Radar system, radar control method, and radar control program

Abstract

A processor of this radar system is configured to perform transmission of signal sets in which: the center frequency of a chirp signal changes monotonically for each of the signal sets; and the time interval between the sets changes temporally and linearly. The transmission of the signal sets includes adjusting the center frequency so that a ratio change rate, which is a relative change rate of a temporal change rate relative to a frequency change rate in the center frequency, falls within an allowable change rate range in a specific time domain. The processor is configured to perform acquisition of a reception signal set which results from a transmission signal set reflected by an external target. The processor is configured to perform output of sensing data correlating with a corrected signal set obtained by correcting the reception signal set so as to reduce a non-linear component included in a phase component of the reception signal set.

Description

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

[0001] This application is based on Patent Application No. 2024-38422 filed in Japan on March 12, 2024, and the contents of the original application are incorporated by reference in their entirety.

[0002] This disclosure relates to radar technology.

[0003] Patent Literature 1 discloses a radar system that transmits multiple chirp signals with varying center frequencies and acquires the chirp signals reflected by a target as a received signal. In frequency analysis of a beat signal generated by mixing a transmitted signal with a received signal, if the center frequency of the chirp signal varies, a term that depends on the product of the center frequency of the chirp signal and the transmission time appears in the frequency of the beat signal. If this term is nonlinear with respect to the number of sequential chirp signals, the target peak will broaden. To linearize this term, the radar system adjusts the time interval of the chirp signal so that the magnitude of the relative change in the time interval is at least twice the magnitude of the relative change in the center frequency.

[0004] German Patent No. 102020210079

[0005] However, the technology of Patent Document 1 may require time adjustment with higher precision than can be achieved by the integrated circuit of the radar system. In this case, it may be necessary to adjust parameters other than the time interval of the chirp signal to achieve the required time interval. Therefore, the technology of Patent Document 1 may impose stricter constraints on parameters other than the time interval of the chirp signal in order to suppress peak broadening.

[0006] An object of the present disclosure is to provide a radar system that can suppress peak broadening and relax restrictions on chirp signals.Another object of the present disclosure is to provide a radar control method that can suppress peak broadening and relax restrictions on chirp signals.A further object of the present disclosure is to provide a radar control program that can suppress peak broadening and relax restrictions on chirp signals.

[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 processor that transmits a plurality of transmit signal sets per transmission cycle, each transmit signal set including at least one chirp signal whose frequency varies over time, wherein the processor is configured to: transmit the transmit signal sets, each transmit signal set having a center frequency that varies monotonically for each transmit signal set and a time interval between the transmit signal sets that varies linearly over time, and wherein the center frequency is adjusted so that, where the relative rate of change of the center frequency of each transmit signal set with respect to a reference frequency is defined as the frequency change rate and the relative rate of change of the time interval of each transmit signal set with respect to the reference interval is defined as the time change rate, the ratio change rate, which is the relative rate of change of the time change rate to the frequency change rate, falls within an allowable change rate range in a specific time range; acquire a receive signal set in which the transmit signal set is reflected by a target in the external world; and output sensing data that correlates to a corrected signal set in which the receive signal set is corrected to reduce the nonlinear component of the linear and nonlinear components contained in the phase components of the receive signal set.

[0009] A second aspect of the present disclosure is a radar control method executed by a processor to control a radar device that transmits a plurality of transmit signal sets per transmission cycle, each transmit signal set including at least one chirp signal whose frequency varies over time, the method comprising: transmitting the transmit signal sets, each transmit signal set having a center frequency that varies monotonically for each transmit signal set and a time interval between the transmit signal sets that varies linearly over time, the center frequency of the transmit signal set being adjusted so that, where the relative rate of change of the center frequency of each transmit signal set with respect to a reference frequency is defined as the frequency change rate and the relative rate of change of the time interval of each transmit signal set with respect to the reference interval is defined as the time change rate, a ratio change rate, which is the relative rate of change of the time change rate to the frequency change rate, falls within an allowable change rate range in a specific time domain; acquiring a receive signal set in which the transmit signal set is reflected by a target in the external world; and outputting sensing data that correlates to a corrected signal set in which the receive signal set is corrected to reduce the nonlinear component of the linear and nonlinear components contained in the phase components of the receive signal set.

[0010] A third aspect of the present disclosure is a radar control program stored in a storage medium for controlling a radar device that transmits a plurality of transmission signal sets per transmission cycle, each transmission signal set including at least one chirp signal whose frequency varies over time, and includes instructions to be executed by a processor, the instructions including: transmitting transmission signal sets in which the center frequency of the chirp signal varies monotonically for each transmission signal set and the time interval between the transmission signal sets varies linearly over time, and in which the center frequency is adjusted so that, where the relative rate of change of the center frequency of each transmission signal set with respect to a reference frequency is defined as the frequency change rate and the relative rate of change of the time interval of each transmission signal set with respect to the reference interval is defined as the time change rate, a ratio change rate, which is the relative rate of change of the time change rate to the frequency change rate, falls within an allowable change rate range in a specific time range; acquiring a reception signal set in which the transmission signal set is reflected by a target in the external world; and outputting sensing data correlated to a corrected signal set in which the reception signal set is corrected to reduce the nonlinear component of the linear and nonlinear components contained in the phase components of the reception signal set.

[0011] According to these first to third aspects, the center frequency of the chirp signal is adjusted so that the ratio change rate falls within an acceptable range of change over a specific time period. This prevents the product of the time interval and center frequency of the chirp signal from becoming nonlinear over a specific time period. Because the center frequency can be adjusted more precisely than the time interval, adjusting the center frequency makes it easier for the ratio change rate to fall within an acceptable range of change, thereby relaxing constraints on parameters other than the center frequency. This reduces peak broadening depending on velocity. Furthermore, because the correction signal set corrects the phase components of the received signal set to reduce nonlinear components, it reduces peak broadening depending on distance. As a result, it is possible to suppress peak broadening and relax constraints on the chirp signal.

[0012] FIG. 1 is a schematic diagram showing the overall configuration of a radar device to which a first embodiment is applied. FIG. 2 is a block diagram showing the functional configuration of a control unit according to the first embodiment. FIG. 3 is a flowchart showing a radar control flow according to the first embodiment. FIG. 4 is a graph showing an example of a chirp signal according to the first embodiment. FIG. 5 is a graph showing an example of a change in time interval for each chirp signal. FIG. 6 is a graph showing an example of a change in center frequency for each chirp signal. FIG. 7 is a graph showing an example of a ratio change rate for each chirp signal. FIG. 8 is a graph for explaining linear components and non-linear components of a chirp signal. FIG. 9 is a flowchart showing a radar control flow according to a second embodiment. FIG. 10 is a flowchart showing a radar control flow according to a third embodiment. FIG. 11 is a graph showing an example of a chirp signal according to a fourth embodiment. FIG. 12 is a graph showing an example of a chirp signal according to a fifth embodiment. FIG. 13 is a graph showing an example of a chirp signal according to a sixth embodiment. FIG. 14 is a graph showing an example of a chirp signal according to a seventh embodiment. FIG. 15 is a schematic diagram showing a radar system according to a modified example.

[0013] Hereinafter, multiple embodiments of the present disclosure will be described with reference to the drawings. Note that corresponding components in each embodiment are designated by the same reference numerals, and redundant description may be omitted. Furthermore, when only a portion of the configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the remaining portions of the configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

[0014] 1 to 8, a first embodiment of the present disclosure will be described. A radar device 1 is mounted on a moving body such as a vehicle. The radar device 1 transmits a transmission signal, receives the transmission signal reflected by an object as a received signal, and detects, as target information, the distance to a target that is the object that reflected the transmission signal, the relative speed to the target, the direction of the target, and the like.

[0015] The target information 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. The in-vehicle ECU executes various processes for automatic driving of the vehicle and advanced driving assistance based on the acquired target information of each target.

[0016] Processing based on target information includes, for example, collision avoidance processing, warning processing, etc. Collision avoidance processing is processing for controlling the vehicle to avoid collision with a target by controlling the brake system, steering system, etc. based on the target information of each target. Warning processing is processing for warning the driver of the possibility of collision with a target based on the target information of each target.

[0017] 1 , the radar device 1 of this embodiment includes a clock oscillator 2a, a signal generating unit 2b, a plurality of transmitting circuits 3, a plurality of transmitting antennas TX, a plurality of receiving antennas RX, a plurality of receiving circuits 4, a control unit 6, and a storage unit 7. The radar device 1 is a so-called MIMO (Multiple-Input-Multiple-Output) radar that transmits transmission signals from a plurality of transmitting antennas TX to artificially increase the number of receiving antennas RX beyond the actual number.

[0018] The clock oscillator 2a generates a periodic clock signal. The clock oscillator 2a transmits the clock signal to the signal generating unit 2b and each receiving circuit 4. The signal generating unit 2b generates a modulated signal modulated at a modulation period corresponding to the clock signal based on a control signal from the control unit 6. The modulated signal is, for example, a so-called chirp signal whose frequency changes over time. The modulated signal is distributed and output to each channel of the transmitting circuit 3 and the receiving circuit 4. In the following, the modulated signal output from the signal generating unit 2b to the transmitting circuit 3 is referred to as a transmission signal. Furthermore, the modulated signal output from the signal generating unit 2b to the receiving circuit 4 is referred to as a local signal.

[0019] The transmission circuit 3 and the reception circuit 4 are each mainly composed of a semiconductor integrated circuit device such as an MMIC (Monolithic Microwave Integrated Circuit). The transmission circuit 3 is connected to a transmission antenna TX and outputs a transmission signal to the transmission antenna TX. For example, a plurality of transmission circuits 3 are mounted on one radar device 1. The transmission circuit 3 includes amplifiers 30 in the same number as the connected transmission antennas TX. The amplifiers 30 amplify the transmission signals output from the signal generation unit 2b and output the signals to the corresponding transmission antennas TX.

[0020] The transmitting antenna TX converts an electrical signal, which is a transmission signal provided from the signal generating unit 2b, into a radio wave signal and transmits it to the outside world. The transmitting antenna TX is configured to include 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 surface opposite to the ground plane of a dielectric substrate having a ground plane provided on one surface, so as to face the ground plane. The multiple antenna elements are connected, for example, in series, by a feeder line that supplies the electrical signal.

[0021] The receiving antenna RX receives, as a received signal, a radio wave signal including a transmission signal reflected by a target in the external world as a reflecting object. The receiving antenna RX is connected to a corresponding receiving circuit 4.

[0022] 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 4. The receiving antenna RX is, for example, a patch antenna in the same manner as the transmitting antenna TX, in which at least one antenna element is connected in series by a feeder line.

[0023] The receiving circuit 4 is connected to the receiving antenna RX and acquires the received signal received by the receiving antenna RX. For example, a plurality of receiving circuits 4 are mounted in one radar device 1. The receiving circuit 4 includes the same number of amplifiers 40, signal mixers 41, and AD converters 42 as the number of connected receiving antennas RX.

[0024] The amplifier 40 amplifies the received signal received by the receiving antenna RX and outputs the amplified signal to the signal mixer 41. The signal mixer 41 generates a beat signal by mixing the local signal from the signal generating unit 2b with the received signal. The generated beat signal is an interference signal that represents the frequency difference between the received signal and the local signal. The beat signal is output to the AD converter 42 after high-frequency components that deviate from the frequency difference between the received signal and the local signal have been filtered out by a low-pass filter (not shown).

[0025] The AD converter 42 converts the beat signal, which is a filtered analog signal, into a digital signal. The AD converter 42 acquires the clock signal output from the clock oscillator 2 a, samples the beat signal at time intervals corresponding to the cycle of the clock signal, and digitizes it. The AD converter 42 sequentially outputs the digitized beat signal to the control unit 6.

[0026] The accommodation unit 7 is a housing that accommodates the transmitting antenna TX, the receiving antenna RX, the clock oscillator 2a, the signal generating unit 2b, the transmitting circuit 3, the receiving circuit 4, and the control unit 6. The accommodation unit 7 includes a radome 7a and a case body 7b. The radome 7a is mainly formed of a transparent material that transmits millimeter-wave radio waves. The radome 7a is attached to the case body 7b so as to cover the antennas TX and RX. The radome 7a protects the antennas TX and RX while allowing radio waves to pass through, enabling signal transmission and reception by the antennas TX and RX. The case body 7b, together with the radome 7a, defines an accommodation space that accommodates the components of the radar device 1. A temperature sensor that detects the internal temperature may be provided within the accommodation unit 7. The temperature sensor may include, for example, a thermistor and output temperature information corresponding to the resistance value of the thermistor. The temperature sensor may be configured to detect temperature information of each of the transmitting circuit 3 and the receiving circuit 4 and output the information to the control unit 6.

[0027] The control unit 6 is a control unit including at least one dedicated computer. The dedicated computer constituting the control unit 6 may be, for example, an ECU (Electronic Control Unit) specialized for controlling the radar device 1.

[0028] The dedicated computer constituting the control unit 6 has at least one memory 6a and one processor 6b. The memory 6a 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 sensor system is turned on or off, or may refer to temporary storage in which data is erased when the sensor system is turned off.

[0029] The processor 6b may include at least one of a central processing unit (CPU), a graphics processing unit (GPU), a reduced instruction set computer (RISC)-CPU, a data flow processor (DFP), and a graph streaming processor (GSP) as a core. Alternatively, the processor 6b may be at least one of a digital circuit and an analog circuit. Here, the digital circuit refers to 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 include a memory 6a that stores a program.

[0030] In the radar device 1, the processor 6b executes a plurality of instructions included in a radar control program stored in the memory 6a to detect targets. This causes the radar device 1 to implement a plurality of functional units for controlling the radar. The functional units implemented in the radar device 1 include a transmission processing unit 60 and a reception processing unit 61, as shown in FIG. 2. These functional units may also be referred to as functional blocks.

[0031] The radar control method in which the control unit 6 controls the radar device 1 through cooperation of the transmission processing unit 60 and the reception processing unit 61 is executed in accordance with the radar control flow shown in Fig. 3. 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.

[0032] First, in S10, the transmission processing unit 60 generates and transmits a transmission signal. The transmission signal is a radar wave in the millimeter wave band or quasi-millimeter wave band. The transmission processing unit 60 generates a chirp wave, whose frequency is modulated over time, as a basic signal. Specifically, as shown in FIG. 4 , the transmission processing unit 60 defines a waveform that changes (e.g., gradually increases) from a predetermined initial frequency to a final frequency as one chirp, and generates a signal that repeats multiple chirps at a predetermined cycle. The transmission processing unit 60 transmits the multiple chirp signals thus generated as transmission signals. Note that, hereinafter, the number indicating the ordinal number of a specific chirp signal in one transmission cycle may be referred to as chirp number k.

[0033] The transmission processing unit 60 generates multiple chirp signals in one transmission cycle. The transmission processing unit 60 sets the center frequency of the chirp signals so that it changes monotonically in one transmission cycle. In the example shown in FIG. 4, the transmission processing unit 60 sets the center frequency of each chirp signal so that the center frequency increases monotonically with the passage of time in the transmission cycle. Note that the transmission cycle here refers to a specific number of transmissions (k ｆｉｎ The cycle is the time it takes to complete the transmission of the chirp signals (number of chirp signals).

[0034] The transmission processing unit 60 sets the time interval of the chirp signals to change linearly with time and the number of chirp signal sequences. Here, the time interval of a particular chirp signal is the interval between the transmission start time of that signal and the transmission start time of the chirp signal immediately preceding that signal within the transmission cycle. Here, for the kth chirp signal in a certain transmission cycle, the transmission start time is set to T Ｓ (k), the time interval is T Ｄ Since there is no preceding chirp signal for the first chirp signal, the time interval from the reference time is set as T ＤＳ Let's say. T ＤＳ is set to zero, for example. Ｄ If the increase width for each chirp signal in (k) is Δt, the linearly changing time interval T Ｄ (k) is T ＤＳ , k, and Δt, the following equation (1) is used.

[0035] Then, the transmission processing unit 60 calculates the transmission start time T for the k-th chirp signal, which corresponds to the following equation (2): Ｓ (k) is set.

[0036] The transmission processing unit 60 calculates the time interval T corresponding to the above formula for each of the specified number of chirp signals in one transmission cycle. Ｄ (k) and transmission start time T Ｓ Furthermore, the transmission processing unit 60 defines a monotonically changing center frequency as a parameter that defines each chirp signal in one transmission cycle.

[0037] The transmission processing unit 60 calculates the center frequency F of the kth chirp signal. Ｓ (k), the time interval T Ｄ (k) is set to a frequency such that the product of (k) is substantially linear with respect to time and the number of orders of the chirp signal in a specific time domain. ＤThis means that the relative change rate of the time change rate, which is the relative change rate with respect to the reference interval (k), to the frequency change rate, which is the relative change rate of the center frequency with respect to the reference frequency, falls within the allowable change rate range. Hereinafter, the relative change rate of the time change rate with respect to the frequency change rate may be referred to as the ratio change rate. Note that the allowable change rate range is a range in which the ratio change rate is equal to or less than a specified upper threshold and equal to or greater than a specified lower threshold. Furthermore, the specific time range is a time range in which the ratio change rate is equal to or less than a specified upper limit time and equal to or greater than a specified lower limit time. For example, the specific time range is a time range after a predetermined time has elapsed from the start of the transmission cycle, i.e., a time range in which the upper limit time is the specified time and the lower limit time is zero.

[0038] Here, the time change rate A and frequency change rate B of the k-th chirp signal correspond to the values ​​calculated by the following formulas (3) and (4). Note that the reference interval for the time change rate A is the first time interval T ＤＳ The reference frequency at the frequency change rate B is the first center frequency F ＳＳ Let's say.

[0039] Therefore, the ratio change rate corresponds to the value obtained by dividing the right side of the formula (3) by the right side of the formula (4). The transmission processing unit 60 determines the center frequency F at which the ratio change rate falls within the allowable change rate range in a specific time region. Ｓ (k). For example, the time interval T Ｄ 5. In this case, the transmission processing unit 60 changes the center frequency F Ｓ (k) is varied for each chirp signal in accordance with the variation shown in the graph of FIG. 6 so that the ratio change rate becomes the variation shown in the graph of FIG. 7. Ｓ (k) is the time interval T Ｄ (k) and the transmission start time T Ｓ The value at which the product with (k) is substantially linear corresponds to the parameter expressed by the following equation (5).

[0040] Here, the rate of change from the trailing chirp signal to the leading chirp signal in each transmission cycle varies only in the negative direction. That is, the graph of the rate of change in one transmission cycle is a one-sided hyperbolic curve of inverse proportion, as shown in Figure 7. For this reason, the transmission processing unit 60 manages the chirp numbers for each chirp signal in one transmission cycle, starting from k = 1.

[0041] The IC constituting the control unit 6 is generally capable of adjusting the time interval in units of approximately 10 ns. The IC is also generally capable of adjusting the center frequency in units of comma hertz.

[0042] In the first embodiment, the transmission processing unit 60 generates a transmission signal in which the time interval for each chirp signal varies linearly with time and the number of chirp signal sequences, and the center frequency varies monotonically. In other words, the transmission processing unit 60 can be understood as generating a transmission signal in which the time interval for each signal set varies linearly and the center frequency varies monotonically, using a single chirp signal as a signal set. A single chirp signal is an example of a "transmission signal set." The time width from the start to the end of chirp signal transmission within a transmission cycle and the size of the bandwidth are set to be substantially the same, for example. Furthermore, the transmission end time of the preceding chirp signal and the transmission start time of the following chirp signal are set to be substantially the same.

[0043] Next, in S20, the transmission processing unit 60 transmits the set chirp signal. In the following S30, the reception processing unit 61 acquires, from the reception circuit 4, a beat signal corresponding to the received signal that is the transmitted chirp signal reflected by the target.

[0044] Next, in S40, the reception processing unit 61 performs a fast Fourier transform (FFT) process on the beat signal. Specifically, the transmission processing unit 60 first performs FFT processing on the beat signal for each chirp. This first FFT process obtains, for each chirp, frequency spectrum (distance spectrum) data that shows peaks at frequency positions corresponding to the distance to the target. The distance spectrum data is a distance bin signal that includes information on the signal strength for each distance bin according to the distance resolution.

[0045] Then, in S50, the reception processing unit 61 applies a phase correction component to the distance spectrum. Here, the phase correction component is a phase component that is applied to the beat signal in order to reduce the nonlinear component, out of the linear component and nonlinear component contained in the phase component of the acquired beat signal, compared to when the beat signal was acquired.

[0046] More specifically, the phase correction component is a phase component that correlates with the difference between the center frequency of the chirp signal and a linear component assumed in the phase component of the beat signal corresponding to the chirp signal. In this embodiment, the beat signal corresponding to one chirp signal is an example of a "received signal set."

[0047] Here, the phase φ of the beat signal at a particular range bin ＩＦ The relationship shown in the following formula (6) holds between (k) and the chirp number k of the corresponding chirp signal. In formula (6), r is the distance, v is the velocity, and c is the speed of light. ｃｈ is a parameter determined according to the slope of the chirp signal, and is +1 if the slope is positive and −1 if the slope is negative.

[0048] Also, the center frequency of the chirp signal F Ｓ As shown in Figure 8, (k) can be defined as the sum of a linear component that changes linearly with the average fluctuation amount ΔF and a nonlinear component that changes nonlinearly. In other words, if the nonlinear component is defined as a parameter e(k) that correlates with k, then the center frequency F Ｓ The relationship shown in the following equation (7) holds between (k) and the chirp number k.

[0049] Here, the center frequency F of the first term on the right side of the formula (6) Ｓ Substituting the right side of equation (7) into (k), the center frequency F Ｓ When the right side of the formula (5) is substituted for (k), the formula (6) is transformed into the following formula (8).

[0050] Furthermore, rearranging equation (8), the phase φ ＩＦ The relationship between (k) and chirp number k is expressed by the following equation (9).

[0051] The second term in the curly brackets in Equation (9) is a term that changes linearly with respect to k. On the other hand, the first term is a term that changes nonlinearly with respect to k. That is, the phase correction component φ ｃｏｍｐ (k) can be defined by the following equation (10), which cancels out the component of the first term.

[0052] Here, from equation (7), e(k) is the center frequency F Ｓ (k) and the average fluctuation amount ΔF multiplied by the chirp number k. That is, the phase correction component φ ｃｏｍｐ (k) is a parameter correlated with this difference. Ｓ (k), the average fluctuation amount ΔF, and the chirp number k, the phase correction component φ ｃｏｍｐ The reception processing unit 61 can obtain the center frequency F (k) of the first chirp signal and the last chirp signal. Ｓ Alternatively, the reception processing unit 61 may use a parameter obtained by dividing the difference between the first and last chirp signals by one, as the average fluctuation amount ΔF. Ｓ The differential value of the change in (k) may be used as the average fluctuation amount ΔF.

[0053] The reception processing unit 61 calculates the phase correction component φ ｃｏｍｐThe reception processing unit 61 applies the phase correction component φ (k) to the range bin signal, for example, over all the acquired range bins. ｃｏｍｐ As a result, the reception processing unit 61 obtains corrected range bin signals, which are range bin signals in which the nonlinear phase components have been reduced. The corrected range bin signals corresponding to the chirp signals are an example of a "correction signal set."

[0054] Next, in S60, the reception processing unit 61 applies a window function to all the distance bins of the corrected distance bin signal. The window function is, for example, a Hanning function or a Gaussian function.

[0055] Then, in S70, the reception processing unit 61 performs a second FFT process on the corrected range bin signal that has been windowed. If the relative velocity with respect to the target is not zero, the range spectrum corresponding to each chirp will show a peak in the same range bin. However, the phases of the chirps differ from one another. This phase difference between the chirps is due to changes in the distance between the radar device 1 and the target. Using this, the FCM (Fast Chirp Modulation) method detects the relative velocity with respect to the target. Through this second FFT process, the reception processing unit 61 acquires two-dimensional spectrum signals for the range and relative velocity.

[0056] Specifically, in the second FFT process, the receiver processor 61 performs FFT on a waveform in which the phases at the range bins obtained in the first FFT process for multiple chirps are arranged in time series. This results in a frequency spectrum (velocity spectrum) for each velocity bin, which shows peaks at positions corresponding to the relative velocity with respect to the target. Note that depending on the maximum detectable velocity, velocity aliasing may occur, resulting in multiple peaks in the two-dimensional spectrum signal.

[0057] Here, the central frequency F Ｓ (k) and the time interval T Ｄ The product with (k) is substantially linear. Ｓ (k) is the time interval T to the kth chirp signal Ｄ (k), the transmission start time TＳ (k) and the center frequency F Ｓ The product with (k) is also linear. That is, the center frequency F Ｓ (k) and the transmission start time T Ｓ (k) and F Ｓ The product with (k) is also linear. Therefore, the reception processing unit 61 acquires a two-dimensional spectrum signal in which the broadening of the peaks is suppressed even when the target velocity increases, compared to when this product is nonlinear.

[0058] Furthermore, the phase correction component φ ｃｏｍｐ By applying (k) to the range bin signal, the phase at each range bin is essentially equivalent to the phase obtained by substantially removing the first term on the right-hand side, which is a nonlinear term, from Equation (9), which is obtained by rearranging Equation (6). Therefore, the reception processing unit 61 acquires a two-dimensional spectrum signal in which the broadening of the peaks is suppressed even when the target distance is long, compared to when the nonlinear term is not removed.

[0059] Then, in S80, the reception processing unit 61 outputs target information correlated with the two-dimensional spectrum signal acquired as a result of the second FFT process. The target information includes at least one of the following: the distance to the target, the relative speed of the target, and the relative angle. For example, the reception processing unit 61 acquires and outputs the distance and relative speed of the target from the peak of the two-dimensional spectrum signal. The reception processing unit 61 also acquires and outputs the relative angle from a frequency spectrum (angular spectrum) that shows a peak at a position corresponding to the relative angle of the target, which is acquired by further performing FFT processing on each two-dimensional spectrum signal for each receiving antenna RX. The reception processing unit 61 outputs the target information to another on-board ECU and to the outside of the vehicle. The target information is an example of "sensing data." In the first embodiment described above, the radar device 1 is an example of a "radar system."

[0060] According to the first embodiment described above, the center frequency F of the chirp signal is adjusted so that the ratio change rate falls within the allowable change rate range in a specific time domain. Ｓ (k) is adjusted. Therefore, the time interval TＤ (k) and the center frequency F Ｓ (k) is nonlinear within a specific time range. Ｓ (k) is the time interval T Ｄ Since finer adjustment is possible compared to (k), the center frequency F Ｓ By adjusting (k), the ratio change rate tends to fall within the allowable change rate range, and the center frequency F Ｓ Constraints on parameters other than (k) can be relaxed. This can suppress peak broadening depending on velocity. Furthermore, since the correction signal set corrects to reduce nonlinear components in the phase components of the received signal set, peak broadening depending on distance can be suppressed. As a result, it may be possible to suppress peak broadening and relax constraints on the chirp signal.

[0061] Furthermore, according to the first embodiment, a phase correction component correlated to the center frequency of the chirp signal and the average fluctuation amount of the center frequency for each chirp signal in a transmission cycle is applied to the set of received signals. Sensing data correlated to the acquired set of correction signals is output. Therefore, nonlinear components of the beat signal correlated to the center frequency and the average fluctuation amount can be reliably suppressed. Furthermore, according to the first embodiment, sensing data correlated to the set of correction signals obtained by applying the phase correction component to the beat signal before applying the window function can be output. Therefore, the independence of the application of the phase correction component from the application of the window function can be ensured.

[0062] Second Embodiment As shown in FIG. 9, the second embodiment is a modification of the first embodiment.

[0063] The radar control method of the second embodiment is executed according to the radar control flow shown in Fig. 9. The radar control flow of the second embodiment proceeds to S45 after S40. In S45, the reception processing unit 61 calculates the phase correction component φ ｃｏｍｐ A window function including (k) is applied to the range bin signal. ｃｏｍｐ The window function including (k) is, for example, a phase correction component φ ｃｏｍｐ It is defined by a function multiplied by (k).

[0064] According to the second embodiment described above, the phase correction component φ is used as part of the window function. ｃｏｍｐ (k) is applied. Therefore, the window function and the phase correction component φ ｃｏｍｐ The operations in (k) are performed together, so that the calculation process can be simplified.

[0065] Third Embodiment As shown in FIG. 10, the third embodiment is a modification of the first embodiment.

[0066] The radar control method of the third embodiment is executed according to the radar control flow shown in Fig. 10. The radar control flow of the third embodiment proceeds to S55 after S40. In S55, the reception processing unit 61 calculates a phase correction component φ ｃｏｍｐ In other words, the reception processing unit 61 applies the phase correction component φ ｃｏｍｐ The distance bins on which (k) is applied are limited to a distance range of interest. Here, the distance range of interest may be, for example, a distance range equal to or greater than a threshold distance. Alternatively, the distance range of interest may be a distance range in which the presence of a target peak is estimated.

[0067] According to the third embodiment described above, the phase correction component φ is applied to the signal portion corresponding to the distance range of interest. ｃｏｍｐ (k) is applied. Therefore, the phase correction component φ ｃｏｍｐ The distance bins over which (k) is operated may be limited, reducing the computational load.

[0068] Fourth Embodiment As shown in FIG. 11, the fourth embodiment is a modification of the first embodiment.

[0069] In the fourth embodiment, the transmission processing unit 60 switches between increasing and decreasing the frequency of each chirp signal over time depending on the transmission cycle. In other words, the transmission processing unit 60 changes the positive and negative slopes of the frequency change over time for each chirp signal depending on the transmission cycle. For example, as shown in FIG. 11 , the transmission processing unit 60 sets the slope of the frequency change to a positive direction in a specific transmission cycle, and switches the slope of the frequency change to a negative direction in the immediately following transmission cycle.

[0070] According to the fourth embodiment described above, the frequency of the chirp signal switches between increasing and decreasing over time in accordance with the transmission cycle, so that interference with other radar devices 1 can be suppressed.

[0071] Fifth Embodiment As shown in FIG. 12, the fifth embodiment is a modification of the first embodiment.

[0072] In the fifth embodiment, the transmission processing unit 60 switches between increasing and decreasing the center frequency of each chirp signal over time depending on the transmission cycle. In other words, the transmission processing unit 60 changes the positive and negative slope of the center frequency change over time in one transmission cycle. For example, as shown in FIG. 12 , the transmission processing unit 60 sets the slope of the center frequency change to a positive direction in a specific transmission cycle, and then switches the slope of the center frequency change to a negative direction in the immediately following transmission cycle.

[0073] According to the fifth embodiment described above, the center frequency of each chirp signal switches between increasing and decreasing over time depending on the transmission cycle, so that interference with other radar devices 1 can be suppressed.

[0074] Sixth Embodiment As shown in FIG. 13, the sixth embodiment is a modification of the first embodiment.

[0075] The transmission processing unit 60 performs both a switching between increasing and decreasing the frequency of each chirp signal over time in accordance with the transmission cycle, and a switching between increasing and decreasing the center frequency of each chirp signal over time in accordance with the transmission cycle. For example, as shown in Figure 13, the transmission processing unit 60 sets the slope of the frequency change for each chirp signal to a positive direction and the slope of the center frequency change to a negative direction in a specific transmission cycle. Then, in the immediately following transmission cycle, the transmission processing unit 60 switches the slope of the frequency change for each chirp signal to a negative direction and the slope of the center frequency change to a positive direction.

[0076] Seventh Embodiment As shown in FIG. 14, the seventh embodiment is a modification of the first embodiment.

[0077] In the seventh embodiment, the transmission processing unit 60 sets the time interval and center frequency of the chirp signals within a transmission cycle so that they change for each set of multiple chirp signals (transmission signal set). In the example shown in Fig. 11, the transmission processing unit 60 sets the time interval and center frequency so that they change for each set of two consecutive chirp signals. In this embodiment, the beat signal corresponding to one chirp signal set is an example of a "reception signal set."

[0078] According to the seventh embodiment described above, the center frequency and time interval are changed for each set of multiple chirp signals, rather than for each chirp signal. This allows for smaller time interval adjustments compared to when changing the time interval for each chirp signal. For example, if the minimum time interval that can be set by the control unit 6 is 10 ns, adjustments of 5 ns can be achieved by changing the time interval once every two times. If there is a difference between the required time interval and the implementable time interval, changing the time interval for each set of multiple chirp signals as described above allows for finer time interval control.

[0079] (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.

[0080] In a modified example, the reception processing unit 61 may output, as sensing data, a two-dimensional spectrum signal obtained by performing FFT processing on the corrected distance bin signal.

[0081] In a modified example, at least some of the functions of the reception processing unit 61 may be implemented by a control device other than the control unit 6, that is, outside the radar device 1. For example, as shown in FIG. 15 , another on-board ECU 10 in a vehicle equipped with the radar device 1 may be configured to execute some of the functions of the reception processing unit 61. For example, the processor 10b of the on-board ECU 10 may execute a program stored in the memory 10a to execute the processing from S50 onwards in FIG. 3. In this case, the control unit 6 executes the processing up to S40 and outputs a distance bin signal to the on-board ECU 10. In the modified example of FIG. 15 , an on-board system 100 including the radar device 1 and the on-board ECU 10 is an example of a "radar system."

[0082] In a modified example, the process of applying the phase correction component may be executed after the process of applying the window function, i.e., the process of S60 may be executed prior to the process of S50 in FIG.

[0083] In a variant, the time interval T Ｄ (k) may be an interval between representative times in the chirp signal other than the transmission start time. The representative time other than the transmission start time may be, for example, the transmission end time of the chirp signal, or the time when the frequency is the center frequency F Ｓ (k) and so on.

[0084] In a modified example, the direction of change in the ratio from the trailing chirp signal side to the leading chirp signal side in each transmission cycle may be only one direction, the positive direction.

[0085] In a variant, the time interval T of the chirp signal Ｄ (k) and the center frequency F Ｓ Parameters other than (k) may be changed as appropriate. Furthermore, the preceding chirp signal and the following chirp signal may be separated in time, or may partially overlap in time.

[0086] In a modified example, the radar device 1 may perform so-called CDM (Code Division Multiplex) modulation, in which a random component is superimposed on the phase of a chirp signal to be transmitted from each of the plurality of transmitting antennas TX.

[0087] In a modified example, the radar device 1 may perform so-called DDM (Doppler Division Multiplex) modulation, in which a linear component is superimposed on the phase of a chirp signal to be transmitted from each of the plurality of transmitting antennas TX.

[0088] 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. Furthermore, the autonomous robot may include an autonomous vehicle.

[0089] In addition to the embodiments described above, the above-described embodiments and modifications may be implemented as a control device that can be mounted on a host vehicle and has at least one processor 6 b and one memory 6 a. Specifically, the above-described embodiments and modifications may be implemented in the form of a processing circuit (e.g., a processing ECU) or a semiconductor device (e.g., a semiconductor chip).

[0090] (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.

[0091] (Technical Idea 1) A radar system having a processor (6b) that transmits a plurality of transmit signal sets per transmission cycle, each set including at least one chirp signal whose frequency varies over time, wherein the processor is configured to: transmit the transmit signal sets, in which the center frequency of the chirp signal varies monotonically for each transmit signal set and the time interval between the transmit signal sets varies linearly over time, and the center frequency is adjusted so that, where a frequency change rate is a relative change rate of the center frequency for each transmit signal set with respect to a reference frequency and a time change rate is a relative change rate of the time interval for each transmit signal set with respect to a reference interval, the ratio change rate, which is the relative change rate of the time change rate to the frequency change rate, falls within an allowable change rate range in a specific time range; acquire a receive signal set in which the transmit signal set is reflected by a target in the external world; and output sensing data that correlates to a corrected signal set in which the receive signal set is corrected to reduce nonlinear components out of linear components and nonlinear components included in phase components of the receive signal set.

[0092] (Technical Idea 2) A radar system according to Technical Idea 1, wherein outputting the sensing data includes outputting the sensing data correlated to the correction signal set obtained by applying a phase correction component to the received signal set that is correlated to the center frequency of the chirp signal and the average fluctuation amount of the center frequency for each chirp signal in the transmission cycle.

[0093] (Technical Idea 3) A radar system according to Technical Idea 2, wherein outputting the sensing data includes outputting the sensing data correlated with the correction signal set obtained by applying the phase correction component before or after applying a window function to the received signal set.

[0094] (Technical Idea 4) A radar system according to Technical Idea 2, wherein outputting the sensing data includes outputting the sensing data correlated to the corrected signal set obtained by applying the phase correction component as part of a window function to the received signal set.

[0095] (Technical Idea 5) A radar system described in Technical Idea 2 or Technical Idea 3, in which outputting the sensing data includes outputting the sensing data correlated to the corrected signal set obtained by applying the phase correction component to a signal portion corresponding to a specific distance range of interest in the received signal set.

[0096] (Technical Idea 6) The radar system according to any one of Technical Ideas 1 to 5, wherein transmitting the set of transmission signals includes transmitting a single chirp signal for each of the set of transmission signals.

[0097] (Technical Idea 7) The radar system according to any one of Technical Ideas 1 to 5, wherein transmitting the set of transmission signals includes transmitting a plurality of the chirp signals for each of the set of transmission signals.

[0098] The above technical idea may be implemented in the form of a radar control method and a radar control program.

Claims

1. A radar system having a processor (6b) that transmits a plurality of transmit signal sets per transmission cycle, each set including at least one chirp signal whose frequency varies over time, wherein the processor is configured to: transmit the transmit signal sets, in which the center frequency of the chirp signal varies monotonically for each transmit signal set and the time interval between the transmit signal sets varies linearly over time, and the center frequency of each transmit signal set is adjusted so that, where the relative rate of change of the center frequency of each transmit signal set with respect to a reference frequency is defined as a frequency change rate and the relative rate of change of the time interval of each transmit signal set with respect to a reference interval is defined as a time change rate, a ratio change rate, which is the relative rate of change of the time change rate to the frequency change rate, falls within an allowable change rate range in a specific time range; acquire a receive signal set in which the transmit signal set is reflected by a target in the external world; and output sensing data that correlates with a corrected signal set in which the receive signal set is corrected to reduce nonlinear components out of linear and nonlinear components contained in the phase components of the receive signal set.

2. The radar system of claim 1, wherein outputting the sensing data includes outputting the sensing data correlated to the corrected signal set obtained by applying a phase correction component to the received signal set that is correlated to the center frequency of the chirp signal and an average amount of fluctuation in the center frequency for each chirp signal in the transmission cycle.

3. The radar system of claim 2, wherein outputting the sensing data includes outputting the sensing data correlated to the corrected signal set obtained by applying the phase correction component before or after applying a window function to the received signal set.

4. The radar system of claim 2, wherein outputting the sensing data includes outputting the sensing data correlated to the corrected signal set obtained by applying the phase correction component as part of a window function to the received signal set.

5. The radar system of claim 2, wherein outputting the sensing data includes outputting the sensing data correlated to the corrected signal set obtained by applying the phase correction component to a signal portion of the received signal set corresponding to a specific distance range of interest.

6. A radar system as claimed in any one of claims 1 to 5, wherein transmitting the set of transmit signals comprises transmitting a single chirp signal for each of the set of transmit signals.

7. A radar system according to any one of claims 1 to 5, wherein transmitting the set of transmit signals includes transmitting a plurality of the chirp signals for each of the set of transmit signals.

8. A radar control method executed by a processor (6b) for controlling a radar device (1) that transmits a plurality of transmission signal sets per transmission cycle, each transmission signal set including at least one chirp signal whose frequency varies over time, the method comprising: transmitting the transmission signal sets, in which the center frequency of the chirp signal varies monotonically for each transmission signal set and the time interval between the transmission signal sets varies linearly over time, the center frequency of the transmission signal sets being adjusted so that, where the relative rate of change of the center frequency of each transmission signal set with respect to a reference frequency is defined as a frequency change rate and the relative rate of change of the time interval of each transmission signal set with respect to a reference interval is defined as a time change rate, a ratio change rate, which is the relative rate of change of the time change rate to the frequency change rate, falls within an allowable change rate range in a specific time range; acquiring a reception signal set in which the transmission signal set is reflected by a target in the external world; and outputting sensing data correlated to a correction signal set in which the reception signal set is corrected to reduce nonlinear components out of linear components and nonlinear components contained in the phase components of the reception signal set.

9. A radar control program stored in a storage medium (6a) for controlling a radar device (1) that transmits a plurality of transmission signal sets per transmission cycle, each set including at least one chirp signal whose frequency varies over time, and including instructions to be executed by a processor (6b), the instructions including: transmitting the transmission signal sets in which the center frequency of the chirp signal varies monotonically for each transmission signal set and the time interval between the transmission signal sets varies linearly over time, the center frequency of each transmission signal set being adjusted so that, where the relative rate of change of the center frequency of each transmission signal set with respect to a reference frequency is defined as a frequency change rate and the relative rate of change of the time interval of each transmission signal set with respect to a reference interval is defined as a time change rate, a ratio change rate, which is the relative rate of change of the time change rate to the frequency change rate, falls within an allowable change rate range in a specific time range; and acquiring a reception signal set resulting from reflection of the transmission signal set by a target in the external world. and outputting sensing data correlated with a corrected signal set obtained by correcting the set of received signals so as to reduce nonlinear components among linear components and nonlinear components included in phase components of the set of received signals.

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