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The Study of the Beam Forming New Technologies for Imaging Sonar

Author: WangXiaoFeng
Tutor: SangEnFang
School: Harbin Engineering University
Course: Signal and Information Processing
Keywords: Sonar Acoustic Image Beamforming Acoustic Lense Array CCD
CLC: U666.7
Type: PhD thesis
Year: 2011
Downloads: 103
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Abstract

The techniques of underwater object detection are very important in either underwater defence or civil ocean industry. Detecting by the imagining sonar is a effective method. With the rapid progress in underwater engineering fields, the need for development of high resolution, real time, precise imaging sonar is more and more urgent. In this paper, besed on recent development of electronic beamforming and lens beamforminng, the author have studied on some key techniques by computer simulations and have implemented two experimental systems. The works include:1. In order to avoid the large amount of hardware caused by the acoustic plane array for 3D multiple beamforming, the bidirectional multiple beam forming imaging sonar have been studied. A designed system achieving 3D imagine have implemented by two acrossing linear arrays, one transmitting array and one receiving array. The works of beamforming software based on parallel algorithms and its implementation on TMS320C6416, Matlab simulation for performance analysis and the system hardware have been done.2. Acoustic lens designing is a key technology on lens imaging sonar. Firstly the paper introduces the design principle of the lens in detail. The principle of acoustic lens imagining is the same as optical one but compared with the optical lens, the aperture of the acoustic lens to signal wavelength ratio is much smaller, so that diffraction can not be ignored. Since the effect of diffraction is based on the scale diffraction.boundary conditions are very cumbersome, so a hybrid model is very realistic. The author reforms the previous hybrid model and make the model more precise and reasonable.3. Combined with the simulation model, "apodization" is used in acoustic lens for bean control. Adopting different apodization function for apodization, simulation result indicates that "apodization" takes effect in beam control.4. For high attenuation coefficient, the author study the fresnel lens in beam width control. Simulation results indicate fresnel lens structure is useful in beam width control by high attenuation coefficient.5. According to the analysis of both performances of acoustic lens sonar and digital camera, the possibility of CCD based device combined with detector using for lens sonar pixel data transmission has been studied. The results show that the new structure will be very beneficial to lens sonar technology.6. The author implements a experimental system of a acoustic lens imaging sonar to test its performances and got some high resolution images of some small objectsAt the end of this paper, the author give an outlook about sonar technology future development.

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