Study On MIMO Radar Waveform Design And Transmit Beampattern Optimization

Multiple Input Multiple Output(MIMO)radar employs multiple antennas transmitting different signals at the transmit end,while separating the contributions of different signals at the receive end to improve the detection capacity of radar system,exploiting the gain of spatial diversity.Compared with traditional phased array radar,MIMO radar has more degrees of freedom,performs better at parameter estimation and detection.Waveform diversity is an important characteristic for MIMO radar differing from phased array radar,Waveform diversity is also the superiority where MIMO radar lies in.The degrees of freedom in waveform design make MIMO radar easy to form flexible transmit beampattern.Hence,this thesis mainly focuses on waveform design and transmit beampattern optimization for MIMO radar,The main work include the following:1.For MIMO radar frequency modulated waveform design,the waveform design method based on stationary phase principle is applied to complete nonlinear frequency modulated(NLFM)waveform design;Making NLFM signal as transmit waveform of a single channel,Orthogonal Frequency Division Non Linear Frequency Modulated(OFD-NLFM)waveform is presented for MIMO radar;Inspired by the theory of mismatched filtering,the iterative optimization of frequency modulated waveform and mismatched filter is considered to obtain NLFM waveform with super low pulse compression sidelobe level;Applying this signal to MIMO radar,frequency division FM waveform with super low sidelobe is designed.2.Focusing on phase coded signal design for MIMO radar,method based on sequential quadratic programming is applied to achieve phase coded signal,which possess the property of low autocorrelation sidelobe,low peak cross correlation and strict orthogonality.Aiming at the matched-out energy spread problem for extended targets,enlightened by the concept of sequences with zero correlation zone in communication,phase coded signal with zero correlation zone in range dimension and range-doppler dimension is designed based on method of sequential quadratic programming.3.For the problem of MIMO radar waveform design in colored noise,the relationship between energy spectrum of the optimal waveform and noise power density is derived firstly.In the condition that the receive filter is prewhitening-matched filter,the eigen-vector waveform design method is derived to maximize the output signal to noise ratio(SNR),the SWORD(Signal Waveform's Optimal under Restriction Design)algorithm is derived to maximize the output SNR with waveform similarity constraint.In order to fully utilize transmit energy,an adaptive constant modulus waveform design method under colored noise is proposed based on stationary phase principle;Finally,multiple waveforms for MIMO radar in colored noise are designed.4.Considering transmit beampattern optimization for MIMO radar,several common transmit beampattern optimization models and constraints are presented,including transmit beampattern matching design,minimizing peak sidelobe transmit beampattern design,minimizing integrated sidelobe transmit beampattern design.the ways to convert optimization models to convex optimization problems are also given.For the problem of transmit beampattern optimization controlling ripples within mainlobe,methods of weighted 1-norm and matrix regularization(MR)are proposed.Finally,MIMO radar transmit beampattern optimization model to control transition band is discussed.