改善相位同調盲蔽等化器收斂效果之研究

Abstract

在現代的無線通訊系統中，由於通訊環境相當複雜，造成多重路徑干擾的 現象，影響通訊的品質。為了提高通訊的效能，吾人常利用盲蔽等化器來 克服多重路徑干擾對系統的影響。在本論文中，吾人探討盲蔽等化方法的 收歛情形及其改良的方法。對於相位同調盲蔽等化方法，通道輸出訊號的 相關矩陣的特徵值分佈嚴重地遲緩了等化器的收歛速率。為了改善其效能 ，吾人提出應用自我正交法及格狀濾波器來提高系統的收斂速率。此外， 為了克服非理想解調所引發的相位誤差對收歛速率的影響，吾人提出方法 來補償固定的相位誤差。吾人亦推導出配合相位同調盲蔽等化使用的載波 再生方法，以追蹤時變的相位擾動。最後，吾人以電腦模擬的結果來驗證 以上所提出的方法確實有效。 In this thesis, we discuss the convergence properties of a previously developed blind equalization algorithm and propose methods for improving its performance. In blind equalization, the rate of convergence depends heavily on the eigenvalue spread of the data correlation matrix. A natural way of speeding up the convergence would then be to orthogonalize the correlation structure, which may be achieved by applying the self orthogonalizing algorithm and lattice filter structure. On the other hand, in order to alleviate the effect of phase errors on the convergence of the proposed equalizer, we proposed supervised and unsupervised methods for detecting fixed phase errors resulting from channel disturbance. We also derived a carrier recovery algorithm for tracking time varying phase jitters. The efficacy of the proposed methods are demonstrated by simulation results.