IFB不确定性对双频码载分歧监测的影响分析

Impact of IFB uncertainty on dual-frequency code carrier divergence monitoring

码载分歧(CCD)监测器是卫星导航地基增强系统(GBAS)引入的完好性监测器之一,用于监测码伪距与载波相位观测值之间的不一致性。双频平滑技术的引入改变了CCD监测器的检验统计量等参数,进而影响了监测性能。针对双频GBAS中存在的频间偏差(IFB),基于北斗双频观测数据,分析IFB不确定性对于双频码载分歧监测性能的影响。研究结果表明:在IFB不确定性的影响下,监测器的阈值增大了26.1%,导致其在发生CCD故障情况下的漏检率显著增大,最小可检测故障值增大了26.9%,监测器的灵敏度降低;最坏情况下系统完好性损失概率从低于10^(-14)增大到接近10^(-8),同时机载端为满足漏检率性能安全要求所引入的延迟值更大,导致CCD监测器的故障响应变慢,双频GBAS的完好性受到影响。

Code carrier divergence(CCD)monitor is one of the integrity monitors introduced by ground-based augmentation systems(GBAS),which is used to monitor the inconsistency between code pseudorange and carrier phase observations.Dual-frequency smoothing technology changes the test statistics and other parameters of CCD monitor,which affect the monitoring performance.Considering the inter-frequency bias(IFB)introduced in dual-frequency GBAS,the impact of IFB uncertainty on the dual-frequency CCD monitoring is analyzed based on the dual-frequency observation data of BDS B1I and B3I signals.The results show that under the influence of IFB uncertainty,the threshold of the monitor increases by 26.1%,resulting in a significant increase of the probability of missed detection(PMD)in the case of CCD fault.And the minimum detectable fault increases by 26.9%,which means a decrease in the sensitivity of the monitor.Meanwhile,the probability of the loss of integrity in the worst case increases from less than 10^(−14) to nearly 10^(−8),and the delay introduced by the airborne to meet the PMD requirement is larger,resulting in a slower response of CCD monitor and impacts the integrity of dual-frequency GBAS.