EKF based Vector Delay Lock Loop algorithm for GPS signal tracking

This paper analyzes a system model for Vector Delay Lock Loop (VDLL) algorithm based on Extended Kalman Filtering (EKF) for GPS signal tracking. In the VDLL, all the code tracking loops are closed by the navigation solutions estimated by EKF, and the tracking performance is more robust than that of the traditional scalar delay lock loop (SDLL). Firstly, we illustrate the essential difference between SDLL and VDLL. Secondly, aiming at the condition in which the code phase spacing between the early and the late replica code is not 1 chip exactly, we establish the non-linear system model for VDLL, and give the equation between the system measurement and the estimated error of transmission delay. Moreover, we derive the equation for the measurement noise variance. Then, this paper linearizes the non-linear model, and gives the multi-satellite VDLL algorithm using EKF. Lastly, the effectiveness of the model is validated by simulation.