應用於無線多輸入多輸出基頻處理器之載波頻率偏移下IQ不平衡效應之研究

Abstract

直接降頻的接收器(DCR)架構目前在工業和學術界已經成為一個趨勢，因為它擁有體積小，便宜和消耗更少動力的優勢。但是，這種架構會一起伴隨著一些射頻(RF)的不完美效應，像是直流電(DC)偏移，頻率偏移，以及I/Q不平衡效應等等…在這篇論文中，主要是研究在有載波頻率偏移和I/Q不平衡之效應。 為了使無線接收器上的類比I/Q處理器得到令人滿意的效能，實部和虛部的匹配變得至關重要，且對於載波頻率偏移的影響也很敏感。此論文提出一個新穎的基頻處理方，在MIMO-OFDM系統，來估計和補償在有大的載波頻率偏移下之I/Q不平衡效應。並且，為了可以在大的載波頻率偏移以及嚴重的震幅和相位誤差下，可以使P-CFO的演算法可以實踐，提出一個新的估測和補償流程，結合P-CFO和I/Q不平衡的方法，使得整體系統效能獲得改善。再加上改善的相位恢復方法，更讓整體系統效能大幅的提升。它能容忍的範圍包含了震幅誤差2dB，相位誤差20 度，以及載波頻率偏移為150ppm的情況。

A direct-conversion receiver architecture becomes a trend in industry and academic world nowadays because it is small, cheap and less power-consuming. This kind of architecture, however, accompanies with some radio frequency (RF) imperfections such as the direct current (DC) offset, frequency offset, in-phase/quadrature (I/Q) mismatch, and etc. In this thesis, it focuses on the topic of the RF impairment of I/Q mismatch and CFO. To achieve satisfactory performance in analog I/Q processing based wireless receivers, the matching of amplitudes and phases of the I and Q branches becomes vital, and also consider the CFO effect. In this thesis, a novel baseband I/Q mismatch estimation and compensate technique is proposed to overcome I/Q mismatch with large CFO in MIMO-OFDM systems. Moreover, depend on [11] to combine the P-CFO method and the proposed I/Q-M scheme. To make these algorithms can work under large CFO and I/Q-M, proposed a flow and the improved phase recovery scheme to improve the whole system performance. The proposed schemes be able to estimate and compensate the non-ideal effect up to gain error 2dB, phase error 20 degree, and CFO 150ppm in MIMO-OFDM systems.