Radar system, radar control device, radar control method, and radar control program

Abstract

A processor of this radar system is configured to transmit, in addition to the shift amount and from each transmission antenna, a transmission signal having an initial phase that has been changed in accordance with the transmission antenna. The processor is configured to set a candidate of the correspondence relationship between a plurality of peaks and the plurality of transmission antennas in a speed spectrum defined by reception signals obtained via the reception of transmission signals from the plurality of transmission antennas by a reception antenna. When the phase difference between the peaks correlated with the spatial disposition of the transmission antennas is confirmed by the combination of the peak corresponding to the candidate and the initial phase, the processor is configured to output sensing data correlated with the reception signals in which the correspondence relationship by the candidate is defined.

Description

Radar system, radar control device, radar control method, and radar control program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2024-62386 filed in Japan on April 8, 2024, the contents of which are incorporated by reference in their entirety.

[0002] The present disclosure relates to a radar control technique for controlling a radar system.

[0003] Patent Document 1 discloses a radar device that performs phase shift keying (PSK) on multiple transmission signals input to multiple transmission antennas, rotating the phases of each signal by different amounts of phase rotation for each repetition period. The radar device sets the number of phases used for PSK to be greater than the number of transmission antennas. As a result, the radar device unevenly arranges peaks based on the transmission signals on a Doppler spectrum obtained by analyzing the received signals. The radar device identifies the correspondence between the multiple peaks and the multiple transmission antennas by using the uneven arrangement of peaks on the Doppler spectrum as a clue.

[0004] Patent No. 6881177

[0005] However, the Doppler spectrum may contain peaks derived from signal components other than the normal transmission signal. When these peaks are lined up alongside the normal peaks, it may be difficult to accurately identify the correspondence between the multiple peaks and the multiple transmitting antennas. In this case, an incorrect correspondence may be selected, resulting in erroneous detection.

[0006] An object of the present disclosure is to provide a radar system capable of suppressing false detection. Another object of the present disclosure is to provide a radar control device capable of suppressing false detection. Yet another object of the present disclosure is to provide a radar control method capable of suppressing false detection. Yet another object of the present disclosure is to provide a radar control program capable of suppressing false detection.

[0007] The technical means of the present disclosure for solving the problems will be described below. Note that the reference numerals in parentheses in the claims indicate the correspondence with the specific means described in the embodiments described later in detail, and do not limit the technical scope of the present disclosure.

[0008] A first aspect of the present disclosure is a radar system having a plurality of transmitting antennas, at least one receiving antenna, and a processor, wherein the processor is configured to perform the following: transmit, from each transmitting antenna, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount between the transmitting antennas for each repetition period; and output sensing data correlating the transmission signals from the plurality of transmitting antennas to received signals received at the receiving antenna; wherein transmitting the transmission signals includes transmitting, from each transmitting antenna, transmission signals to which an initial phase changed according to the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data includes setting candidates for correspondence between a plurality of peaks and a plurality of transmitting antennas in a velocity spectrum defined from received signals received at the receiving antenna from the transmission signals from the plurality of transmitting antennas; and when a phase difference between peaks correlated to the spatial arrangement of the transmitting antennas is confirmed in a combination of a peak according to the set candidate and the initial phase, outputting sensing data correlating to the received signals for which the correspondence defined by the candidate is defined.

[0009] A second aspect of the present disclosure is a radar control device having a processor and controlling a radar system equipped with a plurality of transmitting antennas and at least one receiving antenna, wherein the processor is configured to perform the following: transmit, from each transmitting antenna, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount between the transmitting antennas for each repetition period; and output sensing data correlating the transmission signals from the plurality of transmitting antennas to a received signal received by the receiving antenna; wherein transmitting the transmission signal includes transmitting, from each transmitting antenna, a transmission signal to which an initial phase changed depending on the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data includes setting candidates for correspondence between a plurality of peaks and a plurality of transmitting antennas in a velocity spectrum defined from a received signal received by the receiving antenna from the transmission signals from the plurality of transmitting antennas; and when a phase difference between the peaks correlated to the spatial arrangement of the transmitting antennas is confirmed in a combination of a peak according to the set candidate and the initial phase, outputting sensing data correlating to the received signal for which the correspondence defined by the candidate is defined.

[0010] A third aspect of the present disclosure is a radar control method executed by a processor to control a radar system having a plurality of transmitting antennas and at least one receiving antenna, the method comprising: transmitting, from each transmitting antenna, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount between the transmitting antennas for each repetition period; and outputting sensing data correlated with a received signal from the transmitting signals from the plurality of transmitting antennas and received at the receiving antenna, wherein transmitting the transmission signal comprises transmitting, from each transmitting antenna, a transmission signal to which an initial phase changed depending on the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data comprises setting candidates for a correspondence relationship between a plurality of peaks and a plurality of transmitting antennas in a velocity spectrum defined from a received signal from the transmitting signals from the plurality of transmitting antennas and received at the receiving antenna; and when a phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is confirmed in a combination of a peak according to the set candidate and the initial phase, outputting sensing data correlated with the received signal for which the correspondence relationship defined by the candidate is defined.

[0011] A fourth aspect of the present disclosure is a radar control program stored in a storage medium and including instructions to be executed by a processor that controls a radar system having a plurality of transmitting antennas and at least one receiving antenna, the instructions including: causing each transmitting antenna to transmit a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount between the transmitting antennas for each repetition period; and outputting sensing data that correlates the transmission signals from the plurality of transmitting antennas to a received signal received by the receiving antenna, wherein transmitting the transmission signal includes causing each transmitting antenna to transmit a transmission signal to which an initial phase that is changed depending on the transmitting antenna in addition to the shift amount is assigned; and outputting the sensing data includes: setting candidates for correspondence between a plurality of peaks and a plurality of transmitting antennas in a velocity spectrum defined from a received signal received by the receiving antenna from the transmission signals from the plurality of transmitting antennas; and when a phase difference between the peaks that correlates to the spatial arrangement of the transmitting antennas is confirmed in a combination of a peak according to the set candidate and the initial phase, outputting sensing data that correlates to the received signal for which the correspondence defined by the candidate is defined.

[0012] According to these first to fourth aspects, a shift amount and an initial phase are assigned to the transmission signal transmitted from each transmitting antenna. Therefore, a velocity spectrum defined from a single received signal may have peaks including different initial phases for each velocity corresponding to the shift amount. Therefore, if candidates for correspondence relationships between multiple peaks and multiple transmitting antennas are valid, a phase difference between the peaks correlating with the spatial arrangement of the transmitting antennas may be confirmed in the velocity spectrum according to the combination of the peaks and initial phases corresponding to the candidates. Therefore, sensing data correlated with a group of received signals for which correspondence relationships are defined in which a phase difference between the peaks correlating with the spatial arrangement of the transmitting antennas is confirmed may be sensing data in which the correspondence relationships between the multiple peaks and the multiple transmitting antennas are accurately identified. Therefore, false detection may be suppressed.

[0013] FIG. 1 is a schematic diagram showing the overall configuration of a radar system according to a first embodiment. FIG. 2 is a schematic diagram for explaining phases assigned to transmission signals in each transmitting antenna. FIG. 3 is a block diagram showing the functional configuration of a control unit in the radar system. FIG. 4 is a flowchart showing a radar control flow according to the first embodiment. FIG. 5 is a schematic diagram for explaining a part of the processing by the radar system. FIG. 6 is a schematic diagram for explaining angle measurement processing when the correspondence candidate is legitimate. FIG. 7 is a schematic diagram for explaining angle measurement processing when the correspondence candidate is invalid. FIG. 8 is a flowchart showing a radar control flow according to a second embodiment. FIG. 9 is a flowchart showing a radar control flow according to a third embodiment. FIG. 10 is a schematic diagram for explaining detection of multiple targets.

[0014] Hereinafter, multiple embodiments of the present disclosure will be described with reference to the drawings. Note that corresponding components in each embodiment are designated by the same reference numerals, and redundant description may be omitted. Furthermore, when only a portion of the configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the remaining portions of the configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

[0015] First Embodiment A first embodiment of the present disclosure will be described with reference to FIGS. 1 to 7. A radar device 1 shown in FIG. 1 is mounted on a moving object such as a vehicle. The radar device 1 transmits a transmission signal to the outside world and receives the transmission signal reflected by a target T as a received signal. The radar device 1 acquires and outputs sensing data related to the target T that reflected the transmission signal by analyzing the received signal. The radar device 1 is a so-called MIMO (Multiple-Input-Multiple-Output) radar that transmits transmission signals from multiple transmission antennas TX to artificially increase the number of receiving antennas RX beyond the actual number. The radar device 1 is an example of a "radar system."

[0016] The sensing data output from the radar device 1 is input to an in-vehicle ECU (Electronic Control Unit) via an in-vehicle network such as a Control Area Network (CAN) (registered trademark) or Ethernet (registered trademark). The in-vehicle ECU executes various processes for automatic driving of the vehicle and advanced driving assistance based on the acquired sensing data of each target T.

[0017] The processing based on the sensing data includes, for example, collision avoidance processing, warning processing, etc. The collision avoidance processing is processing for controlling the vehicle to avoid a collision with the target T by controlling the brake system, steering system, etc. based on the sensing data of each target T. The warning processing is processing for warning the driver of the possibility of a collision with the target T based on the sensing data of each target T.

[0018] 1, the radar device 1 of this embodiment includes a transceiver unit 2, a control unit 7, and a storage unit 8. The transceiver unit 2 is a processing unit that performs transmission processing of a transmission signal and reception processing of a reception signal. The transceiver unit 2 includes a clock oscillator 3, a signal generator 4, multiple transmission circuits 5, multiple transmission antennas TX, multiple reception antennas RX, and multiple reception circuits 6.

[0019] The clock oscillator 3 generates a periodic clock signal. The clock oscillator 3 transmits the clock signal to the signal generator 4 and each receiving circuit 6. The signal generator 4 generates a chirp signal modulated so that the frequency changes over time, for each chirp period Tc corresponding to the clock signal. The signal generator 4 generates a specified number of chirp signals for each measurement period Tf. The generated multiple chirp signals are distributed and output to each channel of the transmitting circuit 5 and the receiving circuit 6. Note that in FIG. 2 , the chirp signal is shown as a so-called up-chirp signal, whose frequency increases over time. However, the chirp signal may also be a so-called down-chirp signal, whose frequency decreases over time.

[0020] In the following, the multiple chirp signals output from the signal generator 4 to the transmitter circuit 5 and transmitted from the transmitter antenna TX may be referred to as transmission signals. Furthermore, the multiple chirp signals output to the receiver circuit 6 in response to the transmission signals may be referred to as local signals.

[0021] The transmitter circuit 5 and receiver circuit 6 are each mainly composed of a semiconductor integrated circuit device such as an MMIC (Monolithic Microwave Integrated Circuit). The transmitter circuit 5 is connected to a transmitter antenna TX and outputs a transmit signal to the transmitter antenna TX. The transmitter circuit 5 includes the same number of phase shifters 51 and amplifiers 52 as the number of connected transmitter antennas TX.

[0022] The phase shifter 51 imparts a specific phase shift to the input transmission signal. More specifically, the phase shifter 51 imparts at least a phase shift by shifting a plurality of chirp signals arranged in time by a substantially constant amount of shift for each chirp period Tc. For example, as shown in FIG. 2 , the phase shifter 51 imparts a shift amount ω to a plurality of chirp signals as transmission signals transmitted from a specific transmission antenna TX1 among the plurality of transmission antennas TX. １ In this case, the k-th chirp signal is shifted by an amount ω before being input to the phase shifter 51. １ The phase is rotated by a factor of the chirp number multiplied by . As a result, the phase of the multiple chirp signals that are aligned in time and that have passed through the phase shifter 51 changes linearly for each chirp period Tc. This linear change in phase imparts a pseudo Doppler velocity to the chirp signal according to the shift amount. The shift amount that imparts the above phase change may be referred to as the Doppler shift amount below. Note that in FIG. 2, the chirp number k ranges from "1" to "N," which is the maximum number of chirp signals in the measurement period Tf. However, the chirp number k may be set to start from any number, such as "0." The chirp period Tc is an example of a "repetition period."

[0023] Each of the phase shifters 51 applies a different Doppler shift amount to each of the chirp signals transmitted from a transmitting antenna TX2 other than the transmitting antenna TX1 in FIG. １ A shift amount ω different from ２ Similarly, for the transmitting antenna TXm, a shift amount ω is given to the multiple chirp signals to be transmitted. １ , ω ２ Shift amount ω different from etc. ｍ As a result, the multiple transmission signals transmitted from the multiple transmission antennas TX are subjected to so-called Doppler Division Multiplexing (DDM).

[0024] Furthermore, the phase shifter 51 calculates a specific initial phase φ in addition to the Doppler shift amount. ｉ can be assigned to the chirp signal. The phase shifter 51 assigns substantially the same initial phase to each of the multiple chirp signals arranged in time. Each of the multiple phase shifters 51 assigns an initial phase that is changed depending on the transmitting antenna TX to which it is output. For example, each phase shifter 51 assigns a corresponding phase as an initial phase from a phase sequence pseudo-randomly coded using a PN sequence or the like. The phase sequence is, for example, a sequence of phases pseudo-randomly changed between "0" and "π" depending on the transmitting antenna TX. In this case, each initial phase φ in the example of FIG. 2 ｉ＿１ , φ ｉ＿１ , φ ｉ＿ｍ etc. are pseudo-randomly assigned either "0" or "π".

[0025] The phase shifter 51 may impart a preset Doppler shift amount and initial phase to the chirp signal. Alternatively, the phase shifter 51 may impart a different Doppler shift amount and initial phase between measurement periods Tf in response to a control command from the control unit 7. The amplifier 52 amplifies the transmission signal output from the phase shifter 51 and outputs the amplified signal to the corresponding transmitting antenna TX.

[0026] The transmitting antenna TX converts the transmission signal supplied from the transmitting circuit 5 from an electrical signal to a radio wave signal and transmits it to the outside. A single transmitting antenna TX is configured to include at least one antenna element. For example, the transmitting antenna TX is a patch antenna equipped with multiple flat antenna elements. The antenna elements are arranged on the opposite side of a dielectric substrate having a ground plane on one side, facing the ground plane. The multiple antenna elements are connected, for example, in series, by a feeder line that supplies the electrical signal. Each transmission signal transmitted from each of the multiple transmitting antennas TX is given a Doppler shift amount that differs for each transmitting antenna TX and an initial phase that is changed depending on the transmitting antenna TX by the corresponding phase shifter 51.

[0027] The receiving antenna RX receives, as a received signal, a radio wave signal including a transmitted signal reflected by a target T, which is a reflecting object in the outside world. Each of the multiple receiving antennas RX receives a signal in a state in which the received signals corresponding to the transmitted signals from the multiple transmitting antennas TX are mixed together. Hereinafter, this mixed signal received by each receiving antenna RX will be referred to as a mixed received signal. Furthermore, the components of the received signals corresponding to the transmitted signals from the multiple transmitting antennas TX, mixed together in the mixed received signal, will be referred to as received signal components.

[0028] The receiving antenna RX converts the received signal as a radio wave signal into an electrical signal and outputs it to the corresponding receiving circuit 6. The receiving antenna RX is, for example, a patch antenna, similar to the transmitting antenna TX, in which at least one antenna element is connected in series by a feeder line. Note that the transmitting antenna TX and the receiving antenna RX may also be monopole antennas, inverted-F antennas, loop antennas, or the like. Note that, hereinafter, multiple received signals received by multiple receiving antennas RX may be collectively referred to as a received signal group.

[0029] The receiving circuit 6 is connected to the receiving antennas RX and acquires the signals received by the receiving antennas RX. The receiving circuit 6 includes amplifiers 61, signal mixers 62, and AD converters 63, the number of which is equal to the number of the connected receiving antennas RX.

[0030] The amplifier 61 amplifies the received signal received by the receiving antenna RX and outputs the amplified signal to the signal mixer 62. The signal mixer 62 generates a beat signal by mixing the local signal from the signal generator 4 with the received signal. The generated beat signal becomes an interference signal representing the frequency difference between the received signal and the local signal. The beat signal generated by the signal mixer 62 may be filtered by a low-pass filter (not shown) to remove high-frequency components that deviate from the frequency difference between the received signal and the local signal. The beat signal is also called an IF signal.

[0031] The AD converter 63 converts the beat signal, which is an analog signal, into a digital signal. The AD converter 63 acquires the clock signal output from the clock oscillator 3, samples the beat signal at time intervals corresponding to the cycle of the clock signal, and digitizes it. The AD converter 63 sequentially outputs the digitized beat signal to the control unit 7.

[0032] The control unit 7 is connected to the transceiver unit 2 via at least one of a LAN (Local Area Network) line, a wire harness, an internal bus, a wireless communication line, etc. The configuration of the control unit 7 will be described later.

[0033] The accommodation unit 8 is a housing that accommodates the transceiver unit 2 and the control unit 7. The accommodation unit 8 includes a radome 81 and a case body 82. The radome 81 is mainly formed of a transparent material that allows millimeter-wave band radio waves to pass through. The radome 81 is attached to the case body 82 so as to cover the antennas TX and RX. The radome 81 protects the antennas TX and RX while allowing radio waves to pass through, enabling the antennas TX and RX to transmit and receive signals. The case body 82, together with the radome 81, defines an accommodation space that accommodates the components of the radar device 1 described above.

[0034] The control unit 7 includes at least one dedicated computer. The dedicated computer constituting the control unit 7 may be a radar ECU (Electronic Control Unit) specialized for controlling a specific radar device 1. The dedicated computer constituting the control unit 7 may be a radar management ECU that controls multiple radar devices 1 mounted on a moving object in an integrated manner. The dedicated computer constituting the control unit 7 may be a sensor management ECU that controls multiple sensors including the radar device 1 and other sensors such as LiDAR (Light Detection and Ranging / Laser Imaging Detection and Ranging).

[0035] The dedicated computer constituting the control unit 7 has at least one memory 7a and one processor 7b. The memory 7a is a storage medium that non-temporarily stores computer-readable programs, data, etc., and is at least one type of non-transitory tangible storage medium, such as a semiconductor memory, a magnetic medium, or an optical medium. Here, "storage" may refer to accumulation in which data is retained even when the radar device 1 is turned off, or may refer to temporary storage in which data is erased when the radar device 1 is turned off. The processor 7b includes at least one type of core selected from the group consisting of a central processing unit (CPU), a graphics processing unit (GPU), a reduced instruction set computer (RISC)-CPU, a data flow processor (DFP), and a graph streaming processor (GSP).

[0036] In the control unit 7, the processor 7b executes a plurality of instructions included in a radar control program stored in the memory 7a in order to control the radar device 1. In this way, the control unit 7 constructs a plurality of functional blocks for controlling the radar device 1. The functional blocks constructed in the control unit 7 include a transmission processing block 71 and a reception processing block 72, as shown in Fig. 3. The control unit 7 is an example of a "radar control device."

[0037] The radar control method in which the control unit 7 controls the radar device 1 through cooperation of these blocks 71 and 72 is executed in accordance with the radar control flow shown in Fig. 4. This radar control flow is executed repeatedly while the radar device 1 is running. Note that each "S" in this radar control flow represents a plurality of steps executed by a plurality of commands included in the radar control program.

[0038] First, in S10, the transmission processing block 71 outputs a command to start transmission processing to the transceiver unit 2, thereby causing the transmission signals to be transmitted from the multiple transmission antennas TX. As described above, the phase shifter 51 imparts to the chirp signals constituting the transmission signals a different Doppler shift amount for each transmission antenna TX and an initial phase changed according to the transmission antenna TX.

[0039] The transmission processing block 71 may transmit a command to start the transmission process, thereby causing the transceiver unit 2 to transmit a transmission signal with a preset Doppler shift amount and initial phase. Alternatively, the transmission processing block 71 may sequentially set the Doppler shift amount and initial phase for each measurement period Tf and output them to the transceiver unit 2.

[0040] Next, in S20, the reception processing block 72 acquires, from each reception circuit 6, beat signals defined from each reception signal of the reception signal group. Then, in S30, the reception processing block 72 acquires a Doppler spectrum for the beat signal defined from the reception signal received by a single reception antenna RX. The reception processing block 72 may acquire a beat signal corresponding to a specific, predefined single reception antenna RX. Alternatively, the reception processing block 72 may change the single reception antenna RX corresponding to the acquired beat signal for each measurement period Tf.

[0041] To describe in more detail how the Doppler spectrum is acquired, the reception processing block 72 acquires the Doppler spectrum by performing a Fast Fourier Transform (FFT) twice on the beat signal. Through the first FFT, the reception processing block 72 acquires, for each chirp signal, a frequency spectrum (distance spectrum) that exhibits a peak at a frequency position corresponding to the distance to the target T. The distance spectrum data is a distance bin signal that includes information on the signal strength for each distance bin according to the distance resolution.

[0042] Furthermore, the receiver processing block 72 performs a second FFT process on a waveform in which the phases at the range bins obtained in the first FFT process for the multiple chirp signals are arranged in time series. As a result of the FFT process, the receiver processing block 72 acquires, for each range bin, a frequency spectrum (Doppler spectrum) that shows a peak at a position corresponding to the Doppler velocity (relative velocity) of the target T. As a result, the receiver processing block 72 acquires a two-dimensional spectrum of the range R and the Doppler velocity V, as shown in FIG. 5. The Doppler spectrum is also called a velocity spectrum, and the two-dimensional spectrum is also called an RV map. Note that, for simplicity, the example in FIG. 5 shows a case in which three transmitting antennas TX1, TX2, and TX3 and four receiving antennas RX1, RX2, RX3, and RX4 are provided.

[0043] Furthermore, in S40, the reception processing block 72 sets candidates for the correspondence relationship between the multiple peaks in the Doppler spectrum and the multiple transmitting antennas TX. In other words, the reception processing block 72 tentatively determines, for each of the multiple peaks in the same distance bin of the two-dimensional spectrum, which transmitting antenna TX the transmitted signal from.

[0044] For example, suppose that a transmission signal is reflected by a single target T and received by each receiving antenna RX. In this case, peaks resulting from each transmission signal are detected in the velocity bin corresponding to the amount of Doppler shift imparted to each transmission signal in the same distance bin. That is, in the example shown in Fig. 5, a peak P_TX1 corresponding to the transmission signal from transmitting antenna TX1, a peak P_TX2 corresponding to the transmission signal from transmitting antenna TX2, and a peak P_TX3 corresponding to the transmission signal from transmitting antenna TX3 are detected.

[0045] Here, suppose that a peak P_S unrelated to the peaks corresponding to the transmitted signal is mixed in the same range bin as the above-mentioned peaks P_TX1, P_TX2, and P_TX3. Such a peak P_S may be due to a spurious signal caused by a phase error generated in each phase shifter 51, or a transmitted signal reflected by another target T, etc.

[0046] In this case, the reception processing block 72 sets candidates for the correspondence relationship between these four peaks and the three transmitting antennas TX1, TX2, and TX3 as correspondence candidates. That is, the reception processing block 72 selects three candidates for the peak that are estimated to correspond to the transmission signals transmitted from each of the transmitting antennas TX1, TX2, and TX3 from among the four peaks.

[0047] The reception processing block 72 may estimate and set correspondence candidates based on at least one of the following: the position of the speed bin in which each peak is detected, the relative positional relationship between the speed bins of the peaks, and the signal strength of each peak. Alternatively, the reception processing block 72 may randomly set correspondence candidates.

[0048] In the next step S50, the reception processing block 72 decodes the Doppler spectrum with respect to the initial phase corresponding to the set candidate. Specifically, the reception processing block 72 extracts peaks corresponding to the corresponding candidates, i.e., peaks selected as corresponding to the transmission signal from the transmitting antenna TX, from the acquired Doppler spectrum. The reception processing block 72 then performs a calculation process to cancel the initial phase corresponding to the set corresponding candidate for each extracted peak. As a result, the reception processing block 72 acquires a decoded spectrum in which the Doppler spectrum is decoded with respect to the initial phase.

[0049] Next, in S60, the receiving processing block 72 performs angle measurement processing on the single decoded spectrum. In the angle measurement processing, the receiving processing block 72 performs a third FFT process on the single decoded spectrum. In the third FFT process, the receiving processing block 72 performs FFT processing on a waveform in which the phases of the peaks in the decoded spectrum are aligned. As a result, the receiving processing block 72 acquires a frequency spectrum (angular spectrum) showing peaks at the positions of the arrival angles of the received signals for angle A. The arrival angle of the received signals substantially corresponds to the relative angle of the target T. Note that the FFT process in S60 is performed using a beat signal corresponding to the received signal obtained by receiving signals transmitted from multiple transmitting antennas TX at a single receiving antenna RX. For this reason, this FFT process can also be referred to as MISO (Multiple-Input-Single-Output) angle measurement processing.

[0050] Then, in S70, the reception processing block 72 determines whether the signal-to-noise ratio at the peak of the angular spectrum is outside the specified range. The signal-to-noise ratio is the ratio of signal strength to noise level NL. The reception processing block 72 may perform this determination, for example, for the maximum peak in the angular spectrum. Here, the specified range is the range of signal-to-noise ratios that are equal to or less than a threshold. The threshold is specified as a value that causes the signal-to-noise ratio to fall outside the specified range when the set correspondence candidates are normal, i.e., when the combination of each peak and each transmitting antenna TX is correct.

[0051] For example, as shown in FIG. 6, assume that the correspondence candidates are set such that peak P_TX1 corresponds to transmitting antenna TX1, peak P_TX2 corresponds to transmitting antenna TX2, and peak P_TX3 corresponds to transmitting antenna TX3. In this case, the set correspondence candidates are normal. Therefore, the initial phases assigned to the phases of the peaks are accurately canceled by the decoding process in S50. Therefore, the phases of the peaks are essentially given a phase θ derived from the arrival angle. １ , θ ２ , θ ３ In other words, the phase difference between the peaks is a regular phase difference that correlates with the spatial arrangement of the transmitting antennas TX. Therefore, the angular spectrum obtained by FFT processing shows peaks at the relative angles of the target T.

[0052] Therefore, the signal-to-noise ratio of the peaks in the angular spectrum falling outside the specified range is an example of the phase difference between the peaks in the decoded spectrum correlating with the spatial arrangement of the transmitting antennas TX. In turn, the signal-to-noise ratio of the angular spectrum falling outside the specified range is also an example of the phase difference between the peaks correlating with the spatial arrangement of the transmitting antennas TX being confirmed in the combination of the peaks and the initial phase according to the set candidates.

[0053] On the other hand, as shown in FIG. 7 , suppose that a correspondence candidate is set in which peak P_S corresponds to transmitting antenna TX1, peak P_TX1 corresponds to transmitting antenna TX2, and peak P_TX2 corresponds to transmitting antenna TX3. In this case, the set correspondence candidate is irregular. Therefore, the decoding process of S50 imparts a further irregular phase to the phase of each peak. As a result, the angular spectrum acquired by the FFT process is spread without showing a peak at the relative angle of target T. If the MIMO angle measurement process described below is performed with the relationship between the peaks and the transmitting antennas TX defined using irregular correspondence candidates, erroneous detection of the relative angle and, ultimately, the sensing data may occur.

[0054] That is, the reception processing block 72 essentially determines whether the set correspondence candidate is legitimate by determining whether the signal-to-noise ratio of the peak in the angular spectrum is outside a specified range.

[0055] If it is determined that the signal-to-noise ratio is within the specified range, the flow proceeds to S80. In S80, the reception processing block 72 stops outputting the sensing data. If the processes of S70 and S80 do not confirm a phase difference between peaks that correlates with the spatial arrangement of the transmitting antennas TX, the output of the sensing data is interrupted.

[0056] On the other hand, if it is determined in S80 that the signal-to-noise ratio is outside the specified range, the flow proceeds to S90. In S90, the reception processing block 72 decodes the entire Doppler spectrum with respect to the initial phase using a combination of peaks and initial phases according to the set correspondence. That is, the reception processing block 72 acquires Doppler spectra for beat signals based on received signals at other reception antennas RX other than the beat signal used to confirm the phase difference between the peaks. The reception processing block 72 then extracts peaks from each Doppler spectrum and cancels the initial phase from the phase of each peak according to the set correspondence, thereby acquiring a decoded spectrum for each reception antenna RX.

[0057] In the next step S100, the reception processing block 72 performs angle measurement processing on the multiple decoded spectra. That is, the reception processing block 72 performs FFT processing on a waveform in which the phases of each peak in an integrated spectrum obtained by integrating the multiple decoded spectra are aligned. At this time, the reception processing block 72 performs FFT processing after defining the correspondence between each peak and each transmitting antenna TX according to the set candidates. As a result, the reception processing block 72 acquires an angular spectrum showing a peak at a position corresponding to the relative angle with respect to the target T. Note that the FFT processing in S100 is processing performed using a group of beat signals corresponding to a group of received signals obtained by receiving transmission signals from the multiple transmitting antennas TX at each of the multiple receiving antennas RX. For this reason, this FFT processing can also be referred to as MIMO angle measurement processing.

[0058] Furthermore, in S110, the reception processing block 72 outputs sensing data corresponding to candidates for correspondence relationships in which the phase difference between peaks correlated with the spatial arrangement of the transmitting antennas TX has been confirmed. The reception processing block 72 outputs, as sensing data, information about the target T, such as the distance to the target T, the relative speed, and the relative angle. The distance information, the relative speed information, and the relative angle information are information that correlates the transmission signals from the multiple transmitting antennas TX with the reception signals received by each of the multiple receiving antennas RX, obtained by the MIMO angle measurement process.

[0059] According to the first embodiment described above, the transmission signal transmitted from each transmitting antenna TX is assigned a Doppler shift amount and an initial phase for each transmitting antenna TX. Therefore, a Doppler spectrum defined from a single received signal may have peaks containing different initial phases for each velocity corresponding to the Doppler shift amount. Therefore, if the candidates for correspondence relationships between multiple peaks and multiple transmitting antennas TX are valid, the Doppler spectrum may contain a phase difference between the peaks that correlates with the spatial arrangement of the transmitting antennas TX, depending on the combination of the peaks and initial phases corresponding to the candidates. Therefore, sensing data correlated with a group of received signals for which correspondence relationships are defined in which a phase difference between the peaks that correlates with the spatial arrangement of the transmitting antennas TX is confirmed may be sensing data in which the correspondence relationships between the multiple peaks and the multiple transmitting antennas TX are accurately identified. Therefore, erroneous detection of the sensing data of the target T may be suppressed.

[0060] Furthermore, according to the first embodiment, a transmission signal is encoded at an initial phase that is changed depending on the transmitting antenna TX. Then, sensing data is output when the phase difference between peaks in a decoded spectrum obtained by decoding a Doppler spectrum for the initial phase depending on the set candidate correlates with the spatial arrangement of the transmitting antennas TX. Therefore, by decoding the encoding, it is possible to reliably identify the correspondence between multiple peaks and multiple transmitting antennas TX.

[0061] Furthermore, according to the first embodiment, when the signal-to-noise ratio of the peak in the angular spectrum defined from the decoded spectrum is outside the specified range, the sensing data is output. Therefore, it is possible to reliably determine whether the decoding has been successful or not based on the signal-to-noise ratio of the peak in the angular spectrum.

[0062] In addition, according to the first embodiment, if a phase difference between peaks correlated with the spatial arrangement of the transmitting antennas TX is not confirmed in a combination of peaks and initial phases according to the set candidates, output of the sensing data is interrupted. This makes it possible to avoid output of sensing data correlated with a group of received signals in which a correspondence relationship between multiple peaks and multiple transmitting antennas TX that is likely to be irregular is defined. This makes it possible to reliably suppress erroneous detection.

[0063] Second Embodiment As shown in FIG. 8, the second embodiment is a modification of the first embodiment.

[0064] In the radar control flow of the second embodiment, if it is determined in S70 that the signal-to-noise ratio is within a specified range, the flow proceeds to S85. In S85, the reception processing block 72 resets candidates for correspondence other than the candidate for which a negative determination was made in S70. The reception processing block 72 may reset candidates for correspondence that are estimated to be normal from multiple possible candidates excluding the candidate for which a negative determination was made. Alternatively, the reception processing block 72 may reset candidates for correspondence according to a specific resetting rule, such as shifting the peak associated with the transmitting antenna TX by one point on the Doppler axis.

[0065] After the process of S85, the flow returns to S50. That is, in this embodiment, the reception processing block 72 resets the candidates for the correspondence relationship to search for a candidate that can be determined to be a regular correspondence relationship.

[0066] According to the second embodiment described above, when a phase difference between peaks correlated with the spatial arrangement of the transmitting antennas TX is not confirmed in a combination of peaks and initial phases according to a set candidate, a phase difference between peaks correlated with the spatial arrangement of the transmitting antennas TX is confirmed in another candidate. Therefore, correspondences can be searched until correspondences between multiple peaks and multiple transmitting antennas TX that are likely to be normal are confirmed. Therefore, erroneous detections can be suppressed and accurate sensing data can be reliably output.

[0067] Third Embodiment As shown in FIGS. 9 and 10, the third embodiment is a modification of the first embodiment.

[0068] In the radar control flow in the third embodiment, if it is determined in S70 that the signal-to-noise ratio is outside the specified range, the flow proceeds to S71. In S71, the reception processing block 72 adopts this candidate as a correspondence relationship to be used for decoding the Doppler spectrum and stores it in the memory 7a or the like as an adopted candidate. On the other hand, if it is determined in S70 that the signal-to-noise ratio is within the specified range, the flow proceeds to S72. In S71, the reception processing block 72 rejects this candidate as a correspondence relationship to be used for decoding the Doppler spectrum and discards the data or stores it as an rejected candidate.

[0069] After the process of S71 or S72, the flow proceeds to S73. In S73, the reception processing block 72 determines whether or not the selection of whether or not to adopt the correspondence relationship has been completed for all patterns of combinations of peaks and transmitting antennas TX.

[0070] If it is determined that the selection of all patterns has not been completed, the flow proceeds to S74. In S74, the reception processing block 72 sets another candidate for the correspondence relationship from among the patterns for which the selection has not yet been completed as the selection target. After the processing of S74, the flow proceeds to S50. As a result, a selection is made as to whether or not to adopt the correspondence relationship for all patterns of combinations of peaks and transmitting antennas TX.

[0071] On the other hand, if it is determined in S73 that the selection of all patterns has been completed, the flow proceeds to S90. In S90 of this embodiment, if there are multiple corresponding candidates for adoption, the reception processing block 72 executes the decoding process for each candidate for adoption individually.

[0072] For example, suppose two different targets T1 and T2 are located at the same distance, as shown in Figure 10. In this case, peaks P1_TX1, P1_TX2, and P1_TX3 corresponding to target T1 and peaks P2_TX1, P2_TX2, and P2_TX3 corresponding to target T2 are detected in the Doppler spectrum of the same distance bin. In such a situation, there may be multiple candidates for the corresponding relationship.

[0073] Therefore, the reception processing block 72 performs decoding processing assuming that each of the adopted candidates corresponds to different targets T1 and T2 at the same distance. In the subsequent processing at S100, the reception processing block 72 also performs MIMO angle measurement processing for different targets T1 and T2 at the same distance for each decoded spectrum corresponding to each adopted candidate. Then, in processing at S110, the reception processing block 72 outputs sensing data for different targets T1 and T2 at the same distance.

[0074] According to the third embodiment described above, multiple patterns of candidates are set that are assumed for the correspondence relationship between multiple peaks and multiple transmitting antennas TX. Then, when there are multiple candidates in which a phase difference between peaks correlated with the spatial arrangement of the transmitting antennas TX has been confirmed, sensing data is output for each candidate in which a phase difference has been confirmed. Therefore, when there are multiple candidates in which a phase difference between peaks correlated with the spatial arrangement of the transmitting antennas TX has been confirmed, sensing data can be output for each candidate as a peak originating from a different target T. Therefore, even when peaks overlap in Doppler spectra at the same distance, it may be possible to distinguish between the overlapping peaks.

[0075] (Other Embodiments) Although multiple embodiments have been described above, the present disclosure should not be construed as being limited to those embodiments, and can be applied to various embodiments and combinations within the scope that does not deviate from the gist of the present disclosure.

[0076] In a modified example, the reception processing block 72 in S50 may perform decoding processing for each single Doppler spectrum for the number of reception antennas RX. The reception processing block 72 may perform the processing of S60 and S70 for each single Doppler spectrum, integrate the determination results for each single Doppler spectrum, and determine whether to proceed to S80 or S90.

[0077] In a modified example, at least a part of the processing executed in blocks 71 and 72 may be executed by a processor external to the radar device 1. For example, at least a part of the processing may be executed by a processor of an on-board ECU mounted on a vehicle equipped with the radar device 1. For example, in Figures 4, 8, and 9, the processing from S30 or S40 onwards may be executed by the processor of the on-board ECU. In this case, the "radar system" is configured to include the radar device 1 and the processor of the on-board ECU.

[0078] In a modified example, the radar device 1 may include only one receiving antenna RX. In this case, the reception processing block 72 outputs sensing data correlated with the received signal received by the single receiving antenna RX. For example, when the signal-to-noise ratio of a peak in an angular spectrum defined from a decoded spectrum corresponding to a corresponding candidate falls outside a specified range, the reception processing block 72 outputs sensing data including at least the relative angle of the target T corresponding to the peak.

[0079] In a modified example, the dedicated computer constituting the control unit 7 may have at least one of a digital circuit and an analog circuit as the processor 7b. Here, the digital circuit is at least one of an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a system on a chip (SOC), a programmable gate array (PGA), and a complex programmable logic device (CPLD). Such a digital circuit may also have a memory 7a storing a program.

[0080] In a modified example, the mobile body to which the radar device 1 is applied may be, for example, an autonomous robot that can transport luggage or collect information by autonomous driving or remote driving. Examples of the autonomous robot include an autonomous vehicle.

[0081] (Disclosure of Technical Ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be described in a multiple dependent form, with the subsequent clause alternatively referring to the preceding clause. Furthermore, some clauses may be described in a multiple dependent form, with the subsequent clause referring to another multiple dependent clause. These multiple dependent clauses define multiple technical ideas.

[0082] (Technical Idea 1) A radar system having a plurality of transmitting antennas (TX), at least one receiving antenna (RX), and a processor (7b), wherein the processor is configured to execute the following: transmit, from each of the transmitting antennas, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount for each of the repetition periods; and output sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received by the receiving antenna; wherein transmitting the transmission signals includes transmitting, from each of the transmitting antennas, the transmission signals to which an initial phase changed according to the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data includes setting candidates for correspondence between a plurality of peaks and a plurality of the transmitting antennas in a velocity spectrum defined from the received signals received by the receiving antenna from the transmission signals from the plurality of transmitting antennas; and when a phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is confirmed in a combination of the peak and the initial phase according to the set candidate, outputting the sensing data correlated with the received signal for which the correspondence relationship is defined by the candidate.

[0083] (Technical Idea 2) A radar system according to Technical Idea 1, wherein transmitting the transmission signals includes transmitting, from each of the transmitting antennas, each of the transmission signals encoded with the initial phase changed according to the transmitting antenna, and outputting the sensing data includes outputting the sensing data when the phase difference between the peaks in a decoded spectrum in which the velocity spectrum is decoded for the initial phase according to the set candidate correlates with the spatial arrangement of the transmitting antennas.

[0084] (Technical Idea 3) A radar system according to Technical Idea 2, wherein outputting the sensing data includes outputting the sensing data when a signal-to-noise ratio of a peak in an angular spectrum defined from the decoded spectrum is outside a specified range on the larger side.

[0085] (Technical Idea 4) A radar system according to any one of Technical Ideas 1 to 3, wherein the output of the sensing data is interrupted when the phase difference between the peaks that correlates with the spatial arrangement of the transmitting antenna is not confirmed in the combination of the peak and the initial phase according to the set candidate.

[0086] (Technical Idea 5) A radar system described in any one of Technical Ideas 1 to 3, wherein outputting the sensing data includes, when the phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is not confirmed in a combination of the peak and the initial phase according to the set candidate, confirming the phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas in another candidate.

[0087] (Technical Idea 6) The radar system according to any one of Technical Ideas 1 to 3, wherein outputting the sensing data includes: setting multiple patterns of candidates assumed for the correspondence between multiple peaks and multiple transmitting antennas; and, when there are multiple candidates for which the phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas has been confirmed, outputting the sensing data for each of the candidates for which the phase difference has been confirmed.

[0088] The above technical concepts 1 to 6 may be implemented in the form of a radar control device, a radar control method, and a radar control program.

Claims

1. A radar system having a plurality of transmitting antennas (TX), at least one receiving antenna (RX), and a processor (7b), wherein the processor is configured to execute the following: transmit, from each of the transmitting antennas, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount for each of the repetition periods; and output sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received by the receiving antenna; wherein transmitting the transmission signals includes transmitting, from each of the transmitting antennas, the transmission signals to which an initial phase changed according to the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data includes setting candidates for correspondence between a plurality of peaks and a plurality of the transmitting antennas in a velocity spectrum defined from the received signals received by the receiving antenna from the transmission signals from the plurality of transmitting antennas; and when a phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is confirmed in a combination of the peak and the initial phase according to the set candidate, outputting the sensing data correlated with the received signal for which the correspondence relationship is defined by the candidate.

2. The radar system of claim 1, wherein transmitting the transmission signals includes transmitting, from each of the transmission antennas, each of the transmission signals encoded with the initial phase changed according to the transmitting antenna, and outputting the sensing data includes outputting the sensing data when the phase difference between the peaks in a decoded spectrum obtained by decoded the velocity spectrum for the initial phase according to the set candidate correlates with the spatial arrangement of the transmitting antennas.

3. The radar system according to claim 2, wherein outputting the sensing data includes outputting the sensing data when a signal-to-noise ratio of a peak in an angular spectrum defined from the decoded spectrum falls outside a specified range to the larger side.

4. The radar system of claim 1, wherein outputting the sensing data comprises interrupting output of the sensing data when the phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is not confirmed in the combination of the peak and the initial phase according to the set candidate.

5. The radar system of claim 1, wherein outputting the sensing data includes, when the phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is not confirmed in a combination of the peak and the initial phase according to the set candidate, confirming the phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas in another candidate.

6. The radar system of claim 1, wherein outputting the sensing data includes: setting multiple patterns of candidates assumed for the correspondence between multiple peaks and multiple transmitting antennas; and, when there are multiple candidates for which the phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas has been confirmed, outputting the sensing data for each of the candidates for which the phase difference has been confirmed.

7. A radar control device having a processor (7b) for controlling a radar system (1) equipped with a plurality of transmitting antennas (TX) and at least one receiving antenna (RX), wherein the processor is configured to execute the following: transmitting, from each of the transmitting antennas, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount for each of the repetition periods; and outputting sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received by the receiving antenna; wherein transmitting the transmission signals includes transmitting, from each of the transmitting antennas, the transmission signals to which an initial phase changed according to the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data includes setting candidates for correspondence between a plurality of peaks and a plurality of the transmitting antennas in a velocity spectrum defined from the received signals received by the receiving antenna from the transmission signals from the plurality of the transmitting antennas; and when a phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is confirmed in a combination of the peak and the initial phase according to the set candidate, outputting the sensing data correlated with the received signal for which the correspondence relationship is defined by the candidate.

8. A radar control method executed by a processor (7b) for controlling a radar system (1) having a plurality of transmitting antennas (TX) and at least one receiving antenna (RX), comprising: transmitting, from each of the transmitting antennas, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount for each of the repetition periods; and outputting sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received by the receiving antenna, wherein transmitting the transmission signals comprises transmitting, from each of the transmitting antennas, the transmission signals to which an initial phase changed according to the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data comprises setting candidates for correspondence between a plurality of peaks and a plurality of the transmitting antennas in a velocity spectrum defined from the received signals received by the receiving antenna from the transmission signals from the plurality of the transmitting antennas; and when a phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is confirmed in a combination of the peak and the initial phase according to the set candidate, outputting the sensing data correlated with the received signal for which the correspondence relationship is defined by the candidate.

9. A radar control program stored in a storage medium (7a) and including instructions to be executed by a processor (7b) that controls a radar system (1) having a plurality of transmitting antennas (TX) and at least one receiving antenna (RX), the instructions including: transmitting, from each of the transmitting antennas, a transmission signal whose frequency changes over time in a repetition period and whose phase is shifted over time by a different amount for each of the repetition periods; and outputting sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received by the receiving antenna, wherein transmitting the transmission signals includes transmitting, from each of the transmitting antennas, the transmission signals to which an initial phase changed according to the transmitting antenna is assigned in addition to the shift amount; and outputting the sensing data includes setting candidates for correspondence between a plurality of peaks and a plurality of the transmitting antennas in a velocity spectrum defined from the received signals received by the receiving antenna from the transmission signals from the plurality of transmitting antennas; and when a phase difference between the peaks correlated with the spatial arrangement of the transmitting antennas is confirmed in a combination of the peak and the initial phase according to the set candidate, outputting the sensing data correlated with the received signal for which the correspondence relationship is defined by the candidate.

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