Combined phase-frequency tracking in GNSS receivers

Signal processing algorithms in GNSS receivers are actively developing. Modern GNSS receivers are capable to work both in a coherent mode, i.e. with the phase estimation, and in a noncoherent mode, i.e. without the phase estimation. Algorithms for these modes are different, and also GNSS receiver's characteristics are different in these modes. Coherent mode provides more accurate estimates of the parameters of the navigation signal. On the other hand , noncoherent mode under adverse conditions provides a greater noise immunity and sensitivity of a GNSS receiver. Thus, the modern GNSS receiver should be able to operate in both modes. The combined frequency-phase lock loop-s algorithm is proposed in this article. This algorithm allows to obtain advantages of both modes, which were mentioned above. A novel discriminator of phase was synthesized. Results of a simulation and a prototyping are presented.