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

Abstract

To provide a radar control system or the like capable of suppressing interference while restricting complication of processing.SOLUTION: A processor of a radar control system is configured to execute determination so that at least one of a transmission time zone of a radar wave and a frequency bandwidth in each radar device for each specific cycle related to the radar wave transmission is different from those of other radar devices. The processor is configured to execute instructions so that the radar wave transmission is performed in the determined transmission time zone and the frequency bandwidth with respect to the radar device. The determination of the transmission time zone and the frequency bandwidth includes changing the frequency bandwidth for each specific cycle in a state where a transmission cycle of the radar wave for each radar device is fixed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a radar control technique for controlling a radar mounted on a host vehicle. [Background technology]

[0002] Patent Document 1 discloses a technique for switching modulation modes when external radio wave interference is detected in a radar device so as not to interfere with other radar devices. This technique switches the transmission frequency, transmission period, etc. as modulation modes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-232498 Summary of the Invention [Problem to be solved by the invention]

[0004] However, detecting the presence or absence of radio wave interference one by one as in Patent Document 1 may result in complicated processing. Also, if only the transmission frequency is modulated to avoid interference between multiple radar devices, there is a risk of insufficient frequency bandwidth. Furthermore, modulating the transmission cycle also changes the sampling frequency, which may result in complicated processing to accommodate this.

[0005] An object of the present disclosure is to provide a radar control system capable of suppressing interference while suppressing the complexity of processing. Another object of the present disclosure is to provide a radar control device capable of suppressing interference while suppressing the complexity of processing. Yet another object of the present disclosure is to provide a radar control method capable of suppressing interference while suppressing the complexity of processing. Yet another object of the present disclosure is to provide a radar control program capable of suppressing interference while suppressing the complexity of processing. [Means for solving the problem]

[0006] The technical means of the present disclosure for solving the problems will be described below. Note that the claims and the reference characters in parentheses in this section indicate the correspondence with the specific means described in the embodiments described later in detail, and do not limit the technical scope of the present disclosure.

[0007] A first aspect of the present disclosure includes a processor (102) mounted on a host vehicle (A) for receiving reflected waves from transmitted radar waves and detecting targets. At least three or more A radar control system for controlling a radar device (10), The processor determining a time period and a frequency band for transmitting radar waves in each radar device for each specific cycle of transmitting radar waves so that at least one of the time period and the frequency band is different from those of other radar devices; instructing the radar device to transmit radar waves in the determined transmission time period and frequency band; configured to run Determining the transmission time period and frequency band includes changing the frequency band for each specific cycle while keeping the transmission cycle of the radar wave for each radar device fixed. fruit, Changing the frequency band The method includes setting a group of radar devices having different frequency bands but a common transmission time zone, and one or more radar devices having a different transmission time zone from the group, and changing the frequency band of the group and the frequency band of the one or more radar devices having a different transmission time zone from the group for each specific cycle, while fixing the transmission period of the group and the transmission period of the one or more radar devices having a different transmission time zone from the group. .

[0008] A second aspect of the present disclosure is a radar system having a processor (102) mounted on a host vehicle (A) for detecting a target by receiving a reflected wave in response to a transmitted radar wave. At least three or more A radar control device for controlling the radar device (10), The processor determining a time period and a frequency band for transmitting radar waves in each radar device for each specific cycle of transmitting radar waves so that at least one of the time period and the frequency band is different from those of other radar devices; instructing the radar device to transmit radar waves in the determined transmission time period and frequency band; configured to run Determining the transmission time period and frequency band includes changing the frequency band for each specific cycle while keeping the transmission cycle of the radar wave for each radar device fixed. fruit, Changing the frequency band The method includes setting a group of radar devices having different frequency bands but a common transmission time zone, and one or more radar devices having a different transmission time zone from the group, and changing the frequency band of the group and the frequency band of the one or more radar devices having a different transmission time zone from the group for each specific cycle, while fixing the transmission period of the group and the transmission period of the one or more radar devices having a different transmission time zone from the group. .

[0009] A third aspect of the present disclosure is a radar system mounted on a host vehicle (A) that receives reflected waves from transmitted radar waves and detects targets. At least three or more A radar control method executed by a processor (102) to control a radar device (10) of the present invention, comprising: determining a time period and a frequency band for transmitting radar waves in each radar device for each specific cycle of transmitting radar waves so that at least one of the time period and the frequency band is different from those of other radar devices; instructing the radar device to transmit radar waves in the determined transmission time period and frequency band; Including, Determining the transmission time period and frequency band includes changing the frequency band for each specific cycle while keeping the transmission cycle of the radar wave for each radar device fixed. fruit, Changing the frequency band The method includes setting a group of radar devices having different frequency bands but a common transmission time zone, and one or more radar devices having a different transmission time zone from the group, and changing the frequency band of the group and the frequency band of the one or more radar devices having a different transmission time zone from the group for each specific cycle, while fixing the transmission period of the group and the transmission period of the one or more radar devices having a different transmission time zone from the group. .

[0010] A fourth aspect of the present disclosure is a radar system mounted on a host vehicle (A) that receives reflected waves from transmitted radar waves and detects targets. At least three or more A radar control program is stored in a storage medium (101) for controlling the radar device (10) and includes instructions to be executed by a processor (102), The command is, determining a time period and a frequency band for transmitting radar waves in each radar device for each specific cycle of transmitting radar waves so that at least one of the time period and the frequency band is different from those of other radar devices; instructing the radar device to transmit radar waves in the determined transmission time period and frequency band; Including, Determining the transmission time period and frequency band means changing the frequency band for each specific cycle while keeping the transmission cycle of the radar wave for each radar device fixed. Let Including fruit, Changing the frequency band The method includes setting a group of radar devices having different frequency bands but a common transmission time zone, and one or more radar devices having a different transmission time zone from the group, and changing the frequency band of the group and the frequency band of the one or more radar devices having a different transmission time zone from the group for each specific cycle, while fixing the transmission period of the group and the transmission period of the one or more radar devices having a different transmission time zone from the group. .

[0011] According to the first to fourth aspects, either the transmission time period or the frequency band can be made different between radar devices, thereby avoiding a shortage of frequency bands. Furthermore, since the frequency band is changed for each specific cycle while the transmission period of the radar wave for each radar device is fixed, it is possible to avoid the need to perform processes for detecting the presence or absence of radio wave interference and processes for dealing with modulation of the transmission period. Therefore, it is possible to suppress interference while minimizing the complexity of the process. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing the overall configuration of a first embodiment. [Figure 2] 1 is a schematic diagram showing a host vehicle and a radar device to which a first embodiment is applied; [Figure 3] FIG. 2 is a block diagram showing the functional configuration of the radar control system according to the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating a control of the radar device according to the first embodiment. [Figure 5] 4 is a table showing an example of control parameters for each cycle of the radar device according to the first embodiment. [Figure 6] 3 is a flowchart illustrating a radar control method according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0015] (First embodiment) The radar control system 100 of the first embodiment shown in Fig. 1 controls multiple radar devices 10 mounted on a host vehicle A shown in Fig. 2. From a perspective centered on the host vehicle A, the host vehicle A can also be said to be an ego-vehicle. From a perspective centered on the host vehicle A, the target vehicles can also be said to be other road users.

[0016] The host vehicle A is provided with an autonomous driving mode that is classified into levels according to the degree of manual intervention by the occupant in the driving task. The autonomous driving mode may be realized by autonomous driving control, such as conditional driving automation, high driving automation, or full driving automation, in which the system performs all driving tasks when activated. The autonomous driving mode may also be realized by advanced driving assistance control, such as driving assistance or partial driving automation, in which the occupant performs some or all driving tasks. The autonomous driving mode may be realized by either autonomous driving control or advanced driving assistance control, or by a combination of these, or by switching between them.

[0017] The host vehicle A is equipped with an on-board radar system 1 shown in Figures 1 and 3. The on-board radar system 1 includes a plurality of radar devices 10 controlled by a radar control system 100. The radar device 10 transmits a transmission wave, receives the transmission wave (reflected wave) reflected by an object as a received wave, and detects the distance to the target, which is the object that reflected the transmission wave, the relative speed to the target, and the direction of the target as target information.

[0018] For example, as shown in Fig. 2, the multiple radar devices 10 are arranged substantially symmetrically with respect to the host vehicle A. Specifically, the multiple radar devices 10 are arranged substantially symmetrically left-right and front-rear on the host vehicle A. This allows the radar devices 10 to detect different detection ranges, as shown by the dotted lines in Fig. 2. Alternatively, the detection ranges may at least partially overlap. Note that Fig. 2 shows an example in which six radar devices 10 are mounted on the host vehicle A, but the number of radar devices 10 is not limited to this.

[0019] The radar device 10 includes a transmitter 11, a receiver 12, and a target detection unit 13. The transmitter 11 includes a transmission control unit and a transmission antenna. The transmission control unit generates a millimeter-wave electromagnetic signal, which is a radar wave transmitted from the transmission antenna. The transmission control unit generates the electromagnetic signal to be transmitted in a specified transmission time slot, frequency channel (frequency band), chirp period, and CDM code. The transmission control unit distributes the electromagnetic signal at a specified ratio between a transmission signal supplied to the transmission antenna and a local signal supplied to a signal mixer (described later).

[0020] The receiving unit 12 includes a receiving antenna and a signal mixing unit. The receiving antenna receives an electromagnetic wave signal reflected by an object. The receiving antenna generates a received signal corresponding to the received electromagnetic wave signal. The signal mixing unit generates a beat signal by mixing the received signal from the receiving antenna with a local signal. The beat signal generated by the signal mixing unit is filtered by a low-pass filter, allowing only the beat signal corresponding to the frequency difference between the received signal and the local signal to pass. The beat signal is input to the target detection unit 13.

[0021] The target detection unit 13 detects the distance to the target and the relative velocity of the target by analyzing, using FFT processing or the like, the beat signal input from the receiving unit 12 when the radar wave is transmitted and the received wave is received. For example, in the case of the FCM radar device 10, a beat signal is generated from the transmitted signal (more specifically, the local signal) and the received signal, and the beat signal is subjected to two FFT processes to detect the distance to the target and the relative velocity of the target.

[0022] More specifically, the beat signal is subjected to FFT processing for each chirp. This results in a frequency spectrum for each chirp that shows a peak at the frequency position corresponding to the distance to the target. The distance to the target can be calculated by detecting which frequency bin (also called the distance bin) the peak frequency is located in.

[0023] When the relative velocity with respect to the target is not zero, the frequency spectrum corresponding to each chirp shows a peak in the same distance bin, but the phases of the chirps are different. This phase difference between the chirps is due to the change in distance between the radar device 10 and the target. The FCM method utilizes this to detect the relative velocity with respect to the target. Specifically, as the second FFT process, FFT processing is performed 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 spectrum showing a peak at a position corresponding to the relative velocity with respect to the target. The relative velocity with respect to the target is detected by detecting which frequency bin (also referred to as the speed bin) the peak frequency of this spectrum is located in. The azimuth of the target can be detected based on the beam direction. The target detection unit 13 outputs the detected target information to a driving control ECU (Electronic Control Unit) or the like that controls the driving of the host vehicle A.

[0024] The radar control system 100 is connected to an on-vehicle radar system 1, i.e., a plurality of radar devices 10, via at least one of a LAN (Local Area Network) line, a wire harness, an internal bus, and a wireless communication line. The radar control system 100 includes at least one dedicated computer. The dedicated computer constituting the radar control system 100 is a central control device that comprehensively controls the plurality of radar devices 10 in the on-vehicle radar system 1.

[0025] The dedicated computer constituting the radar control system 100 may be a driving control ECU (Electronic Control Unit) that controls the driving of the host vehicle A. The dedicated computer constituting the radar control system 100 may be a navigation ECU that navigates the driving route of the host vehicle A. The dedicated computer constituting the radar control system 100 may be a locator ECU that estimates the self-state quantity of the host vehicle A. The dedicated computer constituting the radar control system 100 may be an actuator ECU that controls the driving actuator of the host vehicle A. The dedicated computer constituting the radar control system 100 may be an HCU (Human Machine Interface Control Unit (HMI)) that controls the presentation of information in the host vehicle A. The dedicated computer constituting the radar control system 100 may be a computer other than the host vehicle A that constitutes, for example, an external center or a mobile terminal that can communicate via a V2X type communication system 20.

[0026] The dedicated computer constituting the radar control system 100 has at least one memory 101 and one processor 102. The memory 101 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, data, etc. The processor 102 includes at least one type of core, such as a central processing unit (CPU), a graphics processing unit (GPU), a reduced instruction set computer (RISC)-CPU, a data flow processor (DFP), or a graph streaming processor (GSP).

[0027] In the radar control system 100, a processor 102 executes a plurality of instructions included in a radar control program stored in a memory 101 to control a plurality of radar devices 10 mounted on a host vehicle A. In this way, the radar control system 100 constructs a plurality of function blocks for controlling the radar devices 10. The plurality of function blocks constructed in the radar control system 100 include a decision block 110 and an instruction block 120, as shown in FIG. 3 .

[0028] The determination block 110 determines the radar wave transmission time period and frequency channel for each radar wave transmission cycle for the multiple radar devices 10. The transmission cycle is an example of a "specific cycle for radar wave transmission." The determination block 110 determines at least one of the transmission time period and frequency channel for each radar device 10 so that it is different from those of the other radar devices 10.

[0029] The determination block 110 determines the transmission time slots of the radar devices 10 to be relatively fixed within each cycle throughout multiple transmission cycles. In other words, the difference in the relative transmission start times between the radar devices 10 is fixed within each cycle throughout multiple transmission cycles. For example, the determination block 110 may pre-determine combinations of radar devices 10 with different transmission time slots and combinations of radar devices 10 with overlapping transmission time slots. In the example shown in FIG. 4, the first radar device and the second radar device are determined to have different transmission time slots, and the first radar device and the third radar device are determined to have the same transmission time slot.

[0030] For the frequency channel of each radar device 10, the decision block 110 changes the frequency channel for each radar wave transmission cycle while keeping the radar wave transmission cycle for each radar device 10 fixed.

[0031] More specifically, first, the decision block 110 determines the next (or first) frequency channel for a particular radar device 10. For example, the decision block 110 may determine the frequency channel based on a pseudo-random function.

[0032] Next, the decision block 110 allocates the next (or first) frequency channel to the other radar devices 10. At this time, the decision block 110 allocates different frequency channels to at least the radar devices 10 whose transmission time periods overlap. The decision block 110 may also allocate different frequency channels to the radar devices 10 whose transmission time periods differ. The decision block 110 allocates the multiple allocatable frequency channels to each radar device 10 substantially equally.

[0033] The decision block 110 repeats the process of determining the frequency channel for one particular radar device 10 and allocating frequency channels to other radar devices 10 for each transmission cycle.

[0034] The determination block 110 refers to the location and detection direction of each radar device 10 when determining the transmission time zone and frequency channel. The locations and detection directions are information stored in advance in a storage medium such as the memory 101. The determination block 110 determines a combination of radar devices 10 that are allowed to have overlapping transmission time zones or frequency channels based on this information. For example, the determination block 110 allows overlapping transmission time zones or frequency channels between radar devices 10 that are located on opposite sides of the host vehicle A. Then, the determination block 110 prohibits overlapping of at least one of the transmission time zones or frequency channels between radar devices 10 that are adjacent to each other or have detection directions in the same direction.

[0035] Additionally, the decision block 110 determines a CDM code, which is a code used for code division multiplexing modulation in at least one radar device 10, so that it is different from that of the other radar devices 10. The decision block 110 may change or fix the CDM code for each transmission cycle. Furthermore, the decision block 110 determines a common chirp period for multiple radar devices 10. The decision block 110 may change or fix the chirp period for each transmission cycle as long as the chirp period of each radar device 10 is common in the same transmission cycle.

[0036] The instruction block 120 transmits an operation instruction based on the transmission time zone, frequency channel, chirp period, and CDM code determined above to each radar device 10. Upon receiving the operation instruction, each radar device 10 outputs a radar wave according to the operation instruction from its transmitter 11. As a result, the radar device 10 is controlled with different parameters for each transmission cycle, as shown in FIG.

[0037] The flow of the radar control method (hereinafter referred to as radar control flow) in which the radar control system 100 controls the multiple radar devices 10 mounted on the host vehicle A through cooperation of the blocks 110 and 120 described above will be described below with reference to Fig. 6. This processing flow is repeatedly executed while the host vehicle A is running. Note that each "S" in this processing flow represents multiple steps executed by multiple commands included in the radar control program.

[0038] First, in S10, the decision block 110 determines the transmission time zone for each radar device 10. At this time, the decision block 110 determines different transmission time zones for at least combinations of transmission time zones that are prohibited from overlapping. Next, in S20, a common chirp period is determined for the multiple radar devices 10. Then, in S30, the CDM code for at least one radar device 10 is determined to be different from that of the other radar devices 10. Note that the processes of S10, S20, and S30 may be performed in parallel. Alternatively, the processes of S10, S20, and S30 may be performed in an order different from that of the flow in FIG. 6.

[0039] In the next step S40, the decision block 110 determines the frequency channel for the specific radar device 10 in the next transmission cycle. Then, in step S50, frequency channels for the other radar devices 10 in the next transmission cycle are allocated.

[0040] Next, in S60, the instruction block 120 transmits an operation instruction for the transmission time zone, frequency channel, chirp period, and CDM code determined in the above process to each radar device 10. After the process of S60, the process returns to S40, and the frequency channel for each radar device 10 in the next transmission cycle is determined. By repeating the processes of S40, S50, and S60, the frequency channel for each radar device 10 is changed for each transmission cycle.

[0041] The above flow shows the process when the CDM code is not changed with the progress of the transmission cycle. If the CDM code is changed with each transmission cycle, the process returns to S30 after S60, and the CDM code is re-determined. Also, the chirp period may be changed with each transmission cycle by returning to S20 after S60.

[0042] According to the first embodiment described above, it is possible to avoid a shortage of frequency bands by varying either the transmission time period or the frequency band among the radar devices 10. Furthermore, since the frequency band is changed for each specific cycle while the transmission cycle of the radar wave for each radar device 10 is fixed, it is possible to avoid the need to perform processing to detect the presence or absence of radio wave interference and processing to deal with modulation of the transmission cycle. Therefore, it is possible to suppress interference while minimizing the complexity of processing.

[0043] (Other embodiments) Although one embodiment has been described above, the present disclosure should not be construed as being limited to the embodiment described above, and can be applied to various embodiments within the scope that does not deviate from the gist of the present disclosure.

[0044] In a modified example, the decision block 110 may allocate a frequency band for the radar device 10 in the host vehicle A based on frequency band information of radar waves transmitted from the radar device 10 mounted on another target vehicle.

[0045] In a variant, the decision block 110 may also determine the orientation of the plane of polarization of the radar wave.

[0046] In a variant, the decision block 110 may change the frequency band every particular cycle, which may include multiple consecutive transmission cycles.

[0047] In a modified example, the functions of the radar control system 100 may be performed by one of the multiple radar devices 10.

[0048] In a modified example, the dedicated computer constituting the radar control system 100 may have at least one of a digital circuit and an analog circuit as a processor. Here, the digital circuit is at least one of an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a system on a chip (SOC), a programmable gate array (PGA), and a complex programmable logic device (CPLD). Such a digital circuit may also have a memory that stores a program.

[0049] In addition to the embodiments described above, the radar control system 100 according to the above-described embodiments and modifications may be implemented as a radar control device that is a processing device (e.g., a processing ECU) mounted on the host vehicle A. Furthermore, the above-described embodiments and modifications may be implemented as a semiconductor device (e.g., a semiconductor chip) having at least one processor 102 and one memory 101 of the radar control system 100. [Explanation of symbols]

[0050] 10: Radar device, 100: Radar control system, 101: Memory (storage medium), 102: Processor, A: Host vehicle

Claims

1. A radar control system having a processor (102) and controlling at least three radar devices (10) mounted on a host vehicle (A) that receive reflected waves in response to transmitted radar waves and detect targets, The processor: determining a transmission time period and a frequency band of the radar wave for each of the radar devices for each specific cycle of transmitting the radar wave so that at least one of the transmission time period and the frequency band is different from those of the other radar devices; instructing the radar device to transmit the radar wave in the determined transmission time period and frequency band; configured to run determining the transmission time period and the frequency band includes changing the frequency band for each specific cycle while keeping a fixed transmission period of the radar wave for each radar device; Changing the frequency band includes: a transmission period of the group and the transmission period of the one or more radar devices whose transmission time zones are different from those of the group, while fixing the transmission period of the group and the transmission period of the one or more radar devices whose transmission time zones are different from those of the group, and changing the frequency band of the group and the frequency band of the one or more radar devices whose transmission time zones are different from those of the group, for each specific cycle.

2. 2. The radar control system according to claim 1, wherein determining the transmission time period and the frequency band includes setting a code used for code division multiplex modulation of the radar wave in at least one of the radar devices to be different from that in the other radar devices.

3. 3. The radar control system according to claim 1, wherein determining the transmission time period and the frequency band includes determining a common chirp period for the plurality of radar devices.

4. 4. The radar control system according to claim 1, wherein determining the transmission time zone and the frequency band includes determining a combination of the radar devices that allows overlap of the transmission time zone or the frequency band based on an arrangement of the radar devices in the host vehicle.

5. A radar control device having a processor (102) and controlling at least three radar devices (10) mounted on a host vehicle (A) that receive reflected waves in response to transmitted radar waves and detect targets, The processor: determining a transmission time period and a frequency band of the radar wave for each of the radar devices for each specific cycle of transmitting the radar wave so that at least one of the transmission time period and the frequency band is different from those of the other radar devices; instructing the radar device to transmit the radar wave in the determined transmission time period and frequency band; configured to run determining the transmission time period and the frequency band includes changing the frequency band for each specific cycle while keeping a fixed transmission period of the radar wave for each radar device; Changing the frequency band includes: a transmission period of the group and the transmission period of the one or more radar devices whose transmission time zones are different from those of the group, while fixing the transmission period of the group and the transmission period of the one or more radar devices whose transmission time zones are different from those of the group, for each specific cycle;

6. A radar control method executed by a processor (102) for controlling at least three radar devices (10) mounted on a host vehicle (A) and configured to receive reflected waves in response to transmitted radar waves and detect targets, comprising: determining a transmission time period and a frequency band of the radar wave for each of the radar devices for each specific cycle of transmitting the radar wave so that at least one of the transmission time period and the frequency band is different from those of the other radar devices; instructing the radar device to transmit the radar wave in the determined transmission time period and frequency band; Including, determining the transmission time period and the frequency band includes changing the frequency band for each specific cycle while keeping a fixed transmission period of the radar wave for each radar device; Changing the frequency band includes: a transmission period of the group and the transmission period of the one or more radar devices whose transmission time zones are different from those of the group, while fixing the transmission period of the group and the one or more radar devices whose transmission time zones are different from those of the group, for each specific cycle;

7. A radar control program is stored in a storage medium (101) for controlling at least three radar devices (10) mounted on a host vehicle (A) and configured to receive reflected waves from transmitted radar waves and detect targets, the program including instructions to be executed by a processor (102), The instruction: determining, for each specific cycle related to the transmission of the radar waves, a time period and a frequency band of the radar waves for each of the radar devices such that at least one of the time period and the frequency band is different from those of the other radar devices; instructing the radar device to transmit the radar wave in the determined transmission time period and frequency band; Including, determining the transmission time period and the frequency band includes changing the frequency band for each specific cycle while keeping a fixed transmission cycle of the radar wave for each radar device; The changing of the frequency band includes: a transmission period of the group and the transmission period of the one or more radar devices whose transmission time zones are different from those of the group are fixed, and the frequency band of the group and the frequency band of the one or more radar devices whose transmission time zones are different from those of the group are changed for each specific cycle.

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