Dual-Frequency ISB Estimation and Stability Analysis of BDS/GPS

The single-frequency ISB of BDS/GPS is affected by factors such as ionosphere model error and satellite hardware delay. It is difficult to assess accurately and effectively. In this study, the dual-frequency ISB function model of BDS/GPS is derived based on dual-frequency ionosphere-free combination. This method can more accurately determine the time system deviation and hardware delay deviation in receiver. To further analyze the influencing factors and investigate the relation of different receivers (firmware version) and antenna to ISB, 36 MGEX stations' observation data in 2017 are selected. BDS/GPS ISBs series calculated from JAVAD, LEICA, SEPT and TRIMBLE four brand receivers and antennas are analysed in short-term (epoch, day) and long-term (year) time scales. The results show that the ISB variation of diverse brands receiver. In the short-term, the ISB of the above four brand receivers are 40-50 ns, 80-110 ns, 70 ns and 70 ns, respectively. All of above ISBs have periodic time-varying characteristics. The ISB time series of each brand receivers have a consistent but unstable trend in the long-term, and not affected by seasonal factors.