應用於高速網路下行鏈結之載波頻率偏移下I/Q不平衡效應盲目估算之研究

Abstract

正交頻分复用(OFDM)無線通信系統之下已經成為一個趨勢。其中最重要的組成部分是直接變換接收器(DCR)，因為它擁有體積小，價格便宜，還有耗電量低的優勢。 但DCR易受載波頻率偏移(CFO)，DC偏移(DCO)和同步/正交(I/Q)不平和所影響。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I/Q基頻處理無線接收機有令人滿意的效能，在I和Q的幅度和相位的匹配變得非常重要，而且還考慮了CFO影響。隨著無線通信的演步，新規格的演變已經越來越快。而為了新的規格，就必須需要開發一個新的演算法。本論文提出了一種不需要任何特殊的格式與任何平台皆可相容的演算法。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 10ppm 的情況。

Orthogonal frequency division multiplexing (OFDM) modulation scheme is popular in wireless communication. One of the most important components is direct-conversion receiver (DCR), because it is small, cheap and less power-consuming. DCR are vulnerable to carrier frequency offset (CFO), dc offset (DCO) and in-phase/quadrature (I/Q) imbalance. In this thesis, we focus on the topic of I/Q imbalance 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 becomes vital, and also consider the CFO effect. With the progress of wireless communication, the evolution of specification has been getting fast. New specification need to develop a new algorithm. This thesis proposes an algorithm that doesn’t need any special format and compatible with any specification. The propose schemes be able to estimate the non-ideal effect up to gain error 2 dB, and phase error 20 degree, and CFO 20 ppm in OFDM system.