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本文介绍了美国卫星直接广播系统设计的一些技术标准考虑,分析了图象及伴音质量的要求,然后根据目前家用地面站允许的天线口径及低噪声放大器在近期内可达到的水平,得出不能用一个大功率行波管转发器卫星完成对美国全国覆盖的结论。另外还讨论了降雨对系统的可用度、带宽、极化及卫星轨道位置选择的影响。本文所讨论的问题有助于了解先进的卫星直接广播系统的系统设计概念及方法。
This article describes some of the technical standards for the design of the US satellite direct broadcast system, analyzes the requirements of the image and sound quality, and then based on the current allowable antenna diameter of the household ground station and the achievable level of the LNA in the near future, Conclude the nationwide coverage of the United States with a high power TWT transponder satellite. The effects of rainfall on system availability, bandwidth, polarization and satellite orbit location selection are also discussed. The issues discussed in this article help to understand the system design concepts and methods of advanced satellite direct broadcast systems.