Study On High Frequency Radar Ocean Surface Scattering And Remote Sensing

With the development of the economic construction and national defense construction, the oceans occupy and increasingly important position in the national strategy, ocean dynamics research needs of the nearshore environment is becoming more and more urgent. For the real effective environment for the nearshore ocean dynamics monitoring the ecological environment can provide a scientific basis for inshore marine and coastal economy can avoid significant losses due to poor ocean dynamics environment brings, so we urgent need for near-shore marine remote sensing technology for more in-depth study effectively. High Frequency Ground Wave Radar (HFGWR) is a over the horizon radar, it is easy to ues and its cost is low, it has been developed in recent decades as a new equipment for monitoring the marine environment, the HFGWR can monitor the marine environment real-time, all-weather and can monitor large area over the horizon, and its future development and research value are considerable. Therefore, many countries in the world made a lot of research and work into HFGWR. Sea state parameters extraction of HF radar for actual production application has a very significant meaning, and the electromagnetic scattering problems are theoretical foundation of the HFGWR for the long-term development of the HF radar. As the science and technology are developing, theoretical equations and real data during experiments inconsistency for more in-depth understanding and applying to the technology of the ocean remote sensing which has some limitations, so we need to establish a theoretical model consistent with the measured data, the existing theoretical models some supplement and perfect. This thesis is based on the subject background, rough surface on the ocean echo model electromagnetic scattering theory has been researched, and also some research on ocean dynamics and process parameter extraction algorithm processing. The main work of this thesis is as follows:1. The law and the principle of the higher-order Bragg scattering has been observed and analyzed very detail, and the high-order Bragg scattering models have been modeled, then the perturbation method has been used to analyze the equations of the electromagnetic scattering cross section problems on the ocean surface. According to the model of the incident wave and scattered wave, analyzing with the boundary conditions for the equations and the Maxwell's equations, the equations of the higher-order Bragg scattering cross sections can be obtained. The original scattering model supplemented. And various marine radar Doppler frequency spectra have been simulated and modeled.2. Based on the pattern formula of the crossed-loop/monopole antenna and the pattern formula of the linear binary array, the derivation of the pattern of the two-element crossed-loop/monopole, and the digital beamforming (DBF) algorithm has been done to process the measured radar echo data of the HFGWR, and the DBF results of the two-element crossed-loop/monopole array have been compared with the original sea echo and the DBF results of the crossed-loop/monopole antenna.3. The track of the typhoon Bolaven has been presented using experimental data collected by the HF OSMAR-S radar during typhoon Bolaven. The variation of the Doppler spectra of the HF radar that before, during and after the typhoon is very obvious and has been successfully observed. The Doppler spectra change as the wind speed or the direction changes. This variation can be clearly observed from the time before, during and after a typhoon and is therefore useful used for monitoring the passage of the typhoon. In this thesis, the variation of the Doppler spectra during typhoon Bolaven are presented and analyzed.