直接序列展頻接收器的效能，是高度地依賴著，輸入端與本地端的展頻碼(虛擬雜訊碼)之間作同步的精確度和速度；展頻碼的同步分成兩個步驟：一、獲取(粗調)，二、追蹤(細調)。在一般上，這兩個步驟是分別由不同的架構下來執行。近來，適應性最小均方濾波方法被提出，在同一個架構下執行獲取和追蹤，如此可以大大降低系統的硬體複雜度(尤其是對於長的展頻碼而言)，但這個方法是被假設在同調的接收器上。
在本論文中，提出一個新的微分式同調展頻碼同步的方法，也就是微分式偵測器結合適應性限制最小均方濾波演算法，並搭配最大權重值測試法，在同一個架構下執行碼獲取和追蹤；使用微分式偵測器作展頻碼同步，可如同非同調技術，不需要事先得到載波相位，就能作同步。在整數和非整數時間延遲環境下，數值分析和模擬結果已證實，以平均獲取時間而言，提出的方法比傳統的適應性最小均方濾波方法所搭配最大權重值測試或均方誤差值測試法，有更好的獲取效能。同時，在變動的訊雜比和延遲環境下，以平均鎖住的時間和平均誤警所付出的時間而言，所提出的方法，比傳統的適應性最小均方濾波方法，有較好的追蹤能力。

The efficiency of direct sequence spread spectrum (DS/SS) receiver is highly dependent on the accurate and fast synchronization between the incoming and locally generated PN (pseudo-noise) codes. The code synchronization is processed in two steps, acquisition (coarse alignment) and tracking (fine alignment), to estimate the delay offset between the two codes. In general, the schemes for code acquisition and tracking processes are performed, separately, and implemented with different structure. Recently, an alternative approach, with the adaptive LMS filtering scheme, has been proposed for performing both code acquisition and tracking with the identical structure, where the coherent receiver was employed. With this approach, dramatically, hardware complexity reduction could be achieved, especially, when long PN code is considered.
In this thesis, a new differentially coherent code synchronization scheme, based on a differential detector followed by an adaptive constrained LMS (CLMS) filtering algorithm with maximum tap weight (MTW) test scheme, is devised for performing both code acquisition and tracking with the identical structure. With a differential detector for code synchronization, the prior knowledge of the carrier phase is not required as the non-coherent techniques. Numerical analyses and simulation results verify that the proposed scheme has better acquisition performance, in terms of mean acquisition time, than the conventional LMS filtering algorithm with MTW test and mean square error (MSE) test schemes for the integer and non-integer time delay environments. At the same time, the proposed scheme has better tracking capability, in terms of mean hold-in time and mean penalty time, over the conventional LMS filtering schemes, for the variation of signal-to-noise ratio (SNR) and delay offset (delay difference).

Abstract i
Contents ii
List of Figures iv
Chapter 1 Introduction 1
Chapter 2 Conventional Code Synchronization with Adaptive LMS Filtering Scheme
2.1 Introduction 4
2.2 Conventional Code Synchronization with Adaptive LMS Filtering Scheme 6
2.3 Conventional Code Acquisition with Adaptive LMS Filtering Scheme 6
2.4 Mean Square Error (MSE) Test Method for Code Acquisition 9
2.5 The Mean Acquisition Time (MAT) and the Statistics Property 10
2.6 Conventional Code Tracking with Adaptive LMS Filtering Scheme 13
2.7 Verification Mode for Code Tracking 15
Chapter 3 Differentially Coherent Code Synchronization with Adaptive Constrained LMS Filtering Scheme
3.1 Introduction 18
3.2 Differentially Coherent Code Acquisition Based on the Adaptive Constrained LMS (CLMS) Filtering Algorithm with Maximum Tap Weight (MTW) Test Scheme 19
3.2.1 Adaptive CLMS Filtering Algorithm with Maximum Tap Weight (MTW) Test Scheme for Code Acquisition 21
3.2.2 System Probabilities and Mean Acquisition Time (MAT) 26
3.2.3 Practicable Threshold Value Setting for Code Acquisition 28
3.2.4 Comparison of the Acquisition Performance for Different Schemes 29
3.2.4.1 Numerical Results 29
3.2.4.2 Simulation Results 38
3.3 Differentially Coherent Code Tracking Based on the Adaptive CLMS Filtering Algorithm with MTW Test Method and Direct Delay Estimation (DDE) Formula Scheme 38
3.3.1 Adaptive Code Tracking System Description 39
3.3.2 Mean Hold-in Time and Mean Penalty Time 43
3.3.3 Comparison of the Tracking Performance for Different Schemes 44
3.3.3.1 The PDF with MTW and MSE Test methods 44
3.3.3.2 Mean Hold-in Time and Mean Penalty Time 45
Chapter 4 Conclusions 54
Appendix A 55
References 59

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