Precise 1PPS signal by GPS
GPS is widely used to obtain not only the position information but also the time information. Specially, it is used to synchronize the time between separate stations in the measurement system or the communications system. However, in these systems, the output circuit of the 1PPS signal in the GPS receiver has not been optimized. In this paper, we examine the error sources of the time measurement by GPS and show the time measurement accuracy is about 10 ns, and the improvement of the precision of 1PPS signal is most important to realize high accurate 1PPS signal. We propose the precise 1PPS generating method by the analog circuit whose output precision is sufficiently higher than the time measurement accuracy by GPS. We evaluated the time measurement accuracy and the accuracy of 1PPS signal in the relative time synchronization by 24 hours test, and succeeded to realize a few ns precision and several ns accuracy of 1PPS signal in the relative time synchronization using our precise 1PPS generating method.