CN111399366B - Multi-clock comprehensive time keeping method and multi-rubidium clock time keeping device - Google Patents
Multi-clock comprehensive time keeping method and multi-rubidium clock time keeping device Download PDFInfo
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- CN111399366B CN111399366B CN202010234263.4A CN202010234263A CN111399366B CN 111399366 B CN111399366 B CN 111399366B CN 202010234263 A CN202010234263 A CN 202010234263A CN 111399366 B CN111399366 B CN 111399366B
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- G04—HOROLOGY
- G04F—TIME-INTERVAL MEASURING
- G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
- G04F5/14—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks
Abstract
The invention discloses a multi-clock comprehensive time keeping method and a multi-rubidium clock time keeping device, and relates to the technical field of multi-rubidium clock time keeping. According to the invention, a plurality of rubidium clocks are arranged, the rubidium clocks are integrated to obtain the integrated clock, the crystal oscillator is kept consistent with the integrated clock in the time keeping state, and the time keeping high index performance and better consistency can be ensured. The invention adopts the comprehensive time keeping technology adaptive to rubidium clock characteristics, can effectively utilize more rubidium clock resources of the system and ensure the time keeping performance.
Description
Technical Field
The invention relates to the technical field of multi-rubidium clock time keeping, in particular to a multi-rubidium clock comprehensive time keeping method and a multi-rubidium clock time keeping device, which are suitable for various time service and time keeping terminals internally containing rubidium clocks.
Background
At present, rubidium clocks are widely applied to various fixed ground, vehicle-mounted and ship-based time service and time keeping terminals due to the characteristics of small size, low power consumption, low price, high frequency accuracy and stability, long service life, strong temperature adaptability and the like.
The rubidium clock timekeeping mainly adopts a mode of clock disciplining by externally inputting a reference signal to calibrate the frequency accuracy of the rubidium clock, and continuously outputs an accurate and stable time frequency signal according to high-precision timekeeping after a rubidium clock is subjected to reference source failure or shutdown.
Under the requirement of high-reliability application, a plurality of rubidium clocks are generally equipped for keeping time. In the traditional time-frequency generation principle, one rubidium clock is selected as a main clock source according to system rules to generate a system clock, and the system main clock is switched to a standby rubidium clock when the main clock fails. However, this solution has the following drawbacks:
1) the time keeping index is determined by the primary rubidium clock, and the randomness of the time keeping index is high;
2) only one rubidium clock of the system participates in local time generation, and other rubidium clocks are idle, so that resources are not utilized to the maximum extent;
3) the switching of the main clock and the standby clock can generate phase jump;
4) the long switching time of the main clock and the standby clock can cause the interruption of system service.
Disclosure of Invention
In view of the above, the present invention provides a multi-clock comprehensive timekeeping method and a multi-rubidium clock timekeeping device, which can effectively utilize multi-rubidium clock resources of a system, ensure timekeeping performance, and improve reliability.
In order to achieve the purpose, the invention adopts the technical scheme that:
a multi-clock comprehensive time keeping method is used for keeping the time keeping accuracy of a crystal oscillator according to the time of N rubidium clocks in a time keeping state, wherein N is larger than or equal to 2, and the method comprises the following steps:
(1) measuring time differences between each rubidium clock and a crystal oscillator;
(2) taking one rubidium clock as a reference clock, and calculating the time difference of other rubidium clocks to the reference clock to obtain the time difference between N-1 rubidium clocks and the reference clock;
(3) calculating the variation of each time difference in the step (2) in the observation period;
(4) carrying out weighted average on the variation obtained in the step (3) to obtain the variation of the time difference of an integrated clock and a reference clock in an observation period, wherein the integrated clock is a virtual clock determined by N-1 rubidium clocks;
(5) taking the time difference between the crystal oscillator and the reference clock as the time difference between the comprehensive clock and the reference clock at the initial time of the observation period, and obtaining the time difference between the comprehensive clock and the reference clock at the end time of the observation period according to the variation obtained in the step (4);
(6) adjusting the crystal oscillator according to the reference clock and the time difference at the end of the observation period obtained in the step (5) to keep the crystal oscillator consistent with the comprehensive clock;
the weighted average mode in the step (4) is as follows:
(401) calculating the error of N-1 rubidium clocks except for the reference clock relative to the crystal oscillator output time;
(402) calculating the Allan variance of the errors obtained in the step (401), calculating the stability of N-1 rubidium clocks, and taking the normalized stability value as the weight of each corresponding rubidium clock;
(403) and (4) carrying out weighted average according to the weight values obtained in the step (402).
In addition, the invention also provides a highly reliable rubidium clock timekeeping device, which comprises a time-frequency comprehensive module, a power supply module and a plurality of rubidium clock modules, wherein the time-frequency comprehensive module comprises an external reference decoding module, a constant-temperature crystal oscillator, a digital-to-analog converter, a first time difference measuring chip and a first single chip microcomputer, each rubidium clock module comprises a respective rubidium clock, a second time difference measuring chip and a second single chip microcomputer, and each rubidium clock module is connected with the time-frequency comprehensive module through a CAN bus;
the external reference decoding module is used for receiving an external reference signal input from the outside and transmitting the external reference signal to the first time difference measuring chip; the first single chip microcomputer is communicated with the second single chip microcomputer of each rubidium clock module through a CAN bus; a second time difference measuring chip of each rubidium clock module is communicated with the constant-temperature crystal oscillator through a CAN bus;
when the device is in a state of tracking and locking the external reference signal, each rubidium clock module uses a built-in second time difference measuring chip to measure the time difference between the 1PPS signal output by each rubidium clock and the 1PPS signal output by the constant-temperature crystal oscillator, and the frequency of each rubidium clock is adjusted after filtering according to the time difference, so that the tracking and locking of each rubidium clock to the constant-temperature crystal oscillator are realized, and the tracking and locking of the rubidium clock to the external reference signal are indirectly realized;
after locking, when the external reference signal disappears or the device is manually set to work in a timekeeping state, each rubidium clock module measures the time difference between the 1PPS signal output by each rubidium clock and the 1PPS signal output by the constant-temperature crystal oscillator by using a built-in second time difference measuring chip, and sends the respective time difference information to a first single chip of a time-frequency comprehensive module through a CAN bus; the first single chip microcomputer adjusts the frequency of the constant-temperature crystal oscillator according to the time difference information through the multi-clock comprehensive time keeping method, so that the constant-temperature crystal oscillator tracks the comprehensive time of the multi-rubidium clock.
The invention adopts the technical scheme and has the following beneficial effects:
1. the rubidium clock can be comprehensively timed, and the equipment time can be seamlessly switched to any specified clock.
2. By adopting multi-rubidium clock comprehensive timekeeping, the timekeeping reliability of the equipment can be improved.
3. The addition, subtraction and replacement of a rubidium clock can be realized without depending on a specific rubidium clock.
Drawings
Fig. 1 is a schematic diagram of a rubidium clock timing device according to an embodiment of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
A multi-clock comprehensive time keeping method is used for keeping the time keeping accuracy of a crystal oscillator according to the time of N rubidium clocks in a time keeping state, wherein N is larger than or equal to 2, and the method comprises the following steps:
(1) measuring time differences between each rubidium clock and a crystal oscillator;
(2) taking one rubidium clock as a reference clock, and calculating the time difference of other rubidium clocks to the reference clock to obtain the time difference between N-1 rubidium clocks and the reference clock;
(3) calculating the variation of each time difference in the step (2) in the observation period;
(4) carrying out weighted average on the variation obtained in the step (3) to obtain the variation of the time difference of an integrated clock and a reference clock in an observation period, wherein the integrated clock is a virtual clock determined by N-1 rubidium clocks;
(5) taking the time difference between the crystal oscillator and the reference clock as the time difference between the comprehensive clock and the reference clock at the initial time of the observation period, and obtaining the time difference between the comprehensive clock and the reference clock at the end time of the observation period according to the variation obtained in the step (4);
(6) adjusting the crystal oscillator according to the reference clock and the time difference at the end of the observation period obtained in the step (5) to keep the crystal oscillator consistent with the comprehensive clock;
the weighted average mode in the step (4) is as follows:
(401) calculating the error of N-1 rubidium clocks except for the reference clock relative to the crystal oscillator output time;
(402) calculating the Allan variance of the errors obtained in the step (401), calculating the stability of N-1 rubidium clocks, and taking the normalized stability value as the weight of each corresponding rubidium clock;
(403) and (4) carrying out weighted average according to the weight values obtained in the step (402).
In addition, the invention also provides a highly reliable rubidium clock timekeeping device, which comprises a time-frequency comprehensive module, a power supply module and a plurality of rubidium clock modules, wherein the time-frequency comprehensive module comprises an external reference decoding module, a constant-temperature crystal oscillator, a digital-to-analog converter, a first time difference measuring chip and a first single chip microcomputer, each rubidium clock module comprises a respective rubidium clock, a second time difference measuring chip and a second single chip microcomputer, and each rubidium clock module is connected with the time-frequency comprehensive module through a CAN bus;
the external reference decoding module is used for receiving an external reference signal input from the outside and transmitting the external reference signal to the first time difference measuring chip; the first single chip microcomputer is communicated with the second single chip microcomputer of each rubidium clock module through a CAN bus; a second time difference measuring chip of each rubidium clock module is communicated with the constant-temperature crystal oscillator through a CAN bus;
when the device is in a state of tracking and locking the external reference signal, each rubidium clock module uses a built-in second time difference measuring chip to measure the time difference between the 1PPS signal output by each rubidium clock and the 1PPS signal output by the constant-temperature crystal oscillator, and the frequency of each rubidium clock is adjusted after filtering according to the time difference, so that the tracking and locking of each rubidium clock to the constant-temperature crystal oscillator are realized, and the tracking and locking of the rubidium clock to the external reference signal are indirectly realized;
after locking, when the external reference signal disappears or the device is manually set to work in a timekeeping state, each rubidium clock module measures the time difference between the 1PPS signal output by each rubidium clock and the 1PPS signal output by the constant-temperature crystal oscillator by using a built-in second time difference measuring chip, and sends the respective time difference information to a first single chip of a time-frequency comprehensive module through a CAN bus; the first single chip microcomputer adjusts the frequency of the constant-temperature crystal oscillator according to the time difference information through the multi-clock comprehensive time keeping method, so that the constant-temperature crystal oscillator tracks the comprehensive time of the multi-rubidium clock.
The device CAN adopt a modular design, 1 rubidium clock or more is equipped according to actual requirements, a rubidium clock module and a time-frequency comprehensive module are connected through a CAN bus interface, and free expansion CAN be supported.
Taking a dual rubidium clock as an example, as shown in fig. 1, a highly reliable multi-rubidium clock time keeping device mainly comprises a time-frequency integration module, a rubidium clock module 1, a rubidium clock module 2, and a power supply module. The time-frequency synthesis module mainly comprises an external reference decoding module 1, a constant-temperature crystal oscillator 2, a time difference measuring chip 3, a DAC 4 and a single chip microcomputer 5. The rubidium clock module 1 mainly comprises a time difference measuring chip 7, a rubidium clock 8 and a single chip microcomputer 9. The rubidium clock module 2 mainly comprises a time difference measuring chip 10, a rubidium clock 11 and a single chip microcomputer 12.
When the device is in a state of tracking and locking the external reference source, the working modes of the modules are as follows:
1) the time-frequency synthesis module analyzes the time of the external reference signal through the external reference decoding module 1;
2) the time-frequency synthesis module singlechip 5 controls the time difference measurement chip 3 to measure the time difference between the 1PPS signal analyzed by the decoding module 1 and the 1PPS signal generated by the constant-temperature crystal oscillator frequency division;
3) after the time difference is filtered by the singlechip 5 arranged in the time-frequency comprehensive module, the constant-temperature crystal oscillator is acclimated by adjusting a DAC 4 chip, so that the PPS signal of the time-frequency comprehensive module 1 realizes the tracking locking of an external reference signal;
4) the rubidium clock module 1 measures the time difference between a rubidium clock 8 outputting a 1PPS signal and a constant temperature crystal oscillator 3 outputting the 1PPS signal by using a built-in time difference measuring chip 7, and adjusts the frequency of the rubidium clock after filtering according to the time difference so as to realize the tracking locking of the rubidium clock to the constant temperature crystal oscillator and indirectly realize the tracking locking of the rubidium clock to an external reference. The rubidium clock module 2 has the same working principle as the rubidium clock module 1.
When the equipment is locked, the reference source fails or the equipment is manually set to work in a time keeping state, and the rubidium clock has high frequency accuracy, stability, low frequency drift rate and temperature coefficient and is converted into a time keeping device of the equipment. And the time-frequency comprehensive module takes the rubidium clock as a reference source of a built-in constant-temperature crystal oscillator for tracking and taming. The working principle of the equipment in the time keeping state is as follows:
1) the rubidium clock module 1 measures the time difference between a rubidium clock 8 output 1PPS signal and a time frequency comprehensive module output 1PPS signal by using a built-in time difference measuring chip 7, and sends clock difference information to a built-in single chip microcomputer 5 of the time frequency comprehensive module through a CAN bus;
2) the rubidium clock module 2 and the rubidium clock module 1 are in the same working state, and clock difference information is sent to a single chip microcomputer 5 arranged in the time-frequency comprehensive module through a CAN bus;
3) after receiving the clock difference information sent by the rubidium clock module 1 and the rubidium clock module 2, the time-frequency comprehensive module calculates the comprehensive clock time difference through a multi-clock comprehensive time keeping algorithm according to the clock difference information, and adjusts the frequency of the constant-temperature crystal oscillator according to the comprehensive clock time difference so as to realize the tracking of the constant-temperature crystal oscillator on the comprehensive time of the rubidium clock and output signals.
The device adopts a multi-clock comprehensive time keeping method, in the process of multi-clock time keeping of the equipment, in order to avoid mutual influence among rubidium clocks, each rubidium clock is independently kept as an independent time keeping unit, and if N rubidium clocks are arranged in the system, the system can be equivalent to a time-frequency comprehensive module and has N independent reference sources. The method dynamically adjusts each rubidium clock weight, has real-time performance, and can effectively filter short-term change and noise of frequency, and comprises the following specific steps:
(1) rubidium clock module i measures time difference t between time frequency comprehensive module and rubidium clock through time difference measuring chip built in rubidium clock modulei(t + tau), and sending the time difference to a time-frequency synthesis module through a CAN bus;
(2)the rubidium clock 1 is used as a comprehensive atomic time calculation reference clock, the time-frequency comprehensive module calculates clock difference of each rubidium clock module to the rubidium clock 1, and time difference between each rubidium clock and the rubidium clock 1 is xri(t+τ)＝ti(t+τ)-t1(t+τ)。
(3) The amount of change in the time difference of each rubidium clock with respect to the reference clock (i.e., rubidium clock 1) within the observation period τ is calculated as: x'ri(t+τ)＝xri(t+τ)-xri(t)；
(4) The time difference variation of the integrated clock and the reference clock can be obtained by weighted average:
x′r1(t+τ)＝∑(wi*x′ri(t+τ))，
wherein, i is 2, 3 … … N-1, and N is the number of rubidium clocks in the clock group;
(5) calculating the time difference between the integrated clock and the reference clock:
xr1(t+τ)＝xr1(t)+x′r1(t+τ)；
(6) the frequency of the constant-temperature crystal oscillator is adjusted by the time-frequency synthesis module, so that the time difference between the constant-temperature crystal oscillator and the reference clock is xr1(t + τ) to achieve an integrated time output.
The weight of the rubidium clock module can be determined by the following method:
(1) calculating the Allen variance of each rubidium clock relative to the error of the integrated clock to obtain the stability p of each rubidium clocki；
(2) Normalizing the stability of the rubidium clock to obtain the weight w of each rubidium clocki：
In summary, the present invention is configured to provide a plurality of rubidium clocks, integrate the plurality of rubidium clocks to obtain a comprehensive clock, and maintain the crystal oscillator in conformity with the comprehensive clock in the timekeeping state, thereby ensuring high index performance and better consistency in timekeeping. The invention adopts the comprehensive time keeping technology adaptive to rubidium clock characteristics, can effectively utilize more rubidium clock resources of the system and ensure the time keeping performance.
Claims (2)
1. A multi-clock comprehensive time keeping method is characterized by being used for keeping the time keeping accuracy of a crystal oscillator according to the time of N rubidium clocks in a time keeping state, wherein N is larger than or equal to 2, and the method comprises the following steps:
(1) measuring time differences between each rubidium clock and a crystal oscillator;
(2) taking one rubidium clock as a reference clock, and calculating the time difference of other rubidium clocks to the reference clock to obtain the time difference between N-1 rubidium clocks and the reference clock;
(3) calculating the variation of each time difference in the step (2) in the observation period;
(4) carrying out weighted average on the variation obtained in the step (3) to obtain the variation of the time difference of an integrated clock and a reference clock in an observation period, wherein the integrated clock is a virtual clock determined by N-1 rubidium clocks;
(5) taking the time difference between the crystal oscillator and the reference clock as the time difference between the comprehensive clock and the reference clock at the initial time of the observation period, and obtaining the time difference between the comprehensive clock and the reference clock at the end time of the observation period according to the variation obtained in the step (4);
(6) adjusting the crystal oscillator according to the reference clock and the time difference at the end of the observation period obtained in the step (5) to keep the crystal oscillator consistent with the comprehensive clock;
the weighted average mode in the step (4) is as follows:
(401) calculating the error of N-1 rubidium clocks except for the reference clock relative to the crystal oscillator output time;
(402) calculating the Allan variance of the errors obtained in the step (401), calculating the stability of N-1 rubidium clocks, and taking the normalized stability value as the weight of each corresponding rubidium clock;
(403) and (4) carrying out weighted average according to the weight values obtained in the step (402).
2. The highly-reliable multi-rubidium clock time keeping device is characterized by comprising a time-frequency comprehensive module, a power supply module and a plurality of rubidium clock modules, wherein the time-frequency comprehensive module comprises an external reference decoding module, a constant-temperature crystal oscillator, a digital-to-analog converter, a first time difference measuring chip and a first single chip microcomputer, each rubidium clock module comprises a rubidium clock, a second time difference measuring chip and a second single chip microcomputer, and each rubidium clock module is connected with the time-frequency comprehensive module through a CAN bus;
the external reference decoding module is used for receiving an external reference signal input from the outside and transmitting the external reference signal to the first time difference measuring chip; the first single chip microcomputer is communicated with the second single chip microcomputer of each rubidium clock module through a CAN bus; a second time difference measuring chip of each rubidium clock module is communicated with the constant-temperature crystal oscillator through a CAN bus;
when the device is in a state of tracking and locking the external reference signal, each rubidium clock module uses a built-in second time difference measuring chip to measure the time difference between the 1PPS signal output by each rubidium clock and the 1PPS signal output by the constant-temperature crystal oscillator, and the frequency of each rubidium clock is adjusted after filtering according to the time difference, so that the tracking and locking of each rubidium clock to the constant-temperature crystal oscillator are realized, and the tracking and locking of the rubidium clock to the external reference signal are indirectly realized;
after locking, when the external reference signal disappears or the device is manually set to work in a timekeeping state, each rubidium clock module measures the time difference between the 1PPS signal output by each rubidium clock and the 1PPS signal output by the constant-temperature crystal oscillator by using a built-in second time difference measuring chip, and sends the respective time difference information to a first single chip of a time-frequency comprehensive module through a CAN bus; the first single chip microcomputer adjusts the frequency of the constant-temperature crystal oscillator according to the time difference information through the multi-clock comprehensive time keeping method as claimed in claim 1, so that the constant-temperature crystal oscillator tracks the comprehensive time of the multi-rubidium clock.
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