System to Compare and Evaluate the Quality of Precise Frequency and Timing Systems; Conference paper

摘要

Larger scientific and commercial sites like military test ranges or satellite ground stations very often use several sets of independently operating PTFS (Precise Timing & Frequency Systems). Very often these systems are separated by several hundreds of meters and synchronized to different sources that make it difficult to compare the quality in terms of on-time accuracy and frequency precision between these independent systems. This paper describes a 'tool' to measure and evaluate up to eight independently operating PTFS by measuring the differences between the 1pps-signals and the phase relations of frequencies. This 'tool' is designed for a satellite ground station with six independent PTFS, most of them based on GPS receivers using UTC as time scale. The PTFS are located on a campus; the distance between the systems is up to several hundred meters. The frequency pan of the 'tool' continuously measures the phase difference between the multiple frequencies of the external PTFS, which must not necessarily be of the same nominal frequency and outputs the data to a PC. The accuracy of the measurement is about 10 to 50 ps. The timing part of the system compares the difference between 1 pps signals with an accuracy of 100ps and also outputs the data to the same PC. This unit has some more functions - distribute the information to external sites for monitoring and alarm functions as well as act as an NTP-server. The data derived from the system can be used as well for immediate control, as well for long-term evaluation of the behavior of each independent PTFS.