Waveform Optimum Design Technology For MIMO Radar

Traditional radars emit electromagnetic waves in a relatively fixed mode,using relatively fixed beams and waveforms.It is difficult to achieve satisfactory performance in a complex and changing working environment,and it cannot meet the needs of multi-tasking and MIMO radar is an extension of the radar system.It has multiple transmit and receive antennas,and each transmit antenna can transmit different signals.This makes MIMO radars have the advantage of waveform diversity.MIMO radar transmits different signals so that the energy is concentrated in the angular range of interest or evenly distributed in space.Multiple transmitted signals synthesize different waveforms at different angles,thus having a strong anti-intercept ability.The waveform diversity advantage of MIMO radar makes the radar system have a higher degree of freedom of transmission.It can flexibly design the transmission energy coverage map for different working scenarios and requirements;and also adjust the transmission waveform in time according to environmental information.Therefore,waveform optimization design technology for MIMO radar is an important research field.The specific content of this thesis is as follows: First of all,a MIMO radar model with a uniform linear array is firstly established,and the signal model is given.On this basis,two commonly used signal processing methods for MIMO radar are introduced.Then the radar emission energy coverage map,pulse synthesis results,Doppler sensitivity curve related concepts,which are important indicators for evaluating MIMO radar waveform design technology,are introduced.Secondly,the design methods of orthogonal waveforms are studied,which are divided into orthogonal phase-encoded signal waveforms and orthogonal LFM signal waveforms.Their autocorrelation,cross-correlation functions,pulse synthesis results and Doppler sensitivity curve are analyzed and compared.Finally,some related waveforms are discussed.The design of the partially related phase-encoded signal waveform can be divided into two steps.First,the semi-definite quadratic programming and the fundamental beam method are used to optimize the transmission waveform.The complexity of the two methods and the results are compared and analyzed;then get the transmission waveform and compare its performance indicators using Cyclic Algorithm and Sequential Quadratic Programming,In terms of some relevant LFM signals,by analyzing the transmission energy coverage map of the LFM signal,find the factors that affect the transmission energy coverage map in the LFM signal parameters.Then,to solve the problem that the main lobe of the partial correlation LFM signal pulse synthesis result has a large spread with respect to pulse width related to signal bandwidth,a method is proposed to design the partial correlation waveform of the LFM signal based on sub-array orthogonality.The method improves signal freedom by jointly optimizing signal bandwidth and initial phase.The pulse synthesis result of this method demonstrates that the main lobe is not fundamentally widened,and the peak value of the side lobe is low,which improves the detection performance of the radar system.