Research On Radar Target Imaging Technology Of Electromagnetic Vortex

The vortex electromagnetic waves(VEM),which carries orbital angular momentum(OAM),is higher information transmission and information acquisition ability than traditional electromagnetic waves,due to its unique modal orthogonality and spiral phase structure.It has attracted extensive academic attention in the field of wireless communication and radar imaging.Aiming at the main problems existing in electromagnetic vortex radar technology,this thesis carries out research based on OAM radar imaging theory.The imaging models in the scene of gazing and synthetic aperture radar(SAR)are established and analyzed,respectively.Target recognition is carried out by different reconstruction algorithms,and super-resolution radar imaging of target is realized.The main contents are summarized as follows:Firstly,this thesis introduces the background and significance of the research,outlines the traditional radar imaging technology,and summarizes detailed the current research situation in the field of electromagnetic vortex radar imaging.Then the basic theoretical knowledge of orbital angular momentum and vortex electromagnetic wave are explained,and the radiation field characteristics of vortex electromagnetic wave used in radar detection and imaging are analyzed,and the principle of electromagnetic vortex radar imaging is summarized.To offer theoretical support for further research.Secondly,the theoretical research on electromagnetic vortex radar staring radar imaging is carried out.Aiming at the problems that electromagnetic vortex radar does not have the ability to find elevation angle and high-resolution azimuth imaging requires a large number of OAM modes,the radar imaging model is improved.The multiple signal classification(MUSIC)algorithm is used to realize a single OAM mode two-dimensional target reconstruction.Aiming at the problem that radar transceivers require a large number of phase control units and high costs,a two-dimensional imaging method for electromagnetic vortex passive radar targets based on time modulated circular array(TMCA)is designed.The results show that this method can realize two-dimensional joint detection of pitch angle and azimuth angle of radar target.Compared with the current vortex radar imaging method,the complexity of system is effectively reduced.Finally,the theoretical study of electromagnetic vortex SAR imaging is carried out.The side-view vortex strip-map SAR model is constructed,aiming at the problem of too high side lobes in the azimuth profile in point target imaging,a compressed sensing(CS)imaging method is proposed.The imaging performance of different CS algorithms for multi-target is analyzed and compared.Compared with the traditional range doppler algorithm(RDA),the results show that the proposed method can obtain higher azimuth resolution and is robust to noise.In this thesis,an imaging method for gaze and SAR scene electromagnetic vortex radar is designed,the MUSIC and CS are used to improve the performance of the method,and TMCA is applied to reduce the cost and complexity of radar,it not only solves the urgently key problems of electromagnetic vortex radar technology,but also provides a useful reference for the new system of radar imaging technology,which is helpful to promote the technical development in this field.