Radar device, radar control method, and radar control program

Abstract

This radar device has a processor and transmits, during each transmission cycle, a plurality of signal sets that each include at least one chirp signal of which the frequency changes over time. The processor is configured so as to transmit signal sets, the center frequency of the chirp signal in each of these signal sets changing monotonically, and the time intervals between these signal sets changing linearly over time. The transmission of signal sets includes adjusting, when the relative change rate with respect to the reference frequency of the center frequency for each signal set is defined as the frequency change rate and the relative change rate with respect to the reference interval of the time interval for each signal set is defined as the time change rate, the center frequency such that a ratio change rate, which is the relative change rate of the time change rate with respect to the frequency change rate, falls within a permittable change rate range during a specific time range.

Description

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

[0001] This application is based on Patent Application No. 2023-96455 filed in Japan on June 12, 2023, 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 device 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 still 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 device having a processor that transmits a plurality of signal sets per transmission cycle, each signal set including at least one chirp signal whose frequency varies over time, wherein the processor is configured to perform the following: transmitting signal sets in which the center frequency of the chirp signal varies monotonically for each signal set and the time interval between the signal sets varies linearly over time; and acquiring received data of reflected signals of the chirp signals reflected by targets in the external world, wherein the transmitting of the signal sets includes adjusting the center frequency so that, where the relative rate of change of the center frequency of each signal set with respect to a reference frequency is defined as the frequency rate of change and the relative rate of change of the time interval of each signal set with respect to the reference interval is defined as the time rate of change, a ratio rate of change, which is the relative rate of change of the time rate of change to the frequency rate of change, falls within an allowable rate of change range in a specific time domain.

[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 signal sets per transmission cycle, each signal set including at least one chirp signal whose frequency varies over time, the method including: transmitting signal sets in which the center frequency of the chirp signal varies monotonically for each signal set and the time interval between the signal sets varies linearly over time; and acquiring received data of reflected signals of the chirp signals reflected by a target in the external world, the transmitting of the signal sets including: adjusting the center frequency so that, where the relative rate of change of the center frequency of each signal set with respect to a reference frequency is defined as the frequency rate of change and the relative rate of change of the time interval of each signal set with respect to the reference interval is defined as the time rate of change, a ratio rate of change, which is the relative rate of change of the time rate of change to the frequency rate of change, falls within an allowable rate of change range in a specific time domain.

[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 signal sets per transmission cycle, each signal set including at least one chirp signal whose frequency varies over time, and including instructions to be executed by a processor, the instructions including: transmitting signal sets in which the center frequency of the chirp signal varies monotonically for each signal set and the time interval between the signal sets varies linearly over time; and acquiring received data of reflected signals of the chirp signals reflected by a target in the external world, the transmitting of the signal sets including: adjusting the center frequency so that, where the relative rate of change of the center frequency of each signal set with respect to a reference frequency is defined as the frequency rate of change and the relative rate of change of the time interval of each signal set with respect to the reference interval is defined as the time rate of change, a ratio rate of change, which is the relative rate of change of the time rate of change to the frequency rate of change, falls within an allowable rate of change range in a specific time domain.

[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 allowable range of change over a specific time period. Therefore, the product of the time interval and center frequency of the chirp signal can be prevented from becoming nonlinear over the 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 the allowable range of change, and this can alleviate constraints on parameters other than the center frequency. As a result, peak broadening can be suppressed and constraints on the chirp signal can be alleviated.

[0012] 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 showing an example of a chirp signal according to a second embodiment; FIG. 9 is a graph showing an example of a chirp signal according to a third embodiment; FIG. 10 is a graph showing an example of a chirp signal according to a fourth embodiment; and FIG.

[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 7 , a radar device 1 is mounted on a moving object 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 of 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 (registered trademark). 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. Each 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.

[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 calculated values ​​according to 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 number k of 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, each consisting of a single chirp signal, varies linearly with time and the center frequency varies monotonically. The time width from the start to the end of chirp signal transmission within a transmission cycle and 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 receives the signal that is the transmission signal reflected by the target and returned as a received signal. In the following S30, the reception processing unit 61 acquires a beat signal corresponding to the received signal.

[0044] Then, in S40, the reception processing unit 61 performs frequency analysis on the beat signal to acquire target information related to the target. The target information includes at least the distance and relative speed of the target relative to the radar device 1. Specifically, the reception processing unit 61 performs two FFT (Fast Fourier Transform) processes on the beat signal. As a result, the transmission processing unit 60 acquires a two-dimensional spectrum related to the distance and relative speed.

[0045] More specifically, the transmission processor 60 first performs FFT processing on the beat signal for each chirp. This first FFT processing obtains a frequency spectrum (distance spectrum) for each chirp, with peaks at frequency positions corresponding to the distance to the target. The distance spectrum is data indicating the signal strength for each distance bin according to the distance resolution.

[0046] When the relative velocity with respect to the target is not zero, the distance spectrum corresponding to each chirp shows a peak in the same distance bin, but the phases of the chirps are different from each other. This phase difference between the chirps is caused by 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. By performing these two FFT processes, the transmission processing unit 60 acquires two-dimensional spectra of the distance and relative velocity.

[0047] Specifically, in the second FFT process, the reception processing unit 61 performs FFT processing on a waveform in which the phases at the distance bins obtained in the first FFT process for multiple chirps are arranged in time series. This results in a frequency spectrum (velocity spectrum) showing peaks at positions corresponding to the relative velocity from the target for each velocity bin. Note that depending on the maximum detectable velocity, velocity aliasing may occur, resulting in multiple peaks in the two-dimensional spectrum.

[0048] Here, the frequency φ at a specific sampling point for each chirp signal can be obtained by the second FFT processing. ＩＦ (k) corresponds to the following equation, where r is the target distance, v is the velocity, and c is the light velocity. 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.

[0049] 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 signalＤ (k), the transmission start time T Ｓ (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, compared to when this product is nonlinear, the broadening of the peak is more easily suppressed even if the target velocity increases.

[0050] The reception processing unit 61 acquires the distance and relative velocity of the target as target information based on the result of the second FFT processing. In the subsequent step S50, the reception processing unit 61 outputs the acquired target information. The output processing of the target information includes a process of transmitting the target information to an external device and a process of storing the target information in a storage medium.

[0051] The direction of the detection target can be detected based on the irradiation direction of the beam. If the receiver 12 has multiple receiving antennas RX, the direction may be detected based on the phase difference between the received signals from the receiving antennas RX. The radar device 1 outputs the detected detection target information to a driving control ECU (Electronic Control Unit) that controls the driving of the vehicle, etc.

[0052] According to the first embodiment described above, the center frequency of the chirp signal is adjusted so that the ratio change rate falls within the allowable change rate range over a specific time period. Therefore, it is possible to prevent the product of the time interval and the center frequency of the chirp signal from becoming nonlinear over the 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 the allowable change rate range, and this can alleviate constraints on parameters other than the center frequency. As a result, it is possible to suppress peak broadening and alleviate constraints on the chirp signal.

[0053] Second Embodiment As shown in FIG. 8, the second embodiment is a modification of the first embodiment.

[0054] In the second 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. 8 , 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.

[0055] According to the second 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.

[0056] Third Embodiment As shown in FIG. 9, the third embodiment is a modification of the first embodiment.

[0057] In the third 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 slopes of the center frequency change over time in one transmission cycle. For example, as shown in FIG. 9 , 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.

[0058] According to the third 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.

[0059] Fourth Embodiment As shown in FIG. 10, the fourth embodiment is a modification of the first embodiment.

[0060] The transmission processing unit 60 switches between increasing and decreasing the frequency of each chirp signal over time, and between increasing and decreasing the center frequency of each chirp signal over time, depending on the transmission cycle. For example, as shown in Figure 10, 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.

[0061] Fifth Embodiment As shown in FIG. 11, the fifth embodiment is a modification of the first embodiment.

[0062] In the fifth 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. 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.

[0063] According to the fifth 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 the time intervals are changed 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.

[0064] (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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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).

[0072] (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.

[0073] (Technical Idea 1) A radar device having a processor (6b) that transmits a plurality of signal sets per transmission cycle, each signal set including at least one chirp signal whose frequency varies over time, wherein the processor is configured to execute the following: transmitting the signal sets, each of which has a center frequency of the chirp signal that varies monotonically for each signal set and a time interval between the signal sets that varies linearly over time; and acquiring reception data of reflected signals of the chirp signals that are reflected by a target in the external world; and transmitting the signal sets includes adjusting the center frequency so that, when a frequency change rate is a relative change rate of the center frequency for each signal set with respect to a reference frequency and a time change rate is a relative change rate of the time change rate of the time interval for each signal set with respect to a reference interval, a 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 domain.

[0074] (Technical Idea 2) A radar device according to Technical Idea 1, wherein the signal set is such that the direction of change in the ratio change rate from the subsequent signal set side to the preceding signal set side in each transmission cycle is only one of the positive direction and the negative direction.

[0075] (Technical Idea 3) The radar device according to Technical Idea 1 or 2, wherein transmitting the signal set switches between increasing and decreasing the frequency of the chirp signal over time in accordance with the transmission cycle.

[0076] (Technical Idea 4) The radar device according to any one of Technical Ideas 1 to 3, wherein transmitting the signal set switches between increasing and decreasing the center frequency of each signal set over time in accordance with the transmission cycle.

[0077] (Technical Idea 5) The radar device according to any one of Technical Ideas 1 to 4, wherein transmitting the signal sets includes transmitting a single chirp signal for each of the signal sets.

[0078] (Technical Idea 6) The radar device according to any one of Technical Ideas 1 to 4, wherein transmitting the signal sets includes transmitting a plurality of chirp signals for each of the signal sets.

[0079] The above technical idea may be implemented in the form of a radar control method and a radar control program.

Claims

1. A radar device having a processor (6b) and transmitting a plurality of signal sets per transmission cycle, each signal set including at least one chirp signal whose frequency varies over time, wherein the processor is configured to execute the following: transmitting the signal sets, each of which has a center frequency of the chirp signal that varies monotonically for each of the signal sets and a time interval between the signal sets that varies linearly over time; and acquiring reception data of signals reflected by the chirp signal that is reflected by a target in the external world; and transmitting the signal sets includes adjusting the center frequency so that, when a frequency change rate is a relative change rate of the center frequency for each of the signal sets with respect to a reference frequency, and a time change rate is a relative change rate of the time change rate with respect to the frequency change rate, the ratio change rate is within an allowable change rate range in a specific time domain.

2. A radar device as described in claim 1, wherein the signal set has a variation direction of the ratio change rate from the succeeding signal set to the preceding signal set in each transmission cycle, which is only one of a positive direction and a negative direction.

3. The radar device according to claim 1, wherein transmitting the set of signals switches between increasing and decreasing the frequency of the chirp signal over time in accordance with the transmission cycle.

4. The radar device according to claim 1, wherein transmitting the signal sets switches between increasing and decreasing the center frequency of each of the signal sets over time in accordance with the transmission cycle.

5. The radar system of claim 1, wherein transmitting said set of signals includes transmitting a single chirp signal for each of said set of signals.

6. The radar system of claim 1, wherein transmitting said set of signals includes transmitting a plurality of chirp signals for each of said set of signals.

7. A radar control method executed by a processor (6b) for controlling a radar device (1) that transmits a plurality of signal sets per transmission cycle, each signal set including at least one chirp signal whose frequency varies over time, the method comprising: transmitting the signal sets, the center frequency of the chirp signal varying monotonically for each signal set and the time interval between the signal sets varying linearly over time; and acquiring reception data of signals reflected by the chirp signal on a target in the external world, the transmitting the signal sets comprising: adjusting the center frequency so that a ratio rate of change, which is the relative rate of change of the time rate of change to the frequency rate of change, falls within an allowable rate of change range in a specific time domain, where the relative rate of change of the center frequency for each signal set with respect to a reference frequency is defined as a frequency rate of change, and the relative rate of change of the time interval for each signal set with respect to a reference interval is defined as a time rate of change.

8. A radar control program stored in a storage medium (6a) for controlling a radar device (1) that transmits a plurality of signal sets per transmission cycle, each signal set including at least one chirp signal whose frequency varies over time, the program including instructions for causing a processor (6b) to execute the instructions including: transmitting the signal sets, each of which has a center frequency of the chirp signal that varies monotonically for each signal set and a time interval between the signal sets that varies linearly over time; and acquiring reception data of a signal reflected from a target in the outside world, the chirp signal being reflected by the target; the program including adjusting the center frequency so that, when a frequency change rate is a relative change rate of the center frequency for each signal set with respect to a reference frequency and a time change rate is a relative change rate of the time change rate with respect to the frequency change rate, the ratio change rate is within an allowable change rate range in a specific time domain.

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