跳到主要內容

臺灣博碩士論文加值系統

(3.236.28.137) 您好!臺灣時間:2021/07/25 21:04
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果 :::

詳目顯示

: 
twitterline
研究生:宋光玉
研究生(外文):Kuang-yu Sung
論文名稱:正交頻域多工系統中I/Q失衡之估測及補償
論文名稱(外文):Estimation and Compensation of I/Q Imbalance in OFDM Systems
指導教授:趙啟超趙啟超引用關係
指導教授(外文):Chi-chao Chao
學位類別:碩士
校院名稱:國立清華大學
系所名稱:通訊工程研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2004
畢業學年度:92
語文別:英文
論文頁數:111
中文關鍵詞:I/Q失衡I/Q失衡補償正交頻域多工通道估測多路徑通道可加性白色高斯雜訊最大可能性估測法最小平方估測法
外文關鍵詞:I/Q imbalanceI/Q imbalance compensationorthogonal frequency division multiplexingOFDMchannel estimationmultipath channeladditive white Gaussian noiseAWGNmaximum likelihood estimationleast square estimation
相關次數:
  • 被引用被引用:0
  • 點閱點閱:134
  • 評分評分:
  • 下載下載:19
  • 收藏至我的研究室書目清單書目收藏:0
正交頻域多工 (orthogonal frequency division multiplexing,簡稱OFDM) 近年來是一個非常熱門的研究主題且有很廣泛的應用。在正交分頻多工系統中,接收器的射頻模組採用直接轉換架構,則是近年來流行採用的方式。直接轉換架構的好處在於成本較低且功率消耗較少,但是其最主要的缺點是會造成I/Q失衡。在本篇論文中,我們針對OFDM系統中採用直接轉換接收器所產生的I/Q失衡現象加以估測並補償。在先前提出的I/Q失衡補償方法中大部分都未考慮未知的多路徑通道 (multipath channel),在這篇論文中,我們考慮有可加性白色高斯雜訊 (additive white Gaussian noise,簡稱AWGN) 的多路徑衰減通道,而這個通道在一個封包(packet)之內是不變的。我們提出了三種I/Q失衡的補償方法:最大可能性估測法、最小平方估測法、直覺式估測法。我們透過電腦模擬來比較這三種方法的表現,並考慮時序偏移 (timing offset) 及頻率偏移 (frequency offset) 的影響。模擬結果顯示盲蔽最大可能性估測法有很好的表現,並且對時序偏移及頻率偏移有很好的抵抗能力。最小平方估測法及直覺式估測法在訊號對雜訊的比值 (signal-to-noise ratio,簡稱SNR) 較高時有較好的表現,對時序偏移也有很好的抵抗能力,但是在頻率偏移存在的條件下表示會較差。且在不同的振幅不平衡 (gain imbalance) 及相位不平衡 (phase imbalance) 的情況下,我們提出的盲蔽最大可能性估測法、最小平方估測法及直覺式估測法都有很好的表現。
Orthogonal frequency division multiplexing (OFDM) is a popular research topic and has been employed in various applications in recent years. In OFDM systems, it is attractive to employ the direct conversion architecture in the radio frequency module of the receivers for the propose of low cost and low power consumption. But the main problem caused by using the direct conversion architecture is I/Q imbalance. In this thesis, we estimate and compensate the I/Q imbalance generated by the direct conversion receiver in OFDM systems. In previously proposed methods for I/Q imbalance compensation, the unknown multipath channel is usually not considered. In this thesis, the channels are considered to be multipath fading channels with additive white Gaussian noise (AWGN), and the channels are assumed quasi-static during an entire packet. Three methods for I/Q imbalance compensation are proposed: the maximum-likelihood (ML) estimation method, the least-square (LS) estimation method, and a heuristic method. Computer simulations are conducted for comparisons of the performance of three methods. Timing offset and frequency offset effects on performance are also considered. We find that the blind ML estimation method generally performs well and is robust against timing offset and frequency offset.
Abstract i
Contents ii
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Organization of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Overview of the I/Q Imbalance Problem in OFDM Systems 3
3 Review of Previous I/Q Imbalance Compensation Methods 5
3.1 I/Q Imbalance Compensation Methods without Training Signals . . . . . . . 5
3.2 I/Q Imbalance Compensation Methods with Training Signals . . . . . . . . . 10
4 I/Q Imbalance Models in OFDM Systems 15
4.1 OFDM Signaling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 OFDM Transceiver Architecture with I/Q Imbalance . . . . . . . . . . . . . 16
4.3 I/Q Imbalance Models Discussion . . . . . . . . . . . . . . . . . . . . . . . . 17
4.3.1 I/Q Imbalance Model I . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.3.2 I/Q Imbalance Model II . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.4 I/Q Imbalance Models in the Frequency Domain . . . . . . . . . . . . . . . . 25
4.5 Channel Model and Channel Discussion . . . . . . . . . . . . . . . . . . . . . 26
5 Proposed Methods for Estimation and Compensation of I/Q Imbalance 31
5.1 I/Q Imbalance Compensation Using Maximum-
Likelihood Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1.1 Channel Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.1.2 I/Q Imbalance Estimation and Compensation . . . . . . . . . . . . . 50
5.2 I/Q Imbalance Compensation Using Least-Square Estimation . . . . . . . . . 61
5.2.1 Channel Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5.2.2 I/Q Imbalance Estimation and Compensation . . . . . . . . . . . . . 73
5.3 Heuristic I/Q Imbalance Compensation . . . . . . . . . . . . . . . . . . . . . 77
5.3.1 Channel Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.3.2 I/Q Imbalance Estimation and Compensation . . . . . . . . . . . . . 84
6 Simulation Results 86
6.1 Generation of AWGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.2 Generation of Multipath Channel Model . . . . . . . . . . . . . . . . . . . . 88
6.3 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
7 Conclusion 108
Bibliography 110
[1] R. van Nee and R. Prasad, OFDM for Wireless Multimedia Communications. Boston: Artech House, 2000.
[2] B. Razavi, RF Microelectronics. Upper Saddle River, NJ: Prentice Hall, 1998.
[3] B. Razavi, Design considerations for direct-conversion receivers," IEEE Trans. Circuits and Systems II: Analog and Digital Signal Processing, vol. 44, pp. 428-435, June 1997.
[4] M. Valkama and M. Renfors, Advanced DSP for I/Q Imbalance Compensation in a Low-IF Receiver," in Proc. IEEE Int. Conf. Commun., New Orleans, LA, USA, June 2000, pp. 768-772.
[5] M. Valkama, M. Renfors, and V. Koivunen, On the performance of interference canceller based I/Q imbalance compensation," in Proc. IEEE Int. Conf. Acoustics, Speech,
and Signal Processing, Istanbul, Turkey, June 2000, pp. 2885-2888.
[6] S. Fouladifard and H. Shafiee, On adaptive cancellation of IQ mismatch in OFDM receivers," in Proc. IEEE Int. Conf. Acoustics, Speech, and Signal Processing, Hong Kong, China, Apr. 2003, pp. IV-564-567.
[7] H. Q. Mu and Y. N. Peng, An approach to the correction of I and Q imbalance in time domain," in Proc. IEEE/CIE Int. Conf. Signal Processing, Beijing, China, Oct. 2001,
pp. 1006-1010.
[8] J. P. F. Glas, Digital I/Q Imbalance Compensation in a Low-IF Receiver," in Proc. IEEE Globecom, Sydney, Australia, Nov. 1998, pp. 1461-1466.
[9] IEEE 802.11, Supplement to IEEE standard for information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN medium access control (MAC) and physical layer (PHY) specifications: High-speed physical layer in the 5 GHz band," Sept. 1999.
[10] A. V. Oppenheim and R. W. Schafer, Discrete-Time Signal Processing 2nd ed., Englewood Cliffs, NJ: Prentice Hall, 1999.
[11] P. M. Clarkson, Optimal and Adaptive Signal Processing. London: CRC Press, 1993.
[12] H. Stark and J. W. Woods, Probability and Random Processes with Applications to Signal Processing. Upper Saddle River, NJ: Prentice Hall, 2002.
[13] H. P. William, A. T. Saul, T. V. William, and P. F. Brian, Numerical Recipes in C: The Art of Scientific Computing. New York: Cambridge University Press, 1992.
[14] B. O'Hara and A. Petrick, The IEEE 802.11 Handbook: A Designer's Companion. New York: IEEE Press, 1999.
QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top
無相關期刊