Synchronous demodulation algorithm based on energy operator for satellite-based AIS signals

A synchronous demodulation algorithm based on energy operator for satellite-based AIS signals is proposed. Firstly, the baseband signal is obtained by differencing the intermediate frequency signal and estimating the envelope with energy operator. Bit synchronization and decision are achieved by applying the maximum measurement method which selects the best set of samples with the maximum energy. Simulation results show that when the SNR is low or there are interfering signals, the BER of the proposed method is obviously lower than non-coherent ones. The proposed method maintains almost the same efficiency as the incoherent demodulation and is significant for practical application.