阅读说明：本技术 一种适应不同类型频率源远程比对的共视时间规划方法 (Common-view time planning method suitable for remote comparison of different types of frequency sources ) 是由 刘娅 李孝辉 陈瑞琼 樊多盛 于 2020-05-06 设计创作，主要内容包括：本发明提供了一种适应不同类型频率源远程比对的共视时间规划方法,依次确定共视起始时间,根据对频率源的先验知识选择适合被测频率源输出信号的时间变化模型,初次确定频率源模型的参数,计算待测频率源的输出随时间变化量,确定最优跟踪周期值,计算任意跟踪周期的开始时间。本发明可以根据不同频率源的性能特征,设计与其相匹配的跟踪周期,以适应远距离、高精度测量频率源的时间变化需求,为使各站的频率源之间保持同步提供支撑,降低卫星共视技术的使用条件,提高可用性。(The invention provides a common-view time planning method suitable for remote comparison of different types of frequency sources, which sequentially determines common-view starting time, selects a time variation model suitable for an output signal of a frequency source to be measured according to prior knowledge of the frequency source, primarily determines parameters of the frequency source model, calculates the output variation of the frequency source to be measured along with time, determines an optimal tracking period value and calculates the starting time of any tracking period. The invention can design the tracking period matched with the frequency source according to the performance characteristics of different frequency sources so as to adapt to the time change requirement of measuring the frequency source at a long distance and with high precision, provide support for keeping the frequency sources of each station synchronous, reduce the use condition of the satellite common-view technology and improve the usability.)

1. A common-view time planning method suitable for remote comparison of different types of frequency sources is characterized by comprising the following steps:

determining a common view starting time represented by UTC time;

step two, selecting a time change model of an output signal as the tested frequency source with the aging rate larger than 1e-17Selecting a time variation model of an output signal as T (t) ═ a + bt for a tested frequency source with the aging rate of less than or equal to 1e-17,wherein a represents the initial time deviation of the output signal of the tested frequency source and the reference signal, b is the time deviation change rate of the output signal of the frequency source, and c is the aging rate of the frequency source;

step three, when the frequency source model parameters are determined for the first time, making a equal to 0, using the frequency accuracy or frequency deviation quantity known by the measured frequency source as the value of b, and making c equal to 0;

step four, according to the frequency source parameters a, b and c of step three, the time parameter T is N × T_bWherein, T_bDetermining a value range of N for making 5ns less than T (T) less than 20ns by combining the time difference value T (T) result obtained by calculation, and substituting the formula T into N × T_bCalculating the minimum value t of the tracking period candidate interval_g(min)And maximum value t_g(max)；

Step five, taking the value of N as a simultaneous order three formulaMaximum integer of all, corresponding T'_cv＝N×T_bNamely, the tracking period of single common view measurement is determined in the stage of determining the tracking period for the first time;

step six, obtaining T'_cvAssigning to tracking period value T_cvCalculating the start time of any tracking period

t_cv(i)＝T₀+T_cv×i，i＝1，2，3，.....

T₀Indicating the start time of the co-view observation, i indicating that the tracking period is the second tracking period from the start time; so far, the start time of the common view time table, the tracking period, and the start time of any tracking period have all been determined.

2. The method of claim 1, wherein the method comprises: the common-view initial time is zero minute and zero second at zero time of any date, and a new file is generated every 24 hours by the common-view observation data file.

3. The method of claim 1, wherein the method comprises: when the use scene has a definite time ratio required for the expected range, the step is executed between the step four and the step five: calculating an expected tracking period according to the application requirement of the long-distance time comparison of the frequency source

4. The method of claim 1, wherein the method comprises: after the fifth step, if the aging rate parameter of the measured frequency source is known, executing the step: and taking the frequency deviation of the measured frequency source as a parameter b and a frequency aging rate c, and calculating to obtain T 'in the fifth step'_cvAs a time parameter, the value of T (t) is calculated, if the equation can still be usedIf yes, determining the optimal tracking period as T_cv＝T′_cv(ii) a Otherwise, judging according to conditions, if T (T) is less than or equal to 5ns, increasing the value of N by one, then switching to the step five for checking calculation, if yes, continuing to execute, otherwise, continuing to increase the value of the parameter N, repeating the step five until the step meets the requirements, and determining the optimal tracking period as T_cv＝T′_cv(ii) a If T (T) is more than or equal to 20ns, reducing the value of N by one, then transferring to the step five for checking calculation, if yes, continuing to execute, otherwise, continuing to reduce the value of the parameter N, repeating the step five until the step meets the requirement, and determining the optimal tracking period as T_cv＝T′_cv。

Technical Field

The invention relates to the field of time-frequency high-precision transmission, in particular to a common-view time planning method.

Background

The GPS satellite common view technology is one of the main methods for long-distance time comparison at present, and the uncertainty of the comparison can reach several nanoseconds. The basic principle is that any two places use a satellite clock as a common reference source, observe signals of the same navigation satellite at the same time, measure the deviation between local time and satellite clock time, and subtract after exchanging data between the two places, so that common errors including the satellite clock on two propagation paths can be offset, and the relative deviation of the two places in time can be obtained.

The GPS common-view time transfer method is proposed by D.W.Allan and C.Thomas in 1980, 1993 international time frequency Consulting Committee (CCTF) sets up a GPS common-view equipment software technology standard for standardizing the application of the GPS common-view method in TAI time comparison, and then sets up a GPS/GLONASS common-view related technology standard, 2006 CCTF combines the progress of the current navigation satellite common-view technology, and proposes to modify a common-view observation file format to the international committee so as to contain observation results of multiple systems.

The current GPS co-visibility standard data FORMATs are GGTTS GPS DATA FORMAT and CGGTTS-Version 2E, as established by the BIPM host, where the parameters associated with the co-visibility schedule are MJD and STTIME.

MJD: indicating the starting date (referenced to UTC) of the tracked satellite and the reduced julian day in 5-digit numbers. Julian Day (Julian Day) is a continuous long-term Day-of-the-Day method, denoted JD. The calculation days are recorded as one month and one day of the Confucian calendar from the afternoon of 4713 years before the lunar union of the world time, and the accumulation is carried out every day, so that the method is a common representation method for time in astronomy. The Julian date (Modified Julian Day) MJD is defined as MJD JD-2400000.5.

STTIME: indicating the starting time (hours, minutes, seconds referenced to UTC) for tracking the satellite.

The basic arrangement rule of the common view timetable is as follows: taking 0 point, 0 hour and 2 minutes on 1 day of 10 months and 1 in 1997 as starting points, each common-view tracking cycle is 16 minutes, wherein the first 2 minutes is preparation time, the last minute is observation time, the last minute is data calculation time, 89 common-view tracking segments of 16 minutes are included each day, in the observation period of each tracking cycle, 13 minutes are continuously tracked, once per second is observed, 780 data are observed for 13 minutes, the processing result of each common-view observation data is marked by the time of the first observation of the common-view observation data, the observation date adopts reduced julian day number, the time adopts UTC time, minutes and seconds for marking, the starting time of each day tracking observation is 4 minutes earlier than the previous day, and the purpose is mainly to be consistent with the sidereal time of the GPS satellite operation cycle, so that the satellites tracked by the common-view observation each day can be repeated.

The common view time calculation formula is as follows:

on day MJD 50722, the starting time of the 13 minute observation period is calculated as follows:

time _ ref (i) 00h02m00s + (i-1) × 16, where i ranges from [1,89]

The starting time calculation formula for the 13 minute observation period on any date is as follows:

time (i) -Time _ ref (i) -4 minutes x (MJD-50722), where 50722 is the reduced julian day corresponding to UTC Time 1997, 10/1.

According to the related content of the common-view time table and data processing in the current GNSS common-view standard CGGTTS-Version 2E, one-time common-view tracking lasts for 16 minutes, 780 observation data are subjected to multiple fitting to generate a clock error test result, and the method is more suitable for testing frequency sources with higher stability and accuracy. Taking a frequency source with the frequency accuracy of 5e-12 as an example, the time variation of the frequency source in a 16-minute tracking period is 4.8ns, and if the stability of the frequency source is also in the order of e-12, the fluctuation condition of the frequency source in one tracking period is hardly reflected by a test result, and thus the performance of the frequency source cannot be accurately evaluated. Therefore, the common view period of the current common view standard is only suitable for frequency sources with stability and accuracy superior to e-12 magnitude, and for frequency sources with accuracy or stability below e-12 magnitude, such as rubidium atomic clock or constant temperature crystal oscillator and other types, the common view comparison of a tracking period of 16 minutes is adopted, so that the test requirement is difficult to meet.

With the continuous increase of high-precision time synchronization application scenes, the time synchronization requirements of various applications including the communication field are improved to a nanosecond level, but an atomic clock with the accuracy of e-12 level is difficult to be widely used due to the price of tens of thousands or hundreds of thousands, a low-cost frequency source has poor accuracy and stability indexes, if a satellite is applied to commonly view inter-station time comparison, a measurement result can be updated every 16 minutes, and the inter-station time nanosecond synchronization is difficult to realize, so that the comparison of the existing standard commonly view technology to the low-cost frequency source is not applicable, and a new solution is needed.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a common-view time planning method suitable for remote comparison of different types of frequency sources, which can design a tracking period matched with the performance characteristics of the different frequency sources according to the performance characteristics of the different frequency sources so as to adapt to the time change requirement of measuring the frequency sources at a long distance and with high precision, provide support for keeping synchronization among the frequency sources of each station, reduce the use condition of a satellite common-view technology and improve the usability.

The technical scheme adopted by the invention for solving the technical problem comprises the following steps:

determining a common view starting time represented by UTC time;

step two, selecting a time change model of an output signal as the tested frequency source with the aging rate larger than 1e-17

For the frequency source to be measured with the aging rate of 1e-17 or less, selecting a time variation model of the output signal as T (t) ═ a + bt, wherein a represents the initial time deviation of the frequency source output signal to be measured and a reference signal, b is the time deviation variation rate of the frequency source output signal, and c is the aging rate of the frequency source;

step three, when the frequency source model parameters are determined for the first time, making a equal to 0, using the frequency accuracy or frequency deviation quantity known by the measured frequency source as the value of b, and making c equal to 0;

step four, according to the frequency source parameters a, b and c of step three, the time parameter T is N × T_bWherein, T_bDetermining a value range of N for making 5ns less than T (T) less than 20ns by combining the time difference value T (T) result obtained by calculation, and substituting the formula T into N × T_bCalculating the minimum value t of the tracking period candidate interval_g(min)And maximum value t_g(max)；

Step five, taking the value of N as a simultaneous order three formula

Maximum integer of all, corresponding T'_cv＝N×T_bI.e. a single common view measurement during the initial determination of the tracking periodA tracking period of (d);

step six, obtaining T'_cvAssigning to tracking period value T_cvCalculating the start time of any tracking period

t_cv(i)＝T₀+T_cv×i，i＝1，2，3，.....

T₀Indicating the start time of the co-view observation, i indicating that the tracking period is the second tracking period from the start time;

so far, the start time of the common view time table, the tracking period, and the start time of any tracking period have all been determined.

The common-view initial time is zero minute and zero second at zero time of any date, and a new file is generated every 24 hours by the common-view observation data file.

When the use scene has a definite time ratio required for the expected range, the step is executed between the step four and the step five: calculating an expected tracking period according to the application requirement of the long-distance time comparison of the frequency sourceWhere TD represents the expected difference between the two frequency sources in the long-distance time comparison determined by the demand, and thus the maximum value of the two-place time deviation for realizing time synchronization, b_AAnd b_BRepresenting the frequencies of the two frequency sources a and B respectively involved in the test.

After the fifth step, if the aging rate parameter of the measured frequency source is known, executing the step: and taking the frequency deviation of the measured frequency source as a parameter b and a frequency aging rate c, and calculating to obtain T 'in the fifth step'_cvAs a time parameter, the value of T (t) is calculated, if the equation can still be usedIf yes, determining the optimal tracking period as T_cv＝T’_cv(ii) a Otherwise, judging according to conditions, if T (t) is less than or equal to 5ns, increasing the value of N by one, then switching to the step five for checking calculation, if yes, continuing to execute, otherwise, continuing to increase the value of the parameter N, and repeating the step five until the step meets the requirementsIt is required to determine the optimum tracking period as T_cv＝T’_cv(ii) a If T (T) is more than or equal to 20ns, reducing the value of N by one, then transferring to the step five for checking calculation, if yes, continuing to execute, otherwise, continuing to reduce the value of the parameter N, repeating the step five until the step meets the requirement, and determining the optimal tracking period as T_cv＝T’_cv。

The invention has the beneficial effects that:

(1) the common-view timetable can be flexibly configured according to the requirement of the application scene on the time synchronization performance (comprising the common-view starting time in the step one and the TD value in the step five, the common-view starting time can be determined according to the user requirement, and the value of the TD value is determined according to the time synchronization performance of the application scene), so that the high-precision time synchronization requirement is met;

(2) the tracking period can be determined according to the performance condition of the frequency source to be detected and the optimal selection principle of the common-view timetable, so that the high-precision measurement and evaluation of the performance of the frequency source are realized, and the method is particularly suitable for the frequency source with poor performance such as accuracy, stability and the like;

(3) the common-view timetable is irrelevant to the satellite orbit period, the ephemeris updating period and the like, and can be applied to any satellite navigation system to carry out satellite common-view comparison, expand the application range and improve the availability of satellite common-view;

(4) continuous and gapless tracking periods of the common-view timetable are continuous, and compared with the existing standard, the common-view timetable has a 3-minute tracking gap, more available observation data are provided, and the reliability of an observation result is improved;

Detailed Description

The invention aims to provide a common view time planning method suitable for requirements of remote comparison and time difference measurement of different types of frequency sources, and mainly solves the following problems:

1) the usability of the common-view technology is improved, so that the common-view technology can meet the long-distance time comparison requirements of more types of frequency sources;

2) the problem of long-distance time high-precision comparison of non-high-performance frequency sources is solved, and long-distance and high-precision time comparison can be realized through satellite common view like frequency sources such as a crystal oscillator, a chip atomic clock, a rubidium atomic clock and the like;

3) the common-view tracking period can be freely selected according to requirements, and support is provided for obtaining a test result more quickly;

4) each time parameter of the common-view timetable is mainly related to the performance of a measured frequency source, the real-time requirement of a user on a time difference measurement result, the precision of the measurement result and other factors, and is unrelated to a satellite orbit period, an ephemeris update period and the like, so that the common-view timetable can be applied to all visible satellite navigation systems, including Beidou, GPS, GLONASS, Galileo and the like; the method can adapt to the comparison among frequency sources with different performances, and therefore, the method can be used for long-distance comparison among frequency sources with accuracy better than that of e-9 magnitude.

In order to achieve the purpose, the invention provides a common-view time planning method suitable for remote comparison of different types of frequency sources, a flexible and repeatable common-view time table is designed, the requirement of nanosecond-level time comparison application of diversified frequency sources is met, and support is provided for high-precision and remote comparison of common-performance frequency sources.

The invention mainly comprises a method for calculating the common-view tracking period by combining the measured frequency source performance and the application requirement.

The invention comprises the following contents:

the method comprises the following steps: determining the common-view starting time, wherein the common-view starting time is represented by UTC time, the default starting time is zero-minute zero-second of zero time of any date (wherein the 'time' can be specified by special requirements of users and is any integer of 0-23 hours), the common-view starting time determines the generation starting time of the common-view observation data file, and a new file is generated every 24 hours by the common-view observation data file;

step two: selecting a time variation model suitable for the output signal of the tested frequency source from the equations (1) and (2) according to the prior knowledge of the frequency source:

T(t)＝a+bt (2)

wherein a represents the initial time deviation of the measured frequency source output signal from the reference signal, b is the rate of change of the time deviation of the frequency source output signal, typically representing the frequency deviation of the measured frequency source from a standard or reference source, c is the rate of change of the frequency deviation, typically considered as the aging rate of the frequency source; aging rates greater than 1e-17 are generally considered to be relatively significant, and formula (2) is selected for frequency sources that do not have a significant aging rate, such as a cesium clock, a rubidium clock, and formula (1) is selected for oscillators that are significantly aged;

step three: the primary determination method of the frequency source model parameters comprises the following steps:

and (4) determining values of the parameters a, b and c (when the model selects the formula (2), the value of c does not need to be calculated) by using the historical time difference measurement data T (t) of the frequency source according to the time change model determined in the step two. Determining operation requirements according to a tracking period, and determining parameters in two stages of primary determination and feasibility rechecking;

the method mainly concerns the variation of a certain time period in the estimation of the time variation parameter, so that the initial time deviation does not influence the result, and therefore, a is 0;

the known frequency accuracy or frequency deviation amount of a measured frequency source is used as frequency deviation and is used as the value of the parameter b of the formula (1) or (2);

the value of the parameter c can be ignored in the primary determination stage, namely c is set to be 0;

step four: calculating the output variation T (t) of the frequency source to be detected along with time according to the frequency deviation parameter b of the frequency source to be detected obtained in the step three, aiming at determining the range of the available tracking period, wherein the calculation method comprises the following steps:

substituting the frequency source parameters a, b and c in the third step into the formula (1), wherein the value of the time parameter t in the formula (1) follows the formula (3):

t＝N×T_b(3)

in the formula (3), T_b15s represents a tracking basic period unit, N is an integer and represents a tracking period multiple, the value range is 1-80,

determining the value range of N for making 5ns less than T (t) less than 20ns according to the time difference T (t) result obtained by calculation in the combination formula (1), and calculating the minimum value t of the candidate value interval of the tracking period in the following formula (3)_g(min)And maximum value t_g(max)；

Step five: if the usage scenario has a definite time comparison requirement with the expected range, the step is executed, otherwise, the step is skipped.

Calculating an expected tracking period according to the application requirement of the long-distance time comparison of the frequency source, wherein the calculation formula is as follows:

wherein TD represents an expected difference value of two frequency sources in long-distance time comparison determined by requirements (the value range of TD satisfies 5-20 ns), so as to realize the maximum value of two-place time deviation of time synchronization, b_AAnd b_BRespectively representing the frequencies of two frequency sources A and B participating in the test;

step six: and determining the optimal tracking period value by combining the step four and the step five.

In view of the technical characteristics of satellite common view comparison, random measurement noise exists in signals transmitted by radio waves, and therefore the longer the tracking period is, the smaller the influence of the random measurement noise is, the maximum integer which makes the following three formulas simultaneously true is the value of N:

corresponding T'_cv＝N×T_bNamely, the tracking period of single common view measurement is determined in the stage of determining the tracking period for the first time; step seven: if the aging rate parameter of the measured frequency source is known, executing the step, and performing tracking cycle review, otherwise, skipping the step and entering the step eight.

Substituting the frequency deviation of the measured frequency source as a parameter b and a frequency aging rate c into a parameter item corresponding to the formula (1), and calculating to obtain T 'by applying the sixth step'_cvCalculating the value of T (T) in the formula (1) as a time parameter, and if the formula (6) can be satisfied, determining the optimal tracking period as T_cv＝T’_cv；

If the formula (6) does not work, judging according to conditions, if T (T) is less than or equal to 5ns, increasing the value of N by one, then transferring to the step six for checking calculation, if yes, continuing to execute, otherwise, continuing to increase the value of the parameter N, repeating the step six until the step seven meets the requirements, and determining that the optimal tracking period is T_cv＝T’_cv；

If the formula (6) does not work, judging according to conditions, if T (T) is more than or equal to 20ns, reducing the value of N by one, then switching to the step six for checking, if yes, continuing to execute, otherwise, continuing to reduce the value of the parameter N, repeating the step six until the step seven meets the requirements, and determining that the optimal tracking period is T_cv＝T’_cv；

Step eight: tracking period value T obtained according to the step seven_cvIf the condition that the seventh step does not satisfy is not executed, the T 'obtained in the sixth step is used'_cvIs assigned to T_cvCalculating the start time of any tracking period:

the starting time calculation formula for each tracking period is as follows:

t_cv(i)＝T₀+T_cv×i，i＝1，2，3，.....(5)

the common view schedule is repeated every 24 hours, T₀The starting time of each day of the common view observation is represented, the UTC time of one zero minute and zero second can be randomly specified, and the default zero minute and zero second of zero can be used as the starting time; i indicates that the tracking period is the next tracking period from the start time;

so far, the starting time of the co-view schedule, the tracking period and the starting time of any tracking period are all determined, namely, the key elements of the co-view schedule can be all determined by the method of the invention.

The present invention is further illustrated by the following examples, which include, but are not limited to, the following examples.

The method has the advantages that two rubidium atomic clocks with the accuracy of 2E-11 and the aging rate of 6.3E-18/s are respectively reference clocks of a place A and a place B, and the time of the rubidium atomic clocks needs to be kept synchronous (the time deviation of the places A and the place B is required to be less than 10ns) because the systems of the place A and the place B need to work cooperatively, at the moment, the method for planning the co-view time can be applied, the co-view comparison is carried out, and the operation flow is as follows:

the method comprises the following steps: determining the co-view starting time, wherein UTC time is used as the representation, the starting time is defined as zero minute and zero second of zero hour on any date (wherein, the 'hour' can be specified by special requirements of users and is any integer of 0-23 hours), and the co-view starting time is repeated every 24 hours;

step two: selecting a time variation model of a rubidium clock frequency source output signal:

where a represents the initial deviation of the frequency source output signal from the reference signal, b is the rate of change of the time deviation of the frequency source output signal, typically representing the frequency deviation of the frequency source from a standard or reference, and c is the rate of change of the slope, typically considered the aging rate of the frequency source.

Step three: model parameter determination for frequency sources:

according to the model of equation (1), the parameter b of equation (1) is taken to be 2e-11 by using the known frequency accuracy or frequency deviation amount of the measured frequency source, and the parameter a can be taken to be 0 in view of the fact that the change of the estimated frequency source in a certain period of time does not relate to the initial deviation, and the value of the parameter c is determined by the finally determined tracking period time length, and when the caused time change exceeds the expected time change, the parameter cannot be zero, otherwise the parameter is zero;

step four: determining the application range of the tracking period, bringing the accuracy of the frequency source into the formula (1) with the parameter b being 2e-11 and the parameter c being 0, and then calculating the minimum value t of the tracking period candidate value interval by the formula (2)_g(min)250s and a maximum value t_g(max)＝500s；

Step five: calculating the expected tracking period according to the application requirement, wherein the calculation formula is as follows:

step six: combining the fourth step and the fifth step, calculating a tracking period T 'meeting the requirement of formula (4)'_cv495s, corresponding N ═ 33, T'_cvNamely, the tracking period is obtained in the stage of primarily determining the tracking period;

step seven: substituting the aging rate c of the known frequency source to be measured to be 6.3E-18/s and the frequency accuracy b to be 2-11/s into the formula (1) to obtain T (T) to be (9.9E-9+7.7E-13) s, namely, the time change caused by the aging rate is far less than the nanosecond order, and substituting T (T) into the formula (5) is still true, so that the optimal tracking period T is determined_cv＝T’_cv＝495s。

Step eight: and C, calculating the starting time of any tracking period according to the tracking period value obtained in the step seven:

the starting time calculation formula for each tracking period is as follows:

T(i)＝T₀+495×i,i＝1,2,3,.....(3)

the common view schedule is repeated every 24 hours, T₀Representing the starting time of each day of the co-view observation, using the default zero hour, zero minutes and zero seconds; i indicates that the tracking period is the next tracking period from the start time.

So far, the starting time of the common view schedule, the tracking period and the starting time of any tracking period are all determined, and the determination of the key elements of the common view schedule is completed.