Research On Imaging Methods For Multi-channel Circular Synthetic Aperture Radar

Radar imaging was originally an imaging technology produced to meet military needs.Because it can work all day and around the clock and is not easy to be constrained by environmental factors like optical imaging,radar imaging technology has also been steadily developed and widely used.But the original radar was real-aperture radar which required large dimensions for high-resolution.With the improvement of imaging quality and imaging cost requirements,some scholars have proposed high-resolution SAR imaging technology that combines small antenna motion into large aperture.However,the trajectory of traditional SAR is a straight line,the shape of its frequency domain is a fan,and the spectrum information is not rich enough,so the resolution of the azimuth direction is limited.In addition,it can only realize two-dimensional imaging.Therefore,some scholars have proposed models such as linear array synthetic aperture radar(LASAR)and curvilinear synthetic aperture radar(CLSAR)that can realize three-dimensional imaging.The trajectory of the Circular Synthetic Aperture Radar(CSAR)in the curvilinear synthetic aperture radar is circular,and the shape of its three-dimensional spatial spectrum is a circular truncated cone.Therefore,it has higher azimuth resolution and can realize three-dimensional imaging.Circular SAR has become a hot spot in SAR imaging research in recent years.But its research time is short,technology is not mature,and has great prospects for development and research.For example,its higher side lobe level is a problem to be solved in circular SAR imaging research.In this paper,near-field millimeter-wave circular track SAR imaging is studied.A multi-channel circular SAR model is proposed,and an improved multi-channel circular SAR system with lower cost is designed.This system can realize side lobe suppression,effectively avoiding the submerged weak targets and imaging the false targets in imaging,make the imaging result more accurate,and obtain higher imaging quality.The main work is as follows:1.Basic research:The knowledge of traditional SAR imaging is briefly introduced.The two-dimensional imaging mechanism of SAR and its high resolution imaging principle are understood.The computer simulation imaging of SAR is carried out by back projection(BP)algorithm,which lays a foundation for the research of back projection algorithm of circular SAR.After understanding the circular SAR model,the echo model is correctly established and the target scene which we set is imaged by the backward projection(BP)algorithm.The side lobe level of the imaging result is recorded and analyzed in order to compare with the imaging result of the subsequent algorithm.2.Innovative inquiry:Real-aperture radar has abundant spectrum information,so its side lobe is low.In order to solve the problem of high side lobe in circular SAR imaging,the real aperture radar imaging model can be used for reference.Real Aperture Radar(SAR)is a kind of array radars arranged in a certain way,so the emphasis is turned to the construction of array radars,and then a multi-channel circular SAR model analogous to real Aperture Radar is proposed.By simulating the multi-channel circular SAR of the radar equidistant arrangement,the side lobe suppression ability of the system is confirmed,and a multi-channel circular SAR system with improved radar arrangement is proposed at a lower cost,and then its side lobe suppression ability is also confirmed by imaging simulation.In a word,this paper studies the backward projection(BP)algorithm for multi-channel circular SAR.Based on the theory of imaging,the feasibility and superiority of the improved multi-channel circular SAR backward projection(BP)algorithm to reduce the side lobe level are verified from geometric models to simulation experiments.The research effectively alleviates the false target imaging,reduces the risk of the weak target being submerged,improves the anti-interference ability of the radar imaging system,and has important significance for the practical application of radar imaging such as target detection and recognition.