Subjects: Astronomy >> Astrophysical processes submitted time 2023-11-16 Cooperative journals: 《天文研究与技术》
Abstract： In order to verify the conformity of the multi-path error characteristics of the BeiDou Satellite Based Augmentation System with the International Civil Aviation Organization Dual-Frequency Multi-Constellation Satellite-Based Augmentation System multipath error model，this paper compares the signal characteristics of BDS，GPS and Galileo systems，and then proposes a DFMC BDSBAS multi-path error characteristic verification method based on the multi-path model requirements of ICAO DFMC SBAS. Finally，its conformity is verified by aviation antenna group delay test and measured data. The results show that: (1) Dual-frequency signal characteristics of BDS，GPS and GALILEO are basically consistent；(2) The aerial antenna used in the test meets the requirements of DO￣373 antenna group delay characteristics；(3) The change trend of multi-path error curve of BDS is basically consistent with that of GPS and GALILEO. The multi-path error characteristics of DFMC BDSBAS meet the requirements of multi-path model of ICAO.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-01-17 Cooperative journals: 《天文研究与技术》
Abstract： Radio astronomy uses antenna array for observation in the HF-VHF frequency band. According to the requirements of SKA (square kilometer array), the gain, structure consistency, stability, impedance change trend, polarization purity and other aspects of each array element antenna need to reach high indicators to meet the requirements of Sun, Jupiter, Epoch of reionization and other measurements in polarization measurement, antenna tracking stability and receiver broadband matching and other aspects. According to the performance requirements proposed in SKA requirement 2165: polarization purity 2135-38 and sensitivity per polarization 2814-15. And after summarizing the experience of the original design, this study designed a new type of inverted "V" grid dipole antenna suitable for HF-VHF for the 10-90MHz frequency band, which has the advantages of light weight and small wind resistance. The structure has the advantages of slow impedance change and good polarization purity in the ultra-wide frequency band of 10-90MHz. Among them, in terms of impedance change: the real part of the impedance of the antenna changes from about 0.8Ω to 631.132Ω, which is better than the low-frequency array antenna of the low-frequency radio array, reducing the difficulty of receiver matching and noise; in terms of polarization purity: the overall axial ratio of the antenna is less than 0.41dB, with good polarization isolation for strong polarization signals such as solar radio bursts.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-01-14 Cooperative journals: 《天文研究与技术》
Abstract：为促进全球卫星导航系统（GNSS）在国际航空领域的应用，国际民航组织（ICAO）正在开展面向北斗卫星导航系统（BDS）、GPS、Galileo、GLONASS的标准与建议措施（SARPs）的研究、验证与升级工作。BDS自2010年启动ICAO标准化工作以来，历时11年，参加了50余次技术会议，提交了90余份、千余页技术文件，涉及2000余项问题，关闭了189项验证指标。本文重点围绕时间与坐标基准、射频信号特征、空间信号性能等北斗标准国际化推进过程中的重点问题开展论述。北斗时与国际UTC的偏差保持在50ns以内（模1s），北斗坐标系与ITRF-2014之间的差异不超过3cm；对北斗民用信号落地电平、信号质量、抗干扰能力进行了分析和验证，构建了北斗空间信号畸变模型；最后，明确了北斗在ICAO SAPRs框架下的服务性能定义和计算方法，并利用系统实际数据验证北斗系统空间信号性能均满足设计指标要求。以上的分析、模型与验证结果表明，北斗系统具有良好的时空兼容与互操作基础，射频信号质量高、抗干扰能力强，相关内容满足指标要求，能够提供面向国际航空领域的高安全高完好性导航服务，已被写入ICAO BDS SARPs中，为我国北斗系统国际化及民航领域推广应用奠定了良好的理论、标准及验证基础。
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