Research On The Method Of Obtaining Wave Information Based On X-band Coherent Radar

The ocean is a pure blue treasure which contains a large number of resources.Since modern times,with the development of science and technology,human beings have gradually shifted their vision of development to the ocean.But while nature brings such rich gifts,it also brings disasters and tragedies.Therefore,in order to ensure the safety of shipping,coastal cities and various maritime operations,people try to use various methods to observe the unpredictable information of sea conditions.Compared with other measurement methods,X-band radar has many advantages,such as high resolution,large observation range and low cost.Therefore,this paper studies the method of obtaining wave parameters information based on X-band coherent radar.Firstly,the formation mechanism of two data sets(radar wave image and Doppler velocity field)acquired by X-band coherent radar is analyzed.According to the linear wave theory,we model the random wave height,and add two important modulation functions,shadow modulation and tilt modulation,to obtain the simulated radar wave image.At the same time,through reading and learning a large number of relevant literature,we analyze the composition of Doppler velocity obtained by X-band radar when observing ocean waves,and give a credible data simulation method,and get the simulated Doppler velocity field.These two simulation datasets provide data support for the following algorithm research.Subsequently,the method of reconstructing sea surface wave height field using Doppler velocity field is studied and analyzed in this paper.We reconstruct the wave height field using simulated Doppler data,and the validity of the reconstructed wave height field is demonstrated by qualitative and quantitative comparison with the original wave height field.This conclusion not only proves the credibility of our simulation data,but also gives us inspiration to improve the classical method of wave parameter acquisition-3D-FFT algorithm.Since the 3D-FFT algorithm based on non-coherent radar is used to analyze the intensity of radar image in frequency domain,modulation transfer function(MTF)must be used to correct the image spectrum to wave spectrum.The calculation of MTF requires the use of real wave height information measured by field measurement tools,which brings high work costs.Moreover,the uncertainty of MTF parameters affects the accuracy of the results.In this paper,two improved 3D-FFT algorithms for coherent radar are proposed by combining the reconstructed wave height method with the 3D-FFT method.The first method uses reconstructed wave height field instead of measured data,which greatly reduces the difficulty and cost of MTF acquisition.The second method uses the reconstructed wave height field instead of the wave image as the input of the algorithm,which avoids the use of MTF more thoroughly.The experimental results show that both methods can obtain more accurate wave parameters.Finally,based on the practical application,this paper studies the effective wave height acquisition method when the radar antenna points to the main wave direction for a long time.Considering the energy loss caused by projection effect,the Doppler velocity field in staring mode is simulated and then used to estimate the effective wave height.The simulation results are satisfactory.The deviation between the estimated effective wave height and the real value is less than 0.16 meters.