| Distributed MIMO radar,as a new type radar system,has great potential advantages in coverage of radar network system and anti-stealth performance,target parameter estimation,low probability of interception performance,clutter suppression,and antijamming.It is one of the development trends of modern radar system technology.Airborne distributed generally refers to the application of distributed MIMO radar to plane-borne,missile-borne and other platforms,and coordinated operations through multiple radars in the air combat area,greatly improving the overall radar detection capability.In this thesis,the key technologies such as target positioning,velocity estimation,waveform design and coherent parameter estimation of airborne distributed MIMO radar are studied.The main research contents of the thesis are as follows:1.The basic working principle and performance of distributed MIMO radar are introduced.The content includes system composition,basic working process of transmission and reception,basic signal model,signal processing process,and based on the comparison of various parameters with traditional phased array radar,the advantages of distributed MIMO radar are summarized。2.The target positioning problem of the air distributed MIMO radar is studied.By using different types of information at the same time,including time delay,Doppler frequency shift,azimuth angle and elevation angle of arrival,algebraic closed-form twostage weighted least squares solution are studied.It also shows the proposed algorithm to obtain Cramer lower bound accuracy under the assumption of small Gaussian noise.Simulations are included to examine the algorithm's performance,and the results show that CRLB accuracy can be achieved well under low noise conditions.3.The waveform design method of aerial distributed MIMO radar is studied,and the basic principles and methods of orthogonal waveform design are discussed.For the design of orthogonal phase encoding waveforms,by summing up the traditional genetic algorithm and simulated annealing algorithm,a genetic simulated annealing algorithm combining the advantages of the two algorithm is proposed,and a set of orthogonal poly phases code with better autocorrelation and cross-correlation levels are designed.For discrete frequency-coding waveforms,a design method using a combination of linear coding and PN-code is proposed,and a set of optimization processes consisting of two stages are proposed.Finally,a set of discrete frequency-coding waveforms with better performance is obtained,which can effectively optimize the autocorrelation and crosscorrelation level of the waveform.4.The two coherent working modes of the airborne distributed MIMO radar system are studied,namely,transmitting coherent and transmitting and receiving full coherent,and then the estimation method of coherent parameters is studied,and the mathematical model of parameters estimation is proposed.At the coherent working mode,different parameters estimation methods are proposed: coherent parameters estimation based on orthogonal signals and coherent parameters estimation based on coherent signals.Then,the Cramer-Rao lower bound(CRLB)of the two estimation methods is derived,and the performance analysis is performed through simulation,and the requirements of the two coherent estimation methods on the SNR are proposed.Study of the two coherent parameters estimation methods provides the theoretical support for the realization of the coherent working modes of airborne distributed MIMO radar. |
