針對WLAN OFDM系統之I/Q不平衡與載波頻率偏移補償與其電路設計與實現

Design and Implementation of Joint IQ Imbalance and Carrier Frequency Offset Compensation for WLAN OFDM Systems

劉瀚升(Han-sheng Liu)

指導教授 ： 張大中

國立中央大學/資訊電機學院/通訊工程學系/碩士(2011年)

摘要

正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM) 技術，已經廣泛使用於現代的無線網路實體層中，在射頻電路的架構方面，直接轉換接收機(Direct-conversion) 也越來越受到廣泛的使用，因其具備低成本與小面積等優點。伴隨著此結構容易受到射頻元件與震盪電路的誤差帶來IQ 不平衡(IQ Imbalance)、直流偏移(DC Offset) 與載波頻率偏移(Carrier Frequency Offset) 等問題，降低接收機性能。因此在本篇論文，提出了使用訓練符元以最小平方(Least square) 做參數估計，達到在無線區域
網路系統中快速同步的目的，並且較現有演算法有更好的效能。最後，基於我們的演算法提出同步電路架構，並以VHDL 撰寫RTL 驗證我們的電路結構效能。

關鍵字

直接轉換接收器 ； 正交分頻多工系統 ； IQ不平衡 ； 載波頻率偏移

並列摘要

Orthogonal Frequency Division Multiplexing (OFDM) is a widely used technique in the physical layer of modern communication system. Unfortunately,OFDM system is sensitive to imperfect synchronization and non-ideal front-end effects such as IQ Imbalance, DC Offset and carrier frequency offset, leading to serve system performance degradation. In this thesis, we consider recovering the WLAN OFDM signals in the presence of these imperfect conditions, we propose least-square (LS) equalization for Joint IQ Imbalance and carrier frequency offset estimation. From computer simulation results, the proposed algorithm has better performance than existing algorithms. Finally, the VHDL Design is used to verity the feasibility in electric circuit structure.

並列關鍵字

OFDM ； IQ Imbalance ； IQ Mismatch ； Carrier frequency offset ； Direct Conversion

參考文獻

[2] S.-L. Su and Y.-J. Chiu, “Adaptive iq imbalance compensation scheme with frequency offset for communication channel,” in 2006. CCNC 2006. 3rd IEEE Consumer Communications and Networking Conference,, vol. 2, Jan. 2006, pp. 1038 –1042.

[3] Y.-J. Chiu and S.-P. Hung, “Estimation scheme of the receiver iq imbalance under carrier frequency offset in communication system,”IET Communications, vol. 4, no. 11, pp. 1381 –1388, 23 2010.

[4] J.-R. Liang and C.-H. Kuo, “Ls-based joint estimation of carrier frequency offset and iq imbalance in ofdm systems,”in 2010 International Symposium on Next-Generation Electronics (ISNE), Nov.2010, pp. 52 –55.

[6] L. Lanante, M. Kurosaki, and H. Ochi, “A new joint estimation scheme for carrier frequency offset and i/q imbalance,”in IEEE International Conference on Communications, 2009. ICC ''09., June 2009, pp. 1 –5.

[7] G.-T. Gil, I.-H. Sohn, J.-K. Park, and Y. Lee, “Joint ml estimation of carrier frequency, channel, i/q mismatch, and dc offset in communication receivers,”IEEE Transactions on Vehicular Technology,vol. 54, no. 1, pp. 338 –349, Jan. 2005.