正交分頻多工器(Orthogonal Frequency Division Multiplexing，OFDM)
是一種現今用在無線通訊系統的高速率傳輸技術，在此高速數傳輸通訊系統下，一些普遍的通訊傳輸問題例如同相通道 (I channel) 以及正交通道 (Q channel) 間的振幅不平衡及相位間的失調 (IQ imbalance)在此環境中也伴隨著而生。而為了去移除這些可能由一些通訊傳收所使用元件而造成的效應，我們必須採取一些必要且緊急的補償方案來解決這些會嚴重影響整個通訊系統的效應。
在現存的研究中，有非常多對於此效應的補償方法被建議，但是考慮到對整個系統的效益以及簡單的程序，在我們所提出的架構我們採取時間領域最小平均方差 (Least-Mean-Squared) 的補償方法來為我們所採用。且與一般的單一天線傳送單一天線接收 (Single-Input Single-Output，SISO) 的通訊系統比較，目前所熱門研究的多天線傳送多天線接收 (Multiple-Input Multiple-Output，MIMO) 具有更多的優勢在下一世代的無線通訊應用上。因此，在本論文我們所提出的架構中，我們使用時間領域最小平均方差的方法來補償同相通道以及正交通道間的振幅不平衡及相位的不平衡，並且我們把架構由原本的單一天線傳送單一天線接收系統延伸至單天線傳送雙天線接收 (Single-Input Multiple-Output)的多天線傳輸系統並且結合最大比例結合 (Maximun-Ratio-Combine) 的方法來完成我們的系統。最後，我們也經由一些對我們所提出的架構來做一些模擬，藉由此模擬驗證我們所採用的理論架構是否對於此問題有了明顯的改進。
索引-正交分頻多工，多天線輸入多天線輸出，時間領域最小平均方差，最大比例結合，同相/正交通道間的不平衡。

Orthogonal Frequency Division Multiplexing (OFDM) is a high data-rate communica-
tion system. In this high data-rate communication system, a popular problem such as IQ imbalance occurs in this system front-end. In order to remove the e®ect caused by such circuit components, we need to take some compensation schemes urgently. There have been many compensation schemes proposed, by better performance and a simple technique, we take the time-domain LMS compensation scheme into account.
Comparing with the single-input single-output (SISO) OFDM system, multiple-input multiple-output (MIMO) OFDM system has great advantages and take more concerns applying in next communication generation. In our thesis, we take the time-domain LMS compensation scheme combing with the MRC algorithm for our simulation which include one transmitted antenna and two received antennas. Simulation will show great improvement dealing with the IQ imbalance for time-domain LMS compensation scheme and a great promotion for MIMO OFDM system to SISO OFDM system.
Index-OFDM,MIMO, time-domain LMS, MRC, IQ imbalance.

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