Study On The Application Of Time And Frequency Transfer With GPS Common-view

With the development of science and technology, time and frequency is playing an important role in many field. The national defense and the space technology have put forward the demand with more higher precision on time and frequency synchronization. The time synchronization with nanosecond level is required in Synchronous Digital Hierarchy (SDH) communication network and heading off to the objection in space. At present, Chinese have no ability on developing the instrument with the time synchronization precision up to ns level. In addition, the performance of time synchronization in real-time and so on is required in many cases. The method of GPS Common-view is characterized by higher precision, good convenience in use, and cheap instrument, therefore the study on the application of GPS common-view is very important.A new method of design on common-view time transfer system is presented The system is based on Motorola VP Oncore GPS receiver. For the sake of strict common-view, a synchronized control strategy using multi-thread mechanism and an auto-detecting block are designed. The raw data with zero-baseline single-channel common-view measurement shows that the Root-Mean-Square is better than 4.9ns in case that the distance between two antenna is about 0.3m but the coordinates is set to the same.GPS common-view time transfer in near real-time may be implemented by processing observation data with high speed and high precision, but normal smoothing and filtering method is not satisfied with near real-time case. Based on the datum from GPS common-view, a Kalman filtering algorithm is presented, and the clock difference at remote different places can be obtained. The reductions of the common-view data from Communications Research Laboratory(CRL) and the Korea Research Institute of Standards and Science(KRIS), which locate at a distance of about 1000km show that the root mean square of time difference obtained by Kalman filter, and one from Circular T is better than 2.6ns. Furthermore, when GPS CV in near real-time is applied in multi-sites, in order to improve precision, a technique of indirect observation adjustment after Kalman filtering algorithm is presented, in which the observation weight is set according to the distance between two sites. With reference to the clock difference from Circular T of BIPM, a comparison between data before and after adjustment shows that common-view in near real-time is more accurate after adjustment. Considering the very small difference of clock difference after Kalman filtering in continues time with interval equal to 16 minutes, we may forecast the clock difference in next time in series by extrapolateing according to that in present, and high precision may also be obtained.The main error source in GPS Common-view is analyzed, and the multi-path effect is put emphasis upon.The application of GPS disciplined Rb in telecommunication network is analyzed. Frequency measurement is the basis of frequency disciplined in GPS disciplined Rb clock system. The disadvantage of high precision frequency measurement method available is that an expensive high-resolution time interval counter is needed. A new frequency measurement method is presented. Using a low-resolution circuit card with which the time interval may be measured in indirect method, we may get the time interval between Ipps of GPS receiver and that of LPFRS Rb clock. After that, a Kalman filtering algorithm is developed on single chip computer with smooth of the measurement noise. Based on frequency accuracymeasurement algorithm, LPFRS disciplined Rb system is developed. Measurement data shows that the frequency accuracy is better than 1 × 10-12.The demand of digital synchronization network and its operation network, and the problem of time traceability are analyzed. We can draw a conclusion that the time traceability with GPS common-view has much advantage, such as few chains, high precision, and convenience in using.