Adaptive frequency lock loop system for global navigation satellite systems signals

Formulation of the problem. Classical optimal Bayesian frequency lock loop (FLL) algorithms require a priori knowledge of the frequency dynamics parameters and signal-to-noiz ratios of the received signals. In practice, these parameters vary significantly and, as a rule, are unknown. Taking into account the fact that the operation of such algorithms under conditions different from those a priori specified is not reliable according to the criterion of minimum variance error.

Purpose of the study. Develop a frequency-locked loop system for the Global Navigation Satellite System (GNSS) signal that adapts to frequency dynamics and signal-to-noise ratio to maintain frequency tracking over the widest possible range of operating conditions.

Results. A multi-channel adaptive frequency -locked loop system (MAFLL system) has been developed.

Practical significance. The developed system is capable of processing a jump in the signal-to-noise ratio from 25 to 2 dBHz and back without losing frequency  tracking (under conditions of low dynamics), maintaining frequency tracking during abrupt transitions of dynamics between low (due to the dynamics of the reference oscillator and constant acceleration along the line of sight of 0.04 m/s) and average (due to sinusoidal acceleration with an amplitude of 0.35g and a period of 22.2 s) at a signal-to-noise ratio of 10 dBHz. Thus, in real-world conditions where object dynamics and S/N ratios of received signals change in unpredictable ways, MAFLL system maintains frequency tracking over a much wider range of conditions than non-adaptive FLL.