Radar device and method for operating the same

Abstract

In this radar device (100), a signal processing unit (3), which performs a detection process for a target, comprises an R-FFT unit (32a, 32b), a V-FFT unit (33a, 33b), an A-FFT unit (34), a transmission phase control unit (15), a reception phase reference value storage unit (40), and a reception phase correction unit (35). The transmission phase control unit (15) modulates the transmission phase of a transmission chirp signal to a different modulation degree in each transmission channel, and the reception phase reference value storage unit (40) stores a reception phase reference value, which is reception phase information. The reception phase correction unit (35) calculates a change amount for a reception phase of a spectrum, which is obtained by the R-FFT unit (32a, 32b) and the V-FFT unit (33a, 33b), on the basis of the reference phase and the reception phase reference value stored by the reception phase reference value storage unit (40) and reflects the calculated change amount in a process performed by the A-FFT unit (34).

Description

Radar device and radar device operation method

[0001] The present disclosure relates to a radar device that detects targets and a method for operating the radar device.

[0002] The following Patent Document 1 discloses a radar device that can detect faults during operation without using reflected waves from a target by receiving a direct wave that is emitted from a transmission circuit and coupled directly without passing through the target. Such a radar device is already used as a radar device for automobile sensors.

[0003] International Publication No. 2019 / 234946

[0004] Radar devices for automobile sensors generally have other operating modes, such as a target detection mode for detecting target information, a fault detection mode, a performance correction mode, etc. Radar devices with such multiple operating modes have the problem that the operating time increases, which increases the time required to determine whether the radar device has a fault.

[0005] The present disclosure has been made in view of the above, and aims to provide a radar device that can suppress an increase in the time required to determine whether the radar device has a fault, even if the radar device has multiple operation modes.

[0006] To solve the above-mentioned problems and achieve the object, a radar device according to the present disclosure includes multiple transmission channels that generate transmission chirp signals and multiple reception channels that receive reflected waves of the transmission chirp signals emitted from the transmission channels from a target and mix the received signals using a reference signal that forms the basis of the transmission chirp signals. The radar device also includes a signal processing unit that performs target detection processing based on a beat signal mixed by the reception channels. The signal processing unit includes first and second processing units, a transmission phase control unit, a storage unit, and a reception phase correction unit. The first processing unit detects the position and velocity of the target based on the beat signal. The second processing unit detects the azimuth angle of the target based on the beat signal and the processing result of the first processing unit. The transmission phase control unit modulates the transmission phase of the transmission chirp signal with a modulation index that differs for each transmission channel. The storage unit stores a reception phase reference value that is reception phase information. The reception phase correction unit calculates a change in the reception phase based on the reception phase of the spectrum obtained by the first processing unit and the reception phase reference value stored in the storage unit, and reflects the calculated change in the processing of the second processing unit.

[0007] The radar device according to the present disclosure has an advantage that, even if the radar device has a plurality of operation modes, an increase in the time required for fault determination of the radar device can be suppressed.

[0008] FIG. 1 is a block diagram showing a configuration example of a radar device according to a first embodiment; FIG. 2 is a diagram showing a first example of time waveforms of a transmission frequency and a transmission phase in a fault detection mode according to the first embodiment; FIG. 3 is a diagram showing a second example of time waveforms of a transmission frequency and a transmission phase in a fault detection mode according to the first embodiment; FIG. 4 is a diagram showing a spectrum result of received data in an arbitrary one receiving channel corresponding to the waveform shown in FIG. 2; FIG. 5 is a diagram showing a spectrum result of received data in an arbitrary one receiving channel corresponding to the waveform shown in FIG. 3; 1 is a block diagram showing an example of a hardware configuration for realizing the function of the signal processing unit in the first embodiment; FIG. 2 is a block diagram showing another example of a hardware configuration for realizing the function of the signal processing unit in the first embodiment; FIG. 3 is a block diagram showing a configuration of a radar device according to a second embodiment; FIG. 4 is a flowchart explaining the operation of a failure detection mode by a failure detection unit and a transmission amplitude correction mode by a transmission amplitude correction unit in the second embodiment; FIG. 5 is a diagram explaining a method for calculating a transmission amplitude change amount in the transmission amplitude correction mode in the second embodiment;

[0009] A radar device and a method for operating the radar device according to an embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings. In the following embodiments, a radar device for an automobile sensor mounted on an automobile will be described as an example, but this does not mean that application to other uses will be excluded. In the following description, multiple components of the same type will be indicated by reference numerals with subscripts, but the subscripts will be omitted as appropriate when there is no need to distinguish between the individual components. In the following description, the term "connection" will be used without distinguishing between physical and electrical connections. In other words, the term "connection" includes both cases where components are directly connected to each other and cases where components are indirectly connected to each other via other components.

[0010] Embodiment 1. One example of a radar device is an FMCW (Frequency Modulated Continuous Wave) radar. FMCW radar has the advantages of being simple to configure and easy to handle because the frequency band of the transmitted and received beat signals that undergo baseband processing is relatively low. Therefore, it has become widespread as an automobile sensor for preventing automobile collisions. Furthermore, FMCW radar is expected to be used as one of the automobile sensors for autonomous driving in the future. In this FMCW radar, the transmission signal emitted into space includes an up-chirp, which changes the transmission frequency from low to high, and a down-chirp, which changes the transmission frequency from high to low. The FMCW radar calculates the distance, relative velocity, azimuth angle, etc., to a target based on the sum and difference of the peak frequencies of the beat signals obtained from the up-chirp and down-chirp.

[0011] Another example of a radar device is an FCM (Fast Chirp Modulation) radar. In an FCM radar, a transmission signal emitted into space includes either an up-chirp, which modulates the modulation frequency from low to high at high speed, or a down-chirp, which modulates the modulation frequency from high to low at high speed. The FCM radar calculates the distance, relative velocity, azimuth angle, etc. to a target based on information about the frequency and reception phase of a received beat signal resulting from either the up-chirp or down-chirp.

[0012] Unlike FMCW radar, which requires pairing of up-chirp and down-chirp, FCM radar does not require pairing. For this reason, FCM radar places less strain on signal processing and can detect targets with high accuracy, making it popular as an automotive sensor. In the following description of this paper, when there is no need to distinguish between FMCW radar and FCM radar, they will simply be referred to as "radar" or "radar device."

[0013] 1 is a block diagram showing an example of the configuration of a radar device 100 according to embodiment 1. As shown in FIG. 1 , the radar device 100 according to embodiment 1 includes a transmission circuit 1, a reception circuit 2, a signal processing unit 3, and an ambient temperature monitor 6.

[0014] The transmitter circuit 1 includes an RF (Radio Frequency) signal source 11, phase shifters 12a and 12b, amplifiers 13a and 13b, and transmit antennas 14a and 14b. The transmitter circuit 1 transmits signals generated by the RF signal source 11 to the transmit antennas 14a and 14b via the phase shifters 12a and 12b and amplifiers 13a and 13b. The phase shifters 12a and 12b adjust the phases of the input signals. The amplifiers 13a and 13b individually amplify the signals output from the phase shifters 12a and 12b, respectively. The transmit antennas 14a and 14b radiate the signals output from the amplifiers 13a and 13b into space as transmit chirp signals 51. The signal generated by the RF signal source 11 is the basis for the transmit chirp signals 51 and is referred to as a "reference signal" in this document.

[0015] In the transmission circuit 1, a set consisting of one of the phase shifter 12, the amplifier 13, and the transmission antenna 14 constitutes a transmission channel 10. In the first embodiment, the minimum number of transmission channels 10 is two. That is, the radar device 100 according to the first embodiment includes a plurality of transmission channels 10 that generate transmission chirp signals.

[0016] The receiving circuit 2 includes receiving antennas 21a and 21b, mixers 22a and 22b, band pass filters (BPFs) 23a and 23b, and analog-to-digital converters (ADCs) 24a and 24b. The receiving circuit 2 receives, via the receiving antennas 21a and 21b, a reflected wave 52 from a target 41, which is a transmitted chirp signal 51 emitted into space. The mixers 22a and 22b mix the received signals using a reference signal output from the RF signal source 11. The BPFs 23a and 23b apply band pass filtering to the beat signals mixed by the mixers 22a and 22b. The ADCs 24a and 24b perform AD conversion, and the converted signals are transmitted to the signal processing unit 3. As shown in FIG. 1, a direct wave 53 is present that is directly coupled from the transmitting circuit 1 to the receiving circuit 2, and the receiving circuit 2 also receives the direct wave 53 and performs the processing described below.

[0017] In the receiving circuit 2, a set consisting of one receiving antenna 21, one mixer 22, one BPF 23, and one ADC 24 constitutes a receiving channel 20. In the first embodiment, the minimum number of receiving channels 20 is two. That is, the radar device 100 according to the first embodiment includes a plurality of receiving channels 20 that receive reflected waves 52 from a target 41 of a transmission chirp signal radiated from a transmission channel 10, and direct waves 53 that do not pass through the target 41, and mix the received signals using a reference signal that is the basis of the transmission chirp signal.

[0018] The signal processing unit 3 performs a detection process to detect information about the target 41 based on the beat signal mixed by the receiving channel 20. To achieve this function, the signal processing unit 3 includes range-fast Fourier transform (R-FFT) units 32a and 32b, velocity-fast Fourier transform (V-FFT) units 33a and 33b, an azimuth-fast Fourier transform (A-FFT) unit 34, a position / velocity detection unit 39, a transmission phase control unit 15, an amplitude detection unit 36, a fault detection unit 31, a reception phase correction unit 35, and a reception phase reference value storage unit 40.

[0019] The R-FFT units 32a and 32b are processing units that perform a fast Fourier transform in the distance direction, the V-FFT units 33a and 33b are processing units that perform a fast Fourier transform in the velocity direction, and the A-FFT unit 34 is a processing unit that performs a fast Fourier transform in the azimuth angle direction, i.e., the horizontal angle direction. The position / velocity detection unit 39 detects the position, velocity, and azimuth of the target 41 based on the calculation results of the R-FFT units 32a and 32b, the V-FFT units 33a and 33b, and the A-FFT unit 34, and transmits the detection results to the vehicle 150. The R-FFT units 32a and 32b, the V-FFT units 33a and 33b, and the position / velocity detection unit 39 are processing units that detect the position and velocity of the target 41 based on the beat signal, and these processing units may be collectively referred to as the "first processing unit" in this document. In addition, the A-FFT unit 34 and the position / velocity detection unit 39 are processing units that detect the azimuth angle of the target 41 based on the beat signal and the processing results of the first processing unit, and these processing units may be collectively referred to as the "second processing unit" in this document.

[0020] The radar device 100 according to the first embodiment has a target detection mode for detecting target information, a fault detection mode for detecting a fault in the radar device 100, and a performance correction mode for correcting the performance of the radar device 100. The performance correction modes include a reception phase correction mode, a transmission amplitude correction mode, and a transmission phase correction mode. These various correction modes are performed to suppress performance degradation of the radar device 100. It is assumed that the radar device 100 according to the first embodiment has at least the reception phase correction mode in addition to the target detection mode and the fault detection mode.

[0021] The transmission phase control unit 15 individually controls the phase shift amounts of the phase shifters 12a and 12b in the fault detection mode and the reception phase correction mode. Specifically, the transmission phase control unit 15 modulates the transmission phase of the transmission chirp signal with a different modulation factor for each transmission channel 10. That is, the transmission phase control unit 15 applies independent transmission phase modulation to each transmission channel 10. This process utilizes the characteristic that, by applying independent transmission phase modulation to each transmission chirp signal of each transmission channel 10, the spectrum peaks of the received beat signal due to the direct wave 53 occur in different range bins or velocity bins. A range bin is the minimum unit width for identifying the difference in range from a target, and a velocity bin is the minimum unit width for identifying the difference in relative velocity from a target. In a typical radar device, the widths of the range bins and velocity bins are determined by the range and velocity resolution. In a typical radar device, the range bins and velocity bins are assigned numbers, and the range bins and velocity bins are identified by the numbers.

[0022] The amplitude detection unit 36 ​​detects the amplitude of the direct wave 53 based on the amplitude intensity of the spectrum obtained by the R-FFT units 32a and 32b and the V-FFT units 33a and 33b. The fault detection unit 31 determines whether or not there is a fault in the radar device 100 based on the amplitude information obtained by the amplitude detection unit 36, and transmits the determination result to the vehicle 150.

[0023] The reception phase reference value storage unit 40 is a storage unit that stores reception phase reference values, which are reception phase information. The reception phase reference values ​​are reception phases obtained from the spectrum of the direct wave 53 in the R-FFT and V-FFT processes, and are calculated for all reception channels 20. The calculation process of the reception phase reference values ​​is performed in an environment where no reflected wave components from the target 41 are present, for example, during shipping inspection.

[0024] The reception phase correction unit 35 calculates the amount of change in the reception phase based on the reception phase of the spectrum obtained by the R-FFT units 32a, 32b and the V-FFT units 33a, 33b and the reception phase reference value stored in the reception phase reference value storage unit 40, and reflects the calculated amount of change in the processing of the A-FFT unit 34.

[0025] FIG. 2 is a diagram showing a first example of time waveforms of a transmission frequency and a transmission phase in the fault detection mode of the first embodiment, and FIG. 3 is a diagram showing a second example of time waveforms of a transmission frequency and a transmission phase in the fault detection mode of the first embodiment. As shown in the upper part of each diagram, the transmission frequency repeats a time-varying chirp waveform. The "transmission phase (a)" shown in the middle part of each diagram represents the component of the subscript a in FIG. 1 , i.e., the change in the transmission phase imparted to the transmission channel 10 with the subscript a. Furthermore, the "transmission phase (b)" represents the component of the subscript b in FIG. 1 , i.e., the change in the transmission phase imparted to the transmission channel 10 with the subscript b. In the following description, for convenience, the transmission channel 10 with the subscript a may be referred to as "transmission channel a," and the transmission channel 10 with the subscript b may be referred to as "transmission channel b." These names also apply to the reception channel 20. Furthermore, when there is no particular distinction between the transmission channel 10 and the reception channel 20, they may be simply referred to as "channel a" and "channel b."

[0026] In shipping inspection and in a fault detection mode during operation, the transmission phase control unit 15 sets a different transmission phase change width independently for each transmission channel 10 and supplies the set value to the phase shifters 12 a and 12 b to change the transmission phase. Specifically, when the change width of transmission channel a is p and the change width of transmission channel b is q, FIG. 2 shows an example in which the transmission phases of transmission channels a and b are increased stepwise for each chirp period, and FIG. 3 shows an example in which the transmission phases of transmission channels a and b are increased stepwise within the chirp period. Note that the examples in FIGS. 2 and 3 are merely examples, and any method of increasing the transmission phases may be used as long as different transmission phases are independently assigned to transmission channels a and b.

[0027] Fig. 4 is a diagram showing the spectrum result of the received data in any one of the receiving channels 20 corresponding to the waveform shown in Fig. 2, and Fig. 5 is a diagram showing the spectrum result of the received data in any one of the receiving channels 20 corresponding to the waveform shown in Fig. 3. The received data in any one of the receiving channels 20 referred to here is data that has been subjected to R-FFT processing and V-FFT processing and is output from either one of the V-FFT units 33a and 33b in the configuration of Fig. 1. The horizontal axis in Fig. 4 represents speed, the horizontal axis in Fig. 5 represents distance, and the vertical axes in Figs. 4 and 5 represent amplitude.

[0028] When the transmission phase control unit 15 performs the transmission phase modulation of the waveform shown in FIG. 2, as shown in FIG. 4, the TX ａ , TX ｂ The amplitude peaks appear at positions corresponding to the respective modulation indices. The same is true for the example in Figure 5. Therefore, even if transmission signals are transmitted simultaneously from two transmission channels a and b, the two signals can be separated in the velocity frequency domain. Even if there are three or more transmission channels 10, by performing transmission phase modulation with different modulation indices for each, even if transmission signals are transmitted simultaneously from the three or more transmission channels 10, the respective direct wave components can be separated and extracted in the velocity frequency domain.

[0029] In the first embodiment, the amplitude detector 36 detects the amplitude of the direct wave component from each transmission channel 10 and compares it with a set threshold value to determine whether or not the radar device 100 has a malfunction.

[0030] 6 is a flowchart illustrating the operation of the failure detection mode by the failure detection unit 31 and the reception phase correction mode by the reception phase correction unit 35 according to the first embodiment. The failure detection mode and reception phase correction mode shown in FIG. 6 can be activated even during operation of the radar device 100. That is, the operation flow of the failure detection mode and reception phase correction mode shown in FIG. 6 can be performed even when the radar device 100 is in transmission and reception operation.

[0031] The radar device 100 modulates the transmission phase of the transmission chirp signal 51 with a different modulation factor for each transmission channel 10 (step S101), and simultaneously emits the transmission chirp signals 51 from the multiple transmission channels 10 (step S102). Steps S101 and S102 are common to the fault detection mode and the reception phase correction mode.

[0032] Next, the operation of the fault detection mode will be described. The operation of the fault detection mode is shown on the left side of Fig. 6. First, a part of the transmitted chirp signal 51 is received by the receiving circuit 2 as a direct wave 53. The received data output from the receiving circuit 2 is sent to the signal processing unit 3.

[0033] The signal processing unit 3 detects the amplitude of all transmitted direct wave components in all receiving channels 20, i.e., the amplitude of direct wave components radiated from all transmitting channels 10 (step S103). If the amplitude of the direct wave components is greater than the threshold (step S104, Yes), the fault detection unit 31 determines that the radar device 100 is normal (step S105) and ends the fault detection mode. On the other hand, if the amplitude of the direct wave components is equal to or less than the threshold (step S104, No), the fault detection unit 31 determines that a fault has occurred (step S106) and ends the fault detection mode.

[0034] Next, the operation of the reception phase correction mode will be described, which is shown on the right side of FIG.

[0035] The signal processing unit 3 detects the reception phase of the transmission direct wave component radiated from any one of the transmission channels 10 for all of the reception channels 20 (step S107). Then, the signal processing unit 3 calculates the reception phase change amount for all of the reception channels 20 (step S108). The method for calculating the reception phase change amount will be further explained with reference to FIG. 7. FIG. 7 is a diagram illustrating the method for calculating the reception phase change amount in the reception phase correction mode of the first embodiment. Note that the explanation of FIG. 7 assumes that there are two reception channels 20, reception channels a and b, in accordance with the configuration shown in FIG. 1. Also, as described above, it is assumed that reception phase reference values ​​are stored in the reception phase reference value storage unit 40.

[0036] First, as shown in FIG. 7 , the reception phase reference values ​​of reception channels a and b stored in the reception phase reference value storage unit 40 are defined as "θref_a" and "θref_b," respectively. Furthermore, the reception phase detection values ​​of reception channels a and b due to the direct wave component radiated from any one of the transmission channels 10 detected in step S107 are defined as "θdir_a" and "θdir_b." The reception phase detection values ​​can be calculated using data of the peak bin of the spectrum due to the direct wave 53. The peak bin is a velocity bin or distance bin where the peak of the spectrum due to the direct wave 53 appears. Furthermore, the reception phase change amounts in reception channels a and b are defined as "Δθ_a" and "Δθ_b," respectively. As shown in FIG. 7 , the reception phase change amounts Δθ_a and Δθ_b can be calculated using the formulas "Δθ_a = θref_a - θdir_a" and "Δθ_b = θref_b - θdir_b," respectively. That is, the amount of change in the reception phase can be obtained by calculating the difference between the reception phase reference value and the reception phase detection value.

[0037] Returning to the operation flow of FIG. 6, the reception phase correction unit 35 reflects the amount of change in the reception phase calculated in step S108 in the processing of the A-FFT unit 34 (step S109), and ends the reception phase correction mode.

[0038] 6 is determined using the measured value of the direct wave component in an environment where there is no reflected wave component from the target 41, for example, during a shipping inspection. At this time, the direct wave component may be measured while changing the ambient temperature, and a temperature table of threshold values ​​may be created for each transmission channel 10. The ambient temperatures in the temperature table may be set and referenced by correlating the temperature detection value of the ambient temperature monitor 6 with the actual ambient temperature.

[0039] Next, a hardware configuration for realizing the functions of the signal processing unit 3 in the first embodiment will be described with reference to the drawings of Fig. 8 and Fig. 9. Fig. 8 is a block diagram showing an example of a hardware configuration for realizing the functions of the signal processing unit 3 in the first embodiment. Fig. 9 is a block diagram showing another example of a hardware configuration for realizing the functions of the signal processing unit 3 in the first embodiment.

[0040] When the functions of the signal processing unit 3 in embodiment 1 are realized by software, the configuration can include a processor 400 that performs calculations, a memory 402 that is a storage unit in which programs read by the processor 400 are stored, an interface 404 that inputs and outputs signals, and a display 406 that displays the detection results, as shown in Figure 8.

[0041] The processor 400 may be a computing means called an arithmetic unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Examples of the memory 402 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically EPROM), as well as magnetic disks, flexible disks, optical disks, compact disks, minidisks, and DVDs (Digital Versatile Discs).

[0042] The memory 402 stores programs for executing the functions of the signal processing unit 3, as well as threshold values, temperature table values, reception phase reference values, etc. The processor 400 exchanges necessary information via the interface 404, and executes the programs stored in the memory 402. The processor 400 can also execute the processes of the target detection mode, fault detection mode, and performance correction mode described above by referring to the threshold values, temperature table values, and reception phase reference values ​​stored in the memory 402. The calculation results by the processor 400 can be stored in the memory 402. The processing results of the processor 400 can also be displayed on the display 406. The display 406 may be provided outside the signal processing unit 3.

[0043] 8 may be replaced with a processing circuit 403 as shown in Fig. 9. The processing circuit 403 may be a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0044] As described above, in the radar device according to the first embodiment, the signal processing unit that performs target detection processing includes first and second processing units, a transmission phase control unit, a storage unit, and a reception phase correction unit. The first processing unit detects the position and velocity of the target based on the beat signal, and the second processing unit detects the azimuth angle of the target based on the beat signal and the processing result of the first processing unit. The transmission phase control unit modulates the transmission phase of the transmission chirp signal with a different modulation factor for each transmission channel, and the storage unit stores a reception phase reference value, which is reception phase information. The reception phase correction unit calculates a change in the reception phase based on the reception phase of the spectrum obtained by the first processing unit and the reception phase reference value stored in the storage unit, and reflects the calculated change in the processing of the second processing unit. With this radar device configured in this manner, during operation of the radar device, transmission chirp signals used for fault detection of the radar device are simultaneously emitted into space from multiple transmission channels. This makes it possible to suppress an increase in the time required for fault detection of the radar device. Furthermore, according to the radar device of the first embodiment, the processing in the fault detection mode and the processing in the reception phase correction mode, which are performed to suppress performance degradation of the radar device, can be performed simultaneously in parallel using the same processing flow. This allows the processing in the fault detection mode and the reception phase correction mode to be performed in a short time while the radar device is in operation. Since the processing in multiple operation modes can be performed in a short time, the power consumption of the radar device can be reduced.

[0045] Furthermore, a radar device operating method according to the first embodiment is a radar device operating method performed using the radar device configured as described above, and can be a process including the following modulation steps, emission steps, amplitude detection steps, and determination steps. In the modulation step, the transmission phase of a transmission chirp signal is modulated with a different modulation factor for each transmission channel. In the emission step, the transmission chirp signals generated in the modulation step are simultaneously emitted into space from multiple transmission channels. In the amplitude detection step, direct waves of the transmission chirp signals emitted in the emission step are received, and the amplitudes of the transmission direct wave components of all transmission channels are detected by all reception channels. In the determination step, a fault in the radar device is determined based on a comparison result between the amplitudes of the transmission direct wave components detected in the amplitude detection step and a preset threshold. Such a radar device operating method including the modulation step, emission step, amplitude detection step, and determination steps can prevent an increase in the time required to determine a fault in the radar device.

[0046] The radar device operation method according to the first embodiment may include the following phase detection step, calculation step, and reflection step in addition to the above-described modulation step, emission step, amplitude detection step, and determination step. In the phase detection step, a direct wave of the transmitted chirp signal emitted in the emission step is received, and the received phase of any one of the transmitted direct wave components is detected in all reception channels. In the calculation step, a received phase change amount is calculated based on the detected value of the received phase detected in the phase detection step and a previously stored received phase reference value. In the reflection step, the received phase change amount calculated in the calculation step is reflected in the target detection process. According to this radar device operation method further including the phase detection step, calculation step, and reflection step, a fault detection process of the radar device and a received phase correction process performed to suppress performance degradation of the radar device can be simultaneously performed in parallel using the same processing flow. This allows these multiple processes to be performed in a short time during operation of the radar device. Furthermore, since processes in multiple operating modes can be performed in a short time, the power consumption of the radar device can be reduced.

[0047] Second Embodiment It is known that in radar devices, the amplitude characteristics of transmission signals vary significantly due to manufacturing variations in semiconductor elements on integrated circuits that make up transmission channels, fluctuations in power supply voltage, changes in ambient temperature, and the like. When the amplitude characteristics of transmission signals vary, amplitude differences occur between the signal paths of multiple transmission channels, reducing the detection accuracy of the target's distance, relative velocity, azimuth angle, and the like. In a second embodiment, a configuration and method are proposed that reduce the effects of amplitude differences that may occur between the signal paths of multiple transmission channels.

[0048] Fig. 10 is a block diagram showing the configuration of a radar device 200 according to embodiment 2. Of the components shown in Fig. 10, those that achieve the same functions as those of the radar device 100 according to embodiment 1 shown in Fig. 1 are given the same reference numerals, and overlapping descriptions will be omitted as appropriate.

[0049] 10, in a radar device 200 according to the second embodiment, the signal processing unit 3 shown in Fig. 1 is replaced with a signal processing unit 3A. In the signal processing unit 3A shown in Fig. 10, the reception phase correction unit 35 in the signal processing unit 3 shown in Fig. 1 is replaced with a transmission amplitude correction unit 43, and the reception phase reference value storage unit 40 is replaced with a transmission amplitude reference value storage unit 44. In addition, a transmission amplitude control unit 42 is added to the signal processing unit 3A shown in Fig. 10.

[0050] The transmission amplitude reference value storage unit 44 is a memory unit that stores a transmission amplitude reference value, which is amplitude information of a transmission signal. The transmission amplitude reference value is amplitude information of a transmission signal obtained from the spectrum of a direct wave 53 in R-FFT and V-FFT processing, and is calculated in at least one reception channel 20. The calculation process of the transmission amplitude reference value is performed in an environment where no reflected wave components from a target 41 are present, for example, during a shipping inspection.

[0051] The transmission amplitude correction unit 43 calculates the amount of change in the transmission amplitude based on the transmission amplitude, which is the amplitude information of the spectrum obtained by the R-FFT units 32a, 32b and the V-FFT units 33a, 33b, and the transmission amplitude reference value stored in the transmission amplitude reference value storage unit 44, and reflects the calculated amount of change in the processing of the transmission amplitude control unit 42.

[0052] The transmission amplitude control unit 42 controls the amplification factors of the amplifiers 13a and 13b in accordance with the amount of change in the transmission amplitude calculated by the transmission amplitude correction unit 43, thereby changing the amplitude of the transmission chirp signal during operation.

[0053] Next, the operation of the radar device 200 according to the second embodiment will be described with reference to Fig. 10 and Fig. 11. Fig. 11 is a flowchart illustrating the operation of the failure detection mode by the failure detection unit 31 and the transmission amplitude correction mode by the transmission amplitude correction unit 43 according to the second embodiment. The failure detection mode and the transmission amplitude correction mode shown in Fig. 11 can be activated even while the radar device 200 is in operation. That is, the operation flow of the failure detection mode and the transmission amplitude correction mode shown in Fig. 11 can be performed even when the radar device 200 is in transmission and reception operation.

[0054] The radar device 200 modulates the transmission phase of the transmission chirp signal 51 with a different modulation factor for each transmission channel 10 (step S101), and simultaneously emits the transmission chirp signals 51 from the multiple transmission channels 10 (step S102). Steps S101 and S102 are common to the fault detection mode and the transmission amplitude correction mode. The left side of Fig. 11 shows the operation flow for the fault detection mode, but the processing of steps S103 to S106 is the same as that shown on the left side of Fig. 6, and therefore a description thereof will be omitted here.

[0055] Next, the operation of the transmission amplitude correction mode will be described, which is shown on the right side of FIG.

[0056] The signal processing unit 3A detects the transmission amplitude of the transmission direct wave components radiated from all the transmission channels 10 using any one of the reception channels 20 (step S110). Then, the signal processing unit 3A calculates the transmission amplitude change amount for all the transmission channels 10 (step S111). The method for calculating the transmission amplitude change amount will be further described with reference to FIG. 12. FIG. 12 is a diagram illustrating the method for calculating the transmission amplitude change amount in the transmission amplitude correction mode of the second embodiment. Note that the description of FIG. 12 assumes that there are two transmission channels 10, transmission channels a and b, in accordance with the configuration shown in FIG. 1. Also, as described above, it is assumed that the transmission amplitude reference value storage unit 44 stores transmission amplitude reference values.

[0057] First, as shown in FIG. 12 , the transmission amplitude reference values ​​of transmission channels a and b stored in the transmission amplitude reference value storage unit 44 are defined as "Aref_a" and "Aref_b," respectively. Furthermore, the transmission amplitude detection values, which are the detection values ​​of reception channel a or reception channel b, which is any one reception channel 20, due to the direct wave components radiated from all transmission channels a and b, detected in step S110, are defined as "Adir_a" and "Adir_b." The transmission amplitude detection values ​​can be obtained using data of the peak bin of the spectrum due to the direct wave 53. The peak bin is the velocity bin or distance bin where the peak of the spectrum due to the direct wave 53 appears. Furthermore, the transmission amplitude change amounts in transmission channels a and b are defined as "ΔA_a" and "ΔA_b," respectively. The transmission amplitude variations ΔA_a and ΔA_b can be calculated using the formulas "ΔA_a=Aref_a-Adir_a" and "ΔA_b=Aref_b-Adir_b," respectively, as shown in Fig. 12. That is, the transmission amplitude variations can be calculated by calculating the difference between the transmission amplitude reference value and the transmission amplitude detection value.

[0058] Returning to the operation flow of FIG. 11, the transmission amplitude correction unit 43 reflects the amount of change in transmission amplitude calculated in step S111 in the processing of the transmission amplitude control unit 42 (step S112), and ends the transmission amplitude correction mode.

[0059] As described above, in the radar device according to the second embodiment, the signal processing unit that performs target detection processing includes first and second processing units, a transmission phase control unit, a storage unit, a transmission amplitude correction unit, and a transmission amplitude control unit. The first processing unit detects the position and velocity of the target based on the beat signal, and the second processing unit detects the azimuth angle of the target based on the beat signal and the processing result of the first processing unit. The transmission phase control unit modulates the transmission phase of the transmission chirp signal with a different modulation factor for each transmission channel, and the storage unit stores a transmission amplitude reference value, which is amplitude information of the transmission signal. The transmission amplitude correction unit calculates the amount of change in transmission amplitude based on the reception phase of the spectrum obtained by the first processing unit and the transmission amplitude reference value stored in the storage unit. The transmission amplitude control unit controls the change in the amplitude of the transmission chirp signal based on the amount of change in transmission amplitude calculated by the transmission amplitude correction unit. With this radar device configured in this way, transmission chirp signals used for radar device fault detection are simultaneously emitted into space from multiple transmission channels during operation of the radar device. This makes it possible to suppress an increase in the time required for radar device fault detection. Furthermore, according to the radar device of the second embodiment, the processing in the fault detection mode and the processing in the transmission amplitude correction mode, which are performed to suppress performance degradation of the radar device, can be performed simultaneously in parallel using the same processing flow. This allows the processing in the fault detection mode and the transmission amplitude correction mode to be performed in a short time while the radar device is in operation. Since the processing in multiple operation modes can be performed in a short time, the power consumption of the radar device can be reduced.

[0060] Furthermore, a radar device operating method according to a second embodiment is a radar device operating method performed using the radar device configured as described above. In addition to the modulation step, emission step, amplitude detection step, and determination step described in the first embodiment, the method can also include the following amplitude detection step, calculation step, and amplitude control step. In the amplitude detection step, a direct wave of the transmission chirp signal emitted in the emission step is received, and the transmission amplitude of the transmission direct wave components of all transmission channels is detected in any one reception channel. In the calculation step, a transmission amplitude change amount is calculated based on the detected value of the transmission amplitude detected in the amplitude detection step and a pre-stored transmission amplitude reference value. In the amplitude control step, the transmission amplitude change amount calculated in the calculation step is reflected in amplitude control of the transmission chirp signal emitted in the emission step. According to this radar device operating method further including the amplitude detection step, calculation step, and amplitude control step, a fault detection process for the radar device and a transmission amplitude correction process for suppressing performance degradation of the radar device can be performed simultaneously in parallel using the same processing flow. This allows these multiple processes to be performed in a short time during operation of the radar device. Furthermore, since processing in a plurality of operation modes can be performed in a short time, the power consumption of the radar device can be reduced.

[0061] Third Embodiment It is known that in radar devices, the phase characteristics of transmission signals vary significantly due to manufacturing variations in semiconductor elements on integrated circuits that constitute transmission channels, fluctuations in power supply voltage, changes in ambient temperature, and the like. When the phase characteristics of transmission signals vary, phase differences occur between the signal paths of multiple transmission channels, reducing the detection accuracy of target distance, relative velocity, azimuth angle, and the like. In a third embodiment, a configuration and method are proposed that reduce the effects of phase differences that may occur between the signal paths of multiple transmission channels.

[0062] Fig. 13 is a block diagram showing the configuration of a radar device 300 according to embodiment 3. Of the components shown in Fig. 13, those that achieve the same functions as those of the radar device 100 according to embodiment 1 shown in Fig. 1 are denoted by the same reference numerals, and overlapping descriptions will be omitted where appropriate.

[0063] 13, in a radar device 300 according to the third embodiment, the signal processing unit 3 shown in Fig. 1 is replaced with a signal processing unit 3B. In the signal processing unit 3B shown in Fig. 13, the reception phase correction unit 35 in the signal processing unit 3 shown in Fig. 1 is replaced with a transmission phase correction unit 45, and the reception phase reference value storage unit 40 is replaced with a transmission phase reference value storage unit 46.

[0064] The transmission phase reference value storage unit 46 is a storage unit that stores a transmission phase reference value, which is transmission phase information. The transmission phase reference value is phase information of a transmission signal obtained from the spectrum of a direct wave 53 in R-FFT and V-FFT processing, and is calculated in at least one reception channel 20. The calculation process of the transmission phase reference value is performed in an environment where no reflected wave components from a target 41 are present, for example, during shipping inspection.

[0065] The transmission phase correction unit 45 calculates the amount of change in the transmission phase based on the transmission phase, which is the phase information of the spectrum obtained by the R-FFT units 32a, 32b and the V-FFT units 33a, 33b, and the transmission phase reference value stored in the transmission phase reference value storage unit 46, and reflects the calculated amount of change in the processing of the transmission phase control unit 15.

[0066] The transmission phase control unit 15 controls the phases of the phase shifters 12a and 12b in accordance with the amount of change in the transmission phase calculated by the transmission phase correction unit 45, thereby changing the phase of the transmission chirp signal during operation.

[0067] Next, the operation of the radar device 300 according to the third embodiment will be described with reference to Fig. 13 and Fig. 14. Fig. 14 is a flowchart illustrating the operation of the failure detection mode by the failure detection unit 31 and the transmission phase correction mode by the transmission phase correction unit 45 according to the third embodiment. The failure detection mode and the transmission phase correction mode shown in Fig. 14 can be activated even while the radar device 300 is in operation. That is, the operation flow of the failure detection mode and the transmission phase correction mode shown in Fig. 14 can be performed even when the radar device 300 is in transmission and reception operation.

[0068] The radar device 300 modulates the transmission phase of the transmission chirp signal 51 with a different modulation factor for each transmission channel 10 (step S101), and simultaneously emits the transmission chirp signals 51 from the multiple transmission channels 10 (step S102). Steps S101 and S102 are common to the fault detection mode and the transmission phase correction mode. The left side of Fig. 14 shows the operation flow for the fault detection mode, but the processing of steps S103 to S106 is the same as that shown on the left side of Fig. 6, and therefore a description thereof will be omitted here.

[0069] Next, the operation of the transmission phase correction mode will be described, which is shown on the right side of FIG.

[0070] The signal processing unit 3B detects the transmission phase of the transmission direct wave components radiated from all the transmission channels 10 using any one of the reception channels 20 (step S113). Then, the signal processing unit 3B calculates the transmission phase change amount for all the transmission channels 10 (step S114). The method for calculating the transmission phase change amount will be further described with reference to FIG. 15. FIG. 15 is a diagram illustrating the method for calculating the transmission phase change amount in the transmission phase correction mode of the third embodiment. Note that the description of FIG. 15 assumes that there are two transmission channels 10, transmission channels a and b, in accordance with the configuration shown in FIG. 1. Also, as described above, it is assumed that the transmission phase reference value is stored in the transmission phase reference value storage unit 46.

[0071] First, as shown in FIG. 15 , the transmission phase reference values ​​of transmission channels a and b stored in the transmission phase reference value storage unit 46 are defined as "θTXref_a" and "θTXref_b," respectively. Furthermore, the transmission phase detection values, which are the detection values ​​of reception channel a or reception channel b, which is any one reception channel 20, detected in step S113 due to the direct wave components radiated from all transmission channels a and b, are defined as "θTXdir_a" and "θTXdir_b." The transmission phase detection values ​​can be obtained using data of the peak bin of the spectrum due to the direct wave 53. The peak bin is the velocity bin or distance bin where the peak of the spectrum due to the direct wave 53 appears. Furthermore, the transmission phase change amounts in transmission channels a and b are defined as "θTX_a" and "θTX_b," respectively. The transmission phase change amounts θTX_a and θTX_b can be calculated by the calculation formulas "θTX_a=θTXref_a-θTXdir_a" and "θTX_b=θTXref_b-θTXdir_b," respectively, as shown in Fig. 15. That is, the transmission phase change amount can be calculated by calculating the difference between the transmission phase reference value and the transmission phase detection value.

[0072] Returning to the operation flow of FIG. 14, the transmission phase correction unit 45 reflects the amount of change in the transmission phase calculated in step S114 in the processing of the transmission phase control unit 15 (step S115), and ends the transmission phase correction mode.

[0073] As described above, in the radar device according to the third embodiment, the signal processing unit that performs target detection processing includes first and second processing units, a transmission phase control unit, a storage unit, and a transmission phase correction unit. The first processing unit detects the position and velocity of the target based on the beat signal, and the second processing unit detects the azimuth angle of the target based on the beat signal and the processing result of the first processing unit. The transmission phase control unit modulates the transmission phase of the transmission chirp signal with a different modulation factor for each transmission channel, and the storage unit stores a transmission phase reference value that is phase information of the transmission signal. The transmission phase correction unit calculates a change in the transmission phase based on the reception phase of the spectrum obtained by the first processing unit and the transmission phase reference value stored in the storage unit. The transmission phase control unit controls the phase of the transmission chirp signal based on the change in the transmission phase calculated by the transmission phase correction unit. With this radar device configured in this way, transmission chirp signals used for fault detection of the radar device are simultaneously emitted into space from multiple transmission channels during operation of the radar device. This makes it possible to suppress an increase in the time required for fault detection of the radar device. Furthermore, according to the radar device of the third embodiment, the processing in the fault detection mode and the processing in the transmission phase correction mode, which are performed to suppress performance degradation of the radar device, can be performed simultaneously in parallel using the same processing flow. This allows the processing in the fault detection mode and the transmission phase correction mode to be performed in a short time while the radar device is in operation. Since the processing in multiple operation modes can be performed in a short time, the power consumption of the radar device can be reduced.

[0074] Furthermore, a radar device operating method according to a third embodiment is a radar device operating method performed using the radar device configured as described above. In addition to the modulation step, emission step, amplitude detection step, and determination step described in the first embodiment, the method can also include the following phase detection step, calculation step, and phase control step. In the phase detection step, a direct wave of the transmission chirp signal emitted in the emission step is received, and the transmission phase of the transmission direct wave components of all the transmission channels is detected in any one reception channel. In the calculation step, a transmission phase change amount is calculated based on the detected value of the transmission phase detected in the phase detection step and a pre-stored transmission phase reference value. In the phase control step, the transmission phase change amount calculated in the calculation step is reflected in the phase control of the transmission chirp signal emitted in the emission step. According to this radar device operating method further including the phase detection step, calculation step, and phase control step, a fault detection process for the radar device and a transmission phase correction process for suppressing performance degradation of the radar device can be performed simultaneously in parallel using the same processing flow. This allows these multiple processes to be performed in a short time during operation of the radar device. Furthermore, since processing in a plurality of operation modes can be performed in a short time, the power consumption of the radar device can be reduced.

[0075] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0076] 1 Transmitting circuit, 2 Receiving circuit, 3, 3A, 3B Signal processing unit, 6 Ambient temperature monitor, 10 Transmitting channel, 11 RF signal source, 12a, 12b Phase shifter, 13a, 13b Amplifier, 14a, 14b Transmitting antenna, 15 Transmitting phase control unit, 20 Receiving channel, 21a, 21b Receiving antenna, 22a, 22b Mixer, 31 Fault detection unit, 32a, 32b R-FFT unit, 33a, 33b V-FFT unit, 34 A-FFT unit, 35 Receiving phase correction unit, 36 Amplitude detection unit, 39 Position / speed detection unit, 40 Receiving phase reference value storage unit, 41 Target, 42 Transmitting amplitude control unit, 43 Transmitting amplitude correction unit, 44 Transmitting amplitude reference value storage unit, 45 Transmitting phase correction unit, 46 Transmitting phase reference value storage unit, 51 Transmitted chirp signal, 52 reflected wave, 53 direct wave, 100, 200, 300 radar device, 150 vehicle, 400 processor, 402 memory, 403 processing circuit, 404 interface, 406 display.

Claims

1. A radar device comprising: a plurality of transmission channels that generate transmission chirp signals; a plurality of reception channels that receive reflected waves of the transmission chirp signals emitted from the transmission channels from a target and mix the received signals using a reference signal that is the basis of the transmission chirp signal; and a signal processing unit that performs target detection processing based on the beat signals mixed by the reception channels, wherein the signal processing unit comprises: a first processing unit that detects the position and velocity of the target based on the beat signal; a second processing unit that detects the azimuth angle of the target based on the beat signal and the processing result of the first processing unit; a transmission phase control unit that modulates the transmission phase of the transmission chirp signal with a modulation index that differs for each transmission channel; a memory unit that holds a reception phase reference value that is reception phase information; and a reception phase correction unit that calculates the amount of change in the reception phase based on the reception phase of the spectrum obtained by the first processing unit and the reception phase reference value held in the memory unit, and reflects the calculated amount of change in the processing of the second processing unit.

2. The radar device according to claim 1, further comprising a performance correction mode for correcting the performance of the radar device, wherein in the performance correction mode, the plurality of receiving channels receive direct waves of transmitted chirp signals whose transmission phases are modulated with modulation indices that differ for each of the transmitting channels, and the signal processing unit detects the reception phase of any one of the transmitted direct wave components in all of the receiving channels, calculates the amount of change in the reception phase in all of the receiving channels, and reflects the calculated amount of change in the reception phase in the processing of the second processing unit.

3. A radar device comprising: a plurality of transmission channels that generate transmission chirp signals; a plurality of reception channels that receive reflected waves of the transmission chirp signals radiated from the transmission channels from a target and mix the received signals using a reference signal that is the basis of the transmission chirp signals; and a signal processing unit that detects target information based on the beat signals mixed by the reception channels, wherein the signal processing unit comprises: a first processing unit that detects the position and velocity of the target based on the beat signal; a second processing unit that detects the azimuth angle of the target based on the beat signal and the processing result of the first processing unit; a transmission phase control unit that modulates the transmission phase of the transmission chirp signal with a modulation index that differs for each transmission channel; a memory unit that holds a transmission amplitude reference value, which is amplitude information of the transmission signal; a transmission amplitude correction unit that calculates the amount of change in transmission amplitude based on the reception phase of the spectrum obtained by the first processing unit and the transmission amplitude reference value held in the memory unit; and a transmission amplitude control unit that controls the change in the amplitude of the transmission chirp signal based on the amount of change in transmission amplitude calculated by the transmission amplitude correction unit.

4. The radar device according to claim 3, further comprising a performance correction mode for correcting the performance of the radar device, wherein in the performance correction mode, the plurality of receiving channels receive direct waves of transmitted chirp signals whose transmission phases are modulated with modulation indices that differ for each of the transmitting channels, and wherein the signal processing unit detects the amplitudes of transmitted direct wave components of all of the transmitting channels in any one of the receiving channels, calculates the amount of change in transmission amplitude of all of the transmitting channels, and reflects the calculated amount of change in transmission amplitude in the processing of the transmission amplitude control unit.

5. A radar device comprising: a plurality of transmission channels that generate transmission chirp signals; a plurality of reception channels that receive reflected waves of the transmission chirp signals radiated from the transmission channels from a target and mix the received signals using a reference signal that is the basis of the transmission chirp signals; and a signal processing unit that detects target information based on the beat signals mixed by the reception channels, wherein the signal processing unit comprises: a first processing unit that detects the position and velocity of the target based on the beat signal; a second processing unit that detects the azimuth angle of the target based on the beat signal and the processing result of the first processing unit; a transmission phase control unit that modulates the transmission phase of the transmission chirp signals with a modulation index that differs for each transmission channel; a memory unit that holds a transmission phase reference value that is phase information of the transmission signal; and a transmission phase correction unit that calculates the amount of change in the transmission phase based on the reception phase of the spectrum obtained by the first processing unit and the transmission phase reference value held in the memory unit, wherein the transmission phase control unit controls the change in the phase of the transmission chirp signal based on the amount of change in the transmission phase calculated by the transmission phase correction unit.

6. The radar device according to claim 5, further comprising a performance correction mode for correcting the performance of the radar device, wherein in the performance correction mode, the plurality of receiving channels receive direct waves of transmitted chirp signals whose transmission phases are modulated with modulation indices that differ for each of the transmitting channels, and wherein the signal processing unit detects the reception phase of any one of the transmitted direct wave components in all of the receiving channels, calculates the amount of change in the reception phase in all of the receiving channels, and reflects the calculated amount of change in the reception phase in the processing of the second processing unit.

7. A radar device according to any one of claims 1 to 6, characterized in that it has a fault detection mode for detecting a fault in the radar device, wherein in the fault detection mode, the plurality of receiving channels receive direct waves of transmitted chirp signals whose transmission phases are modulated with different modulation indices for each of the transmitting channels, and the signal processing unit detects the amplitudes of the transmitted direct wave components of all of the transmitting channels in all of the receiving channels, and determines that the device has failed if at least one of the amplitudes of the transmitted direct wave components of all of the transmitting channels is equal to or less than a threshold.

8. A method for operating a radar device comprising a plurality of transmission channels that generate transmission chirp signals, and a plurality of reception channels that receive reflected waves of the transmission chirp signals radiated from the transmission channels from a target and mix the received signals using a reference signal that is the basis of the transmission chirp signals, and that detects target information based on beat signals mixed by the reception channels, the method comprising: a modulation step that modulates the transmission phase of the transmission chirp signals with a modulation index that differs for each transmission channel; a radiation step that radiates the transmission chirp signals generated in the modulation step into space simultaneously from a plurality of the transmission channels; an amplitude detection step that receives direct waves of the transmission chirp signals radiated in the radiation step and detects the amplitudes of the transmission direct wave components of all the transmission channels in all the reception channels; and a determination step that determines a fault in the radar device based on the results of comparing the amplitudes of the transmission direct wave components detected in the amplitude detection step with a preset threshold.

9. A method for operating a radar device according to claim 8, comprising: a phase detection step of receiving the direct wave of the transmitted chirp signal emitted in the emission step and detecting the received phase of any one of the transmitted direct wave components in all of the receiving channels; a calculation step of calculating a received phase change amount based on the detected value of the received phase detected in the phase detection step and a received phase reference value stored in advance; and an reflection step of reflecting the received phase change amount calculated in the calculation step in the target detection process.

10. A method for operating a radar device according to claim 8, comprising: an amplitude detection step of receiving the direct wave of the transmission chirp signal radiated in the radiation step, and detecting the transmission amplitude of the transmission direct wave components of all of the transmission channels in any one of the reception channels; a calculation step of calculating a transmission amplitude change amount based on the detection value of the transmission amplitude detected in the amplitude detection step and a transmission amplitude reference value stored in advance; and an amplitude control step of reflecting the transmission amplitude change amount calculated in the calculation step in amplitude control of the transmission chirp signal radiated in the radiation step.

11. A method for operating a radar device according to claim 8, comprising: a phase detection step of receiving the direct wave of the transmission chirp signal radiated in the radiation step, and detecting the transmission phase of the transmission direct wave components of all of the transmission channels in any one of the reception channels; a calculation step of calculating a transmission phase change amount based on the detection value of the transmission phase detected in the phase detection step and a transmission phase reference value stored in advance; and a phase control step of reflecting the transmission phase change amount calculated in the calculation step in phase control of the transmission chirp signal radiated in the radiation step.

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