ICAO二阶阶跃模型下信号畸变对导航接收机载噪比估计影响分析

载噪比是评估导航信号质量的重要指标，直接影响着接收机的捕获、跟踪和电文解调性能。论文推导了基于国际民航组织（ICAO）二阶阶跃信号畸变模型下导航接收机采用相关、非相关处理时载噪比估计与信号畸变参数之间的解析表达式，并分析了导航信号畸变参数对载噪比估计的影响。仿真结果表明，数字畸变参数变化范围下导航信号载噪比变化在10-2量级，增大模拟畸变的振荡频率或者减小衰减频率将会提高载噪比估计值，模拟畸变参数变化引起的载噪比损耗可达0.1dBHz，畸变参数对载噪比估计的影响整体上都较小，因此利用接收机输出载噪比作为导航信号异常监测手段是不完备的。

Analysis of the influence of CNR estimation for GNSS receiver based on ICAO 2nd-Order Step Threat Model

Carrier-to-noise ratio (CNR) is an important indicator to evaluate the navigation signal quality, directly affecting the GNSS receiver performance of carrier tracking, data demodulation and signal acquisition. In this paper the analytical expressions between CNR estimation and the distortion parameters of ICAO 2nd-order step (2OS) threat model are induced using both coherent early-late processing (CELP) and non-coherent early-late processing (NELP). And then the relationship between distortion parameters and CNR estimation loss is analyzed. Simulation results show that CNR only changes in the 10-2 order of magnitude when the TMA parameter changes within the set range, and can reach about 0.1dBHz caused by the TMB parameters. When increasing the TMB oscillation frequency and decreasing the attenuation factor can increase the estimated CNR. Consequently the distortion parameters of ICAO 2OS threat model have a small influence on the CNR estimation loss and using the output CNR of the GNSS receiver to monitor the navigation signal abnormality is not reliable.