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1 数字化传输及数字信号的形成 在信息日益产业化的今天,数字传输作为一种新的通信手段,正以它独特的优势越来越为人们所重视。FDM—FM系统构成全球通信网时,模拟信号传输中固有噪声积累的缺点越来越突出。通信距离越长,所需转接的次数就越多,沿站噪声积累就越大。将模拟信号转化为数字信号再传输可有效的消除噪声积累,同时易于进行各种复杂处理,便于存储,易集成化等。但数字信号(特别是电视信号)数码率太高,不易直接进行传输。因此,在传输前要进行多种处理,这些处理包括了提高传输效
A digital transmission and the formation of digital signals Today, the information increasingly industrialized, digital transmission as a new means of communication, is its unique advantages more and more attention. When the FDM-FM system constitutes a global communication network, the drawbacks of the inherent noise accumulation in analog signal transmission become more and more prominent. The longer the communication distance, the more the number of handovers required and the greater the noise accumulation along the station. The analog signal into a digital signal and then re-transmission can effectively eliminate the noise accumulation, and easy to carry out a variety of complex processing, easy to store, easy integration. However, the digital signal (especially the television signal) digital rate is too high, not easy to direct transmission. Therefore, a variety of processing is performed before transmission, and these processes include improvement of transmission efficiency