QAM 與 VSB 共用的高畫質電視數據機

Abstract

不論是經由空中或電纜, VSB 與 QAM 兩種數位調變的技術皆可以用來傳 送 HDTV 的訊號.如果能夠設計單一個接收器來合併這兩者將是更符合經 濟效益的做法. 在這篇論文中, 我們首先比較並分析 VSB 與 QAM 這兩類 訊號, 並且根據先前的研究結果指出 VSB是可以被視為 SQAM 的一種特 例, 我們提出一個類似 QAM 接收器的架構來解調 QAM 和 VSB 訊號.在設 計的過程中, 我們針對時脈回復及載波回復和頻道等化分別嘗試不同的理 論與方法.而頻道編碼設計及整個完整的系統亦在電腦模擬之中. 最後模 擬的結果顯示出這樣的一個雙功能的接收器不論對於 QAM 或 SQAM(VSB) 訊號都能正確地將其解調. Two digital modulation techniques, VSB and QAM, may be used for transmitting HDTV signals over the air and/or the cable. It wouldbe more economical if a single receiver can be designed to accommodateboth signals. In this thesis, we first compare and analyze the VSB andthe QAM signals, and then based on previousresearch results that VSBcan be viewed as SQAM, we propose a modified QAM receiver structure that can also demodulate SQAM signals. In the design process, we study, simulate and compare various algorithms for timing recovery, carrierrecovery and channel equalization. Also simulated is the channel coding schemes and the complete system. The results indicate that such a dual-function receiver works equally well for both QAM and SQAM (VSB).