有線數位影像廣播系統中之盲蔽式等化技術

Abstract

盲蔽式等化器可以恢復在伴隨白色高斯雜訊的ISI通道的數位信號。近來恆模數演算法(constant modulus algorithm)的盲蔽式等化器演算法改善了收斂速度和穩態誤差，因此這類盲蔽式等化器更適合數位影像廣播系統。 在本篇論文中，我們考慮此種等化器在數位影像廣播系統(EN300429)中之適用性，並討論及比較數種演算法的盲蔽式等化器設計。模擬結果指出，使用SGA演算法的盲蔽式等化器可以獲得比較好的收斂速度及穩態誤差。同樣的，盲蔽式等化器使用於DAPSK調變方式也可以得到相同的收斂行為。

Blind equalizers have long been employed to recover the distorted signal over ISI channel with AWGN noise. Among the many blind algorithms, constant modulus algorithm (CMA) is the most frequently employed adaptation algorithm in blind equalizers. In this thesis, we consider the applicability of such equalizers to the EN300429 DVB system using QAM modulation technique. Specifically, the effects of several algorithms for blind equalization are discussed and compared. Computer simulation results indicate that the performances of blind equalizers using SGA algorithm, one variant of the CMA, is the best approach for improving convergence speed and reducing steady state error. Also, the blind equalizers for DPASK modulation scheme can achieve similar convergence behaviors, if it is employed in DVB systems.