Ionospheric Echo Analysis And Suppression Algorithm Research Based On Beibu Gulf Ocean Echo Data

Guangxi Beibu Gulf Economic Zone is the key areas of the economic policy named" the Belt and Road", and has an irreplaceable role. Inversion of Beibu Gulf marine environment kinetic parameters, detecting moving targets ocean surface and monitoring low-altitude targets, by high-frequency surface wave radar, are important ways for environmental protection of the Beibu Gulf Economic Zone in Guangxi. Portable high-frequency surface wave radar is mainly used in the sea wind, waves and low-flying target detection, but ionospheric echoes, sea clutter and other disturbances will reduce the detection reliability. Echo ionosphere with high-strength energy, regional and other characteristics, is considered the bottleneck in the development of high-frequency surface wave radar, so the research on ionospheric echo characteristics and ionospheric echo suppression algorithm is very necessary.Ionospheric echo suppression algorithm is divided into two directions:First, the improvements of hardware configuration of the radar, such as making the horizontally polarized antenna and vertically polarized antenna work together, increasing the frequency of the radar in order to improve the ionospheric echo anti-jamming capability. Second, perform ionospheric echo suppression with data processing algorithms, for example, the whole space-time adaptive method, time-frequency masking methods and so on. Now, the main research is to propose different ionospheric echo suppression algorithms for different types of rader, but the comparative analysis of the relevant literature for the same type of radar data processing algorithms using different ionospheric echo suppression is short, and research on ionospheric echo suppression of data obtained by portable high-frequency ground wave radar (OSMAR-S) is even more rare. In this paper, the analysis of ionospheric echo characteristics and the research on ionospheric echo suppression algorithm for the experimental data obtained by portable HF radar are made, mainly in the following four aspects:(1) The causes of ionospheric echo:analysis hierarchy and state variation of the ionosphere, and it will provide the inference basis for ionospheric echo reflection height in the experimental data; analysis propagation of electromagnetic wave in the ionosphere, and it will explain the presence of ionospheric echo in the marine echo spectrum.(2)The effect evaluation criteria for ionospheric echo suppression:combining the hardware structure of portable high-frequency radar and the mechanism of receiver data processing, analysis peak signal to noise ratio calculation method and propose an ionospheric echo suppression comparison programme that is normalized percentage amount, laying the groundwork for the ionospheric echo characteristics.(3)The study of ionospheric echo characteristics:analysis characteristics of ionospheric echo, which is from experimental data, in the range Doppler domain, distance yuan Doppler domain, distances field and other signal fields and summarize the experimental site ionospheric echo characteristics, performing mathematical statistics for the time and form of ionospheric echo appears in distance Doppler spectrum.(4)The study of ionospheric echo suppression method:perform ionospheric echo suppression for measured data with wavelet shrinkage threshold algorithm and virtual frequency hopping algorithm based on wavelet shrinkage threshold, and comparative analysis the results of suppression with the orthogonal projection filtering algorithm, summarizing the feasibility and effect of both suppress ionospheric echo algorithms.The results show that the ionosphere echo in the experimental data has day and night periodicity, and is generated mainly by the ionospheric spread F-layer reflecting electromagnetic waves. When perform ionospheric echo suppression for data obtained by portable high-frequency surface wave radar, under the premise of streamlined calculation wavelet shrinkage threshold method is a preferred method, under the premise of high-precision virtual frequency hopping method is a preferred method.