Passive Distributed Aperture Radar Imaging Method Applicable To Non-cooperative Illuminator

Passive radar itself does not radiate electromagnetic waves outward,but uses external illumination sources for detection and tracking.Therefore it has good electronic countermeasures characteristics,at the same time it can save system cost and frequency band resources.In passive distributed aperture configuration,each transmitting unit and receiving unit can be arbitrarily distributed,and the spacing of array elements can be hundreds or thousands of times of wavelength,which is suitable for the flexible configuration of radar.With the development of society,the number of external illuminators of opportunity,such as radio signal,television signal,mobile communication signal,satellite navigation signal and wireless network signal,has greatly increased.Especially in cities and their surrounding areas,the distribution of illuminators is more intensive.Passive radar detection technology using external illuminators has once again become a research hotspot in the field of radar.This paper studies passive distributed aperture radar imaging methods for non-cooperative illumination sources.First of all,this paper briefly introduces the general situation of passive radar and its imaging technology,analyses the related research trends at home and abroad,and also gives the research background,significance and main contents of this paper.Secondly,this paper studies the method of distributed aperture radar compressive sensing(CS)imaging based on passive echo model.Most of the existing passive imaging methods generally need to set up auxiliary channels or special receivers to receive direct wave signals from the irradiation source.The passive echo model does not need the waveform information of the transmitting source.It chooses a receiving unit as a reference,and describes the echo signals of all other receiving units with the received signals of the reference unit.The scene satisfies the sparse characteristics because the number of moving objects in the scene is limited.The CS method can use far less samples than the request of Nyquist sampling theorem to realize the imaging and velocity estimation of moving objects.The simulation results show that the method is effective.Thirdly,the passive radar imaging method considering residual direct wave is studied in detail.Aiming at the residual problem of direct wave suppression,passive imaging method is studied on the basis of generalized Likelihood Ratio Test(GLRT).Assuming that the correlation of emission waveforms is known,the non-linear estimation of amplitude and noise variance in the imaging model is solved by Expectation Maximization(EM)algorithm.Then,from the GLRT theory,the image ofthe area is constructed by the spatial resolution test statistics.The effectiveness of this method is verified by simulation experiments.Then,the passive distributed aperture radar imaging method based on unknown waveform modeling is studied.Based on the consideration of the residual direct wave,this paper also studies a passive distributed aperture radar imaging method using the correlation of transmitted waveforms.The correlation of transmitted waveforms is unknown.By modelling the unknown signal transmitted by the illuminators of opportunity as an autoregressive(AR)process,the time correlation is estimated and applied to passive imaging.Then,from the GLRT theory,the correlation of emission waveform and unknown parameters in imaging model are estimated jointly by EM algorithm,and the image of the area to is composed of spatial resolution test statistics.The effectiveness of this method is verified by simulation experiments.Finally,for the conclusion,the work of the paper is summarized,and the problems that still need to be further studied and solved are pointed out.