Dual update-rate carrier tracking technique for new generation global navigation satellite system signals in dynamic environments

Abstract

With the upcoming of modernised global positioning system (GPS) and Galileo, the new generation global navigation satellite systems (GNSSs) will be able to provide the users a better positioning performance. An important modification on most of the new generation GNSS signal structures is the availability of the pilot channel, which stands for an additional measurement obtained; moreover, a pure phase-locked loop (PLL) can be used in carrier-phase tracking loop. Utilising this characteristic, the authors present a dual update-rate PLL for modernised GNSS signals to deal with the well-known dilemma that the usage of long coherent integral time can help in reducing the noise from thermal effects, whereas the usage of short coherent integral time can permit the tracking loop to suffer more dynamics stress. By processing data and pilot channels with different coherent integral times, different discriminators, and then performing the fusion of those two different update-rate measurements in a Kalman-filter-based loop filter, this loop offers several advantages over the traditional methods in dynamic and low carrier-to-noise ratio (CNR) environments. Simulation results demonstrate that the proposed dual update-rate PLL shows good performance in both dynamic and low CNR environments.