Introduction of software-defined receivers in two-way satellite time and frequency transfer

The precision of two-way satellite time and frequency transfer (TWSTFT) is currently limited due to unstable measurement of the signal arrival time. To improve the TWSTFT precision without interrupting the main system, we introduce the software-defined receiver (SDR) to measure the arrival time of the code signal. The SDRs have been successfully installed among TL, NICT and KRISS, and time-difference results for more than 20 days were obtained and compared. From the results, the SDR has better precision and less diurnal, even when an earth station suffered from a bad condition.