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如果能将比特率减到34Mbit/s(对于480路PCM系统来说,比特率则应减至34.368Mbit/s),那么,采用数字调制方法的电视卫星传输则在卫星传输功率和传输带宽方面呈现出优越性。本文叙述了一种非常高效的编码技术,即差分脉码调制(DPCM)技术,并说明了这种编码技术在电视传输中的应用。本文还详述了一种测试系统,这一测试系统用来说明数字电视传输是切实可行的。在这一测试系统中,将复合电视信号分离为亮度和色度分量。在将4-PSK(相移键控法)的调制解调器作为接口的情况下,已经实现了定向无线电和卫星线路测试。经DPCM编码后,这些图象信号和伴音信号多工复用,并且连同同步码字一起发射。在接收端,将此信号分离和解码后,就得到模拟信号。本文给出一幅实际的数字传输图象,以说明业已得到很好的图象质量。
If the bit rate can be reduced to 34Mbit / s (480bit PCM system, the bit rate should be reduced to 34.368Mbit / s), then the use of digital modulation method of satellite television transmission in terms of satellite transmission power and transmission bandwidth Showing superiority. This paper describes a very efficient encoding technique, namely Differential Pulse Code Modulation (DPCM) technology, and illustrates the application of this encoding technique in television transmission. This article also details a test system that is used to demonstrate that digital television transmission is viable. In this test system, the composite television signal is separated into luminance and chrominance components. In the case of a 4-PSK (Phase Shift Keying) modem as an interface, directional radio and satellite line testing have been implemented. After DPCM encoding, these video and audio signals are multiplexed and transmitted together with the synchronization codeword. At the receiving end, this signal is separated and decoded to obtain an analog signal. This article presents an actual digital transmission image to illustrate that good image quality has been achieved.