Research On Localization Method Of Subsurface Target Based On Parameter Estimation Of MIMO Radar

Since multiple-input multiple-output(MIMO)technology was introduced into radar field,it has become a research hotspot because of its many advantages.The parameter estimation algorithm based on MIMO radar has gradually matured.However,most of these algorithms are based on far-field.For near-field conditions,especially for near-subsurface target,there are few studies on it.Moreover,the single-input multiple-output(SIMO)system used in traditional subsurface target detection has limited amount of information,and it is difficult to obtain a qualitative improvement due to interference of various factors.Therefore,it is of great significance to study the localization method of near-subsurface target based on MIMO radar.In addition,in the research of new radar system,frequency diverse array(FDA)radar has gained wide attention with its unique advantages.However,the research on FDA radar,whether waveform design or target localization,are limited to far-field at present.Therefore,it is of pioneering value to explore the application of FDA radar in near-subsurface condition.Aiming at the above problems,this paper studies the subsurface target localization method of conventional MIMO radar,and explores the near-field theory and subsurface target localization method of FDA-MIMO radar which combines MIMO radar and FDA radar,based on the analysis of signal model.The main work of this paper is summarized as follows:1.To deal with the issue of inverse direction target localization method of conventional linear array MIMO radar can't effectively locate multi-targets with different distances,a new approach of reverse direction target localization based on symmetric sub-array MIMO radar is proposed.It reconstructs the received signals of the sub-array by using the particularity of symmetric structure.The reconstructed signal can realize the DOA estimation without distance dependence,and then the reverse direction target localization with different distances can be realized.The effectiveness of the proposed method is verified by simulations.2.According to the localization mechanism of the reverse direction target localization algorithm of the symmetrical sub-array MIMO radar,it can be optimized from two aspects: localization accuracy and efficiency.According to the core of accuracy of the proposed algorithm is DOA estimation,the localization accuracy can be improved by using a more accurate DOA estimation algorithm.According to the large amount of redundant data in the application space of the proposed algorithm,an optimization algorithm based on spatial segmentation is used to improve the localization efficiency.The effectiveness of the proposed optimization methods is verified by simulations.3.In view of the advantages of FDA-MIMO radar in target localization,and the existing researches are limited to far-field,this paper attempts to introduce it into near-subsurface target detection.Firstly,the near-field theory of FDA-MIMO radar is studied.The point spread function(PSF)of FDA-MIMO and conventional MIMO radar in near-field is compared and analyzed.The simulation results of PSF show that FDA-MIMO radar can effectively suppress side lobes in azimuth direction and range direction,and has better resolution in range direction,compared with conventional MIMO radar.Then,to deal with the issue of single frequency offset will lead to the imbalance of PSF image in near field,a symmetrical dual frequency offset method is proposed.Finally,the two dimensional beam scanning method is used to realize the subsurface target localization of the FDA-MIMO radar.The simulation results show that the FDA-MIMO radar has higher localization accuracy and imaging effect than the conventional MIMO radar.