Integration of vector tracking loop and multipath mitigation technique and its assessment

Multipath mitigation techniques based on code discriminator design are well-known for their capability of reducing multipath effects. However, it also suffers from loss of receiver sensitivity. In order to maintain the multipath mitigation capability and avoid the loss of sensitivity, this paper proposes a novel integration scheme for the discriminator-based multipath mitigation technique and the vector-based tracking loop. In this paper, a Strobe correlator is used as the discriminator-based multipath mitigation algorithm and a vector delay lock loop (VDLL) is used as the vector tracking algorithm. An adaptive tuning algorithm in the form of an Extended Kalman filter (EKF) within the VDLL is developed in this paper as well. An equivalent conventional tracking loop is used as a baseline to evaluate the performance of the proposed integration scheme. In addition, real intermediate frequency (IF) signals are used to verify the positioning improvement of the proposed algorithm. Both static and dynamic signals are identified in the presence of multipath interference. Further, the performance comparison study of the stand-alone conventional tracking (CT) method, the CT with Strobe correlator method, the stand-alone vector tracking (VT) method, and the VT with Strobe correlator method (the proposed combination) is presented in this paper. According to the experiment results, the Strobe correlator further enhances the multipath mitigation ability of the vector tracking in terms of the 3D position solutions as well as the capability of detecting multipath effects. A correlator-based Monte-Carlo simulator is also developed to evaluate the receiver sensitivity. In comparison to the conventional tracking loop, the simulation results show that the proposed integration scheme could achieve a maximum 2.26 dB improvement in terms of tracking threshold probability of 50% with seven satellites in view. In conclusion, the integration of the Strobe correlator with vector tracking not only improves positioning accuracy but also maintains an acceptable tracking threshold.