臺灣博碩士論文加值系統

摘 要

無線通訊帶動人們遠距離的溝通互動，而隨著數位多媒體的發展，高資料量影像、視訊、聲音等傳輸成為無線通訊上的主流應用，無線通訊技術進入一個新的時代。無線行動通訊採用數位訊號處理技術，不但提升傳輸速率、訊號品質與保密性，也大幅提升頻寬效率。
將資料分成多個子載波(subcarrier)傳送是正交分頻多工(OFDM)系統的主要概念，此技巧可以大幅提升頻寬效率。OFDM現階段主要的調變技巧主要有垂直振幅調變(QAM)、相位調變(PSK)等技術。其中垂直振幅調變由於傳送速度快，調變機制易實現，較廣被使用；相位調變則是由於功率消耗較低取勝，但缺點是傳送速度較慢而且當應用到M-ary PSK時，複雜度會增加許多，造成實現上的困難。
本論文採差異振幅與相位調變方式(Differential Amplitude and Phase Shift Keying，DAPSK)作為主要的調變架構，以及格雷編碼(Gray code)來當做數位訊號的編碼技巧，藉此以避開同調(Coherent)解調可能帶來的成本過高問題，同時降低系統複雜度。
本論文在最後同時針對差異振幅與相位調變提出改善方案，將DAPSK的架構中的振幅值，從乘方變化改善成等差增加，希望對DAPSK架構中的峰對平均值功率比值(PAPR)再降低。控制在Multi-Ring時，振幅值不會嚴重擴張，藉以達到功率不會浪費的目的。

關鍵字：正交分頻多工、差異振幅與相位調變、格雷編碼、峰對平均值功率比值

Abstract
Wireless communication makes the interaction between the people who is far away to the others. With the digital multimedia development including image, audio and video, wireless communication goes to a new era. The technology of wireless communication is digital signal process that can promote the rate of data transmission, the quality of signals, the data confidentiality of user, and the efficiency of bandwidth.
OFDM uses several subchannels to transmit data. Compared with single carrier system, the bandwidth of multicarrier communication system is much narrow. The main technologies of OFDM are Quadrature Amplitude Modulation (QAM) and Phase Shift keying (PSK). With the high speed data transmission and the system that is easy to realize, QAM is used widely. The strength of PSK is the lower transmission power, but it is difficult to realize for the two reasons. First, the data transmission rate is lower. Second, when PSK is used in M-ary, the system complication will increase.
In the paper, the modulation used in system is DAPSK (Differential Amplitude and Phase Shift Keying). With means of Gray Code, it can not only avoid the problem of high prime cost in coherent demodulation but also reduce the complexity of system.
Finally, we proposed a formula to improve the ring ratio of amplitude. In order to reduce PAPR in DAPSK, we used the power difference to calculate new ring ratio. It will not waste power when the amplitude is increased in Multi-Ring.

Keywords : OFDM、DAPSK、Gray Code、PAPR

目　錄

第一章 序論..................................... 1
1.1 簡介....................................... 1
1.2 研究背景................................... 3
1.3 研究目的與動機............................. 3
1.4 各章節內容概述............................. 4
第二章 同調解調系統應用於正交分頻多工............. 7
2.1 正交分頻多工技術的發展背景................. 7
2.1.1 正交分頻多工的系統起源.................. 7
2.1.2 正交分頻多工的改進與發展................ 8
2.1.3 正交分頻多工系統的應用.................. 9
2.2 正交分頻多工的原理......................... 9
2.2.1 正交分頻多工技術的調變模型.............. 10
2.2.2 正交分頻多工技術的正交原理.............. 12
2.3 正交分頻多工系統的優點..................... 14
2.3.1 抗頻率選擇性衰落........................ 14
2.3.2 OFDM與傳統FDM頻譜比較.................. 15
2.3.3 OFDM與傳統單載波的頻寬使用效率......... 16
2.3.4 可變的調變方式.......................... 17
2.3.5 抵抗多重路徑干擾與單頻網的實現.......... 18
2.4 同調解調技術應用於正交分頻多工............. 18
2.4.1 垂直振幅調變(QAM)用於正交分頻多工系統.... 18
2.4.2 相位位移鍵(PSK)用於正交分頻多工系統...... 21
2.4.3 PSK與QAM的優缺比較..................... 24
2.5 非同調解調技術應用於正交分頻多工........... 25
2.5.1 非同調調變技術背景...................... 26
2.5.2 非同調調變技術原理...................... 26
2.6 峰對平均值功率比........................... 27
2.6.1 峰對平均值功率比過高之影響.............. 27
2.6.2 峰對平均值功率比........................ 28
2.6.3 降低PAPR技術.......................... 29
第三章 差異相位調變技術之應用..................... 31
3.1 格雷碼用於非同調系統....................... 31
3.2 DBPSK原理................................. 35
3.2.1 差異相位調變原理........................ 35
3.2.2 DBPSK原理.............................. 37
3.3 DQPSK原理................................. 40
3.4 D16PSK、D32PSK與D64PSK.................... 43
3.4.1 D16PSK.................................. 44
3.4.2 D32PSK.................................. 45
3.4.3 D64PSK.................................. 46
第四章 差異振幅相位位移鍵調變技術與多環式差異相位位移鍵..................................... 47
4.1 D16APSK基本原理........................... 47
4.2 D64APSK基本原理........................... 55
4.3 差異振幅相位位移鍵調變於正交分頻多工系統... 61
4.4 多環式差異相位位移鍵調變之原理............. 63
4.5 多環式差異相位位移鍵調變於正交分頻多工系統 65
第五章 實驗結果與模擬............................. 67
第六章 結論與未來發展............................. 81
參考文獻 ........................................ 83

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