Development Of A Ku Band Satellite Simulator For TWSTFT Applications

LNE-SYRTE has developed a satellite simulator for the monitoring of the delay difference of its earth station used for the two-way satellite time and frequency transfer (TWSTFT) applications. Such a device is more and more recommended by the CCTF working group on TWSTFT in order to better evaluate the time transfer uncertainty component related to the variation of the earth station delay difference between two calibration campaigns with a portable station. Besides few simulators commercially available based on the VSL design (G. De Jong, 1998), our laboratory has realized a new calibration device with at least two different concepts from those currently in use: a faster delay calibration process and a characterization of its internal delays using a microwave vector network analyzer (MVNA). The key component of this simulator is the use of a double-balanced microwave mixer and its characterization in terms of absolute delay requiring a specific measurement system such as an MVNA allowing a vector mixer calibration technique using a characterized mixer/filter as a through standard. The measurements done with the MVNA completed by those giving with the SATRE modem during calibration sessions, involving the earth station -which is driven by UTC(OP)-and the satellite simulator, are described in this paper. Moreover, the study of the time stability of the whole system including the earth station and the simulator shows a time deviation below 20 ps at 1 s, giving an excellent measurement noise. For the long term, a time deviation below 50 ps is reached between 0,3 d and 3 d averaging time (P. Merck and J. Achkar, 2006). The next step is the implementation of the simulator into measurement regular sessions permitting the computation and the monitoring of the earth station differential delay as well as the study of the time stability over one year period.