Performance Analysis And Optimal Design Of The MIMO GMTI Radar Waveforms

Transmit diversity is used in multiple input multiple output(MIMO)radar,so MIMO radar has more degrees of freedom and longer equivalent baseline than single input multiple output(SIMO)radar.Therefore,it has a huge potential to apply MIMO radar into ground moving target indication(GMTI)radar.The transmit waveform is the source of many problems in implementing of MIMO GMTI radar,and it is also a key factor influencing the performance of MIMO GMTI radar.In this paper,the performace analysis and optimal design of the MIMO GMTI radar are studied.Based on the general signal model for MIMO GMTI radar,the performance of the ideally orthogonal,fast-time and slow-time waveforms is analysed,and the nonorthogonal waveform design with a priori knowledge about the targets and interference is studied.The main work is as follows:A general signal model for MIMO GMTI radar is established in chapter 2.The existing transmit waveforms are special cases of the general signal model.The performance of the MIMO GMTI radar with ideally orthogonal waveforms is studied via this general signal model.The waveforms with the same time and carrier frequency can be separated by multidimensional waveform encoding at the cost of digital beamforming in elevation,thus the MIMO GMTI radar based on multidimensional waveform encoding is a kind of approximately ideal MIMO GMTI radar,the GMTI performance is also analysed.The performance of the MIMO GMTI radar with fast-time waveforms are analysed in chapter 3.The code division multiple access(CDMA)waveforms have high integrated sidelobe ratio,so its minimum detectable velocity(MDV)performance is close to the MDV performance of SIMO radar.The frequency division multiple access(FDMA)waveforms have the range-dependent characteristic due to the multiple carrier frequencies,thus the MDV performance of FDMA waveforms is also close to that of SIMO radar.In this capter,cyclic-shift transmission and range-compensation methods for FDMA waveforms are proposed,and these two methods can improved the MDV performance effectively.The performance of the MIMO GMTI radar with slow-time waveforms are analysed in chapter 4.The TDMA waveforms adopts switch mode of transmitters,so its MDV performance is improved due to its longer equivalent baseline than SIMO radar.However,only one transmitter is active in each pulse repetition interval(PRI),thus it has a signal-to-noise ratio(SNR)loss compared to the ideal MIMO GMTI radar.The Doppler division multiple access(DDMA)waveforms can separate the echoes in the Doppler domain,but the blind velocities are more serious in DDMA MIMO GMTI radar.In this capter,the methods of multiple carrier frequencies,multiple pulse repetition frequencies(PRFs),and multiple pulse repetition intervals(PRIs)are proposed to mitigate the blind velocities of the DDMA MIMO GMTI radar.The optimal design of the nonorthogonal waveforms in MIMO GMTI radar is studied in chapter 5.Aiming at the application scenarios with a priori knowledge about the targets,maximization of the output signal-to-interference-noise ratio is usually regarded as the objective function.The joint design of constant-envelope and similarity-constrained waveforms and receive filters is studied.In multi-target scenario,the performance of the moving target to be detected will reduce,because other moving targets will be included into the training data.This capter proposed a method based on interference covariance matrix reconstruction to avoid the influence of other moving targets effectively.Correctness of the theoretical results and validity of the proposed methods are demonstrated by simulation results.