Carrier Tracking Loop Based on Two-Stage Phase Compensation Under Highly Dynamic and Low-SNR Environments

Wireless communication systems are subject to significant and time-varying Doppler frequency offsets (DFO), especially in highly dynamic environments where the DFO is larger than the symbol rate. Even after coarse DFO compensation, substantial residual frequency offset (RFO) remains. Under low signal-to-noise ratio (SNR) conditions, data bit-flip events may occur, causing abrupt changes in the tracked RFO and resulting in tracking loop failure and degraded performance. To address this issue, we propose a novel carrier tracking loop based on two-stage phase compensation (CTL-PC<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>). The first phase compensation ensures continuity of the tracked RFO using the output of a two-quadrant arctan phase detector, while the second is activated upon detection of bit-flip events. Simulation results show that the proposed CTL-PC<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> offers improved tracking accuracy and dynamic range compared to conventional phaselocked loop (PLL), frequency-locked loop-assisted PLL and CTLs based on bandwidth adjustment methods in highly dynamic and low-SNR environments.