天波雷达电离层相径扰动去除方法研究

Elimination of the ionospheric phase-path disturbance is the ones of the key and difficult problems in the signal processing for HF skywave radar. So study on how to deal with it is valuable in the scientific research. This project will study on the theory and method of Elimination of the ionospheric disturbance based on the ionosphere observation data and the actual data by HF skywave radar. Firstly, according to the ionospheric data, the time-varying ionospheric model will be established, the effect on radar detection by the disturbance will be analyzed quantitatively through the path-distance transformation, and the mode how the ionospheric disturbance works will also be illuminated. So the ionospheric disturbance will be classified compared with the actual radar data. Secondly, the algorithms on elimination of ionospheric contamination will be studied by the type of the disturbance. For the slow phase-path disturbance, a statistic method on estimation of the disturbance based on the judgment of consistency of the space cells will be given. And For the fast one, which causes the positive and negative Bragg lines' overlapping and unstable, a detection and estimation algorithm in the space of intrinsic mode functions will be proposed. Thirdly, criterions, by which to judge the spectrum with or without disturbance and classification of the disturbance type, will be given for adaptive elimination process by the spectrum. Finally, the processing algorithm mentioned above will be verified by the actual data with different condition, and the results of the target detection and remote sensing will be listed to illuminate the validity.

电离层相径扰动去除是天波超视距雷达信号处理领域中的重点和难点，具有重要的科学研究价值。本项目利用已有的电离层观测数据和天波雷达实测数据，研究电离层相径扰动去除理论与方法。首先根据电离层观测数据，建立全年电离层时变模型，并结合PD变换，定量描述相径扰动对探测的影响，阐释相径扰动机理，并参考雷达实测数据，将电离层相径扰动进行分类。其次研究各类电离层相径扰动去除算法，对于慢相径扰动，提出基于空间一致性判别的相径扰动统计估计算法；对于快相径扰动，此时正负Bragg峰发生混叠，且为非平稳信号，因此提出基于内模式函数空间检测估计算法。再次研究相径扰动自适应去除方法，即提出基于谱结构的相径扰动有无以及类型判断准则，实现相径扰动类型的自动判断与处理。最后，结合天波雷达不同时段多批次的实测数据，利用本项目提出的电离层相径扰动处理方法给出目标检测以及海态遥感结果。

电离层的时变、色散、非平稳特性对天波雷达信号传播产生了不可避免的污染，严重影响了天波超视距雷达的性能。本课题围绕着如何自适应去除电离层相径污染展开研究，具体包括三方面内容：一是电离层扰动类型的建立；二是设计自适应处理的两大判定准则；三是利用现今普遍采用的去扰算法进行去扰效果分析，给出各算法的适用条件。针对上述三点获得了以下结论：.（1）利用观测到的一年的电离层实际数据，分析出电离层扰动类型为多项式与正弦周期信号的组合。.（2）对于慢相径扰动与快相径扰动的区分，提出了采用高频率分辨特性的MUSIC算法，估算一阶Bragg峰附近两谱峰的频率间隔，用于对相位扰动的回波数据的慢快进行判定。.（3）对于快相径扰动与多目标的回波数据的区分，提出了采用HIM算法，根据算法得到的HAF谱，根据其是否具有平移谱变化特性，加以区分。.（4）详细的分析了HRR_SVD、PWVD、ST_MUSIC、PPS及PPS_MUSIC算法的原理，利用仿真数据数据及实际数据对各算法的性能进行检验及证明。得出了调制频率较低时可选取HRR_SVD，PWVD、PPS对污染的天波雷达数据进行校正；在调制频率较高时可选取PPS及ST_MUSIC对污染的天波雷达数据进行校正的结论。.利用实际数据对各算法的实际处理能力进行验证，发现PPS算法对于快慢相近扰动的海杂波谱都有比较好的锐化效果，适宜对数据的批量处理。为后续的目标检测以及海态遥感提供高质量的回波谱。