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研究生： 郭宜遠
I-Yuan Kuo
論文名稱： 正交分頻多工接收機中數位降頻器之低通濾波器設計
Design of Lowpass Filter for Digital Down Converter in OFDM Receiver
指導教授： 陳逸民
Yih-Min Chen
口試委員:
學位類別： 碩士
Master
系所名稱： 資訊電機學院 - 通訊工程學系
Department of Communication Engineering
畢業學年度： 93
語文別： 中文
論文頁數： 90
中文關鍵詞： 濾波器設計 、數位降頻器 、正交分頻多工
外文關鍵詞： Filter Design, Digital Down Converter, OFDM
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    • 正交分頻多工(OFDM)之所以成為一熱門數位寬頻無線通訊技術，主要是由於其容易對抗高度分散傳輸的特性，而實現正交分頻多工接收機可行的方法是需要倚靠全方位的數位科技技術。
    在這篇論文，我們討論的是關於高效能的低通濾波器設計之議題，此濾波器特別針對正交分頻多工接收機中的數位降頻器而設計，而接收機的輸入端為數位中頻訊號。數位降頻器中的低通濾波器所肩任的功能是同時抑制因降取(decimation)所產生的交迭頻帶內(aliasing bands)之鏡像訊號與雜訊，而鏡像訊號是因移頻(frequency mixing)所產生。由此新提出的基準所設計的低通濾波器與傳統規格的濾波器相比較，可得到效能上的增益趨勢。

    Orthogonal frequency-division multiplexing (OFDM) is a favored technique in digital broad-band wireless communications due to its easiness to combat highly dispersive transmission. The feasible implementation of an OFDM receiver relies on fully digital technique.
    In this thesis, we discuss the issue regarding to the design of an efficient lowpass filter specifically for the digital down converter (DDC) in OFDM receivers with digital intermediate frequency (IF) input. The lowpass filter in the DDC possesses the function to suppress both the image band signal due to frequency mixing and the noise residing in aliasing bands resulted from decimation. The lowpass filter designed with a newly proposed criterion exhibits performance improvement comparing to those designed with traditional specification.

    目錄 中文摘要………………………………………………………………I 英文摘要………………………………………………………………II 誌謝……………………………………………………………………III 圖目錄………………………………………………………………VI 表目錄………………………………………………………………XI 第一章 正交分頻多工系統之簡介……………………………………1 1.1 多載波調變……………………………………………………………1 1.2 正交分頻多工系統……………………………………………………3 1.3 正交分頻多工系統之優缺點…………………………………………6 1.4 正交分頻多工系統與單載波調變之比較……………………………7 第二章 正交分頻多工系統之應用……………………………………9 2.1 地面數位視訊廣播系統簡介…………………………………………9 2.2 通道編碼與訊號調變…………………………………………………10 2.3 訊框結構………………………………………………………………12 2.4 參考訊號………………………………………………………………14 2.4.1 散射領航訊號………………………………………………………15 2.4.2 連續領航訊號………………………………………………………16 2.4.3 傳輸參數訊號………………………………………………………17 第三章 正交分頻多工接收機之數位降頻器………………………19 3.1 數位正交分頻多工接收機………………………………………20 3.2 數位降頻器………………………………………………………23 3.3 數位降頻器中低通濾波器之設計………………………………30 3.3.1 數位濾波器類型……………………………………………………32 3.3.2 數位濾波器設計基準………………………………………………37 3.4 低通濾波器之設計流程與設計實例……………………………39 3.4.1 設計流程……………………………………………………………40 3.4.2 設計實例……………………………………………………………41 第四章 電腦模擬與分析結果………………………………………44 4.1 效能衰減分析……………………………………………………46 4.1.1 阻帶容限……………………………………………………………48 4.1.2 阻帶截止頻率………………………………………………………50 4.2 系統模擬…………………………………………………………52 4.2.1 阻帶容限……………………………………………………………53 4.2.2 阻帶截止頻率………………………………………………………53 4.3 傳統濾波器之改善流程與效能比較……………………………54 4.3.1 濾波器改善流程……………………………………………………54 4.3.2 改善前後之效能比較………………………………………………57 4.4 濾波器之量化…………………………………………………………59 第五章 結論……………………………………………………60 參考文獻………………………………………………………………90

    參考文獻
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