碩士 / 國立臺灣海洋大學 / 電機工程學系 / 92 / In underwater environment, sonar is the most effective detection device at present. It uses propagation characteristics of acoustic wave to detect targets in the sea. The device at the front stage of sonar is a beamformer used to perform spatial filtering, attempting to suppress noise and eliminate interference. But conventional beamformers are very sensitive to the position error of the sensors, and need prior information about the direction of arrival (DOA) of the desired signal. To overcome the problems mentioned above, we adopt a blind adaptive beamformer as the device at the front stage of underwater sonar detection system.
When detecting submarine in underwater environment, acoustic sinusoidal signals generated by submarine propeller blade can be used for this task. But received signals are seriously distorted by the broadband noise from submarine engine and underwater environment, and multi-path channel effect. The information that we may have is the sinusoidal waves with unknown frequencies generated by propeller blades. Therefore, frequency estimation method is employed to estimate frequency and fed to a phase lock loop（PLL）to lock the desired frequency in order to suppress noise and eliminate interference. Next, the detector and the associated decision device are designed using statistical optimum decision theory. Finally, to evaluate the performance of the proposed underwater sonar detection system, computer simulations for Rayleigh fading channel are carried out.
| Identifer | oai:union.ndltd.org:TW/092NTOU5442034 |
| Date | January 2004 |
| Creators | Ming-Yi Guan, 管明義 |
| Contributors | Hsien-Sen Hung, 洪賢昇 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 70 |
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