An Improved Time Synchronous System Based on GPS Disciplined Rubidium

In this paper, an improved time synchronous system based on Global Positioning System (GPS) disciplined Rubidium frequency standard is introduced. By comparing with the Cesium frequency standard´s output, the difference between the two signals has been measured, the character of the GPS timing signal is analyzed, it is proved that the GPS timing signal has a zero mean value over the long haul and the accuracy may be enhanced by making many measurements and averaging them. A scheme of GPS disciplined Rubidium based on Time to Digital Converter (TDC), numeric data filtering, embedded computer and precisely Digital to Analogy Converter is designed, the accuracy of the GPS disciplined Rubidium frequency standard is about 3 × 10^-12. Based on the same, a novel method of time Synchronous using GPS timing signal is invented. Not as the normal method-directly using any one of the GPS timing signal to synchronous, the improved time synchronous system´s output is synchronous to the GPS timing signal´s mean, though it has a lower noisy level and a good accuracy. The precisely time synchronous circuit based on an embedded computer, Complicated Programmable Logical Device (CPLD), Time to Digital Converter (TDC) is described, and the test result results are presented too.