臺灣博碩士論文加值系統

聲波於水下通道傳遞時，通常會受到水下環境的反射與散射之影響，導致訊號受到多重路徑干擾而產生符元間際干擾，而等化器是解決此問題的一種方法。本論文先探討兩種盲蔽式適應性等化器，以電腦模擬方式比較盲蔽式常模數(CMA)等化器及結合鎖相迴路的盲蔽適應性等化器的效能，發現這兩種等化器本質上是相同的。
為了達到即時通訊的需求，我們以DSP單晶片來進行QPSK調變與盲蔽式等化器之韌體設計與實現。此盲蔽式等化器利用通訊信號的週期平穩特性來設計，不須使用訓練序列訓練來調適通道特性，並可更快速收斂及達到較好的位元錯誤率。此外在水槽環境下作資料傳輸時，此收發機系統可以有效改善在多重路徑傳播的效應。
關鍵字：水下通道、通道效應、等化器、週期平穩、盲蔽式、適應性。

When propagation through a underwater channel, acoustic waves are usually affected by reflection and scattering of underwater environment, therefore, signals are seriously distorted by multipath interference, leading to the intersymbol interference. Equalizer is one of the solutions to this problem. In this paper, we first investigate two blind adaptive equalizers, namely the blind constant modulus(CMA) and the PLL-based blind adaptive equalizer, and then compare their performances by computer simulations. We find that these two equalizer are essentially equivalent.
For real-time communications, DSP chips are used for the firmware design and implementation of QPSK modulation and PLL-based blind equalization. Using the cyclostationarity of communication signals, the PLL-based equalizer does not require training sequence to adapt channel variations, exhibits faster convergence speed and better bit-error rate. For performance evaluation, the DSP-based transceiver is tested by data transmission through the channel of a watertank. Experimental results show that the transceiver can significantly improve the multipath effect.
Keywords：underwater channel, channel distortion, equalizer, cyclostationary, blind, adaptive.

第一章 緒論
1.1 簡介…………………………………………………… 1
1.2 研究動機……………………………………………… 2
1.3 各章節內容概述……………………………………… 3

第二章 盲蔽適應性等化器之比較
2.1 適應性等化器概論…………………………………… 4
2.1.1 等化器………………………………………………… 4
2.1.2 適應性演算法最小均方( LMS )演算法……………… 7
2.2 盲蔽適應式等化器…………………………………… 9
2.2.1 常模數等化器………………………………………… 10
2.2.2 結合鎖相迴路之盲蔽適應性等化器………………… 11
2.2.3 盲蔽式適應性等化器之比較………………………… 13

第三章 盲蔽適應性通訊系統之實現
3.1 數位訊號處理之簡介………………………………… 19
3.2 發射機之韌體實現…………………………………… 20
3.2.1 正交相位移鍵( QPSK )調變器……………………… 21
3.2.2 以C6211 DSK實現之發射機程式流程………………… 23
3.2.3 發射機訊號量測……………………………………… 26
3.3 結合鎖相迴路盲蔽適應性等化器之韌體實現……… 29
3.3.1. 同步及複數希爾伯轉換……………………………… 29
3.3.2 鎖相迴路與等化演算法之運算式…………………… 32
3.3.3 以C6711 DSK實現之接收機程式流程……………… 34
3.3.4 接收機初步功能檢查………………………………… 36

第四章 水槽之測試與討論
4.1 實驗硬體配置………………………………………… 39
4.2 水槽試驗……………………………………………… 42
4.2.1 實際測量結果………………………………………… 43
4.2.2 實驗結果統計資料…………………………………… 47

第五章 結論與未來展望 48

參考文獻………………………………………………………… 49
附錄 ……………………………………………………… 51

參考文獻

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