General Design Method for Two-dimensional Multi-correlator Anti-multipath Tracking Loop for BOC Signals

Abstract

As binary offset carrier (BOC) signals are widely used in global navigation satellite system (GNSS), tracking ambiguity threats and multipath become two main factors which affect ranging precision. Two-dimensional (2-D) tracking loops, such as double estimate tracking (DET) and double phase estimator (DPE), estimate the code delay and subcarrier delay by the delay locked loop (DLL) and the subcarrier locked loop (SLL), respectively, to obtain high precision and unambiguous propagation delay. Although 2-D tracking techniques can effectively alleviate the impact of tracking ambiguity threats, their anti-multipath performance has not been improved compared with one-dimension (1-D) tracking techniques. This paper proposes a general design method for two-dimensional multi-correlator anti-multipath tracking (TMAT) structures based on heuristic optimization. Compared with 2-D tracking loops equipped with traditional anti-multipath structures, such as narrow early minus late (NEML) and double delta (DD) structures, TMAT structures designed for different signals with different bandwidths always have better multipath mitigation performance without any degradation of tracking robustness. According to case studies, because of the great anti-multipath improvement of TMAT structures, the slight degradation in thermal noise performance can be acceptable. Also, the designed TMAT structures are insensitive to relative amplitude of multipath and bandwidth of signals, indicating the great practicality of this technique.