A method and device for improving the autonomous timekeeping capability of a crystal oscillator

Abstract

The present application relates to a method and apparatus for improving the autonomous timekeeping capability of a crystal oscillator. The method comprises: when the crystal oscillator transitions from a tamed state to an autonomous timekeeping state, periodically and slowly changing the DAC value by performing polarization modulation on the value of a digital-to-analog converter (DAC), thereby periodically and slowly changing the DAC value, and thus periodically and slowly changing the voltage control voltage of the crystal oscillator, thereby fine-tuning the crystal oscillator frequency to compensate for the aging rate of the crystal oscillator itself and the phase deviation caused by the frequency-temperature characteristics, thereby significantly improving the autonomous timekeeping capability of the crystal oscillator.

Description

Technical Field

[0001] The present application relates to the technical field of crystal oscillator design, and in particular to a method and device for improving the autonomous timekeeping capability of a crystal oscillator. Background Art

[0002] Crystal oscillators, as frequency components, offer unique advantages such as short-term stability, compact size, and low cost. They are widely used in numerous key industries, including communications, electricity, finance, and transportation. However, due to temperature and aging drift, their long-term stability and accuracy are poor, and they lack the ability to maintain autonomous timekeeping for extended periods. Typically, the 1 Pulse Per Second (1PPS) signal provided by the Global Navigation Satellite System (GNSS) is used to calibrate and train local crystal oscillators to improve their long-term stability and accuracy. However, due to the complex transmission paths of satellite signals, interference, spoofing, or even interruption can cause the GNSS clock reference to be lost, making it impossible to calibrate and train the local crystal oscillator. Over time, the output frequency deviation gradually increases, and phase synchronization can no longer be guaranteed. Therefore, improving the autonomous timekeeping capability of crystal oscillators, ensuring that they can maintain high-precision time synchronization for a certain period of time even when the time and frequency reference source is lost, is a critical issue that must be addressed.

[0003] Traditional methods for improving the autonomous timekeeping capabilities of crystal oscillators often involve building algorithmic models for the aging and temperature drift of the crystal oscillator. For example, multiple Kalman filters are used to process the historical data of the oven-controlled crystal oscillator, adaptively simulating the temperature and aging drift of the oven-controlled crystal oscillator's output frequency for compensation. Alternatively, a neural network-based crystal oscillator frequency prediction algorithm is developed. By training the neural network model with historical measurements of the crystal oscillator's frequency, the drift patterns of the crystal oscillator's frequency are characterized, thereby improving the prediction accuracy of the crystal oscillator's frequency. Regardless of which method is used, both the accumulation of historical crystal oscillator data and the establishment of an algorithmic model for prediction require extensive algorithm code development and are difficult to optimize. Furthermore, this compensation method exhibits a certain degree of lag, making real-time compensation impossible. Summary of the Invention

[0004] Based on this, it is necessary to provide a method and device for improving the autonomous timekeeping capability of a crystal oscillator in response to the above technical problems.

[0005] A method for improving the autonomous timekeeping capability of a crystal oscillator, the method comprising: improving the autonomous timekeeping capability of the crystal oscillator by using a method of periodically polarizing and modulating a DAC value; the DAC value is a control signal of a voltage-controlled terminal of the crystal oscillator, and the specific steps of the method of periodically polarizing and modulating the DAC value include:

[0006] From the moment t0 when the crystal oscillator changes from the taming state to the autonomous timekeeping state, within the time period T1, every first time interval Δt + , increase the DAC value step by step by Δ DAC+ .

[0007] During the T2 period starting from the time t0+T1, every second time interval Δt - , decrease the DAC value step by step by Δ DAC- ; Similarly, the DAC value changes slowly with a period of T=T1+T2.

[0008] The DAC value that changes slowly and periodically is used to change the voltage control voltage of the crystal oscillator, and the crystal oscillator frequency is fine-tuned to compensate for the phase deviation caused by the aging rate of the crystal oscillator itself and the frequency-temperature characteristics, thereby improving the autonomous timing accuracy of the crystal oscillator.

[0009] In one embodiment, T1 and Δt + , T2 and Δt - Satisfaction relationship:

[0010] T1=N*Δt + , N positive integer

[0011] T2=M*Δt - , M is a positive integer

[0012] Where N is the time interval Δt within the T1 period + The number of M is the time interval Δt in the T2 period - The number of

[0013] In one embodiment, the parameter combination (M, N; Δt + , Δt - ; Δ DAC+ , Δ DAC- ) includes the following steps:

[0014] Step 1: Set the initial value of the parameter combination so that the parameter combination satisfies M=N, Δt + =Δt - , Δ DAC+ =Δ DAC- , and obtain the initial curve of the change law of the crystal oscillator output phase difference over time.

[0015] Step 2: If the initial curve of the crystal oscillator output phase difference over time is flat, determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- )value.

[0016] Step 3: If the initial curve of the crystal oscillator output phase difference over time is not straight, first keep M = N, Δ DAC+ =Δ DAC- Fixed, by adjusting Δt + and\or Δt - Adjust the output phase difference of the crystal oscillator to obtain the time-varying regularity curve; observe whether the output phase difference of the crystal oscillator is flat; if it is flat, determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ) value; if it is not straight, continue to + and\or Δt - Adjust. If the adjustment times are less than the preset maximum cycle threshold and the curve of the crystal oscillator output phase difference changing with time is flat, stop adjusting and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ) value; if the phase difference over time curve does not reach a flat line when the preset maximum cycle threshold is reached, then keep M = N, Δt + =Δt - Fixed, by DAC+ and\or Δ DAC- Adjust until the crystal oscillator output phase difference changes with time and the curve is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- )value.

[0017] In one embodiment, when the initial curve of the variation law of the crystal oscillator output phase difference over time is open upward: step 3 specifically includes:

[0018] First, keep M=N, Δ DAC+ =Δ DAC- Fixed by reducing Δt + , increase Δt - Or reduce Δt + At the same time, add the Δt adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat.

[0019] If the curve of the crystal oscillator output phase difference changing with time is straight, then the parameter combination is determined as (M, N; Δt + , Δt - ; Δ DAC+ , Δ DAC- ).

[0020] If the curve of the crystal oscillator output phase difference over time still opens upward, continue to reduce Δt + , increase Δt - Or reduce Δt + At the same time, increase the Δt adjustment method to adjust until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time opens downward, then by increasing Δt + , reduce Δt - Or increase Δt + While reducing Δt - Continue to adjust in the same way.

[0021] If the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0022] If the curve of the crystal oscillator output phase difference changing with time is not straight when the cycle adjustment number threshold is reached, then keep M=N, Δt + =Δt - Fixed by reducing Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; if the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination is determined to be (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0023] If the curve of the crystal oscillator output phase difference over time still opens upward, continue to reduce Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC-); if the curve opens downward, increase Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0024] In one embodiment, when the initial curve of the variation law of the crystal oscillator output phase difference over time is open downward: step 3 specifically includes:

[0025] First, keep M=N, Δ DAC+ =Δ DAC- Fixed, by increasing Δt + , reduce Δt - Or increase Δt + , while reducing Δt - Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat.

[0026] If the curve of the crystal oscillator output phase difference changing with time is straight, then the parameter combination is determined as (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0027] If the curve of the crystal oscillator output phase difference over time still opens downward, continue to increase Δt + , reduce Δt - Or increase Δt + , while reducing Δt - If the cycle adjustment number threshold is not reached and the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the cycle adjustment number threshold is not reached and the curve of the crystal oscillator output phase difference over time opens upward, then reduce Δt + , increase Δt - Or reduce Δt + While increasing Δt - Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt- , Δ DAC+ , Δ DAC- ).

[0028] If the crystal oscillator output phase difference curve over time is not straight when the cycle adjustment number threshold is reached, then maintain Δt + =Δt - Fixed by increasing Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; if the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination is determined to be (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time still opens downward, continue to increase Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method until the crystal oscillator output phase difference changes smoothly with time, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time opens upward, then by reducing Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Continue to adjust in this way until the phase difference of the crystal oscillator output changes smoothly with time, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0029] In one embodiment, the DAC value at any time t0+k*T satisfies the relationship:

[0030] DAC(t0+k*T)=DAC0+k*(N*Δ DAC+ -M*Δ DAC- )

[0031] Wherein, k is a positive integer.

[0032] In one embodiment, when Δt + =Δt -By setting T1, T2, Δ DAC+ and Δ DAC- Improve the autonomous timekeeping capability of the crystal oscillator.

[0033] A device for improving the autonomous timekeeping capability of a crystal oscillator, the device is used to improve the autonomous timekeeping capability of the crystal oscillator by using a method of periodically polarizing and modulating a DAC value; the DAC value is a control signal of a voltage-controlled terminal of the crystal oscillator, and the specific steps of the method of periodically polarizing and modulating the DAC value include: starting from the moment t0 when the crystal oscillator changes from a tamed state to an autonomous timekeeping state, within a time period T1, every first time interval Δt + , increase the DAC value step by step by Δ DAC+ ; During the T2 period starting from the time t0+T1, every second time interval Δt - , decrease the DAC value step by step by Δ DAC- ; Similarly, the DAC value changes slowly with a period of T=T1+T2; the voltage-controlled voltage of the crystal oscillator is changed by using the periodically slowly changing DAC value, and the crystal oscillator frequency is fine-tuned to compensate for the phase deviation caused by the aging rate of the crystal oscillator itself and the frequency-temperature characteristics, thereby improving the autonomous timing accuracy of the crystal oscillator.

[0034] The above-mentioned method and device for improving the autonomous timekeeping capability of the crystal oscillator, when the crystal oscillator is transferred from the tamed state to the autonomous timekeeping state, periodically polarizes the value of the digital-to-analog converter DAC to slowly and periodically change the DAC value, thereby slowly and periodically changing the voltage-controlled voltage of the crystal oscillator, and fine-tuning the crystal oscillator frequency to compensate for the aging rate of the crystal oscillator itself and the phase deviation caused by the frequency-temperature characteristics, which significantly improves the autonomous timekeeping capability of the crystal oscillator. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram showing the crystal oscillator transitioning from a tamed state to an autonomous timekeeping state;

[0036] Figure 2 1 is a flow chart of a method for improving the autonomous timekeeping capability of a crystal oscillator in one embodiment;

[0037] Figure 3 A schematic diagram of another embodiment for improving the autonomous timekeeping capability of a crystal oscillator;

[0038] Figure 4 1. A graph showing the change in DAC value and output phase difference in another embodiment of the crystal oscillator in autonomous timing mode;

[0039] Figure 5 In another embodiment, the crystal oscillator is in autonomous timekeeping state, and the DAC value is modulated by periodic polarization (M=N=150; Δt + =Δt - =1,Δ DAC+ =Δ DAC-=1), short-term output phase difference result diagram;

[0040] Figure 6 In another embodiment, the crystal oscillator is in autonomous timekeeping state, and the DAC value is modulated by periodic polarization (M=N=10; Δt + =Δt - =1,Δ DAC+ =Δ DAC- =16), long-term output phase difference result diagram;

[0041] Figure 7 In another embodiment, the crystal oscillator is in autonomous timekeeping state, and the DAC value is modulated by periodic polarization (M=N=10; Δt + =Δt - =1,Δ DAC+ =Δ DAC- =16), short-term output phase difference result diagram. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0043] The traditional crystal oscillator training process consists of a time interval counter (TIC), Kalman filter, proportional integral derivative (PID) control, digital-to-analog converter (DAC) and crystal oscillator to form a training loop, such as Figure 1 As shown in the figure, a time interval counter (TIC) measures the time difference between the 1PPS output of the crystal oscillator and the reference 1PPS. Kalman filtering and proportional-integral-differential (PID) control process this time difference, outputting a digital value representing the time difference. This digital value is converted into an analog control voltage by a digital-to-analog converter (DAC). This voltage is applied to the voltage control terminal of the crystal oscillator, thereby correcting the crystal oscillator's 1PPS to ensure that it fully follows the external reference 1PPS. If the external reference is interrupted, the time interval counter (TIC), Kalman filtering, and proportional-integral-differential (PID) control will not function. Therefore, by changing the DAC value, the phase difference caused by the crystal oscillator's aging and temperature drift can be compensated, thereby improving the crystal oscillator's autonomous timing capability.

[0044] By studying the influence of the gradual increase and decrease of the DAC value output by the digital-to-analog converter on the phase difference of the crystal oscillator output, it is clarified that the gradual increase of the DAC value leads to the gradual increase of the crystal oscillator output phase difference, and the gradual decrease of the DAC value leads to the gradual decrease of the crystal oscillator output phase difference. The two are the rules with opposite polarity and approximately equal amplitude; the influence of the periodic polarization modulation DAC value on the crystal oscillator output phase difference is studied, that is, in a period of time, the DAC value gradually increases, and then in another period of time the DAC value gradually decreases. It is clarified that the periodic polarization modulation DAC value can achieve the stability of the crystal oscillator output phase difference.

[0045] In one embodiment, Figure 2 As shown, a method for improving the autonomous timekeeping capability of a crystal oscillator is provided, the method comprising: improving the autonomous timekeeping capability of the crystal oscillator by using a method of periodically polarizing and modulating a DAC value; the DAC value is a control signal of a voltage-controlled terminal of the crystal oscillator, and the specific steps of the method of periodically polarizing and modulating the DAC value include:

[0046] Step 100: From the moment t0 when the crystal oscillator changes from the taming state to the autonomous timekeeping state, within the time period T1, every first time interval Δt + , increase the DAC value step by step by Δ DAC+ .

[0047] Step 102: During the time period T2 starting from the time t0+T1, every second time interval Δt - , decrease the DAC value step by step by Δ DAC- ; Similarly, the DAC value changes slowly with a period of T=T1+T2.

[0048] Step 104: Use the periodically and slowly changing DAC value to change the voltage control voltage of the crystal oscillator, fine-tune the crystal oscillator frequency to compensate for the phase deviation caused by the aging rate of the crystal oscillator itself and the frequency-temperature characteristics, and improve the autonomous timing accuracy of the crystal oscillator.

[0049] The schematic diagram for improving the crystal oscillator's autonomous timekeeping capability is as follows: Figure 3 shown.

[0050] In the above-mentioned method for improving the autonomous timekeeping ability of the crystal oscillator, when the crystal oscillator is transferred from the tamed state to the autonomous timekeeping state, the value of the digital-to-analog converter DAC is periodically polarized modulated, the DAC value is periodically and slowly changed, and then the voltage-controlled voltage of the crystal oscillator is periodically and slowly changed, and the crystal oscillator frequency is fine-tuned to compensate for the aging rate of the crystal oscillator itself and the phase deviation caused by the frequency-temperature characteristics, which significantly improves the autonomous timekeeping ability of the crystal oscillator.

[0051] In one embodiment, when the periodic polarization modulation DAC value method is used, T1 and Δt + , T2 and Δt - Satisfaction relationship:

[0052] T1=N*Δt + , N positive integer

[0053] T2=M*Δt - , M is a positive integer

[0054] Where N is the time interval Δt within the T1 period + The number of M is the time interval Δt in the T2 period - The number of

[0055] In one embodiment, the parameter combination (M, N; Δt + , Δt - ; Δ DAC+ , Δ DAC- ) includes the following steps:

[0056] Step 1: Set the initial value of the parameter combination so that the parameter combination satisfies M=N, Δt + =Δt - , Δ DAC+ =Δ DAC- , and obtain the initial curve of the change law of the crystal oscillator output phase difference over time.

[0057] Step 2: If the initial curve of the crystal oscillator output phase difference over time is flat, determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- )value.

[0058] Step 3: If the initial curve of the crystal oscillator output phase difference over time is not straight, first keep M = N, Δ DAC+ =Δ DAC- Fixed, by adjusting Δt + and\or Δt - Adjust the output phase difference of the crystal oscillator to obtain the time-varying regularity curve; observe whether the output phase difference of the crystal oscillator is flat; if it is flat, determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ) value; if it is not straight, continue to + and\or Δt - Adjust. If the adjustment times are less than the preset maximum cycle threshold and the curve of the crystal oscillator output phase difference changing with time is flat, stop adjusting and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC-) value; if the phase difference over time curve does not reach a flat line when the preset maximum cycle threshold is reached, then keep M = N, Δt + =Δt - Fixed, by DAC+ and\or Δ DAC- Adjust until the crystal oscillator output phase difference changes with time and the curve is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- )value.

[0059] In one embodiment, when the initial curve of the variation law of the crystal oscillator output phase difference over time is open upward: step 3 specifically includes:

[0060] First, keep M=N, Δ DAC+ =Δ DAC- Fixed by reducing Δt + , increase Δt - Or reduce Δt + At the same time, add the Δt adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat.

[0061] If the curve of the crystal oscillator output phase difference changing with time is straight, then the parameter combination is determined as (M, N; Δt + , Δt - ; Δ DAC+ , Δ DAC- ).

[0062] If the curve of the crystal oscillator output phase difference over time still opens upward, continue to reduce Δt + , increase Δt - Or reduce Δt + At the same time, increase the Δt adjustment method to adjust until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time opens downward, then by increasing Δt + , reduce Δt - Or increase Δt + While reducing Δt - Continue to adjust in the same way.

[0063] If the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination (M, N; Δt + , Δt -, Δ DAC+ , Δ DAC- ).

[0064] If the curve of the crystal oscillator output phase difference changing with time is not straight when the cycle adjustment number threshold is reached, then keep M=N, Δt + =Δt - Fixed by reducing Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; if the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination is determined to be (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0065] If the curve of the crystal oscillator output phase difference over time still opens upward, continue to reduce Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); if the curve opens downward, increase Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0066] In one embodiment, when the initial curve of the variation law of the crystal oscillator output phase difference over time is open downward: step 3 specifically includes:

[0067] First, keep M=N, Δ DAC+ =Δ DAC- Fixed, by increasing Δt + , reduce Δt - Or increase Δt + , while reducing Δt -Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat.

[0068] If the curve of the crystal oscillator output phase difference changing with time is straight, then the parameter combination is determined as (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0069] If the curve of the crystal oscillator output phase difference over time still opens downward, continue to increase Δt + , reduce Δt - Or increase Δt + , while reducing Δt - If the cycle adjustment number threshold is not reached and the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the cycle adjustment number threshold is not reached and the curve of the crystal oscillator output phase difference over time opens upward, then reduce Δt + , increase Δt - Or reduce Δt + While increasing Δt - Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0070] If the crystal oscillator output phase difference curve over time is not straight when the cycle adjustment number threshold is reached, then maintain Δt + =Δt - Fixed by increasing Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; if the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination is determined to be (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time still opens downward, continue to increase Δ DAC+ , reduce ΔDAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method until the crystal oscillator output phase difference changes smoothly with time, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time opens upward, then by reducing Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Continue to adjust in this way until the phase difference of the crystal oscillator output changes smoothly with time, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

[0071] In one embodiment, the DAC value at any time t0+k*T satisfies the relationship:

[0072] DAC(t0+k*T)=DAC0+k*(N*Δ DAC+ -M*Δ DAC- )

[0073] Wherein, k is a positive integer.

[0074] In one embodiment, when Δt + =Δt - By setting T1, T2, Δ DAC+ and Δ DAC- Improve the autonomous timekeeping capability of the crystal oscillator.

[0075] Specifically, from the moment t0 when the crystal oscillator changes from the tamed state to the autonomous timekeeping state, if every Δt + DAC value increases step by step Δ DAC+ , the phase difference of the crystal oscillator output changes with time and satisfies the quadratic function relationship: + (t) = a + t 2 +b + t+c + ;

[0076] From the moment t0 when the crystal oscillator changes from the tamed state to the autonomous timekeeping state, if every Δt - DAC value decreases step by step Δ DAC- , the phase difference of the crystal oscillator output changes with time and satisfies the quadratic function relationship: - (t) = a - t 2 +b- t+c - ;

[0077] When Δt + =Δt - , Δ DAC+ =Δ DAC When a + ≈-a - , b + ≈-b - , c + ≈-c - That is, when the DAC value increases and decreases in a step-by-step manner at equal time and equal amplitude, the change pattern of the crystal oscillator output phase difference is opposite in polarity and approximately equal in amplitude, thus achieving automatic compensation of the positive and negative phase difference of the crystal oscillator output.

[0078] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. In addition, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0079] In a specific embodiment, let Δt + =Δt - =1,Δ DAC+ =Δ DAC- =1, 2, 3, in the state of crystal oscillator autonomous timing, the DAC value change and output phase difference measurement results are as follows Figure 4 As shown in the figure, it can be seen that the phase difference of the crystal oscillator output changes with time and satisfies the quadratic function. The larger the change of the DAC value, the smaller the opening and the steeper the change. DAC+ =Δ DAC- , the phase difference of the crystal oscillator output changes with time into a symmetrical relationship.

[0080] Let M=N=150, Δt + =Δt - =1,Δ DAC+ =Δ DAC- =1, use this parameter to periodically polarize the DAC value. When the crystal oscillator is in autonomous timing state, the measurement results of the output phase difference changing with time are as follows: Figure 5As shown in the figure, it can be seen that the output phase difference remains basically unchanged in a short period of time (600s) and is a horizontal straight line. This proves that the periodic polarization modulation DAC value can improve the autonomous timing capability of the crystal oscillator.

[0081] In order to further prove the effectiveness of this method, let M=N=150, Δt + =Δt - =1,Δ DAC+ =Δ DAC- =1, using this parameter to periodically polarize the DAC value, the crystal oscillator's autonomous timekeeping capability within a time scale of 35,000 seconds (9.7 hours) was tested, and the output phase difference measurement results are as follows: Figure 6 In the crystal oscillator's free-running mode, the timing accuracy (maximum value minus minimum value) is approximately 928ns. When periodic polarization is used to modulate the DAC value, the timing accuracy (maximum value minus minimum value) is approximately 150ns, a six-fold improvement.

[0082] In a specific embodiment, let M=N=10, Δt + =Δt - =1,Δ DAC+ =Δ DAC- =16, use this parameter to periodically polarize the DAC value, and when the crystal oscillator is in autonomous timing state, the measurement results of the output phase difference changing with time are as follows Figure 7 As shown in the figure, it can be seen that, in general, the output phase difference remains basically unchanged in a short period of time (500s), which proves that the periodic polarization modulation DAC value can improve the autonomous timekeeping ability of the crystal oscillator. However, compared with M=N=150, Δt + =Δt - =1,Δ DAC+ =Δ DAC- = 1, the phase difference fluctuation over time increases significantly, mainly due to Δ DAC Too large caused.

[0083] In one embodiment, a device for improving the autonomous timekeeping capability of a crystal oscillator is provided. The device uses a method of periodically polarizing a DAC value to improve the autonomous timekeeping capability of the crystal oscillator. The DAC value is a control signal at a voltage-controlled terminal of the crystal oscillator. The specific steps of the method of periodically polarizing the DAC value include: starting at time t0 when the crystal oscillator switches from a tamed state to an autonomous timekeeping state, within a time period T1, every first time interval Δt + , increase the DAC value step by step by Δ DAC+ ; During the T2 period starting from the time t0+T1, every second time interval Δt - , decrease the DAC value step by step by Δ DAC-; Similarly, the DAC value changes slowly with a period of T=T1+T2; the voltage-controlled voltage of the crystal oscillator is changed by using the periodically slowly changing DAC value, and the crystal oscillator frequency is fine-tuned to compensate for the phase deviation caused by the aging rate of the crystal oscillator itself and the frequency-temperature characteristics, thereby improving the autonomous timing accuracy of the crystal oscillator.

[0084] The specific definition of the device for improving the autonomous timekeeping capability of a crystal oscillator can be found in the definition of the method for improving the autonomous timekeeping capability of a crystal oscillator described above and will not be repeated here. The various modules in the aforementioned device for improving the autonomous timekeeping capability of a crystal oscillator can be implemented in whole or in part through software, hardware, or a combination thereof. The aforementioned modules can be embedded in or independent of a processor in a computer device in hardware form, or can be stored in a memory in a computer device in software form, so that the processor can call and execute the operations corresponding to the aforementioned modules.

[0085] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A method for improving the autonomous timekeeping capability of a crystal oscillator, characterized in that the method comprises: The method of periodic polarization modulation DAC value is used to improve the autonomous timekeeping capability of the crystal oscillator; The DAC value is a control signal of the crystal oscillator voltage control terminal, and the specific steps of the method for periodically polarizing the DAC value include: From the moment t0 when the crystal oscillator changes from the taming state to the autonomous timekeeping state, within the time period T1, every first time interval Δt + , increase the DAC value step by step by Δ DAC+ ; During the T2 period starting from the time t0+T1, every second time interval Δt - , decrease the DAC value step by step by Δ DAC- ; Similarly, the DAC value changes slowly with a period of T=T1+T2; The DAC value changes slowly and periodically to change the voltage control voltage of the crystal oscillator, fine-tuning the crystal oscillator frequency to compensate for the phase deviation caused by the aging rate of the crystal oscillator itself and the frequency-temperature characteristics, thereby improving the crystal oscillator's autonomous timing accuracy. Among them, T1 and Δt + , T2 and Δt - Satisfaction relationship: T1=N*Δt + , N positive integer T2=M*Δt - , M is a positive integer Where N is the time interval Δt within the T1 period + The number of M is the time interval Δt in the T2 period - The number of 2. The method for improving the autonomous timekeeping capability of a crystal oscillator according to claim 1, characterized in that the parameter combination (M, N; Δt + , Δt - ; Δ DAC+ , Δ DAC- ) includes the following steps: Step 1: Set the initial value of the parameter combination so that the parameter combination satisfies M=N, Δt + =Δt - , Δ DAC+ =Δ DAC- , get the initial curve of the change of the crystal oscillator output phase difference over time; Step 2: If the initial curve of the crystal oscillator output phase difference over time is flat, determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- )value; Step 3: If the initial curve of the crystal oscillator output phase difference over time is not straight, first keep M = N, Δ DAC+ =Δ DAC- Fixed, by adjusting Δt + and\or Δt - Adjust the output phase difference of the crystal oscillator to obtain the time-varying regularity curve; observe whether the output phase difference of the crystal oscillator is flat; if it is flat, determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ) value; if it is not straight, continue to + and\or Δt - Adjust. If the adjustment times are less than the preset maximum cycle threshold and the curve of the crystal oscillator output phase difference changing with time is flat, stop adjusting and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ) value; if the phase difference over time curve does not reach a flat line when the preset maximum cycle threshold is reached, then keep M = N, Δt + =Δt - Fixed, by DAC+ and\or Δ DAC- Adjust until the crystal oscillator output phase difference changes with time and the curve is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- )value.

3. The method for improving the autonomous timekeeping capability of a crystal oscillator according to claim 2, wherein when the initial curve of the variation law of the crystal oscillator output phase difference over time is open upward: step 3 specifically comprises: First, keep M=N, Δ DAC+ =Δ DAC- Fixed by reducing Δt + , increase Δt - Or reduce Δt + At the same time, add the Δt adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; If the curve of the crystal oscillator output phase difference changing with time is straight, then the parameter combination is determined as (M, N; Δt + , Δt - ; Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time still opens upward, continue to reduce Δt + , increase Δt - Or reduce Δt + At the same time, increase the Δt adjustment method to adjust until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time opens downward, then by increasing Δt + , reduce Δt - Or increase Δt + While reducing Δt - Continue to adjust in the same way; If the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference changing with time is not straight when the cycle adjustment number threshold is reached, then keep M=N, Δt + =Δt - Fixed by reducing Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; if the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination is determined to be (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time still opens upward, continue to reduce Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); if the curve opens downward, increase Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

4. The method for improving the autonomous timekeeping capability of a crystal oscillator according to claim 2, wherein when the initial curve of the variation law of the crystal oscillator output phase difference over time is open downward: step 3 specifically comprises: First, keep M=N, Δ DAC+ =Δ DAC- Fixed, by increasing Δt + , reduce Δt - Or increase Δt + , while reducing Δt - Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; If the curve of the crystal oscillator output phase difference changing with time is straight, then the parameter combination is determined as (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time still opens downward, continue to increase Δt + , reduce Δt - Or increase Δt + , while reducing Δt - If the cycle adjustment number threshold is not reached and the curve of the crystal oscillator output phase difference changing with time is flat, the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the cycle adjustment number threshold is not reached and the curve of the crystal oscillator output phase difference over time opens upward, then reduce Δt + , increase Δt - Or reduce Δt + While increasing Δt - Adjust the adjustment method until the curve of the crystal oscillator output phase difference changing with time is straight, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the crystal oscillator output phase difference curve over time is not straight when the cycle adjustment number threshold is reached, then maintain Δt + =Δt - Fixed by increasing Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method to obtain the curve of the crystal oscillator output phase difference changing with time, and observe whether the curve of the crystal oscillator output phase difference changing with time is flat; if the curve of the crystal oscillator output phase difference changing with time is flat, then the parameter combination is determined to be (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time still opens downward, continue to increase Δ DAC+ , reduce Δ DAC- Or increase Δ DAC+ While reducing Δ DAC- Adjust the adjustment method until the crystal oscillator output phase difference changes smoothly with time, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ); If the curve of the crystal oscillator output phase difference over time opens upward, then by reducing Δ DAC+ , increase Δ DAC- Or reduce Δ DAC+ While increasing Δ DAC- Continue to adjust in this way until the phase difference of the crystal oscillator output changes smoothly with time, and determine the parameter combination (M, N; Δt + , Δt - , Δ DAC+ , Δ DAC- ).

5. The method for improving the autonomous timekeeping capability of a crystal oscillator according to claim 1, wherein the DAC value at any time t0+k*T satisfies the relationship: DAC(t0+k*T)=DAC0+k*(N*Δ DAC+ -M*Δ DAC- ) in, k is a positive integer.

6. The method for improving the autonomous timekeeping capability of a crystal oscillator according to claim 1, wherein when Δt + =Δt - By setting T1, T2, Δ DAC+ and Δ DAC- Improve the autonomous timekeeping capability of the crystal oscillator.

7. A device for improving the autonomous timekeeping capability of a crystal oscillator, characterized in that the device improves the autonomous timekeeping capability of the crystal oscillator by periodically polarizing and modulating a DAC value; the DAC value is a control signal at a voltage-control terminal of the crystal oscillator, and the specific steps of the periodic polarization and DAC value modulation method include: From the moment t0 when the crystal oscillator changes from the taming state to the autonomous timekeeping state, within the time period T1, every first time interval Δt + , increase the DAC value step by step by Δ DAC+ ; During the T2 period starting from the time t0+T1, every second time interval Δt - , decrease the DAC value step by step by Δ DAC- ; Similarly, the DAC value changes slowly with a period of T=T1+T2; The DAC value changes slowly and periodically to change the voltage control voltage of the crystal oscillator, fine-tuning the crystal oscillator frequency to compensate for the phase deviation caused by the aging rate of the crystal oscillator itself and the frequency-temperature characteristics, thereby improving the crystal oscillator's autonomous timing accuracy. Among them, T1 and Δt + , T2 and Δt - Satisfaction relationship: T1=N*Δt + , N positive integer T2=M*Δt - , M is a positive integer Where N is the time interval Δt within the T1 period + The number of M is the time interval Δt in the T2 period - The number of

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