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研究生： 洪紹評
Hung, Shao-Ping
論文名稱： IQ不平衡及頻率偏移效應補償
Effect Compensation of Both IQ Imbalance and Frequency-Offset
指導教授： 蘇賜麟
Su, Szu-Lin
學位類別： 碩士
Master
系所名稱： 電機資訊學院 - 電機工程學系
Department of Electrical Engineering
論文出版年： 2004
畢業學年度： 92
語文別： 英文
論文頁數： 66
中文關鍵詞： IQ不平衡 、頻率偏移
外文關鍵詞： IQ imbalance, frequency offset
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    • 　　在很多的通訊設備中，在高頻端會存在兩個重要的訊號傷害效應 ― 頻率偏移和IQ不平衡。這兩個效應通常會大大的影響通訊設備的效能。在本篇論文中，我們首先提出了利用訊號重覆特性的preamble，經計算處理後，再利用 LS 演算法去估測同時受頻率偏移影響效應下的IQ不平衡參數值。另外，我們也提出類似的方法去估測同時受IQ不平衡影響下的頻率偏移值。而提出的演算法正可以應用在 IEEE 802.11a的通訊系統，本論文即以軟體模擬來確認所提方法在802.11a環境之系統性能。

    　　There are two types of RF front-end imperfections in most communication devices, the frequency offset and the IQ imbalance, namely and respectively. The two effects can affect serious impact on performance. This study proposes a novel scheme which adopts the Least Square (LS) method to estimate the IQ imbalance when the frequency offset effect exists by using a preamble of repeated training sequence. An analogous scheme to estimate the frequency offset was also developed in this study when the IQ imbalance effect exists. These proposed schemes were applied in IEEE 802.11a standard and validated their performance by simulation.

    摘要 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .i Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ii Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .iii List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vi 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.1 IQ Mismatch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 1.2 IQ Mismatch with CFO . . . . . . . . . . . . . . . . . . . . . . . . .6 1.3 Image-Reject Receiver (Hartley and Weaver) . . . . . . . . . . . . . .6 1.4 Direct-Conversion (Zero-IF) Receiver . . . . . . . . . . . . . . . . .9 1.5 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 2 IQ Imbalance Estimation/Compensation 11 2.1 IQ Imbalance with CFO Effect . . . . . . . . . . . . . . . . . . . . .11 2.2 Existing IQ Imbalance Estimation Schemes . . . . . . . . . . . . . . .13 2.2.1 Simple Estimation Scheme in the Frequency Domain [11]. . . . . . .13 2.2.2 Adaptive Estimation Scheme in the Frequency Domain [12]. . . . . .14 2.2.3 Extra FFT Scheme in the Frequency Domain [6] . . . . . . . . . . .14 2.2.4 Based on Accurate CFO in the Time Domain [7] . . . . . . . . . . .15 2.3 Proposed Solution for the IQ Imbalance with CFO Effect . . . . . . . .16 2.3.1 Proposed Method. . . . . . . . . . . . . . . . . . . . . . . . . .17 2.3.2 Determination of alpha_r by beta_r . . . . . . . . . . . . . . . .19 2.3.3 Compensation of IQ Imbalance . . . . . . . . . . . . . . . . . . .20 2.3.4 Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 3 System Simulation/Evaluation . . . . . . . . . . . . . . . . . . . . . . .22 3.1 The Signal Format of the IEEE 802.11a. . . . . . . . . . . . . . . . .22 3.2 Simulation Model . . . . . . . . . . . . . . . . . . . . . . . . . . .23 3.3 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . .23 3.4 Possible Modifications of the Proposed Method. . . . . . . . . . . . .31 3.5 Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 4 Estimation of IQ Imbalance by Self-test .. . . . . . . . . . . . . . . . .38 4.1 Self-test of the Receiver. . . . . . . . . . . . . . . . . . . . . . .38 4.2 Post-compensation of the Receiver. . . . . . . . . . . . . . . . . . .41 4.3 Self-test of the Receiver. . . . . . . . . . . . . . . . . . . . . . .42 4.4 Pre-compensation of the Transmitter. . . . . . . . . . . . . . . . . .45 4.5 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . .45 5 CFO Estimation with the unknown IQ . . . . . . . . . . . . . . . . . . . .47 5.1 CFO Estimation without IQ Effect . . . . . . . . . . . . . . . . . . .47 5.2 Proposed CFO Estimation Scheme with IQ Imbalance Effect. . . . . . . .48 5.3 Performance Simulation . . . . . . . . . . . . . . . . . . . . . . . .51 5.4 Possible Modifications of the Proposed Method. . . . . . . . . . . . .57 5.5 Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63 6 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

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