Study Of MIMO Radar Waveform Design And Application And Distributed Coherent Transmission

Waveform design is an important issue in Multiple-Input Multiple-Output(MIMO)radar research field.According to the configuration of the antennas,the MIMO radar is generally classified into two types: MIMO radar with colocated antennas(colocated MIMO radar)and MIMO radar with widely separated antennas(distributed MIMO radar).For colocated MIMO radar,desired transmit beampattern can be obtained by waveform design,thus improved search efficiency of the surveillance space and utilization efficiency of energy and time resources can be achieved.For distributed MIMO radar,the spatial diversity ability can be obtained by orthogonal waveforms design,thus improved target detection performance and localization accuracy can be achieved.By the study of waveform design for MIMO radar,lots of waveforms have been obtained,which provides the condition for the extended application of MIMO radar waveforms.Besides,when tracking important targets,the distributed MIMO radar can work in coherent transmission mode to improve the tracking performance and discrimination capability.Therefore,this dissertation focused on the MIMO radar transmit beampattern design and orthogonal waveforms design,pulse agility technique based on MIMO radar waveforms,and distributed MIMO radar coherent transmission theory.The main content of this dissertation is summarized as follows.1.Transmit beampattern design for colocated MIMO radar is studied.Firstly,waveform design criteria with the objective functions to match a desired transmit beampattern and to suppress the Auto-correlation Peak Sidelobe Level(APSL)and Peak Cross Correlation Level(PCCL)of the illuminated waveforms in the spatial direction(angular waveforms)are established,where two transmit beampattern matching methods are used.Then,receiving beamforming is introduced into the above waveform design process.Because of the suppression of the cross correlation level of angular waveforms by the receiving beamforming,there are more degrees of freedom in the waveform design process to match the desired transmit beampattern and to suppress the auto-correlation sidelobes of angular waveforms.Therefore,a better transmit beampattern matching result and lower APSL and PCCL of angular waveforms are achieved.Finally,transmit beampattern design method based on unequally spaced sparse linear array is proposed.Joint design criteria to design element positions of transmit array and waveforms simultaneously are constructed,by which a larger transmit array aperture is obtained and a better transmit beampattern matching result and lower APSL and PCCL of angular waveforms are achieved for more degrees of freedom.2.Design of orthogonal waveforms for distributed MIMO radar is studied.In order to further decrease the APSL and PCCL of orthogonal waveforms,firstly,a waveform design criterion with the objective function to minimize the APSL and PCCL of orthogonal waveforms is established.And then the waveform design criterion is rewritten,so that the least-pth algorithm can be used to solve this optimization problem.Numerical results indicate that,compared with the present algorithms,lower APSL and PCCL are achieved by the least-pth algorithm.For the Doppler sensitivity of orthogonal phase coded waveforms,auto-correlation sidelobes will increase if there is a Doppler mismatch,but an analysis indicates that the increased sidelobes can be suppressed by the waveform design method.Therefore,a construction method for orthogonal phase coded waveforms with low Doppler sidelobes is proposed.A phase coded waveform with low Doppler sidelobes is designed firstly,and then a set of orthogonal phase coded waveforms with low Doppler sidelobes is constructed based on this waveform.3.Pulse agility technique of monostatic radar based on MIMO radar waveforms is proposed.Firstly,the signal model of range-Doppler sidelobes after coherent integration under random transmitting mechanism for pulse agility technique with MIMO radar waveforms is derived,and the performance of pulse agility technique with MIMO radar waveforms is analyzed in theory.Secondly,for a lower range-Doppler sidelobe level,given a set of MIMO radar waveforms,a design criterion of transmission order is established.Thirdly,for the pulse agility technique,its waveform design method is proposed,and a joint design criterion of waveforms and transmission order is constructed,which can further decrease the range-Doppler sidelobe level.Finally,for a better optimization performance,a waveform design criterion with a given transmission order is further proposed based on the joint design criterion.4.The theory and performance of coherent transmission for distributed MIMO radar is studied.Under the distributed coherent transmission mode,the signal model of the signal in the space after transmission of the distributed radars is derived,and a spatial interference energy distribution function is defined to show the energy level in the space after coherent transmission.The spatial interference energy distribution function is also given when phase errors exist for distributed radars.Based on the spatial interference energy distribution function,the maximum gain of the energy after distributed coherent transmission is obtained,and the conditions to form an interference peak and the distribution of the interference peaks in the space are analyzed in theory.The effects of the number and location of the radar to the shape and distribution of interference peaks are studied by numerical simulations.