Radar device

Abstract

To provide a radar device capable of accurately estimating an azimuth while suppressing the limitation of a configuration.SOLUTION: A radar device for estimating an azimuth of a target includes a transmission section 10, a reception section 20, a main body section P, and a control section 30. The reception section has a first reception antenna 21a and a second reception antenna 22a that receive transmission waves reflected by the target and receive superimposed reflected waves. The control section has: a power profile storage section 322 that stores a first power profile and a second power profile; a power calculation section 313 that obtains first reception power and second reception power; a distance calculation section 314 that obtains the distance between protective members; and an azimuth estimation section 316 that estimates an azimuth. The first reception antenna and the second reception antenna are arranged on the main body section so as to be shifted by a predetermined distance δz in a direction in which the reception section and the protective member face each other. The predetermined distance is set to a value different from a value obtained by multiplying 1 / 4 of the wavelength of the transmission wave by an integer.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Conventionally, a radar device including a transmission unit that transmits radio waves and a reception unit that receives radio waves reflected by a target is known (see, for example, Patent Document 1). The reception unit employed in this radar device has a first array antenna and a second array antenna with equal characteristics, and these first array antenna and second array antenna are arranged with a distance δz shift in the depth direction. The distance δz is set to be equal to or less than 1 / 4 wavelength of the radio wave. Then, the radar device corrects the arrival angle of the estimated radio wave based on the phase difference between the two radio waves caused by the difference in the propagation distances of the two radio waves received by each of the first array antenna and the second array antenna arranged with a distance δz shift.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since the radar device described in Patent Document 1 corrects the arrival angle based on the phase difference between the two radio waves caused by the difference in the propagation distances, it is required that the characteristics of the first array antenna and the second array antenna be equivalent. Further, it is required that the distance δz, which is the shift between the first array antenna and the second array antenna, be equal to or less than 1 / 4 wavelength of the radio wave. Thus, the radar device described in Patent Document 1 needs to have equivalent characteristics of the first array antenna and the second array antenna, and there is a limit to the maximum value of the magnitude of the shift between the first array antenna and the second array antenna.

[0005] In view of the above points, an object of the present disclosure is to provide a radar device capable of accurately estimating an azimuth while suppressing configuration limitations.

Means for Solving the Problems

[0006] According to one aspect of the present disclosure, a radar device that transmits a transmission wave toward a target, receives the transmission wave reflected by the target, and estimates the azimuth of the target includes a transmission unit (10) that transmits a transmission wave, a reception unit (20) that receives the transmission wave reflected by the target, a main body unit (P) where the transmission unit and the reception unit are provided, and a control unit (30) that estimates the arrival angle at the reception unit as the azimuth, The reception unit receives the transmission wave reflected by the target through a protection member (B) that protects the transmission unit disposed at a position facing the transmission unit and the reception unit, and the first reception antenna (21a) and the second reception antenna (22a) that receive a superimposed reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the protection member overlap, The control unit a power profile storage unit (322) that stores a first power profile in which the distance between the protection members, which is the distance between the first reception antenna and the protection member, is associated with the first reception power corresponding to the superimposed reflected wave received by the first reception antenna, and a second power profile in which the distance between the protection members and the second reception power corresponding to the superimposed reflected wave received by the second reception antenna are associated, a power calculation unit (313) that obtains the first reception power corresponding to the superimposed reflected wave and the second reception power corresponding to the superimposed reflected wave, a distance calculation unit (314) that obtains the distance between the protection members based on the first reception power and the second reception power obtained by the power calculation unit, and an azimuth estimation unit (316) that estimates the azimuth based on the distance between the protection members obtained by the distance calculation unit. The first reception antenna and the second reception antenna are arranged on the main body unit with a predetermined distance (δz) shifted in the direction in which the reception unit and the protection member face each other. The predetermined distance is set to a value different from an integral multiple of 1 / 4 of the wavelength of the transmission wave.

[0007] If the configuration is such that the azimuth is estimated based on the distance between the protection members in this way, it is possible to suppress the azimuth estimation error caused by the protection members and accurately estimate the azimuth. And by simply setting the magnitude of the deviation between the first receiving antenna and the second receiving antenna to a value different from an integral multiple of 1 / 4 of the wavelength of the transmission wave, the distance between the protection members can be accurately obtained based on the deviation between the first receiving antenna and the second receiving antenna. Therefore, it is possible to realize a radar device that is not restricted by the characteristics of the first receiving antenna and the second receiving antenna and whose maximum value of the magnitude of the deviation between the first receiving antenna and the second receiving antenna is not restricted.

[0008] Note that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and the specific components etc. described in the embodiments described later.

Brief Description of Drawings

[0009]

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Mode for Carrying Out the Invention

[0010] An embodiment of the present disclosure will be described with reference to FIGS. 1 to 22. In this embodiment, a radar device 1 of the present disclosure is mounted on a vehicle, and an example of being used to detect various targets existing around the vehicle will be described.

[0011] The radar device 1 is disposed, for example, inside a front component of the vehicle, emits radio waves toward the front of the vehicle, and receives radio waves reflected by a target in front of the vehicle, thereby obtaining the distance to the target, the relative speed with respect to the host vehicle, the azimuth with respect to the host vehicle, and the like. In this embodiment, an example will be described in which the radar device 1 is disposed inside a bumper B described later so as not to be directly exposed to the outside and is protected by the bumper B.

[0012] The FMCW method is adopted as the signal modulation method of the radar device 1. The operating frequency of the radio waves of the radar device 1 is set to a frequency band corresponding to millimeter waves (for example, 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.

[0013] As shown in FIG. 1, the radar device 1 includes a transmission unit 10, a reception unit 20, and a control unit 30. The transmission unit 10 has an oscillation unit 11 and a modulation unit 12, and transmits a transmission wave from a transmission antenna 13. The reception unit 20 includes a first reception unit 21, a second reception unit 22, and an MMIC 23. The transmission unit 10, the reception unit 20, and the control unit 30 are formed on a substrate P.

[0014] As shown in FIG. 2, the substrate P has a first stepped portion P1 and a second stepped portion P2 formed in a stepped shape, and is disposed inside the bumper B such that the plate surfaces of the first stepped portion P1 and the second stepped portion P2 face the inner surface of the bumper B. Although not shown, the substrate P is disposed inside the bumper B such that the portion where the transmission unit 10 is formed faces the inner surface of the bumper B. The distance of the first stepped portion P1 from the bumper B is larger than that of the second stepped portion P2.

[0015] In addition, a first receiving unit 21 is formed on the plate surface of the first stepped portion P1 facing the bumper B. A second receiving unit 22 is formed on the plate surface of the second stepped portion P2 facing the bumper B. The first receiving unit 21 has a plurality of first receiving antennas 21a, and these plurality of first receiving antennas 21a are formed on the substrate P. The second receiving unit 22 has a plurality of second receiving antennas 22a, and these plurality of second receiving antennas 22a are formed on the substrate P. The antenna surfaces of the plurality of first receiving antennas 21a and the plurality of second receiving antennas 22a face the bumper B.

[0016] The first receiving unit 21 of the present embodiment has an array configuration in which a plurality of first receiving antennas 21a are arranged side by side on the substrate P. The second receiving unit 22 has an array configuration in which a plurality of second receiving antennas 22a are arranged side by side on the substrate P. The substrate P corresponds to the main body portion provided with the transmission unit 10 and the receiving unit 20. The bumper B corresponds to a protection member that protects the transmission unit 10 and the receiving unit 20. Note that the protection member is not limited to the bumper B, and may be a member different from the bumper B, such as a grille.

[0017] The first receiving unit 21 uses a plurality of first receiving antennas 21a to receive a reflected wave in which a transmitted wave is reflected by a target after passing through the bumper B. The second receiving unit 22 uses a plurality of second receiving antennas 22a to receive a reflected wave in which a transmitted wave is reflected by a target after passing through the bumper B.

[0018] Here, the direction perpendicular to the plate surface of the substrate P is defined as the z direction. The z direction is the direction in which the first receiving antenna 21a of the first receiving unit 21 and the second receiving antenna 22a of the second receiving unit 22 face the bumper B, and is also the direction in which the transmitting unit 10 faces the bumper B. In the present embodiment, the first step portion P1 and the second step portion P2 are formed such that their plate surfaces are displaced from each other by a predetermined distance δz in the z direction. Therefore, the first receiving antenna 21a and the second receiving antenna 22a are formed on the substrate P with a displacement of the distance δz in the z direction.

[0019] In the present embodiment, the distance δz is set to be 1 / 8 of the wavelength of the transmission wave transmitted by the transmitting unit 10. That is, the distance δz is 1 / 8 of the wavelength of the reflected wave received by the first receiving antenna 21a and the second receiving antenna 22a of the receiving unit 20.

[0020] Hereinafter, the distance in the z direction between the first receiving antenna 21a and the bumper B in the radar device 1 is defined as the bumper-to-bumper distance d. The bumper-to-bumper distance d is larger than the distance in the z direction between the second receiving antenna 22a and the bumper B by the distance δz.

[0021] The MMIC 23 converts the signals received by the first receiving antenna 21a and the second receiving antenna 22a respectively into a received signal X in a desired form by processing the received signals. Note that "MMIC" is an abbreviation for Monolithic Microwave Integrated Circuit.

[0022] The control unit 30 constitutes the electronic control unit in the radar device 1. The radar device 1 is a microcomputer including a processor 31 and a storage unit 32. The storage unit 32 includes, for example, ROM, RAM, and EEPROM. Various functions of the microcomputer are realized by executing a computer program stored in the storage unit 32. In this example, the storage unit 32 corresponds to a non-transitory tangible recording medium storing the computer program. Part or all of the functions executed by the processor 31 may be realized by a hardware circuit.

[0023] The processor 31 of this embodiment includes an FFT processing unit 311, a peak extraction unit 312, a power calculation unit 313, a bumper - to - bumper distance calculation unit 314, an array correction unit 315, and a direction estimation unit 316 as shown in FIG. 3. Also, the storage unit 32 of this embodiment includes a calibration matrix storage unit 321 and a power profile storage unit 322 as shown in FIG. 3.

[0024] When each of the first receiving antenna 21a and the second receiving antenna 22a receives a reflected wave, the FFT processing unit 311 performs frequency analysis on each received signal X corresponding to the reflected wave by means of FFT. The peak extraction unit 312 obtains the peak of the frequency of each received signal X from the result of the frequency analysis performed by the FFT processing unit 311 on each received signal X. The power calculation unit 313 calculates each received power corresponding to each received signal X from the peak of the frequency obtained by the peak extraction unit 312. The power profile storage unit 322 stores information on a power profile, which will be described later, that associates each received power calculated by the power calculation unit 313 with the positional relationship of the radar device 1.

[0025] The bumper - to - bumper distance calculation unit 314 calculates the bumper - to - bumper distance d based on each received power calculated by the power calculation unit 313 and the power profile stored in the power profile storage unit 322. The calibration matrix storage unit 321 stores a calibration matrix Q corresponding to the bumper - to - bumper distance d calculated by the bumper - to - bumper distance calculation unit 314. The array correction unit 315 corrects the mode vector based on the calibration matrix Q stored in the calibration matrix storage unit 321 to obtain a corrected mode vector. The direction estimation unit 316 estimates the direction of the target reflecting this reflected wave with respect to the host vehicle using the corrected mode vector obtained by the array correction unit 315 and the received signal X corresponding to the reflected wave. The bumper - to - bumper distance d corresponds to the distance between the protection members. Also, the bumper - to - bumper distance calculation unit 314 corresponds to the distance calculation unit.

[0026] In this embodiment, the processor 31 functions as an FFT processing unit 311, a peak extraction unit 312, a power calculation unit 313, a bumper-to-bumper distance calculation unit 314, an array correction unit 315, and a direction estimation unit 316 by executing a computer program stored in the storage unit 32. Alternatively, the processor 31 may include a plurality of circuit modules corresponding to the FFT processing unit 311, the peak extraction unit 312, the power calculation unit 313, the bumper-to-bumper distance calculation unit 314, the array correction unit 315, and the direction estimation unit 316, respectively. Further, the storage unit 32 functions as a calibration matrix storage unit 321 and a power profile storage unit 322.

[0027] Hereinafter, the processes executed by the FFT processing unit 311, the peak extraction unit 312, the power calculation unit 313, the bumper-to-bumper distance calculation unit 314, the array correction unit 315, the direction estimation unit 316, the power profile storage unit 322, and the calibration matrix storage unit 321 will be described as processes executed by the control unit 30.

[0028] The control unit 30 of this embodiment corrects a mode vector indicating a phase corresponding to the arrival angle of the reflected wave by the processor 31, and estimates the direction using the corrected mode vector, which is the correction result of the mode vector, and the received signal X corresponding to the reflected wave.

[0029] The radar device 1 of this embodiment is configured as a SIMO radar having one transmitting antenna 13. Note that the radar device 1 may be configured as a MIMO radar or a MISO radar having a plurality of transmitting antennas 13. Note that SIMO is an abbreviation for Single Input Multiple Output. MIMO is an abbreviation for Multiple Input Single Output. MISO is an abbreviation for Single Input Multiple Output. Note that a MIMO radar having m transmitting antennas 13 and n first receiving antennas 21a and second receiving antennas 22a can be treated as an equivalent array antenna to a SIMO radar having m×n first receiving antennas 21a and second receiving antennas 22a. Also, a MISO radar having m transmitting antennas 13 and one first receiving antenna 21a and one second receiving antenna 22a can be treated as an equivalent array antenna to a SIMO radar having m first receiving antennas 21a and second receiving antennas 22a.

[0030] Based on the reception result of the signal in the receiving unit 20, the radar device 1 executes a target detection process for estimating the distance to the target, the speed of the target, and the azimuth of the target by the control unit 30. Hereinafter, the target detection process executed by the control unit 30 will be described with reference to FIG. 4. The process shown in FIG. 4 is executed periodically or irregularly by the control unit 30 when a chirp signal is transmitted from the transmitting antenna 13 at a predetermined transmission period.

[0031] As shown in FIG. 4, when the reflected waves from the target are received by the plurality of first receiving antennas 21a and the plurality of second receiving antennas 22a, the control unit 30 receives, in step S10, the reflected waves from the target by the plurality of first receiving antennas 21a and the plurality of second receiving antennas 22a. The control unit 30 individually acquires from the receiving unit 20 the received signal X when the first receiving antenna 21a receives the reflected wave from the target and the received signal X when the plurality of second receiving antennas 22a receive the reflected wave.

[0032] For example, as shown in FIG. 5, the receiving unit 20 of the radar device 1 includes a linear array having L first receiving antennas 21a and second receiving antennas 22a (element positions d 1、 d2, ··· d L ).). Assume that the received signals X from the first receiving antenna 21a and the second receiving antenna 22a in this case are not ideal signals, and various array errors such as mutual coupling between elements, errors due to variations in characteristics (amplitude, phase) of each antenna element, and errors due to the positions of the antenna elements may be included. Each received signal X including such array errors can be modeled, for example, by the mathematical formula F10 in FIG. 6. In the mathematical formula F10, the received signal X is denoted as "X(t)".

[0033] Here, "T" in the mathematical formulas F10 to F13, F15 indicates transpose. "s(t)" in the mathematical formula F12 is a signal vector indicating the complex amplitudes of each of the K incoming waves. "n(t)" in the mathematical formulas F11, F13 is a noise vector composed of noise components with an average of "0" and a variance of thermal noise power at each antenna element. "a(θ K )" is an ideal mode vector corresponding to the K-th incoming wave, and "A" is a mode matrix with "a(θ K )" as columns. The mode vector is a vector indicating the phase corresponding to the arrival angle of the reflected wave. Note that "λ" is the wavelength.

[0034] Also, "Q" in the mathematical formulas F11, F16 is a matrix indicating an error model in the case of including various array errors. In the present embodiment, the matrix indicating the error model is used as a calibration matrix Q for correcting the ideal mode vector.

[0035] When the control unit 30 acquires the received signal X corresponding to the reflected waves received by the first receiving antenna 21a and the second receiving antenna 22a respectively from the receiving unit 20, in step S11, the control unit 30 performs FFT processing on each received signal X. By performing frequency analysis on each received signal X by FFT, the control unit 30 obtains the distance to the target. Also, the control unit 30 performs FFT for each beat frequency component by FFT to obtain the Doppler frequency and obtains the relative speed of the target based on the Doppler frequency. Note that FFT is an abbreviation for Fast Fourier Transform.

[0036] Subsequently, in step S12, the control unit 30 performs FFT peak processing. For example, the control unit 30 detects the frequency bin where a peak occurs in the RV map consisting of the distance and speed obtained by the FFT processing.

[0037] Subsequently, in step S13, the control unit 30 performs array correction processing. The array correction processing is a process of correcting the ideal mode vector to obtain a corrected mode vector taking into account various array errors and the like. In the array correction processing, the ideal mode vector "a(θ)" is corrected using the calibration matrix Q to obtain the corrected mode vector "am(θ)".

[0038] Subsequently, in step S14, the control unit 30 performs azimuth estimation processing.

[0039] Specifically, in the azimuth estimation processing, based on each received signal X, the correlation matrix R shown by Equation F17 in FIG. 6 XX is obtained. Then, the control unit 30 obtains the noise subspace U shown by Equation F18 in FIG. 6 from the eigenvalue decomposition of the correlation matrix R XX Note that "T" in Equation F17 is not the transpose but the number of snapshots. N After that, the control unit 30 has a relationship where the noise subspace U

[0040] and the corrected mode vector "am(θk)" corrected by the calibration matrix Q are orthogonal (that is, am(θk) ⊥ U N N ​The azimuth is estimated by the MUSIC method shown in Equation F19 of FIG. 6 using (k = 1, 2, ··· K). In this MUSIC method, when θ = θk, the denominator of Equation F19 approaches zero, resulting in a very large value. By detecting this peak value, the arrival angle of the reflected wave is estimated as the azimuth of the target. In this embodiment, the azimuth is estimated by the MUSIC method. However, the azimuth estimation is not limited to the MUSIC method and may be realized by other methods such as DBF, Capon, MODE, etc.

[0041] Here, an example of a measurement system for obtaining the calibration matrix Q will be described with reference to FIG. 7. In the measurement system for obtaining the calibration matrix Q, for example, as shown in FIG. 7, a calibration device 40, a rotator 50 for rotating the calibration device 40, and a corner reflector 60 serving as a target are used.

[0042] The calibration device 40 is a device having the same functions as the radar device 1. Note that the calibration device 40 may be a device having the same functions as another radar device 1 different from the radar device 1, or the radar device 1 itself may be adopted.

[0043] In the measurement system for obtaining the calibration matrix Q, the calibration device 40 is rotated to a predetermined angle using the rotator 50 to set the arrival angle of the reflected wave from the corner reflector 60, and the received signal X at that time can be measured by the calibration device 40. When obtaining the calibration matrix Q using such a measurement system, within the field of view angle range of the receiving unit 20, the calibration device 40 is rotated at a predetermined angle step, and the received signal X measured each time is stored as received data in the memory of the calibration device 40. Then, the calibration device 40 obtains the calibration matrix Q based on the received data stored in the memory.

[0044] There are various methods for obtaining the calibration matrix Q. For example, the received signal Xmeans received from a known arrival angle or the signal subspace U obtained from the eigenvalue decomposition of the received signal Xmeans SThere is a method of obtaining a calibration matrix Q using the ideal mode vector determined by the known arrival angle and the noise subspace U obtained from the eigenvalue decomposition of the received signal Xmeans received from the known arrival angle which is the known arrival angle. N There is a method of obtaining a calibration matrix Q using the ideal mode vector determined by the known arrival angle. Note that the received signal Xmeans is the average of the actual received signal X over a predetermined number of snapshots.

[0045] By the way, when the radar device 1 is installed inside the bumper B of the vehicle which is a protection member as in this embodiment, the transmitted wave from the radar device 1 and the reflected wave reflected by the target may be refracted or reflected by the bumper B. Also, a part of the reflected wave reflected by the target may not be received by the radar device 1 but be reflected by the radar device 1 and then be reflected by the inner surface of the bumper B. In this case, the radar device 1 receives the reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the bumper B overlap. Due to these effects, there may occur azimuth-dependent errors such as errors in the amplitude and phase of the received signal X and mutual coupling errors between antennas.

[0046] As a result of the inventors' intensive studies, it has been found that the azimuth-dependent error due to the presence of the bumper B between the radar device 1 and the target changes according to the bumper distance d. Here, as shown in FIG. 8, the inventors conducted an experiment of measuring the estimated error in the estimated azimuth when the radar device 1 received the reflected wave from the corner reflector 60 with the bumper B disposed between the radar device 1 and the corner reflector 60. The bumper B is positioned at a position where the error between the designed value of the bumper distance d and the actual bumper distance d is 1 / 4 or less of the wavelength of the reflected wave. Note that the wavelength of the reflected wave is also the wavelength of the transmitted wave transmitted from the transmitting antenna 13. Hereinafter, the reflected wave in which the reflected wave reflected by the target or the corner reflector 60 and the reflected wave reflected by the bumper B overlap is referred to as a superimposed reflected wave.

[0047] Fig. 9 shows the measurement results of the azimuth estimation error for each bumper-to-bumper distance d and for each azimuth that changes by varying the bumper-to-bumper distance d and the arrival angle of the reflected wave from the corner reflector 60. Note that Figs. 9 and 10 show the respective measurement results when the bumper-to-bumper distance d is changed at intervals of 1.5 mm to 19 mm, 20.5 mm, and 22 mm. As shown in Fig. 9, even when the bumper-to-bumper distance d is constant, the value of the azimuth estimation error increases or decreases as the arrival angle changes. Furthermore, even when the arrival angle is constant, the value of the azimuth estimation error increases or decreases as the bumper-to-bumper distance d changes.

[0048] Also, according to the inventor's intensive study, the received power corresponding to the received signal X of the superimposed reflected wave changes in its power value according to the azimuth at which this reflected wave is received, as shown in Fig. 10. Specifically, when the azimuth of the reflected wave along the z-direction when the radar device 1 receives the superimposed reflected wave is set to zero, regardless of the bumper-to-bumper distance d, it tends to have a mountain shape with the received power when the azimuth is zero as the peak. That is, when the bumper-to-bumper distance d is changed, the received power tends to decrease in its power value as the azimuth of the reflected wave moves away from zero, regardless of any bumper-to-bumper distance d. Note that Figs. 9 and 10 show the respective measurement results when the bumper-to-bumper distance d is set to 19 mm, 20.5 mm, and 22 mm, but similarly, when the bumper-to-bumper distance d is set to 18.5 mm, 19.5 mm, 20 mm, 21 mm, and 21.5 mm, the power value tends to decrease as the azimuth of the reflected wave moves away from zero.

[0049] And as shown in Fig. 9, since the azimuth estimation error changes depending on the bumper-to-bumper distance d, when performing array correction processing using the calibration matrix Q as in this embodiment, it is desirable to use a calibration matrix Q that takes into account the bumper-to-bumper distance d.

[0050] However, when the radar device 1 is attached inside the bumper B, the installation position of the radar device 1 may deviate from the designed position due to manufacturing errors or the like. Then, this bumper-to-bumper distance d will be different from the designed value. Therefore, in order to use the calibration matrix Q that takes into account the bumper-to-bumper distance d, it is necessary to accurately measure the actual measured value of the bumper-to-bumper distance d after the radar device 1 is actually attached inside the bumper B. And it is desirable to perform array correction processing using the calibration matrix Q based on the actually measured value of the bumper-to-bumper distance d.

[0051] Therefore, as shown in FIG. 8, when the radar device 1 receives the superimposed reflected wave, the inventor considered calculating the received power corresponding to the received signal X corresponding to the superimposed reflected wave, and obtaining the actually measured value of the bumper-to-bumper distance d based on the calculated power. And the inventor considered performing array correction processing using the calibration matrix Q based on the actually measured value of the bumper-to-bumper distance d obtained in this way.

[0052] Here, as shown in FIG. 8, when the radar device 1 receives the superimposed reflected wave in which the reflected wave reflected by the corner reflector 60 and the reflected wave reflected by the bumper B overlap, the inventor conducted an experiment to measure the received power of the superimposed reflected wave. In this experiment, the received power of the superimposed reflected wave was calculated when the bumper-to-bumper distance d was changed by 0.5 mm at a time in the range of 10 mm to 18 mm. And the inventor found through this experiment that the received power when receiving the superimposed reflected wave has a periodic characteristic that changes periodically according to the bumper-to-bumper distance d. FIG. 11 shows a part of the experimental results.

[0053] In FIG. 11, for easy viewing of the measurement results, only 6 out of 15 measurement results are shown when the bumper-to-bumper distance d is changed by 0.5 mm at a time in the range of 10 mm to 18 mm. By the way, the operating frequency of the radio wave of the radar device 1 in the present embodiment is 76.5 GHz. That is, the wavelengths of the transmitted wave transmitted and the reflected wave received by the radar device 1 in the present embodiment are approximately 3.92 mm. Therefore, the change amount of the bumper-to-bumper distance d of 0.5 mm when the experiment shown in FIG. 11 was conducted corresponds to approximately 1 / 8 of the wavelengths of the transmitted wave and the reflected wave.

[0054] In FIG. 11, the power values for each azimuth at each bumper-to-bumper distance d when the overlapping reflected wave is received by changing the bumper-to-bumper distance d are shown. Further, in FIG. 12, the change in the power value of the overlapping reflected wave when the azimuth of the reflected wave from the bumper B is zero while changing the bumper-to-bumper distance d by 0.5 mm in the range of 10 mm to 18 mm is shown.

[0055] As shown in FIG. 12, when the azimuth of the overlapping reflected wave is zero and constant, as the bumper-to-bumper distance d increases, the received power changes periodically in terms of its power value. Specifically, as shown in FIG. 12, the received power of the overlapping reflected wave received by the radar device 1 of the present embodiment has a waveform in which one period is approximately 2 mm, where the shape of its power value changes periodically according to the bumper-to-bumper distance d. However, there was a slight increase or decrease in the magnitude of each of the maximum point and the minimum point. That is, the wavelength of the waveform indicated by the received power of the received signal X corresponding to the overlapping reflected wave was approximately half the size of the wavelength of the transmitted wave and the reflected wave, which is 3.92 mm. In other words, every time the bumper-to-bumper distance d changes by approximately half the size of the wavelength of the transmitted wave and the reflected wave, which is 2 mm, the received power of the overlapping reflected wave changes by one period.

[0056] The reason why the received power of the overlapping reflected wave changes by one period every time the bumper-to-bumper distance d changes by 2 mm will be explained. The overlapping reflected wave received by the radar device 1 is a wave in which the reflected wave reflected by the target or the corner reflector 60 and the reflected wave reflected by the bumper B overlap. For this reason, the amplitude of this overlapping reflected wave changes according to the phase of the reflected wave reflected by the target or the corner reflector 60 and the phase of the reflected wave reflected by the bumper B. That is, the power value of the received power corresponding to the received signal X corresponding to the overlapping reflected wave changes according to the phase of the reflected wave reflected by the target or the corner reflector 60 and the phase of the reflected wave reflected by the bumper B.

[0057] For example, when the phases of the reflected waves from the target or the corner reflector 60 and the reflected wave from the bumper B are in phase, the power of the superimposed reflected wave increases because the amplitudes of the reflected waves reinforce each other. On the other hand, when the phases of the reflected waves from the target or the corner reflector 60 and the reflected wave from the bumper B are out of phase, the power of the superimposed reflected wave decreases because the reflected waves cancel each other out. And the amplitude of the reflected wave from the bumper B when received by the radar device 1 changes according to the bumper distance d.

[0058] Also, the reflected wave reflected by the bumper B travels back and forth between the radar device 1 and the bumper B. Therefore, the round-trip distance when the reflected wave travels back and forth between the radar device 1 and the bumper B is twice the bumper distance d. Thus, when the bumper distance d is changed by a predetermined distance, the round-trip distance of the reflected wave reflected by the bumper B is changed by twice the predetermined distance.

[0059] When the round-trip distance of the reflected wave reflected by the bumper B, which changes due to the change in the bumper distance d, is equal to the wavelength of this reflected wave, the power value of the reflected wave reflected by the bumper B when received by the radar device 1 is shifted by one period of the reflected wave. Also, when the round-trip distance of the reflected wave reflected by the bumper B, which changes due to the change in the bumper distance d, is equal to an integer multiple of the wavelength of this reflected wave, the power value of the reflected wave reflected by the bumper B when received by the radar device 1 is shifted by an integer multiple of the period of the reflected wave.

[0060] And, as described above, the wavelength of the transmission wave transmitted by the radar device 1, that is, the wavelength of the reflected wave reflected by the target or the corner reflector 60 and the wavelength of the reflected wave reflected by the bumper B is approximately 4 mm. Therefore, when the bumper distance d gradually changes, the phase state of the reflected wave reflected by the bumper B alternates between an in-phase state and an anti-phase state with respect to the phase of the reflected wave reflected by the target or the corner reflector 60. As a result, the power value of the superimposed reflected wave has a waveform with a wavelength of 4 mm. Therefore, every time the change amount of the bumper distance d changes in integer multiples of 2 mm so that the round-trip distance of the reflected wave reflected by the bumper B becomes an integer multiple of approximately 4 mm, the waveform of the power value of the superimposed reflected wave changes by one cycle of the superimposed reflected wave.

[0061] Here, taking the bumper distance d of 10 mm shown in FIG. 12 as the reference distance, the difference between the value set at a bumper distance d different from the reference distance and the reference distance is defined as the reference distance difference, and the difference in the round-trip distance when the reflected wave travels back and forth between the radar device 1 and the bumper B is defined as the optical path difference. As shown in FIG. 13, when the bumper distance d is 12 mm, the reference distance difference is 2 mm and the optical path difference is 4 mm. Also, when the bumper distance d is 14 mm, the reference distance difference is 4 mm and the optical path difference is 8 mm. And when the bumper distance d is 16 mm, the reference distance difference is 6 mm and the optical path difference is 12 mm. Also, the reference distance difference when the bumper distance d is 18 mm is 8 mm and the optical path difference is 16 mm.

[0062] In this way, when the bumper distance d is changed so that the reference distance difference is a value obtained by multiplying 1 / 2 of the wavelength of the transmission wave by an integer "n" and the optical path difference is a value obtained by multiplying the wavelength of the transmission wave by the integer "n", the power value of the superimposed reflected wave is shifted by n cycles of the waveform of the power value of the superimposed reflected wave. That is, the waveform based on the received power of the superimposed reflected wave including the reflected wave reflected by the bumper B has a periodic characteristic with a wavelength approximately the same as the wavelength of the reflected wave reflected by the bumper B.

[0063] The inventor considered obtaining the measured value of the bumper distance d from the power waveform of the superimposed reflected wave having such periodic characteristics, and performing array correction processing using the calibration matrix Q based on the obtained measured value of the bumper distance d.

[0064] Here, when the radar device 1 is provided inside the bumper B, the measured value of the bumper distance d is 20 mm, and the effect when array correction processing is performed using the calibration matrix Q based on this measured value will be described with reference to FIG. 14. In FIG. 14, the range of the target's viewing angle of the radar device 1 is set to -70° to +70°.

[0065] In FIG. 14, the azimuth estimation error before performing array correction processing in the radar device 1 is indicated by a broken line, and the azimuth estimation error after performing array correction processing using the calibration matrix Q to estimate the azimuth is indicated by a solid line.

[0066] As shown in FIG. 14, the azimuth estimation error before the radar device 1 performs array correction processing was a relatively large value in almost the entire range of the viewing angle. On the other hand, when the radar device 1 performs array correction processing using the calibration matrix Q based on the measured value of the bumper distance d to estimate the azimuth, the azimuth estimated by the radar device 1 was a very small value in the entire range of the viewing angle.

[0067] Subsequently, the difference in the azimuth estimation error when applying a single calibration matrix Q regardless of the bumper distance d will be described with reference to FIG. 15. In FIG. 15, when the actual bumper distance d is 21 mm, the azimuth estimation error when array correction processing is performed using the calibration matrix Q obtained when the bumper distance d is 20 mm is indicated by a dashed-dotted line. Also, in FIG. 15, when the actual bumper distance d is 22 mm, the azimuth estimation error when array correction processing is performed using the calibration matrix Q obtained when the bumper distance d is 20 mm is indicated by a double-dashed-dotted line.

[0068] As described above, when the change amount of the bumper - to - bumper distance d is 2 mm, the round - trip distance of the reflected wave reflected by the bumper B is 4 mm. For this reason, the power value of the superimposed reflected wave received by the radar device 1 is shifted by one cycle. Therefore, when the bumper - to - bumper distance d is 20 mm and 22 mm, the received power of the superimposed reflected wave becomes relatively close values.

[0069] For this reason, even when the actual bumper - to - bumper distance d is 22 mm and array correction processing is performed using the calibration matrix Q obtained when the bumper - to - bumper distance d is 20 mm, the azimuth estimation error is relatively small over the entire range of the viewing angle. In particular, near the azimuth of 0°, the error could be suppressed compared to other azimuths. However, as the azimuth deviates from 0°, the error tends to increase and the correction effect becomes smaller.

[0070] On the other hand, when the change amount of the bumper - to - bumper distance d is 1 mm, the round - trip distance of the reflected wave reflected by the bumper B is 2 mm. For this reason, the power value of the superimposed reflected wave received by the radar device 1 is shifted by approximately half a cycle. Therefore, when the bumper - to - bumper distance d is 20 mm and 21 mm, the received power of the superimposed reflected wave deviates greatly.

[0071] For this reason, even when the actual bumper - to - bumper distance d is 21 mm and array correction processing is performed using the calibration matrix Q obtained when the bumper - to - bumper distance d is 20 mm, it is difficult to suppress the error over the entire range of the viewing angle. For example, near the azimuth of 0°, the error cannot be suppressed, and it is difficult to estimate the azimuth with high precision. Also, at an azimuth away from 0°, the error cannot be suppressed, and it is difficult to estimate the azimuth with high precision.

[0072] Thus, when performing array correction processing using the calibration matrix Q, if the difference in the bumper-to-bumper distance d is a positive multiple of 1 / 2 of the wavelength of the transmitted wave, even when using the calibration matrix Q obtained based on other bumper-to-bumper distances d, the radar device 1 can estimate the azimuth with relatively high accuracy. However, in order to estimate the azimuth with high accuracy over the entire range of the viewing angle, it is desirable to obtain the measured value of the bumper-to-bumper distance d and perform array correction processing using the calibration matrix Q based on the obtained measured value of the bumper-to-bumper distance d to estimate the azimuth.

[0073] However, the received power of the superimposed reflected wave periodically changes its power value according to the bumper-to-bumper distance d. For this reason, even when the bumper-to-bumper distances d are different, there may be cases where the received powers of each other are equal depending on the bumper-to-bumper distance d. Therefore, it is difficult to accurately measure the measured value of the bumper-to-bumper distance d after the radar device 1 is actually mounted on the vehicle by obtaining only one waveform of the received power of the superimposed reflected wave.

[0074] Hereinafter, information in which the bumper-to-bumper distance d as shown in FIG. 12 and the received power of the superimposed reflected wave when the radar device 1 receives the superimposed reflected wave are associated with each other is called a power profile. The power profile is different depending on the characteristics of each linear array included in each of the first receiving unit 21 and the second receiving unit 22 of the radar device 1, and indicates the unique characteristics of each radar device 1. That is, the power profile may be different for each radar device 1 attached to the bumper B.

[0075] Therefore, in the measurement system and the like for obtaining the calibration matrix Q of the present embodiment, the radar device 1 is arranged inside the bumper B so that the bumper-to-bumper distance d is a known distance, and the calibration matrix Q and the power profile are obtained based on the received signal X of the superimposed reflected wave. Then, the radar device 1 obtains the measured value of the bumper-to-bumper distance d when the radar device 1 is actually mounted on the vehicle based on the obtained power profile, and performs array correction based on the obtained bumper-to-bumper distance d.

[0076] Next, the calibration matrix Q and the calibration process for obtaining the power profile of the present embodiment will be described with reference to FIG. 16. This calibration process uses the radar device 1, the rotator 50, and the corner reflector 60. Then, using these radar device 1, rotator 50, and corner reflector 60, the calibration process shown in FIG. 16 is performed. The calibration process is performed before the radar device 1 is actually attached to the vehicle. The bumper B is positioned at a position where the error between the designed value of the bumper-to-bumper distance d and the actual bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave.

[0077] The radar device 1 used in the calibration process is the radar device 1 itself that is actually attached to the vehicle. This is because there may be differences in the respective unique characteristics due to the radar device 1. However, when it has characteristics equivalent to those of the radar device 1 actually attached to the vehicle, a radar device 1 different from the radar device 1 actually attached to the vehicle may be adopted as the radar device 1 used in the calibration process. Alternatively, as the radar device 1 used in the calibration process, a calibration device having functions and characteristics equivalent to those of the radar device 1 actually attached to the vehicle may be adopted.

[0078] In the calibration process, as shown in FIG. 16, in the first step S20, the radar device 1 is arranged inside the bumper B so that the bumper-to-bumper distance d becomes a known distance. Specifically, the radar device 1 is arranged so that the bumper-to-bumper distance d becomes the minimum distance d min This minimum distance d min is set to a value that is assumed to be the smallest bumper-to-bumper distance d when the radar device 1 is installed inside the bumper B, for example. If the designed value of the bumper-to-bumper distance d when the radar device 1 is attached to the bumper B is 15 mm and the bumper-to-bumper distance d may deviate within the range of 10 mm to 20 mm due to factors such as manufacturing errors, the minimum distance d min is 10 mm.

[0079] Then, in step S21, the corner reflector 60 is arranged outside the bumper B so that the reflector distance, which is the distance between the radar device 1 and the corner reflector 60, becomes a predetermined design distance Y. This design distance Y is set to, for example, 5 m based on the radar cross-section (i.e., RCS), which indicates characteristics such as the reflection intensity when the corner reflector 60 reflects the transmission wave from the radar device 1. The design distance Y is set so that the received power becomes a relatively large value when the radar device 1 receives the reflected wave from the corner reflector 60.

[0080] Subsequently, in step S22, the angle of the corner reflector 60 is set so that the angle with respect to the front of the radar device 1 becomes zero when viewed from the corner reflector 60.

[0081] Subsequently, in step S23, the radar device 1 transmits a transmission wave from the transmission antenna 13 toward the corner reflector 60 and measures the received power when the superimposed reflected wave is received. Specifically, the control unit 30 causes the transmission antenna 13 to transmit a chirp signal at a predetermined transmission period. Then, the radar device 1 receives, with a plurality of first reception antennas 21a and second reception antennas 22a, the superimposed reflected wave in which the reflected wave reflected by the corner reflector 60 and the reflected wave that is reflected by the surface of the radar device 1 after being reflected by the corner reflector 60 and then further reflected by the inner surface of the bumper B overlap. The control unit 30 individually acquires the received signal X when the superimposed reflected wave is received by the first reception antenna 21a and the received signal X when the superimposed reflected wave is received by the second reception antenna 22a from the reception unit 20.

[0082] When acquiring each received signal X corresponding to the superimposed reflected waves received by the first receiving antenna 21a and the second receiving antenna 22a from the receiving unit 20, the FFT processing unit 311 of the control unit 30 performs FFT processing on each of these received signals X. Then, the peak extraction unit 312 of the control unit 30 performs FFT peak processing to detect the frequencies at which peaks occur in each received signal X corresponding to the superimposed reflected waves received by the first receiving antenna 21a and the second receiving antenna 22a respectively. When the frequencies at which peaks occur are acquired, the power calculation unit 313 of the control unit 30 calculates the received power of each received signal X corresponding to the superimposed reflected waves received by the first receiving antenna 21a and the second receiving antenna 22a respectively from the signals at the peak frequencies. The power calculation unit 313 transmits information on each power value of the received power of the received signal X corresponding to the superimposed reflected waves received by the first receiving antenna 21a and the second receiving antenna 22a respectively to the calibration matrix storage unit 321 and the power profile storage unit 322. Hereinafter, the received power of the received signal X corresponding to the superimposed reflected wave received by the first receiving antenna 21a is also referred to as the first received power, and the received power of the received signal X corresponding to the superimposed reflected wave received by the second receiving antenna 22a is also referred to as the second received power.

[0083] Incidentally, as described above, the positions of the first receiving antenna 21a and the second receiving antenna 22a with respect to the z direction are offset by a distance δz. And the distance δz in this embodiment is set to be 1 / 8 of the wavelength of the transmitted wave. Specifically, the first receiving antenna 21a and the second receiving antenna 22a are formed with an offset of approximately 0.5 mm in the z direction. In other words, the first receiving antenna 21a and the second receiving antenna 22a are formed with an offset of approximately 1 / 8 of the wavelength of the transmitted wave in the z direction.

[0084] Therefore, the round-trip distance of the reflected wave from the bumper B received by the first receiving antenna 21a is approximately 1 mm longer than the round-trip distance of the reflected wave from the bumper B received by the second receiving antenna 22a. Accordingly, the power value of the superimposed reflected wave received by the first receiving antenna 21a is a value shifted by approximately 1 / 4 cycle with respect to the power value of the superimposed reflected wave received by the second receiving antenna 22a in the waveform of the power of the superimposed reflected wave. That is, the waveforms of the first received power and the second received power are shifted from each other without overlapping their respective periods.

[0085] In step S24, the calibration matrix storage unit 321 stores, as calibration matrix data, the information on the first received power and the second received power received from the power calculation unit 313, which is the measurement result, in association with the bumper distance d set in step S20. Hereinafter, the calibration matrix data in which the first received power is associated with the bumper distance d may be referred to as first calibration matrix data, and the calibration matrix data in which the second received power is associated with the bumper distance d may be referred to as second calibration matrix data.

[0086] The power profile storage unit 322 stores, as power profile data, the information on the first received power and the second received power received from the power calculation unit 313, which is the measurement result, in association with the bumper distance d set in step S20 and the reflector distance set in step S21. Hereinafter, the power profile data in which the first received power is associated with the bumper distance d and the reflector distance may be referred to as first power profile data, and the power profile data in which the second received power is associated with the bumper distance d and the reflector distance may be referred to as second power profile data.

[0087] Subsequently, in step S25, the control unit 30 determines whether or not the bumper distance d is greater than or equal to the maximum distance d max . The maximum distance d max is set to a value assumed to be the maximum bumper distance d when the radar device 1 is installed inside the bumper B. As described above, when there is a position where the bumper distance d deviates within the range of 10 mm to 20 mm due to factors such as manufacturing errors, the maximum distance dmax is 20 mm.

[0088] When it is not determined that the bumper distance d is greater than or equal to the maximum distance d max In step S26, the bumper distance d is increased by a change distance Δd, which is a known distance predetermined from the bumper distance d when the process of step S25 was executed. This change distance Δd is set to a distance that can accurately measure the bumper distance d, such as 0.5 mm.

[0089] Then, the control unit 30, in a state where the bumper distance d is increased by the change distance Δd from the minimum distance d min re-executes the processes of steps S22 to S25. The control unit 30 repeatedly executes the processes of steps S22 to S26 until the bumper distance d becomes greater than or equal to the maximum distance d max And, the control unit 30 changes the bumper distance d by the change distance Δd from the minimum distance d min to the maximum distance d max and stores the first calibration matrix data and the second calibration matrix data based on the received signal X received each time in the calibration matrix storage unit 321. Also, the control unit 30 changes the bumper distance d by the change distance Δd from the minimum distance d min to the maximum distance d max and stores the first power profile data and the second power profile data based on the received signal X received each time in the power profile storage unit 322. When the bumper distance d becomes greater than or equal to the maximum distance d max the control unit 30 ends the calibration process.

[0090] The calibration matrix Q of this embodiment is such that the bumper distance d is changed from the minimum distance d min to the maximum distance d maxIt is obtained based on the first calibration matrix data obtained by making the change up to. And the obtained calibration matrix Q is based on the bumper-to-bumper distance d. Hereinafter, the calibration matrix obtained according to the bumper-to-bumper distance d is shown as the calibration matrix (Q, θ). The calibration matrix (Q, θ) is stored in the calibration matrix storage unit 321. Note that the calibration matrix Q may be obtained based on the second calibration matrix data. In this case, the calibration matrix Q can be obtained based on the bumper-to-bumper distance d and the distance δz.

[0091] Also, by this calibration process, in the power profile storage unit 322, information on the first power profile and the second power profile indicating the characteristics of the radar device 1 as shown in FIG. 12 is stored. The first power profile is information in which information on the bumper-to-bumper distance d before the radar device 1 is actually attached to the vehicle is associated with information on the first received power. The second power profile is information in which information on the bumper-to-bumper distance d before the radar device 1 is actually attached to the vehicle is associated with information on the second received power. And the first power profile and the second power profile are information indicating changes in the first received power and the second received power when the bumper-to-bumper distance d is changed.

[0092] Also, by this calibration process, in the power profile storage unit 322, the first received power including the reflected wave reflected by the bumper B positioned at a position where the error between the design value of the bumper-to-bumper distance d and the actual bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the transmission wave is associated with the bumper-to-bumper distance d. The first power profile is stored. Also, in the power profile storage unit 322, a power profile in which the second received power including the reflected wave reflected by the bumper B positioned at a position where the error between the design value of the bumper-to-bumper distance d and the actual bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the transmission wave is associated with the bumper-to-bumper distance d is stored.

[0093] Subsequently, the measurement process for measuring the bumper-to-bumper distance d after the radar device 1 and the bumper B are actually attached to the vehicle will be described with reference to FIG. In the measurement process, as shown in FIG. 17, in the first step S30, the bumper-to-bumper distance d is the design value ds The radar device 1 is arranged inside the bumper B so as to achieve this. The mounting position when arranging the radar device 1 includes errors such as manufacturing errors when mounting the radar device 1 inside the bumper B. Also, the bumper B is positioned at a location where the error between the designed value d of the bumper-to-bumper distance d s and the actual bumper-to-bumper distance d is equal to or less than 1 / 4 of the wavelength of the transmitted wave.

[0094] Then, in step S31, the corner reflector 60 is arranged outside the bumper B so that the reflector distance becomes a predetermined designed distance Y. This designed distance Y is set to the same value as the designed distance Y in step S21 in the calibration process, for example. Thereby, in step S38 described later, it becomes easier to compare the power value of the received signal X calculated in the calibration process with the power value of the received signal X calculated in the measurement process.

[0095] Note that if it is possible to compare the power value of the received signal X calculated in the calibration process with the power value of the received signal X calculated in the measurement process using the radar cross-section, the designed distance Y in the measurement process may be set to a value different from the designed distance Y in the calibration process.

[0096] Subsequently, in step S32, the angle of the corner reflector 60 is set so that the angle with respect to the front of the radar device 1 becomes zero.

[0097] Subsequently, in step S33, the radar device 1 transmits a transmitted wave from the transmission antenna 13 toward the corner reflector 60 and measures the first received power and the second received power when receiving the superimposed reflected wave. Specifically, the control unit 30 executes the same process as step S23 in the calibration process, and the power calculation unit 313 calculates the power value of the received signal X corresponding to the superimposed reflected wave received by each of the first receiving antenna 21a and the second receiving antenna 22a. The control unit 30 transmits the information on the first received power and the second received power calculated by the power calculation unit 313 to the bumper-to-bumper distance calculation unit 314.

[0098] In step S34, the bumper distance calculation unit 314 stores the information on the first received power and the second received power in association with the bumper distance d set in step S30 and the reflector distance set in step S31.

[0099] Subsequently, in step S35, the control unit 30 calculates the bumper distance d based on the first power profile and the second power profile stored in the power profile storage unit 322 by the bumper distance calculation unit 314, and the first received power and the second received power calculated in step S33.

[0100] The method for calculating the bumper distance d calculated based on the first power profile and the second power profile, and the first received power and the second received power will be described with reference to FIGS. 18 and 19. In FIG. 18, the first power profile in which the first received power is associated with the bumper distance d is shown by a solid line, and the second power profile in which the second received power is associated with the bumper distance d is shown by a dashed line.

[0101] As described above, the first received power corresponding to the received signal X corresponding to the superimposed reflected wave changes periodically according to the bumper distance d. Therefore, as shown in FIG. 18, for example, when the first received power is the power value E1, there are two candidates for the bumper distance d, i.e., the distance D1 and the distance D2. Thus, when there are two candidates for the bumper distance d, the bumper distance calculation unit 314 cannot accurately obtain the bumper distance d based on the information of the first power profile alone.

[0102] In addition, the second received power corresponding to the superimposed reflected wave also periodically varies according to the bumper-to-bumper distance d. The second received power is calculated based on the received signal X corresponding to the superimposed reflected wave received by the second receiving antenna 22a positioned at a distance δz in the z direction from the first receiving antenna 21a. Specifically, the second received power is calculated based on the received signal X corresponding to the superimposed reflected wave received by the second receiving antenna 22a positioned at a distance of approximately 0.5 mm, which is about 1 / 8 of the wavelength of the transmitted wave, in the z direction from the first receiving antenna 21a. For this reason, as described above, the waveforms of the first power profile and the second power profile are shifted by about 1 / 4 cycle. That is, the first power profile and the second power profile are shifted from each other without the periods of their respective waveforms overlapping.

[0103] Therefore, even when there are two candidates for the bumper-to-bumper distance d obtained from the first power profile, based on the second power profile, it is possible to narrow down to one candidate from the bumper-to-bumper distances d with two candidates.

[0104] For example, as shown in FIG. 18, when the first received power is the power value E1 and the second received power is the power value E2, or when it approximates the power value E2, the bumper-to-bumper distance calculation unit 314 determines that the bumper-to-bumper distance d is the distance D1. On the other hand, when the first received power is the power value E1 and the second received power is the power value E3, or when it approximates the power value E3, the bumper-to-bumper distance calculation unit 314 determines that the bumper-to-bumper distance d is the distance D2.

[0105] Therefore, the bumper-to-bumper distance calculation unit 314 can accurately measure the bumper-to-bumper distance d based on the first power profile and the second power profile. Then, array correction processing can be performed using the correction matrix Q based on the accurately measured bumper-to-bumper distance d.

[0106] In this embodiment, the distance δz is set to be 1 / 8 of the wavelength of the transmitted wave. However, the magnitude of the distance δz is not limited to this. For example, if the periods of the waveforms of the first power profile and the second power profile can be shifted from each other without overlapping, the distance δz may be set to a value different from 1 / 8 of the wavelength of the transmitted wave. However, even when the periods of the waveforms of the first power profile and the second power profile do not overlap with each other, if the amount of shift between their waveforms is small, it is difficult to obtain the bumper-to-bumper distance d based on the first power profile and the second power profile.

[0107] Therefore, it is desirable that the distance δz be set so that the waveforms of the first power profile and the second power profile are shifted by about 1 / 4 cycle so as to ensure the amount of shift between the waveforms of the first power profile and the second power profile. For this reason, it is desirable that the distance δz be set so as to satisfy the following Equation 1.

[0108] (Equation 1) δz=(2N - 1)*(λ / 8) Note that "N" in Equation 1 is an integer greater than 1. Also, "λ" in Equation 1 is the magnitude of the wavelength of the transmitted wave. That is, the distance δz is set to a value that is an odd multiple of 1 / 8 of the wavelength of the transmitted wave. In this embodiment, the distance δz is set to a value determined by setting N to the integer 1 in the above Equation 1.

[0109] Here, for example, FIG. 19 shows the first power profile and the second power profile when "N" in Equation 1 is the integer 3. In FIG. 19, the first power profile in which the first received power and the bumper-to-bumper distance d are associated is shown by a solid line, and the second power profile in which the second received power and the bumper-to-bumper distance d are associated is shown by a dashed line.

[0110] As shown in FIG. 19, when the first received power is the power value E4, there are two candidates for the bumper-to-bumper distance d obtained from the first power profile, namely the distance D3 and the distance D4. Even in such a case, when the second received power is the power value E5 or approximates the power value E5, the bumper-to-bumper distance calculation unit 314 determines that the bumper-to-bumper distance d is the distance D3. On the other hand, when the second received power is the power value E6 or approximates the power value E6, the bumper-to-bumper distance calculation unit 314 determines that the bumper-to-bumper distance d is the distance D4.

[0111] Thus, when the distance δz is set to the value obtained by the above formula 1, the bumper-to-bumper distance calculation unit 314 can accurately measure the bumper-to-bumper distance d based on the first power profile data and the second power profile data. Then, array correction processing can be performed using the calibration matrix Q based on the accurately measured bumper-to-bumper distance d.

[0112] Subsequently, the case where the distance δz is set without satisfying the above formula 1 will be described with reference to FIGS. 20 and 21. In FIG. 20, the case where the distance δz is 0, that is, the case where the first receiving antenna 21a and the second receiving antenna 22a are not displaced in the z direction, shows the first power profile and the second power profile. Also, in FIG. 21, the case where the distance δz is 2 / 8 of the wavelength of the transmitted wave shows the first power profile and the second power profile. In FIGS. 20 and 21, the first power profile in which the first received power is associated with the bumper-to-bumper distance d is shown by a solid line, and the second power profile in which the second received power is associated with the bumper-to-bumper distance d is shown by a broken line.

[0113] As shown in FIG. 20, when the first received power is the power value E7, there are two candidates for the bumper-to-bumper distance d obtained from the first power profile, which are the distance D5 and the distance D6. However, when the first receiving antenna 21a and the second receiving antenna 22a are not displaced in the z direction, as shown in FIG. 20, the second power profile has a period that almost overlaps with that of the first power profile. For this reason, in the second power profile, the power values corresponding to the distance D5 and the distance D6 both become the power value E8, or an approximate value of the power value E8. Therefore, it is difficult for the bumper-to-bumper distance calculation unit 314 to accurately measure the bumper-to-bumper distance d based on the first power profile and the second power profile.

[0114] Also, when the distance δz is 2 / 8 of the wavelength of the transmitted wave, that is, when the distance δz is approximately 1 mm, the round-trip distance of the reflected wave from the bumper B received by the first receiving antenna 21a is approximately 2 mm longer than the round-trip distance of the reflected wave from the bumper B received by the second receiving antenna 22a. Therefore, the waveform of the power value of the superimposed reflected wave received by the first receiving antenna 21a is shifted by approximately 1 / 2 cycle with respect to the waveform of the power value of the superimposed reflected wave received by the second receiving antenna 22a. Then, as shown in FIG. 21, the waveforms of the first received power and the second received power each have a shape similar to a shape in which the waveforms of their respective power values are inverted with respect to each other, and the periods substantially overlap.

[0115] And, as shown in FIG. 21, when the first received power is the power value E9, there are two candidates for the bumper-to-bumper distance d obtained from the first power profile, which are the distance D7 and the distance D8. However, as shown in FIG. 21, when the waveforms of the first received power and the second received power are inverted and their periods overlap, the power values corresponding to the distance D7 and the distance D8 in the second power profile both become the power value E10, or an approximate value of the power value E10. Therefore, it is difficult for the bumper-to-bumper distance calculation unit 314 to accurately measure the bumper-to-bumper distance d based on the first power profile and the second power profile.

[0116] Thus, when the periods of the waveforms of the first received power and the second received power overlap with each other, it is difficult to accurately measure the bumper-to-bumper distance d based on the first power profile and the second power profile. Further, when the shapes of the waveforms of the first received power and the second received power are inverted with respect to each other, it is difficult to accurately measure the bumper-to-bumper distance d based on the first power profile and the second power profile. That is, when the distance δz is set to a value that is an integer multiple of 1 / 4 of the wavelength of the transmitted wave, it is difficult to accurately measure the bumper-to-bumper distance d based on the first power profile and the second power profile.

[0117] Therefore, in the radar device 1 of the present embodiment, the distance δz is set to a value different from a value that is an integer multiple of 1 / 4 of the wavelength of the transmitted wave. Specifically, in the radar device 1 of the present embodiment, the distance δz is set to the value obtained by the above equation (1). Thereby, it is possible to sufficiently ensure the amount of deviation of the waveforms of the first power profile and the second power profile respectively. Then, based on the first power profile data and the second power profile data, the bumper-to-bumper distance d can be accurately measured.

[0118] Note that, in the calibration process, in the power profile storage unit 322, the first power profile in which the first received power including the reflected wave reflected by the bumper B positioned at a position where the error between the design value d s and the bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave is associated with the bumper-to-bumper distance d is stored. Further, in the power profile storage unit 322, the second power profile in which the second received power including the reflected wave reflected by the bumper B positioned at a position where the error between the design value d s and the bumper-to-bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave is associated with the bumper-to-bumper distance d is stored.

[0119] And the first power profile and the second power profile change periodically as shown in FIG. 12 and the like. Here, if the design value d of the bumper-to-bumper distance d sAssume that the radar device 1 is mounted inside the bumper B with an error between the actual bumper distance d and the designed bumper distance d being offset by 1 / 4 of the wavelength of the transmitted wave. In this case, when the actual bumper distance d is the designed value d s the waveform of the first power profile and, when the actual bumper distance d is mounted with an offset of 1 / 4 of the wavelength of the transmitted wave from the designed value d s will overlap. In this case, it is difficult for the bumper distance calculation unit 314 to accurately calculate the bumper distance d.

[0120] Also, assume that the radar device 1 is mounted inside the bumper B with an error between the designed value d s of the bumper distance d and the actual bumper distance d being greater than 1 / 4 of the wavelength of the transmitted wave. In this case, the bumper distance calculation unit 314 may calculate a value smaller than 1 / 4 of the wavelength of the transmitted wave, even though the error between the designed value d s and the actual bumper distance d is greater than 1 / 4 of the wavelength of the transmitted wave.

[0121] On the other hand, the power profile storage unit 322 stores a first power profile in which the first received power including the reflected wave reflected by the bumper B positioned at a position where the error between the designed value d s and the bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave is associated with the bumper distance d. Also, the power profile storage unit 322 stores a second power profile in which the second received power including the reflected wave reflected by the bumper B positioned at a position where the error between the designed value d s and the bumper distance d is 1 / 4 or less of the wavelength of the transmitted wave is associated with the bumper distance d. Therefore, the bumper distance calculation unit 314 can accurately calculate the bumper distance d based on the first power profile and the second power profile stored in the power profile storage unit 322.

[0122] Subsequently, the calibration matrix Q and the first power profile obtained in the calibration process, and the array correction based on the bumper distance d calculated in the measurement process will be described with reference to FIG. 22.

[0123] First, in step S40, the bumper - to - bumper distance calculation unit 314 transmits the information of the bumper - to - bumper distance d obtained in the measurement process to the calibration matrix storage unit 321.

[0124] When the calibration matrix storage unit 321 acquires the information of the bumper - to - bumper distance d from the bumper - to - bumper distance calculation unit 314, in step S41, it extracts the calibration matrix Q(θ, d) corresponding to the acquired bumper - to - bumper distance d from the calibration matrix Q(θ, d) obtained in the calibration process. Then, the calibration matrix storage unit 321 outputs the information of the extracted calibration matrix (Q, d) to the array correction unit 315.

[0125] Then, in step S42, the array correction unit 315 performs array correction processing using the calibration matrix Q(θ, d) based on the bumper - to - bumper distance d acquired from the calibration matrix storage unit 321. Specifically, in step S13 shown in FIG. 3, the array correction unit 315 corrects the ideal mode vector "a(θ)" using the calibration matrix Q to obtain the corrected mode vector "am(θ)". By performing such array correction processing, it is possible to suppress the azimuth - dependent error that changes according to the bumper - to - bumper distance d of the bumper B existing between the radar device 1 and the target.

[0126] As described above, the radar device 1 of the present embodiment includes a transmission unit 10 that transmits a transmission wave, a reception unit 20 that receives the transmission wave reflected by a target, a substrate P on which the transmission unit 10 and the reception unit 20 are provided, and a control unit 30 that estimates the arrival angle to the reception unit 20 as an azimuth. The reception unit 20 receives the transmission wave reflected by the target passing through the bumper B disposed at a position facing the transmission unit 10 and the reception unit 20, and has a first reception antenna 21a and a second reception antenna 22a that receive the reflected wave of the transmission wave reflected by the bumper B. The control unit 30 includes a power profile storage unit 322, a power calculation unit 313, a bumper distance calculation unit 314, and an azimuth estimation unit 316. The power profile storage unit 322 stores a first power profile in which the bumper distance d is associated with the first reception power corresponding to the reflected wave received by the first reception antenna 21a, and a second power profile in which the bumper distance d is associated with the second reception power corresponding to the reflected wave received by the second reception antenna 22a. The power calculation unit 313 obtains the first reception power corresponding to the reflected wave and the second reception power corresponding to the reflected wave. The bumper distance calculation unit 314 obtains the bumper distance d based on the first reception power and the second reception power obtained by the power calculation unit 313. The azimuth estimation unit 316 estimates the azimuth based on the bumper distance d obtained by the bumper distance calculation unit 314. The first reception antenna 21a and the second reception antenna 22a are disposed on the substrate P with a distance δz in the z direction. The distance δz is set to a value different from an integral multiple of 1 / 4 of the wavelength of the transmission wave.

[0127] If the configuration is such that the azimuth is estimated based on the bumper distance d in this way, it is possible to suppress the azimuth estimation error caused by the bumper B and accurately estimate the azimuth. And just by setting the distance δz to a value different from an integral multiple of 1 / 4 of the wavelength of the transmission wave, the bumper distance d can be accurately obtained based on this distance δz. Therefore, it is possible to realize the radar device 1 that is not restricted by the characteristics of the first reception antenna 21a and the second reception antenna 22a and the maximum value of the distance δz is not restricted.

[0128] Further, according to the above embodiment, the following effects can be obtained.

[0129] (1) In the above embodiment, when N is an integer of 1 and the wavelength of the reflected wave is λ, the distance δz is set to a value obtained by (2N - 1)λ / 8, which is 1 / 8 of the wavelength of the reflected wave.

[0130] When the distance δz is set in this way, since the waveforms of the first power profile and the second power profile are shifted by about 1 / 4 cycle, it is easy to increase the amount of shift in the waveforms of the first power profile and the second power profile respectively. Therefore, based on the first power profile and the second power profile, it is easy to obtain the bumper interval d.

[0131] (2) In the above embodiment, the receiving unit 20 has an array configuration in which a plurality of first receiving antennas 21a are arranged side by side on the substrate P, and also has an array configuration in which a plurality of second receiving antennas 22a are arranged side by side on the substrate P.

[0132] According to this, by averaging the power values of the reflected waves received by each of the plurality of first receiving antennas 21a and the plurality of second receiving antennas 22a, the variation in the calculated power values can be suppressed.

[0133] (3) In the above embodiment, in the power profile storage unit 322, the first power profile in which the first received power corresponding to the reflected wave reflected by the bumper B positioned at a position where the error between the designed value d s of the bumper interval d and the actual bumper interval d is 1 / 4 or less of the wavelength of the reflected wave is associated with the bumper interval d is stored. Further, in the power profile storage unit 322, the second power profile in which the second received power corresponding to the reflected wave reflected by the bumper B positioned at a position where the error between the designed value d s of the bumper interval d and the actual bumper interval d is 1 / 4 or less of the wavelength of the reflected wave is associated with the bumper interval d is stored.

[0134] As described above, the designed value d sWhen the error between the design value and the actual bumper distance d deviates by more than 1 / 4 of the wavelength of the reflected wave and the radar device 1 is mounted inside the bumper B, it is difficult for the bumper distance calculation unit 314 to accurately calculate the bumper distance d.

[0135] On the other hand, in the power profile storage unit 322, a first power profile in which the first received power corresponding to the reflected wave reflected by the bumper B positioned at a position where the error between the design value d and the bumper distance d is 1 / 4 or less of the wavelength of the reflected wave is associated with the bumper distance d is stored. Further, in the power profile storage unit 322, a second power profile in which the second received power corresponding to the reflected wave reflected by the bumper B positioned at a position where the error between the design value d and the bumper distance d is 1 / 4 or less of the wavelength of the reflected wave is associated with the bumper distance d is stored. Therefore, the bumper distance calculation unit 314 can accurately calculate the bumper distance d based on the first power profile and the second power profile stored in the power profile storage unit 322. s and the bumper distance d is stored. Further, in the power profile storage unit 322, a second power profile in which the second received power corresponding to the reflected wave reflected by the bumper B positioned at a position where the error between the design value d and the bumper distance d is 1 / 4 or less of the wavelength of the reflected wave is associated with the bumper distance d is stored. Therefore, the bumper distance calculation unit 314 can accurately calculate the bumper distance d based on the first power profile and the second power profile stored in the power profile storage unit 322. s and the bumper distance d is stored. Therefore, the bumper distance calculation unit 314 can accurately calculate the bumper distance d based on the first power profile and the second power profile stored in the power profile storage unit 322.

[0136] (Other Embodiments) As described above, representative embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above-described embodiments and can be variously modified as follows, for example.

[0137] In the above-described embodiment, an example in which the transmitting unit 10 and the receiving unit 20 are formed on the substrate P in the radar device 1 has been described. However, the present disclosure is not limited to this. For example, the radar device 1 may be configured to have an array antenna using a waveguide for the transmitting unit 10 and the receiving unit 20.

[0138] In the above-described embodiment, an example in which the receiving unit 20 has an array configuration in which a plurality of first receiving antennas 21a are arranged side by side on the substrate P and an array configuration in which a plurality of second receiving antennas 22a are arranged side by side on the substrate P has been described. However, the present disclosure is not limited to this. For example, the receiving unit 20 may have a configuration in which a single first receiving antenna 21a and a single second receiving antenna 22a are formed on the substrate P.

[0139] In the above-described embodiment, an example in which the distance δz is set to a value obtained by (2N - 1)*λ / 8 has been described, but the present invention is not limited thereto. As long as the value is different from an integral multiple of 1 / 4 of the wavelength of the transmitted wave, the distance δz may be set to a value different from the value obtained by (2N - 1)*λ / 8.

[0140] In the above-described embodiment, the z-direction distance between the first receiving antenna 21a and the bumper B is defined as the bumper interval d, and each configuration and each control process have been described based on the z-direction distance between the first receiving antenna 21a and the bumper B. However, the present invention is not limited thereto. For example, the z-direction distance between the second receiving antenna 22a and the bumper B may be defined as the bumper interval d, and each configuration may be arranged based on the z-direction distance between the second receiving antenna 22a and the bumper B, and each control process may be executed.

[0141] In the above-described embodiment, an example in which the radar device 1 of the present disclosure is mounted on a vehicle and detects various targets existing around the vehicle has been described, but the present invention is not limited thereto. The radar device 1 may be installed in devices or objects other than vehicles.

[0142] In the above-described embodiment, it goes without saying that the elements constituting the embodiment are not necessarily essential, except in cases where it is explicitly stated that they are particularly essential and cases where they are considered to be clearly essential in principle.

[0143] In the above-described embodiment, when numerical values such as the number, numerical value, quantity, and range of the components of the embodiment are mentioned, they are not limited to the specific number, except in cases where it is explicitly stated that they are particularly essential and cases where they are clearly limited to a specific number in principle.

[0144] In the above-described embodiments, when referring to the shape, positional relationship, etc. of components and the like, unless otherwise specified or limited to a specific shape, positional relationship, etc. in principle, it is not limited to such shape, positional relationship, etc.

[0145] The control unit 30 and its method of the present disclosure may be implemented by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied by a computer program. The control unit 30 and its method of the present disclosure may be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. The control unit 30 and its method of the present disclosure may be implemented by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured by one or more hardware logic circuits. Further, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

Explanation of Reference Numerals

[0146] 10 Transmission unit 20 Reception unit 30 Control unit 21a First reception antenna 22a Second reception antenna 313 Power calculation unit 314 Distance calculation unit 316 Azimuth estimation unit 322 Power profile storage unit B Protection member

Claims

1. A radar device that transmits a transmission wave toward a target, receives the transmission wave reflected by the target, and estimates the azimuth of the target, comprising: a transmission unit (10) that transmits the transmission wave; a reception unit (20) that receives the transmission wave reflected by the target; a main body unit (P) where the transmission unit and the reception unit are provided; a control unit (30) that estimates the arrival angle at the reception unit as the azimuth, and the reception unit receives the transmission wave reflected by the target through a protection member (B) that protects the transmission unit disposed at a position facing the transmission unit and the reception unit, and the reception unit has a first reception antenna (21a) and a second reception antenna (22a) that receive a superimposed reflected wave in which the reflected wave reflected by the target and the reflected wave reflected by the protection member overlap; the control unit a power profile storage unit (322) that stores a first power profile in which a protection member distance, which is the distance between the first reception antenna and the protection member, is associated with a first reception power corresponding to the superimposed reflected wave received by the first reception antenna, and a second power profile in which the protection member distance is associated with a second reception power corresponding to the superimposed reflected wave received by the second reception antenna; a power calculation unit (313) that obtains the first reception power corresponding to the superimposed reflected wave and the second reception power corresponding to the superimposed reflected wave; a distance calculation unit (314) that obtains the protection member distance based on the first reception power and the second reception power obtained by the power calculation unit; an azimuth estimation unit (316) that estimates the azimuth based on the protection member distance obtained by the distance calculation unit, and the first reception antenna and the second reception antenna are arranged in the main body unit with a predetermined distance (δz) shifted in a direction in which the reception unit and the protection member face each other, the radar device in which the predetermined distance is set to a value different from an integer multiple of 1 / 4 of the wavelength of the transmission wave.

2. The radar device according to claim 1, wherein the predetermined distance is set to a value obtained by (2N - 1)λ / 8, where N is an integer of 1 or more and λ is the wavelength.

3. The radar device according to claim 1, wherein the reception unit has an array configuration in which a plurality of the first reception antennas are arranged side by side in the main body unit, and an array configuration in which a plurality of the second reception antennas are arranged side by side in the main body unit.

4. In the power profile storage unit, the first power profile in which the first received power corresponding to the superimposed reflected wave including the reflected wave reflected by the protection member positioned at a position where the error between the design value of the distance between the protection members and the distance between the protection members is 1 / 4 or less of the wavelength is associated with the distance between the protection members is stored, and the second received power corresponding to the superimposed reflected wave including the reflected wave reflected by the protection member positioned at a position where the error between the design value of the distance between the protection members and the distance between the protection members is 1 / 4 or less of the wavelength is associated with the distance between the protection members. The radar device according to claim 1, wherein the second power profile is stored.

5. The control unit includes an array correction unit (315) that corrects a mode vector indicating a phase corresponding to the arrival angle of the superimposed reflected wave using a correction matrix. The array correction unit corrects the mode vector using the correction matrix based on the distance between the protection members obtained by the distance calculation unit. The azimuth estimation unit estimates the azimuth using the corrected mode vector, which is the correction result of the mode vector by the array correction unit, and the reception signal corresponding to the superimposed reflected wave received by the first reception antenna and the second reception antenna. The radar device according to claim 1.

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