WBMod assisted PLL GPS software receiver for mitigating scintillation affect in high latitude region

Abstract

Ionospheric scintillation occurs for transionospheric radio waves propagating through random ionospheric irregularities, which affect the phase and/or amplitude observations made by the receiver. Generally, the scintillation induces excess carrier phase jitter in the phase lock loop (PLL) of the GPS receiver, and strong scintillation can cause a conventional PLL (ATAN [arctangent method], constant bandwidth Bn = 10 Hz) to lose phase lock resulting in no GNSS signal available at that time from the satellite path(s) affected. A PLL with a larger bandwidth is one solution to mitigate this but at the expense of extra phase noise, and this may not be an optimal solution during weak scintillation conditions. This study uses a novel WBMod (Wide Band Modeling) assisted PLL for robustness of availability of GPS services with lower introduction of extra phase noise. At the initial stage, an optimal PLL bandwidth is predicted using WBMod to stabilize the PLL during strong phase scintillation. A FAB (Fast Adaptive Bandwidth) PLL is used to minimize the phase error. To investigate this approach, a realistic scintillated signal is produced using 50 Hz raw GPS signal observations (carrier phase and intensity) collected at Yellowknife (Yell, 64.48° N, -114.52° E) in a Matlab-based GPS software receiver.