CN116027242B - High-precision time-frequency calibration and synchronization system and method based on multi-source GNSS - Google Patents
High-precision time-frequency calibration and synchronization system and method based on multi-source GNSS Download PDFInfo
- Publication number
- CN116027242B CN116027242B CN202310013411.3A CN202310013411A CN116027242B CN 116027242 B CN116027242 B CN 116027242B CN 202310013411 A CN202310013411 A CN 202310013411A CN 116027242 B CN116027242 B CN 116027242B
- Authority
- CN
- China
- Prior art keywords
- gnss
- time
- frequency
- clock
- utc
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000034 method Methods 0.000 title claims abstract description 21
- 239000013078 crystal Substances 0.000 claims abstract description 21
- 238000004422 calculation algorithm Methods 0.000 claims description 35
- LIWAQLJGPBVORC-UHFFFAOYSA-N ethylmethylamine Chemical compound CCNC LIWAQLJGPBVORC-UHFFFAOYSA-N 0.000 claims description 31
- 238000004458 analytical method Methods 0.000 claims description 18
- 230000006870 function Effects 0.000 claims description 16
- 230000000630 rising effect Effects 0.000 claims description 15
- 230000009466 transformation Effects 0.000 claims description 15
- 238000001914 filtration Methods 0.000 claims description 6
- 238000004590 computer program Methods 0.000 claims description 5
- 238000004891 communication Methods 0.000 claims description 4
- 238000005516 engineering process Methods 0.000 abstract description 4
- 238000010586 diagram Methods 0.000 description 6
- 238000012937 correction Methods 0.000 description 5
- 230000008859 change Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 101100119135 Mus musculus Esrrb gene Proteins 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 230000006855 networking Effects 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000013500 data storage Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000005433 ionosphere Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention relates to a time-frequency calibration and synchronization technology, in particular to a high-precision time-frequency calibration and synchronization system and method based on a multi-source GNSS. Based on the phase-locked loop technology, PPS second pulse signals given by a single or a plurality of navigation systems GNSS (Beidou, GPS, gelnas, galileo) are used as reference standard, and FPGA control is used for automatically calibrating the voltage-controlled constant-temperature crystal oscillator OCXO, so that a clock source with high precision and high stability is obtained. The system clock stability can be up to 5ppb and can provide sub-second time resolution up to 5ns levels. The FPGA control system can configure the GNSS receiver, so that single or multiple GNSS signal sources are selected according to user requirements, and the running reliability and safety of the equipment are ensured.
Description
Technical Field
The invention belongs to the technical field of time-frequency calibration and synchronization, and particularly relates to a high-precision time-frequency calibration and synchronization system and method based on a multi-source GNSS.
Background
Very low frequency (VLF, very Low Frequency) refers to electromagnetic waves having a frequency in the range of 3kHz to 30kHz, which may be generated by natural phenomena (e.g., lightning) or by man-made (e.g., station signals and electromagnetic interference). VLF has great significance in research in the fields of earth ionosphere, magnetic layer, remote sensing detection, navigation communication, etc. In order to obtain more comprehensive VLF signal information, researchers need to build a detection network composed of a plurality of observation sites, and how to perform accurate time-frequency synchronization on the plurality of observation sites becomes a problem to be solved.
When VLF detection equipment works in networking, each equipment needs to work based on the same time standard so as to ensure the operational order and reliability. The traditional time-frequency calibration system based on GNSS second pulse often has the problems of insufficient calibration precision, too slow convergence speed, single GNSS signal source, poor anti-interference capability and the like, so that the high-precision time synchronization system applied to multi-equipment networking needs to be further improved. And the PID algorithm based on error nonlinear transformation is adopted, so that the convergence speed and the frequency correction precision of frequency correction are improved.
Disclosure of Invention
Aiming at the problems existing in the background technology, the invention provides a novel time-frequency calibration and synchronization method, the clock calibration precision can reach 5ppb, and the time synchronization resolution can reach 5ns.
In order to solve the technical problems, the invention adopts the following technical scheme: the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS comprises a GNSS control module, an NMEA analysis module, a clock calibration module and a time synchronization module;
the GNSS control module is connected with the GNSS receiver, changes the working state of the GNSS receiver by sending an instruction, and switches the selected GNSS system;
the NMEA analysis module receives an NMEA message given by the GNSS receiver, and analyzes the message to obtain UTC time, longitude and latitude information and satellite attitude information;
the clock calibration module takes a PPS signal given by the GNSS receiver as a reference, compares a phase difference with a local first PPS signal obtained by frequency division of the constant temperature crystal oscillator OCXO, adjusts the frequency of the constant temperature crystal oscillator OCXO, and obtains a local clock source;
the time synchronization module acquires UTC second-level time by combining the UTC time information acquired by the NMEA analysis module with the PPS signal, and acquires sub-second-level time resolution by utilizing a local clock source given by the clock calibration module.
In the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, the GNSS control module receives the upper computer instruction, selects the corresponding control instruction ID according to the instruction, then uses the Command ID to acquire the content of the GNSS control instruction from the ROM of the storage GNSS instruction, and sends the content to the GNSS receiver through the communication interface, thereby realizing the functions of switching different GNSS systems, saving/resetting configuration and setting NMEA output message types.
In the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, an NMEA analysis module receives an NMEA message from a GNSS receiver, and analyzes and obtains UTC time, longitude and latitude and altitude information.
In the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, the clock calibration module adopts a phase-locked loop structure and comprises a frequency divider, a frequency multiplier, a digital phase discriminator, a Kalman filter, a PID module and a DAC control module;
the frequency divider divides the frequency of a clock from the local constant temperature crystal oscillator OCXO to obtain a local first PPS signal;
the frequency multiplier multiplies the clock from the local constant temperature crystal oscillator OCXO to obtain a high-frequency phase discrimination clock;
the digital phase discriminator compares the phase difference between a first PPS signal from the GNSS and a local first PPS signal, and obtains a phase difference first phase difference between the two PPS signals by counting a high-frequency phase discrimination clock;
the Kalman filter filters the first phase difference, eliminates phase jitter, and outputs a second phase difference of a filtering result;
the PID module receives the phase error err and calculates and outputs a control signal through a PID algorithm;
and the DAC control module adjusts the output voltage of the DAC according to the control signal, so as to adjust the output frequency of the local constant-temperature crystal oscillator OCXO.
In the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, the time synchronization module input interface comprises: the PPS signal, the NMEA analysis module analyzes the obtained time information NMEA_UTC_time and the clock signal OCXO_10M of the constant-temperature crystal oscillator OCXO; the output signal includes: UTC time utc_time, OCXO clock count cnt_10m from PPS rising edge; NMEA_UTC_time, UTC_time is the sum of a set of signals, including UTC year/monta/day, UTC hh/mm/ss.
A high-precision time-frequency calibration and synchronization system method based on a multi-source GNSS is based on a phase-locked loop structure, PPS second pulse signals given by a single or a plurality of navigation system GNSS are used as reference standards, and FPGA control is used for calibrating a voltage-controlled constant-temperature crystal oscillator OCXO, so that a clock source is obtained.
In the method of the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, the core algorithm controlled by the FPGA comprises the following steps: digital phase discrimination algorithm, kalman-PID joint control algorithm and nonlinear PID control algorithm.
In the method for the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, the method configures the GNSS receiver through the FPGA, and single or multiple GNSS signal sources are selected according to user requirements.
In the method of the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, the nonlinear PID control algorithm comprises: firstly, carrying out nonlinear transformation on an input error e (t) to obtain epsilon (t), then respectively carrying out proportional, integral and differential operations on epsilon (t), and carrying out weighted summation operation on the epsilon (t) and the epsilon (t) to obtain a control quantity u (t);
let the nonlinear transformation function g (x), g (x) be the odd function:
for the input error err, calculating through a transformation function g (x) to obtain a transformation result second error err2; setting parameter K p ＝0.1，K i ＝0.01，K d =0, by the formula:
the control amount u (t) is calculated.
In the method for high-precision time-frequency calibration and synchronization system based on multi-source GNSS, GNSS signal sources comprise Beidou, GPS, geronas and Galileo systems.
An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the method of multi-source GNSS based high precision time frequency calibration and synchronization system when the computer program is executed.
Compared with the prior art, the invention has the beneficial effects that: the invention uses FPGA to control and automatically calibrate the voltage-controlled constant temperature crystal oscillator OCXO, thereby obtaining the clock source with high precision and high stability. The system clock stability can be up to 5ppb and can provide sub-second time resolution up to 5ns levels. According to the system, the GNSS receiver is configured through the FPGA, and single or multiple GNSS signal sources are selected according to user requirements, so that the reliability and safety of equipment operation are guaranteed.
Drawings
FIG. 1 is a schematic diagram of hardware connection of a time-frequency calibration and synchronization system according to an embodiment of the present invention;
FIG. 2 is a block diagram of a clock calibration module according to an embodiment of the invention;
FIG. 3 is a block diagram of a nonlinear PID algorithm in accordance with an embodiment of the invention;
FIG. 4 is a schematic diagram of an interface of a time synchronization module according to an embodiment of the present invention;
fig. 5 is a timing diagram of input/output signals of the time synchronization module according to an embodiment of the invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention will be further illustrated, but is not limited, by the following examples.
According to the high-precision time-frequency calibration and synchronization system based on the multi-source GNSS, the system is based on a phase-locked loop technology, PPS second pulse signals given by single or multiple navigation system GNSS are used as reference standards, and FPGA control is used for automatically calibrating the voltage-controlled constant-temperature crystal oscillator OCXO, so that a clock source with high precision and high stability is obtained. Practical tests show that the system clock stability can reach 5ppb and can provide sub-second time resolution of up to 5ns level. The FPGA controls the operation of the whole system, and the core algorithm mainly comprises the following steps: high-precision digital phase discrimination algorithm, kalman-PID joint control algorithm and nonlinear PID control algorithm. In addition, the system can configure the GNSS receiver through the FPGA, so that single or multiple GNSS signal sources are selected according to the user requirements, and the reliability and the safety of equipment operation are ensured.
As shown in fig. 1, the high-precision time-frequency calibration and synchronization system based on multi-source GNSS includes: the system comprises a GNSS control module, an NMEA analysis module, a clock calibration module and a time synchronization module.
The GNSS control module is connected with the GNSS receiver, and can change the working state of the GNSS receiver by sending an instruction to switch the selected GNSS system. The NMEA analysis module receives an NMEA message given by the GNSS receiver, and analyzes the message to obtain UTC time, longitude and latitude information, satellite attitude and other information. The clock calibration module takes a PPS signal given by the GNSS receiver as a reference, and compares the phase difference with a local 1PPS signal obtained by OCXO frequency division, so that the frequency of the OCXO is adjusted, and a high-precision and high-stability local clock source is obtained. The time synchronization module acquires accurate UTC second time by combining the PPS signal by utilizing the time information acquired by the NMEA analysis module, and acquires high-precision sub-second time resolution by utilizing a high-precision local clock source provided by the clock calibration module.
The GNSS control module receives the upper computer instruction, selects a corresponding control instruction ID according to the instruction, then uses the Command ID to acquire the content of the GNSS control instruction from the ROM storing the GNSS instruction, and sends the content to the GNSS receiver through a communication interface (UART interface is selected in the embodiment), thereby realizing the functions of switching different GNSS systems, saving/resetting configuration, setting NMEA output message types and the like. The data storage format of the GNSS instruction ROM is as follows: each (Max Command Len+1) unit is a group, the starting address of each group of data is Command ID× (Max Command Len+1), the first storage unit of each group of data records the length of the instruction, and the actual instruction content is stored from the second storage unit, wherein Max Command Len is the maximum instruction length (Bytes).
And the NMEA analysis module receives the NMEA message from the GNSS receiver, and analyzes and obtains information such as UTC time, longitude and latitude, altitude and the like. It should be noted that, the UTC time obtained by parsing the NMEA packet is not the time when the NMEA packet is sent, but corresponds to the rising edge of the next first PPS signal, and the rising edge of each first PPS signal is aligned to the starting time of UTC seconds, so that the UTC time output by the NMEA packet parsing module is always earlier than the real time, and needs to be registered at the rising edge of the first PPS signal, and the value output by the register corresponds to the real UTC time. In this embodiment, the RMC message is selectively parsed, where the RMC message includes information such as UTC date, UTC time, longitude and latitude, and the spatial information is relatively comprehensive.
The clock calibration module structure is shown in fig. 2, and adopts a phase-locked loop structure, and mainly comprises: the digital phase discriminator, the frequency divider, the frequency multiplier, the Kalman filter, the PID module and the DAC control module. The frequency divider divides the clock from the local oven controlled crystal oscillator OCXO to obtain a local first 1PPS signal. The frequency multiplier multiplies the clock from the OCXO to obtain a high-frequency phase-discrimination clock. The digital phase detector compares the phase difference between the first 1PPS signal from the GNSS and the local 1PPS signal, and obtains the phase difference between the two PPS signals by counting the high frequency phase-discriminating clock, as shown by the first phase difference 1. The Kalman filter filters the first phase difference 1, eliminates phase jitter that may exist, and outputs a filtering result, i.e., the second phase difference 2. Note that the local first 1PPS signal may have a large initial offset from the first 1PPS signal, and it takes a very long time to cancel the offset using the PID algorithm, which is not practical, and has no practical meaning, so the initial phase difference should be recorded at reset, and the initial phase difference is stored in a reg register shown in the figure, and the phase error err is obtained by subtracting the initial phase difference from the second phase difference 2 during phase locking, which is the actual input error of the PID module. The PID module receives the phase error err and calculates and outputs a control signal through a PID algorithm. The DAC control module adjusts the output voltage of the DAC according to the control signal, so as to adjust the output frequency of the OCXO.
In order to further improve the convergence speed and the frequency correction precision of the frequency correction, the traditional PID algorithm is improved, and the PID algorithm based on error nonlinear transformation is adopted, and the algorithm structure is shown in figure 3. The nonlinear PID algorithm firstly carries out nonlinear transformation on an input error e (t) to obtain epsilon (t), then carries out proportional, integral and differential operations on epsilon (t) respectively, and carries out weighted summation operation on the epsilon (t) and the epsilon (t) to obtain a control quantity u (t).
The nonlinear transformation function of the nonlinear PID algorithm can select different expression forms according to different requirements, but note that the selected nonlinear transformation function should be an odd function in the interval [0, + ] infinity]Monotonically increasing, and parameter K p 、K i 、K d The parameters should be appropriate to meet the convergence of the PID algorithm. In contrast, the conventional PID algorithm requires artificial modification of the parameter K if it is required to change the control characteristics of the early and late stages p 、K i 、K d This is likely to occur when the convergence condition is not satisfied.
For the traditional PID algorithm in the discrete domain:
where only the proportional term P and integral term I are used (i.e., K is taken d =0), to satisfy
Can ensure the convergence of the PID algorithm, and generally takes K for the algorithm to have better anti-interference performance p ＝0.01～0.1，K i ＝(0.01～0.1)K p 。
For a more general case, it is desirable to use larger control parameters in the early stage of the algorithm to enable the PID algorithm to converge near the target value as soon as possible, and then use smaller control parameters to enable the algorithm to enter a fine tuning state to obtain higher adjustment accuracy. For this requirement, a functionally equivalent and hardware-friendly nonlinear transformation function can be designed as follows
Still only the proportional term P and integral term I are used, if convergence conditions are to be met
Where a=max { g' (x) }, b=max { g (x)/x }, in this embodiment a=1, b=1. Thus taking the parameter K p ＝0.1，K i ＝0.01。
The digital phase discriminator measures the rising edge time interval of the first 1PPS signal and the local first 1PPS signal, takes the output clock of the frequency multiplier as a counting clock, outputs the counting number of high-frequency counting clocks between the two rising edges, and takes the counting value as the phase difference of the two PPS signals.
The time synchronization module interface is shown in fig. 4, and the input interfaces include: PPS signal, NMEA analysis module analyzes obtained time information NMEA_UTC_time the clock signal OCXO _10M of the oven controlled crystal OCXO (10 MHz voltage controlled oven controlled crystal is used in this embodiment), the output signals are: UTC time utc_time, OCXO clock count cnt_10m from PPS rising edge. The NMEA_UTC_time, UTC_time is the sum of a set of signals, including UTC year/monta/day, UTC hh/mm/ss.
As shown in fig. 5, the timing chart of the input/output signal of the time synchronization module is that the time synchronization module uses the clock ocxo_10m of the oven controlled crystal OCXO as the working clock, and detects whether the PPS signal is hopped or not at the rising edge of the ocxo_10m. If the rising edge of the PPS is detected, zeroing the cnt_10M, and registering the value of the NMEA_UTC_time into the UTC_time; otherwise, on the ocxo_10m rising edge, cnt_10m self-increases by 1, while utc_time remains. By the design, the change of UTC_time is strictly synchronous with the moment when cnt_10M becomes 0, so that the problem of jump in the subsequent time acquisition is avoided. When the later module obtains time, UTC_time is the accurate second time, and the accurate sub-second time can be obtained through the value calculation of cnt_10M. For example, utc_time=16/11/22 09:13:47,cnt_10M =354, then corresponding to UTC time: 2022, 11, 16, 09, 13 minutes, 47 seconds, 000 milliseconds 035 microseconds, 400 nanoseconds.
In this embodiment, since a 10M driving clock is used, the sub-second time resolution is 100ns, and the error between the output time of the time synchronization module and the absolute accurate UTC time is less than 100ns. Since the ocxo_10m frequency has been corrected by PPS second pulses, the ocxo_10m is multiplied using a phase locked loop PLL, the accuracy of which will be transferred to the multiplied clock, thereby improving to sub-second time resolution and time accuracy. Specifically, the ocxo_10m is multiplied to 100MHz, the multiplied clock is clk_100deg.M, and since the accuracy of the clock frequency of the ocxo_10m is 5ppb, the accuracy of the clock frequency of clk_100deg.M is also 5ppb, the time of sub-second level obtained by counting the clock has the maximum time error of max {1/100e6,5e-9}s =10ns, wherein the former corresponds to the error caused by the time resolution, inversely proportional to the frequency of the working clock, and the latter corresponds to the accuracy of the clock frequency, i.e. the maximum accumulated phase error within 1s caused by the frequency error of clk_100deg.M, which is determined by the working performance of the phase-locked loop clock calibration module.
An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the method of multi-source GNSS based high precision time frequency calibration and synchronization system when the computer program is executed.
In specific implementation, the novel high-precision time-frequency calibration and synchronization system is realized based on the FPGA by using various GNSS signal sources. Through the phase-locked loop structure, the calibration of the OCXO frequency is realized by combining a second pulse signal of a satellite navigation system, and meanwhile, the self-adaptive dynamic parameter adjustment is realized by combining Kalman filtering and a nonlinear PID control algorithm, so that the convergence speed and the frequency correction precision of the phase-locked loop are improved.
According to the method, a FPGA, OCXO, DAC, GNSS receiver is connected according to the diagram shown in fig. 1, wherein an FPGA is connected with a GNSS receiver through a UART interface, the FPGA also receives PPS signals sent by the GNSS receiver, the FPGA is connected with a DAC through an SPI interface, a DAC voltage output port is connected to a voltage control pin of an OCXO, a clock output of the OCXO is connected to the FPGA, and the FPGA is subjected to pin configuration. In this embodiment, the GNSS receiver selects U-Blox F9T, DAC8531, and OCXO frequency 10MHz.
And then, UART function is realized in the FPGA, and a GNSS control module and an NMEA analysis module are designed on the basis, so that the functions of configuring the functions of U-Blox, acquiring UTC time information through NMEA message analysis and the like are respectively realized. And the GNSS control module is used for configuring the U-Blox to use the multi-GNSS system for resolving, so that the accuracy of resolving time is improved.
Setting the output frequency of a PPS signal of U-Blox to 1Hz, dividing the frequency of a 10MHz clock of the OCXO in an FPGA to obtain a local first 1PPS signal PPS_local, and multiplying the frequency of the 10MHz clock OCXO_10M of the OCXO in the FPGA by using a PLL IP core to obtain a 200MHz counting clock clk_200M.
The clock calibration module of the phase locked loop structure is designed according to fig. 2. The digital phase detector is designed to measure the phase difference between the PPS signal and the PPS_local signal by counting clocks through clk_200M and output a first phase difference phase1. And designing a Kalman filter, filtering the first phase difference phase1, and outputting a filtering result as a second phase difference phase2. The register reg is constructed, and after the power-on or at the time of the clock calibration module reset, the second phase difference phase2 at the moment is stored, wherein the phase difference is the initial phase difference phase0 between the PPS signal and the PPS_local. And subtracting the second phase difference phase2 from the initial phase difference phase0 to obtain a phase error err=phase2-phase 0, wherein the phase error err=phase2-phase 0 is used as an input error of the PID module. And constructing a PID module, and calculating according to the phase error err to obtain a control signal u. The DAC control module is constructed to control the output voltage of the DAC8531 through the SPI according to the control signal u. Through the steps, the constructed phase-locked loop structure can carry out negative feedback on the frequency deviation of the OCXO, thereby realizing the calibration of the OCXO frequency and obtaining the OCXO_10M with the frequency precision as high as 5 ppb.
Specifically, for the PID control module, the implementation is performed using a nonlinear PID algorithm as shown in FIG. 3. Designing a nonlinear transformation function g (x), wherein g (x) is an odd function
For the input error err, a transformation result err2 is obtained by calculation with a transformation function g (x). Setting parameter K p ＝0.1，K i ＝0.01，K d =0, by
The control amount u is calculated.
The time synchronization module is designed, as shown in fig. 4 and 5, the working clock can replace ocxo_10m shown in the figure with clk_200m obtained by multiplying frequency of ocxo_10m, and the corresponding cnt_10m is replaced with cnt_200m. The state of the PPS is detected at the rising edge of each clk_200M, the value of the PPS is stored in PPS_reg, if the PPS is detected to be (-PPS_reg) and PPS is high, the rising edge of the PPS is indicated, at the moment, the cnt_200M is set to 0, and the UTC time NMEA_UTC_time obtained by analysis of the NMEA analysis module is registered in a UTC_time register. If no rising edge of PPS is detected at the rising edge of clk_200m, utc_time is kept unchanged while the count value recorded by cnt_200m is self-incremented. Other FPGA functional modules acquire high-precision UTC second-level time by reading UTC_time and acquire high-precision sub-second-level time by cnt_200M. cnt_200m is a time counter in units of 5ns, and the count value of cnt_200m is multiplied by 5ns to obtain high-precision sub-second time, and the resolution of the high-precision time is 5ns.
The time accuracy of the time-frequency calibration synchronization system constructed in this embodiment is analyzed as follows. Since cnt_200m is limited to calculating sub-second time within 1s, the phase accumulation error caused by the frequency error of clk_200m accumulates at most 1s, and since the frequency accuracy of clk_200m is equal to that of ocxo_10m, i.e., 5ppb, the maximum time error caused by the frequency error is 5ppb×1s=5ns. The time error caused by the + -1 count error of clk_200M is equivalent to its time resolution, i.e., 5ns. The maximum time error of the time synchronization system of this embodiment is max {5ns,5ns } = 5ns.
The foregoing is merely illustrative of the preferred embodiments of the present invention and is not intended to limit the embodiments and scope of the present invention, and it should be appreciated by those skilled in the art that equivalent substitutions and obvious variations may be made using the teachings of the present invention, which are intended to be included within the scope of the present invention.
Claims (9)
1. The high-precision time-frequency calibration and synchronization system based on the multi-source GNSS is characterized by comprising a GNSS control module, an NMEA analysis module, a clock calibration module and a time synchronization module;
the GNSS control module is connected with the GNSS receiver, changes the working state of the GNSS receiver by sending an instruction, and switches the selected GNSS system;
the NMEA analysis module receives an NMEA message given by the GNSS receiver, and analyzes the message to obtain UTC time, longitude and latitude information and satellite attitude information;
the clock calibration module takes a PPS signal given by the GNSS receiver as a reference, compares a phase difference with a local first PPS signal obtained by frequency division of the constant temperature crystal oscillator OCXO, adjusts the frequency of the constant temperature crystal oscillator OCXO, and obtains a local clock source; the calibration and synchronization method specifically comprises the following steps:
the clock calibration module adopts a phase-locked loop structure and comprises a frequency divider, a frequency multiplier, a digital phase discriminator, a Kalman filter, a PID module and a DAC control module;
the frequency divider divides the frequency of a clock from the local constant temperature crystal oscillator OCXO to obtain a local first PPS signal;
the frequency multiplier multiplies the clock from the local constant temperature crystal oscillator OCXO to obtain a high-frequency phase discrimination clock;
the digital phase discriminator compares the phase difference between a first PPS signal from the GNSS and a local first PPS signal, and obtains a phase difference first phase difference between the two PPS signals by counting a high-frequency phase discrimination clock;
the Kalman filter filters the first phase difference, eliminates phase jitter, and outputs a second phase difference of a filtering result;
the PID module receives the phase error err and calculates and outputs a control signal through a PID algorithm;
the DAC control module adjusts the output voltage of the DAC according to the control signal, so that the output frequency of the local constant-temperature crystal oscillator OCXO is adjusted;
the PID algorithm based on error nonlinear transformation comprises the following steps: firstly, carrying out nonlinear transformation on an input error e (t) to obtain epsilon (t), then respectively carrying out proportional, integral and differential operations on epsilon (t), and carrying out weighted summation operation on the epsilon (t) and the epsilon (t) to obtain a control quantity u (t);
the time synchronization module acquires UTC second-level time by combining the UTC time information acquired by the NMEA analysis module with the PPS signal, and acquires sub-second-level time resolution by utilizing a local clock source given by the clock calibration module.
2. The high-precision time-frequency calibration and synchronization system based on multi-source GNSS according to claim 1, wherein the GNSS control module receives the upper computer instruction, selects the corresponding control instruction ID according to the instruction, then uses the control instruction ID to acquire the content of the GNSS control instruction in the ROM storing the GNSS instruction, and sends the content to the GNSS receiver through the communication interface, thereby realizing the functions of switching different GNSS systems, saving/resetting configuration and setting NMEA output message types.
3. The multi-source GNSS-based high precision time frequency calibration and synchronization system of claim 1 wherein the NMEA parsing module receives NMEA messages from the GNSS receiver and parses the NMEA messages to obtain UTC time, longitude and latitude, altitude information.
4. The multi-source GNSS based high precision time frequency calibration and synchronization system of claim 1 wherein the time synchronization module input interface comprises: the PPS signal, the NMEA analysis module analyzes the obtained time information NMEA_UTC_time and the clock signal OCXO_10M of the constant-temperature crystal oscillator OCXO; the output signal includes: UTC time utc_time, OCXO clock count cnt_10m from PPS rising edge; NMEA_UTC_time, UTC_time is the sum of a set of signals, including UTC year/monta/day, UTC hh/mm/ss.
5. The method of high-precision time-frequency calibration and synchronization system based on multi-source GNSS according to any one of claims 1-4, wherein based on phase-locked loop structure, PPS second pulse signals given by single or multiple navigation system GNSS are used as reference standard, and FPGA control is used to calibrate voltage-controlled constant temperature crystal oscillator OCXO, so as to obtain clock source.
6. The method of multi-source GNSS based high precision time frequency calibration and synchronization system of claim 5 wherein the FPGA controlled core algorithm comprises: digital phase discrimination algorithm, kalman-PID joint control algorithm and nonlinear PID control algorithm.
7. The method of claim 5, wherein the method configures the GNSS receiver by an FPGA and selects one or more GNSS signal sources according to user requirements.
8. The method of claim 7, wherein the GNSS signal sources include beidou, GPS, gnonas, and galileo systems.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor performs the steps of the method for multi-source GNSS based high precision time frequency calibration and synchronization system as claimed in claim 5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310013411.3A CN116027242B (en) | 2023-01-05 | 2023-01-05 | High-precision time-frequency calibration and synchronization system and method based on multi-source GNSS |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310013411.3A CN116027242B (en) | 2023-01-05 | 2023-01-05 | High-precision time-frequency calibration and synchronization system and method based on multi-source GNSS |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN116027242A CN116027242A (en) | 2023-04-28 |
| CN116027242B true CN116027242B (en) | 2024-02-13 |
Family
ID=86079069
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310013411.3A Active CN116027242B (en) | 2023-01-05 | 2023-01-05 | High-precision time-frequency calibration and synchronization system and method based on multi-source GNSS |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116027242B (en) |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102159968A (en) * | 2008-09-22 | 2011-08-17 | 施克莱无线公司 | Method and apparatus for a global navigation satellite system receiver coupled to a host computer system |
| CN102566410A (en) * | 2012-02-16 | 2012-07-11 | 北京华力创通科技股份有限公司 | Method and device for calibrating local clock based on satellite time service |
| CN102611516A (en) * | 2012-01-17 | 2012-07-25 | 成都府河电力自动化成套设备有限责任公司 | Method and device for generating high-precision synchronous clock |
| CN104199278A (en) * | 2014-09-04 | 2014-12-10 | 中国科学院测量与地球物理研究所 | Multi-navigation-system based anti-occlusion high-accuracy synchronous clock system and synchronous method thereof |
| CN104330966A (en) * | 2014-10-22 | 2015-02-04 | 中国人民解放军信息工程大学 | Multi-mode high-precision time and frequency standard equipment |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI540444B (en) * | 2015-07-31 | 2016-07-01 | 晨星半導體股份有限公司 | Transport stream processor capable of timing calibration, and timing calibration device and method |
| US9927831B2 (en) * | 2015-08-25 | 2018-03-27 | Pixart Imaging Inc. | Navigation system and clock calibration method thereof |
| JP6674171B2 (en) * | 2016-02-10 | 2020-04-01 | 国立研究開発法人情報通信研究機構 | Synchronization deviation detection method between communication stations |
-
2023
- 2023-01-05 CN CN202310013411.3A patent/CN116027242B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102159968A (en) * | 2008-09-22 | 2011-08-17 | 施克莱无线公司 | Method and apparatus for a global navigation satellite system receiver coupled to a host computer system |
| CN102611516A (en) * | 2012-01-17 | 2012-07-25 | 成都府河电力自动化成套设备有限责任公司 | Method and device for generating high-precision synchronous clock |
| CN102566410A (en) * | 2012-02-16 | 2012-07-11 | 北京华力创通科技股份有限公司 | Method and device for calibrating local clock based on satellite time service |
| CN104199278A (en) * | 2014-09-04 | 2014-12-10 | 中国科学院测量与地球物理研究所 | Multi-navigation-system based anti-occlusion high-accuracy synchronous clock system and synchronous method thereof |
| CN104330966A (en) * | 2014-10-22 | 2015-02-04 | 中国人民解放军信息工程大学 | Multi-mode high-precision time and frequency standard equipment |
Non-Patent Citations (4)
| Title |
|---|
| Development of ground-based ELF/VLF receiver system in Wuhan and its first results;Yanping Chen等;Advances in Space Research;全文 * |
| PID自动控制技术在时频传输收发机中的应用;赵卓泽;中国优秀硕士学位论文全文数据库信息科技辑;全文 * |
| 导航、电子对抗、制导;中国无线电电子学文摘(04);全文 * |
| 甚低频接收机的开发与应用;刘卿等;现代电子技术;全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN116027242A (en) | 2023-04-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN100583685C (en) | Method for improving satellite time synchronism pulse keeping performance | |
| CN1904642B (en) | Apparatus and method for compensating the drift of a local clock used as sampling frequency | |
| CN102291169B (en) | Onboard high-accuracy time synchronization method for satellite | |
| CN102474410B (en) | High-precision synchronisation method and system | |
| SE518565C2 (en) | Normal frequency generator | |
| CN105549379A (en) | Synchronous measurement apparatus based on high precision time reference triggering and method thereof | |
| CN107505832B (en) | A kind of high-precision time dissemination system | |
| CN109525351A (en) | A kind of equipment for realizing time synchronization with time reference station | |
| CN109085616B (en) | Satellite time service method, device and storage medium | |
| CN104300969B (en) | A kind of high-precise synchronization clock implementation method based on all-digital phase-locked loop | |
| CN100395682C (en) | 'Beidou No.1' satellite navigation system and GPS mutually preparing time service method and apparatus | |
| CN105867107A (en) | Low-power high-precision time service system | |
| CN204631463U (en) | A kind of gps clock synchro system of radiation source Monitoring and Positioning | |
| CN105049040A (en) | Method for correcting output frequency of CPT (Coherent Population Trapping) atomic clock through GNSS(Global Navigation Satellite System) | |
| CN111208727A (en) | High-precision satellite pulse-per-second synchronous time keeping device and method | |
| CN108768577B (en) | Communication network time service method and system based on PTP time synchronization signal | |
| Exel et al. | Improved clock synchronization accuracy through optimized servo parametrization | |
| CN102253638A (en) | Frequency stability control and compensation method for automatically keeping time in complex environment | |
| CN113848568A (en) | Time correction system and method | |
| CN106383438B (en) | One kind taming and dociling clock method based on sliding window time extension high-precision | |
| CN100535824C (en) | Method of improving satellite time synchronuos pulse holding performance | |
| CN106292268B (en) | Time service terminal device and pulse per second (PPS) based on GNSS receiver tame method | |
| CN116027242B (en) | High-precision time-frequency calibration and synchronization system and method based on multi-source GNSS | |
| CN112969229B (en) | Clock correction method and device and network equipment | |
| CN111010174B (en) | Method and circuit for improving time-keeping metering precision |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |