THE ALGORITHM OF WEAK SIGNAL TRACKING BASED ON SLIDING FREQUENCY LOCK LOOP

In some special environments, such as indoor environment, GNSS signal is greatly attenuated when reaching the receiver, so some high-sensitivity tracking technologies must be adopted. The existing high-sensitivity tracking algorithms have a large amount of computation, high complexity and take up more resources. Therefore, a low-complexity weak signal tracking algorithm based on sliding frequency lock loop has been proposed in this paper. For the GPS L1C/A signal, the sliding coherent integration of the data within one data bit (20ms) can increase the pull-in range of the frequency discriminator without changing the current loop structure, so as to lower the tracking threshold of the frequency lock loop and improve the tracking sensitivity of the receiver. The simulation is carried out for the data with the carrier-to-noise ratio of 15dB-40dB, the doppler frequency of 0Hz and 30Hz, and the data with an initial doppler frequency of 30Hz and an acceleration of 0.4g/s. Experimental results indicate that the proposed algorithm can stably track signal with the carrier-to-noise ratio of 16dB (-158dBmW).