Application of Vondrak Filtering Method in Software Defined Receiver (SDR)-Two-Way Satellite Time and Frequency Transfer (TWSTFT)

In March 2020, Two-Way Satellite Time and Frequency Transfer based on SDR-TWSTFT (Software Defined Receiver) link data has been used in the calculation of TAI (International Atomic Time) for the first time. Improving the reliability and stability of the link is of great significance to enhance the performance of TAI. By analyzing the performance of SDR-TWSTFT link, it is found that the results show some characteristics of random noise. In this paper, a frequency domain amplitude analysis method based on Vondrak filtering theory is proposed, which can determine the filtering factor. This method is used to process the SDR-TWSTFT link measurement data between the NTSC (National Time Service Center) of the Chinese Academy of Sciences and the PTB (Physikalisch Technische Bundesanstalt). It is found that this method can improve the reliability of the link time transfer results, and significantly improve the short-term frequency and time stability of the filtered link.