CN110912636A

CN110912636A - Multi-station real-time bidirectional time comparison method

Info

Publication number: CN110912636A
Application number: CN201911140070.6A
Authority: CN
Inventors: 王海峰; 张升康; 王学运; 王宏博; 易航; 王艺陶
Original assignee: Beijing Institute of Radio Metrology and Measurement
Current assignee: Beijing Institute of Radio Metrology and Measurement
Priority date: 2019-11-20
Filing date: 2019-11-20
Publication date: 2020-03-24

Abstract

The invention discloses a multi-station real-time bidirectional time comparison method, which is applied to time synchronization among multiple stations and comprises the following steps: the number of the sites is N, one site is selected from the N sites as a master site, and the rest N-1 sites are slave sites; the N stations transmit burst spread spectrum modulation signals by taking respective second signals as starting references, the time occupied by the spread spectrum modulation signals is M code periods, the duration time of one code period is T, and N, M and T meet the condition that T M N is less than or equal to 1 s; the method comprises the steps that N-1 slave stations receive spread spectrum modulation signals of a master station and obtain pseudo range measurement value sequences PD1 from the master station to the N-1 slave stations, the master station receives the spread spectrum modulation signals of the N-1 slave stations and obtains pseudo range measurement value sequences PD2 from the N-1 slave stations to the master station, and the time difference sequence between the N-1 slave stations and the master station is PD (PD1-PD 2)/2; the N-1 secondary stations adjust the time according to the time difference sequence PD. Compared with the prior art, the technical scheme of the invention can not generate multiple access interference and near-far effect.

Description

Multi-station real-time bidirectional time comparison method

Technical Field

The invention relates to the field of high-precision time synchronization among stations, in particular to a multi-station real-time two-way time comparison method capable of resisting multiple access interference and near-far effect.

Background

The time comparison by the two-way method is the internationally recognized highest-precision time comparison method at present, is widely applied to the field of high-precision time frequency magnitude remote comparison, and has no substitution in the positions of time frequency magnitude transmission and tracing methods. The bidirectional time comparison utilizes a signal spread spectrum modulation technology to carry out high-precision spread spectrum modulation transmission on related information of a timing signal, the signal is transmitted through a satellite, a microwave or an optical fiber link, and a remote comparison station carries out quick acquisition, precise tracking and precise resolving on the signal to obtain signal propagation delay. By exchanging propagation delay data, time difference information between the stations can be accurately obtained, and nanosecond time synchronization level can be obtained. The bidirectional method is widely applied to multiple fields of satellite navigation ground stations, radar networking, deep space exploration and the like.

In the prior art, bidirectional time synchronization is realized by adopting a multichannel microwave bidirectional time comparison system and a continuous wave code division multiple access mode. Unlike satellite navigation systems with low signal-to-noise ratio, the two-way time comparison system is a high signal-to-noise ratio system, and multiple access interference is easily generated among different channels. Meanwhile, the distances between nodes in the system are greatly different, and the acquisition and tracking of weak signals are obviously influenced by multiple access interference from strong signals. In addition, when the frequency of a multiple access interference signal and a desired signal changes to a specific relationship along with the movement of a station, a pseudo code tracking error formed by the multiple access interference is very obvious, the pseudo range measurement precision is greatly influenced, and the nanosecond-level time synchronization precision is difficult to achieve. This phenomenon is particularly evident in international satellite bidirectional comparison systems and short-range multi-site time comparison systems.

In view of the above, the present invention provides a multi-station real-time two-way time comparison method to alleviate the problems of multiple access interference and near-far effect in the prior art.

Disclosure of Invention

In order to solve the above technical problems, an object of the present invention is to provide a multi-station real-time bidirectional time comparison method, so as to alleviate the problems in the prior art.

A multi-station real-time two-way time comparison method is applied to time synchronization among multiple stations and comprises the following steps: the number of the sites is N, one site is selected from the N sites as a master site, and the rest N-1 sites are slave sites; the N stations transmit burst spread spectrum modulation signals by taking respective second signals as starting references, the time occupied by the spread spectrum modulation signals is M code periods, the duration time of one code period is T, and N, M and T meet the condition that T M N is less than or equal to 1 s; the method comprises the steps that N-1 slave stations receive spread spectrum modulation signals of a master station and obtain pseudo range measurement value sequences PD1 from the master station to the N-1 slave stations, the master station receives the spread spectrum modulation signals of the N-1 slave stations and obtains pseudo range measurement value sequences PD2 from the N-1 slave stations to the master station, and the time difference sequence between the N-1 slave stations and the master station is PD (PD1-PD 2)/2; the N-1 secondary stations adjust the time according to the time difference sequence PD.

Further, the measurement of the time difference sequence PD between the N-1 slave stations and the master station is repeated, and the N-1 slave stations adjust the time according to the time difference sequence PD.

The invention has the following beneficial effects:

the technical scheme provided by the invention can have the following beneficial effects: the technical scheme provided by the invention carries out time slot allocation on the multiple stations, adopts a periodic burst ranging communication mode to carry out high-precision time comparison, and completely separates signals transmitted among the stations on the time domain without generating multiple access interference and near-far effect.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are one embodiment of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic flow chart of a multi-station real-time two-way time comparison method according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a time domain relationship of signals transmitted by stations without time synchronization among multiple stations according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a time domain relationship of signals transmitted by stations after a first time of time synchronization among multiple stations according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a time domain relationship of signals transmitted by stations after multiple time synchronizations among multiple stations according to an embodiment of the present invention.

Detailed Description

To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and the described embodiments are some, but not all embodiments of the present invention.

Fig. 1 is a schematic flow chart of a multi-station real-time bidirectional time comparison method according to an embodiment of the present invention, and as shown in fig. 1, the method includes the following five steps.

Step S101: the N stations transmit burst spread spectrum modulated signals with respective second signals as a starting reference. Specifically, the number of stations is N, one station is selected from among the N stations as a master station, and the remaining N-1 stations are slave stations. The master station is used as a time reference, and a station with the most accurate time can be manually designated or selected as the master station.

And the N sites transmit burst spread spectrum modulation signals by taking respective second signals as starting references, the time occupied by the spread spectrum modulation signals is M code periods, the duration of one code period is T, and N, M and T meet the condition that T M N is less than or equal to 1 s. It should be noted that, as the number N of stations increases, the more the number N of time slots allocated to the time slot with the duration of 1s, the shorter the time occupied by the signal of each station is 1/N, which may result in that the code period M is less than 1, in which case each station cannot perform normal ranging operation and the system cannot operate normally. Therefore, the chip rate and the chip length of the comparison signal need to be adjusted according to the number N of stations participating in the comparison, so that the number M of the signal duration code periods of each station is greater than 1, and each station can be ensured to normally perform time difference comparison.

Step S102: a sequence of pseudorange measurements PD1 from the primary station to N-1 secondary stations is obtained. Specifically, because each station can transmit signals for M periods, the autocorrelation and cross-correlation system based on the pseudo code ranging is still satisfied, and periodic reception and distance measurement of the signals can be realized. The N-1 slave stations receive the spread spectrum modulation signals of the master station and obtain a pseudo range measurement value sequence PD1 from the master station to the N-1 slave stations, and the PD1 contains the distance from each slave station to the master station.

Step S103: a sequence of N-1 pseudorange measurements from the secondary station to the primary station is obtained PD 2. Specifically, the master station receives spread spectrum modulation signals of N-1 slave stations, obtains a pseudo range measurement value sequence PD2 from the N-1 slave stations to the master station, and the time difference sequence between the N-1 slave stations and the master station is PD ═ PD1-PD 2)/2. Note that the PD1 includes a time difference between the primary slave and the master, and the PD2 includes a time difference between the primary reverse slave and the master. Therefore, the time difference sequence between N-1 slave stations and the master station is PD ═ (PD1-PD 2)/2.

Step S104: and the N-1 slave stations adjust the time according to the time difference sequence. As shown in fig. 2, the probability of overlapping of the signals transmitted by the stations in the time domain is very high without time synchronization, and mutual interference is easily generated. After the N-1 slave stations adjust the time according to the time difference sequence, as shown in fig. 3, the N-1 slave stations adjust the respective time to align with the master station time, and obtain a new time domain relationship of the transmitted signals, and the signals of the stations are roughly separated in the time domain but have slight overlap.

Step S105: and repeating the time adjustment of the N-1 slave stations. Specifically, steps S101 to S104 are repeated to completely separate signals transmitted between stations in the time domain, so that multiple access interference and near-far effect are not generated, and finally, time synchronization accuracy between N stations in ns seconds or less can be achieved. As shown in fig. 4, after a plurality of time synchronizations, the signals transmitted between the stations are completely separated in the time domain.

Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A multi-station real-time two-way time comparison method is applied to time synchronization among multiple stations and is characterized by comprising the following steps:

the number of the sites is N, one site is selected from the N sites as a master site, and the rest N-1 sites are slave sites;

the N stations transmit burst spread spectrum modulation signals by taking respective second signals as starting references, the time occupied by the spread spectrum modulation signals is M code periods, the duration time of one code period is T, and the N, M and the T meet the condition that T M N is less than or equal to 1 s;

the N-1 slave stations receive the spread spectrum modulation signals of the master station to obtain pseudo range measurement value sequences PD1 from the master station to the N-1 slave stations, the master station receives the spread spectrum modulation signals of the N-1 slave stations to obtain pseudo range measurement value sequences PD2 from the N-1 slave stations to the master station, and the time difference sequence between the N-1 slave stations and the master station is PD (PD1-PD 2)/2;

the N-1 secondary stations adjust the time according to the time difference sequence PD.

2. The method of claim 1, further comprising: and repeatedly measuring the time difference sequence PD between the N-1 slave stations and the master station, wherein the N-1 slave stations adjust the time according to the time difference sequence PD.