Ionospheric scintillations are created by diffraction when the transmitted propagating waves encounter a medium made of irregular structures with variable refraction indexes. The recombination of the waves after propagation can be constructive or destructive and the resulting signal at output of the receiver antenna may present rapid variations of phase and amplitude. The carrier phase is traditionally tracked in the GNSS receivers using PLL, potentially aided by FLL. Phase Loops are known to be less robust than code tracking loops, and the GNSS receivers may thus suffer from phase tracking loss. This strongly impacts the positioning service availability, as well as the capability to demodulate the navigation message data, in situations where ionospheric scintillations affect the received signal. One thus has to implement innovative techniques and receiver architectures to provide robust carrier phase tracking. The aim of this paper is therefore to present the development of a GPS L1 phase tracking technique based on a Kalman Filter PLL [10] improving the tracking robustness in presence of ionospheric scintillations, and to present results of its performance using simulations. This paper is related to the paper presented at ION GNSS 2012 by C. Macabiau [1].