Robust Receiver Tracking

Description Introduction

Figure 1: Illustration of a scenario where both scintillation and radio frequency interference affect the GNSS signal

 

Global Navigation Satellite Systems (GNSS) signals affected by scintillation may experience rapid variations in their amplitude and phase. This phenomenon can strongly decrease the performance of a GNSS receiver, decreasing the position accuracy and in the worst scenario, also inducing a total loss of lock on the satellite signals. Indeed, if the Doppler shift induced by phase scintillation is larger than the phase lock loop bandwidth, the receiver tracking scheme could not be able to follow the high dynamics induced by scintillation. Furthermore, the deep signal fading produced by scintillation, could push the signal level below the minimum receiver threshold allowed for the signal tracking. To mitigate the scintillation effects at the receiver level, particular attention should be dedicated to the design of the Phase Locked Loop (PLL) which is the receiver link more sensitive to scintillation effects. As illustrated in figure 1, apart from scintillation, other telecom systems transmitting at carrier frequencies close to the GNSS bands may interfere with the satellite signals. When subject to radio frequency interference, GNSS receivers experience a drop in signal power and an increased variance in the signal amplitude that could potentially affect the computation of scintillation indices. Consequently, in order to ensure a reliable scintillation monitoring, radio frequency interference mitigation techniques should be activated.