The switching carrier tracking loop under severe ionospheric scintillation

An enhancement of an existing algorithm to track the GNSS signals in presence of strong scintillation is presented. The Carrier Tracking mechanism employs both a Phase Locked Loop and Frequency Locked Loop and a switching mechanism between the two in order to maintain the signal lock during power fades and phase variations; a new Loss of Lock detection method based on the linearity region of the atan2 PLL discriminator is implemented and a switch back from PLL to the FLL is proposed. The Loss of Lock performances of the new strategy are evaluated and compared to the standard PLL and FLL assisted PLL through MATLAB simulations.