Research On The Problem Of Sea Clutter Suppression And DOA Estimation For The Shipborne High Frequency Surface Wave Radar

As a new type of radar,Shipborne High Frequency Surface Wave Radar(HSFWR)has received wide attention due to its flexibility and characteristics of over-the-horizon detection.In shipborne HFSWR,error compensation of antenna elements and arrays is one of the key technologies for signal processing.Due to the limited installation position of the antenna and the influence of the hull structure,the directional pattern of the antenna array element will largely deviate from the ideal array element.If the array error cannot be properly compensated,it will cause the failure of the sea clutter suppression algorithm and the misalignment of the azimuth estimation algorithm.Therefore,based on the echo characteristics of shipborne HFSWR and error analysis,the clutter suppression and azimuth estimation algorithms based on error compensation are proposed respectively.Based on this,the possibility of error correction by neural network is explored.In the array error model considered in this paper,the amplitude phase error of the array is related to the direction of the echo.This error is called the antenna pattern error.Antenna pattern error is most common in engineering,this model is the most versatile and challenging.In this paper,the echo model of shipborne HFSWR in the background of antenna pattern error is established and deduced in detail.Through the analysis of traditional clutter suppression algorithm and azimuth estimation algorithm,the influence of array error on traditional algorithm is discussed.The simulation results verify that the antenna pattern error will invalidate the traditional algorithm.Furthermore,for the problem that the antenna pattern error will make the traditional azimuth estimation algorithm invalid,this paper proposes three kinds of azimuth estimation algorithms based on array error compensation: Error Compensation Digital Beamforming algorithm,Error Compensation Multiple Signal Classification algorithm and Error Compensation Minimum Variance and Distortion Free Response algorithm based on error compensation.Three kinds of algorithms can reduce the impact of array error on the azimuth estimation algorithm.The measured and simulated data verify the effectiveness of the algorithm.Then,this paper studies the problem that the antenna pattern error leads to the failure of the traditional clutter suppression algorithm.The array steering vector is compensated according to the proposed echo model,and Error Compensation Orthogonal Weighting(EC-OW)algorithm is proposed.In addition,according to the fact that the antenna pattern error will change slowly with time and environment,the EC-OW algorithm is improved.Two beamforming algorithms of null widening are proposed: Null Increased Error Compensation Orthogonal Weighting(NI-ECOW)algorithm and Power Suppression Error Compensation Orthogonal Weighting(PS-EC-OW)algorithm.Simulation experiments verify that the proposed algorithm can effectively suppress the widened sea clutter in the background of antenna pattern error.Finally,for the slowly changing antenna pattern error,this paper introduces the neural network to estimate the azimuth of the target signal affected by the error.Firstly,the article discusses the possibility of azimuth estimation through neural networks,and then BP neural network and RBF neural network are used to fit DBF,MUSIC and Error Compensation Multiple Signal Classification algorithm algorithms.An azimuth estimation algorithm based on RBF neural network is proposed to estimate the direction of the coherent and incoherent signals affected by the error.The experimental results verify that the proposed algorithm is robust to the antenna pattern error.