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dual tone multiple-frequency
双音多频

the satellites rely on multiple frequency data positioning system satellites (gnss) so they are precisely defined and harmonized with the international terrestrial reference system (itrs).
这些站点依赖多频率数据定位系统卫星（全球导航卫星系统），因此界定精确，并与国际地面参照基准相一致。

gnss consists of constellations of satellites that provide continuously optimized location and time information, transmitting a variety of signals on multiple frequencies available at all locations on earth.
13. 导航卫星系统由各种卫星星座组成，持续提供定位和定时最优信息，传送有关地球上各个地点所可提供的多种频率的各类信号。

4. gnss consist of constellations of satellites that provide continuously optimized location and time information, transmitting a variety of signals on multiple frequencies that are available worldwide.
4. 导航卫星系统由不间断提供优化位置和时间信息的卫星星座组成，以全世界可用的多个频率发送多种信号。

coordination difficulties and system economy compelled satellite systems to use more spectrum-efficient transmission techniques, multiple frequency re-use, more sophisticated antennas, new frequency bands and, if possible, more interference- resistant transmissions.
协调的困难和系统经济问题的存在，迫使卫星系统采用更有效利用频谱的传送技术，多重频率反复使用、更尖端的天线、新频带和在可能情况下采用更抗干扰的传送。

the 30-year trend in fixed satellite service (fss) had been one in which communication satellites were becoming more powerful, were three-axis stabilized, and were using higher-gain and larger-aperture antennas operating with multi-beams to achieve multiple frequency re-use.
30年来发展固定卫星服务的趋势，是通信卫星功率越来越强大、呈三轴固定、采用高增益、大孔径天线操作并以多波束确保多重频率的反复使用的趋势。