Research On Key Techniques Of Wave Remote Sensing Based On Marine Radar

Ocean wave is the most common and important ocean fluctuation phenomenon, which has close relations with many important issues such as ocean exploration, ocean development and utilization, especially marine military technology and navigation safety. An important condition of ocean wave observation is provided by the development of radar technology, especially in marine radar technology.The marine radar observing waves is realized through the analysis of sea echo varied with time and space, which come from the ocean surface, the real-time near-surface current and sea state parameters (peak wave period, peak wave direction and significant wave height.) obtained by wave spectral analysis.The method of wave observed by marine radar has incomparable superiority and greatly potential application value compared with other method, for there is no direct contact between sea and marine radar. Therefore, the use of marine radar observing waves is increasingly attracted wide attention from scholars at home and abroad.In this dissertation, based on the theory and development of ocean remote sensing technology are systematically analyzed, the key technologies of ocean wave observation, wave image data acquisition, wave image pre-processing, current estimation and ocean wave parameters inversion are deeply researched.In view of specific demands of the subject, based on the radar units and the function feature of radar output signal are researched, a multi-channel signal acquisition method based on interval sampling mode is presented in this dissertation. Through profound analysis of function feature of PXI-9820 high-speed data acquisition card, the hardware platform of data acquisition is designed. At the same time, the radar echo signal data acquisition software is designed and realized based on Windows/PXI system. At last, the feasibility and reliability of the platform is proved by the subsequent shore-based experimentation.In this dissertation, the rain clutter and the same frequency interference noise are taken into account.Firstly, on the basis of systematic analysis of a large number of rainfall image features, an analyzing and processing method is proposed for rainfall observation data in wave monitoring system by marine radar which uses the statistic characteristic-mean value and variation coefficient of radar echo image in order to distinguish rainfall and non-rainfall image.Secondly, in order to inhibit the same frequency interference noise effectively, a novel algorithm for co-channel interference noise suppression is proposed based on the wavelet transform in this dissertation. The high-frequency details part of image are extracted by the wavelet transform.According to the histogram distribution of wave image, a threshold value is used to determine sea echo signal points and noise points.Then the property values of determined noise points are substituted with the adjacent signal points.The result of Experiments shows that the algorithm is effective for the image noise suppression.Considering the main problem of current estimates, a novel algorithm for retrieving ocean surface currents is presented in order to reduce errors in wave directional spectrum, which based on the minimum variance and iterative algorithm. The objective function of current estimate is based on minimum variance.The ocean current is determined by using dispersion relations. At the same time, the energy set of the dispersion relation is determined using the Gaussian normal distribution principle.Experimental results show that the stability and accuracy of the currents estimation could be improved by the proposed algorithm in this dissertation.Taking into account the specific requirements of ocean wave parameter inversion, an improved band-pass filtering algorithm is proposed in this dissertation. Through a deep study of the monotonicity, continuity and convergence of the dispersion relation equation, the main areas of dispersion relations could be determined. Based on this algorithm, a more reasonable and accurate band-pass filter is designed to improve the accuracy of wave parameters inversion. Experimental results show that more accurate information of the wave spectrum for wave parameters inversion could be extracted by the improved band-pass filtering algorithm.