Research On The Weak Signal Detection Of Underwater Acoustic Signals Based On Chaos And Its Data Transmission

China’s status in the international area is climbing. The promoting in both politics and economy can bring provocation from the hegemon countries. The key measure to deal with this problem is to defend the territory of motherland. Because of the vast but not be opened completely space, the ocean is bound to become the battle field. For our country, the first task is to detect the enemy fleet and prevent the attack. Therefore, one of the important issues is the detection of weak signal in the ocean and its data transmission. Aiming at weak signal detection in underwater acoustic communication, chaos which is more potential with the sensitivity to weak signals and the immune to noise in the field of weak signal detection is chosen. Aiming at the problem of data transmission and communication, this paper studies the way of BDS communication.First of all, the paper takes the traditional Duffing system as the research object, and study the chaotic characteristic and the dynamic characteristics, then find out the threshold point from chaos state to periodic state of Duffing system. Simulation of the Duffing system has been made to study the characteristics of weak signal detection, low signal to noise ratio characteristics, different envelope signal detection characteristics and the strong pulse suppression characteristics. As well, Multisim circuit simulation has been done to confirme the ability of weak signal detection in Duffing system, and its signal to noise ratio can be-80 db. In the end, some problems in Duffing system such as the system’s non-convergence of the periodic state and the narrow detection domain is raised up. These problems limit the application of the Duffing system in practical engineering.Secondly, aiming at solving the the system’s non-convergence of the periodic state and the narrow detection domain in the traditional Duffing systems, two improved schemes are proposed. The first scheme is to improve the model of the Liu system by using the non resonant parameter perturbation method. The threshold point is found out according to the average value method. Some simulation is done to study the characteristics of weak signal detection and signal to noise ratio characteristics. It can be proved that the improved system can be used in weak signal detection and the signal to noise ratio can be-44.77 d B. But this method is not stable and the circuit design is complex. The second scheme is to improve the model of Liu system by using the periodic signal perturbation method and get the similar Liu system at last. The chaotic characteristic and the dynamic characteristics are studied. Simulation of the similar Liu system has been made to study the characteristics of weak signal detection, low signal to noise ratio characteristics, different envelope signal detection characteristics and the strong pulse suppression characteristics. As well, Multisim circuit simulation has been done. The results show that the similar Liu system can solve the two problems of the period convergence and narrow detection domain by using the traditional Duffing system, and the signal to noise ratio is low to-70 d B.Lastly, aiming at the problem that there is no traditional wireless signal coverage in the marine environment, data transmission by the short message communication in BDS is proposed in the paper. Detailed analyses are made to study the communication principle and protocol in BDS short message. Finally, the data transmission and communication of weak signal detection based on BDS short message is realized by debugging the actual equipment.