Research On High Resolution SAR Imaging Technology Based On Vortex Electromagnetic Wave

Because of the spiral phase wavefront,the vortex electromagnetic wave with orbital angular momentum can bring more freedom for information modulation and greatly increase the ability of information acquisition.Orbital angular momentum,as one of the most basic physical quantities of electromagnetic fields,can theoretically generate an infinite variety of mutually orthogonal modulation modes.Therefore,the orbital angular momentum diversity multiplexing technology has very attractive application prospects in wireless communication and radar detection.As the most widely used practical radar system,Synthetic aperture radar(SAR)can synthesize a long antenna aperture to achieve high-resolution imaging by using the movement of radar platform such as aircraft or satellite.If the vortex electromagnetic wave can be applied to SAR imaging system,not only the problem that the vortex antenna can’t be moved and the practicability is not strong can be solved,but also the higher electromagnetic imaging resolution can be obtained,and it is expected to solve the problem that the ordinary SAR can’t achieve imaging in three-dimensional space and can’t reach the target pitch angle.Based on this,this paper explores the application of vortex electromagnetic waves in SAR imaging systems.The principles of electromagnetic vortex radar imaging,vortex electromagnetic wave SAR imaging system models,vortex SAR signal echo equations,vortex electromagnetic wave SAR imaging algorithm design and the three-dimensional spatial imaging capability of electromagnetic vortex SAR has been studied in depth.The design ideas,technical methods and imaging advantages of vortex electromagnetic waves used in SAR imaging systems are analyzed.At the beginning of this paper,we introduce the background and significance of the subject,the concepts and theoretical knowledge related to orbital angular momentum and vortex electromagnetic wave,and then analyzes the high-resolution imaging principle of two kinds of electromagnetic vortex radar.Different from the ordinary plane electromagnetic wave,the phase wavefront of vortex electromagnetic wave is no longer the ordinary plane,but presents a spiral structure of periodic steps.When applied to radar imaging,it can easily provide the phase difference needed for azimuth resolution,and realize the range azimuth two-dimensional imaging without relative motion,which is the principle of real aperture radar staring imaging.In synthetic aperture radar,the echo signal with the property of vortex electromagnetic wave shows a wider effective beam width than the ordinary plane wave signal,which is the macroscopic performance of the extraordinary information acquisition ability of vortex electromagnetic wave carrying orbital angular momentum.Based on the theory of vortex electromagnetic wave correlation and the imaging principle of electromagnetic vortex SAR,the imaging verification experiment of electromagnetic vortex SAR is carried out.Based on the increasing phase uniform circular array antenna vortex electromagnetic wave receiving and transmitting mode,three imaging models of electromagnetic vortex SAR are established,and the echo equation is deduced.In view of the new orbital angular momentum correlation term in the echo equation,the traditional back projection algorithm is improved,which effectively compensates the impact of the new term on the imaging results.Through the simulation experiment,the azimuth imaging performance of electromagnetic vortex SAR is verified,and the improved algorithm is applicable to the imaging scene with a certain overlap of scattering centers of multiple targets,which is robust to noise.In addition,the vortex electromagnetic wave signal has a certain spatial resolution,so the SAR system that transmits the vortex electromagnetic wave to detect the target can realize the target imaging in three-dimensional space through certain algorithm design,this paper studies this.Combining the method of electromagnetic vortex staring imaging with SAR system,the azimuth information of the target is obtained by using the similar method of staring imaging,and the slant distance and track information of the target are obtained by using the two-dimensional imaging method of electromagnetic vortex SAR,and the improved CS algorithm is proposed for imaging processing.Finally,through coordinate transformation and angle relationship,the elevation information of the target is obtained,and the three-dimensional space imaging of the target is realized.In this paper,electromagnetic vortex technology is applied to SAR imaging,which provides an effective scheme for high resolution azimuth imaging and three-dimensional space imaging of SAR.The research work of this paper will promote the application of electromagnetic vortex in radar field,and provide reference for the development of new radar technology.