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.