Research On Angular Super-Resolution Method Of Airborne Radar Forward-Looking Imaging

Airborne radar can obtain real beam images of the forward-looking area through beam scanning,and has broad application prospects in military reconnaissance,aircraft landing,and material airdrops.However,due to the limitation of antenna beam width and radar range,its azimuth resolution is usually very low.The forward-looking angular super-resolution method refers to improving the angular resolution of the forward-looking real beam image through signal processing,which has become a research hotspot in recent years.This thesis focuses on the echo model,the influence of point spread function,the space-varying super-resolution algorithm and the coherent super-resolution method involved in the research of airborne radar forward-looking angular super-resolution,and it mainly includes the following work:1.According to the working mode of airborne radar forward-looking scanning,the echo model is established,the echo law is analyzed,the azimuth convolution relationship is derived,the applicable conditions are analyzed,and the ill-conditioned nature of the deconvolution problem is revealed,which will provide theoretical guidance for the subsequent research.2.A modified raised cosine function is constructed to simulate the antenna pattern and control its main lobe width and side lobe level,and the influence of antenna main lobe width and side lobe level on convolution matrix condition number and Fisher information is evaluated.Furthermore,the impact of different antenna patterns on different super-resolution algorithms performance is evaluated through simulation,so as to provide a theoretical basis for the selection and design of antenna patterns.3.Aiming at the problem of spatial variation of the azimuth point spread function(PSF)in the forward looking scanning area,,the law of spatial variation is analyzed,and a space-variant angular super-resolution algorithm for forward-looking scanning radar based on PSF decomposition is proposed.First,the singular value decomposition of the point spread function is performed to obtain the base PSF,and then the total variational regularization model is established,and the iterative problem-solving method based on the Alternating Direction Method of Multipliers(ADMM)is studied,and finally,angular super-resolution was achieved under the condition of spatially variable point spread function.4.To address the issue of noise sensitivity in conventional super-resolution methods,a coherent super-resolution imaging method is proposed.This method effectively achieves azimuth super-resolution within one beamwidth in the forward looking area by designing an antenna illumination function that contains nonlinear phase changes in the antenna pattern,and combining it with azimuth matching filtering.