基于FFT的星载AIS信号频偏估计算法

Frequency-Offset Estimation of Satellite-Based AIS Signals Based on FFT

针对星载自动识别系统(Automatic Identification System,AIS)信号中存在较大多普勒频移而造成的信号难以正确检测问题,提出了一种星载AIS信号的频偏估计算法,根据FFT算法寻找谱线峰值位置得到信号的频偏信息,通过改变周期图峰值范围扩大正频偏估计范围,利用接收信号的幅角信息判断频偏符号并对负频偏的估计结果进行校正来。仿真结果表明,改进的算法能够估计的范围达到-4800Hz^4800Hz,且提高了估计的精度,可以应用于星载AIS接收机。

Since satellite - based Automatic Identification System （AIS） signals are difficult to detect which caused by the larger Doppler frequency shift, this paper proposes an algorithm to get satellite - based AIS signals fre- quency information. By changing the scope of periodogram peak position, the algorithm expands the range of positive frequency offset estimation. It uses the angle information of received signals to judge the symbol of frequency value and fixes the estimated result. Simulation results show that the range of improved algorithm can reach -4800Hz - 4800Hz, its accuracy is better than the earlier methods. This estimation algorithm is reasonable for satellite - based AIS receiver.