台灣四面環海，港灣防衛一直是重要的議題及發展方向，而聲學偵測又為進行港灣防衛有效的方式之一。無論要建置被動或主動的聲學系統，皆須掌握港灣的聲場特性。當訊號在水下傳遞時，會因折射、反射或散射造成一定的多路徑效應(Multipath effect)，並且聲波能量也會因高噪度的船舶活動與底床吸收，導致訊雜比降低，造成偵測移動目標物的接收訊號受到干擾而發生接收錯誤。有鑑於此，本研究主要的目的為透過主動偵測實驗，發展主動聲納回波訊號之處理流程，並研究利用模糊度函數(Ambiguity function)解析港灣環境固定結構及動態結構物的可行性，期望與實驗室自行研發之自收發聲納系統結合，發展自主式港灣防衛主動聲納系統偵測雛形。
在主動偵測過程中，主動聲納拍發之聲波將被水面、海床或水下目標物反射，而當聲源與目標物之間有相對位移存在時，會產生中心頻率位移的現象，稱為都卜勒效應(Doppler effect) ，此回波訊號頻率位移可作為偵測判斷之標的。為發展水下主動偵測的技術，本研究團隊分別於2017年5、6月在高雄港外以海研三號研究船(R / V OCEAN RESEARCHER III)為載台，下放本研究團隊自行研發之自收發拖曳式聲納系統(Towed sonar system)進行水下目標物之主動偵測實驗；同年12月於高雄港內使用定點收發聲納系統進行聲學實驗。實驗過程使用具有高辨識度與高抗噪性的掃頻訊號(Linear Frequency Modulation，LFM)量測水下通道脈衝響應(Channel Impulse Response，CIR)，並使用具有高頻率辨識度之最大序列碼訊號(Maximum Length Sequence，MLS)結合模糊度函數進行反射都卜勒分析，解析水下環境狀態，討論高雄港內及港外在偵測水下目標物方面所面臨之困難，並可作為日後發展港灣防衛系統雛形之依據。

Taiwan is surrounded by ocean so that harbor defense has always been one of the most important topics of development priorities. Whether building a passive or active acoustic system, we must first grasp the sound field characteristics of the harbor. When soundwave propagated in ocean, the energy of soundwave will be absorbed by boundary or will decrease due to multipath effect. In this situation, to detect underwater target became more difficult and inaccurate due to the poor signal to noise ratio (SNR). Thus, the aims of this research were to develop received signal processing methods which conducted by active acoustic experiment, using Ambiguity function to analyse moving target condiction and combined with our towed sonar system to develop harbor defenses prototype.
In the application of active acoustic, soundwave emitted form active sonar will be reflected by sea surface, ocean boundary or moving target. When there is relative motion between the source and the target, Doppler phase-shift effects will cause frequency of received echo changed. In order to undertake the analysis of active acoustic underwater detection, this research using Linear Frequency Modulation (LFM) and Maximum Length Sequence (MLS) which both have high degree of recognition and high noise immunity to detect moving target. After doing pulse compression and compensate the doppler shift, we can estimate speed and direction of moving target even as positioning.

誌謝 ii
摘要 iii
Abstract iv
目錄 v
圖次 vii
表次 xi
第一章 緒論 1
1.1 前言 1
1.2 研究動機與研究目的 3
1.3 文獻回顧 4
1.4 論文架構 13
第二章 研究方法與理論 15
2.1 脈衝壓縮 16
2.2 都卜勒效應 23
2.3 模糊度函數與最大長度序列碼訊號 25
第三章 港外水下目標物偵測實驗 28
3.1 主動聲學前導實驗 ― 水槽實驗 29
3.2 高雄港外水下目標物偵測實驗簡介 32
3.2.1 實驗地點與各航次細節 32
3.2.2 拖曳式自收發聲納系統 (Towed sonar system) 39
3.2.3 溫壓記錄儀(Temperature depth recorder) 43
3.2.4線性頻率調變訊號(Linear Frequency Modulation，LFM) 44
3.3實測資料分析結果 46
3.3.1 港外水下目標物偵測實驗結果 46
3.3.2 港外水下目標物反射都卜勒模擬 53
第四章 港內移動目標物偵測實驗 59
4.1高雄港內移動水下目標物偵測實驗簡介 59
4.1.1 實驗地點與日期 59
4.1.2 實驗儀器配置 60
4.1.3 實驗移動目標物 61
4.1.4 實驗聲源訊號 62
4.2高雄港內環境與移動目標物分析 64
4.2.1 場域分析與環境背景資訊 64
4.2.2 目標物移動狀態分析 65
4.3實測資料分析結果 70
4.4 主動聲納系統佈放深度探討 82
4.4.1主動聲納系統佈放深度探討 82
4.4.2移動目標物偵測 85
第五章 結論與討論 89
5.1實驗結果統整與探討 89
5.2使用限制與未來應用 91
5.2.1 非單一反射體辨識 91
5.2.2 目標物速度估算應用 91
參考文獻 93
附錄一 主動聲學實驗日誌 97
附錄二 高雄港內環境背景噪音 100

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