Study of mean time to lose lock and lock detector threshold in GPS carrier tracking loops

Narrow-Band power detector was applied to indicate the lock status in tracking loops of GPS receiver. Previous researches did not discover the statistical characteristics and mean time to lose lock of detector, thus the threshold selection did not have theoretical support. In this paper, the probability distribution of detector is derived theoretically by stochastic method, and the relationship between the lock probability and carrier to noise (C/Nq) of the signal is discovered. Furthermore, the paper analyzes the Mean time to lose lock (MTLL) related to threshold setting and C/No of signal, providing a theoretical basis for threshold setting method of GPS tracking loops. At last, the simulations and real data test have been made to prove the results.