Research On Chirp FSK Reliable Underwater Acoustic Communication Technology

Shallow water channel was a very complex channel, with complexity, diversity, strong multi-path effects and Doppler frequency shift characteristics. For the features of the channel, Chirp FSK system was established with multi-transmission mode and high transmisison rate in order to achieve robust communication on the condition of low SNR, serious multipath spread, and Doppler frequency shift.Chirp FSK system adopted the main idea of Orthogonal frequency division multiplexing technology and made use of multi-frequency shift keying modulation method overcoming disadvantages sensitive to Doppler frequency shift and phase noise to enhance reliability of the system. Non-coherent energy detection was the key technique of frequency-shift keying modulation, so the system introduced Chirp signal as the carrier signal for its performance with sharp energy peak, easy to detect and judge to reduce the probability of error. The system could overcome effects of multi-path interference and Doppler frequency shift to achieve reliable data communications.In this thesis, first of all, Chirp FSK communication system model was established. Second, the structure of the system was analyzed, then the theory of modulation was studied in detail. At last, key technologies to achieve system were explained simply. Chirp FSK schedule was the key technique of the system,it was the combination of the idea of Orthogonal frequency division multiplexing and multi-frequency shift keying.At the end, the thesis analyzed the nature of the system,results verified the reliability and feasibility of the system.