Research On Radar Azimuth Super Resolution Technology Based On Vortex Electromagnetic Wave

The vortex electromagnetic wave carrying the orbital angular momentum(OAM),which has a special spiral wavefront phase structure and infinite variety of orthogonal modes,provides a new dimension for the electromagnetic wave transmission information.Vortex radar can distinguish multiple targets within the beam by emitting vortex electromagnetic waves,which can solve the pain points that real aperture radar cannot distinguish targets in the beam and synthetic aperture radar relies on relative motion and cannot forward-looking imaging.The azimuth super-resolution technology of vortex electromagnetic wave radar refers to using the phase difference of echoes of different OAM modal numbers,using super-resolution algorithms such as spectral estimation and sparse recovery algorithms to realize vortex radar azimuth super-resolution in the case of the small number of modes and missing modes.In this thesis,the research work is carried out on the azimuth super-resolution in the vortex radar gaze scene.Firstly,the vortex radar system model is established based on the uniform concentric array and the echo expression is deduced.Then,the azimuth superresolution algorithm of the vortex radar based on the iterative adaptive approach and sparse learning via iterative minimization algorithms is studied.Finally,a missing mode recovery algorithm based on the linear minimum mean square error is proposed.The main contents are as follows:1.Research on the azimuth resolution mechanism of vortex radar.The purity of OAM modes under different array arrangements is analyzed.The effects of different array parameters on the vortex electromagnetic wave radiation field under the uniform annular array are compared.The scattering characteristics of vortex electromagnetic waves under an ideal scatterer target is studied,and the case of missing modes when the vortex radar receives the echo is demonstrated.2.The vortex radar echo model is established,the azimuth theoretical resolution of the vortex radar is analyzed,the interference caused by the Bessel function in the echo equation is compensated,and the relationship between the azimuth main lobe width and the OAM mode number is determined,which lays a foundation for the subsequent comparative study of vortex radar azimuth super-resolution algorithms.3.The azimuth super-resolution algorithm of vortex radar in the staring scene is studied.For the problem that the azimuth resolution of the vortex radar requires a large number of modes,the algorithm of parametric spectral estimation,non-parametric spectral estimation,and sparse reconstruction are used respectively.These methods achieve a finer azimuth resolution ability in a small number of modes.4.An algorithm for improving the super-resolution performance of vortex radar in missing modes is proposed.Aiming at the problem of poor azimuth resolution accuracy and high sidelobes caused by echo missing modes,a missing mode recovery algorithm based on linear minimum mean square error is proposed,which has better recovery accuracy than the gradient descent algorithm and achieves a more robust azimuth resolution ability while suppressing sidelobes under the case of missing modes.The above research work has been verified by several independent Monte Carlo experimental simulations.The experimental results show that the research work in this thesis can achieve robust azimuth super-resolution performance of vortex radar in a small number of OAM modes.