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

Abstract

A processor of this radar system is configured to cause an encoded transmitted signal to be transmitted from individual transmission antennas within overlapping transmission periods in a compensation transmission cycle preceding a measurement transmission cycle. The encoding is defined by a line pertaining to an additional phase for adding a phase shift amount that is an integral multiple of a rotation amount, the phase shift amount being the same within the rotation period of a velocity phase and being random for each rotation period. The processor is configured to acquire a phase offset component correlated with a plurality of decoded signals in a compensation reception cycle. The decoded signals result from a plurality of signal components that correspond to individual chirp signals within the rotation periods being decoded by rearrangement into a phase rotation order shared among the rotation periods. The processor is configured to output sensing data correlated with a received signal from which the phase offset component has been removed.

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. 2024-82711 filed in Japan on May 21, 2024, the contents of which are incorporated by reference in their entirety.

[0002] The present disclosure relates to radar control technology.

[0003] Patent Literature 1 discloses a MIMO (Multiple-Input Multiple-Output) radar system that transmits Doppler Division Multiplexing (DDM) modulated transmission signals from multiple transmission channels. This radar system transmits signals sequentially for each transmission channel. The radar system estimates a periodic phase offset as a phase error due to DDM modulation for each transmission channel.

[0004] US Patent Application Publication No. 2023 / 0129203

[0005] However, if transmission signals are transmitted sequentially from each transmitting antenna in the phase offset estimation process as in Patent Document 1, the transmission process takes a time equal to the number of transmitting antennas. Here, if transmission signals are transmitted from each transmitting antenna in overlapping periods to shorten the transmission process time, it is conceivable to multiplex the transmission signals using code division multiplexing (CDM) modulation. However, CDM modulation makes the phase offset non-periodic. This can make it difficult to estimate the phase offset.

[0006] An object of the present disclosure is to provide a radar system capable of estimating a phase offset while shortening the transmission processing time. Another object of the present disclosure is to provide a radar control device capable of estimating a phase offset while shortening the transmission processing time. Yet another object of the present disclosure is to provide a radar control method capable of estimating a phase offset while shortening the transmission processing time. Yet another object of the present disclosure is to provide a radar control program capable of estimating a phase offset while shortening the transmission processing time.

[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 including a plurality of chirp signals whose frequencies vary over time, and in which the amount of rotation of a velocity phase, which is a phase rotated for each chirp signal by a specific amount of rotation, differs between the transmitting antennas, for each measurement transmission cycle; and output, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received at the receiving antennas, wherein the transmitting signal includes: transmitting, in a compensation transmission cycle before the measurement transmission cycle, transmission signals encoded with a code distinct for each transmitting antenna, the code being defined by a sequence of additional phases that add to each chirp signal a phase shift amount that is the same within the rotation period of the velocity phase and random for each rotation period, and that is an integer multiple of the amount of rotation; and outputting the sensing data includes: transmitting, from each transmitting antenna, in an overlapping transmission period, transmission signals encoded with a code defined by a sequence of additional phases that add to each chirp signal a phase shift amount that is the same within the rotation period of the velocity phase and is random for each rotation period, and that is distinct for each transmitting antenna; In a compensation reception cycle corresponding to the compensation transmission cycle, the method includes acquiring phase offset components correlated to a plurality of decoded signals obtained by rearranging a plurality of signal components correlated to the received signal, the signal components corresponding to each chirp signal within the rotation cycle, into a phase rotation order common between the rotation cycles; and outputting, in a measurement reception cycle following the compensation reception cycle, sensing data correlated to the received signal from which the phase offset components have been removed.

[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, transmission signals including a plurality of chirp signals whose frequencies vary over time, and in which the amount of rotation of a velocity phase, which is a phase rotated for each chirp signal by a specific amount of rotation, differs between the transmitting antennas, in each measurement transmitting cycle; and output, in a measurement receiving cycle corresponding to the measurement transmitting cycle, sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received at the receiving antennas, wherein the transmitting signals include: transmit, in a compensation transmitting cycle before the measurement transmitting cycle, transmission signals encoded with codes distinct for each transmitting antenna, which are defined by a sequence of additional phases that add to each chirp signal a phase shift amount that is the same within the rotation period of the velocity phase and random for each rotation period, and which is an integer multiple of the amount of rotation; and outputting the sensing data includes: In a compensation reception cycle corresponding to the compensation transmission cycle, the method includes acquiring phase offset components correlated to a plurality of decoded signals obtained by rearranging a plurality of signal components correlated to the received signal, the signal components corresponding to each chirp signal within the rotation cycle, into a phase rotation order common between the rotation cycles; and outputting, in a measurement reception cycle following the compensation reception cycle, sensing data correlated to the received signal from which the phase offset components have been removed.

[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, transmission signals each including a plurality of chirp signals whose frequencies vary over time, the transmission signals having different rotation amounts of velocity phases, the phases being rotated for each chirp signal by a specific rotation amount, for each transmitting antenna, in each measurement transmission cycle; and outputting, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received at the receiving antennas, the received signals being the same within the rotation period of the velocity phase and random for each rotation period, the sensed data being distinct for each transmitting antenna; and In a compensation reception cycle corresponding to the compensation transmission cycle, the method includes acquiring phase offset components correlated to a plurality of decoded signals obtained by rearranging a plurality of signal components correlated to the received signal, the signal components corresponding to each chirp signal within the rotation cycle, into a phase rotation order common between the rotation cycles; and outputting, in a measurement reception cycle following the compensation reception cycle, sensing data correlated to the received signal from which the phase offset components have been removed.

[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: transmitting, from each transmitting antenna, transmission signals that include a plurality of chirp signals whose frequencies vary over time, and in which the amount of rotation of a velocity phase, which is a phase that is rotated for each chirp signal by a specific amount of rotation, differs between the transmitting antennas, for each measurement transmission cycle; and outputting, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data that correlates the transmission signals from the plurality of transmitting antennas with received signals received at the receiving antennas, wherein transmitting the transmission signals includes: transmitting, in a compensation transmission cycle before the measurement transmission cycle, transmission signals that are coded with codes that are defined by a sequence of additional phases that add to each chirp signal a phase shift amount that is the same within the rotation period of the velocity phase and is random for each rotation period, and that is an integer multiple of the amount of rotation, from each transmitting antenna, during overlapping transmission periods; and outputting the sensing data includes: In a compensation reception cycle corresponding to the compensation transmission cycle, a phase offset component correlated to a plurality of decoded signals obtained by rearranging a plurality of signal components correlated to the received signal, the signal components corresponding to each chirp signal within the rotation cycle, into a phase rotation order common between the rotation cycles, is acquired; and in a measurement reception cycle following the compensation reception cycle, sensing data correlated to the received signal from which the phase offset component has been removed is output.

[0012] According to these first to fourth aspects, in a compensated reception cycle, the phase offset included in the signal component correlated with the reception signal can be rearranged in a common phase rotation order within a rotation period to ensure periodicity. Therefore, the periodicity of the phase offset can be ensured while transmitting transmission signals in overlapping transmission periods. Therefore, it is possible to estimate the phase offset while shortening the processing time.

[0013] FIG. 1 is a schematic diagram showing an overall configuration of an embodiment; FIG. 2 is a schematic diagram for explaining phases imparted to transmission signals in each transmitting antenna; FIG. 3 is a table showing an example of phases imparted to transmission signals; FIG. 4 is a diagram showing an example of a transmission period and a reception period; FIG. 5 is a diagram for explaining phase offsets; FIG. 6 is a block diagram showing the functional configuration of a control unit in a radar system; FIG. 7 is a flowchart showing a radar control flow according to an embodiment; FIG. 8 is a flowchart showing details of a phase offset estimation process; FIG. 9 is a diagram for explaining a decoding process; FIG. 10 is a diagram for explaining a phase offset estimation process; FIG. 11 is a graph showing an example of the relationship between a side lobe and a peak; and FIG. 12 is a table showing an example of a phase imparted to a transmission signal in a comparative example.

[0014] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0015] First Embodiment A first embodiment of the present disclosure will be described with reference to FIGS. 1 to 11 . 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. As shown in FIG. 2 , the signal generator 4 generates a chirp signal modulated so that the frequency varies 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 compensation transmission cycle Tt_c and measurement transmission cycle Tt_m as transmission cycles. The number of chirp signals is, for example, an even number. The number of chirp signals is constant throughout all transmission cycles, regardless of the compensation transmission cycle Tt_c and measurement transmission cycle Tt_m. 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 and other figures, the chirp signals are shown as so-called up-chirp signals whose frequency increases over time. However, the chirp signals may also be so-called down-chirp signals 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 change to the input transmission signal. More specifically, the phase shifter 51 imparts at least a phase change that rotates the multiple chirp signals arranged in time by a substantially constant amount of rotation for each chirp period Tc. As a result, the multiple transmission signals transmitted from the multiple transmission antennas TX are subjected to so-called Doppler division multiplexing (DDM) modulation. In the following description, it is assumed that the radar device 1 is provided with a total of m transmission antennas TX. In order to distinguish between the individual transmission antennas TX, an index i (i is a natural number from 1 to m) may be added to the end of the symbol "TX" to distinguish them.

[0023] For example, as shown in FIG. 2, a transmission signal transmitted from a specific transmission antenna TX1 among a plurality of transmission antennas TX is rotated by an amount of rotation ω １ In this case, the k-th chirp signal in the transmission signal is rotated by an amount ω １ The phase is rotated by a factor of 1 / Tc times the chirp number. 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 amount of rotation. The above phase change can also be referred to as a Doppler shift. Each phase shifter 51 imparts a rotation amount in both the compensation transmission cycle Tt_c and the measurement transmission cycle Tt_m.

[0024] In FIG. 2, the chirp number k ranges from "1" to "N", which is the maximum number of chirp signals in one transmission cycle. ｃ However, the chirp number k ranges from "0" to "N ｃ It may be set from any number to any number, such as "-1".

[0025] Each of the phase shifters 51 applies a different rotation amount. That is, in FIG. 2, for a plurality of chirp signals transmitted from a transmitting antenna TX2 different from the transmitting antenna TX1, the rotation amount ω １ A rotation amount ω different from ２ Similarly, for the transmitting antenna TXm, the rotation amount ω is given to the plurality of chirp signals to be transmitted. １ , ω ２ The rotation amount ω is different from ｍ Each phase shifter 51 may impart the same amount of rotation to the chirp signal for each transmission cycle. Alternatively, each phase shifter 51 may impart a different amount of rotation for each transmission cycle in response to a control command from the control unit 7.

[0026] Hereinafter, the initial phase rotated by the rotation amount in each chirp signal may be referred to as the DDM phase. For example, assume that the rotation amount is π / 2 and the initial phase of the first chirp signal is 0. In this case, as shown in FIG. 3, the DDM phase of the second chirp signal is π / 2, the DDM phase of the third chirp signal is π, and the DDM phase of the fourth chirp signal is 3π / 2. Then, the DDM phase completes one cycle with the fifth chirp signal. In other words, when the rotation amount is π / 2, the rotation period Tr of the DDM phase is four chirp signals. The DDM phase is an example of a "velocity phase."

[0027] Furthermore, in a compensation transmission cycle Tt_c before the measurement transmission cycle Tt_m, the phase shifter 51 encodes the transmission signal with a different code for each transmission antenna TX in addition to DDM modulation, so that the transmission signal is subjected to so-called code division multiplexing (CDM) modulation.

[0028] Here, a code is a sequence of phases added to a series of chirp signals within a transmission cycle. Hereinafter, each phase constituting a code may be referred to as a CDM phase. The CDM phase constituting a code is the same within a rotation period Tr of the DDM phase and is a phase that is an integer multiple of the rotation amount, which is random for each rotation period Tr. For example, a code is one in which a random half-rotation offset is added as a phase shift amount for each rotation period Tr. Specifically, the code is a sequence of pseudo-random CDM phases of "0" and "π." The code may be, for example, an M-sequence code or an APAS code. Alternatively, the code may be a Gold code or a ZCZ code. Alternatively, the code may be a code of any type to which any CDM phase has been added so that the number of "0"s and "π"s is the same. The CDM phase is an example of an "additional phase."

[0029] Also, the code is the chirp number N ｃ The number of DDM phases is N ｐｈ The small code, which is a code of the code length divided by the DDM phase number N ｐｈ Here, the number of DDM phases N ｐｈ is the number of DDM phases in one rotation period Tr. For example, the chirp number N ｃ is 16, the number of DDM phases is N ｐｈ is 4, the code is composed of a sequence in which each CDM phase constituting a small code with a code length of 4 is repeated four times.

[0030] Due to the above coding, the multiple chirp signals that pass through the phase shifter 51 in the compensated transmission cycle Tt_c are assigned a coded phase that is the sum of the DDM phase and the CDM phase. For example, in the example shown in FIG. 3 , assume that the CDM phase for chirp numbers 1 to 4 and 9 to 12 is 0, and the CDM phase for chirp numbers 5 to 8 is π. In this case, the coded phases for chirp numbers 1 to 4 and 9 to 12 are the same as the DDM phase. The coded phases for chirp numbers 5 to 8 are π, 3π / 2, 0, and π / 2, in ascending order of chirp number. In practice, the phase shifter 51 assigns coded phases, which are pre-designed as a combination of the DDM phase and the CDM phase, to each input chirp signal.

[0031] Each phase shifter 51 may assign the same code to the chirp signal for each transmission cycle, or may assign a different code for each transmission cycle 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.

[0032] 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 includes at least one antenna element. For example, the transmitting antenna TX is a patch antenna having 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 different rotation amount for each transmitting antenna TX by the corresponding phase shifter 51. Furthermore, each transmission signal transmitted from each of the multiple transmitting antennas TX in the compensation transmission cycle Tt_c is encoded with a different code for each transmitting antenna TX by the corresponding phase shifter 51.

[0033] As a result, as shown in Fig. 2, each transmitting antenna TX transmits a specified number of chirp signal groups as transmission signals for each compensation transmission cycle Tt_c and measurement transmission cycle Tt_m. The transmission cycles Tt_c and Tt_m are synchronized between the transmitting antennas TX. That is, the transmission of each transmission signal from each transmitting antenna TX starts substantially simultaneously.

[0034] The receiving antenna RX receives, as a received signal, a radio wave signal including a transmitted signal reflected by a target as a reflector in the external 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 that are mixed together in the mixed received signal will be referred to as received signal components.

[0035] 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.

[0036] The receiving circuit 6 is connected to the receiving antenna RX and acquires a received signal received by the receiving antenna RX. The receiving circuit 6 acquires a received signal as a reflected signal of a transmitted signal reflected by a target for each compensation receiving cycle Tr_c and measurement receiving cycle Tr_m as receiving cycles. The compensation receiving cycle Tr_c corresponds to the compensation transmitting cycle Tt_c. The measurement receiving cycle Tr_m corresponds to the measurement transmitting cycle Tt_m. As shown in FIG. 4, each receiving cycle is synchronized with the corresponding transmitting cycle. Furthermore, the receiving cycles are synchronized between receiving channels. The receiving circuit 6 includes amplifiers 61, signal mixing units 62, and AD converters 63, the number of which is the same as the number of connected receiving antennas RX.

[0037] 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.

[0038] 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.

[0039] In the above-described transceiver unit 2, the transmission signals transmitted from each transmitting antenna TX contain a phase offset as an error relative to the imparted phase change. The phase offset is caused by hardware in the transmission circuit 5, such as the phase shifter 51. The phase offset is an error whose magnitude corresponds to the overall value of the imparted phase. That is, in the measurement transmission cycle Tt_m, only the DDM phase is imparted to the chirp signal, so each chirp signal contains a phase offset corresponding to the DDM phase. Furthermore, in the compensation transmission cycle Tt_c, a phase offset corresponding to the encoded phase, which is the sum of the DDM phase and the CDM phase, is contained.

[0040] For example, in the measurement transmission cycle Tt_m, when the rotation amount is π / 2 as shown in FIG. 3, each chirp signal with a DDM phase of 0, π / 2, π, or 3π / 2 contains a different phase offset. The phase offsets corresponding to the DDM phases 0, π / 2, π, and 3π / 2 are denoted by δ in this order. ０ , δ ９０ , δ １８０ , δ ２７０ In this case, as shown in Fig. 5, a phase offset occurs periodically as a spurious signal with the same period as the rotation period Tr.

[0041] The time waveform of such periodic phase offset can be assumed to be composed of a linear sum of sine waves. Therefore, if a phase offset is included in a transmission signal, multiple periodic peaks (spurious peaks) will appear in the Doppler spectrum of the corresponding beat signal. Such phase offset changes depending on temperature, aging of the transmission circuit 5, and the like. Therefore, when compensating for the phase offset, it may be necessary to periodically estimate and update the actual phase offset.

[0042] The control unit 7 processes the acquired beat signal. The control unit 7 estimates and compensates for the phase offset described above. The control unit 7 is connected to the transceiver unit 2 via at least one of, for example, a local area network (LAN) line, a wire harness, an internal bus, and a wireless communication line. The configuration of the control unit 7 will be described later.

[0043] 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.

[0044] 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).

[0045] The dedicated computer constituting the control unit 7 has at least one memory 7a and one processor 7b. The memory 7a is at least one type of non-transitory tangible storage medium, such as a semiconductor memory, a magnetic medium, or an optical medium, that non-temporarily stores computer-readable programs and data. 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 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).

[0046] 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. 6. The control unit 7 is an example of a "radar control device."

[0047] 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 Figures 7 and 8. 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.

[0048] First, in S10 of Fig. 7, a phase offset estimation process is executed. More specifically, first, in S101 of Fig. 8, the transmission process block 71 outputs a command to start transmission process to the transceiver unit 2, thereby causing the transmission signal to be transmitted from the multiple transmission antennas TX. As described above, the transmission signal is given a different rotation amount and sign for each transmission antenna TX by the action of the phase shifter 51.

[0049] 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 rotation amount and code. Alternatively, the transmission processing block 71 may change the rotation amount and code for each compensation transmission cycle Tt_c.

[0050] Next, in S102, the reception processing block 72 acquires, from each reception circuit 6, beat signals defined from the reception signals acquired for each reception antenna RX. Then, in S103, the reception processing block 72 acquires a distance spectrum using the beat signals defined from the reception signals received at 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 compensated reception cycle Tr_c.

[0051] Specifically, the reception processing block 72 performs a Fast Fourier Transform (FFT) on the beat signal. As a result, the reception processing block 72 acquires a distance spectrum, which is a spectrum that exhibits peaks at frequency positions corresponding to the distance to the target, for each chirp signal. The distance spectrum data includes signal strength information for each distance bin according to the distance resolution. Each distance spectrum for each chirp signal is an example of a "signal component correlated to the received signal."

[0052] Next, in S104, the reception processing block 72 sets i = 1 to perform iterative processing. Then, in S105, the reception processing block 72 executes decoding processing on the distance spectrum in accordance with the code assigned to the transmission signal from the transmission antenna TXi.

[0053] In the decoding process, the receiver processing block 72 rearranges the distance spectra corresponding to each chirp signal into a phase rotation order common to the corresponding rotation periods Tr, as shown in FIG. 9 . For example, in the example shown in FIG. 3 , the time series of distance spectra corresponding to chirp signals with chirp numbers 5 to 8 includes encoded phases of [π, 3π / 2, 0, π / 2]. The receiver processing block 72 rearranges the distance spectra arranged in this time series into a phase rotation order common to other rotation periods Tr. For example, the receiver processing block 72 rearranges the distance spectra in ascending order of encoded phase so that the phase rotation order is common to the phase rotation order of [0, π / 2, π, 3π / 2] of the encoded phases of the distance spectra in a rotation period Tr in which the CDM phase is "0." The group of distance spectra resulting from the above decoding process is an example of a "decoded signal."

[0054] In the following S106, the reception processing block 72 acquires a Doppler spectrum using the group of distance spectra that have been subjected to the decoded processing. To describe the acquisition of the Doppler spectrum in more detail, the reception processing block 72 performs a second FFT process on the sequence of distance spectra. In the second FFT process, the reception processing block 72 performs FFT processing on a waveform in which the phases at the distance bins obtained in the first FFT process are arranged in the order after decoding. As a result of the second FFT process, the reception processing block 72 acquires, for each distance bin, a frequency spectrum (Doppler spectrum) that shows a peak at a position corresponding to the Doppler velocity (relative velocity) of the target. In this way, the reception processing block 72 acquires a two-dimensional spectrum of the distance R and the Doppler velocity V. The Doppler spectrum is also called a velocity spectrum, and the two-dimensional spectrum is also called an RV map.

[0055] In the next step S107, the reception processing block 72 acquires spurious data. Specifically, the reception processing block 72 generates spurious data by utilizing the fact that the Doppler spectrum can be defined by the convolution of the DDM modulation component and the phase offset component as shown in FIG. 10. Note that φ in FIG. 10 ＤＤＭ where (k) is the DDM phase of the kth chirp signal, and Δφ(k) is the phase offset of the kth chirp signal. First, the reception processing block 72 performs a cyclic shift on the Doppler spectrum so that the peaks are arranged in order from the zeroth-order spurious component. Then, the reception processing block 72 removes peak components derived from the target from the spectrum after the cyclic shift. As a result, the reception processing block 72 obtains a spectrum containing peaks derived from spurious components (spurious spectrum) as spurious data.

[0056] Next, in S108, the reception processing block 72 estimates the phase offset contained in the transmission signal of the transmitting antenna TXi. Specifically, as shown in FIG. 10, the reception processing block 72 obtains a time waveform of the phase offset by performing an inverse fast fourier transform (IFFT) process on the spurious data. Then, the reception processing block 72 extracts and obtains each phase offset from the obtained time waveform. For example, when the rotation amount of the DDM modulation is π / 2, the reception processing block 72 obtains the phase offset δ ０ , δ ２７０ , δ １８０ , δ ２７０ Get.

[0057] Then, in S109, the reception processing block 72 stores the estimated phase offsets of each transmitting antenna TXi in a storage medium such as the memory 7a. Next, in S110, the reception processing block 72 counts up i to i+1. Then, in S112, the reception processing block 72 determines whether the value of i after counting up exceeds the number m of transmitting antennas TX. If it is determined that i does not exceed the number m, that is, that phase offset estimation has not been completed for all transmitting antennas TX, the flow returns to S105. On the other hand, if it is determined that i exceeds the number m, that is, that phase offset estimation has been completed for all transmitting antennas TX, the flow ends and returns to S20 in FIG. 7.

[0058] Returning to FIG. 7 , in S20, the transmission processing block 71 transmits a transmission signal in the measurement transmission cycle Tt_m. Next, in S30, the reception processing block 72 acquires, from the reception circuit 6, a beat signal that correlates with the reception signal received in the measurement reception cycle Tr_m. Next, in S40, the reception processing block 72 acquires a Doppler spectrum. Next, in S50, the reception processing block 72 performs phase offset compensation processing based on the phase offset acquired in the previous compensation reception cycle Tr_c. For example, the reception processing block 72 may generate a spurious spectrum from the stored phase offset and subtract it from the Doppler spectrum to compensate for the phase offset.

[0059] Next, in S60, the reception processing block 72 performs angle measurement processing on the Doppler spectrum corresponding to each transmitting antenna TX. That is, the reception processing block 72 performs a third FFT process on a waveform obtained by arranging the phases of each peak in an integrated spectrum obtained by integrating multiple Doppler spectra. As a result, the reception processing block 72 obtains an angle spectrum showing peaks at positions corresponding to the relative angle from the target. Note that the FFT process in S100 is performed using a group of beat signals corresponding to a group of received signals obtained by receiving signals from multiple transmitting antennas TX at multiple receiving antennas RX. For this reason, this FFT process is also referred to as MIMO angle measurement processing.

[0060] Furthermore, in S70, the reception processing block 72 outputs sensing data. The reception processing block 72 outputs information about the target, such as the distance to the target, the relative speed, and the relative angle, as sensing data. The distance information, relative speed information, and relative angle information are information that correlates the transmission signals from the multiple transmission antennas TX with the reception signals received by each of the multiple reception antennas RX, obtained by the MIMO angle measurement process.

[0061] The control unit 7 repeatedly executes the above series of processes during the activation of the radar device 1. As a result, the control unit 7 of the first embodiment transmits a transmission signal in the compensation transmission cycle Tt_c every time before the measurement transmission cycle Tt_m.

[0062] According to the first embodiment described above, in the compensated reception cycle Tr_c, the phase offset included in the distance spectrum, which is a signal component correlated with the reception signal, can be rearranged into a common phase rotation order over the rotation cycle Tr, thereby ensuring periodicity. Therefore, it is possible to avoid the spread of spurious signals in the Doppler spectrum while transmitting transmission signals in overlapping transmission periods. Therefore, it is possible to estimate the phase offset while shortening the processing time.

[0063] For example, as a comparative example, consider a case where a transmission signal is transmitted that is coded with a code defined by a sequence of non-identical CDM phases within a rotation period Tr of the DDM phase (see FIG. 12). In FIG. 12, of the first to fourth chirp signals, only the second one is assigned a CDM phase of "π", and the other CDM phases are "0". Therefore, within this rotation period Tr, the phase offset is "δ ０ , δ ２７０ , δ １８０ , δ ２７０ Furthermore, for the fifth to eighth chirp signals, "π" is assigned as the CDM phase to the fifth, sixth, and eighth chirp signals, and the CDM phase of the seventh chirp signal is "0". Therefore, within this rotation period Tr, the phase offset is "δ １８０ , δ ２７０ , δ １８０ , δ ９０". In other words, the phase offset has lost its periodicity, and it is also impossible to rearrange the distance spectra into a common phase rotation order over the rotation period Tr. Note that even if only the distance spectrum to which the CDM phase of "π" is assigned is encoded and then decoded by inverting the phase, the phase offset assigned at the time of transmission remains unchanged.

[0064] Therefore, in this comparative example, since the phase offset is not periodic, at least one spurious peak is spread in the Doppler spectrum. Therefore, it may be impossible to reliably estimate the phase offset of each DDM phase. On the other hand, in the first embodiment, since the phase offset is periodic as described above, it is possible to achieve both a reduction in processing time and estimation of the phase offset.

[0065] Furthermore, according to the first embodiment, a transmit signal is transmitted that is encoded with a code defined by a sequence of CDM phases that randomly imparts a phase shift of half a rotation for each rotation period Tr of the DDM phase, which makes it possible to encode the transmit signal with a code that is easier to generate.

[0066] Furthermore, according to the first embodiment, a transmission signal is transmitted in which each additional phase in a small code having a code length obtained by dividing the number of chirp signals in the transmission signal by the number of phase rotations within a rotation period Tr is encoded with consecutive codes every rotation period Tr. Therefore, as shown in FIG. 11 , it becomes easier to prevent peaks and spurious peaks originating from targets from being buried in side lobes in the Doppler spectrum.

[0067] (Other Embodiments) Although one embodiment has been described above, the present disclosure should not be construed as being limited to the embodiment described above, and can be applied to various embodiments and combinations within the scope that does not deviate from the gist of the present disclosure.

[0068] In a modified example, the control unit 7 may set the compensation transmission cycle Tt_c next to the previous compensation transmission cycle Tt_c after multiple measurement transmission cycles Tt_m following the previous compensation transmission cycle Tt_c. In other words, the control unit 7 does not necessarily need to estimate the phase offset before each measurement transmission cycle Tt_m. The control unit 7 may periodically estimate and update the phase offset by setting the compensation transmission cycle Tt_c for each predetermined number of measurement transmission cycles Tt_m. Alternatively, the control unit 7 may perform phase offset estimation when a specific condition related to the state of the radar device 1 or the vehicle on which the radar device 1 is installed is met.

[0069] In a modified example, the reception processing block 72 in S105 may perform decoding processing for each distance spectrum group corresponding to each reception antenna RX. The reception processing block 72 may perform processing in S106 to S108 for each distance spectrum group and acquire a phase offset that combines the processing results.

[0070] In a modified example, the transmission processing block 71 may transmit a transmission signal that has been subjected to CDM modulation in addition to DDM modulation, also in the measurement transmission cycle Tt_m.

[0071] 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. In this case, the "radar system" includes the radar device 1 and the processor of the on-board ECU.

[0072] 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 reception signal received by the single receiving antenna RX.

[0073] 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.

[0074] 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.

[0075] (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.

[0076] (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 perform the following: transmit, from each of the transmitting antennas, transmission signals each including a plurality of chirp signals whose frequency varies over time, and in which the rotation amount of a velocity phase, which is a phase rotated for each of the chirp signals by a specific rotation amount, differs between the transmitting antennas, for each measurement transmission cycle; and output, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data in which the transmission signals from the plurality of transmitting antennas are correlated with reception signals received by the receiving antennas, wherein the transmitting of the transmission signals includes: transmitting, from each of the transmitting antennas, during an overlapping transmission period, in a compensation transmission cycle before the measurement transmission cycle, the transmission signals encoded with a code defined by a sequence of additional phases that add to each of the chirp signals a phase shift amount that is the same within a rotation period of the velocity phase and is random for each rotation period, the phase shift amount being an integer multiple of the rotation amount; and outputting the sensing data a compensation reception cycle corresponding to the compensation transmission cycle, acquiring phase offset components correlated to a plurality of decoded signals obtained by decoded signal components correlated to the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, by rearranging the signal components into a phase rotation order common between the rotation cycles; and outputting the sensing data correlated to the received signal from which the phase offset components have been removed, in the measurement reception cycle after the compensation reception cycle.

[0077] (Technical Idea 2) The radar system according to Technical Idea 1, wherein transmitting the transmission signal includes transmitting the transmission signal encoded with the code defined by a sequence of the additional phases that randomly imparts the phase shift amount of half a rotation for each rotation period of the velocity phase.

[0078] (Technical Idea 3) A radar system according to Technical Idea 1 or Technical Idea 2, in which transmitting the transmission signal includes transmitting the transmission signal encoded with the code such that the number of chirp signals to which the phase shift amount is assigned is equal to the number of chirp signals to which the phase shift amount is not assigned.

[0079] (Technical Idea 4) A radar system according to any one of Technical Ideas 1 to 3, wherein transmitting the transmission signal includes transmitting the transmission signal in which each of the additional phases constituting a small code having a code length obtained by dividing the number of chirp signals in the transmission signal by the number of phase rotations within the rotation period is encoded with the code that continues for each rotation period.

[0080] The above technical concepts 1 to 4 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: transmit, from each of the transmitting antennas, transmission signals each including a plurality of chirp signals whose frequencies vary over time, the transmission signals having a velocity phase that is rotated for each of the chirp signals by a specific rotation amount, the rotation amount of the velocity phase being different between the transmitting antennas, in each measurement transmission cycle; and output, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received at the receiving antennas, wherein transmitting the transmission signals includes: transmitting, in a compensation transmission cycle before the measurement transmission cycle, the transmission signals coded with a code defined by a sequence of additional phases that add to each of the chirp signals a phase shift amount that is the same within the rotation period of the velocity phase and is random for each rotation period, the phase shift being an integer multiple of the rotation amount, the code being distinct for each of the transmitting antennas; and outputting the sensing data. a compensation reception cycle corresponding to the compensation transmission cycle, acquiring phase offset components correlated to a plurality of decoded signals obtained by decoded signal components correlated to the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, by rearranging the signal components into a phase rotation order common between the rotation cycles; and outputting the sensing data correlated to the received signal from which the phase offset components have been removed, in the measurement reception cycle after the compensation reception cycle.

2. The radar system according to claim 1, wherein transmitting the transmission signal includes transmitting the transmission signal encoded with the code defined by a sequence of the additional phases that randomly imparts the phase shift amount of half a rotation to each rotation period of the velocity phase.

3. The radar system according to claim 1, wherein transmitting the transmission signal includes transmitting the transmission signal encoded with the code such that the number of chirp signals to which the phase shift amount is applied is equal to the number of chirp signals to which the phase shift amount is not applied.

4. The radar system according to claim 1, wherein transmitting the transmission signal includes transmitting the transmission signal in which each of the additional phases constituting a small code having a code length obtained by dividing the number of chirp signals in the transmission signal by the number of phase rotations within the rotation period is encoded with the code that continues for each rotation period.

5. 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, transmission signals including a plurality of chirp signals whose frequencies change over time, and in which the rotation amount of a velocity phase, which is a phase rotated for each of the chirp signals by a specific rotation amount, differs between the transmitting antennas, for each measurement transmission cycle; and outputting, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received at the receiving antennas, wherein transmitting the transmission signals includes transmitting, from each of the transmitting antennas, during an overlapping transmission period, the transmission signals encoded with a code defined by a sequence of additional phases that add to each of the chirp signals a phase shift amount that is the same within the rotation period of the velocity phase and is random for each rotation period, the phase shift being an integer multiple of the rotation amount; and outputting the sensing data a compensation reception cycle corresponding to the compensation transmission cycle, acquiring phase offset components correlated with a plurality of decoded signals obtained by decode- ing a plurality of signal components correlated with the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, by rearranging the signal components into a phase rotation order common between the rotation cycles; and outputting the sensing data correlated with the received signal from which the phase offset components have been removed, in the measurement reception cycle after the compensation reception cycle.

6. 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, transmission signals each including a plurality of chirp signals whose frequency varies over time, the rotation amount of a velocity phase being a phase rotated for each of the chirp signals by a specific rotation amount, which varies among the transmitting antennas, in each measurement transmission cycle; and outputting, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data correlating the transmission signals from the plurality of transmitting antennas with received signals received at the receiving antennas, wherein transmitting the transmission signals comprises transmitting, in a compensation transmission cycle before the measurement transmission cycle, the transmission signals coded with a code defined by a sequence of additional phases that add to each of the chirp signals a phase shift amount that is the same within the rotation period of the velocity phase and is random for each rotation period, the phase shift being an integer multiple of the rotation amount, from each of the transmitting antennas, in an overlapping transmission period; and outputting the sensing data comprises a compensation reception cycle corresponding to the compensation transmission cycle, acquiring phase offset components correlated with a plurality of decoded signals obtained by decode- ing a plurality of signal components correlated with the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, by rearranging the signal components into a phase rotation order common between the rotation cycles; and outputting the sensing data correlated with the received signal from which the phase offset components have been removed, in the measurement reception cycle after the compensation reception cycle.

7. 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, transmission signals including a plurality of chirp signals whose frequencies change over time, the rotation amount of a velocity phase being a phase rotated for each of the chirp signals by a specific rotation amount, which varies among the transmitting antennas, in each measurement transmission cycle; and outputting, in a measurement reception cycle corresponding to the measurement transmission cycle, sensing data correlating the transmission signals from the plurality of transmitting antennas with reception signals received by the receiving antennas, wherein transmitting the transmission signals includes transmitting, from each of the transmitting antennas, during overlapping transmission periods, in a compensation transmission cycle before the measurement transmission cycle, the transmission signals encoded with a code defined by a sequence of additional phases that add to each of the chirp signals a phase shift amount that is the same within the rotation period of the velocity phase and is random for each rotation period, the phase shift amount being an integer multiple of the rotation amount, the code being distinct for each of the transmitting antennas; The outputting of the sensing data includes: acquiring, in a compensated reception cycle corresponding to the compensated transmission cycle, phase offset components correlated to a plurality of decoded signals obtained by decoded signal components correlated to the received signal, the plurality of signal components corresponding to each of the chirp signals within the rotation cycle, by rearranging the signal components into a phase rotation order common between the rotation cycles; and outputting, in the measurement reception cycle after the compensated reception cycle, the sensing data correlated to the received signal from which the phase offset components have been removed.

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