Kalman Filter-Based GNSS Receiver Structure for Ionospheric Scintillation Mitigation Employing Radial Basis Function Networks

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We propose an adaptive Kalman phase locked loop (PLL) structure for ionospheric scintillation mitigation on global navigation satellite systems (GNSS) receivers, employing radial basis function (RBF) networks to model the scintillation phase and amplitude. The Kalman filter innovations are computed by the arctangent phase discriminator, and the state estimates are directly employed in the carrier replica generation. The nonlinear RBF provide more flexibility to capture nonlinear dynamics evolving with time, possibly present in the scintillation phase and amplitude. The weights of the RBF network and the covariance matrices of the process and measurement noise of the Kalman filter are estimated online, in the adaptive Kalman PLL structure. Simulations with synthetic severe scintillation data show the capability of the proposed Kalman PLL to improve robustness to scintillation effects in carrier synchronization, with performance similar to the corresponding structure employing autoregressive (AR) scintillation model. Simulations with real scintillation data collected by a commercial receiver highlight the learning and generalization capability of the RBF networks to cope with evolving scintillation characteristics over time with possibly nonlinear effects. The Kalman PLL structure employing the RBF network presents reduced state estimation errors when compared to the structure employing the AR model.