Research On Beampattern Synthesis And Adaptive Processing Of The Array Radar

The array radars have roughly gone through mechanical scanning radars,phased array radars,and multiple-input multiple-output(MIMO)radars.They scan targets in the spatial domain through beamforming at the transmitter and receiver.The array radars are widely used in the scenes of early warning,detection,and fire control in the military,as well as in the scenes of meteorology,remote sensing,and vehicle collision avoidance in the civilian world.Among them,MIMO radar has more processing degrees of freedom than phased array radar because of its angle-time domain waveform diversity characteristics,and it can obtain better performance in target detection,parameter estimation,and anti-jamming.On the one hand,array radar beampattern synthesis is a vital segment that needs to be realized by the radar transmitter to detect target information in a specific scope of the angle domain.In the framework of MIMO radar,it relies on waveform design.In the complex electromagnetic environment,thoroughly using the degrees of freedom of angle,time,frequency and other domains to reasonably design the amplitude and phase of the transmitted waveform to meet the needs of various target probing scenarios has significant engineering applications value.On the other hand,the receiving end of the array radar needs to make reasonable use of the prior information of the target,and fully consider the robustness of the weak power target in the complex electromagnetic environment with signal-related interference,clutter echo,clutter broadening and burst pulse.The optimal filtering weight vector can be designed under suitable criteria to obtain excellent filtering performance.Therefore,the research on beampattern synthesis at the transmitting end and robust adaptive processing at the receiving end of the array radars has significant engineering application value and broad application prospects.In this dissertation,aiming at the transmitting beampatterns synthesis and adaptive receiving processing of the array radars under different scenarios,the main research contents and innovations obtained are listed as follows:1.Considering the constant modulus constraint of the transmitting signal waveform,a non-convex high-dimensional constrained optimization model is established for the angle-delay domain transmitting beampattern synthesis problem of the array radar,and a MIMO radar transmitting waveform design algorithm based on the alternating direction method of multiplier(ADMM)method is proposed.The algorithm gives a straightforward iterative solution to the non-convex high-dimensional constrained optimization problem.It aims to jointly optimize the performance of the transmitting beampattern,waveform autocorrelation characteristic,and cross-correlation characteristic.It can avoid range sidelobes of the strong target echo to cover up weak target echoes in the nearby distance unit.It can reduce the influence of range deception interference on accurate target probing.The simulation results show that the waveform designed by the proposed algorithm can synthesize near-optimal beampattern with lower autocorrelation sidelobe level and cross-correlation level.2.Considering the constant modulus constraint and similarity constraint of the transmitted signal waveform,a MIMO radar transmit waveform design algorithm based on the minimization majorization(MM)method is proposed for the angle-frequency domain transmit beampattern synthesis problem of the array radar.In each iteration,the algorithm designs a substitute function to approximate the cost function of the previous step and gradually approximates the optimal solution of the waveform,aiming to optimize the performance of beampattern synthesis and spectrum compatibility.The frequency band that can avoid the communication equipment does not affect the communication transmission performance.Simulation results show that the waveform designed by the proposed algorithm has good spectrum compatibility performance.3.Considering the constant modulus constraint and similarity constraint of the transmitting signal waveform,a joint robust design algorithm of MIMO radar transmitting waveform and receiving filter weight vector for the angle domain beampattern synthesis is proposed for the problem of combining the transmitting and receiving beampatterns in the angle domain of the array radar.The algorithm first establishes a signal-to-interference-plus-noise-ratio(SINR)maximization model including the target,interference prior information and uncertainty,then converts the fractional cost function into a quadratic function.And then iteratively solves it,which aims to optimize the beampattern performance and robust filtering performance of the MIMO radar in the case of signal-related interference and inaccurate prior information of target and interference.In other words,when prediction angles of the target and interference are mismatched,the beampattern mainlobe can be aimed at the target direction and the beampattern nulling can be aligned to the interference direction,meanwhile preferable output SINR performance can be obtained.Simulation results show that the waveform and filtering weight vector designed by the proposed algorithm have good beampattern synthesis performance and robust filtering performance.4.For the design of the weight vector of the receiving filter in the angle-Doppler domain of the airborne phased array radar,this dissertation considered the situation where the strong clutter covers the weak target,the target estimated angle and Doppler are inaccurate,and there are the clutter broadens and the interference suppression.A robust spacetime adaptive processing(STAP)algorithm based on alternating projection is proposed to reconstruct the clutter plus interference covariance matrix and the target steering vector in a specific range of the angle-Doppler domain and then use the minimum variance distortionless response(MVDR)design receiving filtering weight vector,aiming to optimize the signal-to-clutter-plus-jamming-plus-noise ratio(SCJNR)performance.The simulation results show that the filter weight vector designed by the proposed algorithm has good SCJNR performance and robust filtering performance.5.For the robust subspace tracking problem under the influence of burst pulse and strong clutter,a parallel estimation and tracking via recursive weighted least squares(PETRWLS)with less computational complexity is proposed.After the weight coefficients that can suppress the burst pulse are designed,and the target reflected signal and the target subspace are successively estimated from the received signal,in order to optimize the subspace estimation error performance.Then the dynamic characteristics of the algorithm is analyzed through the differential equation.In addition,for the problem of tracking the far-field target subspace in a distributed array without a central processor,a PETRWLS algorithm based on average consensus(AC)is proposed.The total average value is calculated to update the real-time estimation of the target subspace to obtain better subspace estimation performance and angular resolution performance than a single node.Simulation results show that the subspace estimated by the proposed algorithm has good estimation error performance and robust performance.