GA VSB HDTV 地面傳輸系統之模擬

Abstract

基於實驗室內的測試結果, 8-VSB系統已被美國的Grand Alliance (GA)選 為高畫質電視(HDTV)地面廣播的方法. 此系統亦已被FCC Advisory Committee on Advanced Television(ACATS)所核准, 預備用來取代已使 用了五十年的NTSC系統．將資料速率超過20Mb/sec的HDTV信號透過一遭受 多路徑傳輸(multipath propagation), 各種雜訊, 以及NTSC同頻道干擾 (cochannel interference)等破壞的頻寬6MHz的頻道來傳送的確是數位通 訊上的一大挑戰.本論文以電腦來模擬此一系統在實際傳輸環境中之表現, 藉以評估其在將來HDTV地面廣播應用上的可行性. 模擬著重在通道等化 器 (channel equalizr), 相位追蹤迴路(phase tracking loop), NTSC干 擾除濾波器(NTSC rejection filter), 以及通道編碼. On the basis of laboratory testing, the 8-VSB transmission system was selected as the vehicle for the terrestrial transmission of the high definition television (HDTV) by the Grand Alliance USA. This system has been approved by the FCC Advisory Committee on Advanced Television Service (ACATS),and is intended to replace the fifty years old NTSC system now in use. To squeeze the HDTV signal at rate over 20Mb/s into a 6MHz bandwidth channel which suffers from multipath propagation, noises, and NTSC cochannel interference, is really a challenge of digital transmission. To investigate the suitability of this system under real world condition of propagation, we simulate the various components of this system. Emphases are placed on channel equalizer, phase tracking loop, NTSC rejection filter, and channel coding.