NTSC Researches Made Important Progress on Time-keeping Theory and Method

Recently, Metrologia, a leading international journal in the field of time frequency, published the academic paper- Detecting an atomic clock frequency anomaly using an adaptive Kalman filter algorithm co-authored by Mr. Song Huijie, Dong Shaowu and other members of the Key Laboratory of Time-frequency Standard of National Time Service Center (NTSC), Chinese Academy of Science (CAS). The paper is significant for keeping China’s time reference. It marks that NTSC researches on time-keeping theory and method have gained international recognition.

The paper introduces how to detect an atomic clock frequency anomalyby using an adaptive Kalmanfilteralgorithm, improving on the traditional mathematic model algorithm. Frequency anomaly mainly includes frequency hopping and frequency drift variation. Obvious frequency anomalies can be easily detected by traditional measurement like allan variance and power spectral density, but it is difficult to detect tiny anomalies using these methods. Thus, based on the analysis of stimulated clock data and the atomic clock data from the UTC（NTSC）time reference system, it finds that compared with the classical Kalman filter algorithm, adaptive Kalman filter algorithm has higher probability of detecting frequency anomalies and it takes shorter time in detection, making a very promising method in maintaining time reference.

In recent years, NTSC has been contributing to improving the performance of the national standard time, developing methods to evaluate atomic clock performance, carrying out innovative researches on integrated multi-links GNSS time transfer methods and applications of reference clocks to time-keeping systems. Breakthroughs have been made in time-keeping methods and technologies, as well as researches on GNSS time transfer.