A new method of time difference calibration of TWSTFT earth station based on two portable stations

The time difference calibration between stations is a hot research topic in two-way satellite time and frequency transfer (TWSTFT). According to the disadvantage of the traditional TWSTFT calibration methods using a portable station(PS) that baseband modem and RF transceiver of the portable station must be compatible with TWSTFT earth station´s, a new TWSTFT calibration method is proposed based on two TWSTFT portable stations. Two TWSTFT portable stations´ prototypes are developed. The prototypes´ system compositions are introduced and the performance of prototypes is tested. The results show that type A uncertainty of time difference calibration between stations is 0.077ns based on the zero baseline comparison. The type A uncertainty of ground station time delay of portable station 1 and 2 respectively is 0.043ns and 0.027ns. The measuring system can be applied to the satellite navigation systems and the comparisons of time and frequency among different laboratories.