Hybrid differential coherent bit synchronization algorithm for the weak GNSS signal

The low signal-to-carrier ratio and frequency deviation affect the bit synchronization in the GNSS receiver. In this paper, a hybrid differential coherent bit synchronization algorithm is presented, which uses the short coherent time to improve the signal gain and adopts the large distance differential coherent method to enhance the discrimination between bit edge and others. The results show that the proposed algorithm maintains a good frequency deviation tolerance, and achieves good synchronization performance under 50Hz frequency deviation. Compared with previous methods, the proposed algorithm improves the sensitivity of bit synchronization by 3～7dB.