## 1 Introduction  
The BeiDou Navigation Satellite System (BDS) is a global satellite navigation system developed by China. The successful launch of the first group of networking satellites on 5 November 2017 marked the start of the third-generation BDS (known as BDS-3) entering the global construction stage. As of December 2019, all three inclined geostationary satellite orbit satellites (IGSO) and twenty-four medium earth orbit (MEO) satellites of BDS-3 have been easily launched ([[http://www.beido.u.gov.cn](http://www.beido.u.gov.cn)]([http://www.beido.u.gov.cn](http://www.beido.u.gov.cn))), and the completion of MEO satellite networking represents the completion of the core constellation deployment of BDS-3. Compared to the BDS-2 satellites, the new system signals, B1C and B2a, which are the two major public service signals of BDS-3, are broadcast on the BDS-3 satellites. With the construction of four global navigation satellite systems (GNSS), the compatibility and interoperability between systems has become increasingly important. The B1C signal shares a frequency band (1575.420 MHz) with the global positioning system (GPS) L1 and Galileo E1 civil signals, and the BDS B2a/GPS L5/Galileo E5a signals share the same frequency band (1176.450 MHz), which means that BDS-3 further integrates into the family of GNSS and will also bring significant changes in satellite navigation receiver technology, including improvements to the service performance and reductions in power consumption and the cost of equipment. To a great extent, the accuracy, reliability, and availability of satellite navigation signals depend on the observation quality of satellite navigation signals in which the code-phase divergences (code bias variations) are an important part of the quality evaluation, which is a prerequisite for ambiguity resolution [1] and high-precision absolute positioning such as precise point positioning (PPP) [2,3]. [PERSON] et al. [4] first determined that the code-phase divergences exist based on COMPASS-M1 tracking data. Many scholars have done in-depth research on identifying code-phase divergences in BDS-2 with diverse COMPASS-capable multi-frequency GNSS receivers and various data sources made public, for example Multi-GNSS Experiment (MGEX) [5]. The satellite-induced code bias variations are about 1 m from the horizontal range to the zenith for BDS IGSOs and MEOs, which is related to the elevation, frequency, and orbit type [2,3,6,7,8]. In GNSS data processing, the code bias variation severely affects the accuracy and stability of wide-lane ambiguity that is derived from the Melbourne-Wubbena (MW) combination and finally degrades the precision of BDS PPP ambiguity estimations for BDS-2 satellites [9,10]. Additionally, a very strong systematic effect of about 1 m is found in the height component in single-frequency ionosphere-free combination PPPs [2]. The code variations of the BDS-3 experimental satellites and BDS-3 satellites have already been discussed in previous research with the development of BDS-3 system [11, 12, 13, 14, 15, 16]. [PERSON] et al. [13,14] analyzed all signals based on the two IGSO and three MEO experimental satellites measured by a single receiver and multiple receivers, respectively, using normal geodetic antennas; their results show that the satellite-induced code bias for BDS-3 experimental satellites and signals can be negligible for observations observed at different stations' MW values. Some studies proved that the code bias variation of BDS-3 satellite with normal geodetic antennas is less than that of BDS-2 satellite and there is no apparent satellite-induced code bias on BDS-3 satellites [16, 17, 18]. The code observations for BDS-3 satellites, however, may be contaminated due to the low gain of normal geodetic antennas and multipath (MP) error from the surroundings. [PERSON] et al.