Two-way Time Synchronization For Foundation Pseudolites Technology Research

Foundation pseudo satellite navigation enhance system is an important part of navigation and positioning system, effectively supplement the deficiency of the satellite navigation system. Foundation pseudo satellite navigation enhance system is the essence of a time synchronization system,the accuracy of the system time is the foundation of high precision timing, positioning. Two-way time and frequency transfer (TWTFT) is currently one of the highest precision of long time synchronization technology, its system advantage lies in the use of the symmetry of two-way link to eliminate common-mode error in the process of bidirectional transmission signal. Paper based on this background, the application of two-way time frequency transmission technology to enhance the system how to realize the foundation pseudo satellite navigation time synchronization.This article main research content and the work is as follows:First of all, the thesis compares the time-frequency transmission methods, including one-way time synchronization method and GPS method, three kinds of two-way time synchronization method. Pseudolite system under the environment of foundation with two-way time synchronization process carried on the thorough theoretical analysis, and gives the foundation pseudo satellite two-way time synchronization error model. Near the ground,the clock feature is one of the key factors influencing the time synchronization performance,the paper deeply analyzes the cock drift impact on the foundation of pseudolite time synchronization mechanism, and gives a reasonable effective clock frequency calibration scheme.Second,the thesis analyses the key technology in the process of implementation,including tracking capture, modeling precision and clock. Capture tracking is the basis of reception, the performance of the tracking loop directly related to the accuracy of time synchronization. Distance measuring method in this paper using carrier phase smoothing pseudorange, it combined with carrier phase measurements and the advantages of both the pseudo code ranging is a kind of high precision,complexity,low range estimates. In view of the range that may occur during the process of pseudo according to burst error and carrier phase cycle slip is given a more robust carrier phase smoothing pseudorange algorithm. Paper using kalman filtering algorithm for clock difference data modeling, and the clock difference,frequency difference, aging rate three state parameter estimates, after filtering more smooth state parameters are obtained. Papers of the above technical problems are analyzed through Matlab simulation validation.Finally, the paper gives the overall architecture of the system and key modules of the FPGA design. And conducted a large number of field, the test results show that the basic foundation of pseudolite system time synchronization error keep within five nanoseconds,achieve the expected technical indicators, meet the demand of the foundation of pseudolite system design.