the following embodiments.

[0106] As in the first embodiment, it is preferable that the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 are arranged so that the interval between adjacent antenna elements in the second MIMO antenna is equal to or less than twice the second minimum interval, but is not limited to this. The transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 may be arranged so that the interval between adjacent antenna elements in the second MIMO antenna is greater than twice the second minimum interval. This also applies to the following embodiments.

[0107] As in the first embodiment, it is preferable that the interval between the first neighboring element NTx and the second neighboring element NRx in the horizontal direction U is set to be equal to or greater than the first minimum interval, and the interval between the first neighboring element NTx and the second neighboring element NRx in the vertical direction V is set to be equal to or greater than the second minimum interval, but this is not necessarily the case. For example, the interval between the first neighboring element NTx and the second neighboring element NRx in the horizontal direction U may be set to be equal to or greater than the first minimum interval, and the interval between the first neighboring element NTx and the second neighboring element NRx in the vertical direction V may be set to be less than the first minimum interval. Also, the interval between the first neighboring element NTx and the second neighboring element NRx in the horizontal direction U may be set to be less than the first minimum interval, and the interval between the first neighboring element NTx and the second neighboring element NRx in the vertical direction V may be set to be equal to or greater than the second minimum interval. This also applies to the following embodiments.

[0108] As in the above embodiment, it is preferable that the radar device 1 is configured to be able to determine whether a signal corresponding to a target is a real image or a false image, but it does not have to be configured in this way. Note that the method of determining whether a signal corresponding to a target is a real image or a false image may be different from that specifically described in the above embodiment.

[0109] In the above embodiment, the horizontal direction U is the "first direction" and the vertical direction V is the "second direction", but this is not limiting, and the horizontal direction U may be the "second direction" and the vertical direction V may be the "first direction". This also applies to the following embodiments.

[0110] Second embodiment Next, a second embodiment will be described with reference to Fig. 15 to Fig. 22. In this embodiment, differences from the first embodiment will be mainly described.

[0111] The control unit 50 of this embodiment is configured to use a first extended array antenna to perform azimuth estimation processing in the horizontal direction U. The first extended array antenna includes, in addition to the antenna elements of the first MIMO antenna, virtual antenna elements interpolated using a differential signal corresponding to a phase difference between the antenna elements of the first MIMO antenna caused by radio waves arriving from a direction intersecting the horizontal direction U.

[0112] Such a first extended array antenna is obtained by interpolating signals at missing antenna locations in the non-uniformly spaced array obtained by the first MIMO antenna through an extension process using differential signals corresponding to phase differences between multiple antenna elements, as shown in Fig. 15. The extension process in this example is Khatri-Rao product extended array processing.

[0113] Here, the matrix shown on the left side of FIG. 16 is the dispersion matrix e of the received signal at the antenna element and the complex conjugate of the received signal for the first MIMO antenna shown in FIG. iω The table on the right side of Fig. 16 shows the distribution matrix e iω The table on the right side of Fig. 16 shows the relationship between the exponent part of the independent components and the number of signals corresponding to each antenna element. The numerical values ​​(indexes) arranged in the table on the right side of Fig. 16 indicate the respective arrangement positions in the extended array antenna.

[0114] The first extended array antenna obtained by such an extension process has an antenna configuration with a larger aperture than the first MIMO antenna. Moreover, in the first extended array antenna, the antenna elements are arranged so that they are evenly spaced near the center. Note that in the first 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 components is "21" after "19", and "20" does not exist. Moreover, the index of the independent components is "-21" after "-19", and "-20" does not exist. This causes an increase in the side lobe SL.

[0115] Considering this, the control unit 50 of this embodiment performs weighting by window function processing on the signals corresponding to the antenna elements constituting the first extended array antenna. In this window function processing, for example, the Hann window or Blackman window shown in Fig. 17 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.

[0116] Furthermore, in the first 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 is greater than the number of signals detected at a position farthest from the median value. Note that, in the first extended array antenna of this example, when the position where the index of the independent components is "0" is taken as the reference position, the number of signals does not decrease but increases or decreases as it moves away from the reference position. For example, the number of signals is 16 at the reference position, but decreases to 9 at "-1" and increases to 10 at "-2".

[0117] Considering this, when multiple signals corresponding to the antenna elements constituting the first extended array antenna are obtained, the control unit 50 adds and averages the multiple signals. In other words, when there are multiple numbers corresponding to the installation positions in the extended array antenna, the control unit 50 averages the multiple difference signals obtained at the installation positions. In this way, interference between adjacent targets is suppressed.

[0118] Moreover, the control unit 50 of this embodiment is configured to perform azimuth estimation processing in the vertical direction V by using the second extended array antenna. In addition to the antenna elements of the second MIMO antenna, the second extended array antenna includes virtual antenna elements interpolated using a differential signal corresponding to a phase difference between the antenna elements of the second MIMO antenna caused by radio waves arriving from a direction intersecting the vertical direction V.

[0119] Such a second extended array antenna is obtained by interpolating signals at missing antenna locations in the non-uniformly spaced array obtained by the second MIMO antenna through an extension process using differential signals corresponding to the phase differences between multiple antenna elements, as shown in Fig. 18. The extension process in this example is Khatri-Rao product extended array processing.

[0120] Here, FIG. 19 shows the distribution matrix e iω 19 shows the correspondence between the exponent part of the independent components and the number of signals corresponding to each antenna element. Note that Fig. 19 corresponds to the table shown on the right side of Fig. 16. The numerical values ​​(exponents) arranged in the table shown in Fig. 19 indicate the respective arrangement positions in the extended array antenna.

[0121] The second extended array antenna obtained by such an extension process has an antenna configuration with a larger aperture than the second MIMO antenna. In addition, in the second extended array antenna, the indexes of the independent components at both ends are not consecutive. Therefore, the control unit 50 of this embodiment performs weighting by window function processing on the signals corresponding to the antenna elements constituting the first extended array antenna.

[0122] In addition, in the first 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 exponents of the independent components is greater than the number of signals detected at a position farthest from the median value. In consideration of this, when multiple signals corresponding to the antenna elements constituting the second extended array antenna are obtained, the control unit 50 adds and averages the multiple signals. This suppresses interference between adjacent targets.

[0123] Hereinafter, the simulation results of the azimuth estimation of the target in the horizontal direction U and the vertical direction V using the first and second extended array antennas will be described with reference to Figs. 20 to 22. In the simulation of this example, as in the first embodiment, three targets trg1, trg2, and trg3 are assumed to be present at the positions shown in Fig. 11. Note that Fig. 20 shows a simulation result when the azimuth of the target in the horizontal direction U is estimated by horizontal MIMO under the condition that the outward and return paths of the radio waves are coincident. Fig. 21 shows a simulation result when the azimuth of the target in the vertical direction V is estimated by reproducing a spectrum signal in the azimuth corresponding to the first target trg1 detected in the azimuth estimation in the horizontal direction U. Fig. 22 shows a simulation result when the azimuth of the target in the vertical direction V is estimated by reproducing a spectrum signal in the azimuth corresponding to the second target trg2 detected in the azimuth estimation in the horizontal direction U.

[0124] As shown in Figures 20 to 22, under conditions in which the outbound and return paths of the radio waves are aligned, the peaks of the spectrum signal were detected at positions corresponding to the three targets trg1, trg2, and trg3, and the side lobes SL were also sufficiently suppressed.

[0125] 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.

[0126] Moreover, the radar device 1 of this embodiment has the following features.

[0127] (1) The control unit 50 estimates the azimuth of a target in the horizontal direction U by using a first 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 the horizontal direction U. This makes it possible to interpolate missing antenna elements in the first MIMO antenna with virtual antenna elements based on a differential signal corresponding to a phase difference between each antenna element caused by radio waves arriving from a direction intersecting the horizontal direction U. As a result, the occurrence of side lobes SL due to missing antenna elements can be sufficiently suppressed, and therefore the deterioration of the detection accuracy of the target in the horizontal direction U can be sufficiently suppressed.

[0128] (2) The control unit 50 performs weighting by window function processing on the signals corresponding to the antenna elements constituting the first extended array antenna. This reduces the side lobes SL, and therefore, the deterioration of the detection accuracy of the target in the horizontal direction U can be sufficiently suppressed.

[0129] (3) The control unit 50 estimates the azimuth of the target in the vertical direction V by using a second extended array antenna including virtual antenna elements interpolated using a differential signal corresponding to the phase difference between a plurality of antenna elements caused by radio waves arriving from a direction intersecting the vertical direction V. This makes it possible to interpolate missing antenna elements in the second MIMO antenna with virtual antenna elements based on a differential signal corresponding to the phase difference between each antenna element caused by radio waves arriving from a direction intersecting the vertical direction V. As a result, the occurrence of side lobes SL can be sufficiently suppressed, and therefore the deterioration of the detection accuracy of the target in the vertical direction V can be sufficiently suppressed.

[0130] (4) The control unit 50 performs weighting by window function processing on the signals corresponding to the antenna elements constituting the second extended array antenna. This reduces the side lobes SL, and therefore, the deterioration of the detection accuracy of the target in the vertical direction V can be sufficiently suppressed.

[0131] (5) Here, when two targets are used as targets trg, a signal with a large peak may appear between two main lobes corresponding to real images due to interference between the targets trg. Such a signal may affect the result of identifying whether the image is real or false. In consideration of this, in the radar device 1 of this embodiment, when multiple signals corresponding to the antenna elements constituting each extended array antenna are obtained, the multiple signals are averaged. This can reduce the effect of interference between the targets trg, so that even when two targets are used as targets trg, it is possible to appropriately identify whether the image is real or false.

[0132] (Modification of the second embodiment) When multiple signals corresponding to the antenna elements constituting each extended array antenna are obtained, 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 the antenna elements constituting each extended array antenna are obtained, the radar device 1 may be configured to select the maximum or minimum signal from the multiple signals.

[0133] The radar device 1 is preferably configured to weight signals corresponding to antenna elements constituting each extended array antenna by window function processing, but is not limited to this. The radar device 1 may not weight signals corresponding to antenna elements constituting each extended array antenna by window function processing.

[0134] Third embodiment Next, a third embodiment will be described with reference to Figures 23 to 25. In this embodiment, differences from the first embodiment will be mainly described.

[0135] 23, the radar device 1 includes a plurality of radar units RU1, 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.

[0136] The first radar unit RU1 constitutes a first transceiver section 20, and includes a first transmitter section 21, actual transmitting antenna elements Tx1-Tx4, a plurality of actual receiving antenna elements Rx1-Rx4, and a first receiver section 22. The first radar unit RU1 is mounted on a semiconductor chip such as an MMIC.

[0137] The second radar unit RU2 constitutes a second transceiver unit 30, and includes a second transmitter unit 31, an actual transmitting antenna element Tx2, a plurality of actual receiving antenna elements Rx3, Rx4, and Rx5, and a second receiver unit 32. The second radar unit RU2 is implemented on a semiconductor chip such as an MMIC.

[0138] In this embodiment, the transmitting antenna elements Tx1-Tx4 of the first radar unit RU1 and the transmitting antenna elements Tx5-Tx8 of the second radar unit RU2 form a "transmitting antenna group Tx." Additionally, the receiving antenna elements Rx1-Rx4 of the first radar unit RU1 and the receiving antenna elements Rx5-Rx8 of the second radar unit RU2 form a "receiving antenna group Rx." The "transmitting antenna group Tx" and the "receiving antenna group Rx" will be described in detail later.

[0139] The first transmitter 21 of the first radar unit RU1 generates a chirp signal whose frequency changes continuously, and provides the generated chirp signal to the transmitting antenna elements Tx1 to Tx4. The first receiver 22 generates a beat signal based on the received signals received by the receiving antenna elements Rx1 to Rx4 and the local signal transmitted from the first transmitter 21, samples the beat signal, and provides it to the control unit 50.

[0140] The second transmitter 31 of the second radar unit RU2 generates a chirp signal whose frequency changes continuously, and provides the generated chirp signal to the transmitting antenna elements Tx5 to Tx8. The second receiver 32 generates a beat signal based on the signals received by the receiving antenna elements Rx5 to Rx8 and the local signal transmitted from the second transmitter 31, samples the beat signal, and provides it to the control unit 50.

[0141] Next, the group of transmitting antennas Tx and the group of receiving antennas Rx of this example will be described with reference to Fig. 24. Below, the points different from those described in the first embodiment will be mainly described.

[0142] 24, the transmitting antenna group Tx in this example has eight actual transmitting antenna elements Tx1 to Tx8, and the receiving antenna group Rx in this example has eight actual receiving antenna elements Rx1 to Rx8.

[0143] Moreover, the two upper transmitting antenna elements Tx1, Tx2 are spaced apart by an interval equal to the antenna aperture length ("9d" in this example) of the receiving antenna elements Rx1 to R4 plus a reference interval ("4d" in this example) that is a multiple of the horizontal reference distance dh. Specifically, the two upper transmitting antenna elements Tx1, Tx2 are spaced apart by "13dh", which is 13 times the horizontal reference distance dh in the horizontal direction U.

[0144] Similarly, the two lower transmitting antenna elements Tx7 and Tx8 are spaced apart by an interval (13dh 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 receiving antenna elements Rx1 to R4.

[0145] The four transmitting antenna elements Tx3 to Tx6 located approximately in the center include those that are arranged at intervals (13dh 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 receiving antenna elements Rx1 to R4.

[0146] Specifically, the transmitting antenna elements Tx3 and Tx6 at both ends of the horizontal direction U are spaced apart by an interval (13dh in this example) that is the sum of the antenna aperture length of the receiving antenna elements Rx1 to R4 and a reference interval that is a multiple of the horizontal reference distance dh. The transmitting 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 transmitting 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.

[0147] In this manner, the transmitting antenna group Tx of this embodiment includes transmitting antenna elements Tx1 to Tx8 that are arranged at intervals that are a multiple of the horizontal reference distance dh.

[0148] Moreover, the receiving antenna elements Rx1 to Rx4 in the first row and the receiving antenna elements Rx5 to Rx8 in the second row are arranged at intervals of "3dh", which is three times the horizontal reference distance dh. In this way, the receiving antenna group Rx of this embodiment includes receiving antenna elements Rx1 to Rx8 that are arranged at intervals that are multiples of the horizontal reference distance dh.

[0149] In this embodiment, the interval in the horizontal direction U between the first neighboring element NTx and the second neighboring element NRx is set to a first minimum interval which is the smallest among the intervals between the transmitting antenna elements Tx1 to Tx8 and the intervals between the receiving antenna elements Rx1 to Rx8 aligned in the horizontal direction U. The first minimum interval in this example is "2dh".

[0150] Furthermore, in this embodiment, the multiple transmitting antenna elements Tx1 to Tx8 and the multiple receiving antenna elements Rx1 to Rx8 are arranged such that the distance between adjacent antenna elements in the first MIMO antenna is equal to or less than twice the first minimum distance.

[0151] Specifically, as shown in the upper part of Figure 25, the spacing in the horizontal direction U between the transmitting antenna elements Tx1 to Tx3 and Tx6 to Tx8 at both ends of the horizontal direction U is set to "13dh", and the spacing between each adjacent element NTx, NRx is set to "2dh", which is larger than the first minimum spacing.

[0152] According to this, as shown in the lower part of Figure 25, the spacing between virtual antenna elements in the central part of the first MIMO antenna is at most "2dh", and can be limited to less than "4dh", which is twice the first minimum spacing.

[0153] Here, the multiple transmitting antenna elements Tx1 to Tx8 in this embodiment include those arranged at the same interval as the multiple receiving antenna elements Rx1 to Rx8 in the horizontal direction U. Specifically, the interval between the transmitting antenna elements Tx4 and Tx5 in the center part in the horizontal direction U is set to "9dh", which is the same as the antenna aperture length of the multiple receiving antenna elements Rx1 to Rx8. With such an antenna configuration, the first MIMO antenna includes antenna elements that virtually overlap.

[0154] In the virtually overlapping antenna elements, the phases of the received signals basically match. The phase difference of the received signals in the virtually overlapping antenna elements may be caused by individual differences between the first transceiver unit 20 and the second transceiver unit 30.

[0155] Taking this into consideration, the control unit 50 of this embodiment compares the phases of signals received by virtually overlapping antenna elements, and based on the comparison result, compensates for the phase difference between the first transceiver unit 20 and the second transceiver unit 30. In this embodiment, the software and hardware of the control unit 50 that compensates for the phase difference between the multiple transceivers 20, 30 constitutes a "phase compensation unit 54."

[0156] 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.

[0157] Moreover, according to this embodiment, the following effects can be obtained.

[0158] (1) In the radar device 1 of this embodiment, the first MIMO antenna is configured to include virtually overlapping antenna elements. The radar device 1 is configured to compensate for the phase difference between the multiple transceivers 20, 30 based on the reception signals received by the virtually overlapping antenna elements. This makes it possible to suppress deterioration of the detection accuracy of targets caused by the phase difference between the multiple transceivers 20, 30.

[0159] (Modification of the third embodiment) In the third embodiment, the first MIMO antenna is configured to include virtually overlapping antenna elements, but the second MIMO antenna may also be configured to include virtually overlapping antenna elements. Such a configuration can be obtained by aligning a part of the spacing between the transmitting antenna elements Tx1 to Tx8 with the spacing between the receiving antenna elements Rx1 to Rx8.

[0160] As in the third embodiment, the radar device 1 is preferably configured to be capable of compensating for the phase difference between the multiple transmission / reception units 20 and 30, but this is not essential. Also, although the radar device 1 is configured to be capable of compensating for the phase difference between the multiple transmission / reception units 20 and 30 (e.g., a configuration including multiple ICs), the present invention is not limited thereto, and the first transmission / reception unit 20 and the second transmission / reception unit 30 may each be configured to include a single transmission / reception unit (e.g., a configuration including a single IC).

[0161] (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.

[0162] 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. For example, the radar device 1 may have an antenna configuration in which the arrangement of the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8 is reversed. Furthermore, the number of antenna elements constituting the transmitting antenna group Tx and the receiving antenna group Rx is not limited to the above and may be a number different from the above.

[0163] In the above embodiment, the two different directions are the horizontal direction U and the vertical direction V, but they may be different directions. Of the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8, it is preferable that some of the antenna elements on one side are arranged at equal intervals with a reference interval that is multiple times a predetermined reference distance, but this is not necessary. Of the transmitting antenna elements Tx1 to Tx8 and the receiving antenna elements Rx1 to Rx8, it is preferable that some of the antenna elements on the other side are arranged at an interval that is smaller than the reference interval by the reference distance, but this is not necessary.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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]

[0169] 1. Radar equipment 51 First direction estimation part 52 2nd direction estimation part Tx Transmitting antenna group NTx 1st Proximity Element Rx receiving antennas NRx second nearest neighbor

Claims

1. A radar device that detects targets using radio waves, a transmitting antenna group (Tx) including a plurality of transmitting antenna elements arranged in a first direction at intervals that are a multiple of a predetermined first reference distance and arranged in a second direction intersecting the first direction at intervals that are a multiple of a predetermined second reference distance; a receiving antenna group (Rx) including a plurality of receiving antenna elements arranged in the first direction at intervals that are a multiple of the first reference distance and arranged in the second direction at intervals that are a multiple of the second reference distance; a first azimuth estimation unit (51) that estimates an azimuth of a target in the first direction by using the plurality of transmitting antenna elements and the plurality of receiving antenna elements that are arranged in the first direction; a second azimuth estimation unit (52) that estimates an azimuth of a target in the second direction by using the plurality of transmitting antenna elements and the plurality of receiving antenna elements that are arranged in the second direction, Among the plurality of transmitting antenna elements, the one closest to the receiving antenna element is defined as a first neighboring element (NTx), and among the plurality of receiving antenna elements, the one closest to the transmitting antenna element is defined as a second neighboring element (NRx), and the smallest interval between the intervals between the transmitting antenna elements arranged in the first direction and the interval between the receiving antenna elements is defined as a first minimum interval, A radar device, wherein the distance between the first proximity element and the second proximity element in the first direction is set to be equal to or greater than the first minimum distance.

2. 2. The radar device according to claim 1, wherein the plurality of transmitting antenna elements and the plurality of receiving antenna elements are arranged such that a distance between adjacent antenna elements in a first MIMO antenna, which is a MIMO antenna based on a plurality of antenna elements arranged in the first direction, is equal to or less than twice the first minimum distance.

3. When the minimum interval between the interval between the transmitting antenna elements arranged in the second direction and the interval between the receiving antenna elements arranged in the second direction is defined as a second minimum interval, The radar device according to claim 1 , wherein the distance between the first proximity element and the second proximity element in the second direction is set to be equal to or greater than the second minimum distance.

4. 4. The radar device according to claim 3, wherein the plurality of transmitting antenna elements and the plurality of receiving antenna elements are arranged such that a distance between adjacent antenna elements in a second MIMO antenna, which is a MIMO antenna based on a plurality of antenna elements arranged in the second direction, is equal to or less than twice the second minimum distance.

5. 3. The radar device according to claim 2, wherein the first azimuth estimation unit estimates the azimuth of the target in the first direction by using a first extended array antenna including, in addition to a plurality of antenna elements constituting the first MIMO antenna, virtual antenna elements interpolated using a differential signal corresponding to a phase difference between a plurality of antenna elements generated by radio waves arriving from a direction intersecting the first direction.

6. The radar device according to claim 5 , wherein the first azimuth estimation unit performs weighting by window function processing on signals corresponding to antenna elements that configure the first extension array antenna.

7. 5. The radar device according to claim 4, wherein the second azimuth estimation unit estimates the azimuth of the target in the second direction by using a second extended array antenna including, in addition to a plurality of antenna elements constituting the second MIMO antenna, virtual antenna elements interpolated using a differential signal corresponding to a phase difference between a plurality of antenna elements generated by radio waves arriving from a direction intersecting the second direction.

8. The radar device according to claim 7 , wherein the second azimuth estimation unit performs weighting by window function processing on signals corresponding to antenna elements that configure the second extension array antenna.

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