Research On ISAR Imaging Technology Based On Frequency Diversity Array

Inverse Synthetic Aperture Radar(ISAR)can provide all-time and all-weather imaging of moving targets at long distances.The azimuth resolution obtained by ISAR is different from other radars,and it is essentially obtained through the relative motion between the radar itself and the target using synthetic aperture technology.Considering that the Frequency diversity Array(FDA)can obtain the advantage of broadband observation performance by transmitting single frequency signals,but has the disadvantage of not having the ability of beam pointing,this paper will apply a continuous directional beam technology to enable FDA and ISAR to better conduct joint imaging,and then use different imaging algorithms,based on the full use of radar system resources,To achieve the goal of improving the imaging quality of moving targets.This article conducts in-depth research on ISAR imaging technology based on the characteristics of ISAR and FDA.The main research content is as follows:(1)Firstly,the basic principles of ISAR imaging were introduced from the perspective of model structure.By establishing a model,the spatial geometric relationship between ISAR and the observed target was visually displayed.Classic target translation compensation methods,the conversion of ISAR small angle motion modes,and the resolution of the ISAR system were introduced;Next,the basic model,working principle,and characteristics of the beam pattern of FDA were explained,and some common decoupling methods were given for the distance angle coupling characteristics of FDA.Finally,different reception methods of array echo signals were introduced to some extent.(2)In response to the problems of low accumulated reflection energy and poor imaging quality of moving targets in traditional FDA ISAR applications,this paper constructs an FDA-ISAR imaging system based on continuous directional beam technology and derives an echo signal model,laying the foundation for the subsequent application of imaging algorithms and achieving high-quality two-dimensional images of FDA-ISAR targets.Analyzed the performance of continuous directional beams and the related radar imaging system resolution,providing a certain reference for the subsequent analysis of the application effect of imaging algorithms.(3)In order to improve the quality of moving target imaging,this paper uses twodimensional Fourier transform algorithm,back projection(BP)algorithm and orthogonal Matching pursuit(OMP)algorithm in the echo signal processing.When using the twodimensional Fourier transform algorithm for imaging,the imaging results without the use of continuous directional beam technology were compared.Through simulation,it was verified that the continuous directional beam can achieve high energy accumulation when used for radar system imaging;In order to improve the imaging quality of the radar system for multiple moving targets and ensure that each target can achieve the same imaging effect,this paper uses the BP algorithm to image the targets in this radar system and analyzes the simulation results accordingly;Finally,aiming at the multi sidelobe problem after the BP algorithm imaging,this paper uses the OMP algorithm based on compressed sensing,and the simulation results show that the OMP algorithm effectively suppresses the sidelobe interference,making the imaging quality of moving targets better.