Frequency tracking loop with wide pull-in range for weak DSSS signal

A frequency tracking loop based on triangle function frequency discriminator and adaptive loop bandwidth adjustment is proposed to track the Doppler frequency of weak direct-sequence spread spectrum (DSSS) signal. The proposed structure first provides a frequency discrimination with wide pull-in range to lock the large residual frequency offset after acquisition. Then, the adaptive loop bandwidth adjustment is employed to improve the accuracy of frequency estimation. Compared with the conventional tracking loop, the proposed structure has wider pull-in range and higher sensitivity. Simulation results verify the validity of the proposed method.