Reaserch Of Shallow Underwater Acoustic Positioning Key Issues Based On Fractional Fourier Transform

Sound is the only carrier ever discovered that through which information can propagate long distance in the sea. Compared to other forms of communication, sound signal’s attenuation is minimum. So the main means of underwater communication technology mostly depend on underwater acoustic communication. In recent years, with the development of underwater acoustic communication and human exploration of the ocean, underwater acoustic positioning technology plays an important role both in military and civilian activities. Therefore, the study of underwater acoustic positioning technology node has great practical significance.Currently acoustic positioning system positioning more commonly use hyperbolic positioning system, and through the cross-correlation estimate the time delay. However, a plurality of beacon signals may be need to sent for self-positioning of the target. The target receives the plurality of beacon signals and processes the signal to find the solution, in which case the cross-correlation signal delay estimation method will identify the presence of vague and arrival time of conflict. This thesis based on this background and on the basis of laboratory acoustic positioning system transceiver platform, introduces some new processing technologies. In order to overcome the lack of cross-correlation time delay estimation, this paper uses chirp signal’s gathered characteristics on fractional Fourier transform domain. The paper introduces automatic gain control, automatic tracking and threshold quick sliding correlation method to make the detection of chirp signal more effectively. This article focuses on these key technology research and implementation.In this thesis, the chirp signal is used as the positioning signal, and the key technologies of positioning are studied in detail. The destination node use TDOA method to complete the self-positioning based on the delay difference of positioning signals transmitted by a plurality of beacons.In this paper, we analyze the problem encountered in the traditional hyperbolic positioning method based on inter-related delay estimation, and propose the corresponding solutions to the problem. The solution has some significance and application prospects for subsequent underwater acoustic positioning research.