碩士 / 國立中山大學 / 機械工程學系 / 87 / In shallow water, the primary limitation of the performance for active sonar is the reverberation that originates from volume and boundaries scattering and the multi-path propagation. Echoes of the target are shadowed by the signals of the reverberation; thus the undesired signal decreases the ability of active sonar for target detection. Therefore, the study of the reverberation cancellation is very important on a active sonar system. In this research, the author has built the models of the reverberation simulated with MATLAB package to study the characteristics of the reverberation. Notably that the simulated frequency range is between 20-kHz and 30-kHz in the research. The main aims of the work are then to create the signals that include the reverberation and the target and then perform the reverberation cancellation of the active sonar in shallow water. The analysis of the reverberation and the target are based on the propagation theory of image source, surface scattering of Rayleigh criterion of roughness, bottom scattering of Lambert’s Law, and multi-path scattering. The result is then compressed or enhanced by basic signal compression, TVG and AGC. At the ends, the echo of the target is distinguished by the methods of post-detector and wavelet transform. The following findings have emerged: a) the basic signal compression can compress the signal in a specific dynamics range, and can reduce the misunderstanding rate that is caused by the traveling distance and the time. b) The wavelet transform can be used to locate and distinguish the echoes of the target in a reverberation-dominated environment.
| Identifer | oai:union.ndltd.org:TW/087NSYSU489047 |
| Date | January 1999 |
| Creators | Yea-Ray Chen, 陳奕瑞 |
| Contributors | Shiuh-Kuang Yang, 楊旭光 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 132 |
Page generated in 0.5011 seconds