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

Abstract

To provide a radar system and the like that can estimate a phase offset while shortening a transmission processing time.SOLUTION: A processor of a radar system is configured to execute, in a compensation transmission cycle prior to a measurement transmission cycle, causing each transmission antenna to transmit an encoded transmission signal within an overlapping transmission period. A code is defined by a sequence of additional phases that add a phase shift amount that is the same within a rotation cycle of a velocity phase and random for each rotation cycle, and is an integer multiple of a rotation amount. The processor is configured to execute, in a compensation reception cycle, acquisition of phase offset components correlated to a plurality of decoded signals. The decoded signals are signals decoded by rearranging multiple signal components corresponding to each chirp signal within the rotation cycle into a phase rotation order that is common between rotation cycles. The processor is also configured to execute output of sensing data correlated with the received signal from which the phase offset components have been removed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to radar control technology. [Background technology]

[0002] Patent Document 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2023 / 0129203 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if transmit signals are transmitted sequentially from each transmit antenna in the phase offset estimation process as in Patent Document 1, the transmission process takes as much time as the number of transmit antennas. To shorten the transmission process time, if transmit signals are transmitted from each transmit antenna in overlapping periods, it is conceivable to multiplex the transmit signals using Code Division Multiplex (CDM) modulation. However, CDM modulation makes the phase offset non-periodic. This can make it difficult to estimate the phase offset.

[0005] 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. [Means for solving the problem]

[0006] The technical means of the present disclosure for solving the problems will be described below. Note that the claims and the reference symbols in parentheses in this section 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.

[0007] A first aspect of the present disclosure is a radar system having a plurality of transmit antennas (TX), at least one receive antenna (RX), and a processor (7b), The processor transmitting, from each transmitting antenna for each measurement transmission cycle, a transmission signal including a plurality of chirp signals whose frequencies change over time, and in which the rotation amount of the velocity phase, which is the phase rotated for each chirp signal by a specific rotation amount, differs between the transmitting antennas; outputting sensing data correlating with received signals obtained by receiving signals from a plurality of transmitting antennas at a receiving antenna in a measurement receiving cycle corresponding to the measurement transmitting cycle; configured to run To transmit a transmission signal is In a compensation transmission cycle before the measurement transmission cycle, a transmission signal is transmitted from each transmission antenna during the overlapping transmission period, the transmission signal being coded with a code defined by a sequence of additional phases that adds to each chirp signal a phase shift amount that is the same within a rotation period of the velocity phase and random for each rotation period, the phase shift amount being an integer multiple of the rotation amount, and the code being distinct for each transmission antenna; Outputting sensing data is In a compensated reception cycle corresponding to the compensated transmission cycle, a plurality of signal components correlated with the received signal, the signal components corresponding to each chirp signal within the rotation cycle, are decoded by rearranging the signal components into a common phase rotation order between the rotation cycles, thereby obtaining phase offset components correlated with a plurality of decoded signals; In a measurement receive cycle after the compensation receive cycle, outputting sensing data correlated with the receive signal from which the phase offset component has been removed; Includes.

[0008] A second aspect of the present disclosure is a radar control device having a processor (7b) for controlling a radar system (1) having a plurality of transmitting antennas (TX) and at least one receiving antenna (RX), The processor transmitting, from each transmitting antenna for each measurement transmission cycle, a transmission signal including a plurality of chirp signals whose frequencies change over time, and in which the rotation amount of the velocity phase, which is the phase rotated for each chirp signal by a specific rotation amount, differs between the transmitting antennas; outputting sensing data correlating with received signals obtained by receiving signals from a plurality of transmitting antennas at a receiving antenna in a measurement receiving cycle corresponding to the measurement transmitting cycle; configured to run To transmit a transmission signal is In a compensation transmission cycle before the measurement transmission cycle, a transmission signal is transmitted from each transmission antenna during the overlapping transmission period, the transmission signal being coded with a code defined by a sequence of additional phases that adds to each chirp signal a phase shift amount that is the same within a rotation period of the velocity phase and random for each rotation period, the phase shift amount being an integer multiple of the rotation amount, and the code being distinct for each transmission antenna; Outputting sensing data is In a compensated reception cycle corresponding to the compensated transmission cycle, a plurality of signal components correlated with the received signal, the signal components corresponding to each chirp signal within the rotation cycle, are decoded by rearranging the signal components into a common phase rotation order between the rotation cycles, thereby obtaining phase offset components correlated with a plurality of decoded signals; In a measurement receive cycle after the compensation receive cycle, outputting sensing data correlated with the receive signal from which the phase offset component has been removed; Includes.

[0009] A third aspect of the present disclosure provides 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), the method comprising: transmitting, from each transmitting antenna for each measurement transmission cycle, a transmission signal including a plurality of chirp signals whose frequencies change over time, and in which the rotation amount of the velocity phase, which is the phase rotated for each chirp signal by a specific rotation amount, differs between the transmitting antennas; outputting sensing data correlating with received signals obtained by receiving signals from a plurality of transmitting antennas at a receiving antenna in a measurement receiving cycle corresponding to the measurement transmitting cycle; Including, To transmit a transmission signal is In a compensation transmission cycle before the measurement transmission cycle, a transmission signal is transmitted from each transmission antenna during the overlapping transmission period, the transmission signal being coded with a code defined by a sequence of additional phases that adds to each chirp signal a phase shift amount that is the same within a rotation period of the velocity phase and random for each rotation period, the phase shift amount being an integer multiple of the rotation amount, and the code being distinct for each transmission antenna; Outputting sensing data is In a compensated reception cycle corresponding to the compensated transmission cycle, a plurality of signal components correlated with the received signal, the signal components corresponding to each chirp signal within the rotation cycle, are decoded by rearranging the signal components into a common phase rotation order between the rotation cycles, thereby obtaining phase offset components correlated with a plurality of decoded signals; In a measurement receive cycle after the compensation receive cycle, outputting sensing data correlated with the receive signal from which the phase offset component has been removed; Includes.

[0010] A fourth aspect of the present disclosure provides 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 program comprising: The command is, transmitting, from each transmitting antenna for each measurement transmission cycle, a transmission signal including a plurality of chirp signals whose frequencies change over time, and in which the rotation amount of the velocity phase, which is the phase rotated for each chirp signal by a specific rotation amount, differs between the transmitting antennas; outputting sensing data correlating with received signals obtained by receiving signals from a plurality of transmitting antennas at a receiving antenna in a measurement receiving cycle corresponding to the measurement transmitting cycle; Including, To transmit a transmission signal is In a compensation transmission cycle before the measurement transmission cycle, a transmission signal is transmitted from each transmission antenna during the overlapping transmission period, the transmission signal being coded with a code defined by a sequence of additional phases that adds to each chirp signal a phase shift amount that is the same within a rotation period of the velocity phase and random for each rotation period, the phase shift amount being an integer multiple of the rotation amount, and the code being distinct for each transmission antenna; To output sensing data, In a compensated reception cycle corresponding to the compensated transmission cycle, a plurality of signal components correlated with the received signal, the signal components corresponding to each chirp signal within the rotation cycle, are decoded by rearranging the signal components into a common phase rotation order between the rotation cycles, thereby obtaining phase offset components correlated with a plurality of decoded signals; In a measurement reception cycle after the compensation reception cycle, outputting sensing data correlated with the reception signal from which the phase offset component has been removed; Includes.

[0011] According to these first to fourth aspects, in a compensated reception cycle, the phase offsets included in the signal components correlated with the reception signal can be rearranged in a common phase rotation order within a rotation period, thereby ensuring periodicity. Therefore, the periodicity of the phase offsets 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. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram illustrating an overall configuration of an embodiment. [Figure 2] 3A and 3B are schematic diagrams for explaining phases assigned to transmission signals at each transmitting antenna. [Figure 3] 10 is a table showing an example of a phase assigned to a transmission signal. [Figure 4] FIG. 2 is a diagram illustrating an example of a transmission period and a reception period. [Figure 5] FIG. 10 is a diagram illustrating a phase offset. [Figure 6] FIG. 2 is a block diagram showing the functional configuration of a control unit in the radar system. [Figure 7] 1 is a flowchart illustrating a radar control flow according to an embodiment. [Figure 8] 10 is a flowchart showing details of a phase offset estimation process. [Figure 9] FIG. 10 is a diagram illustrating a decoding process. [Figure 10] FIG. 10 is a diagram for explaining a process of estimating a phase offset. [Figure 11] 10 is a graph showing an example of the relationship between a side lobe and a peak. [Figure 12] 10 is a table showing an example of a phase assigned to a transmission signal in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0014] (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."

[0015] 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.

[0016] 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.

[0017] 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 transmission signals and reception processing of reception signals. 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.

[0018] 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 its 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 the 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.

[0019] 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.

[0020] The transmitting circuit 5 and the receiving circuit 6 are each mainly composed of a semiconductor integrated circuit device such as an MMIC (Monolithic Microwave Integrated Circuit). The transmitting circuit 5 is connected to a transmitting antenna TX and outputs a transmission signal to the transmitting antenna TX. The transmitting circuit 5 includes the same number of phase shifters 51 and amplifiers 52 as the number of connected transmitting antennas TX.

[0021] 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 a plurality of chirp signals arranged in time by a substantially constant amount of rotation for each chirp period Tc. As a result, the plurality of transmission signals transmitted from the plurality of 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.

[0022] For example, as shown in FIG. 2, suppose a rotation amount ω1 is imparted to a transmission signal transmitted from a specific transmitting antenna TX1 among multiple transmitting antennas TX. In this case, the phase of the kth chirp signal in the transmission signal is rotated by the chirp number multiplied by the rotation amount ω1 relative to the phase before input to the phase shifter 51. As a result, the phases of multiple chirp signals aligned in time that have passed through the phase shifter 51 change linearly for each chirp period Tc. This linear change in phase imparts a pseudo Doppler velocity corresponding to the rotation amount to the chirp signal. This 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.

[0023] 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 can be set from "0" to "N cIt may be set from any number to any number, such as "-1".

[0024] Each of the multiple phase shifters 51 imparts a different rotation amount. That is, in FIG. 2, a rotation amount ω2 different from the rotation amount ω1 is imparted to the multiple chirp signals transmitted from a transmitting antenna TX2 different from the transmitting antenna TX1. Similarly, for the transmitting antenna TXm, a rotation amount ω2 different from the rotation amounts ω1, ω2, etc. is imparted to the multiple chirp signals transmitted. 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.

[0025] In the following, the initial phase rotated by the rotation amount for 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 Figure 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. The DDM phase then 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."

[0026] 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.

[0027] 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 phases constituting a code are consistent within a rotation period Tr of the DDM phase and are randomly generated for each rotation period Tr by an integer multiple of the rotation amount. For example, the code adds a random half-rotation offset 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."

[0028] Also, the code is the chirp number N c The small code, which is a code of a code length obtained by dividing by the number of DDM phases Nph, is repeated for every bit, the number of DDM phases Nph. Here, the number of DDM phases Nph is the number of DDM phases in one rotation period Tr. For example, when the number of chirps N c If the number of CDM phases is 16 and the number of DDM phases Nph 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.

[0029] 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.

[0030] 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 amplifiers 52 amplify the transmission signals output from the phase shifters 51 and output the amplified signals to the corresponding transmitting antennas TX.

[0031] 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 thereof, 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.

[0032] As a result, as shown in Figure 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. In other words, the transmission of each transmission signal from each transmitting antenna TX starts substantially simultaneously.

[0033] The receiving antenna RX receives, as a received signal, a radio wave signal that includes a transmitted signal reflected from a target in the external world. Each of the multiple receiving antennas RX receives a signal that is a mixture of received signals corresponding to the transmitted signals from the multiple transmitting antennas TX. 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 that correspond to the transmitted signals from the multiple transmitting antennas TX and that are mixed in the mixed received signal will be referred to as received signal components.

[0034] 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.

[0035] 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 has the same number of amplifiers 61, signal mixing units 62, and AD converters 63 as the number of connected receiving antennas RX.

[0036] The amplifier 61 amplifies the received signal received by the receiving antenna RX and outputs it 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 that represents 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.

[0037] 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.

[0038] In the above-described transceiver unit 2, the transmit signals transmitted from each transmit antenna TX contain a phase offset as an error relative to the imparted phase change. The phase offset is caused by hardware in the transmit 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 transmit 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 transmit cycle Tt_c, a phase offset corresponding to the coded phase, which is the sum of the DDM phase and the CDM phase, is contained.

[0039] For example, in the measurement transmission cycle Tt_m, when the rotation amount is π / 2 as shown in Figure 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 each DDM phase of 0, π / 2, π, or 3π / 2 are denoted as δ0, δ 90 ,δ 180 ,δ 270In this case, as shown in Figure 5, a phase offset occurs periodically as a spurious signal with the same period as the rotation period Tr.

[0040] 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 and aging of the transmission circuit 5. Therefore, when compensating for the phase offset, it may be necessary to periodically estimate and update the actual phase offset.

[0041] 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 LAN (Local Area Network) line, a wire harness, an internal bus, and a wireless communication line. The configuration of the control unit 7 will be described later.

[0042] 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 made 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 signals to be transmitted and received by the antennas TX and RX. The case body 82, together with the radome 81, defines an accommodation space that accommodates the components of the radar device 1 described above.

[0043] 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 supervising ECU that comprehensively controls multiple radar devices 1 mounted on a moving object. The dedicated computer constituting the control unit 7 may be a sensor supervising ECU that comprehensively controls multiple sensors including the radar device 1 and other sensors such as LiDAR (Light Detection and Ranging / Laser Imaging Detection and Ranging).

[0044] 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 on or 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).

[0045] 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."

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 compensation reception cycle Tr_c.

[0050] 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."

[0051] 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 according to the code assigned to the transmission signal from the transmission antenna TXi.

[0052] In the decoding process, the receiver processing block 72 rearranges the distance spectra corresponding to each chirp signal into a phase rotation order that is common among 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 that is 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 [0, π / 2, π, 3π / 2], which is the phase rotation order of the encoded phases of the distance spectra in a rotation period Tr where the CDM phase is "0."

[0053] 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.

[0054] In the following 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 DDMwhere (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 the 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.

[0055] 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 DDM modulation is π / 2, the reception processing block 72 obtains the phase offsets δ0, δ 270 ,δ 180 ,δ 270 Get.

[0056] Then, in S109, the reception processing block 72 stores the estimated phase offsets of the transmitting antennas 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.

[0057] 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.

[0058] 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 in which the phases of each peak in an integrated spectrum obtained by integrating multiple Doppler spectra are aligned. 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.

[0059] 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 with a group of received signals obtained by the MIMO angle measurement process, in which transmission signals from multiple transmission antennas TX are received by each of multiple receiving antennas RX.

[0060] 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.

[0061] 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 in 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.

[0062] 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 "δ0, δ 270 ,δ 180 ,δ 270 Furthermore, for the fifth to eighth chirp signals, the fifth, sixth, and eighth have a CDM phase of "π", and the seventh has a CDM phase of "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 spectrum 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 decoded by inverting the phase after encoding, the phase offset assigned during transmission remains unchanged.

[0063] Therefore, in this comparative example, since there is no periodicity in the phase offset, 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 periodicity of the phase offset can be ensured as described above, it is possible to achieve both a reduction in processing time and estimation of the phase offset.

[0064] Furthermore, according to the first embodiment, a transmit signal is transmitted that is coded using a code defined by a sequence of CDM phases that randomly imparts a half-rotation phase shift for each DDM phase rotation period Tr, which makes it possible to code a transmit signal using a code that is easier to generate.

[0065] 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 for each 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.

[0066] (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.

[0067] 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 one of the 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 estimate and update the phase offset periodically by setting the compensation transmission cycle Tt_c for each of a 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 mounted is met.

[0068] 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 the processing of S106 to S108 for each distance spectrum group and acquire a phase offset that combines the processing results.

[0069] 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.

[0070] 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.

[0071] In a modified example, the radar device 1 may include only one receiving antenna RX. In this case, the receiving processing block 72 outputs sensing data correlated with the received signal received by the single receiving antenna RX.

[0072] 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 ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), an SOC (System on a Chip), a PGA (Programmable Gate Array), and a CPLD (Complex Programmable Logic Device). Such a digital circuit may also have a memory 7a that stores a program.

[0073] 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 traveling or remote traveling. Examples of the autonomous robot include an autonomous vehicle.

[0074] (Disclosure of technical ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be written in a multiple dependent form, with the subsequent clause referring to the preceding clause as an alternative. Furthermore, some clauses may be written in a multiple dependent form, referring to another multiple dependent clause. These multiple dependent clauses define multiple technical ideas.

[0075] (Technical thought 1) A radar system having a plurality of transmitting antennas (TX), at least one receiving antenna (RX), and a processor (7b), The processor: transmitting, from each of the transmitting antennas, a transmission signal including a plurality of chirp signals whose frequencies change over time, the transmission signal having a velocity phase that is a phase rotated for each of the chirp signals by a specific rotation amount, the rotation amount of which varies between the transmitting antennas; outputting sensing data correlating the transmission signals from the plurality of transmission antennas with reception signals received by the reception antennas in a measurement reception cycle corresponding to the measurement transmission cycle; configured to run The transmitting of the transmission signal includes: In a compensation transmission cycle before the measurement transmission cycle, the transmission signals are encoded with codes defined by a sequence of additional phases that add to each chirp signal 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 the codes are distinct for each transmission antenna, and are transmitted from each of the transmission antennas during overlapping transmission periods; The outputting of the sensing data includes: In a compensated reception cycle corresponding to the compensated transmission cycle, acquiring phase offset components correlated with a plurality of decoded signals obtained by rearranging a plurality of signal components correlated with the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, into a phase rotation order common between the rotation cycles; In the measurement receive cycle after the compensation receive cycle, outputting the sensing data correlated with the receive signal from which the phase offset component has been removed; A radar system including:

[0076] (Technical thought 2) The transmitting of the transmission signal includes: The radar system according to Technical Idea 1 includes transmitting the transmission signal encoded with the code defined by a sequence of the additional phases that randomly impart a phase shift amount of half a rotation to the velocity phase for each rotation period.

[0077] (Technical Thought 3) The transmitting of the transmission signal includes: A radar system according to Technical Idea 1 or Technical Idea 2, which 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.

[0078] (Technical Thought 4) The transmitting of the transmission signal includes: The radar system according to any one of Technical Ideas 1 to 3 includes transmitting the transmission signal in which the additional phases constituting small codes 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 are encoded with the codes that continue for each rotation period.

[0079] The above technical ideas 1 to 4 may be implemented in the form of a radar control device, a radar control method, and a radar control program. [Explanation of symbols]

[0080] 1: radar device (radar system), 7: control unit (radar control device), 7a: memory (storage medium), 7b: processor, TX: transmitting antenna, RX: receiving antenna

Claims

1. A radar system having a plurality of transmit antennas (TX), at least one receive antenna (RX), and a processor (7b), The processor: transmitting, from each of the transmitting antennas, a transmission signal including a plurality of chirp signals whose frequencies change over time, the transmission signal having a velocity phase that is a phase rotated for each of the chirp signals by a specific rotation amount, the rotation amount of which varies between the transmitting antennas; outputting sensing data correlating the transmission signals from the plurality of transmission antennas with reception signals received by the reception antennas in a measurement reception cycle corresponding to the measurement transmission cycle; configured to run The transmitting of the transmission signal includes: In a compensation transmission cycle before the measurement transmission cycle, the transmission signals are encoded with codes defined by a sequence of additional phases that add to each chirp signal 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 the codes are distinct for each transmission antenna, and are transmitted from each of the transmission antennas during overlapping transmission periods; The outputting of the sensing data includes: In a compensated reception cycle corresponding to the compensated transmission cycle, acquiring phase offset components correlated with a plurality of decoded signals obtained by rearranging a plurality of signal components correlated with the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, into a phase rotation order common between the rotation cycles; outputting the sensing data correlated with the received signal from which the phase offset component has been removed in the measurement receive cycle after the compensation receive cycle; A radar system including:

2. The transmitting of the transmission signal includes:

2. The radar system according to claim 1, further comprising 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 transmitting of the transmission signal includes:

2. The radar system according to claim 1, further comprising 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 transmitting of the transmission signal includes:

2. The radar system according to claim 1, further comprising 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 for controlling a radar system (1) having a plurality of transmitting antennas (TX) and at least one receiving antenna (RX), the radar control device comprising: The processor: transmitting, from each of the transmitting antennas, a transmission signal including a plurality of chirp signals whose frequencies change over time, the transmission signal having a velocity phase that is a phase rotated for each of the chirp signals by a specific rotation amount, the rotation amount of which varies between the transmitting antennas; outputting sensing data correlating the transmission signals from the plurality of transmission antennas with reception signals received by the reception antennas in a measurement reception cycle corresponding to the measurement transmission cycle; configured to run The transmitting of the transmission signal includes: In a compensation transmission cycle before the measurement transmission cycle, the transmission signals are encoded with codes defined by a sequence of additional phases that add to each chirp signal 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 the codes are distinct for each transmission antenna, and are transmitted from each of the transmission antennas during overlapping transmission periods; The outputting of the sensing data includes: In a compensated reception cycle corresponding to the compensated transmission cycle, acquiring phase offset components correlated with a plurality of decoded signals obtained by rearranging a plurality of signal components correlated with the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, into a phase rotation order common between the rotation cycles; outputting the sensing data correlated with the received signal from which the phase offset component has been removed in the measurement receive cycle after the compensation receive cycle; A radar control device comprising:

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, a transmission signal including a plurality of chirp signals whose frequencies change over time, the transmission signal having a velocity phase that is a phase rotated for each of the chirp signals by a specific rotation amount, the rotation amount of which varies between the transmitting antennas; outputting sensing data correlating the transmission signals from the plurality of transmission antennas with reception signals received by the reception antennas in a measurement reception cycle corresponding to the measurement transmission cycle; Including, The transmitting of the transmission signal includes: In a compensation transmission cycle before the measurement transmission cycle, the transmission signals are encoded with codes defined by a sequence of additional phases that add to each chirp signal 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 the codes are distinct for each transmission antenna, and are transmitted from each of the transmission antennas during overlapping transmission periods; The outputting of the sensing data includes: In a compensated reception cycle corresponding to the compensated transmission cycle, acquiring phase offset components correlated with a plurality of decoded signals obtained by rearranging a plurality of signal components correlated with the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, into a phase rotation order common between the rotation cycles; outputting the sensing data correlated with the received signal from which the phase offset component has been removed in the measurement receive cycle after the compensation receive cycle; A radar control method comprising:

7. A radar control program stored in a storage medium (7a) and including instructions to be 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), The instruction: transmitting, from each of the transmitting antennas, a transmission signal including a plurality of chirp signals whose frequencies change over time, the transmission signal having a velocity phase that is a phase rotated for each of the chirp signals by a specific rotation amount, the rotation amount of which varies between the transmitting antennas; outputting sensing data correlating the transmission signals from the plurality of transmission antennas with reception signals received by the reception antennas in a measurement reception cycle corresponding to the measurement transmission cycle; Including, The transmitting of the transmission signal includes: In a compensation transmission cycle before the measurement transmission cycle, the transmission signals are encoded with codes defined by a sequence of additional phases that add to each chirp signal 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 the codes are distinct for each transmission antenna, and are transmitted from each of the transmission antennas during overlapping transmission periods; The outputting of the sensing data includes: In a compensated reception cycle corresponding to the compensated transmission cycle, acquiring phase offset components correlated with a plurality of decoded signals obtained by rearranging a plurality of signal components correlated with the received signal, the signal components corresponding to each of the chirp signals within the rotation cycle, into a phase rotation order common between the rotation cycles; In the measurement reception cycle after the compensation reception cycle, outputting the sensing data correlated with the reception signal from which the phase offset component has been removed; A radar control program including:

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