A GPS C/A Code Tracking Loop Based on Extended Kalman Filter with Multipath Mitigation

Multipath is one of the dominant error sources in the GPS positioning. It is well known that conventional DLL tracking loop in GPS receiver would suffer from performance degradation due to multipath. There are several methods for mitigating the multipath problem. The use of Extended Kalman Filter (EKF) to estimate multipath component and extract the direct signal component is an estimation-based approach for multipath mitigation. In this paper, an EKF based DLL tracking loop is proposed. To estimate the multipath components multiple samples of C/A code autocorrelation function are required and multiple correlators are used to provide them. The I and Q correlator accumulator outputs are used as measurements for the EKF estimation. The amplitude, delay and phase of the direct and the reflected signal components are estimated by the EKF.