| Distributed Multiple Input Multiple Output(MIMO)array radar uses transceiver diversity technology to form multiple transceiver antenna pairs,so as to independently process the signals of each channel,thereby reducing the interference between signals and optimizing the performance of target parameter estimation.At the same time,the radar can also synthesize a large virtual antenna aperture to improve azimuth resolution,so distributed MIMO array radar plays an extremely important role in target detection and imaging.Distributed MIMO array radar is based on MIMO virtual aperture technology,which equates real arrays to form virtual arrays to achieve detection and sensing of targets.The radar mostly adopts sparse array arrangement,although this method can increase the virtual antenna aperture,however,the generated grating lobe will greatly affect the imaging results,so the suppression problem of grating lobe is of important research significance.This thesis addresses the grating lobe suppression problem of distributed MIMO array radar.The theoretical research and simulation verification are conducted around the echo modeling and characterization,array optimized grating lobe suppression,and image domain grating lobe suppression of this radar.The main work is as follows:(1)The echo model of distributed MIMO array radar is established,The basic principle of this radar and the target estimation and detection algorithm are analyzed,the virtual aperture technique of distributed MIMO radar is studied,and the mechanism of grating lobe generation is analyzed in detail,which lays the foundation for the subsequent research on the method of grating lobe suppression.(2)Improved the method of grating lobe suppression based on array optimization,transformed the grating lobe suppression problem in array design into an optimization problem and solved it using particle swarm algorithm,improved the design criterion of parameters and the selection of fitness function,obtained the optimal array configuration for grating lobe suppression.The optimal array configuration is verified using DOA(Direction of arrival)spectral estimation and CFAR detection algorithm,and the problem of grating lobe suppression in the radiation diagram is solved,which is based on the distributed MIMO array radar array optimization method.(3)The method of grating lobe suppression in the image domain of distributed MIMO array radar is proposed.By analyzing the echo superposition characteristics of the grating lobe and the main lobe and the phase difference between them,the coherence factor is derived and the amplitude in the imaging process is weighted to solve the problem of false targets caused by the grating lobe in MIMO array radar imaging,and the image domain grating lobe suppression of distributed MIMO array radar is realized.The proposed methods are validated by simulation experiments or real measurement data,and the results show that the proposed methods are effective and feasible in grating lobe suppression of distributed MIMO array radar. |
