北斗三号基本系统空间信号质量评估

全球卫星导航系统(GNSS)空间信号(SIS)质量直接影响了用户使用性能。北斗三号卫星不同于北斗二号卫星，将继续播发北斗二号老信号，同时新增播发B1C, B2a等新信号，多频多信号多分量的信号体制较北斗二号更为复杂，对导航卫星信号质量控制提出了较大挑战。2018年底北斗系统完成了18颗卫星组网，完成北斗三号基本系统建设并开始提供全球服务，有必要对北斗三号在轨卫星空间信号质量进行量化评估。传统空间信号质量评估方法侧重于单项的定性评估，而针对北斗三号复杂的信号体制，缺乏系统的、定量的分析结果。该文对标北斗系统接口控制文件(ICD)，从功率特性、频域特性、时域特性、相关域特性和信号一致性等方面研究了不同参数配置对评估结果的影响，形成了一套面向新型调制方式和多频多分量复用信号的量化评估方法。基于40 m大口径天线的空间信号质量评估系统，对18颗MEO卫星进行了长时间监测跟踪和数据采集，首次对北斗三号卫星空间信号质量进行了全面量化评估。结果表明:北斗三号卫星空间信号质量良好，18颗MEO卫星一致性较好，符合ICD指标要求，可满足服务区内用户需求；评估方法可用于对后续导航卫星空间信号质量的量化评估。

Signal Quality Assessment of BDS-3 Preliminary System

The Signal-In-Space (SIS) quality affects directly the user performance of Global Navigation Satellite System (GNSS). Unlike BDS-2, the BDS-3 satellites not only broadcast old signals, but also broadcast new signals such as B1C and B2a at the same time. The signal structure of BDS-3 with multi-frequency, multi-signal and multi-component is more complex than BDS-2, which is a great challenge to signal quality control of BDS-3 satellites. By the end of 2018, 18 BDS-3 satellites were successfully launched and the BDS-3 preliminary system is completed to provide global services. It is necessary to evaluate the signal quality of BDS-3. Traditional signal quality assessment methods focus on the qualitative assessment of a single item, but lacks systematic and quantitative analysis results for the complex signal structure of BDS-3. Based on the Interface Control Document (ICD) of BDS, this paper studies the influence of different parameter configurations on the evaluation results from the aspects of power characteristics, frequency characteristics, time characteristics, correlation characteristics and signal consistency, and forms a set of quantitative evaluation methods for new modulations and multi-frequency, multi-component signals. Based on the signal quality assessment system with 40-meter aperture antenna, 18 MEO satellites of BDS-3 preliminary system were monitored, and the signal quality of BDS-3 satellites were comprehensively and quantitatively evaluated for the first time. The results show that, signal qualities of BDS-3 satellites are good, and the 18 MEOs have a good consistency, which can meet the requirements of ICD and GNSS users. The evaluation methods can be also used to quantitatively evaluate the signal quality of other satellites.