A Carrier Tracking Algorithm Based on Adaptive Unscented Kalman Filter Under Ionosphere Scintillation Conditions

Abstract

The rapid change in the phase and amplitude of GNSS signals can cause the strong nonlinearity of carrier tracking under scintillation conditions. Moreover, the noise caused by ionospheric scintillation is non-Gaussian, resulting in difficult determination of the covariance of measurement noise. These would degrade the accuracy and robustness of conventional phase lock loop and extended Kalman filter (EKF)-based carrier tracking algorithms. This work proposes an adaptive unscented Kalman filter (UKF)-based carrier tracking algorithm to mitigate the adverse impacts of ionospheric scintillation. For one thing, the unscented transformation can effectively mitigate the linearization error of strong nonlinear cause by ionospheric scintillation, For another, we employ the phase lock indicator (PLI) to estimate the covariance of the measurement noise adaptively according to different scintillation scenarios. Through the adaptive UKF-based algorithm, the performance of carrier tracking under ionospheric scintillation can be improved, and the probability of divergence can be decreased. Simulation results demonstrate the validity of the analysis and the proposed method.