Adaptive Phase Lock Loop for GNSS Receiver

Classical Bayesian algorithms for Phase lock loop (PLL) system require a priori knowledge about the parameters of the phase process dynamics and the signal-to-noise ratio (SNR) of the received signals. In practice, these parameters vary over a wide range and rarely are known. As a result, the operation of such algorithms under conditions other than that a priori specified is not optimal. The purpose of this work is to develop an optimal phase tracking system that is adaptive to the dynamics of the phase process and the SNR in order to maintain phase tracking in the widest possible range of operating conditions while tracking global navigation satellite system (GNSS) signal. An adaptive multichannel phase lock loop (AMPLL) system has been synthesized as a result of formulation and solution of signal processing problem in terms of the statistical synthesis theory. The AMPLL system is able to withstand an SNR jump from 50 to 9 dBHz and back without loss of phase tracking in low dynamics conditions (only the drift of the reference quartz oscillator). The AMPLL system is able to withstand abrupt transitions of dynamics between low and high (the sinusoidal acceleration 10g and sinusoidal jerk 10 g/s) without loss of phase tracking under the 24 dBHz signal-to-noise ratio. Thus, in real conditions, when the dynamics of the GNSS receiver and the SNRs of the received signals change in an unpredictable way, the AMPLL system keep tracking in a much wider range of conditions than the non-adaptive PLL.