Improvement of the Carrier Phase Based on Vector Frequency Locked Loop with the Phase Locked Loop Assisted

Vector frequency locked loop (VFLL) uses the information which is the velocity and the clock drift from the receiver and satellites to predict the carrier frequency in each channel. However, VFLL is not precise enough to lock the carrier phase, which does not demodulate the received signal correctly. To address this problem, this paper presents a method based on the vector frequency locked loop with the Phase Locked Loop (PLL) assisted. Firstly, the proposed method adds the output of the loop filter of the carrier phase discriminator to the prediction of the carrier frequency, which enhances the precision of the carrier phase of VFLL. Then, by means of compensating the residual of the carrier phase, the accuracy of demodulation value is improved. Simulation results of simulated data test and real data test demonstrate that the performance of the proposed method outperforms the VFLL in term of the carrier phase and demodulation value.