Improvement of the Accuracy of PPS Signal

Hiroaki Toyoizumi, Masahiro Genda, Katsuo Yui, Tetsushi Yamada and Yoshiji Hieda

Abstract:	The Pulse Per Second (PPS) signal generated by a GPS receiver is used for the synchronization between separate stations in the communications system or the measurement system. The PPS signal can be observed in excellent relative accuracy because of followings. Firstly, the time difference among GPS satellites which influences the accuracy of PPS signal is controlled on the ground. Secondly, in the short-range synchronization commonly used in the communication-service cell, the same GPS satellites can be observed simultaneously. The above-mentioned utilization of GPS time information enables the accurate relative synchronization; currently the PPS accuracy in the GPS receiver is about 20 nanoseconds, which is not the limit of the accuracy of PPS signal. Practically more accurate PPS signal is required for improving the quality of the synchronous systems, which is important to expand the application into various fields. We developed a precise output circuit as an improvement of hardware, and a calculation algorithm as an improvement of software, for generating more accurate PPS signal. (1) Precise Output Circuit We investigated the accuracy and the error sources in the present PPS signal. A commonplace single frequency GPS receiver contains a temperature-controlled crystal oscillator (TCXO) which oscillates at about 16MHz. In such a receiver, the error of the TCXO-clock resolution is more influential than user range error (URE) which depends on the GPS system and the receiving environment. Therefore, we developed a precise PPS output circuit within 1 nanosecond of precision. (2) Calculation algorithm The deviation in GPS time solution causes the error of the PPS output timing. We developed the algorithm for suppressing these deviations. We have achieved PPS signal such that the relative synchronization error is a few nanoseconds, a tenth of the error of the conventional receiver. We expect that our accurate PPS signal will play an important role for expanding the applications of GPS receivers, such as communication systems by shortening the initial acquisition time, and the measurement systems by improving the sampling accuracy.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	1713 - 1719
Cite this article:	Toyoizumi, Hiroaki, Genda, Masahiro, Yui, Katsuo, Yamada, Tetsushi, Hieda, Yoshiji, "Improvement of the Accuracy of PPS Signal," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 1713-1719.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In