低频天波传播相位延迟的高精度预测方法研究

Low-frequency radio navigation system is the major part of national Positioning, Navigation and Timing (PNT) system and the PNT capabilities have been significantly improved in recent years, but low-frequency skywave propagation prediction restricts the development of the system and limits its further exploration of super long-range navigation ability (long distance, high precision). This research aims to study the method of high precision and fast forecasting of the phase delay of low frequency skywave propagation characteristics and excavate its superlong-range PNT ability. The innovation includes: ①A weighted laguerre polynomials based Stochastic Finite-Difference Time-Domain (WLP-S-FDTD) method is proposed for magnetized plasma with random characteristics, taking into account the anisotropy and random characteristics of the magnetized plasma medium. ②Two kinds of low dispersion Weighted Laguerre Polynomials based Finite-Difference Time-Domain（WLP-FDTD）methods combining with the space and time domain are proposed: the space domain high order difference method and the transformation of spatial differential to spectral domain method. ③A hybrid model combining WLP-FDTD method and Ultra Wide Band Gausses Beam tracing (UWB-GB) method for low-frequency skywave propagation prediction is presented, which can reduce computation load and memory cost, and maintain high calculation precision, thus laying a good foundation for high precision analyzing the low frequency wave propagation properties and excavating its superlong-range navigation ability of low frequency radio navigation system. ④The deep learning method applied in skywave propagation prediction is exploratory studied for the first time.

低频无线电导航系统是国家PNT体系重要组成部分，近年来卓有成效的工作使其PNT能力显著提高，但是，低频天波传播预测限制了其超远程导航能力（远距离、高精度）的深入挖掘。本项目拟研究低频天波传播相位延迟高精度快速预测方法，深入挖掘其超远程PNT能力，创新包括：①提出一种具有随机特性的磁化等离子中WLP-S-FDTD方法，同时考虑了磁化等离子媒质各向异性和随机变化两种特性；②提出两种空时结合的低色散WLP-FDTD方法，一是空域高阶差分降低色散，二是把空域微分变换到谱域求解降低色散，从而使WLP-FDTD同时在时域和空域上低色散；③提出一种低频天波传播预测“WLP-FDTD”+“UWB-GB”混合模型，在降低计算量和内存消耗的同时确保了高精度计算结果，为高精度分析低频天波传播特性、深入挖掘低频无线电导航系统超远程导航能力奠定了基础；④首次对深度学习方法在天波传播预测中的应用进行探索性研究。

低频无线电导航系统是国家PNT体系重要组成部分，近年来卓有成效的工作使其PNT能力显著提高，但是，低频天波传播预测限制了其超远程导航能力（远距离、高精度）的深入挖掘。项目组首先从理论创新出发，研究了低频天波传播相位延迟高精度快速预测方法、高精度的天地波分离方法；同时，搭建长时间的监测系统和采集系统，通过外场试验验证理论结果，为理论应用于工程实践打下坚实基础。具体的创新工作包括：①提出了具有随机特性的磁化等离子中WLP-S-FDTD方法、PCE-BT-FDTD方法，可同时考虑磁化等离子体媒质各向异性和随机变化两种特性；②针对大区域复杂低频电波传播预测问题，借鉴现有PE方法相关研究成果，进行适应性创新。同时，与FDTD方法结合构建混合模型，提出适用于平坦区域的FEF-TDPE方法以及适用于源区复杂环境的FDTD-TDPE方法；③搭建了长期的监测系统及采集系统，为理论分析提供大量实测数据；④为了在实测数据中准确获得天地波时延，研究了多种天地波分离方法，其中首次对深度学习方法在天波传播预测中的应用进行探索性研究，取得了很好的效果。通过以上四个方面的研究，形成了完整的闭环分析，从理论分析到实测验证，各种方法之间优势互补，形成了对大区域低频天波传播的高精度快速预测能力。