UWB Time Synchronization System, Method and Device Based on Unidirectional Broadcast Mode

Abstract

The present application relates to a UWB time synchronization system, method and device based on a unidirectional broadcast mode. The system includes: a reference node and slave nodes, where the reference node and the slave nodes include a chip atomic clock, a frequency synthesizer, a UWB radio frequency chip and a main controller; the main controller of the reference node is used to control the UWB radio frequency chip to generate broadcast data with a reference timestamp according to the 1PPS signal output by the chip atomic clock, and the UWB radio frequency chip sends the broadcast data to the slave nodes; the UWB radio frequency chip of the slave nodes receives the broadcast data and sends the received timestamp and the reference timestamp to the main controller of the slave nodes, and the main controller calculates the frequency difference according to the accumulated received timestamp and the reference timestamp, performs PID dynamic calibration on the frequency of the chip atomic clock of the slave nodes according to the frequency difference, and calculates and calibrates the time difference according to the received timestamp and the transmitted timestamp. Using this system can improve the reliability and persistence of time synchronization.

Description

Technical Field

[0001] This application relates to the field of wireless communication technologies, and particularly to a UWB time synchronization system, method, and apparatus based on a one-way broadcast mode. Background Art

[0002] Time synchronization technology plays a crucial role in modern distributed systems and Internet of Things applications, and is widely used in fields such as wireless sensor networks, drone swarms, intelligent manufacturing, and intelligent transportation. Current time synchronization methods are mainly divided into methods based on wireless communication protocols (such as Bluetooth, Wi-Fi, Zigbee, etc.) and high-precision time synchronization technologies relying on satellite navigation systems.

[0003] In the Bluetooth-based time synchronization scheme, time stamps are usually transmitted and aligned using Bluetooth periodic two-way communication signals. This scheme generally can achieve a synchronization accuracy of 10 to 100 microseconds, but the accuracy may be affected by factors such as channel delay and transmission interval. Through protocol improvement or the addition of time stamp correction technology, the highest accuracy of Bluetooth synchronization is 10 microseconds.

[0004] Wi-Fi time synchronization methods include time synchronization schemes based on the IEEE 802.11 protocol and time stamp mutual transmission mechanisms based on the MAC layer. Compared with Bluetooth, Wi-Fi time synchronization has higher accuracy, generally being able to achieve an accuracy of 1 to 10 microseconds. In a local network, through precise time stamp recording and a high-frequency correction mechanism, the accuracy of Wi-Fi time synchronization can reach the sub-microsecond level.

[0005] High-precision time synchronization methods based on satellite navigation systems (such as GPS, GLONASS, Beidou, etc.) are widely used in distributed systems with extremely high accuracy requirements. This method uses high-precision clocks on satellites to provide Universal Time Coordinated (UTC) signals. Ground devices achieve nanosecond-level time synchronization by receiving time stamp information from multiple satellites and eliminating signal propagation delays. Although atmospheric interference and multipath effects may affect the reception accuracy, through time correction and anti-interference algorithms, reliable high-precision synchronization can still be ensured, making it suitable for scenarios that require strict synchronization such as power systems, communication base stations, and financial systems. However, in indoor, underground, and other denied environments, due to the loss or interference of external signals, time synchronization and communication coordination between devices become extremely difficult. This is particularly critical for distributed systems, especially in application scenarios with strict requirements for time synchronization accuracy (such as drone swarm collaboration, intelligent transportation), which will lead to a decline in the efficiency and reliability of the collaborative system. Summary of the Invention

[0006] Based on this, it is necessary to provide a UWB time synchronization system, method, and device based on a unidirectional broadcast mode to address the technical issues such as inapplicability in the above-mentioned denial environment, too low time synchronization accuracy, and resource consumption in two-way communication.

[0007] A UWB time synchronization system based on a unidirectional broadcast mode, the system includes:

[0008] A reference node and a slave node, the reference node and the slave node include a chip atomic clock, a frequency synthesizer, a UWB RF chip, and a main controller; the main controller is respectively connected to the chip atomic clock and the UWB RF chip;

[0009] The UWB RF chip is connected to the chip atomic clock;

[0010] The frequency synthesizer is respectively connected to the chip atomic clock and the UWB RF chip, and is used to convert the 10 MHz signal provided by the chip atomic clock into the standard time signal of the UWB RF chip;

[0011] On the reference node, the main controller of the reference node controls the UWB RF chip to generate broadcast data with a reference timestamp according to the 1PPS signal output by the chip atomic clock, and the UWB RF chip sends the broadcast data to the slave node;

[0012] On the slave node, the UWB RF chip of the slave node receives the broadcast data and sends the received timestamp and the reference timestamp to the main controller of the slave node, is triggered according to the 1PPS signal output by the chip atomic clock, sends an empty data packet and sends the transmission timestamp to the main controller of the slave node, the main controller calculates the frequency difference according to the cumulative received timestamp and the reference timestamp, performs PID dynamic calibration on the frequency of the chip atomic clock of the slave node according to the frequency difference, calculates the time difference according to the received timestamp and the transmission timestamp and calibrates it to achieve time synchronization.

[0013] A UWB time synchronization method based on a unidirectional broadcast mode, the method includes:

[0014] Generate broadcast data with a reference timestamp through the reference node and send it to the slave node;

[0015] Receive the broadcast data through the slave node and extract the reference timestamp, send an empty data packet, calculate the frequency difference according to the cumulative received timestamp and the reference timestamp, perform PID dynamic calibration on the frequency of the chip atomic clock of the slave node according to the frequency difference, calculate the time difference according to the received timestamp and the transmission timestamp and calibrate it to achieve time synchronization.

[0016] A UWB time synchronization device based on a unidirectional broadcast mode, the device includes:

[0017] Chip atomic clock, frequency synthesizer, UWB radio frequency chip and main controller;

[0018] The chip atomic clock is used to provide a time reference signal to the frequency synthesizer and the main controller; the time reference signal includes a 10 MHz signal and a 1PPS signal;

[0019] The frequency synthesizer is used to convert the 10 MHz signal into a standard time signal and send it to the UWB radio frequency chip;

[0020] The UWB radio frequency chip uses the standard time signal as the operating frequency source, and is used to send broadcast data to the child nodes when the device is used as a reference node, and is used to receive broadcast data and send the received timestamp and the reference timestamp to the main controller when the device is used as a child node. At the same time, an empty data packet is sent and the transmission timestamp is obtained and sent to the main controller;

[0021] The main controller is used to control the UWB radio frequency chip to generate broadcast data with a reference timestamp and transmit it to the child nodes according to the 1PPS signal when the device is used as a reference node, and is used to calculate the frequency difference according to the cumulative received timestamp and the reference timestamp when the device is used as a child node. The frequency of the chip atomic clock of the child node is dynamically calibrated by PID, and the time difference is calculated and calibrated according to the received timestamp and the transmitted timestamp to achieve time synchronization.

[0022] The above UWB time synchronization system, method and device based on the one-way broadcast mode provide a highly stable time reference signal through the chip atomic clock, the frequency synthesizer ensures the reliability of UWB communication, the reference node sends timestamps through one-way broadcast, and there is no need for the child nodes to respond, reducing communication conflicts. And by using the high-frequency bandwidth characteristics of UWB, the anti-interference ability is enhanced, efficient and conflict-free time synchronization is achieved in a multi-node scenario, adapting to the communication requirements of complex environments, with strong scalability. The UWB radio frequency chip of the child node receives the broadcast timestamp of the reference node, records the received timestamp at the same time, generates and sends an empty data packet through the trigger signal output by its own chip atomic clock, records the transmission timestamp at the same time, calculates the frequency difference according to the received timestamp and the reference timestamp, and dynamically adjusts the frequency of the chip atomic clock through PID control to eliminate the cumulative error in real time. Calculate the time difference according to the received timestamp and the transmitted timestamp, and use the precise clock reference after frequency difference calibration to fine-tune its own time reference according to the phase calibration mechanism to eliminate the phase deviation, so as to achieve high-precision synchronization under long-term operation, avoid inaccuracy caused by error accumulation, and improve the reliability and persistence of time synchronization. Through the careful system operation logic, ensure the efficient and stable operation of the system. The embodiment of the present invention can achieve nanosecond-level time synchronization, providing a reliable guarantee for applications with strict time requirements (such as drone swarm collaboration and intelligent transportation). Description of the Drawings

[0023] Figure 1 It is a structural block diagram of a UWB time synchronization system based on a unidirectional broadcast mode in an embodiment;

[0024] Figure 2 It is a schematic diagram of the communication process between a reference node and a child node in an embodiment;

[0025] Figure 3 It is a schematic diagram of the overall operation logic of the system in an embodiment;

[0026] Figure 4 It is a schematic diagram of the actual operation result of the UWB time synchronization system in an embodiment;

[0027] Figure 5 It is a structural block diagram of a UWB time synchronization device based on a unidirectional broadcast mode in an embodiment. Detailed implementation manners

[0028] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] In one embodiment, as Figure 1 shown, a UWB time synchronization system based on a unidirectional broadcast mode is provided, including:

[0030] A reference node and child nodes, where the reference node and the child nodes include a chip atomic clock, a frequency synthesizer, a UWB radio frequency chip and a main controller; the main controller is respectively connected to the chip atomic clock and the UWB radio frequency chip; the UWB radio frequency chip is connected to the chip atomic clock;

[0031] The frequency synthesizer is respectively connected to the chip atomic clock and the UWB radio frequency chip, and is used to convert the 10 MHz signal provided by the chip atomic clock into a standard time signal of the UWB radio frequency chip;

[0032] On the reference node, the main controller of the reference node controls the UWB radio frequency chip to generate broadcast data with a reference timestamp according to the 1PPS signal output by the chip atomic clock, and the UWB radio frequency chip sends the broadcast data to the child nodes;

[0033] On the child node, the UWB RF chip of the child node receives broadcast data and sends the received timestamp and the reference timestamp to the main controller of the child node. It is triggered according to the 1PPS signal output by the chip atomic clock, sends an empty data packet and sends the transmission timestamp to the main controller of the child node. The main controller calculates the frequency difference based on the cumulative received timestamp and the reference timestamp, performs PID dynamic calibration on the frequency of the chip atomic clock of the child node according to the frequency difference, calculates and calibrates the time difference based on the received timestamp and the transmission timestamp, and realizes time synchronization.

[0034] In this embodiment, the chip atomic clock is responsible for providing a stable time reference signal, including 10 MHz and 1 PPS (pulses per second) signals. Among them, the 1 PPS signal provides a tick signal per second for the main controller to ensure the basic time scale of the system. The 10 MHz signal is converted into 38.4 MHz via a frequency synthesizer and used as the operating frequency source of the UWB RF chip to meet the frequency requirements of the UWB chip.

[0035] During the operation of the system, the UWB RF chip generates an interruption when sending or receiving a broadcast signal, and transmits the corresponding transmission timestamp or received timestamp to the main controller through SPI (Serial Peripheral Interface). The main controller performs calculations based on the received timestamp, calculates the time offset of the system, and adjusts the time synchronization accuracy of the device in real time. Subsequently, the main controller feeds back the calculation result to the chip atomic clock through the RS232 interface to calibrate its frequency and realize the closed-loop control of the hardware solution.

[0036] In the above UWB time synchronization method based on the unidirectional broadcast mode, a high-stability time reference signal is provided by a chip atomic clock, and a frequency synthesizer ensures the reliability of UWB communication. The reference node sends a timestamp through unidirectional broadcast without requiring the slave nodes to respond, reducing communication conflicts. Moreover, by utilizing the high-frequency bandwidth characteristics of UWB, the anti-interference ability is enhanced, enabling efficient and conflict-free time synchronization in a multi-node scenario, adapting to the communication requirements of complex environments, and having strong scalability. The UWB RF chip of the slave node receives the broadcast timestamp of the reference node and records the reception timestamp simultaneously. Through the trigger signal output by its own chip atomic clock, it generates and sends an empty data packet, and records the transmission timestamp at the same time. The frequency difference is calculated based on the reception timestamp and the reference timestamp, and the frequency of the chip atomic clock is dynamically adjusted through PID control to eliminate the cumulative error in real time. The time difference is calculated based on the reception timestamp and the transmission timestamp, and the precise clock reference after frequency difference calibration is used to fine-tune its own time reference according to the phase calibration mechanism to eliminate the phase deviation, thereby achieving high-precision synchronization during long-term operation, avoiding inaccuracy caused by error accumulation, and improving the reliability and persistence of time synchronization. Through a rigorous system operation logic, the efficient and stable operation of the system is ensured. In the embodiment of the present invention, nanosecond-level time synchronization can be achieved, providing a reliable guarantee for applications with strict time requirements (such as drone swarm collaboration and intelligent transportation).

[0037] In one embodiment, the frequency difference is calculated based on the cumulative reception timestamp and the reference timestamp, and the frequency of the chip atomic clock of the slave node is dynamically calibrated by PID according to the frequency difference, including: calculating the reception time interval between two broadcasts based on the reception timestamp of the received broadcast data, calculating the reference time interval of the corresponding two reference timestamps, and calculating the frequency error ratio based on the reception time interval and the reference time interval; calculating the frequency difference according to the frequency error ratio, and dynamically calibrating the frequency of the chip atomic clock of the slave node by PID according to the frequency difference; calculating and calibrating the time difference based on the reception timestamp and the transmission timestamp, including: calculating the time difference between nodes based on the reception timestamp of the received broadcast data and the transmission timestamp of the sent empty data packet; extracting the phase offset of the slave node according to the time difference, and performing phase calibration by adjusting the phase offset.

[0038] Specifically, the node communication process is as Figure 2 shown. The slave node calculates the ratio of frequencies through the broadcast data of the reference node twice, estimating the error of its local clock frequency relative to the clock frequency of the reference node, as shown in formula (1).

[0039] (1)

[0040] Where represents the reference node frequency, represents the frequency of this node, represents the The timestamp of the reference node's broadcast packet at a moment, indicating the timestamp when the child node receives the broadcast moment of the reference node. From this, the time difference between nodes can be calculated, as shown in formula (2).

[0041] (2)

[0042] Among them, indicating the timestamp when the child node sends an empty data packet. After obtaining the clock time difference and frequency difference data, the chip atomic clock can be dynamically calibrated through the PID. The calibration formula is as shown in formula (3).

[0043] (3)

[0044] Among them represents the clock parameter to be adjusted, is the proportional gain, which generates a correction amount for the current time difference , is the integral gain, which integrates the cumulative error over past time to eliminate the continuous deviation existing during long-term operation, is the differential gain, which is adjusted according to the rate of change of the time error (i.e., the derivative of the error). The differential term can predict the change trend of the error, enabling the system to make adjustments in advance when the error changes rapidly and avoiding large offsets.

[0045] In one embodiment, the chip atomic clock is used to provide a time reference signal for the frequency synthesizer and the main controller; the time reference signal includes a 10 MHz signal and a 1 PPS signal.

[0046] In one embodiment, the standard time signal of the UWB radio frequency chip is a 38.4 MHz signal.

[0047] In one embodiment, the system further includes: after power-on, the chip atomic clock, frequency synthesizer, and UWB radio frequency chip of the reference node and child node are initialized in sequence.

[0048] The overall operation logic of the system is as Figure 3As shown. After the device starts up, it first executes the initialization process. To ensure the accurate startup of the time signal, during initialization, the chip atomic clock, frequency synthesizer, and UWB RF chip are activated in sequence to ensure the unified time reference among modules. After initialization is completed, the device will detect whether it is a reference node. The main function of the reference node is to periodically send broadcast data with accurate timestamps for other child nodes to synchronize. After receiving the timestamp from the reference node, the child node calculates the deviation between its own time and the reference time by sending an empty data packet triggered by PPS, and compensates and calibrates accordingly to achieve accurate time synchronization.

[0049] Specifically, the left process describes the initialization of the hardware module to ensure that the system has working conditions. The system detects whether the device has completed power-on startup. After power-on, the chip atomic clock is initialized. If the initialization fails, the system needs to retry. After the chip atomic clock is successfully initialized, similarly, the frequency synthesizer and UWB RF chip are initialized in sequence. After successful initialization, the system enters the running state. The 1PPS (Pulse Per Second signal) of the system is used to trigger the clock reset of the UWB RF chip to ensure the consistency of the time synchronization reference of the module. The right process details how the reference node and child nodes complete broadcasting, listening, time calibration, and frequency calibration during operation, forming a complete time synchronization closed-loop system. The reference node broadcasts the timestamp according to the PPS signal triggered per second and ensures the reliability of the broadcast through anti-collision calculation; the child node listens to the broadcast information, and after receiving the timestamp from the reference node, confirms the data validity by sending a receipt message. Subsequently, the child node is triggered by the PPS signal to actively send an empty data packet, and uses the received timestamp and its own sending timestamp to dynamically calibrate the frequency error of the chip atomic clock through a PID controller, and finally performs phase difference calibration to ensure high-precision time synchronization with the reference node. The whole process runs in a loop to achieve continuous synchronization and dynamic adjustment of the system.

[0050] In a specific embodiment, a UWB time synchronization system is built according to the time synchronization system architecture of the present invention. The clock oscillator uses SA.45s, which outputs a 10 MHz signal and a 1 PPS signal. The short-term stability within a 1 s average period is 2.5 10 -10 , and the long-term aging is less than 9 10 -10 , and the maximum frequency change within the temperature range of -10 to 35 degrees Celsius is 5 10 -10It can perform digital servo adjustment through a serial interface. The frequency synthesizer uses the LMX2571 with low jitter characteristics to convert the 10 MHz clock signal into the 38.4 MHz signal required by the UWB module. The UWB module uses the DW1000 chip, which is an integrated UWB signal transceiver chip with ultra-wideband, low power consumption, and low cost, and has high-precision ranging and data transmission capabilities. It can extract the timestamp of the arrival time of data packets at a resolution of 15.6 ps, and the measurement accuracy is better than 10 cm. The main processor uses the Kinetis K22F, which is a high-performance, low-power microcontroller based on the ARM Cortex-M4 core, with an operating frequency of 120 MHz, 512 KB Flash, and 128 KB SRAM, supports rich peripheral interfaces such as USB, UART, SPI, and I2C, and has built-in hardware encryption and analog signal processing functions.

[0051] The present invention conducts experiments on the built UWB time synchronization system. A UWB time synchronization system is built using 5 nodes. Each node broadcasts its current timestamp to adjacent nodes, and the node compensates according to the obtained time difference. The node time slot is 1 s, the parameter sampling period is 1 s, and 300 samplings are performed. The experiment checks the clock synchronization effect by measuring the 1PPS output signal of the atomic clock of each node. As Figure 4 This is the time difference between each node and Node 1. It can be seen from the results that after about 100 synchronizations, each node achieves time synchronization, the time difference tends to be stable relative to the reference Node 1, and the time difference range is less than 8 ns, meeting the requirements of nanosecond-level time synchronization.

[0052] Through the combination of hardware and software algorithms, the present invention realizes high-precision time synchronization at the nanosecond level and is applicable to distributed systems in indoor and other denied environments. Compared with the limited accuracy of traditional time synchronization methods in environments such as indoors where signals are blocked or severely interfered, the present invention can achieve stable time synchronization in these environments. At the same time, compared with other synchronization methods in denied environments, the present invention can achieve high-precision nanosecond-level synchronization. By using the precise time base signal provided by the chip atomic clock, combined with the characteristics of the UWB high-frequency bandwidth and the PID dynamic calibration algorithm, the system can achieve nanosecond-level time synchronization. This high precision provides a reliable guarantee for applications with strict time requirements. In addition, by using the PID control algorithm, the system can dynamically adjust the chip atomic clock according to the current time deviation and historical deviation. This mechanism ensures that the system can compensate for time offset and frequency drift at any time and maintain long-term synchronization accuracy. Compared with other two-way communication time synchronization systems, the present invention reduces communication resource consumption and obtains the same synchronization performance as the two-way communication system through a careful transceiver logic.

[0053] In one embodiment, a UWB time synchronization method based on the unidirectional broadcast mode is provided. The specific steps include:

[0054] The reference node generates broadcast data with a reference timestamp and sends it to the child nodes;

[0055] The child nodes receive the broadcast data, extract the reference timestamp, send empty data packets, calculate the frequency difference based on the cumulative received timestamp and the reference timestamp, perform PID dynamic calibration on the chip atomic clock frequency of the child nodes according to the frequency difference, calculate the time difference based on the received timestamp and the sent timestamp, and perform calibration to achieve time synchronization.

[0056] In one embodiment, as Figure 5 shown, a UWB time synchronization device based on the unidirectional broadcast mode is provided, including: a chip atomic clock, a frequency synthesizer, a UWB radio frequency chip, and a main controller;

[0057] The chip atomic clock is used to provide a time reference signal to the frequency synthesizer and the main controller; the time reference signal includes a 10 MHz signal and a 1PPS signal;

[0058] The frequency synthesizer is used to convert the 10 MHz signal into a standard time signal and send it to the UWB radio frequency chip;

[0059] The UWB radio frequency chip uses the standard time signal as the operating frequency source, is used to send broadcast data to the child nodes when the device is a reference node, and is used to receive broadcast data and send the received timestamp and the reference timestamp to the main controller when the device is a child node, and at the same time send empty data packets and obtain the sent timestamp and send it to the main controller;

[0060] The main controller is used to control the UWB radio frequency chip to generate broadcast data with a reference timestamp and transmit it to the child nodes according to the 1PPS signal when the device is a reference node, and is used to calculate the frequency difference according to the cumulative received timestamp and the reference timestamp when the device is a child node, perform PID dynamic calibration on the chip atomic clock frequency of the child nodes according to the frequency difference, calculate the time difference according to the received timestamp and the sent timestamp, and perform calibration to achieve time synchronization.

[0061] For the specific limitations of the UWB time synchronization device based on the unidirectional broadcast mode, reference can be made to the limitations of the UWB time synchronization system based on the unidirectional broadcast mode in the above text, which will not be elaborated here. Each module in the above UWB time synchronization device based on the unidirectional broadcast mode can be implemented in whole or in part through software, hardware, and their combination. The above modules can be embedded in or independent of the processor in the computer device in hardware form, or stored in the memory in the computer device in software form, so that the processor can call and execute the operations corresponding to the above modules.

[0062] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0063] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A UWB time synchronization system based on a one-way broadcast mode, characterized in that: The system includes a reference node and a subnode, wherein the reference node and the subnode include a chip atomic clock, a frequency synthesizer, a UWB radio frequency chip and a main controller; the main controller is respectively connected to the chip atomic clock and the UWB radio frequency chip; the UWB radio frequency chip is connected to the chip atomic clock; The frequency synthesizer is connected to the chip atomic clock and the UWB radio frequency chip respectively, and is used to convert the 10 MHz signal provided by the chip atomic clock into a standard time signal of the UWB radio frequency chip; On the reference node, the main controller of the reference node controls the UWB radio chip to generate broadcast data with a reference timestamp according to the 1PPS signal output by the chip atomic clock, and the UWB radio chip sends the broadcast data to the child node; On the child node, the UWB RF chip of the child node receives the broadcast data and sends the receiving timestamp and the reference timestamp to the main controller of the child node. It is triggered by the 1PPS signal output by the chip atomic clock, sends an empty data packet and sends the sending timestamp to the main controller of the child node. The main controller calculates the frequency difference based on the accumulated receiving timestamps and the reference timestamps, performs PID dynamic calibration on the chip atomic clock frequency of the child node based on the frequency difference, calculates and calibrates the time difference based on the receiving timestamp and the sending timestamp to achieve time synchronization.

2. The system according to claim 1, characterized in that The frequency difference is calculated based on the accumulated receiving timestamp and the reference timestamp, and the PID dynamic calibration of the chip atomic clock frequency of the child node is performed based on the frequency difference, including: Calculate the receiving time interval between two broadcasts according to the receiving timestamp of the received broadcast data, calculate the reference time interval between the two corresponding reference timestamps, and calculate the frequency error ratio according to the receiving time interval and the reference time interval; The frequency difference is calculated according to the frequency error ratio, and the PID dynamic calibration of the chip atomic clock frequency of the sub-node is performed according to the frequency difference.

3. The system according to claim 1, characterized in that Calculate the time difference and calibrate based on the receiving timestamp and sending timestamp, including: The time difference between nodes is calculated based on the receiving timestamp of the received broadcast data and the sending timestamp of the sent empty data packet; The phase offset of the subnode is extracted according to the time difference, and the phase calibration is performed by adjusting the phase offset.

4. The system according to claim 1, characterized in that The system further comprises: After power-on, the chip atomic clock, frequency synthesizer and UWB radio frequency chip of the reference node and sub-node are initialized in turn.

5. The system according to claim 1, characterized in that The chip atomic clock is used to provide a time reference signal to a frequency synthesizer and a main controller; the time reference signal includes a 10 MHz signal and a 1 PPS signal.

6. The system according to claim 1, characterized in that The standard time signal of the UWB radio frequency chip is a 38.4 MHz signal.

7. A UWB time synchronization method implemented in a UWB time synchronization system based on a unidirectional broadcast mode as claimed in any one of claims 1 to 6, characterized in that: The method comprises: Generate broadcast data with reference timestamp through reference node and send it to child nodes; The sub-node receives the broadcast data and extracts the reference timestamp, sends an empty data packet, calculates the frequency difference based on the accumulated received timestamp and the reference timestamp, performs PID dynamic calibration on the chip atomic clock frequency of the sub-node based on the frequency difference, calculates and calibrates the time difference based on the received timestamp and the sent timestamp, and realizes time synchronization.

8. A UWB time synchronization device of a UWB time synchronization system based on a unidirectional broadcast mode, characterized in that: The device includes a chip atomic clock, a frequency synthesizer, a UWB radio frequency chip and a main controller; The chip atomic clock is used to provide a time reference signal to the frequency synthesizer and the main controller; the time reference signal includes a 10 MHz signal and a 1PPS signal; The frequency synthesizer is used to convert the 10 MHz signal into a standard time signal and send it to the UWB radio frequency chip; The UWB radio frequency chip uses the standard time signal as the working frequency source, is used to send broadcast data to the child node when the device is used as a reference node, and is used to receive broadcast data and send the receiving timestamp and the reference timestamp to the main controller when the device is used as a child node, and send an empty data packet and obtain the sending timestamp and send it to the main controller at the same time; The main controller is used to control the UWB radio frequency chip to generate broadcast data with a reference timestamp and transmit it to the child node according to the 1PPS signal when the device acts as a reference node, and is used to calculate the frequency difference according to the accumulated reception timestamp and the reference timestamp when the device acts as a child node, perform PID dynamic calibration on the chip atomic clock frequency of the child node according to the frequency difference, calculate and calibrate the time difference according to the reception timestamp and the transmission timestamp, and realize time synchronization.

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