High-precision timekeeping and network time synchronization system based on Beidou signal and its method

Abstract

The present invention relates to a high-precision timekeeping and network time synchronization system and method based on Beidou signals. The system includes: a BeiDou-3 antenna module for receiving and filtering electromagnetic wave signals of each frequency point of BeiDou-3 and outputting radio frequency signals; a BeiDou-3 signal processing module for receiving the radio frequency signals output by the BeiDou-3 antenna module, processing them, completing input capture, PVT solution, data analysis and storage of BeiDou-3 signals, and outputting BeiDou time information, where the BeiDou time information includes TOD and 1PPS time information; a rubidium atomic clock timekeeping module for receiving the TOD and 1PPS time information output by the BeiDou-3 signal processing module, performing timekeeping operations, and outputting the accumulated standard TOD time information and high-precision 1PPS edge; a network time synchronization module for receiving the TOD time information and high-precision 1PPS edge information output by the rubidium atomic clock timekeeping module and performing network time synchronization; and a power supply module. The system and method of the present invention can be used for high-precision timekeeping and network time synchronization.

Description

Technical Field

[0001] The present invention relates to the field of Beidou-3 satellite time service, and more specifically, to a high-precision timekeeping and network time service system and method based on Beidou-3 signals. Background Art

[0002] With the completion of the global deployment of Beidou-3 satellites, the high-precision time characteristics of the Beidou-3 satellite system have become a major highlight. However, how to make full use of this feature of Beidou-3 satellites in various industries has become an issue that everyone is thinking about.

[0003] Currently, Beidou receivers on the market can only achieve real-time positioning and timing of Beidou. However, when the Beidou signal is blocked, the time will deviate. Network time devices on the market often do not meet the expected time accuracy requirements because they do not have a high-precision time source.

[0004] How to make good use of the high-precision time of the Beidou-3 satellite system to achieve high-precision timekeeping and network time service has become an urgent problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to combine the reception of Beidou-3 (also known as "BeiSan") satellite signals, the timekeeping of the ground system, and the current common network time system, introduce Beidou time into the network system, and make it continuously available with high precision for a long time, forming a high-precision time system integrating time service, timekeeping, and network time dissemination, to meet the needs of various industries for a continuous high-precision time system.

[0006] To solve the above technical problems, according to one aspect of the present invention, a high-precision timekeeping and network time synchronization system based on Beidou signals is provided, which includes: a BeiDou-3 antenna module for receiving and filtering electromagnetic wave signals of each frequency point of BeiDou-3 and outputting a radio frequency signal; a BeiDou-3 signal processing module connected to the BeiDou-3 antenna module, receiving the radio frequency signal output by the BeiDou-3 antenna module, processing it, completing the input capture, PVT (position, velocity and time) solution, data analysis and storage of the BeiDou-3 signal, and outputting BeiDou time information, where the BeiDou time information includes TOD (Time of Day) and 1PPS (pulse per second, 1pps = 1Hz) time information; a rubidium atomic clock timekeeping module connected to the BeiDou-3 signal processing module, receiving the TOD and 1PPS time information output by the BeiDou-3 signal processing module, performing timekeeping operations, and outputting the accumulated standard TOD time information and a high-precision 1PPS edge; a network time synchronization module connected to the rubidium atomic clock timekeeping module, receiving the TOD time information and the high-precision 1PPS edge information output by the rubidium atomic clock timekeeping module, and performing network time synchronization; and a power supply module for providing electrical energy for the high-precision timekeeping and network time synchronization system.

[0007] According to an embodiment of the present invention, the BeiDou-3 antenna module may include receiving antennas and low-noise amplifiers for the B1 / B2 / B3 frequency bands, and the low-noise amplifiers are used to amplify and filter the satellite signals received by the antennas.

[0008] According to an embodiment of the present invention, the BeiDou-3 signal processing module may include: an up / down conversion channel that respectively completes the conversion, filtering from intermediate frequency to radio frequency, radio frequency to intermediate frequency, and modulation of baseband spread-spectrum data; an AD (analog-to-digital) sampling chip that completes the digitization of the analog intermediate frequency; and a baseband processing chip that completes the positioning and timing functions of BeiDou-3 and realizes communication with external devices through the serial port of the baseband processing chip.

[0009] According to an embodiment of the present invention, the rubidium atomic clock timekeeping module may include a rubidium atomic clock, an FPGA (Field-Programmable Gate Array) chip, and an ARM chip. Among them, the Kalman filtering algorithm is used inside the ARM chip to estimate and correct the time deviation, and a DAC (digital-to-analog converter) chip is used for digital-to-analog conversion to voltage-control and adjust the 1PPS output of the rubidium clock.

[0010] According to an embodiment of the present invention, the network time synchronization module and the rubidium atomic clock timekeeping module can share the FPGA chip and the ARM chip. The FPGA chip has a high-speed bus clock, a hardware MAC (Media Access Control) receiving end, and an Ethernet functional unit. Among them, at the hardware MAC receiving end of the FPGA chip, the starting edge of time is recorded, and the time delay DELTA_T (time difference) is transmitted between the FPGA chip and the ARM chip in a parallel bus manner. Inside the ARM chip, the Kalman filtering algorithm is used to optimize the time delay DELTA_T, and it is sent back to the FPGA chip in a bus manner. Among them, the FPGA chip and the ARM chip cooperate with each other. The FPGA chip is responsible for capturing precise time, and the ARM is responsible for performing filtering algorithms and the interaction of message input and output.

[0011] According to an embodiment of the present invention, the high-precision timekeeping and network time synchronization system may further include a display and control unit, which includes a processor, a display screen, an indicator light, and a button connected to the processor. The display and control unit is used to complete the communication, control, status display of each module within the system, network IP setting, current time display, expansion and management of peripheral interfaces, and human-computer interaction.

[0012] According to another aspect of the present invention, a method for high-precision timekeeping and network time synchronization using a high-precision timekeeping and network time synchronization system based on Beidou signals is provided. The high-precision timekeeping and network time synchronization system based on Beidou signals includes a Beidou-3 antenna module, a Beidou-3 signal processing module, a rubidium atomic clock timekeeping module, a network time synchronization module, and a power supply module. The method includes the following steps: S1. Receive signals. The Beidou-3 antenna module completes the reception and filtering processing of electromagnetic wave signals at each frequency point of Beidou-3 and outputs a radio frequency signal; S2. Beidou-3 signal processing. The Beidou-3 signal processing module is connected to the Beidou-3 antenna module, receives the radio frequency signal output by the Beidou-3 antenna module, performs processing, completes the input capture, PVT solution, data analysis and storage of Beidou-3 signals, and outputs Beidou time information, where the Beidou time information includes TOD and 1PPS time information; S3. Rubidium atomic clock timekeeping. The rubidium atomic clock timekeeping module is connected to the Beidou-3 signal processing module, receives the TOD and 1PPS time information output by the Beidou-3 signal processing module, performs timekeeping operations, and outputs the accumulated standard TOD time information and a high-precision 1PPS edge; S4. Network time synchronization. The network time synchronization module is connected to the rubidium atomic clock timekeeping module, receives the TOD time information and the high-precision 1PPS edge information output by the rubidium atomic clock timekeeping module, and performs network time synchronization.

[0013] According to an embodiment of the present invention, the BeiSan signal processing steps may include the following sub-steps: S21. The BeiSan signal processing module receives radio frequency signals from the BeiSan antenna module, performs acquisition and tracking to stably track signals of more than four satellites; S22. The BeiSan signal processing module starts positioning and timing calculation. After a time T1, the user clock error and frequency difference converge to stable values; S23. The BeiSan signal processing module controls the number of samples between two calculations to make the difference between the calculation moment and the whole second moment within 1 sampling interval period, and executes it once after each calculation starts. This process is called coarse adjustment; S24. After coarse adjustment, the difference between the second pulse of the calculation time and the UTC whole second moment is within 1 sampling interval period. Let the difference be DELTA_T seconds, then control the next calculation period to be 1 + DELTA_T seconds, so that the second pulse of the next calculation moment is synchronized with the whole second moment. Then, fine adjustment is performed, and it is executed once after each calculation is completed. Fine adjustment is to modify the calculation period, and modifying the calculation period is to change the period of the sampling interval between two calculations, and change the period of the sampling interval to MEAS_PERIOD + DELTA_T seconds; S25. The positioning, timing calculation and sampling interval calculation of the BeiSan signal processing module are completed in the information processing unit, and then the calculation results are packetized in the signal processing module according to the standard Beidou data interface protocol. After packetization, Beidou time information is output externally.

[0014] According to an embodiment of the present invention, the rubidium atomic clock timekeeping steps may include the following sub-steps: S31. The rubidium atomic clock timekeeping module receives TOD + 1PPS time information from the BeiSan signal processing module; S32. The rubidium atomic clock timekeeping module converts the current TOD time information into a count value that can be recognized and accumulated by the internal register, and locks the 1PPS edge of Beidou; S33. The rubidium atomic clock timekeeping module uses the locked Beidou 1PPS time information edge to compare with the 1PPS edge output by the rubidium atomic clock, records the error DELTA_T between the two time edges, and the ARM chip internally uses the Kalman filtering algorithm to optimally estimate and correct the time deviation DELTA_T, and converts the estimation result into an analog signal output by the DAC digital-to-analog conversion chip to control the rubidium atomic clock; S34. Inside the rubidium atomic clock, the DELTA_T time difference is compensated into its output 1PPS, so that the output 1PPS of the rubidium clock and the 1PPS output by Beidou have comparable accuracy, and due to the principle of closed-loop control, its stability is higher than the Beidou 1PPS information; S35. Inside the rubidium atomic clock timekeeping module, through continuous closed-loop adjustment, the adjustment parameters are recorded, the accuracy and stability of 1PPS are corrected, the FGPA chip accumulates the high-precision 1PPS time in seconds, and packs the TOD data according to the Beidou standard data interface protocol, and outputs the accumulated standard TOD time information and the high-precision 1PPS edge externally.

[0015] According to an embodiment of the present invention, the network time synchronization step may include the following sub-steps: S41. The network time synchronization module receives the serial TOD time information and the high-precision 1PPS second edge information of the rubidium atomic clock timekeeping module, and then uses the high-speed bus clock inside the FPGA chip to accurately count the time unit to the nanosecond level; S42. The network time synchronization module configures the network MAC and IP underlying information using the Ethernet function unit inside the FPGA chip, uses the NTP network time protocol in the network application layer of the ARM chip to packetize the time data, and responds to the time information request of the client in real time to complete the NTP (Network Time Protocol) network time synchronization for the client; S43. The network time synchronization module configures the network MAC and IP underlying data using the Ethernet function unit inside the FPGA chip, adds a hardware time stamp at the MAC layer to eliminate the delay D1 brought by the operating system protocol stack, uses the Kalman filter algorithm to filter out the jitter, eliminates the network uplink and downlink jitter delay D2, and uses the PTP (Precise Time Protocol) of the IEEE 1588 precise time protocol in the network application layer to transmit time stamps T1, T2, T3, T4 and device diagnosis and time source optimization and other messages between the server and the client; S44. The network time synchronization module re-encodes the received TOD and 1PPS time information, and modulates the year, month, day, hour, minute and second information of TOD to a single-wire IO port according to different duty cycles to realize the single-wire IRIG-B (DC) code output of the time information.

[0016] Compared with the prior art, the technical solution provided by the embodiment of the present application can at least achieve the following beneficial effects:

[0017] 1. In the present invention, by introducing the high-precision time of Beidou into the network system and adding a timekeeping function, the advantages of all aspects are perfectly exerted, forming a unique high-precision time system to meet the needs of various industries for high-precision time.

[0018] 2. In the present invention, by performing coarse adjustment and fine adjustment on the sampling signal, accurate modulation of the sampling signal is realized, ensuring transmission accuracy and sampling accuracy.

[0019] 3. In the present invention, by using the Kalman filter algorithm to filter the DELTA_T time, the 1PPS accuracy of timekeeping is optimized, and the network delays D1 and D2 are optimized, thereby ensuring high-precision time.

[0020] 4. In the present invention, the design of each internal functional unit adopts the prior art, reducing the design difficulty and shortening the R & D cycle.

[0021] 5. In the present invention, the network time synchronization unit adopts an internationally standard network time synchronization application protocol, which is convenient for interfacing with network devices in various industries.

[0022] 6. In the present invention, the overall device adopts a standard 1U chassis structure, which is convenient for rack-mounted installation. The front panel of the 1U chassis is configured with human-computer interaction functions such as a liquid crystal display, LED lights, and buttons, with a friendly and user-friendly interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention and do not limit the present invention.

[0024] Figure 1 is a schematic diagram of the modules of the high-precision timekeeping and network time synchronization system according to the embodiments of the present invention.

[0025] Figure 2 is a schematic diagram of the working principle of the high-precision timekeeping and network time synchronization system according to the embodiments of the present invention.

[0026] Figure 3 is a schematic diagram of the working principle of the rubidium atomic clock timekeeping module according to the embodiments of the present invention.

[0027] Figure 4 is a flowchart of the network time synchronization according to the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0029] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The "first", "second", and similar terms used in the specification and claims of this patent application for the present invention do not denote any order, quantity, or importance, but are only used to distinguish different components. Similarly, the terms such as "a" or "one" do not denote a quantity limitation, but mean that there is at least one.

[0030] Figure 1 is a schematic diagram of the modules of the high-precision timekeeping and network time synchronization system according to the embodiments of the present invention. Figure 2 is a schematic diagram of the working principle of the high-precision timekeeping and network time synchronization system according to the embodiments of the present invention.

[0031] Such asFigure 1 and Figure 2 As shown in Figure 2 , the high-precision timekeeping and network time synchronization system based on Beidou signals includes: a Beidou-3 antenna module, a Beidou-3 signal processing module, a rubidium atomic clock timekeeping module, a network time synchronization module, and a power supply module.

[0032] The Beidou-3 antenna module is used to receive and filter electromagnetic wave signals at each frequency point of Beidou-3 and output radio frequency signals.

[0033] The Beidou-3 signal processing module is connected to the Beidou-3 antenna module, receives the radio frequency signals output by the Beidou-3 antenna module, processes them, completes the input capture, PVT (position, velocity and time) solution, data analysis and storage of Beidou-3 signals, and outputs Beidou time information, where the Beidou time information includes TOD (Time of Day) and 1PPS (pulse per second, 1pps = 1Hz) time information.

[0034] The rubidium atomic clock timekeeping module is connected to the Beidou-3 signal processing module, receives the TOD and 1PPS time information output by the Beidou-3 signal processing module, performs timekeeping operations, and outputs the accumulated standard TOD time information and high-precision 1PPS edge.

[0035] The network time synchronization module is connected to the rubidium atomic clock timekeeping module, receives the TOD time information and high-precision 1PPS edge information output by the rubidium atomic clock timekeeping module, and performs network time synchronization.

[0036] The power supply module is used to provide electrical energy for the high-precision timekeeping and network time synchronization system.

[0037] By introducing the high-precision time of Beidou into the network system and adding a timekeeping function, the advantages of all aspects are perfectly exerted, forming a unique high-precision time system to meet the needs of various industries for high-precision time.

[0038] According to one or some embodiments of the present invention, the Beidou-3 antenna module includes receiving antennas for the B1 / B2 / B3 frequency bands and low-noise amplifiers, and the low-noise amplifiers are used to amplify and filter the satellite signals received by the antennas. The design of each internal functional unit adopts existing technologies, reducing the design difficulty and shortening the R & D cycle.

[0039] According to one or some embodiments of the present invention, the Beidou-3 signal processing module includes: up / down conversion channels, which respectively complete the conversion, filtering from intermediate frequency to radio frequency, radio frequency to intermediate frequency, and modulation of baseband spread-spectrum data; an AD (analog-to-digital) sampling chip, which completes the digitization of the analog intermediate frequency; and a baseband processing chip, which completes the positioning and timing functions of Beidou-3 and realizes communication with external devices through the serial port of the baseband processing chip.

[0040] Figure 3 It is a schematic diagram of the working principle of the rubidium atomic clock timekeeping module according to an embodiment of the present invention.

[0041] As Figure 3 shown, the rubidium atomic clock timekeeping module includes a rubidium atomic clock, an FPGA (Field-Programmable Gate Array) chip, and an ARM chip. Among them, the Kalman filtering algorithm is used inside the ARM chip to estimate and correct the time deviation, and a DAC (Digital-to-Analog Converter) chip is used for digital-to-analog conversion to voltage-control and adjust the 1PPS output of the rubidium clock. By using the Kalman filtering algorithm to filter the DELTA_T time, the accuracy of the timekeeping 1PPS is optimized, and the network delays D1 and D2 are optimized, thereby ensuring high-precision time.

[0042] Figure 4 It is a flowchart of network time synchronization according to an embodiment of the present invention.

[0043] As Figure 4 shown, the network time synchronization module shares the FPGA chip and the ARM chip with the rubidium atomic clock timekeeping module. The FPGA chip has a high-speed bus clock, a hardware MAC (Media Access Control) receiving end, and an Ethernet functional unit. Among them, the starting edge of the time is recorded at the hardware MAC receiving end of the FPGA chip, and the time delay DELTA_T (time difference) is transmitted between the FPGA chip and the ARM chip in a parallel bus manner. The Kalman filtering algorithm is used inside the ARM chip to optimize the time delay DELTA_T and is sent back to the FPGA chip in a bus manner. Among them, the FPGA chip and the ARM chip cooperate with each other. The FPGA chip is responsible for capturing precise time, and the ARM is responsible for filtering algorithms and the interaction of message input and output.

[0044] According to one or some embodiments of the present invention, the high-precision timekeeping and network time synchronization system further includes a display and control unit, which includes a processor, a display screen, an indicator light, and a button connected to the processor. The display and control unit is used to complete the communication, control, status display of each module within the system, network IP setting, current time display, expansion and management of peripheral interfaces, and human-computer interaction. The overall device adopts a standard 1U chassis structure, which is convenient for rack-mounted installation. The front panel of the 1U chassis is equipped with human-computer interaction functions such as a liquid crystal display screen, LED lights, and buttons, with a friendly and user-friendly interface.

[0045] According to one or some embodiments of the present invention, a method for high-precision timekeeping and network time synchronization using a high-precision timekeeping and network time synchronization system based on Beidou signals includes the following steps: S1. Receive signals. The BeiSan antenna module completes the reception and filtering of electromagnetic wave signals at each frequency point of BeiSan, and outputs a radio frequency signal; S2. BeiSan signal processing. The BeiSan signal processing module is connected to the BeiSan antenna module, receives the radio frequency signal output by the BeiSan antenna module, processes it, completes the input capture, PVT solution, data analysis and storage of the BeiSan signal, and outputs Beidou time information, where the Beidou time information includes TOD and 1PPS time information; S3. Rubidium atomic clock timekeeping. The rubidium atomic clock timekeeping module is connected to the BeiSan signal processing module, receives the TOD and 1PPS time information output by the BeiSan signal processing module, performs timekeeping operations, and outputs the accumulated standard TOD time information and high-precision 1PPS edge; S4. Network time synchronization. The network time synchronization module is connected to the rubidium atomic clock timekeeping module, receives the TOD time information and high-precision 1PPS edge information output by the rubidium atomic clock timekeeping module, and performs network time synchronization.

[0046] According to one or some embodiments of the present invention, the BeiSan signal processing step includes the following sub-steps: S21. The BeiSan signal processing module receives the radio frequency signal from the BeiSan antenna module, performs capture and tracking until it stably tracks more than four satellite signals; S22. The BeiSan signal processing module starts positioning and timing solution. After T1 time, the user clock error and frequency difference converge to stable values; S23. The BeiSan signal processing module controls the number of samples between two solutions to make the difference between the solution time and the whole second time within 1 sampling interval period, and executes it once after each solution starts. This process is called coarse adjustment; S24. After coarse adjustment, the difference between the solution time second pulse and the UTC whole second time is within 1 sampling interval period. Let the difference be DELTA_T seconds, then control the next solution period to be 1 + DELTA_T seconds, so that the next solution time second pulse is synchronized with the whole second time. Then, fine adjustment is performed, and it is executed once after each solution is completed. Fine adjustment is to modify the solution period, and modifying the solution period is to change the sampling interval period between two solutions, and change the sampling interval period to MEAS_PERIOD + DELTA_T seconds; S25. The positioning, timing solution and sampling interval calculation of the BeiSan signal processing module are completed in the information processing unit, and then the solution results are packetized in the signal processing module according to the standard Beidou data interface protocol. After packetization is completed, Beidou time information is output externally. By performing coarse adjustment and fine adjustment on the sampled signal, precise modulation of the sampled signal is achieved, ensuring transmission accuracy and sampling accuracy.

[0047] According to one or some embodiments of the present invention, the timekeeping steps of the rubidium atomic clock include the following sub-steps: S31. The timekeeping module of the rubidium atomic clock receives the TOD + 1PPS time information from the BeiDou-3 signal processing module; S32. The timekeeping module of the rubidium atomic clock converts the current TOD time information into a count value that can be recognized and accumulated by the internal register, and locks onto the 1PPS edge of BeiDou; S33. The timekeeping module of the rubidium atomic clock uses the locked 1PPS time information edge of BeiDou to compare with the 1PPS edge output by the rubidium atomic clock, records the error DELTA_T between the two time edges, and the internal ARM chip uses the Kalman filtering algorithm to optimally estimate and correct the time deviation DELTA_T, converts the estimation result into an analog signal output using a DAC digital-to-analog conversion chip, and controls the rubidium atomic clock; S34. Inside the rubidium atomic clock, the DELTA_T time difference is compensated into its output 1PPS, so that the output 1PPS of the rubidium clock has a comparable accuracy to the 1PPS output by BeiDou, and due to the principle of closed-loop control, its stability is higher than the BeiDou 1PPS information; S35. Inside the timekeeping module of the rubidium atomic clock, through continuous closed-loop regulation, the regulation parameters are recorded, the accuracy and stability of 1PPS are corrected, the FGPA chip accumulates the high-precision 1PPS time in seconds, and packs the TOD data according to the BeiDou standard data interface protocol, and externally outputs the accumulated standard TOD time information and the high-precision 1PPS edge.

[0048] According to one or some embodiments of the present invention, the network time synchronization steps include the following sub-steps: S41. The network time synchronization module receives the serial TOD time information and the high-precision 1PPS second edge information from the rubidium atomic clock timekeeping module, and then uses the high-speed bus clock inside the FPGA chip to accurately count the time unit to the nanosecond level; S42. The network time synchronization module configures the network MAC and IP underlying information by using the Ethernet function unit inside the FPGA chip, groups the time data by using the NTP network time protocol in the network application layer of the ARM chip, and responds to the time information request of the client in real time to complete the NTP (Network Time Protocol) network time synchronization for the client; S43. The network time synchronization module configures the network MAC and IP underlying data by using the Ethernet function unit inside the FPGA chip, stamps the hardware time at the MAC layer to eliminate the delay D1 brought by the operating system protocol stack, uses the Kalman filtering algorithm to filter out the jitter, eliminates the network uplink and downlink jitter delay D2, and uses the PTP (Precise Time Protocol) of the IEEE 1588 precise time protocol in the network application layer to transmit the time stamps T1, T2, T3, T4 and device diagnosis and time source preference and other messages between the server and the client; S44. The network time synchronization module re-encodes the received TOD and 1PPS time information, and modulates the year, month, day, hour, minute and second information of TOD to a single-wire IO port according to different duty cycles to realize the single-wire IRIG-B (DC) code output of the time information. The network time synchronization unit adopts an international standard network time synchronization application protocol, which is convenient for interfacing with network devices in various industries.

[0049] The above is only an exemplary implementation manner of the present invention, and is not used to limit the protection scope of the present invention. The protection scope of the present invention is determined by the appended claims.

Claims

1. A high-precision timekeeping and network time synchronization method based on Beidou signals, which uses a high-precision timekeeping and network time synchronization system based on Beidou signals to perform high-precision timekeeping and network time synchronization. The high-precision timekeeping and network time synchronization system based on Beidou signals includes a Beidou three-antenna module, a Beidou three-signal processing module, a rubidium atomic clock timekeeping module, a network time synchronization module, and a power supply module. The method includes the following steps: S1. Receive signals. The Beidou three-antenna module completes the reception and filtering of electromagnetic wave signals at each frequency point of Beidou three, and outputs a radio frequency signal. S2. Beidou three-signal processing. Receive the radio frequency signal output by the Beidou three-antenna module, process it, complete the input capture, PVT solution, data analysis and storage of Beidou three signals, and output Beidou time information, where the Beidou time information includes TOD and 1PPS time information. S3. Rubidium atomic clock timekeeping. Receive the TOD and 1PPS time information output by the Beidou three-signal processing module, perform timekeeping operations, and output the accumulated standard TOD time information and high-precision 1PPS edge. S4. Network time synchronization. Receive the TOD time information and high-precision 1PPS edge information output by the rubidium atomic clock timekeeping module, and perform network time synchronization. Among them, the network time synchronization step includes the following sub-steps: S41. The network time synchronization module receives the serial TOD time information and high-precision 1PPS second edge information of the rubidium atomic clock timekeeping module, and then uses the high-speed bus clock inside the FPGA chip to accurately measure the time counting unit to the nanosecond level. S42. The network time synchronization module configures the network MAC and IP underlying information using the Ethernet function unit inside the FPGA chip, uses the NTP network time protocol at the network application layer of the ARM chip to packetize time data, and responds to the time information request of the client in real time to complete the NTP network time synchronization for the client. S43. The network time synchronization module configures the network MAC and IP underlying data using the Ethernet function unit inside the FPGA chip, adds a hardware time stamp at the MAC layer to eliminate the delay D1 brought by the operating system protocol stack, uses the Kalman filter algorithm to filter out jitter and eliminate the network uplink and downlink jitter delay D2, and uses the IEEE1588 precise time protocol at the network application layer to transmit time stamps T1, T2, T3, T4, and device diagnosis and time source messages between the server and the client. S44. The network time synchronization module re-encodes the received TOD and 1PPS time information, and modulates the year, month, day, hour, minute, and second information of TOD to a single-wire IO port according to different duty cycles to achieve the single-wire IRIG-B code output of time information.

2. The high-precision timekeeping and network time synchronization method according to claim 1, wherein, The Beidou three-signal processing step includes the following sub-steps: S21. The Beidou three-signal processing module receives the radio frequency signal from the Beidou three-antenna module, performs capture and tracking, and achieves stable tracking of more than four satellite signals. S22. The Beidou three-signal processing module starts positioning and timing solution. After time T1, the receiver clock error and frequency error converge to stable values. S23. The north three signal processing module makes the difference between the calculation moment and the whole second moment within one sampling interval period by controlling the number of samples between two calculations. This process is executed once after each calculation starts and is called coarse tuning. S24. When the difference between the calculation time second pulse after coarse tuning and the UTC whole second moment is within one sampling interval period, and the difference is set as DELTA_T seconds, then control the next calculation period to be 1 + DELTA_T seconds. In this way, the second pulse of the next calculation moment is synchronized with the whole second moment. Then, fine tuning is carried out, which is executed once after each calculation is completed. The fine tuning is to modify the calculation period, and modifying the calculation period is to change the period of the sampling interval between two calculations, and change the period of the sampling interval to MEAS_PERIOD + DELTA_T seconds. S25. The positioning, timing calculation and sampling interval calculation of the north three signal processing module are completed within the information processing unit, and then the calculation results are packetized in the signal processing module according to the standard Beidou data interface protocol. After packetization is completed, Beidou time information is output externally.

3. The high-precision timekeeping and network time synchronization method according to claim 1, wherein The steps of the rubidium atomic clock timekeeping include the following sub-steps: S31. The rubidium atomic clock timekeeping module receives TOD + 1PPS time information from the north three signal processing module. S32. The rubidium atomic clock timekeeping module converts the current TOD time information into a count value that can be recognized and accumulated by the internal register, and locks the 1PPS edge of Beidou. S33. The rubidium atomic clock timekeeping module uses the locked Beidou 1PPS time information edge to compare with the 1PPS edge output by the rubidium atomic clock, records the error DELTA_T between the two time edges, and the ARM chip internally uses the Kalman filtering algorithm to optimally estimate and correct the time deviation DELTA_T, and converts the estimation result into an analog signal output by the DAC digital-to-analog conversion chip to control the rubidium atomic clock. S34. Inside the rubidium atomic clock, the DELTA_T time difference is compensated into its output 1PPS, so that the output 1PPS of the rubidium clock has the same accuracy as the 1PPS output by Beidou, and due to the principle of closed-loop control, its stability is higher than the Beidou 1PPS information. S35. Inside the rubidium atomic clock timekeeping module, through continuous closed-loop adjustment, the adjustment parameters are recorded to correct the accuracy and stability of 1PPS. The FGPA chip accumulates the high-precision 1PPS time in seconds, and packs the TOD data according to the Beidou standard data interface protocol, and outputs the accumulated standard TOD time information and the high-precision 1PPS edge externally.

4. A high-precision timekeeping and network time dissemination system based on Beidou signals. The system adopts the high-precision timekeeping and network time dissemination method based on Beidou signals according to any one of claims 1-3. The system includes: The north three antenna module is used to complete the reception and filtering processing of electromagnetic wave signals at each frequency point of the north three, and output radio frequency signals. The North Three signal processing module, connected to the North Three antenna module, receives the radio frequency signals output by the North Three antenna module, processes them, completes the input capture, PVT solution, data analysis and storage of the North Three signals, and outputs Beidou time information, where the Beidou time information includes TOD and 1PPS time information; The rubidium atomic clock timekeeping module, connected to the North Three signal processing module, receives the TOD and 1PPS time information output by the North Three signal processing module, performs timekeeping operations, and outputs the accumulated standard TOD time information and high-precision 1PPS edge; The network time synchronization module, connected to the rubidium atomic clock timekeeping module, receives the TOD time information and high-precision 1PPS edge information output by the rubidium atomic clock timekeeping module, and performs network time synchronization; The power supply module is used to provide electrical energy for the high-precision timekeeping and network time synchronization system.

5. The high-precision timekeeping and network time synchronization system according to claim 4, wherein the North Three antenna module includes receiving antennas for B1 / B2 / B3 frequency bands and low-noise amplifiers, and the low-noise amplifiers are used to amplify and filter the satellite signals received by the antennas.

6. The high-precision timekeeping and network time synchronization system according to claim 4, wherein the North Three signal processing module includes: The up / down conversion channel, which respectively completes the conversion, filtering from intermediate frequency to radio frequency, radio frequency to intermediate frequency, and modulation of baseband spread-spectrum data; The AD sampling chip, which completes the digitization of the analog intermediate frequency; The baseband processing chip, which completes the positioning and timing functions of the North Three, and realizes communication with external devices through the serial port of the baseband processing chip.

7. The high-precision timekeeping and network time synchronization system according to claim 4, wherein the rubidium atomic clock timekeeping module includes a rubidium atomic clock, an FPGA chip and an ARM chip, Among them, Inside the ARM chip, the Kalman filtering algorithm is used to estimate and correct the time deviation, and a DAC chip is used for digital-to-analog conversion to voltage-control and adjust the 1PPS output of the rubidium clock.

8. The high-precision timekeeping and network time synchronization system according to claim 7, wherein the network time synchronization module shares the FPGA chip and the ARM chip with the rubidium atomic clock timekeeping module, and the FPGA chip has a high-speed bus clock, a hardware MAC receiving end and an Ethernet functional unit, Among them, At the hardware MAC receiving end of the FPGA chip, the time start edge is recorded, the time delay DELTA_T is transmitted between the FPGA chip and the ARM chip in a parallel bus manner, and inside the ARM chip, the Kalman filtering algorithm is used to optimize the time delay DELTA_T and send it back to the FPGA chip in a bus manner, wherein, the FPGA chip is responsible for capturing precise time, and the ARM is responsible for performing filtering algorithms and the interaction of message input and output.

9. The high-precision timekeeping and network time synchronization system according to claim 4 further includes a display and control unit, which includes a processor, a display screen, an indicator light, and a button connected to the processor. The display and control unit is used to complete the communication and control of each module within the system, display the status of each module, set the network IP, display the current time, expand and manage the external device interface, and perform human-computer interaction.

Images