CN104238352A - National benchmark controlled local time standard generating system and method - Google Patents

Abstract

The invention provides a national benchmark controlled local time standard generating system and method and belongs to the field of time frequency calibration. The national benchmark controlled local time standard generating system comprises a GSP (global position system) receiver, a time-interval counter, a local atomic clock and a computer; the GSP receiver and the time-interval counter are respectively connected with the computer; the GSP receiver and the local atomic clock are respectively connected with the time-interval counter; the time-interval counter takes a 1pps (pulse per second) signal outputted by the local atomic clock as a door opening pulse and a 1pps signal outputted by the GSP receiver as a door closing pulse, the difference value between the two pulses per second is measured to be the time-interval measurement value; the computer generates a local standard format file by the aid of the different value and information acquired by the GSP receiver; the local standard format file and a standard file generated according to national standard are then compared to generate local standard time.

Description

The local time standard generation system and method that a kind of National primary standard is controlled

Technical field

The invention belongs to temporal frequency calibration field, the local time standard generation system and method being specifically related to that a kind of National primary standard controls.

Background technology

Time is one of seven fundamental physical quantities in International System of Units, is the physical quantity that in current all physical quantitys, accuracy is the highest.The range of application of temporal frequency is from great scientific experiment to daily personal consumption, and purposes is all very extensive.Along with the fast development of satellite navigation industry, the detection demand of navigation Related product constantly expands.Navigation product and the accurate of equipment are all based upon on the accurate basis of satellite reception module time value with stablizing, and therefore satellite reception module time value is accurately ensure that navigator data are basic accurately and reliably.The local time standard that time quantum value transmit needs to set up accurate stable is carried out to satellite navigation product, usually be made up of atomic clock or clock group, i.e. atomic time scale, free markers can be divided into and control markers, one time in target computation process, as do not added the calibration (directly or indirectly) of time and frequency standards, then the markers produced becomes free markers, otherwise is called and controls markers.The atomic time scale accuracy that metering institute of China keeps is better than 1 × 10 ^-13, degree of stability is better than 5 × 10 ^-14, be the highest Time and frequency standard of China.Current China each place time standard is mostly free markers, is made up of rubidium or cesium-beam atomic clock, and accuracy is usually 1 × 10 ^-12, be obviously inadequate for the high-precision navigation time module of calibration.Because atomic clock has drift phenomenon, need regularly to calibrate, use clock carrying can realize synchronously, be transported to upper level measurement unit every year by atomic clock and carry out assay calibration, but a large amount of manpower and financial resources can be wasted like this, the standard device powering up operation is for a long time had no idea to realize real-time tracing to the source especially.And markers of controlling domestic at present is also just traceable to gps time, easily depending on GPS System in USA, is not a kind of independent markers.

GPS is the long-range transmission method of temporal frequency extensively adopted in the world depending on method altogether, transmits uncertainty and can be several nanosecond.Refer in the visual angle of a gps satellite depending on method altogether, on the earth, the time signal of same the satellite that the atomic clock of any two places can utilize the same time to receive carries out temporal frequency comparison.Also be one of technical way of International Atomic Time cooperation altogether depending on method.Current GPS has developed quite ripe depending on technology altogether, but domestic also do not utilize be traceable to National primary standard depending on method altogether control markers, and foreign GPS is only limitted to the comparison between country and national Time and frequency standard depending on technology altogether, without related application in time quantum value transmit, therefore real-time time quantum value transmit cannot be carried out to satellite navigation product.

Summary of the invention

The object of the invention is to solve the difficult problem existed in above-mentioned prior art, the local time standard generation system and method providing a kind of National primary standard to control, local atomic clock is made to be traceable to the time reference UTC (NIM) of metering institute of China depending on method altogether by GPS, generate local time standard UTC (BIM), synchronization accuracy remains on ± 10ns within, achieve real-time transmission of quantity value, meet the detection demand of navigation product.

The present invention is achieved by the following technical solutions:

The local time standard generation system that National primary standard is controlled, comprises GPS, time-interval counter, local atomic clock and computing machine;

Described GPS and time-interval counter are connected with described computing machine respectively;

Described GPS is connected with described time-interval counter respectively with local atomic clock;

The 1pps signal that local atomic clock exports by described time-interval counter is as enabling nulse, and 1pps signal GPS exported, as pass gate pulse, is measured the difference between two pulse per second (PPS)s, is time interval measurement value;

Described computing machine utilizes described difference and generates local standard formatted file from the information that GPS obtains; Then the normative document that local standard formatted file and National primary standard produce is compared, generate local local standard time.

Described GPS is connected with computing machine by serial ports, and time-interval counter is connected with computing machine by another serial ports;

GPS and local atomic clock are respectively time-interval counter and provide 1pps pulse.

Described GPS adopts dual-frequency receiver, can receive CA code, L1/L2 two-frequency signal;

Described time-interval counter adopts high precision time interval counter;

Described local atomic clock adopts GPS can tame and docile rubidium atomic clock, frequency accuracy 1 × 10 ^-12.

Utilize the ionospheric delay that GPS records in L1 and L2 two frequency ranges, revise time delay value, correction formula is as follows:

$\mathrm{PR}=\frac{{\mathrm{PR}}_2-\mathrm{\γ}{\mathrm{PR}}_1}{1-\mathrm{\γ}}---\left(4\right)$

Wherein, PR _i(i=1,2) are the ionospheric delay measured values respectively in L1 and L2 frequency range, and PR is the double frequency ionospheric corrections value calculated by the linear combination of two frequency range ionospheric delays;

γ following formula calculates:

γ＝(f _L1/f _L2) ²＝(1575.42/1227.6) ²＝(77/60) ² (5)

F _l1and f _l2be respectively the frequency of L1 and L2 frequency range.

Described GPS is set to the measurement pattern of ionofree, can revise ionospheric delay more accurately.

When GPS starts, use automatic positioning function, first make GPS be in the pattern of cruising, calculate average coordinates after 24 hours, then be set to fixed mode, higher positioning precision can be obtained.

The local time standard generation method that a kind of National primary standard utilizing described system to realize is controlled, comprising:

At enabling nulse per second with after closing gate pulse, before lower one-second burst arrives, the time interval measurement value that computing machine time of receipt (T of R) interval counter is sent and the corresponding information obtained from GPS, the series of parameters for comparison is obtained, by all parameter read-in local standard formatted files after it is processed;

The normative document that local standard formatted file and National primary standard produce is compared, generates local local standard time.

The described normative document by local standard formatted file and National primary standard generation is compared, and generates local local standard time and is achieved in that

Poor under same PRN, MJD, STTIME condition by the parameter REFGPS in the normative document to local standard formatted file and National primary standard generation, obtain a series of difference, after rejecting the abnormal data in difference, vondrak filtering is carried out to difference data, every day a mean value is asked to the data obtained, specific as follows:

If the time that national time reference produces is t (NIM), the time that local atomic clock produces is t (BIM), t (GPS) is gps time, REFGPS (NIM) and REFGPS (BIM) is respectively the REFGPS parameter value in the normative document of two places, then:

REFGPS(NIM)＝t(NIM)-t(GPS) (1)

REFGPS(BIM)＝t(BIM)-t(GPS) (2)

REFGPS(NIM)-REFGPS(BIM)＝t(NIM)-t(BIM) (3)

Described t (NIM) is national time reference, utilizes REFGPS (NIM)-REFGPS (BIM) to calibrate local atomic clock, and the t (BIM) after calibration is defined as local local standard time;

Process obtaining a series of REFGPS (NIM)-REFGPS (BIM) data sequence every day, namely after rejecting abnormalities data, through vondrak filtering Removing Random No, then average, as the modified value of the local standard time of calibration this locality.

In the process of comparing, select the data of more than 30 °, satellite elevation angle to calculate.

GPS uses smoothing the phase of carrier wave data, and smooth spaces is set to 300s.

Described method comprises further:

Conic fitting is done to the data of the local standard time of this locality and obtains predicting equation, estimate out current data by historical data, thus send to the pulse per second (PPS) of navigation product to revise to local atomic clock, realize transmission of quantity value.

Compared with prior art, the invention has the beneficial effects as follows: present invention achieves the mode of operation being controlled existing temporal frequency measurement standard by national Time and frequency standard, fill up the blank in existing temporal frequency system, thus the transmission achieved satellite navigation product time value, for the detection of navigation product and equipment provides necessary technical foundation.

Accompanying drawing explanation

Fig. 1 is the local time standard generation system structural drawing that National primary standard of the present invention is controlled

Fig. 2 looks comparing process flow diagram altogether

Fig. 3 common-view mode filtering anterioposterior curve figure (16min point)

Fig. 4 common-view mode result curve figure (one day point)

Fig. 5 predicting equation curve map of front 9 day data prediction the 10th day data.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail:

The present invention utilizes rubidium atomic frequency standard, GPS dual-frequency receiver and time-interval counter to build a set of GPS common-view time transmission system, generates the standard format files meeting International Bureau of Wieghts and Measurements and formulate; Utilize local to produce and the normative document of metering institute of China is compared, generate Beijing local standard time UTC (BIM), make UTC (BIM) synchronous with national time reference UTC (NIM) within ± 10ns.

GPS is connected with computing machine by serial ports 1, and time-interval counter is connected with computing machine by serial ports 2, and GPS is connected with time-interval counter respectively with Rb atom frequency marking (the local atomic clock namely in Fig. 1).The 1pps signal that Rb atom frequency marking exports by time-interval counter is as enabling nulse, and 1pps signal GPS exported, as pass gate pulse, measures the difference between two pulse per second (PPS)s.After switch gate pulse per second, before lower one-second burst arrives, computing machine can the time interval measurement value (i.e. the difference of Rb atom frequency marking and gps time) sent of time of receipt (T of R) interval counter and (comprise the time of gps satellite from the corresponding information that GPS obtains, position, state, track, ephemeris etc. information), the series of parameters for comparison can be obtained after data processing software process, finally write in CCTF (time-frequency advisory committee) specified standard data file (i.e. the local normative document generated), for comparing.That the modified value utilizing comparison data to calculate calibrates navigation product to after the pulse per second (PPS) correction of local atomic clock from local atomic clock to the calibration of navigation product in Fig. 1.

Parameter for comparison mainly contains: PRN, MJD, STTIME, ELV, REFGPS, and wherein, PRN is the pseudorandomcode number of satellite, and its available satellite range is from 1 to 32.From GPS decoded information; MJD is the starting date (with reference to UTC) of tracking satellite, the starting date that 5 figure places represent; STTIME be tracking satellite initial time (with reference to UTC hour, minute, second).The arrangement regulation of multichannel receiver timetable is as follows: using during 1 day 0 October in 1997 2 points as starting point, the cycle of timetable is 89 16min, adds a 12min.Therefore, the initial time of to be 16min, STTIME be every secondary tracking period every secondary tracking period; ELV is actual satellite elevation angle of following the tracks of corresponding to period mid point.Unit 0.1dg.From GPS decoded information; REFGPS is the difference of actual tracking period midpoint, local pulse per second (PPS) and GPS pulse per second (PPS), unit 0.1ns.Receiver Software standardized technique guide specification every secondary tracking gps satellite time is 780 seconds, within 780 seconds, be divided into 52 15 seconds, conic fitting is carried out to the time interval value least square method that every 15 seconds record, obtains 52 mid point of curve values respectively, then carry out every time delay correction.Then carry out linear fit by least square method to 52 midranges more respectively, obtaining straight line midrange is exactly REFGPS.

The normative document (normative document of metering institute of China measures institute by China to be provided) utilizing local and Chinese metering institute to generate respectively is compared, clock correction (the i.e. time difference of two places can be obtained, modified value averages the intraday time difference to calculate), make local atomic clock be traceable to the UTC (NIM) of metering institute of China.In Fig. 1, UTC (NIM) remote calibration refers to and utilizes GPS as medium, and two places atomic clock is poor with GPS respectively, utilizes difference data like this, and UTC (NIM) just can the atomic frequency standard of remote calibration this locality.

Two places normative document comparison process is: by poor under same PRN, MJD, STTIME condition to the parameter REFGPS in two normative documents, obtain an a series of difference (corresponding time point of difference, every 16min mono-) be absolute error between the atomic clock of two places, difference data is analyzed, the two places time difference can be obtained.If the time that metering institute of China atomic clock produces is t (NIM), the time that Beijing metering institute's atomic clock (the local atomic clock namely in Fig. 1) produces is t (BIM), t (GPS) is gps time, REFGPS (NIM) and REFGPS (BIM) is respectively the REFGPS parameter value in the normative document of two places, because two places are all using local pulse per second (PPS) as enabling, GPS pulse per second (PPS) as closing the door, then:

REFGPS(NIM)＝t(NIM)-t(GPS) (1)

REFGPS(BIM)＝t(BIM)-t(GPS) (2)

REFGPS(NIM)-REFGPS(BIM)＝t(NIM)-t(BIM) (3)

The time t (NIM) that metering institute of China atomic clock produces is national time reference UTC (NIM), by formula (3), t (BIM) after calibration, by being traceable to UTC (NIM) (utilizing REFGPS (NIM)-REFGPS (BIM) to calibrate) after the difference calibration of REFGPS, is defined as the local standard time UTC (BIM) (namely Fig. 1 Computer exports) of Beijing metering institute by the time t (BIM) that Beijing metering institute atomic clock produces.Can obtain such every day a series of (REFGPS (NIM)-REFGPS (BIM)), after these data sequence rejecting abnormalities data, through vondrak filtering Removing Random No, then average, as the modified value of calibration UTC (BIM).

In order to make UTC (BIM) synchronous with UTC (NIM) within ± 50ns, following measures is adopted to improve synchronization accuracy: (1) selects dual-frequency receiver, can revise ionospheric delay more accurately; (2) receiver is arranged at position fixed mode; (3) elevation angle selects the data of more than 30 ° to calculate.

The UTC (BIM) generated will provide real-time transmission of quantity value for satellite navigation product, need the pulse per second (PPS) through revising in real time, therefore conic fitting is done to the data of UTC (BIM) and obtain predicting equation, current data is estimated out by historical data, thus pulse per second (PPS) (being that local atomic clock sends to navigation product) is revised, realize transmission of quantity value.

As shown in Figure 1, hardware of the present invention is configured to rubidium atomic frequency standard, GPS, time-interval counter and computing machine.In a preferred embodiment of the invention, the receiver of the SIGMA model that GPS selects JAVAD company to produce, can receive CA code, L1/L2 two-frequency signal, measure ionospheric delay more accurately, thus obtain higher timing accuracy.In time interval measurement, what select is the SR-620 high precision time interval counter of SRS company, and best result distinguishes that precision reaches 25ps.Rubidium atomic frequency standard is that the 910R model GPS that Fiuke Co., Ltd produces can tame and docile rubidium atomic clock, frequency accuracy 1 × 10 ^-12.GPS is connected with computing machine by serial ports 1, and time-interval counter is connected with computing machine by serial ports 2, and receiver and Rb atom frequency marking are respectively time-interval counter and provide 1pps pulse.

In order to improve comparison accuracy, reducing synchronous error, necessary setting need be carried out to receiver, being described in detail below:

(1) dual-frequency receiver can utilize the impact of ionosphere on microwave signal to have dispersion characteristics, and with the ionospheric delay that L1/L2 two frequencies record, calculate more accurate time delay value, correction formula is as follows:

$\mathrm{PR}=\frac{{\mathrm{PR}}_2-\mathrm{\γ}{\mathrm{PR}}_1}{1-\mathrm{\γ}}---\left(4\right)$

Wherein, PR _i(i=1,2) are the ionospheric delay measured values respectively in L1 and L2 frequency range, and PR is the double frequency ionospheric corrections value calculated by the linear combination of two frequency range ionospheric delays.And γ following formula calculates:

γ＝(f _L1/f _L2) ²＝(1575.42/1227.6) ²＝(77/60) ² (5)

Because the ionosphere time delay of two frequency ranges is different, can better be revised ionospheric delay by correction formula (4), (5).

Receiver has 4 kinds of pseudo range measurement types: ca code, p1 code, p2 code and ionofree, first 3 kinds is only measure by the single-frequency that a kind of code carries out, and ionofree is the combination of front 3 kinds of codes, this measurement pattern revises pseudorange with double frequency actual measurement ionospheric delay, therefore consequently by ionosphere effect.Receiver is set to the measurement pattern of ionofree, can revise ionospheric delay more accurately.

(2) whether receiver antenna coordinate is accurately the key factor affecting comparison accuracy.Receiver has two kinds of station-keeping modes: fixed mode and pattern of cruising.Receiver can calculate aerial position coordinate in real time under the pattern of cruising, and then uses the stationary coordinate that known under fixed mode.When receiver is in static state, and when being mainly used in regularly applying, use fixed mode that 1pps pulse can be made better to be synchronized to GPS markers, thus improve synchronization accuracy, therefore receiver should be arranged at fixed mode.When receiver starts, use automatic positioning function, first make receiver be in the pattern of cruising, calculate average coordinates after 24 hours, then be set to fixed mode, higher positioning precision can be obtained.

(3) main error source of gps time Frequency Transfer is Atmospheric Refraction Error and multipath effect, the impact of these error sources on precision is relevant with satellite elevation angle, the elevation angle is less, and common-view mode error is larger, therefore should remove low elevation angle satellite data to improve comparison accuracy.In comparison, select the data at more than 30 °, the elevation angle to calculate.

(4) receiver can carry out code observation, also can carry out carrier phase observation.P3 code eliminates ionospheric impact, and accuracy of observation is improved greatly, but also has its shortcoming: when satellite elevation angle is low, and observation is affected comparatively large, and short-term stability is poor.Carrier phase is lower than P code noise level, but there is the problem of integer ambiguity, and the P3 code of smoothing the phase of carrier wave in conjunction with the advantage of two kinds of observations, can reduce observation noise.Therefore, use smoothing the phase of carrier wave data, smooth spaces is set to 300s.

Two places normative document comparison process as shown in Figure 2, be specially: by poor under same PRN, MJD, STTIME condition to the parameter REFGPS in two normative documents, obtain a series of difference, rejecting abnormalities data, vondrak filtering is carried out to difference data, the data obtained ask a mean value, as the two places time difference every day.

For 10 day data between MJD56451-56460, the UTC data of measuring institute with China are compared, and the elevation angle gets more than 30 °, and every 16min sampling spot, result as shown in Figure 3.

As seen from Figure 3, filtered data eliminate random noise, more smoothly, more can reflect true clock correction, and the standard deviation of data is 6.2ns, meets the re-set target being not more than 10ns.

Fig. 3 data are asked 1 mean value every day, is the two places time difference finally obtained, as shown in Figure 4.These data can be used as modified value during calibration navigation product, make calibration data directly be traceable to National primary standard.

Just modified value can be obtained because a day data must collect, so the data on calibration navigation product same day cannot be revised in real time, need second day ability correction by the time, in order to realize real-time correction, data a few days ago can be used to do conic fitting, obtain predicting equation, utilize equation to estimate out the modified value on the same day, accomplish real-time correction.

Such as, estimate the data of MJD56460 by 9 day data between MJD56451-56459, if x=1,2 ..., 10, make conic fitting as shown in Figure 5, trying to achieve equation is:

y＝3.7413x ²-40.697x-1372.9

X=10 is substituted into equation, tries to achieve y=-140.6ns, be the advance estimate modification value of MJD56460, the measured value of MJD56460 is-143.2ns, and predictor error is-140.6ns-(-143.2ns)=2.6ns.

When MJD56460 utilized the pulse per second (PPS) calibration navigation product of local time standard generation system the same day, if to survey data be T ₀, then revised data are: T=T ₀+ 140.6ns.

Technique scheme is one embodiment of the present invention, for those skilled in the art, on the basis that the invention discloses application process and principle, be easy to make various types of improvement or distortion, and the method be not limited only to described by the above-mentioned embodiment of the present invention, therefore previously described mode is just preferred, and does not have restrictive meaning.

Claims (10)

1. the local time standard generation system controlled of National primary standard, is characterized in that: the local time standard generation system that described National primary standard is controlled comprises GPS, time-interval counter, local atomic clock and computing machine;

Described GPS and time-interval counter are connected with described computing machine respectively;

Described GPS is connected with described time-interval counter respectively with local atomic clock;

The 1pps signal that local atomic clock exports by described time-interval counter is as enabling nulse, and 1pps signal GPS exported, as pass gate pulse, is measured the difference between two pulse per second (PPS)s, is time interval measurement value;

Described computing machine utilizes described difference and generates local standard formatted file from the information that GPS obtains; Then the normative document that local standard formatted file and National primary standard produce is compared, generate local local standard time.

2. the local time standard generation system controlled of National primary standard according to claim 1, is characterized in that: described GPS is connected with computing machine by serial ports, and time-interval counter is connected with computing machine by another serial ports;

GPS and local atomic clock are respectively time-interval counter and provide 1pps pulse.

3. the local time standard generation system controlled of National primary standard according to claim 2, is characterized in that: described GPS adopts dual-frequency receiver, can receive CA code, L1/L2 two-frequency signal;

Described time-interval counter adopts high precision time interval counter;

Described local atomic clock adopts GPS can tame and docile rubidium atomic clock, frequency accuracy 1 × 10 ^-12.

4. the local time standard generation system controlled of National primary standard according to claim 3, is characterized in that: utilize the ionospheric delay that GPS records in L1 and L2 two frequency ranges, revise time delay value, correction formula is as follows:

$\mathrm{PR}=\frac{{\mathrm{PR}}_2-\mathrm{\γ}{\mathrm{PR}}_1}{1-\mathrm{\γ}}---\left(4\right)$

Wherein, PR _i(i=1,2) are the ionospheric delay measured values respectively in L1 and L2 frequency range, and PR is the double frequency ionospheric corrections value calculated by the linear combination of two frequency range ionospheric delays;

γ following formula calculates:

γ＝(f _L1/f _L2) ²＝(1575.42/1227.6) ²＝(77/60) ² (5)

F _l1and f _l2be respectively the frequency of L1 and L2 frequency range.

5. the local time standard generation system controlled of National primary standard according to claim 4, is characterized in that: described GPS is set to the measurement pattern of ionofree.

6. the local time standard generation system controlled of National primary standard according to claim 5, it is characterized in that: when GPS starts, use automatic positioning function, first make GPS be in the pattern of cruising, calculate average coordinates after 24 hours, then be set to fixed mode.

7. the local time standard generation method that a kind of National primary standard utilizing the arbitrary described system of claim 1 to 6 to realize is controlled, is characterized in that: described method comprises:

At enabling nulse per second with after closing gate pulse, before lower one-second burst arrives, the time interval measurement value that computing machine time of receipt (T of R) interval counter is sent and the corresponding information obtained from GPS, the series of parameters for comparison is obtained, by all parameter read-in local standard formatted files after it is processed;

The normative document that local standard formatted file and National primary standard produce is compared, generates local local standard time.

8. the local time standard generation method controlled of National primary standard according to claim 7, is characterized in that: describedly the normative document that local standard formatted file and National primary standard produce compared, and generates local local standard time and is achieved in that

Poor under same PRN, MJD, STTIME condition by the parameter REFGPS in the normative document to local standard formatted file and National primary standard generation, obtain a series of difference, after rejecting the abnormal data in difference, vondrak filtering is carried out to difference data, every day a mean value is asked to the data obtained, specific as follows:

If the time that national time reference produces is t (NIM), the time that local atomic clock produces is t (BIM), t (GPS) is gps time, REFGPS (NIM) and REFGPS (BIM) is respectively the REFGPS parameter value in the normative document of two places, then:

REFGPS(NIM)＝t(NIM)-t(GPS) (1)

REFGPS(BIM)＝t(BIM)-t(GPS) (2)

REFGPS(NIM)-REFGPS(BIM)＝t(NIM)-t(BIM) (3)

Described t (NIM) is national time reference, utilizes REFGPS (NIM)-REFGPS (BIM) to calibrate local atomic clock, and the t (BIM) after calibration is defined as local local standard time;

Process obtaining a series of REFGPS (NIM)-REFGPS (BIM) data sequence every day, namely after rejecting abnormalities data, through vondrak filtering Removing Random No, then average, as the modified value of the local standard time of calibration this locality.

9. the local time standard generation method controlled of National primary standard according to claim 8, is characterized in that: in the process of comparing, select the data of more than 30 °, satellite elevation angle to calculate;

GPS uses smoothing the phase of carrier wave data, and smooth spaces is set to 300s.

10. the local time standard generation system controlled of National primary standard according to claim 7, is characterized in that: described method comprises further:

Conic fitting is done to the data of the local standard time of this locality and obtains predicting equation, estimate out current data by historical data, thus send to the pulse per second (PPS) of navigation product to revise to local atomic clock, realize transmission of quantity value.