Application of Diversity Techniques and Signal Processing to Acoustic Far Field Imaging of Underwater Object

• Main Authors: Jyun-Gu Ou, 歐俊谷
• Other Authors: Kun-Chou Lee
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/64358108770779391776

碩士 === 國立成功大學 === 系統及船舶機電工程學系碩博士班 === 96 === The main purpose of this thesis is to establish the theorem and measured system of underwater acoustic imaging. We obtain scattering values of the metal cylinder by utilizing the monostatic system. It means transducer transmits an acoustic wave to illuminate the metal cylinder and receives scattering values of metal cylinder in the far field. Then, we acquired more scattering data by utilizing diversity techniques. Diversity techniques can be divided into angular diversity and frequency diversity. Finally, we put scatter data in Fourier space by bi-linear interpolation and two-dimensional inverse Fourier transformation and then we can get the image reconstruction. In the theorem, we simulate image reconstruction of cylinder of different materials and radius, and using multi-frequency diversity and multi-angular diversity to obtain more scattering value. We analyze the simulated result that the multi-frequency diversity technique influences the resolution of object imaging, and the multi-angular diversity technique influences the contour of object imaging. In the experiment, we process the image reconstruction on the iron cylinder whose radius and high are 10 cm and 40 cm to prove the accuracy of imaging theory. In addition, we illustrate the method of calibration. The experimental result of our image reconstruction was as expected. This shows potential values for diversity techniques to be applied in exploring underwater resources, researching shipwrecks, and testing non-destructively.