Enhancing Vector Tracking Accuracy of GPS in Weak Signal Condition Based on Adaptive Strong Tracking Kalman Filter​

"In this paper, a new method for vector tracking of GPS satellite signals in weak signal circumstances is presented. Extended Kalman Filter (EKF) is usually used in vector tracking. As divergence is one of the main problems in common Kalman filters, Adaptive Kalman filters are used to avoid divergence. Common adaptive Kalman filter in vector tracking is implemented using a window with limited length, which cannot be greater than a specified amount and so after a short while Kalman filter will become divergent again. Window length is specified empirically and in accordance to statistical characteristics which may lead to an ideal solution for one specific amount, but not the other. Therefore adaptive Strong Tracking Kalman Filter (STKF) is used in this paper. Simulation results show that adaptive STKF has high accuracy in relation to adaptive EKF, and in case of correctly arranged STKF parameters computing complexity of the proposed vector tracking will be less than the traditional method. Results show that in comparison to traditional vector tracking ,methods based on adaptive STKF have significantly reduced errors in measuring carrier frequency, position and of course velocity.