GNSS Single Station Timing Technology And Accuracy Analysis

GNSS can not only provide navigation and positioning services,but also provide highprecision time synchronization and satellite timing services.Single-station timing through the GNSS system has the advantages of wide coverage and high accuracy.It is convenient to realize the positioning timing of the local receiver.This paper focuses on the related research of GNSS single-station timing technology,and analyzes the factors that affect the timing accuracy.The article introduces the relevant theoretical basis of timing technology and explains the factors that cause timing errors;Based on the overall design scheme of the single-station time service terminal,a six-layer time service hardware board is designed,and the hardware design is introduced in detail;On the basis of ensuring the hardware design is stable and reliable,the relevant software and algorithms used by the time service terminal are mainly introduced,including the design of FPGA digital phase detection unit,improves the accuracy of measurement by adopting coarse measurement and fine measurement,and is completely implemented inside FPGA;The Kalman filter algorithm filters the time interval data obtained by FPGA digital phase detection,mainly to filter out the jitter of the PPS(Pulse Per Second)signal output by the positioning chip;Also converting the clock difference data and time interval data solved by the ARM into PID adjustment values,and through the PID adjustment algorithm to adjust the miniature rubidium clock to form a closed-loop negative feedback system.In the design of the time service terminal,combined with the actual situation,a method of mutual reference correction is proposed to give full play to the characteristics of the local miniature rubidium clock output frequency signal with high accuracy and stability,and improve the accuracy of the time service terminal output PPS signal;On the basis of completing synchronous timing,a scheme of time keeping design is added,which aims to design a set of timing terminals that integrates timing and time keeping.After building the overall design framework,relevant test experiments were done on the designed time service terminal,and the test equipment and test methods used were given.After verification,the accuracy of the timing output signal relative to the corrected local reference frequency source is within ± 15 ns.Finally,based on the test results,the possible factors that affect the timing accuracy are analyzed,and related solutions are given.