A novel method of synchronising two atomic clocks

Abstract

In this paper we present a novel method of atomic clock synchronisation combining digital error correction and phase tracking. Microwave broadcasts are used to measure the difference in frequency between a pair of atomic clocks. We use the fact that desynchronised atomic clocks give rise to a phase error in a QPSK broadcast, which can be measured with high precision. The rate of change of this phase error is used to find the relative error in frequency of reference signals provided by two clocks, with an uncertainty in the region of 1e-15 Hz over a measurement time of 10 minutes. We find that the base stability that can be measured with this technique is 2.66e-17 Hz, making it potentially applicable to applications like measuring geodetic height to the centimeter level.