Near-field Radar Three-dimensional Imaging Based On Irregular Aperture

Near-field synthetic aperture radar(SAR)mostly works in the millimeter-wave frequency band.Compared with far-field SAR such as spaceborne,airborne and missile-borne SAR,it has the advantages of miniaturization,high resolution and wide bandwidth,which is suitable for perceiving and imaging of near-field targets.And it is widely used in the fields of autonomous driving,safety inspection,and joint radar sensing and communication.Near-field radar three-dimensional imaging technology,which refers to forming a virtual two-dimensional array based on the principle of synthetic aperture and equivalent phase center in a near-field environment,improving resolution in azimuth and height and combining with wide bandwidth in range,realizing three-dimensional imaging of targets.However,in the near-field environment,the miniaturized radar system has the characteristics of arbitrary motion,which will cause the irregular synthetic apertures,resulting in uneven and sparse sampling of echos,seriously affecting three-dimensional imaging quality of the target.This paper focuses on the linearization method of irregular aperture and the radar three-dimensional imaging method under two-dimensional sparse mode.The main work is as follows:1.Irregular aperture three-dimensional model of near-field SAR echo is established,the judgment conditions of near-field environment are derived,the compensation method for the wavefront curvature is studied.Meanwhile,the phase characteristic of radar echo based on irregular aperture is analyzed.which lays a theoretical basis for the subsequent imaging processing of echo signals.2.The conventional near-field radar three-dimensional imaging algorithm,Range Migration Algorithm,is studied.The influence of irregular aperture on the near-field radar three-dimensional imaging is analyzed.And the imaging performance of irregular aperture and regular aperture are compared.3.A irregular aperture linearization method base on minimum two-norm is proposed,which solves the problem of uneven sampling caused by irregular apertures.And the sparse modes of sampling data after aperture linearization are analyzed.A height sparse sampling radar three-dimensional imaging method based on compressed sensing is studied,and height sparse sampling three-dimensional imaging with irregular apertures is realized.4.A sparse sampling radar three-dimensional imaging method based on principal component enhancement matrix completion is proposed,which solves the two-dimensional sparse sampling problem after apertures linearization,and improves the recovery reliability of two-dimensional sparse radar echo signals.Then two-dimensional sparse sampling three-dimensional imaging with irregular apertures is achieved.The effectiveness of the above methods is verified by theoretical analysis,simulation experiments and physical test data,indicating that the above methods can realize the irregular aperture radar near-field 3D imaging.