合成孔徑聲納（Synthetic Aperture Sonar, SAS）之基本原理乃是藉由陣列系統之運動，並經由信號處理的方式，以達提高目標物辨識能力之目的。合成孔徑應用於聲納系統上既可達到高解析度與長距離傳播的需求，因此成為重要的研發技術。SAS 基本觀念源自合成孔徑雷達（Synthetic Aperture Radar, SAR），惟在實務應用上仍然有諸多待克服的困難，如：操作平臺不平穩、環境的變異等。有關本實驗室在 SAS 之研究，先前宋（2010）已進行橫向（與操作平臺平行之方向）解析度之實驗與分析，並獲致良好的結果，惟在縱向（同聲波發射方向）解析度方面，仍有改進的空間，因此，本文將以縱向解析度分析為主題，進行實驗與分析。縱向解析基本上是藉由脈衝壓縮（pulse compression）的信號處理方式，將目標物在縱向方面的特性解析，以達辨識的目標，而其效能乃受到目標物性質、排列方式、頻寬、波型、脈衝長度等因素的影響。

本研究於中山大學無響水槽（4 m × 3.5 m × 2 m）進行實驗，以AST MK VI 192作為發射與接收器，量測多個大小不等之銅球目標物散射，並分析上述所提之各種因素對於縱向解析能力的影響。本研究進行雙體銅球散射場之分析，已現有儀器設備探討並獲致主要結果包括：（1）聲納所發射之脈衝長度與回波訊號有關且正好涵蓋整個物體之最短脈衝長度是2L/c；（2）SAS 實現低頻率又具高解析度的要求；（3）發射聲波 192 kHz 會有暫態現象產生，結果顯示將此訊號當一般訊號進行處理即可；（4）對於訊號頻寬為 20 kHz其縱向解析度為 7.5 cm。本實驗完成之後，擬於西子灣海洋實驗場進行實海域實驗，以期達到實物應用的目標。

The basic principle in SAS is to use an array which is small in length to create a long synthetic array thus the better resolution is achieved through the use of signal processing. Additionally, the resolution that is independent of range and signal frequency, makes SAS a advantageous tool for applications. Although the origin of SAS comes from SAR, SAS still needs to overcome all constraints for real-world application. In a previous study by Sung and prof. Liu, published results of the along track resolution experiments which were well done however there was still much room in range resolution, the purpose of this research is to achieve high range resolution at any ranges. Indeed there are many existing factors affecting the capability of resolution which including characteristic of the target, certain arrangements of targets, bandwidth, waveforms and pulse duration and etc. High range resolution is obtained using pulse compression techniques.

The experiments were carried out using the transducers of AST MK VI 192 kHz which were employed to transmit and receive signals, scanned various copper balls at anechoic water tank(4 m × 3.5 m × 2 m) in NSYSU. From the equipment we have now results were evaluated based on both simulated and real data: for the range resolution the pulse length is very important the shortest pulse length on an object would be 2L/c theoretically, the measured range resolution is about 7.5 cm for the 20-kHz bandwidth signals and 5 cm for along track resolution. As all the experiments have been successful in the Water Tank, we intent to launch further investigation of this research to the real world application of SAS i.e. in Sizihwan Bay Marine Test Field.

第一章 緒論 1
1.1 研究背景與動機 1
1.2 文獻回顧 3
1.3 研究主題與方法 4
1.4 論文範疇 5
第二章 合成孔徑聲納數值模擬 6
2.1 正側視條帶式合成孔徑聲納系統 6
2.2 SAS 參數設定與模擬結果 7
2.3 結語 25
第三章 實驗設計與資料處理 26
3.1 實驗目的 26
3.2 實驗儀器 26
3.2.1 資料處理程式 32
3.3 實驗方法 33
3.4 資料處理 37
3.4.1 解析度 37
3.4.2 取樣原理 39
3.4.3 快速傅立葉轉換 39
3.4.4 希爾伯特轉換 40
3.4.5 脈波長度對目標物回訊的影響 41
3.4.6 脈衝壓縮原理 42
3.4.7 資料取得 44
3.5 結語 48
第四章 縱向解析度分析 49
4.1 雙體目標物分析 49
4.1.1 脈波長度的影響 51
4.1.2 調變函數分析 54
4.1.3 變換操作頻率 57
4.1.4 縱向解析能力 63
4.2 佐證資料之正確性 67
4.3 模型目標物實驗 70
4.4 結語 74
第五章 結論與建議 75
5.1 結論 75
5.2 建議 76

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