Research On Target Localization Correction Methods Under The Mixes Propagation Mode

The echo signal of HF over-the-horizon radar is a signal mode which combined with Surface wave radar and Sky wave radar. In this paper, a research will be done on the propagation mode combined with both surface-wave mode and sky-wave mode caused by the diffuse scattering characteristic of target. This paper aims at modifying the distance information of the target based on the conventional surface wave radar and improving the accuracy of target localization. The study of the mixed propagation mode mainly involves study on the characteristics of ionospheric parameters, establishment of echo signal model under this mode, derivation of related application conditions and research on modifying the distance information of the target using the echo signal.In this paper, the basic structure of the ionosphere and the electromagnetic wave propagation mechanism are analyzed, the layered structure of the ionosphere and the parameters of each layer are described in detail and the mechanism of electromagnetic wave propagation in the ionosphere and the multi-path model are discussed. For mixed propagation mode, this paper establishes a multi-path model, analysis of the application condition of this mode and carries out calculation and simulation analysis of the hop distance of the sky wave mode, the sky wave echo path propagation attenuation and the ground echo path propagation attenuation. On the basis of this, a target location method based on the mixed propagation mode is proposed. The steps of the method are as follows. Beam forming data is obtained by data processing method, then target detection and track processing are done to confirm the suspected target surface wave echo path. Using the information obtained by RD spectrum and target detection, we can determine the suspected target sky wave path echo which is corresponding to the surface wave path echo. To do this processing, this paper proposed 5 criteria of matching processing. Then, the sky wave distance correction is done to get the right echo information for both sky wave path and surface wave path. To solve the problem of how to obtain the ionosphere height and other parameters over the high frequency surface wave radar range over the HFSWR coverage, this paper presents two methods to obtain the height information of the ionosphere. The converted surface wave path distance is gotten by using the ionospheric height information and sky wave path distance. Making a comparison with the converted surface wave path distance and the original surface wave path information, the final conclusion of correction of the simple ground wave path distance and the target location is completed. Meanwhile, the aircraft target height estimation method based on the mixed propagation mode is proposed.Using this method and the measured data of a surface wave over-the-horizon radar experiment, a complete data processing has been done to get the modified surface wave target distance. Compared to the original surface wave target distance, the correction of target localization of surface wave over-the-horizon radar has been achieved, the rationality and feasibility of the method are verified preliminarily and a certain foundation has been laid for further research on this mixed propagation mode.