Voltage-controlled crystal oscillator time frequency synchronization method, device, medium and system based on data chain RTT

Abstract

The invention discloses a voltage-controlled crystal oscillator time-frequency synchronization method, device, medium and system based on data chain RTT, and belongs to the technical field of time-frequency synchronization of collaborative platforms, and the method comprises the following steps: S1, a sensor measures the RTT synchronization signal arrival time difference of a to-be-synchronized platform and a time reference; s2, calculating signal propagation time delay of inquiry and response between the platforms to obtain total motion time delay, resolving clock correction between the platforms by using an RTT algorithm, and compensating the clock correction through motion information and spatial position in a sensor to realize time synchronization; s3, inputting the compensated clock difference into a Kalman filter, and tracking the frequency offset between the platforms; and S4, after the frequency offset is obtained, adjusting the voltage-controlled crystal oscillator to realize frequency synchronization. The method solves the problem of clock error drift when the RTT algorithm is used for time synchronization, and has the advantages of low cost and high stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of time-frequency synchronization of cooperative platforms, and more particularly to a voltage-controlled crystal oscillator time-frequency synchronization method, device, medium and system based on data link RTT. BACKGROUND

[0002] The modern electromagnetic environment is complex and changeable, and the traditional time-frequency synchronization method mainly relies on satellite navigation systems such as GPS, Beidou, etc., but in the conflict situation, these satellite systems may be interfered or even destroyed. Therefore, it is crucial to develop a time-frequency synchronization technology that does not rely on satellite navigation systems. In the environment where satellite signals are limited, distributed devices must rely on more stable data links to achieve accurate time-frequency synchronization.

[0003] The RTT algorithm is one of the most commonly used algorithms in data link synchronization and has been applied in numerous engineering projects. However, in current engineering practice, the RTT algorithm is mainly used for time synchronization, but after each synchronization, there is still a continuous clock difference drift between distributed devices, which is caused by the frequency deviation of the frequency source used by the distributed devices. This technical problem needs to be solved in the field. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a voltage-controlled crystal oscillator time-frequency synchronization method, device, medium and system based on data link RTT, which solves the problem of clock difference drift in the use of RTT algorithm for time synchronization, and has the advantages of low cost and high stability.

[0005] The purpose of the present application is achieved by the following scheme: A voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT, comprising the following steps: S1, a sensor measures the RTT synchronization signal arrival time difference between the platform to be synchronized and the time reference; S2, the total motion time delay of the inquiry and response signals between the platforms is calculated, the clock difference between the platforms is solved using the RTT algorithm, and the clock difference is compensated through the motion information and spatial position in the sensor, to realize time synchronization; S3, the compensated clock difference is input into a Kalman filter to track the frequency deviation between the platforms; S4, after obtaining the frequency deviation, the voltage-controlled crystal oscillator is adjusted to realize frequency synchronization.

[0006] Further, in step S1, the sensor measures the RTT synchronization signal arrival time difference between the platform to be synchronized and the time reference, comprising the following sub-steps: According to the RTT synchronization algorithm, the arrival time of the inquiry signal of the platform to be synchronized is obtained and the arrival time of the response signal of the time reference The time difference of arrival is calculated according to the following formula : ; Wherein, is the time slot of the inquiry and response interval.

[0007] Further, in step S2, the signal propagation time delay of the inquiry and response between the platforms is calculated, including the sub-steps: S21, according to the platform position and speed obtained by the sensor in the RTT time synchronization process, the signal propagation time delay of the inquiry and response between the platforms is calculated according to the following formula: ; ; Wherein, is the speed of light, is the time delay of signal transmission during inquiry, is the time delay of signal transmission during response, , ) and , ) are the differences between the spatial coordinates between the platforms at the start of inquiry and response respectively, , ) is the time reference coordinate minus the coordinate of the to-be-synchronized side, , ) is the coordinate of the to-be-synchronized side minus the time reference coordinate, , ) is the motion speed of the time reference at the start of inquiry, , ) is the motion speed of the to-be-synchronized side at the start of response; S22, according to step S21, the total motion time delay is calculated according to the following formula : .

[0008] Further, in step S2, the clock difference between the platforms is calculated using the RTT algorithm, including the sub-steps: In the RTT time synchronization containing errors, platform A is the time reference, and platform B is the to-be-synchronized side; the to-be-synchronized side first sends an inquiry signal, and the time reference sends a response signal after an interval of one time slot, and the clock difference is inferred according to the time of receiving the signals by the two platforms.

[0009] Further, in step S2, the clock difference is compensated by the motion information and spatial position in the sensor, including the sub-steps: The compensated clock difference is calculated according to the following formula: ; wherein, is the real clock difference between the two platforms, and is the transmission time delay caused by the transmitter and related circuits, and is the receiving time delay caused by the receiver and related circuits; is the time delay of signal transmission in the inquiry process, is the time delay of signal transmission in the response process.

[0010] Further, in step S3, the model parameters of the Kalman filter are as follows: Table 1

[0011] wherein the state matrix is is the clock difference measurement value, is the frequency difference, is the frequency of the time reference, is the frequency offset, is the frequency difference drift rate, the state transition matrix is is the period of clock difference synchronization, the observation noise covariance matrix is is the standard deviation of measurement error.

[0012] Further, in step S4, the frequency offset is obtained to adjust the voltage-controlled crystal oscillator to realize frequency synchronization, specifically including the following sub-steps: The voltage-controlled crystal oscillator is controlled according to the output value of the Kalman filter to reduce the frequency difference between devices, and finally realize frequency synchronization: ; ; wherein, determines the step length of each update, is the period of clock difference update, is the frequency offset, is the frequency offset of the last round of synchronization, is the feedback frequency control amount, is the frequency control amount of the last round of synchronization, is the frequency offset when the algorithm is started.

[0013] A computer device, comprising a processor and a memory, wherein the memory stores a computer program, and when the computer program is loaded by the processor, the method according to any one of the above is executed.

[0014] A computer readable storage medium, wherein the computer readable storage medium stores a computer program, and when the computer program is loaded by a processor, the method according to any one of the above is executed.

[0015] An electronic system comprising the computer device as described above.

[0016] The beneficial effects of the present application include: The present application uses voltage-controlled crystal oscillator as clock source, realizes a low-cost time-frequency synchronization scheme, obtains the spatial position and speed information of each platform through sensor, thereby compensating the motion delay to realize time synchronization. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0018] Figure 1 The flow chart of the voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT in the embodiment of the present application; Figure 2 The RTT time synchronization principle diagram in the embodiment of the present application; Figure 3 The clock difference diagram of the simulation time reference and the clock difference of the to-be-synchronized party in the embodiment of the present application; Figure 4 The frequency difference diagram of the simulation time reference and the to-be-synchronized party in the embodiment of the present application; Figure 5 The clock difference diagram of the simulation time reference and the to-be-synchronized party after completing the RTT synchronization in the embodiment of the present application; Figure 6 The clock difference value diagram of the clock difference drift for 12s in the embodiment of the present application. DETAILED DESCRIPTION

[0019] All features disclosed in the embodiments of the present specification, or all steps in the methods or processes impliedly disclosed, can be combined and / or extended, replaced, unless mutually exclusive.

[0020] In view of the status in the background, the inventors of the present application believe that: in order to effectively suppress clock difference drift and realize long-term stable time synchronization, frequency synchronization must be realized between distributed devices. Voltage-controlled crystal oscillator becomes a frequency source commonly used in distributed devices due to its cost-effectiveness. Its frequency can be adjusted within a certain range, which provides the possibility for realizing frequency synchronization. Therefore, studying the method of adjusting voltage-controlled crystal oscillator has important significance and application value for suppressing clock difference drift and realizing stable time-frequency synchronization.

[0021] In the present concept, it is intended to provide a data link RTT based voltage controlled crystal oscillator time and frequency synchronization scheme under satellite denial condition, measure the clock difference between platforms and track the frequency difference between platforms, adjust the voltage controlled crystal oscillator to ultimately realize the time and frequency synchronization of distributed devices under satellite denial condition, and the specific implementation process is as follows: In the preferred embodiment, as the first aspect of the present application, a data link RTT based voltage controlled crystal oscillator time and frequency synchronization method is specifically provided, as shown in Figure 1 , comprising the following steps: P1: The sensor measures the RTT synchronization signal arrival time difference of the platform to be synchronized and the time reference. According to the RTT synchronization algorithm, the arrival time of the inquiry signal of the platform to be synchronized and the arrival time of the response signal of the time reference , the calculation formula is as follows:

[0022] Among them: is the time slot of the inquiry and response interval.

[0023] P2: According to the platform position and speed obtained by the sensor in the RTT time synchronization process, the signal propagation time delay of the inquiry and response between platforms is calculated, and the calculation formula is as follows:

[0024]

[0025] Among them: is the speed of light; is the time delay of signal transmission in the inquiry process, is the time delay of signal transmission in the response process; , ) and , ) are the differences in spatial coordinates between platforms at the start time of inquiry and response, , ) is the time reference coordinate minus the coordinate of the platform to be synchronized, , ) is the coordinate of the platform to be synchronized minus the coordinate of the time reference; , ) is the motion speed of the time reference at the start time of inquiry, , ) is the motion speed of the platform to be synchronized at the start time of response.

[0026] P3: The time delay caused by motion in the inquiry and response processes is calculated respectively to obtain the total motion time delay , the calculation formula is as follows:

[0027] P4: As shown in the RTT time synchronization containing errors, A platform is the time reference, B platform is the synchronization side. The synchronization side first sends a query signal, and the time reference sends a response signal after an interval of one time slot. The clock difference is speculated according to the time of receiving signals of the two platforms, and the time synchronization is realized. Figure 2

[0028] Figure 2 In the formula, Δt is the real clock difference between the two platforms; and Tt is the transmission time delay caused by the transmitter and related circuit, and Tr is the receiving time delay caused by the receiver and related circuit; is the signal transmission time delay in the query process, and Td is the signal transmission time delay in the response process. The calculation formula of the compensated clock difference is as follows:

[0029]

[0030] P5: The compensated clock difference is input into the Kalman filter to realize the tracking of the frequency deviation. The model parameters of the Kalman filter are as follows: Table 1

[0031] In the formula, the state matrix is is the clock difference measurement value, is the frequency difference, is the frequency of the time reference. is the frequency deviation, is the frequency difference drift rate; the state transition matrix is is the period of clock difference synchronization; the observation noise covariance matrix is is the standard deviation of measurement error.

[0032] P6: The output value of the Kalman filter is used to control the voltage-controlled crystal oscillator to reduce the frequency difference between devices, and finally realize the frequency synchronization.

[0033]

[0034]

[0035] In the formula, the step length of each update is determined by ; the period of clock difference update is ; the frequency deviation is ; the frequency deviation of the last round of synchronization is ; and the feedback frequency control amount is ;​​​​ is the frequency control amount of the last round of synchronization; is the frequency offset at the start of the algorithm.

[0036] Simulation scenario: the time reference and the frequency drift curve of the to-be-synchronized party are respectively:

[0037]

[0038] wherein: is the nominal frequency of the crystal oscillator 100MHz, is the initial frequency difference 0.2Hz, is the drift time. The Kalman filter is used to track the frequency offset between the platforms, and every 12s the control amount is compensated to , the oscillation frequency of the to-be-synchronized party is adjusted to realize frequency synchronization with the time reference.

[0039] Simulation analysis: Figure 3 is the clock difference between the two platforms after time synchronization, and after 1200s of synchronization, the clock difference between the two platforms is controlled within 2ns. Figure 4 is the frequency difference curve of the two platforms before and after adding feedback control, and after 1200s of synchronization, the frequency difference between the two platforms is controlled within 0.07Hz.

[0040] Experimental scenario: the aircraft platform motion parameters are input into the simulation and evaluation computer, and the radio frequency of the time reference and the to-be-synchronized party is transmitted, and the hardware transceiver delay and Doppler effect in the channel transmission process are simulated by the channel simulator. Gap counter is used for counting, and the clock difference between the time reference and the to-be-synchronized party is updated every 1s, and the time-frequency synchronization between the time reference and the to-be-synchronized party is performed every 12s.

[0041] Experimental analysis: Figure 5 is the clock difference between the two platforms after RTT time synchronization based on data link. After nine rounds of synchronization, the clock difference is finally stabilized at 16~20ns, realizing high-precision time synchronization.

[0042] Figure 6 is the clock difference drift after 12s of each round of synchronization. After nine rounds of synchronization, the maximum clock difference drift is shortened from 432ns to 76ns. It is proved that the voltage-controlled crystal oscillator is effectively controlled, and the frequency difference between the devices is suppressed.

[0043] Table 2 shows the clock difference after each round of synchronization and the clock difference after 12s of drift, and the frequency difference accuracy of each round of synchronization is calculated according to the data in Table 1. After nine rounds of synchronization, the frequency difference accuracy converges to 4.6667e-9, i.e. the clock difference drift caused by the frequency offset is 4.6667ns / s, which completes the index of less than 5ns / s, and realizes frequency synchronization.

[0044] Table 2

[0045] As a second aspect of the present application, an embodiment of the present application specifically provides a computer device, comprising a processor and a memory, wherein the memory stores a computer program, and the computer program is loaded by the processor to execute the method as described above.

[0046] As a third aspect of the present application, an embodiment of the present application specifically provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is loaded by a processor to execute the method as described above.

[0047] As a fourth aspect of the present application, an embodiment of the present application specifically provides an electronic system, comprising the computer device as described above.

[0048] The units described in the embodiments of the present application can be implemented by software, or by hardware, or by a combination of software and hardware. The units described can be located in one place or distributed over several places. The names of the units in some cases do not limit the units themselves.

[0049] According to an aspect of the embodiments of the present application, a computer program product or a computer program is provided, which comprises computer instructions stored in a computer readable storage medium. A processor of a computer device reads the computer instructions from the computer readable storage medium, and the processor executes the computer instructions, so that the computer device executes the method provided in the various optional implementation manners described above.

[0050] As another aspect, an embodiment of the present application further provides a computer readable medium, which can be included in the electronic device described in the above embodiments, or can exist separately and not be assembled into the electronic device. The computer readable medium carries one or more programs, and when the one or more programs are executed by the electronic device, the electronic device implements the method described in the above embodiments.

Claims

1. A time-frequency synchronization method for a voltage-controlled crystal oscillator based on data link RTT, characterized in that, Includes the following steps: S1, the sensor measures the arrival time difference of the RTT synchronization signal between the platform to be synchronized and the time reference; S2, calculate the signal propagation delay between the query and response between the platforms to obtain the total motion delay, use the RTT algorithm to solve the clock difference between the platforms, and compensate for the clock difference by using motion information and spatial position in the sensors to achieve time synchronization; S3 inputs the compensated clock error into the Kalman filter to track the inter-platform frequency offset; S4, after obtaining the frequency offset, adjust the voltage-controlled crystal oscillator to achieve frequency synchronization.

2. The voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT according to claim 1, characterized in that, In step S1, the sensor measures the arrival time difference of the RTT synchronization signals between the platform to be synchronized and the time reference, including the following sub-steps: According to the RTT synchronization algorithm, obtain the arrival time of the query signal from the party to be synchronized. Arrival time of the response signal with time reference Calculate the arrival time difference using the following formula. : ； in, This refers to the time slot between queries and responses.

3. The voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT according to claim 1, characterized in that, In step S2, the signal propagation delay between the inter-platform query and response is used to obtain the total motion delay, including the following sub-steps: S21, Based on the platform position and velocity acquired by the sensors during RTT time synchronization, calculate the signal propagation delay for inter-platform queries and responses using the following formula: ； ； in, At the speed of light, The delay in signal transmission during the inquiry process, The delay in signal transmission during the response process, , )and , These represent the difference in spatial coordinates between the platforms at the start times of the query and the response. , The time reference coordinates are subtracted from the coordinates of the direction to be synchronized. , The coordinates to be synchronized are the coordinates of the target direction minus the time reference coordinates. , To query the velocity of the motion based on the starting time reference, , The response is the velocity of the object to be synchronized at the start of the response. S22, Based on step S21, calculate the total motion delay using the following formula. : 。 4. The voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT according to claim 1, characterized in that, In step S2, the calculation of clock difference between platforms using the RTT algorithm includes the following sub-steps: In RTT time synchronization with errors, platform A is the time reference and platform B is the one to be synchronized. The one to be synchronized first sends an inquiry signal, and after a time slot, the time reference sends a response signal. The clock difference is inferred based on the time of the signals received by the two platforms.

5. The voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT according to claim 1, characterized in that, In step S2, the compensation for clock error using motion information and spatial position from the sensor includes the following sub-steps: Calculate the compensated clock error using the following formula: ； in, It is the actual clock difference between the two platforms. and The transmission delay is caused by the transmitter and related circuitry. and The reception delay is caused by the receiver and related circuitry. The delay in signal transmission during the inquiry process, This refers to the delay in signal transmission during the response process.

6. The voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT according to claim 1, characterized in that, In step S3, the model parameters of the Kalman filter are as follows: Table 1 Among them, the state matrix This is a clock error measurement value. For frequency difference, The frequency of the time base It's frequency offset. For frequency drift rate, the state transition matrix is... For the clock synchronization period, the observation noise covariance matrix is... This represents the standard deviation of the measurement error.

7. The voltage-controlled crystal oscillator time-frequency synchronization method based on data link RTT according to claim 1, characterized in that, In step S4, adjusting the voltage-controlled crystal oscillator after obtaining the frequency offset to achieve frequency synchronization specifically includes the following sub-steps: By controlling the voltage-controlled crystal oscillator based on the output value of the Kalman filter, the frequency difference between devices is reduced, ultimately achieving frequency synchronization. ； ； in, This determines the step size for each update. For the period of clock cycle update, For frequency offset, For the frequency offset of the previous synchronization, For feedback frequency control, This is the frequency control value for the previous synchronization round. This is the frequency offset when the algorithm starts.

8. A computer device, characterized in that, It includes a processor and a memory, wherein the memory stores a computer program that, when loaded by the processor, executes the method as described in any one of claims 1 to 7.

9. A computer-readable storage medium, characterized in that, A computer program is stored in a readable storage medium, which, when loaded by a processor, executes the method as described in any one of claims 1 to 7.

10. An electronic system, characterized in that, Includes the computer device as described in claim 8.

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