Synchronization establishment device, synchronization establishment method, and distributed radar system

Abstract

A synchronization establishment device (26) is configured to comprise: a reception signal acquisition unit (31) that, when a transmission signal is transmitted from a master radar device (1) and a slave radar device (2-m) (m=1,...,M) receives a reflected wave of the transmission signal reflected by a target having a known position, acquires a reception signal of the reflected wave; a first propagation delay time calculation unit (32) that, on the basis of the reception signal acquired by the reception signal acquisition unit (31), calculates a first propagation delay time, which is a propagation delay time of the reflected wave; and a second propagation delay time calculation unit (33) that, from the position of the target and the position of the slave radar device (2-m), calculates a second propagation delay time as a true propagation delay time of the reflected wave. The synchronization establishment device (26) further comprises a transmission timing control unit (34) that, on the basis of the first propagation delay time calculated by the first propagation delay time calculation unit (32) and the second propagation delay time calculated by the second propagation delay time calculation unit (33), controls a transmission timing of the transmission signal transmitted from the slave radar device (2-m).

Description

Synchronization establishment device, synchronization establishment method, and distributed radar system

[0001] The present disclosure relates to a synchronization establishment device, a synchronization establishment method, and a distributed radar system.

[0002] There is a distributed radar system that includes multiple radar devices. For example, Patent Document 1 discloses a distributed radar system that includes a master radar device (hereinafter referred to as a "master radar device") and multiple slave radar devices (hereinafter referred to as "slave radar devices"). The master radar device has a synchronization control unit (hereinafter referred to as a "first synchronization control unit"), and each slave radar device has a synchronization control unit (hereinafter referred to as a "second synchronization control unit"). The first synchronization control unit is connected to each second synchronization control unit via a synchronization signal line. To synchronize the master radar device and the multiple slave radar devices, the first synchronization control unit outputs a synchronization signal to each second synchronization control unit via the synchronization signal line.

[0003] Japanese Patent Application Laid-Open No. 2021-12140

[0004] The distributed radar system disclosed in Patent Document 1 has a problem in that the number of synchronization signal lines for transmitting synchronization signals increases as the number of slave radar devices increases.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a synchronization establishment device that can synchronize a master radar device and a slave radar device without connecting the master radar device and the slave radar device with a synchronization signal line.

[0006] A synchronization establishment device according to the present disclosure includes a received signal acquisition unit that acquires a received signal of the reflected wave when a transmission signal is transmitted from a master radar device and the reflected wave of the transmission signal reflected by a target whose position is known is received by a slave radar device, a first propagation delay time calculation unit that calculates a first propagation delay time that is the propagation delay time of the reflected wave based on the received signal acquired by the received signal acquisition unit, and a second propagation delay time calculation unit that calculates a second propagation delay time as the true propagation delay time of the reflected wave from the position of the target and the position of the slave radar device. The synchronization establishment device also includes a transmission timing control unit that controls the transmission timing of the transmission signal transmitted from the slave radar device based on the first propagation delay time calculated by the first propagation delay time calculation unit and the second propagation delay time calculated by the second propagation delay time calculation unit.

[0007] According to the present disclosure, it is possible to synchronize the master radar device and the slave radar device without connecting the master radar device and the slave radar device with a synchronization signal line.

[0008] FIG. 1 is a configuration diagram showing a distributed radar system according to a first embodiment. FIG. 1 is a configuration diagram showing a synchronization establishment device 26 implemented in a slave radar device 2-m (m = 1, ..., M) according to the first embodiment. FIG. 2 is a hardware configuration diagram showing the hardware of the synchronization establishment device 26. FIG. 3 is a hardware configuration diagram of a computer in the case where the synchronization establishment device 26 is realized by software, firmware, or the like. FIG. 4 is an explanatory diagram showing the time waveform of a transmission signal radiated from the transmitting antenna 13 of the master radar device 1 and the time waveform of a reflected wave received by the receiving antenna 24 of the slave radar device 2-m (m = 1, ..., M). FIG. 5 is a flowchart showing a synchronization establishment method which is a processing procedure of the synchronization establishment device 26. FIG. 6 is a configuration diagram showing a distributed radar system according to a second embodiment. FIG. 7 is a configuration diagram showing another distributed radar system according to the second embodiment.

[0009] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] First Embodiment Fig. 1 is a configuration diagram showing a distributed radar system according to a first embodiment. The distributed radar system shown in Fig. 1 includes a master radar device 1 and M slave radar devices 2-1 to 2-M, where M is an integer equal to or greater than 1. The master radar device 1 and the slave radar devices 2-1 to 2-M are mounted on the same vehicle, for example.

[0011] The master radar device 1 includes a signal oscillator 11, a transmitter 12, a transmitting antenna 13, a receiving antenna 14, a receiver 15, and a received signal output unit 16. The signal oscillator 11 is an oscillator that oscillates a transmission signal and outputs the transmission signal to the transmitter 12. The transmitter 12 modulates the transmission signal output from the signal oscillator 11 and outputs the modulated transmission signal to each of the transmitting antenna 13 and the receiver 15. The transmitting antenna 13 radiates the modulated transmission signal output from the transmitter 12 into space.

[0012] The receiving antenna 14 receives a reflected wave of the transmission signal that has been radiated from the transmitting antenna 13 and then reflected by a target or the like, and outputs a received signal of the reflected wave to the receiving unit 15. The receiving unit 15 demodulates the received signal output from the receiving antenna 14 using the modulated transmission signal output from the transmitting unit 12, and outputs the demodulated received signal to the received signal output unit 16. The received signal output unit 16 outputs the demodulated received signal to the distributed radar processing unit 60, which will be described later.

[0013] 2 is a configuration diagram showing the synchronization establishment device 26 implemented in the slave radar device 2-m (m = 1, ..., M) according to the first embodiment. Fig. 3 is a hardware configuration diagram showing the hardware of the synchronization establishment device 26. The slave radar device 2-m (m = 1, ..., M) includes a signal oscillator 21, a transmitter 22, a transmitting antenna 23, a receiving antenna 24, a receiver 25, the synchronization establishment device 26, and a received signal output unit 35.

[0014] The signal oscillator 21 is an oscillator that oscillates a transmission signal and outputs the transmission signal to the transmitter 22. The transmitter 22 modulates the transmission signal output from the signal oscillator 21 and outputs the modulated transmission signal to the transmitter antenna 23 and the receiver 25. The transmitter antenna 23 radiates the modulated transmission signal output from the transmitter 22 into space.

[0015] The receiving antenna 24 receives a reflected wave of the transmission signal that is radiated from the transmitting antenna 23 and then reflected by a target. When synchronizing the master radar device 1 and the slave radar devices 2-m (m = 1, ..., M), the receiving antenna 24 receives a reflected wave of the transmission signal that is radiated from the transmitting antenna 13 of the master radar device 1 and then reflected by a target whose position is known. The receiving antenna 24 outputs a received signal of the reflected wave to the receiving unit 25. The receiving unit 25 demodulates the received signal output from the receiving antenna 24 using the modulated transmission signal output from the transmitting unit 22, and outputs the demodulated received signal to the synchronization establishment device 26 and the received signal output unit 35.

[0016] The synchronization establishment device 26 includes a received signal acquisition unit 31, a first propagation delay time calculation unit 32, a second propagation delay time calculation unit 33, and a transmission timing control unit 34. The received signal acquisition unit 31 is realized, for example, by a received signal acquisition circuit 41 shown in FIG. 3. When a transmission signal is transmitted from the master radar device 1 and a reflected wave of the transmission signal reflected by a target whose position is known is received by a slave radar device 2-m (m = 1, ..., M), the received signal acquisition unit 31 acquires a received signal of the reflected wave from the receiving unit 25. The received signal acquisition unit 31 outputs the received signal of the reflected wave to the first propagation delay time calculation unit 32.

[0017] The first propagation delay time calculation unit 32 is realized by, for example, the first propagation delay time calculation circuit 42 shown in Fig. 3. The first propagation delay time calculation unit 32 acquires the received signal of the reflected wave from the received signal acquisition unit 31. The first propagation delay time calculation unit 32 calculates a first propagation delay time, which is the propagation delay time of the reflected wave, based on the received signal of the reflected wave. The first propagation delay time calculation unit 32 outputs the first propagation delay time to the transmission timing control unit 34.

[0018] The second propagation delay time calculation unit 33 is realized by, for example, the second propagation delay time calculation circuit 43 shown in Fig. 3. The second propagation delay time calculation unit 33 calculates the second propagation delay time as the true propagation delay time of the reflected wave from the position of the target and the position of the slave radar device 2-m (m = 1, ..., M). The second propagation delay time calculation unit 33 outputs the second propagation delay time to the transmission timing control unit 34.

[0019] The transmission timing control unit 34 is realized by, for example, the transmission timing control circuit 44 shown in Fig. 3. The transmission timing control unit 34 acquires the first propagation delay time from the first propagation delay time calculation unit 32 and acquires the second propagation delay time from the second propagation delay time calculation unit 33. The transmission timing control unit 34 controls the transmission timing of the transmission signal transmitted from the slave radar device 2-m (m = 1, ..., M) based on the first propagation delay time and the second propagation delay time.

[0020] The received signal output unit 35 acquires the demodulated received signal from the receiver 25. The received signal output unit 35 outputs the demodulated received signal to the distributed radar processing unit 60.

[0021] The distributed radar processing unit 60 acquires demodulated received signals from the master radar device 1 and the M slave radar devices 2-1 to 2-M. The distributed radar processing unit 60 combines the multiple received signals and outputs the combined received signal to a target detection unit (not shown) or the like.

[0022] 2, it is assumed that the components of the synchronization establishment device 26, namely, the received signal acquisition unit 31, the first propagation delay time calculation unit 32, the second propagation delay time calculation unit 33, and the transmission timing control unit 34, are each realized by dedicated hardware as shown in Fig. 3. That is, it is assumed that the synchronization establishment device 26 is realized by a received signal acquisition circuit 41, a first propagation delay time calculation circuit 42, a second propagation delay time calculation circuit 43, and a transmission timing control circuit 44. Each of the received signal acquisition circuit 41, the first propagation delay time calculation circuit 42, the second propagation delay time calculation circuit 43, and the transmission timing control circuit 44 is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0023] The components of the synchronization establishment device 26 are not limited to those realized by dedicated hardware, and the synchronization establishment device 26 may be realized by software, firmware, or a combination of software and firmware. Software or firmware is stored as a program in the memory of a computer. A computer refers to hardware that executes a program, and includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor).

[0024] 4 is a hardware configuration diagram of a computer when the synchronization establishment device 26 is realized by software, firmware, etc. When the synchronization establishment device 26 is realized by software, firmware, etc., a program for causing the computer to execute the respective processing procedures of the received signal acquisition unit 31, the first propagation delay time calculation unit 32, the second propagation delay time calculation unit 33, and the transmission timing control unit 34 is stored in a memory 51. Then, a processor 52 of the computer executes the program stored in the memory 51.

[0025] 3 shows an example in which each of the components of the synchronization establishment device 26 is realized by dedicated hardware, while Fig. 4 shows an example in which the synchronization establishment device 26 is realized by software, firmware, etc. However, this is merely an example, and some of the components of the synchronization establishment device 26 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0026] Next, the operation of the distributed radar system shown in Fig. 1 will be described. The distributed radar system shown in Fig. 1 combines a transmission signal transmitted from a master radar device 1, a received signal of the reflected wave of the transmitted signal received by the master radar device 1 (hereinafter referred to as a "first received signal"), and a transmission signal transmitted from a slave radar device 2-m (m = 1, ..., M), a received signal of the reflected wave of the transmitted signal received by the slave radar device 2-m (hereinafter referred to as a "second received signal"). In this case, if there is a discrepancy between the reception time of the first received signal at the master radar device 1 and the reception time of the second received signal at the slave radar device 2-m, even if a target detection unit (not shown) or the like acquires a combined signal of the first received signal and the second received signal, it is not possible to improve the detection accuracy of targets or the like. The slave radar device 2-m is equipped with a synchronization establishment device 26 to perform a process (hereinafter referred to as "calibration process") to eliminate the discrepancy between the reception time of the first reception signal at the master radar device 1 and the reception time of the second reception signal at the slave radar device 2-m.

[0027] The synchronization establishment device 26 operates when the calibration process is performed, but does not operate during radar operation after the calibration process. Here, a process for synchronizing the time when a transmission signal is transmitted from the master radar device 1 and the reflected wave of the transmission signal is received by the slave radar device 2-m (m = 1, ..., M) with the time when a transmission signal is transmitted from the slave radar device 2-m and the reflected wave of the transmission signal is received by the slave radar device 2-m will be described.

[0028] The signal oscillator 11 of the master radar device 1 oscillates a transmission signal and outputs the transmission signal to the transmitter 12. The transmitter 12 acquires the transmission signal from the signal oscillator 11. The transmitter 12 modulates the transmission signal and outputs the modulated transmission signal to the transmitter antenna 13 and the receiver 15. The transmitter antenna 13 radiates the modulated transmission signal output from the transmitter 12 into space. The transmission signal radiated into space from the transmitter antenna 13 is reflected by a target whose position is known. An example of a target whose position is known is any target present in the direction of travel of a vehicle equipped with the master radar device 1 and the slave radar devices 2-1 to 2-M. Examples of such targets include traffic lights and signs. Position data indicating the position of the target is included in map data of a car navigation device equipped in the vehicle.

[0029] The receiving antenna 24 of the slave radar device 2-m (m=1, . . . , M) receives the reflected wave of the transmission signal that is radiated from the transmitting antenna 13 of the master radar device 1 and then reflected by the target. The receiving antenna 24 receives the reflected wave reception signal S ｔｇｔ，２１ The receiving unit 25 outputs the received signal S (t) output from the receiving antenna 24. ｔｇｔ，２１ The demodulated received signal is output to the synchronization establishment device 26.

[0030] In formula (1), A ｔｇｔ，２１ is the received signal S ｔｇｔ，２１ (t) amplitude, f ０is the carrier frequency of the transmission signal, R is the distance between the slave radar device 2-m and the target, and Δτ ｅｒｒ is the synchronization error time, which is the delay error of the slave radar device 2-m relative to the reference time, k is the slope of the chirp signal, which is the transmission signal, and c is the speed of light. ｅｒｒ is the general amplitude and phase error, a ＭＤＬ (θ) is the array factor between radar devices, S ＭＩＭＯ (h) is the received signal S ｔｇｔ，２１ (t) is the signal modulated in the hit direction.

[0031] 5 is an explanatory diagram showing the time waveform of a transmission signal emitted from the transmitting antenna 13 of the master radar device 1 and the time waveform of a reflected wave received by the receiving antenna 24 of the slave radar device 2-m (m = 1, ..., M). In FIG. 5, the horizontal axis represents time and the vertical axis represents frequency. The frequencies of the transmission signal and the reflected wave increase from the lowest frequency to the highest frequency over time, then return to the lowest frequency, and then increase again from the lowest frequency to the highest frequency over time. Such a transmission signal is sometimes called a chirp signal.

[0032] 6 is a flowchart showing a synchronization establishment method, which is a processing procedure of the synchronization establishment device 26. The received signal acquisition unit 31 of the synchronization establishment device 26 acquires a received signal of a reflected wave from the receiver 25 (step ST1 in FIG. 6 ). The received signal acquisition unit 31 outputs the received signal of a reflected wave to the first propagation delay time calculation unit 32.

[0033] The first propagation delay time calculation unit 32 acquires the received signal of the reflected wave from the received signal acquisition unit 31. The first propagation delay time calculation unit 32 calculates a first propagation delay time τ ｏｂｓ，２１ (Step ST2 in FIG. 6). The first propagation delay time calculation unit 32 calculates the first propagation delay time τ ｏｂｓ，２１ to the transmission timing control unit 34. Hereinafter, the first propagation delay time τ ｏｂｓ，２１ The calculation process will be specifically described below.

[0034] The first propagation delay time calculation unit 32 converts the received signal of the reflected wave into a frequency domain signal by performing an FFT (Fast Fourier Transform) on the received signal of the reflected wave in the fast time direction. Next, the first propagation delay time calculation unit 32 calculates the distance L between the target and the slave radar device 2-m by performing an FFT on the frequency domain signal in the slow time direction. The process of calculating the distance L is a well-known technique, and therefore a detailed description thereof will be omitted. As shown in the following equation (2), the first propagation delay time calculation unit 32 calculates a first propagation delay time τ, which is the propagation delay time of the reflected wave, by dividing the distance L by the speed of light c, which is the transmission signal. ｏｂｓ，２１ Calculate τ ｏｂｓ，２１ = L / c (2)

[0035] The second propagation delay time calculation unit 33 calculates the second propagation delay time τ from the position of the target and the position of the slave radar device 2-m (m=1, . . . , M) as the true propagation delay time of the reflected wave. ｔｒｕｅ (Step ST3 in FIG. 6). The second propagation delay time calculation unit 33 calculates the second propagation delay time τ ｔｒｕｅ to the transmission timing control unit 34. Hereinafter, the second propagation delay time calculation unit 33 calculates the second propagation delay time τ ｔｒｕｅ The calculation process will be specifically described below.

[0036] As shown in FIG. 5, the reflected wave is delayed by a first propagation delay time τ ｏｂｓ，２１ In the example of FIG. 5, the second propagation delay time τ ｔｒｕｅ is the first propagation delay time τ ｏｂｓ，２１The second propagation delay time calculation unit 33 acquires, for example, a GPS (Global Positioning System) signal from a car navigation device mounted on the vehicle, and determines the position of the slave radar device 2-m based on the GPS signal. The second propagation delay time calculation unit 33 also acquires, for example, map data from the car navigation device mounted on the vehicle, and determines the position of the target based on the map data. The second propagation delay time calculation unit 33 calculates the distance L' between the target and the slave radar device 2-m based on the position of the target and the position of the slave radar device 2-m. As shown in the following equation (3), the second propagation delay time calculation unit 33 divides the distance L' by the speed of light c, which is the transmission signal, to obtain the second propagation delay time τ, which is the true propagation delay time of the reflected wave. ｔｒｕｅ Calculate τ ｔｒｕｅ = L' / c (3)

[0037] The transmission timing control unit 34 receives the first propagation delay time τ from the first propagation delay time calculation unit 32. ｏｂｓ，２１ and the second propagation delay time τ ｔｒｕｅ The transmission timing control unit 34 obtains the first propagation delay time τ ｏｂｓ，２１ and the second propagation delay time τ ｔｒｕｅ Based on this, the transmission timing of the transmission signal transmitted from the slave radar device 2-m (m=1, . . . , M) is controlled (step ST4 in FIG. 6). The transmission timing control process by the transmission timing control unit 34 will now be described in detail.

[0038] The transmission timing control unit 34 calculates the first propagation delay time τ as shown in the following equation (4): ｏｂｓ，２１ and the second propagation delay time τ ｔｒｕｅ The difference between the two is the synchronization deviation time Δτ ｅｒｒ Calculate as follows: Δτ ｅｒｒ = τ ｏｂｓ，２１ -τ ｔｒｕｅ　　　　 (4) The transmission timing control unit 34 calculates the synchronization deviation time Δτ ｅｒｒ That is, the transmission timing control unit 34 controls the transmission timing of the transmission signal transmitted from the slave radar device 2-m based on the synchronization deviation time Δτｅｒｒ If the sign of is positive, the transmission time of the transmission signal transmitted from the slave radar device 2-m is later than the transmission time of the transmission signal transmitted from the master radar device 1 by a synchronization deviation time Δτ ｅｒｒ The transmission timing control unit 34 controls the time at which the signal oscillator 21 of the slave radar device 2-m oscillates the transmission signal so that the time is delayed by the synchronization deviation time Δτ ｅｒｒ If the sign of is negative, the transmission time of the transmission signal transmitted from the slave radar device 2-m is delayed by a synchronization deviation time Δτ from the transmission time of the transmission signal transmitted from the master radar device 1. ｅｒｒ The time at which the signal oscillator 21 of the slave radar device 2-m oscillates the transmission signal is controlled so that the radar advances by only 100ms.

[0039] After the calibration process is completed, during radar operation, the receiving antenna 14 of the master radar device 1 receives reflected waves of the transmission signal that are radiated from the transmitting antenna 13 and then reflected by a target or the like, and outputs the received signal of the reflected waves to the receiving unit 15. The receiving unit 15 demodulates the received signal output from the receiving antenna 14, and outputs the demodulated received signal to the received signal output unit 16. The received signal output unit 16 outputs the demodulated received signal to the distributed radar processing unit 60.

[0040] During radar operation, the receiving antenna 24 of the slave radar device 2-m receives reflected waves of the transmission signal that have been radiated from the transmitting antenna 23 and then reflected by a target or the like, and outputs the received signal of the reflected waves to the receiving unit 25. The receiving unit 25 demodulates the received signal output from the receiving antenna 24 and outputs the demodulated received signal to the received signal output unit 35. The received signal output unit 35 outputs the demodulated received signal to the distributed radar processing unit 60. The distributed radar processing unit 60 acquires demodulated received signals from the master radar device 1 and the M slave radar devices 2-1 to 2-M. The distributed radar processing unit 60 combines the multiple received signals and outputs the combined received signal to a target detection unit or the like (not shown).

[0041] In the first embodiment described above, when a transmission signal is transmitted from the master radar device 1 and a reflected wave of the transmission signal reflected by a target whose position is known is received by a slave radar device 2-m (m = 1, ..., M), the synchronization establishment device 26 is configured to include a received signal acquisition unit 31 that acquires the received signal of the reflected wave, a first propagation delay time calculation unit 32 that calculates a first propagation delay time, which is the propagation delay time of the reflected wave, based on the received signal acquired by the received signal acquisition unit 31, and a second propagation delay time calculation unit 33 that calculates a second propagation delay time, which is the true propagation delay time of the reflected wave, from the position of the target and the position of the slave radar device 2-m. The synchronization establishment device 26 also includes a transmission timing control unit 34 that controls the transmission timing of the transmission signal transmitted from the slave radar device 2-m based on the first propagation delay time calculated by the first propagation delay time calculation unit 32 and the second propagation delay time calculated by the second propagation delay time calculation unit 33. Therefore, the synchronization establishment device 26 can synchronize the master radar device 1 and the slave radar device 2-m without connecting the master radar device 1 and the slave radar device 2-m with a synchronization signal line.

[0042] Embodiment 2. The distributed radar system shown in FIG. 1 includes a master radar device 1 and slave radar devices 2-1 to 2-M. However, this is merely an example, and the distributed radar system may include receive-only radar devices 3-1 to 3-N in addition to the master radar device 1 and slave radar devices 2-1 to 2-M, as shown in FIG. 7, where N is an integer equal to or greater than 1. FIG. 7 is a configuration diagram showing a distributed radar system according to embodiment 2. In FIG. 7, the same reference numerals as in FIG. 1 indicate the same or equivalent parts, and detailed description thereof will be omitted. The receive-only radar devices 3-n (n = 1, ..., N) include a receiving antenna 24, a receiving unit 25, and a received signal output unit 35, but do not include a signal oscillator 21, a transmitting unit 22, a transmitting antenna 23, or a synchronization establishment device 26. In the receive-only radar device 3-n, when a transmission signal is transmitted from either the master radar device 1 or the slave radar device 2-m (m = 1, ..., M), the receiving antenna 24 receives the reflected wave of the transmission signal reflected by the target. The receiving unit 25 demodulates the received signal of the reflected wave using a signal equivalent to the transmission signal.

[0043] In this case, the modulation methods of the transmission signals transmitted from the master radar device 1 and each of the M slave radar devices 2-1 to 2-M may be different from one another, as shown in FIG. 8 . Examples of different modulation methods include a modulation method capable of time-division multiple-input multiple-output (MIMO), a modulation method capable of frequency-division MIMO, or a modulation method capable of code-division MIMO. FIG. 8 is a configuration diagram showing another distributed radar system according to embodiment 2. In FIG. 8 , the same reference numerals as in FIG. 7 indicate the same or equivalent parts, and detailed description thereof will be omitted. In FIG. 8 , the modulation methods are different between transmission signals that are neither hatched nor shaded, transmission signals that are hatched, and transmission signals that are shaded.

[0044] FIG. 9 is a configuration diagram showing another distributed radar system according to embodiment 2. In FIG. 9, the same reference numerals as those in FIGS. 7 and 8 indicate the same or corresponding parts, and detailed description thereof will be omitted. In the distributed radar system shown in FIG. 9, the master radar device 1 and the slave radar device 2-m (m = 1, ..., M) each receive only the reflected waves of the transmission signals transmitted by themselves. The receive-only radar device 3-n (n = 1, ..., N) receives the reflected waves of the transmission signals transmitted from the master radar device 1 and the slave radar device 2-m (m = 1, ..., M), respectively. In FIG. 9, the modulation methods of the transmission signals that are neither hatched nor shaded, the hatched transmission signals, and the shaded transmission signals are different from one another.

[0045] In the first and second embodiments, the received signal output units 16 and 35 output the demodulated received signals to the distributed radar processing unit 60. At this time, the received signal output units 16 and 35 may output the demodulated received signals to the distributed radar processing unit 60 via a wired signal line, or may output the demodulated received signals to the distributed radar processing unit 60 via a wireless line.

[0046] In addition, the present disclosure allows for free combination of the respective embodiments, modification of any of the components of the respective embodiments, or omission of any of the components of the respective embodiments.

[0047] The present disclosure is suitable for a synchronization establishment device, a synchronization establishment method, and a distributed radar system.

[0048] 1 Master radar device, 2-1 to 2-M Slave radar devices, 3-1 to 3-N Receive-only radar devices, 11 Signal oscillator, 12 Transmitter, 13 Transmitting antenna, 14 Receiving antenna, 15 Receiving unit, 16 Received signal output unit, 21 Signal oscillator, 22 Transmitter, 23 Transmitting antenna, 24 Receiving antenna, 25 Receiving unit, 26 Synchronization establishment device, 31 Received signal acquisition unit, 32 First propagation delay time calculation unit, 33 Second propagation delay time calculation unit, 34 Transmission timing control unit, 35 Received signal output unit, 41 Received signal acquisition circuit, 42 First propagation delay time calculation circuit, 43 Second propagation delay time calculation circuit, 44 Transmission timing control circuit, 51 Memory, 52 Processor, 60 Distributed radar processing unit.

Claims

1. A synchronization establishment device comprising: a received signal acquisition unit that acquires a received signal of a reflected wave when a transmission signal is transmitted from a master radar device and the reflected wave of the transmission signal reflected by a target whose position is known is received by a slave radar device; a first propagation delay time calculation unit that calculates a first propagation delay time, which is the propagation delay time of the reflected wave, based on the received signal acquired by the received signal acquisition unit; a second propagation delay time calculation unit that calculates a second propagation delay time from the position of the target and the position of the slave radar device as the true propagation delay time of the reflected wave; and a transmission timing control unit that controls the transmission timing of a transmission signal transmitted from the slave radar device based on the first propagation delay time calculated by the first propagation delay time calculation unit and the second propagation delay time calculated by the second propagation delay time calculation unit.

2. The synchronization establishment device described in claim 1, characterized in that the transmission timing control unit calculates the difference between the first propagation delay time calculated by the first propagation delay time calculation unit and the second propagation delay time calculated by the second propagation delay time calculation unit as a synchronization deviation time, and controls the transmission timing of the transmission signal transmitted from the slave radar device based on the synchronization deviation time.

3. A synchronization establishment method in which, when a transmission signal is transmitted from a master radar device and a reflected wave of the transmission signal reflected by a target whose position is known is received by a slave radar device, a received signal acquisition unit acquires a received signal of the reflected wave, a first propagation delay time calculation unit calculates a first propagation delay time which is the propagation delay time of the reflected wave based on the received signal acquired by the received signal acquisition unit, a second propagation delay time calculation unit calculates a second propagation delay time from the position of the target and the position of the slave radar device as the true propagation delay time of the reflected wave, and a transmission timing control unit controls the transmission timing of the transmission signal to be transmitted from the slave radar device based on the first propagation delay time calculated by the first propagation delay time calculation unit and the second propagation delay time calculated by the second propagation delay time calculation unit.

4. A distributed radar system comprising a master radar device and a slave radar device, wherein the slave radar device comprises: a received signal acquisition unit that acquires a received signal of a reflected wave when a transmission signal is transmitted from the master radar device and the reflected wave of the transmission signal reflected by a target whose position is known is received by the slave radar device; a first propagation delay time calculation unit that calculates a first propagation delay time, which is the propagation delay time of the reflected wave, based on the received signal acquired by the received signal acquisition unit; a second propagation delay time calculation unit that calculates a second propagation delay time from the position of the target and the position of the slave radar device as the true propagation delay time of the reflected wave; and a transmission timing control unit that controls the transmission timing of a transmission signal transmitted from the slave radar device based on the first propagation delay time calculated by the first propagation delay time calculation unit and the second propagation delay time calculated by the second propagation delay time calculation unit.

5. The distributed radar system according to claim 4, characterized in that each of the master radar device and the slave radar device is provided with a received signal output unit that outputs a received signal of a reflected wave received by a receiving antenna, and is provided with a distributed radar processing unit that combines the received signals output from the multiple received signal output units.

6. A distributed radar system as described in claim 4, characterized in that the multiple radar devices include one or more master radar devices and one or more slave radar devices, and the modulation methods of the transmission signals sent from the multiple radar devices are different from each other.

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