正交分頻多工系統之時序偏移與I-Q失衡補償

Abstract

正交分頻多工(Orthogonal Frequency Division Multiplexing，OFDM)是一可以滿足未來高速資料傳輸需求的技術，目前已經被廣泛使用在多種應用領域。本篇論文主要針對OFDM系統的時序偏移與射頻I-Q失衡效應作深入研究，並提出新的補償方法，包含補償時序偏移的開放式相位追蹤迴路與相位內差法，以及不同環境下補償I-Q失衡的三個新方法。本研究以IEEE 802.11a OFDM WLAN為設計系統進行實際模擬，結果證明補償時序偏移後之效能損耗小於1dB，而且補償I-Q失衡之新方法效能優於傳統方法。最後，合併封包偵測、碼框同步與頻偏估算演算法，設計一符合IEEE 802.11a規範之接收機，經由模擬驗證整體效能損耗小於2dB。

Orthogonal frequency division multiplexing (OFDM) is a promising transmission technology for future high data rate communications. OFDM has been used in wide varieties of applications. In this thesis, the issues of clock offset and I-Q imbalance of OFDM systems are investigated. A novel open-loop phase-tracking with phase interpolation is proposed to counteract the effect of clock offset. In addition, three new compensation methods for I-Q imbalance that appears in the direct conversion RF frond-end are proposed. Simulations on the IEEE 802.11a OFDM WLAN system show that the implementation loss due to clock offset estimation is less than 1 dB, and the proposed new methods for I-Q imbalance compensation significantly outperform the traditional ones. Finally, a complete transceiver that complies with the IEEE 802.11a specification is designed and simulated. The overall implementation loss is less than 2 dB.