The Implementation and Comparison Between Kalman Filter-based and Vector Tracking Loops

Abstract

A well-designed tracking loop is the core of a Global Navigation Satellite System (GNSS) receiver and plays a decisive role in estimating parameters and positioning. To solve the problem that classical scalar tracking may fail to track the received signal frequently in high-dynamic and weak signal environments, novel tracking loops based on optimal estimation are proposed by many researchers. Among them, Kalman-based and vector tracking are expected to have a better performance in improving the precision of measurements and positions. Considering their superiority and promising applications in deeply coupled GNSS/ inertial navigation system, the theoretical analysis and practical implementation are worthy of being further explored. In this paper, an EKF-based tracking loop which uses the outputs of coherent channels directly is proposed. And then, the implementation of a vector tracking frequency-locked and delay-locked loop is further proposed in detail. At last, the performance and superiority of the two methods are tested where a software-defined receiver is constructed and the aircraft data from a GNSS constellation simulator is used. Compared with scalar tracking, a significant improvement on positioning and measuring parameters is achieved by the two methods. And the vector tracking indicates a 42.9% and a increase on the precision of positioning and pseudo-range measuring respectively.