Passive Radar Research Based On OFDM Signal

With the rapid development of electronic technology,passive detection technology has been applied to many fields such as passive radar,ocean exploration and seismology.Passive radars that use opportunistic lighting have a natural advantage in resisting the"four major threats"because they do not emit electromagnetic signals.In recent years,research in this field has received extensive attention from radar scholars in various countries.At present,in the field of broadband digital communication,Orthogonal Frequency Division Multiplexing?OFDM?transmission technology is applied in many fields,such as wireless networks,4G mobile communication,Digital Video Broadcasting?DVB?,and Digital Audio Broadcasting?DAB?,so that OFDM signals can be used to provide passive radar opportunitie illumination.This paper studies passive radar technology based on OFDM signals..The main work in this thesis contains:1.At first,we introduce the traditional active radar and passive radar systems separately,and analyze the similarities and differences.The characteristics and advantages of the passive radar system in the target detection field are introduced in this chapter.At the same time,we introduce the characteristics and advantages of passive radar systems.Then,a brief overview of OFDM technology is introduced.In order to solve the problem of single carrier frequency system,we introduce multi-carrier frequency technology.After that,the advantages of OFDM technology in multi-carrier frequency technology were found in the analysis of multi-carrier frequency technology.Finally,according to the basic principle of radar,the characteristics of OFDM signal in passive radar system are descriped.This article introduces several commonly used OFDM signals,and we compare the range resolution,doppler and velocity resolution,and analyze their performance in detail;The theoretical power range of passive radar is derived by the bistatic radar equation,and the feasibility of OFDM signal as a third-party radiation source for passive radar is proved.2.In order to solve the problems of direct wave and multipath interference in the target echo,this paper studies the interference cancellation method based on extended association?ECA?technology:This thesis constructes a bistaic application scenario,and theoretically derived from the two key angles of OFDM signal form and OFDM signal processing to construct a passive radar system based on OFDM system.Without considering the demodulation error,we establish a two-dimensional cross-correlation function model to estimate the delay and Doppler frequency parameter information.The clutter suppression performance of the algorithm is analyzed by simulation experiments,and the effectiveness of ECA algorithm in the application of passive radar system is verified.3.Aiming at the base mismatch problem in joint delay doppler estimation of moving targets,we compare the traditional MUSIC and compressed sensing algorithms,and proposed the compressed perceptual algorithm based on atomic norm which uses atomic norm and ₁l-norm to achieve Super resolution.Among them,the atomic norm is used to represent signal sparsity in a continuous domain.Unlike the previous assumption that demodulation has no error,considering the demodulation error,its sparsity is represented by a ₁l-norm.On this basis,the delay and Doppler frequency are estimated by solving the convex semidefinite programming?SDP?problem.In the simulation experiment of multi-objective environment,with under the direct wave and clutter interference,the algorithm can detect multiple weak targets,which verifies the effectiveness of this method.