本論文以數值模擬及實驗的方法，探討合成孔徑聲納（Synthetic Aperture Sonar; SAS）成像之基本原理。SAS是傳統聲納技術的改進，是利用小尺寸實孔徑聲納陣列，沿著運動軌跡上直線前進，利用發收訊號的位置與相位的關係，將回波數據做疊加處理，而獲得較高的分辨率。由於聲納若需獲得高分辨率，則需要增加聲納陣列的長度，這不但會增加聲納系統的造價，且導致聲納波束之旁波瓣增加，而影響聲納效能。本研究根據SAS基本原理，首先以數值模擬的方式進行各種因子對分辨率的影響，包括實體孔徑、載波頻率、平臺移動速度、頻帶寬度及脈衝時間長度等，對於SAS成像技術的影響。數值模擬結果顯示，當實體孔徑減小時，主波瓣雖然變寬，但經合成處理之後，主波瓣變窄，因而提高方位向分辨率。當頻帶寬度增加，其主波瓣寬度會減小，然而旁波瓣亦隨之增加，故操作時應慎選頻帶寬度，以利獲取更好的解析度。此外，為確保航向上有足夠的採樣數目以維持方位向的解析度，平臺移動速度不能太快。若適當增加時間脈衝長度可以獲得較大的功率，使聲納探測距離增長。有關SAS基本原理，本研究亦於水槽進行實驗，以AST MK VI 192 kHz的換能器作為波發與接收，藉由單一（直徑 8 cm）及多個大小不等的球體（3 cm、6 cm、8 cm）作為目標物，資料擷取之後，經SAS分析處理，獲得了初步的驗證。本研究透過數值模擬與實驗分析的方法，對於SAS的基本原理有了初步的瞭解，可提供後續研究之參考。

This research is to study the fundamental theory of Synthetic Aperture Sonar (SAS) through numerical simulation and experimental analysis. The basic principle of SAS is to enhance the capability of spatial resolution by moving the transducer element to increase aperture so that it achieves a better resolution. The factors affecting the capability of resolution include the actual size of the transducers, frequency and its bandwidth, pulse length, and moving speeds. The effects of various factors on the resolution were examined through numerical simulation. The results have shown that the smaller the true size of the transducer, the better the resolution. Moreover, when the bandwidth is increased, the resolution also increases. The SAS is sensitive to the speed of movement due to the fact that data acquisition may be limited, therefore the speed can not be too high, e.g., less than 1.5 m/s. The experiment was carried out in a water tank of size 4 m x 3.5 m x 2 m. The transducers of AST MK VI 192 kHz were employed to transmit and receive signals. Copper spheres of various sizes (3 cm, 6 cm, 8 cm diameter) were used as targets. The data were obtained and analyzed, and the results have shown that the resolution may be achieved by SAS analysis, establishing the fundamental principle and offering opportunity for future study.

第一章 緒論 1
1.1 動機與背景 1
1.2 文獻回顧 2
1.3 研究目的 3
第二章 SAS 運作原理 5
2.1 分辨率 5
2.2 SAS 與 SAR 之比較 10
2.3 成像限制 12
2.4 成像演算法 15
2.5 結語 18
第三章 SAS 數值模擬 19
3.1 簡介 19
3.2 參數設定 19
3.3 模擬成像 20
3.4 成像效益 25
3.5 結語 29
第四章 SAS 實驗與分析 31
4.1 實驗目的 31
4.2 設備簡介 31
4.3 參數設計 37
4.4 數據處理 44
4.5 討論 55
4.6 結語 57
第五章 結論與建議 59
5.1 結論 59
5.2 建議 60

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