多模GNSS IFCB产品特点分析及精密单点定位性能评估

随着多模全球卫星导航系统（GNSS）高精度应用需求的日益增长，频间钟偏差（IFCB）问题近年来得到广泛研究。基于2023年年积日（DOY）（130～136）澳大利亚地区18个多模实验跟踪网（MGEX）观测数据的无几何无电离层（GFIF）组合，分别估计了北斗卫星导航系统（BDS）、伽利略卫星导航系统（Galileo）和全球定位系统（GPS）卫星的 IFCB 产品。对比分析了BDS-2，BDS-3，Galileo和GPS卫星的IFCB的特点。评估了相位相关的IFCB（PIFCB）误差对GPS BLOCK IIF卫星超宽巷（EWL）未校准相位硬件延迟（UPD）和非组合（UC）三频精密单点定位（PPP）性能的影响。实验结果表明,PIFCB误差对Galileo卫星的影响最小，对GPS BLOCK IIF卫星的影响最大；对BDS-3卫星的影响低于BDS-2卫星；不同信号频率对IFCB产品的估计结果会产生一定的影响。实验结果进一步表明,IFCB产品可以显著提高GPS BLOCK IIF卫星EWL UPD的稳定性和UC三频PPP的定位性能。EWL UPD的平均标准差（STD）从0.064周减小到0.021周，提高了67.2%。UC三频PPP在东（E）、北（N）、天顶（U）三方向分别从4.63 cm，3.04 cm和8.76 cm减小到3.08 cm，2.00 cm和5.85 cm，平均定位精度分别提高了31.5%，34.2%和33.2%。收敛时间小于20 min的比例从66.3%提高到71.8%，提高了5.5%。平均收敛时间从21.13 min缩短到17.24 min，减少了18.4%。

Characteristics analysis of inter-frequency clock bias products of multi-GNSS and its performance evaluation for precise point positioning

With the increasing demand for high-precision applications of multi-constellation global navigation satellite systems (GNSS), the inter-frequency clock bias (IFCB) issue has been widely studied in recent years. Based on the geometry-free and ionosphere-free (GFIF) combinations of observation data from 18 multi-GNSS experiment (MGEX) stations in the Australian region from day of year (DOY) 130 to 136 in 2023, the IFCB products of the BeiDou navigation satellite system (BDS), Galileo navigation satellite system (Galileo), and global positioning system (GPS) satellites are estimated, respectively. The characteristics of IFCB for BDS-2, BDS-3, Galileo, and GPS satellites are analyzed and compared. The impact of phase-specific IFCB (PIFCB) errors on the positioning performance of GPS BLOCK IIF satellite''s extra-wide-lane (EWL) uncalibrated phase hardware delay (UPD) and uncombined (UC) triple-frequency precise point positioning (PPP) is evaluated. Experimental results show that the impact of PIFCB errors is minimal on Galileo satellites and greatest on GPS BLOCK IIF satellites; the impact on BDS-3 satellites is lower than that on BDS-2 satellites; different signal frequencies have a certain impact on the estimation results of IFCB products. Furthermore, experimental results indicate that IFCB products can significantly improve the stability of GPS BLOCK IIF satellite EWL UPD and the positioning performance of UC triple-frequency PPP. The average standard deviation (STD) of EWL UPD increases from 0.064 cycles to 0.021 cycles, an increase of 67.2%. The UC triple-frequency PPP decreases in the east (E), north (N), and up (U) directions from 4.63 cm, 3.04 cm, and 8.76 cm to 3.08 cm, 2.00 cm, and 5.85 cm, respectively, with average positioning accuracy improvements of 31.5%, 34.2% and 33.2%. The proportion of convergence time less than 20 min increases from 66.3% to 71.8%, an increase of 5.5%. The average convergence time decreases from 21.13 min to 17.24 min, a reduction of 18.4%.