Towed Array Technology
Thursday 11th November 2010, 1300hrs–1430hrs
Chaired by Bill Mildon The Theory of Optimum Linear Data Fusion of Multiple Professor Qihu Li, Institute of Acoustics, Chinese Academy of Sciences, China Xiuting Yang; Liping Dong; Yuan Li, nstitute of Acoustics, Chinese Academy of Sciences, China For a long time, Data Fusion is one of the most important aspects of sonar signal processing. The earliest discussion for the data fusion comes from the field of radar signal processing. It is well known that the data fusion problem can be categoried as three levels, i.e. data level, feature level and decision level. A typical scenario of sonar signal processing will be studied in this paper. That is the multiple observations data fusion for same parameter. The observation data, due to some reason, may have different estimation error and can be independent or dependent. The optimum linear data fusion for two independent observations has been studied by many authors. In this paper, the case of multiple independent observations, or even dependent multiple observations are studied in details. The basic theorem in data fusion theory is derived. It is proved that the estimation error of optimum linear data fusion is not greater than that of individual components. This theorem will be proved in each case for two or multiple observations, regardless the dependency among observations. The closed form expression of optimum data fusion solution and numerical examples are given. A combination of towed array sonar and cylindrical sonar will generate much better bearing estimation in using optimum linear data fusion theory will be described in this paper. Effects of the Shallow-water Waveguide on the CBF Performance of the Towed Uniform Long Linear Array Dr Lei Wang, Institute of Acoustics, Chinese Academy of Sciences, China The array gain (AG) of long towed linear array may be degraded seriously in the littoral environment, especially on the near endfire direction and the very low frequency band (<100Hz). A statistical received signal model, combined with the simplified channel parameters, is established to assess the effects of the waveguide propagation on the conventional beam forming (CBF) performance, including target bearing spread and physical achievable array gain. The target beam spread, as the function of signal frequency and bandwidth, simplifying channel structure parameters (equivalent layer depth, and boundary reflectivity), array aperture, and the target bearing, is deduced theoretically and simulated numerically based on the Kraken program. The results show that the array signal gain degradation (ASGD) is mainly due to the signal relative bandwidth, waveguide thickness and target bearing. In our primitive acoustic experiment, performed in the South China Sea (water depth 75m), a 256m long linear array with the signal bandwidth from 30Hz to 1.2kHz is used to validate the analysis results. Research of Vibration Characteristics of Underwater Cables in Very Low Frequency Signal Exploration Mr Ma Xuejie, Institute of Acoustics, Chinese Academy of Sciences, China Li Yuan/ Li Qihu, Institute of Acoustics, Chinese Academy of Sciences, China The VIM (vibration isolation module) is one of the most important components in towed array sonar. At low frequencies, the vibration isolation less effective and even has a larger phenomenon. In the frequency range of 20Hz ~ 100Hz, the vibration isolation effect of excitation frequency increases with the increase in. But VLF (Very Low Frequency) signal exploration gives attention to the frequency range of under 100Hz. In this paper, tow cable vibration characteristics essential for VIM research are obtained experimentally and VIM theoretical analysis methods are given along with theoretical values that indicate vibration isolation effects varying with VIM. The experimental data and analysis results provide a technologic basis to design VIM (Vibration Isolation Module) of the underwater cable in towed array sonar.
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Diamond Industry Patron
Attracts all the right people from the naval defence sector. A very successful ‘first-in-class’ event.
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Kathryn Smyth
Economic Intelligence and Marketing Officer, DCN
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