Study On Waveform Design For MIMO Radar Based On Radar Tasks

With the development of radar theory, especially signal processing algorithm andtechnology, enhancing radar performances by updating signal processing algorithm inradar receiver become more and more difficult. The research interest turns to transmitterfor the fact that waveform design and optimization can also enhance radar detectingperformance. Via alternating waveform according to the changing environment, theperformace of detecting, tracking and inference suppression is adaptively optimized andthe effects of electronic scouting and inference from enemy are reduced. Multiple-InputMultiple-Output radar has become a hotspot in radar technology. The transmit andreceive antenna of MIMO radar are configured flexibly according to systemrequirement and each unit transmits different waveform, in this way better performancesof low probility of interception, detecting target with low RCS, clutter suppression andtracking are obtained. Waveform design and optimization is crucial means to utilize theadvantages of waveform diversity of MIMO radar. Although many scholars haveinvestigate into MIMO radar waveform design algorithms and a number ofachievements have been acquired, there are still many problems to be solved, especiallyin the fields of waveform design and optimization for different specific applications.Based on previous work and combined with my research jobs at present, thisdissertation focuses on the waveform design and optimization algorithms for co-locatedMIMO radar tasks, including orthogonal waveform design, beampattern andtime-domain signal synthesis, adaptive waveform design for detecting and tracking. Themain contents of this dissertation are summarized as follows:Firstly，basic method for radar waveform design is analyzed. The ambiguityfunctions of the waveforms menthioned in the thesis are introduced to analyse theperformances of their range and Doppler resolutions. The relation betweenfrequency-domain waveform and detection performance is studied in maximumsignal-clutter-and-noise ratio rule. Energy spectrum density of optimum waveform isdeduced under energy constraint, based on that, a quick waveform design method fortime-domain frequency modulation signal is introduced.Focused on orthogonal waveform design and related signal processing for MIMOradar, a novel method for orthogonal phase-coded waveform design and related adaptivepulse compression filter are introduced. To minimize the auto-correlation sidelobe andcross-correlation, a multi-objective evolutionary algorithm based on decomposition isintroduced. The algorithm decomposes muti-objective optimization problem into a number of scalar optimization subproblems and optimizes them simultaneously. Eachsubproblem is optimized by using information from several neighboring subproblems,so the disadvantages of computational complexity, slow convergence and lack ofdiversity in gene algorithm is reduced. For related signal processing, considering theinterferences from sidelobes and different channels caused by correlation of differentechos, a MIMO radar adaptive pulse compression algorithm based on iterative updatingis introduced, the algorithm utilizes the information from echos of a number of rangebins and then restrains the range sidelobe and cross-correlation interferences, in thisway it compensates the shortage caused by imperfect orthogonal waveforms.Focused on the spatial distribution of transmitted energy for MIMO radar, amethod for beampattern synthesis and follow-up phase-coded signal design for coherentMIMO radar are studied. Under the beampattern synthesis scheme for MIMO radardeveloped by Fuhrman, a beampattern synthesis method based on DFT newton-likealgorithm is studied which transfoms power restraint problem into a problem withoutrestraints at the cost of increased the number of variables. It substitutes alterablesearching steps for fixed steps of steepest descent method without calculating Hessematrix. Based on the results of baeampattern synthesis, two phase-coded waveformdesign methods are studied: The first is phase-coded waveform based on probabilityoptimization, in which the correlation matrix is denoted with code set and probability,and code is obtained by gambling. The second is phase-coded waveform based on lowpeak average ratio, the related optimization function is introduced and optimized bycyclic optimization algotithm.Focused on the waveform design of target detection for MIMO radar, a method ofadaptive waveform design for MIMO radar based on phase-coded signal and asub-carrier coefficients optimization method for spatial-diversed OFDM waveform arestudied. For the design of phase-coded waveform, a pattern of alternative searching anddetecting is introduced: Firstly an initial waveform is transmitted to get a primaryestimation of target range profile, then waveform is optimized to increase signal-clutterand noise ratio and a preciser estimation is obtained. This process is repeated to enhancedetection performance. Based on the phase-domain grads of optimization function, aphase-domain conjugated grads optimization algorithm is introduced. For thefrequency-coded waveform, MIMO radar model based on OFDM waveform is studied.The optimization object function of sub-carrier coefficients based on GeneralLikelihood Ratio Test is introduced and solved by gene algotithm. The effect of clutterand noise on the detection performance of OFDM-MIMO radar is shown at the end of this chapter.Focused on the waveform design of adaptive tracking for colocated MIMO radar, aadaptive waveform design scheme for target tracking is analysed, on which a adaptivewaveform design algotithm for MIMO radar based on particle filtering is studied.Firstly the state model and measure model are analysed based on single-carrier gaussianpulse. Taking the mean square error of parameter estimation as waveform designstandard, the optimum transmitted waveform parameters are calculated and feed back tothe transmitter in the end of each filtering to increase the tracking precision. For thesituation of colocated MIMO radar which transmits OFDM waveform, particle filteringis taken account considering the possible nonlinear and nongaussian characteristic.Under the contraint of transmitted energy, the sub-carrier coefficients of OFDMwaveform are optimized to minimizing the trace of PCRB matrix. In this way thetracking accuracy is improved.