臺灣博碩士論文加值系統

在無線通訊系統裡，軟體無線電概念之接收機,降低了硬體設計時所需要的成本,而且整體數位化的解調流程,有利於後續接收機能以軟體的方式實現。數位正交解調技術為實現軟體無線電概念之接收機架構,此解調方法是將訊號以符合某種特定取樣頻率來取樣,取樣後的訊號再透過一些規律的運算式得到正確的解調。若取樣時採用帶通取樣法則,將能大幅度地降低取樣頻率,減輕硬體電路在設計時的困難,而其電路設計較具彈性靈活的優點,非常適用於軟體無線電。在本論文中,我們嘗試著解決多頻帶數位正交解調器中載波頻率偏移與符元時序同步的問題。我們提出的方法是運用半頻帶濾波器組與帶緣濾波器組以及多相濾波器組結合的概念,來達到符元時序同步與載波回復。
我們將用電腦模擬驗證所提出方法的正確性。

In wireless communications systems, the concept of software radio is to reduce the cost of the hardware modifications by implementing most of the receiver functions with software. The digital quadrature demodulation technique is one way to implement the concept of the software radio. This method first samples the modulated signal using a sampling frequency which satisfies certain conditions, then acquire the demodulated signal from the sampled signal via some very simple rules. If a bandpass sampling frequency is adopted, we can substantially lower the sampling frequency. This in turn reduces the cost and the complexity of the receiver. In this thesis, we try to solve the problems of carrier frequency offset and symbol timing synchronization
in multiband digital quadrature demodulators. We propose a method to achieve the symbol-timing and carrier recovery by using half band filters, the band-edge filters , and polyphase filter banks. The goodness of the proposed method is demonstrated by computer simulation.

第一章 緒論. . . . . . . . . . . . . . . . . . . 1
1.1 軟體無線電簡介 . . . . . . . . . . . . . . . 1
1.2 研究動機與目的 . . . . . . . . . . . . . . . 3
1.3 論文架構 . . . . . . . . . . . . . . . . . . 3
第二章 數位正交解調器之多相濾波器組 .. . . . . . 5
2.1 正交解調器原理說明 . . . . . . . . . . . . . 5
2.1.1QPSK調變器 . . .. . . . . . . . . . . . . . 5
2.1.2 數位正交解調器 . . . . . . . . . . . . . . 8
2.2 多相濾波器(Polyphase Filter)[9] . . . . . . 9
2.2.1 多相濾波器之升頻架構 . . . . . . . . . . . 9
2.2.2 多相濾波器之降頻架構 . . . .. . . . . . . 12
2.3 半頻帶濾波器(half-band filter)[10]. . . . . 13
第三章 多組射頻訊號之數位正交解調技術 . . . . . 21
3.1 平方根升餘弦濾波器與匹配濾波器 . . . . .. . 21
3.2 單組射頻訊號之數位正交解調技術 . . . . . . 25
3.3 兩組射頻訊號之數位正交解調技術 .. . . . . . 29
3.3.1 數位正交解調流程原理與說明 . . . . . . . 29
3.3.2 避免疊頻現象之正交取樣條件 . . . . . . . 35
第四章 數位正交解調器之符元同步與載波回復 . . .40
4.1 載波偏移回復技術. . . . . . . . . . . . . . 40
4.1.1 造成通訊系統載波頻率偏移因素 . . . . . . 40
4.1.2 載波頻率偏移回復技術 . . . .. . . . . . . 43
4.2 符元時序估測 . . . . . . . . . . . .. . . . 50
第五章 電腦模擬結果. . . . . . . . . . .. . . . 56
5.1 雙頻帶濾波器解調技術之符元時序模擬 . . . . 59
5.2 雙頻帶濾波器解調技術之載波回復模擬 . . . . 62
5.3 載波回復技術之錯誤率效能分析 . . . . . . . 67
第六章 結論 . . . . . . . . . . .. . . . . . . .76

[1] Simon Haykin, Communication systems, 4th, New York : Wiley, 2001.
[2] A. V. Oppenheim, R. W. Schafer, and John R. Buck, Discrete-Time Signal Processing, 2nd, New Jersey : Prentice Hall, 1999.
[3] A. V. Oppenheim and R. W. Schafer, Digital Signal Processing. Englewood Cliffs, New Jersey : Prentice Hall, 1975.
[4] Heinrich Meyr, Marc Moeneclaey and Stefan A Fechtel, Digital Communication Receivers, New York :
Wiley, 1998.
[5] Dennis M. Akos, Michael Stockmaster, James B. Y. Tsui,and Joe Caschera, "Direct bandpass sampling of multiple distinct RF signals". IEEE Trans. on communications, vol. 47, no. 7, pp. 983-988, Jul. 1999.
[6] 郭益男," 多頻帶數位正交解調器之符元同步與載波回復技術", 國立海洋大學電機工程學系碩士論文, 2005.
[7] Fredric J. Harris , Multirate Signal Processing for Communication Systems, Prentice Hall, 2004.
[8] K. C. HO, Y. T. Chan, and R. Inkol, "A Digital Quadrature Demodulation System", IEEE Trans. on
Aerospace and Electronic systems, vol. 32, no. 4, pp. 1218-1227, October . 1996.
[9] Vaidyanathan, P.P.and Liu, V.C. ," Classical sampling theorems in the context of multirate and polyphase digital filter bank structures", IEEE Transactions on Acoustics. speech, and signal processing, vol. 36, no. 9, September 1988.
[10] Jinguji, K. and Oguma, M. , "Optical half-band filters", Journal of Lightwave Technology, vol. 18, no. 2, February 2000.
[11] 鄭經達, "衛星數位視訊廣播系統之多頻帶數位正交解調接收機", 國立海洋大學電機工程學系碩士論文, 2004.
[12] Muschallik,C.," Influence of RF oscillators on an OFDM signal Consumer Electronics", IEEE Transactions on communications, vol. 41, no. 3, pp. 592-603, August. 1995.
[13] Rice, M. and harris, f.," Polyphase Filter Banks for Symbol Synchronization in Sampled Data Receivers", MILCOM-2002, Anaheim, CA, Octobel, 2002.
[14] 蕭振鐸, "雙頻帶數位正交解調器之FPGA實現", 國立海洋大學電機工程學系碩士論文, 2005.