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Use of SDR Receivers in TWSTFT for UTC Computation

Published

Author(s)

Zhiheng Jiang, Victor S. Zhang, Yi-Jiun Huang, Joseph Achkar, Dirk Piester, Shinn-Yan Lin, Wenjun Wu, Sung-hoon Yang, Jerzy Nawrocki, Ilaria Sesia, Christian Schlunegger, Zhiqiang Yang, Miho Fujieda, Albin Czubla, Hector Esteban, Carsten Rieck, Peter Whibberley

Abstract

Two-Way Satellite Time and Frequency Transfer (TWSTFT) is a primary technique for the generation of Coordinated Universal Time (UTC). About 20 timing laboratories around the world continuously operate TWSTFT using the SAtellite Time and Ranging Equipment (SATRE+) modems for remote time and frequency comparisons and for the generation of UTC. The precision of the SATRE TWSTFT is limited by an apparent daily variation pattern (diurnal) in the TWSTFT results. The observed peak-to-peak variation could be as high as 2 ns in some cases. Investigations of the origin of the diurnals provided no clear understanding about the dominant cause of the diurnals so far. But in 2014 and 2015, it was demonstrated that the use of Software-Defined Radio (SDR) receivers in TWSTFT ground stations (SDR TWSTFT) could considerably reduce the diurnals and also the measurement noise. In 2016, the International Bureau of Weights and Measures (BIPM) and the Consultative Committee for Time and Frequency (CCTF) Working Group (WG) on TWSTFT launched a pilot study on the application of SDR receivers in the TWSTFT network for UTC computation. The first results of the pilot study have been reported to the CCTF WG on TWSTFT annual meeting in May 2017. It is concluded that SDR TWSTFT show superior or at least similar performance compared to the performance of SATRE TWSTFT for all links. In particular, for continental TWSTFT links in which strongest diurnals appear, the use of SDR TWSTFT results in a significant gain in reducing the diurnals by a factor between two and three; for the very long inter- continental links, e.g. the Europe to USA links where the diurnals affect less, SDR TWSTFT achieved a smaller but still significant gain of 35%. These findings are supported by a comparison to the GPS IPPP technique reported in this article. Based on these results, the WG on TWSTFT prepared a recommendation for the 21st CCTF meeting. The recommendation suggested the introduction...
Citation
Metrologia

Keywords

Diurnal, SDR, Time Transfer, TWSTFT, Uncertainty, UTC
Created August 2, 2018, Updated October 6, 2020