Telecommunication Laboratories, Chunghwa Telecom Co. Ltd., Taoyuan, Taiwan, R.O.C.
IEEE Trans Ultrason Ferroelectr Freq Control. 2012 Mar;59(3):531-8. doi: 10.1109/TUFFC.2012.2224.
Two-way satellite time and frequency transfer (TWSTFT) is one of the main techniques used to compare atomic time scales over long distances. To both improve the precision of TWSTFT and decrease the satellite link fee, a new software-defined modem with dual pseudo-random noise (DPN) codes has been developed. In this paper, we demonstrate the first international DPN-based TWSTFT experiment over a period of 6 months. The results of DPN exhibit excellent performance, which is competitive with the Global Positioning System (GPS) precise point positioning (PPP) technique in the short-term and consistent with the conventional TWSTFT in the long-term. Time deviations of less than 75 ps are achieved for averaging times from 1 s to 1 d. Moreover, the DPN data has less diurnal variation than that of the conventional TWSTFT. Because the DPN-based system has advantages of higher precision and lower bandwidth cost, it is one of the most promising methods to improve international time-transfer links.
双向卫星时频传递（TWSTFT）是远距离比较原子时标主要技术之一。为了提高 TWSTFT 的精度和降低卫星链路费用，开发了一种具有双伪随机噪声（DPN）码的新型软件定义调制解调器。本文首次展示了为期 6 个月的基于 DPN 的 TWSTFT 国际实验。DPN 的结果表现出优异的性能，在短期与全球定位系统（GPS）精密单点定位（PPP）技术相当，在长期与传统 TWSTFT 一致。在 1 秒到 1 天的平均时间内，达到了小于 75 皮秒的时间偏差。此外，DPN 数据的日变化小于传统 TWSTFT。由于基于 DPN 的系统具有更高精度和更低带宽成本的优势，因此它是改善国际时频传递链路最有前途的方法之一。
