A Large Range Carrier Frequency Offset Estimation Algorithm for APSK Signals

In satellite communication, the high-speed moving source will cause a large frequency offset when the transmission signal arrives at the receiver, and the existence of frequency offset will seriously interfere with the demodulation of the signal, making the receiver unable to obtain the information it carries from the transmission signal. In this paper, the influence of frequency offset and phase offset on modulation signal and constellation is analyzed. In order to eliminate the frequency offset in the process of signal transmission, a carrier frequency offset estimation algorithm for APSK modulated signals is proposed. By setting one or more decision thresholds, the algorithm enlarges the signal points on the inner ring to the outermost ring in equal proportion, and thus realizes the data combination of the signal points on the APSK signal constellation, and then removes the modulation information. Finally, the FFT operation is used to extract the peak value of the signal points, and the estimated value of the carrier frequency offset can be obtained. Through simulation experiments, this algorithm has low complexity, short running time, high accuracy of estimation results, and has a large range of frequency offset estimation compared with kay algorithm, Fitz algorithm, M&M algorithm, L&R algorithm, etc., which is more suitable for satellite communication and other applications with significant Doppler effect.