Design of a Differential Vector Phase Locked Loop for Single Frequency RTK Receivers

Continuous tracking of carrier-phase signals is an important requirement for real-time kinematic (RTK) positioning under dynamic conditions. With the mass-market adaption of carrier-phase differential GNSS technology, there is a strong incentive to use single-frequency commercial receivers. For such receivers, a vector tracking based receiver architecture is a potential candidate for RTK due to improved performance under lower carrier-to-noise power density ratios and higher dynamics as compared to conventional scalar receivers. The performance of vector tracking loops can be further improved for differential positioning, if differential carrier-phase measurements are directly used in the tracking loop of rover receiver. This study presents the design of a vector phase locked loop using single difference carrier-phase measurements directly in the tracking loop for a single frequency dynamic rover. With careful system design and cycle slip detection and correction strategy, phase lock can be maintained providing a precise solution.