星载晶振短稳对导航增强系统PPP精度的影响分析

分析星载恒温晶振（Oven Controlled Crystal Oscillator，OCXO）短稳对导航增强系统精密单点定位（Precise Point Positioning，PPP）精度的影响。本文首先介绍了OCXO短期频率稳定度的概念，然后根据其短稳特性进行噪声反演，最后建立了基于OCXO短稳噪声反演的系统PPP定位模型，将短稳量级不同的OCXO反演噪声引入模型并对系统最终PPP定位精度进行分析比较。实验表明：在无控制段调校星上时频的情况下，选用短稳量级为E-13的OCXO在中长观测时间段内（<1 000 s）可满足系统厘米级的定位需求。该分析可为低轨导航增强系统的时频指标设计提供一定参考。

Analysis of impact of crystal oscillator short stability on PPP accuracy of navigation enhancement system

To analyze the effect of Oven Controlled Crystal Oscillator (OCXO) short-stability on the accuracy of Precise Point Positioning (PPP) of navigation enhancement system. Firstly, this paper introduces the concept of OCXO short-term frequency stability, and then inverts the noise according to its short-term stability characteristics. Then, the PPP positioning model of the system based on OCXO short-term stability noise inversion is established, and OCXO inversion noise with different short-term stability magnitude is introduced into the model, and the final PPP positioning accuracy of the system is analyzed and compared. The experimental results show that the OCXO with the short-stability order of E-13 can meet the centimeter-level positioning requirements of the system in the medium and long observation periods (<1 000 s) without the control section to adjust the on-board time-frequency. The analysis can provide some reference for the time-frequency index design of LEO navigation enhancement system.