Research on the demodulation of the underwater acoustic differential frequency-hopping signals based on adaptive notch filter

The differential frequency-hopping technology is imported into the underwater communication research domain in this paper, according to the requirement of underwater target´s secure communication and safety reliability. By analyzing algorithms of G function and multi-path of received differential frequency-hopping signals, a method of demodulation based on the combination between parallel connection notch filter energy detector and Viterbi algorithm is derived. The performance of the method is validated by the results of the simulation and the lake trial. It is shown that the application of differential frequency-hopping used in the underwater acoustic communication can overcome the multi-path interferences effectively and have a good BER performance under low SNR, so it is suitable for underwater acoustic secure communications.