超寬頻系統能應用於室內的無線個人區域網路( WPAN )或小範圍無線區域網路( WLAN )的傳輸，但由於室內稠密的多重路徑影響，會造成系統更多功率消耗，傳統上使用耙式接收機來提升系統效能。但基於設計複雜度的考量，選擇性耙式接收機的概念亦能夠用來取代傳統耙式接收機。選擇性耙式接收機僅選擇在多重路徑中，增益較大的幾個路徑來提高系統效能。因此，我們需要能夠精準判斷多重路徑以獲得最大效能。首先我們使用CLEAN 演算法來估測最大能量路徑，但是由於頻率選擇性衰變的影響，使得傳送訊號在經多重路徑通道後會由於訊號的散射、繞射或反射導致失真，造成原先藉由擷取傳送訊號與接收訊號之交相關峰值的CLEAN 演算法已不再適用，因此我們使用Multiscale CLEAN 演算法來處理此一變化。Multiscale CLEAN 藉由計算一整組波型之交相關值來選取傳送波型在通道中有可能產生的變化，再針對其變化來做扣除的動作。利用此一步驟使得我們能夠處理由於訊號失真所導致錯誤選擇之偏差路徑，得到更精準的多重路徑解析，同時使用最大比例結合( Maximal Ratio Combining ）給予其路徑增益，以產生效能更佳之訊號。對於通道的頻率選擇性衰變對訊號造成的影響，我們使用二階微分之高斯函數波型，利用波形之不同有效寬度值，所對應之頻譜範圍及衰落程度來表示。並針對此一描述，進行兩演算法之模擬。而後更對其臨界值的設定與訊雜比輸入之關係做探討。在模擬結果能夠發現，使用Multiscale CLEAN 演算法之搜尋路徑精確度較CLEAN 演算法來的優異許多，即使增益較小路徑也能精準擷取，而CLEAN 演算法則無法有效搜尋路徑。

Ultra-wideband systems can be used in indoor wireless personal area network (WPAN) or short-range wireless local area network (WLAN) transmission. Yet owing to the effects of indoor dense multipath, it will cause more power consumption. We usually use Rake receiver to improve system performance. However, we should do some compromise between system performance and the design complexity. Thus, the concept of Selective Rake can be used to substitute for the conventional Rake receiver. Selective Rake receiver uses fewer but more powerful paths instead of using all the paths to raise system performance. Hence, we have to precisely detect the multipath components for best performance. Earlier we use CLEAN algorithm to estimate the multipath components. The CLEAN algorithm can be used in selecting the paths with relatively high energy. But as the impact of frequency selective fading makes the transmitted signal distorted, the CLEAN algorithm no longer applies to this situation. Thus, we use Multiscale CLEAN algorithm instead. Multiscale CLEAN algorithm calculate the value of cross-correlation between the received signal and a set of waveforms, and then choose the higher one as the waveform transmitted. Besides, we use Maximal Ratio Combining to weigh the different paths to get the signal with more power. We represent the signal affected by frequency selective fading by using the second derivatives of Gaussian waveform function with different effective widths of pulse. The waveforms corresponding different effective widths have different spectra which represent the different effects of fading. It is seen that that the multiscale CLEAN has better performance than the CLEAN algorithm with more precise estimation of multipath components. In simulation result, we can figure out path searching using Multiscale CLEAN algorithm is more accurate than using CLEAN algorithm. Even the path with smaller energy gain, using multiscale CLEAN algorithm can search successfully, while CLEAN algorithm cannot do.

致謝. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
中文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
英文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
圖目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
表目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
1 緒論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 研究背景. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 研究動機. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 論文架構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 文獻回顧. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 超寬頻傳輸通道模型. . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 大區域範圍衰減統計特性. . . . . . . . . . . . . . . . . . . . . 5
2.1.2 小區域範圍衰減統計特性. . . . . . . . . . . . . . . . . . . . . 6
2.2 訊號模型. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 超寬頻系統頻寬定義. . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 高斯脈衝波形. . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.3 接收及傳送信號. . . . . . . . . . . . . . . . . . . . . . . . . 11
3 選擇性耙式接收機. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1 系統概念與架構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 多重路徑估測. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4 Multiscale CLEAN 演算法之應用. . . . . . . . . . . . . . . . 19
4.1 演算法概念及架構. . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2 Multiscale CLEAN 演算法應用於超寬頻系統. . . . . 22
5 電腦模擬與分析. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 25
5.1 系統參數設定. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.2 選擇性耙式接收機效能分析. . . . . . . . . . . . . . . . . . . 26
5.2.1 通道假設. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6 結論與建議. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
6.1 結論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
6.2 未來工作建議及衍生. . . . . . . . . . . . . . . . . . . . . . . . .. 52
參考文獻. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

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