Research On Wave Information Inversion Algorithm Based On Shipborne Radar

In recent years,in order to improve the strategic position and promote the military and economic development,countries around the world have paid more and more attention to the development and utilization of ocean resources.As a large ocean country,China’s demand for the development of ocean industry is also increasingly prominent.However,the complex and changeable ocean environment poses a great threat to the safety of many maritime activities,so it is very important to improve the accurate estimation of ocean environment elements such as waves and currents.Wave monitoring system with X-band marine radar as the core has the advantages of low cost,small size,real-time observation with the navigation of ships,and is widely used in ocean development.Therefore,this paper takes X-band radar as the research object,and studies how to improve the inversion accuracy under static base condition and how to correct the region offset caused by carrier shaking under moving base condition.The main research contents are as follows:Firstly,the basic concepts,working principle and imaging modulation mechanism of marine radar are introduced.Radar images under different sea conditions are simulated with random sea wave model and corresponding radar sea clutter image simulation methods,which provides a technical basis for subsequent theoretical research.Then,the inversion method of current and wave parameters based on X-band marine radar under static base is studied.For estimating ocean current parameters,the inversion is performed using classical least squares(LS),iterative least squares(ILS)and normalized scalar product(NSP)algorithms,respectively.The results show that the NSP algorithm with variable step size can effectively shorten the data processing time.For estimating the significant wave height,in order to improve the accuracy of effective wave height estimation,a new effective wave height estimation algorithm based on independent component analysis is presented to overcome the limitation that the Fourier transform method can only be applied to uniform and stationary signals.The algorithm decomposes the radar image data based on the theory of wave composition to calculate the original harmonic components of the wave,and fits the relationship between the original signal energy and wave height to achieve an accurate estimation of wave height information.The related algorithms are validated with the simulated and measured data.The results show that the NSP algorithm has obvious superiority when estimating the surface current on a static base.The estimation results of significant wave heights show that the proposed algorithm is applicable to the nonstationary,nonuniform random signal,such as sea waves,and can obtain higher inversion accuracy of wave heights.Finally,under the condition of moving base,taking the ship as an example,the influence of carrier shaking on radar is studied.Using the conversion relationship among ship,radar and geographic coordinate system,the offset of radar irradiation area is analyzed.Combining with the theory of electromagnetic wave,it is proved that the influence of shaking on the return strength of radar electromagnetic wave can be ignored.To solve the problem of increasing wave height estimation error caused by the offset of radar irradiation area caused by the ship’s own shaking,a dynamic selection scheme for image analysis area is presented.The scheme takes the ship’s posture information as input,and achieves the dynamic selection of the analysis area,thereby reducing the influence of the shaking on the inversion results.The simulation results show that the dynamic area selection proposed in this paper can effectively reduce the estimation error caused by ship shaking,especially in high sea conditions.