臺灣博碩士論文加值系統

在水下環境中,聲波為無線傳輸的主要媒介,近年來通訊技術的發達,數位通訊技術已普遍應用於水下通訊中,以克服聲波訊號傳輸時遭遇的能量損耗、多重路徑與都卜勒效應等問題,另一方面配合著數位訊號處理器的進步,全數位化的架構將是未來通訊系統的發展趨勢。
全數位水下收發機採用QPSK調變/解調技術,並應用全數位化鎖相迴路克服通道所造成的相位變動,達成接收端的載波回復,在全數位的架構中,系統的調整更具彈性,訊號的調變/解調與載波同步皆以軟體的方式,於數位訊號處理器中實現,全數位鎖相迴路以數值控制的方式產生同步的弦波,適合應用於全數位化之系統。在硬體實現上,以TMS320~C6X~DSK數位訊號處理模組為核心搭配數位類比間的轉換界面電路,與傳統實現方式相比,架構更為精簡。軟體方面,則是以C6X組合語言與C語言來實現系統程式,在整合式的軟體開發工具CCS上發展C6X程式。完成軟硬體實現後,進行基礎發收測試與水槽實驗,經由傳送數據資料,可初步驗證全數位水下收發機的正確性。

The underwater acoustic channel is characterized as a time-varying multipath environment, which in addition to possible Doppler effect make developing an underwater communication system a very challenging task. Digital communication technology was used popularly to deal with these problems in recent years. Underwater communication systems generally use phase-shifting-keying (PSK) modulation/demodution techniques.
In conventional receiver, carrier recovery is conducted by controlling the frequency and phase of the voltage controlled oscillator (VCO) in the phase-locked loop. The QPSK modulation techniques for all-digital underwater acoustic transceiver are investigated in this thesis. An all-digital PLL (ADPLL) for QPSK carrier recovery is employed to overcome the channel effect. The frequency offset estimator is also included in the ADPLL to enhance the performance. The TMS320 C6711 DSK module with the A/D converter circuit was used to build up a fundamental hardware architecture. The QPSK modulator/demodulator with ADPLL will be realized by software on DSP. And we use TI C6X assembly language and C language to complement the system programs on CCS. The experiment results from ideal channel and UW channel show that all-digital underwater transceiver is practicable.

1 緒論 1
1.1 背景簡介............................ 1
2.2 研究動機與目的...................... 2
1.3 各章節內容概述...................... 4
2 水下通訊環境與全數位接收機 6
2.1 水下環境與水下聲速.................. 6
2.2 水下聲波通道........................ 8
2.2.1 背景雜訊與有限頻寬............ 8
2.2.2 多重路徑與都卜勒效應.......... 9
2.3 全數位接收機........................10
3 QPSK水下同調通訊系統 12
3.1 水下通訊系統........................12
3.2 QPSK調變解調技術....................14
3.2.1 QPSK..........................14
3.2.2 QPSK調變/解調器...............16
3.3 全數位鎖相迴路......................19
4 全數位水下收發機之實現 24
4.1 簡介................................24
4.2 TI C6X數位訊號處理器................25
4.3 軟體實現工具 Code Composer Studio...28
4.4 數位類比轉換........................30
4.4.1 數位/類比轉換電路.............30
4.4.2 類比/數位轉換電路.............32
4.5 軟體設計............................35
4.5.1 發射端程式設計................36
4.5.2 接收端程式設計................38
4.6 全數位水下收發機....................42
5 實驗測試與結果 43
5.1 基礎發收測試........................43
5.2 水槽實驗測試........................50
6 結論與未來發展 61

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