Sky Wave OTH Radar Signal Processing Research Based On The Uniform Circular Array

The OTH radar uses the ionospheric reflection of the electromagnetic wave to show great potential advantage in the early warning.The angle resolution ability of the circular array is combined with the high resolution multipath identification method proposed in this thesis,which can effectively suppress the multipath clutter and greatly improve the accuracy of target detection.In this thesis,a typical solution to the sky-multipath problem is proposed,and the solution of the OTH radar is given.The combination of circular and OTH radar organic combination of advantages,complement each other,showing excellent performance.The workflow is as follows: 1.Generate multipath echo for the skywave background;2.Identify multipath blur according to generated echoes;3.Suppress multipath clutter by multipath identification information.The details are as follows:First of all,in order to facilitate the simulation in the background of the sky wave OTH radar,a set of OTH radar modeling and simulation platform was developed.The platform design ideas,interface design and array selection are described.By using the combination of theoretical analysis and experimental research,the whole signal processing process of sky wave radar is discussed.By selecting a reasonable background condition,the simulation produces multipath echoes.Then,we study the multi-path clutter identification,and use the circular array symmetry to extend the data matrix through the pitch dimension to distinguish the multipath target,and give the high precision recognition algorithm using the sparse Bayesian learning theory.By dynamically updating the regularization factor in the sparse reconstruction problem,a better reconstruction effect is obtained than the compression-aware algorithm of the fixed factor.This method overcomes the problem of performance deterioration of the traditional angle recognition method caused by signal correlation.Combining the multipath simulation signal,it successfully identifies the target and multipath clutter,and verifies the practicability of the algorithm.And in the small angle interval scene,the algorithm's high resolution ability is confirmed.Finally,the algorithm of multipath suppression is discussed,and the common multipath suppression technique is described.It is proposed to suppress the multipath clutter with robust beamforming.The reason for choosing robust beamforming is that the expected and actual array response is mismatched while still maintaining the effectiveness of suppression.Based on DC optimization theory and the replacement of optimal value function(OVF),the multipath suppression algorithm is given,and the algorithm is used to verify the feasibility of the algorithm.