Approach for Setting the Optimal Parameters of Vector Frequency-Locked Loop-Assisted Phase-Locked Loop in GNSS Receivers

Abstract

High-precision positioning of global navigation satellite systems (GNSSs) is crucial for various Internet of Things (IoT) applications, including intelligent transportation and smart manufacturing. GNSS carrier phase measurements can provide high-accuracy measurements, enhancing positioning performance. Unfortunately, the accuracy of scalar-tracking loop carrier phase measurements significantly deteriorates in complex environments. This decline arises partly from the underutilization of received information by scalar-tracking loops. The hybrid vector-scalar architecture combines the robustness of carrier frequency tracking with the accuracy of the scalar phase-locked loop (PLL), making it an excellent carrier-tracking method. However, the capricious nature of the rule-of-thumb parameter settings and the associated complexity limit the full exploitation of the structural advantages. Therefore, we first establish a mathematical model for error propagation in the vector frequency-locked loop-assisted PLL (VFLL-assisted PLL) and derive an analytical expression for the phase error. Then, an optimal parameter setting approach based on the minimum error criterion is proposed. Finally, the carrier-tracking performance of the VFLL-assisted PLL with the optimal parameter design approach is evaluated. The assessment and evaluation are conducted via experiments with simulated and real data. The results indicate that the optimal parameter design approach improves the carrier-tracking performance of the VFLL-assisted PLL, which is more sensitive and dynamic than the FLL-assisted PLL.