Abstract:We calculate the inter-frequency clock bias(IFCB) of BDS-2 and BDS-3 GEO satellites, and analyze the variation characteristics. The results show that the corresponding phase and pseudo-range IFCB of BDS-2 GEO satellite have obvious time variability and periodicity, while the corresponding phase and pseudo-range IFCB of BDS-3 GEO satellite have no obvious time variability. We analyze the periodic variation characteristics of BDS-2 single-day IFCB, and construct the IFCB modeling function using the period obtained from the analysis. We use the polynomial and mixing harmonic function to model IFCB respectively, and the modeling results are as follows: the average RMS of the mixing function model corresponding to the 4th order harmonic function is 0.003 6 m in phase IFCB fitting, and the corresponding RMS of pseudo-range IFCB is 0.131 3 m. The average RMS of the mixing function model corresponding to the 8th order harmonic function is 0.003 4 m, and the corresponding RMS of pseudo-range IFCB is 0.123 8 m. When using polynomials to model IFCB, the accuracy is improved with the increase of polynomial order, but it is still inferior to the mixing function based on harmonic function. When constants are used to replace BDS-3 phase IFCB results, the average fitting RMS is 0.000 5 m. When pseudo-ranges are used to replace IFCB results, the average fitting RMS is 0.035 2 m.