25-10-2012, 04:41 PM
A Kalman Filter Clock Algorithm for Use in the Presence of Flicker Frequency Modulation Noise
ABSTRACT
NPL has developed a Kalman-filter-based clock algorithm for combining measurements from its three active hydrogen
masers. The algorithm is designed to produce a near optimal composite when the dominant noise process present is flicker
frequency modulation (FFM). The FFM is modelled approximately by a linear combination of Markov noise processes. Each
Markov process is included in the Kalman filter and contributes an additional component to its state vector. Both the validity
of the model and the effectiveness of adding these additional components to the state vector are examined. The performance
of the new algorithm is examined when applied to simulated measurements and also to measurements obtained from NPL’s
hydrogen masers.