Study On The Beampattern Optimization For Multiple-Input Multiple-Output Radar

Multiple-input Multiple-output (MIMO) radar is a new radar system, which utilizes multiple antennas at both the transmitting side and the receiving side. Compared with traditional phased-array radar, which transmits scaled versions of waveform, MIMO radar transmits orthogonal or partially correlated waveforms from each antenna in the transmitting side, and in the receiving side all the signals are extracted by matched filtering. Compared with bi/multi-static radar, MIMO radar jointly processes all the transmit-receive information. All of these can improve the performance of MIMO radar. Till now, the study on MIMO radar mainly includes colocated MIMO radar, distributed MIMO radar and waveform design. In this dissertation, we will focus on how to optimize the beampattern of MIMO radar.Colocated MIMO radar can be treated as an extended type of phased-array radar, in which the antenna arrays in the transmitting side and the receiving side are all traditional. Therefore, the beampattern optimization for colocated MIMO radar is how to obtain a narrower mainlobe beamwidth and a lower sidelobe level.Distributed MIMO radar can be treated as an extended type of bi/multi-static radar, in which the antennas are widely separated. The widely separated antennas can obtain not only the diversity gain, but also a wider field of view or aperture length. The diversity gain can overcome the target radar cross section (RCS)"fluctuation"and improve the target detection ability. The longer aperture length can improve the target resolution at the cost of high sidelobes or grating lobes in the transmit-receive beampattern. Therefore, the beampattern optimization for distributed MIMO radar is how to suppress the high sidelobes or grating lobes.Considering the aspects mentioned above, the following achievements have been obtained:Based on the model of colocated MIMO radar, a generalized transmit-receive beampattern for MIMO radar is given, the relationship between MIMO radar virtual aperture and the transmit-receive beampattern is analyzed, a new minimum sidelobe level design method for MIMO radar is proposed.Based on the model of distributed MIMO radar, a hybrid signal processing mode is proposed. The hybrid mode combines the non-coherent processing with the coherent processing, which can improve not only the ability of target detection but also the target resolution.Combined frequency diversity with MIMO radar, a new beampattern optimization method for coherent processing distributed MIMO radar is proposed, the restriction on the selection of frequency offset is analyzed, the effectiveness of the grating lobes suppression using frequency diversity is demonstrated;The paper has also studied on the distributed small-satellites GMTI method based on frequency MIMO radar beampattern optimization, and electronic reconnaissance technology based on two satellites with sparse aperture equipments.