Time keeping method for taming local clock

Abstract

The invention relates to the technical field of time frequency, and particularly discloses a time keeping method for taming a local clock, which comprises the following steps: acquiring a reference signal and a clock signal of the local clock; when the reference signal is locked, determining a clock difference between the clock signal at room temperature and the reference signal by using a time interval counter; adjusting the control voltage of the local clock according to the clock difference to change the frequency of the local clock, so that the clock signal is synchronized with the reference signal; obtaining the temperature through a temperature sensor; when the reference signal loses lock, the aging coefficient and the temperature coefficient of the local clock are solved through the Gaussian Seidel iteration temperature and the clock difference, and the clock signal is adjusted according to the aging coefficient, the temperature coefficient and the real-time temperature obtained through the temperature sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of time and frequency, and particularly relates to a time keeping method for taming a local clock. Background Art

[0002] With the development of atomic frequency standard technology, in recent years, large domestic and foreign time and frequency systems have high costs and harsh operating environments, which limit their applications in various fields. Relatively speaking, local clocks with price advantages have become the first choice. However, local clocks have problems of frequency offset and aging, and cannot meet the accuracy requirements of the system. Therefore, it is necessary to tame the local clock to maintain a high accuracy for a long time.

[0003] Currently, the time synchronization methods of time and frequency standards are evolving from technical means such as short waves, long waves, and televisions to navigation satellites. The main principle of using navigation satellites for time synchronization is to receive satellite signals through a navigation satellite signal receiving module, and realize system timekeeping and network clock synchronization according to the 1PPS (Pulse Per Second) signal in the received navigation satellite signals. Since the time synchronization of navigation satellites requires very high accuracy, and the circuits in the navigation satellite time synchronization system are directly exposed to the external environment, their parameter values are easily affected by the environmental temperature, resulting in unreliable time synchronization, which is very fatal to a high-precision time synchronization system.

[0004] The existing methods for taming local clocks in the prior art often have the following disadvantages: 1) When estimating the aging coefficient of the crystal oscillator, the influence of temperature is ignored, resulting in inaccurate aging coefficients; 2) Using temperature control devices such as incubators to keep the temperature constant, resulting in high costs; 3) Without considering the influence of temperature, it is only suitable for constant temperature environments, and the applicable range is small; 4) Using a BP neural network model, the calculation amount is large, and it is not applicable to local clocks with weak computing capabilities.

[0005] Therefore, there is an urgent need for a time keeping method for taming local clocks that does not use an incubator and can tame local clocks in an environment with temperature changes. Summary of the Invention

[0006] In view of the above problems, the object of the present invention is to provide a time keeping method for taming a local clock, which solves the temperature coefficient and aging coefficient by Gauss-Seidel iteration, and realizes taming the local clock in an environment with temperature changes.

[0007] The present invention provides a time keeping method for taming a local clock, including: Obtaining a reference signal and a clock signal of the local clock; When the reference signal is locked, a time interval counter is used to determine the clock difference between the clock signal at room temperature and the reference signal; Adjust the control voltage of the local clock according to the clock difference to change the frequency of the local clock, so that the clock signal is synchronized with the reference signal; Obtain the temperature through a temperature sensor; When the reference signal is unlocked, the aging coefficient and temperature coefficient of the local clock are solved by Gauss-Seidel iteration of the temperature and the clock difference, so as to adjust the clock signal according to the aging coefficient, temperature coefficient and the real-time temperature obtained by the temperature sensor.

[0008] In a possible implementation manner, the solving of the aging coefficient and temperature coefficient of the local clock by Gauss-Seidel iteration of the temperature and the clock difference includes: Obtain a preset first coefficient matrix, a preset second coefficient matrix, a clock difference and a frequency difference; According to the preset first coefficient matrix, the clock difference, and the temperature clock difference caused by temperature in the th iteration, solve the aging coefficient in the th iteration; where is a positive integer; Determine the aging clock difference in the th iteration according to the preset first coefficient matrix and the aging coefficient in the th iteration; Determine the aging frequency difference in the th iteration according to the aging clock difference in the th iteration and a preset value; Solve the temperature coefficient according to the preset second coefficient matrix, the aging frequency difference in the th iteration, and the frequency difference; Calculate the temperature frequency difference and temperature clock difference caused by temperature according to the temperature coefficient; Subtract the aging clock difference and the temperature clock difference from the clock difference to obtain a test value; When the test value is less than a preset threshold, output the aging coefficient and temperature coefficient; When the test value is greater than or equal to the preset threshold, re-solve the aging coefficient and temperature coefficient.

[0009] In a possible implementation manner, the clock difference of the local clock is calculated according to the following formula : ; In the formula, is the clock difference at moment, is The aging clock difference caused by aging at a certain moment is the temperature clock difference caused by the temperature at a certain moment.

[0010] In a possible implementation, it is calculated according to the following formula the aging clock difference caused by aging at a certain moment: ; In the formula, is the aging clock difference caused by aging at a certain moment, is the error at the initial time, represents the relative frequency deviation, is the frequency aging rate.

[0011] In a possible implementation, the temperature frequency difference caused by temperature is calculated according to the following formula: ; In the formula, is the temperature frequency difference caused by the temperature at a certain moment, is the frequency error caused by the initial temperature, represents the temperature coefficient.

[0012] In a possible implementation, the aging coefficient and temperature coefficient of the local clock are solved according to the following formula: ; In the formula, is the preset first coefficient matrix, is the preset second coefficient matrix, is the number of iterations, is the clock difference, is the frequency difference, represents the th aging coefficient of the Gauss-Seidel iteration, represents the th temperature coefficient of the Gauss-Seidel iteration, is the temperature clock difference caused by temperature at the th iteration, is the frequency difference vector caused by aging at the th iteration.

[0013] In a possible implementation, the preset first coefficient matrix is determined according to the following formula : ; In the formula, is the sampling moment, , is a positive integer.

[0014] In a possible implementation, the preset second coefficient matrix is determined according to the following formula : ; In the formula, is the temperature at time , and n is a positive integer

[0015] In a possible implementation, the local clock is a constant temperature crystal oscillator, a voltage controlled crystal oscillator or an atomic clock

[0016] In a possible implementation, the reference signal is a global navigation satellite system (GNSS) signal, a base station signal, a long wave time service signal or a short wave time service signal

[0017] The time keeping method for taming a local clock provided by the present invention has the following technical effects 1) Without using an incubator, the time keeping of the local clock can be tamed in an environment with temperature changes; it can be used under room temperature conditions, which can reduce the cost of time keeping, reduce the quality and volume of the local clock, and expand the applicable range 2) Through simple Gauss-Seidel iteration, the temperature coefficient and the aging coefficient can be obtained more accurately, and the separation of the two is realized, and the calculation amount is small 3) Time keeping is realized. When the reference signal is out of lock, the time synchronization between the local clock and the reference signal can be continued in a short time 4) Compared with directly obtaining the aging coefficient by ignoring the influence of temperature, the result is more accurate Description of the Drawings

[0018] Figure 1 is a schematic flowchart of the time keeping method provided by an embodiment of the present invention Figure 2 is an algorithm flowchart of the time keeping method provided by an embodiment of the present invention Detailed Embodiments

[0019] The following further describes in detail the embodiments of the present invention in conjunction with the drawings and embodiments. The detailed description and drawings of the following embodiments are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described preferred embodiments, and the scope of the present invention is defined by the claims

[0020] In the description of the present invention, it should be noted that unless otherwise specified, the meaning of "a plurality of" is two or more; the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; for those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] Figure 1 It is a schematic flowchart of the time keeping method provided by the embodiment of the present invention. As Figure 1 shown, the time keeping method for taming a local clock provided by the present invention includes: Step S1, obtaining a reference signal and a clock signal of a local clock; In a possible implementation manner, the local clock is an oven controlled crystal oscillator, a voltage controlled crystal oscillator or an atomic clock.

[0022] In a possible implementation manner, the reference signal is a global navigation satellite system (GNSS) signal, a base station signal, a long wave time service signal or a short wave time service signal.

[0023] Step S2, when the reference signal is locked, using a time interval counter to determine the clock difference between the clock signal at room temperature and the reference signal; Step S3, adjusting the control voltage of the local clock according to the clock difference to change the frequency of the local clock so that the clock signal is synchronized with the reference signal; Step S4, obtaining the temperature through a temperature sensor; Step S5, when the reference signal is unlocked, solving the aging coefficient and temperature coefficient of the local clock through Gauss-Seidel iteration of temperature and clock difference, so as to adjust the clock signal according to the aging coefficient, temperature coefficient and the real-time temperature obtained by the temperature sensor.

[0024] In a possible implementation manner, solving the aging coefficient and temperature coefficient of the local clock through Gauss-Seidel iteration of temperature and clock difference includes: Obtaining a preset first coefficient matrix, a preset second coefficient matrix, a clock difference and a frequency difference; According to the preset first coefficient matrix, the clock difference, and the temperature clock difference caused by temperature in the th iteration, solving the aging coefficient in the th iteration; where is a positive integer; Determining the aging clock difference in the th iteration according to the preset first coefficient matrix and the aging coefficient in the th iteration; According to the aging clock difference in the th iteration and a preset value, determining the aging frequency difference in the th iteration; Solve for the temperature coefficient based on the preset second coefficient matrix, the aging frequency difference of the nth iteration, and the frequency difference solution temperature coefficient; Calculate the temperature frequency difference and temperature clock error caused by temperature according to the temperature coefficient; Subtract the aging clock error and temperature clock error from the clock error to obtain the test value; When the test value is less than the preset threshold, output the aging coefficient and temperature coefficient; When the test value is greater than or equal to the preset threshold, re-solve the aging coefficient and temperature coefficient.

[0025] In a possible implementation, in addition to using the least squares method to solve the temperature coefficient and aging coefficient during the iteration process, the present invention can also use methods such as gradient descent and machine learning to solve the temperature coefficient and aging coefficient.

[0026] In a possible implementation, calculate the clock error of the local clock according to the following formula : ; where is the clock error at time is the aging clock error caused by aging at time and is the temperature clock error caused by temperature at time.

[0027] In a possible implementation, the short-term frequency stability of the local clock is good, with an obvious frequency drift, and the lock loss time of the reference signal will not be too long. A quadratic polynomial is selected for clock error fitting under constant temperature conditions, and the following formula is used to calculate the aging clock error caused by aging at time: ; where is the aging clock error caused by aging at time, is the error at the initial time, represents the relative frequency deviation, is the frequency aging rate.

[0028] In a possible implementation, considering the frequency-temperature curve as linear, calculate the temperature frequency difference caused by temperature according to the following formula: ; where is the temperature frequency difference caused by temperature at time, is the frequency error caused by the initial temperature, represents the temperature coefficient. ​

[0029] The directly obtainable data in reality is discrete clock offset, and the relationship between clock offset and frequency offset is as follows: ; ; In the formula, is the clock offset at the th moment, is the frequency offset at the th moment, is the sampling time interval; In a possible implementation, based on the obtained n groups of discrete data ( , , ), , the aging coefficient and temperature coefficient of the local clock are solved according to the following formula: ; In the formula, is the preset first coefficient matrix, is the preset second coefficient matrix, is the number of iterations, is the clock offset, is the clock offset at the th moment, is the frequency offset, is the frequency offset at the th moment, represents the aging coefficient of the th Gauss-Seidel iteration, represents the temperature coefficient of the th Gauss-Seidel iteration.

[0030] is the temperature clock offset caused by temperature at the th iteration, where, , is the frequency offset vector caused by aging at the th iteration.

[0031] In a possible implementation, the preset first coefficient matrix is determined according to the following formula: ; In the formula, is the sampling moment, , is a positive integer.

[0032] In a possible implementation, the preset second coefficient matrix is determined according to the following formula: ; In the formula, is the temperature at time , and

[0033] Figure 2 is the algorithm flowchart of the time keeping method provided by the embodiment of the present invention. As Figure 2 shown, the present invention is solved according to the following algorithm.

[0034] 1) Initialize the data, and let = 0; 2) Input historical data. Input clock error , frequency difference , preset first coefficient matrix and preset second coefficient matrix ; 3) Solve the aging coefficient . Use the formula to solve ; 4) Calculate . Use the aging coefficient to calculate the clock error and frequency difference caused by aging; 5) Solve the temperature coefficient . Use the formula to solve ; 6) Calculate . Use the temperature coefficient to calculate the frequency difference and clock error vector caused by temperature; 7) Judge whether to terminate. If and are not satisfied, then , and return to step 3); otherwise, end the loop and output the aging coefficient and temperature coefficient.

[0035] The time keeping method for taming a local clock provided by the present invention has the following technical effects: 1) Without using an incubator, it can tame the time keeping of a local clock in an environment with changing temperatures; when used at room temperature, it can reduce the cost of time keeping, reduce the quality and volume of the local clock, and expand the scope of application; 2) Through simple Gauss-Seidel iteration, the temperature coefficient and aging coefficient can be obtained relatively accurately, and the separation of the two is achieved, and the calculation amount is small; 3) Timekeeping is achieved. When the reference signal loses lock, the time synchronization between the local clock and the reference signal can continue to be achieved within a short time. 4) Compared with directly obtaining the aging coefficient by ignoring the influence of temperature, the result is more accurate.

[0036] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A time keeping method for taming a local clock, characterized in that: include: Obtaining a reference signal and a clock signal of a local clock; When the reference signal is locked, determining the clock difference between the clock signal at room temperature and the reference signal using a time interval counter; adjusting a control voltage of the local clock according to the clock difference to change the frequency of the local clock so that the clock signal is synchronized with the reference signal; Get the temperature through the temperature sensor; When the reference signal is unlocked, the aging coefficient and temperature coefficient of the local clock are solved by Gauss-Seidel iteration of the temperature and the clock difference, so as to adjust the clock signal according to the aging coefficient, temperature coefficient and the real-time temperature obtained by the temperature sensor.

2. The time keeping method according to claim 1, characterized in that: The step of solving the aging coefficient and the temperature coefficient of the local clock by using Gauss-Seidel iteration of the temperature and the clock difference comprises: Obtaining a preset first coefficient matrix, a preset second coefficient matrix, a clock difference, and a frequency difference; According to the preset first coefficient matrix, the clock difference, the The temperature clock difference caused by temperature in the iteration is solved The aging coefficient of the iterations; where, is a positive integer; According to the preset first coefficient matrix and the The aging coefficient of the iteration is determined The aging clock error of iterations; According to the said The aging clock error of the first iteration and the preset value determine the The aging frequency difference of iterations; According to the preset second coefficient matrix, the The aging frequency difference of the iteration, and the temperature coefficient is solved by the frequency difference; Calculate the temperature frequency difference and the temperature clock difference caused by the temperature according to the temperature coefficient; Subtracting the aging clock difference and the temperature clock difference from the clock difference to obtain a test value; When the inspection value is less than a preset threshold, outputting the aging coefficient and the temperature coefficient; When the test value is greater than or equal to the preset threshold, the aging coefficient and the temperature coefficient are re-solved.

3. The time keeping method according to claim 1, characterized in that: The clock difference of the local clock is calculated according to the following formula: : ； In the formula, for The clock difference, for Aging clock error caused by time aging, for Temperature clock difference caused by the temperature at the moment.

4. The time keeping method according to claim 3, characterized in that: Calculate according to the following formula Aging clock error caused by time aging: ； In the formula, for Aging clock error caused by time aging, is the error of the initial time, represents the relative frequency deviation, is the frequency aging rate.

5. The time keeping method according to claim 2, characterized in that: The temperature frequency difference caused by temperature is calculated according to the following formula: ； In the formula, for The temperature frequency difference caused by the temperature at the moment, is the frequency error caused by the initial temperature, Represents the temperature coefficient.

6. The time keeping method according to claim 2, characterized in that: The aging coefficient and temperature coefficient of the local clock are solved according to the following formula: ； In the formula, is the preset first coefficient matrix, To preset the second coefficient matrix, is the number of iterations, For the clock error, is the frequency difference, Indicates The aging coefficient of the sub-Gauss-Seidel iteration, Indicates The temperature coefficient of the Gauss-Seidel iteration, For the The temperature clock difference caused by temperature in the iteration is For the The frequency difference vector caused by aging in the iteration.

7. The time keeping method according to claim 6, characterized in that: The preset first coefficient matrix is ​​determined according to the following formula : ； In the formula, is the sampling time, , Is a positive integer.

8. The time keeping method according to claim 6, characterized in that: The preset second coefficient matrix is ​​determined according to the following formula : ； In the formula, for The temperature of the moment, , Is a positive integer.

9. The time keeping method according to claim 1, characterized in that: The local clock is a constant temperature crystal oscillator, a voltage-controlled crystal oscillator or an atomic clock.

10. The time keeping method according to claim 1, characterized in that: The reference signal is a global navigation satellite system GNSS signal, a base station signal, a long-wave timing signal or a short-wave timing signal.

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