Research On Adaptive Clutter Suppression In Seeker PA And MIMO Radar

With the development of stealth coating materials,low altitude penetration and other equipment technologies,the electromagnetic environment of the battlefield becomes increasingly complex,and the precise missile guidance technology becomes particularly urgent.Phased array radar has the characteristics of flexible beam scanning,short wave dwell time,ability to detect multiple targets and high main lobe gain,etc.MIMO radar has the advantages of full space beam coverage,strong interception resistance and large virtual aperture,etc.Hence,applying two working modes of phased array and MIMO radar to seeker will bring new breakthrough and technical innovation to guidance technology.This thesis focuses on the seeker phased array and MIMO radar,and studies the signal model,clutter property and clutter suppression algorithm under different scenes.The main work and contribution are as follows:1.Research on clutter rank estimation algorithm in diving platformA clutter rank estimation algorithm is proposed for clutter scenarios of seeker phased array and MIMO radar subduction motion platform.Based on the forwardlooking geometry model of the radar seeker,the relationship between the spatial frequency and Doppler frequency and the diving angle is derived.The spatial frequency and Doppler frequency information are projected onto the axes of the ground inertial coordinate system to obtain the virtual aperture in three dimensions.The clutter rank estimation formula of phased array and MIMO radar is derived by using the coupling relationship between wave positions in different dimensions and the spatial resolution unit generated by virtual aperture.2.Research on clutter range-dependent compensation algorithmTwo kinds of clutter compensation algorithms are given for clutter range dependence in the scene of close-range target detection for radar seeker.According to the space-Doppler frequency characteristics,the clutter range dependence and clutter spectrum diffusion are discussed.A 3D subaperture smoothing window is constructed by using the azimuth-elevation-Doppler echo data of the planar array.The covariance matrix of each range sample and the clutter space-time frequency information are estimated,and the range dependence of the clutter is eliminated by compensating the frequency difference between the range sample and the sample under test.By using the concept of virtual aperture of MIMO radar,the transmit-receive array is equivalent to a uniform linear array with larger aperture,and a subaperture smoothing window with larger dimension is constructed,so as to improve the accuracy of clutter frequency estimation and the effect of clutter compensation.3.Research on short-range clutter suppression algorithm with distance ambiguityTwo elevation beam-design algorithms are proposed to suppress short-range clutter while range ambiguity exists.The first algorithm constructs a Quadratic Program(QP)problem with the objective function of minimizing the side lobe level energy of the short-range clutter region as the objective function,and taking into account the requirements of non-loss output of the target signal,no distortion of the main lobe and overall side lobe level control,etc,and solved by using convex function.The second algorithm constructs several auxiliary channels in the short-range clutter area to cover and sample the short-range clutter,and then constructs the elevatiom beam weight optimization problem based on MVDR robust beamforming.The algorithm has strong system robustness and reduces the processing dimension of the system.4.Research on high gating-lobe clutter suppression algorithm in uniform subarray structureTwo kinds of transmit beam weight optimization algorithms are proposed for the high gating-lobe clutter suppression in uniform subarray structure for phased array radar seeker.The first algorithm constructs a non-convex quadratic constrained quadratic programming(QCQP)problem with the objective function of minimizing the sidelobe energy of the grating-lobe clutter,and taking into account the requirements of transmit weight vector norm being 1,integrated sidelobe level control requirements.Such problem can be solved by the positive semidefinite relaxation(SDR)technology.The second algorithm assumes that the prior information of the target and Clutter is known,and takes the signal-to-clutter-plus-noise Ratio(SCNR)as the criterion to jointly optimize the transmitting beamforming and receiving space-time filters.The SDR technique is also used to convert the non-convex problem into a convex problem,and the solution is solved by several iterations.5.Research on non-uniform subarray division and auxiliary channel constructionA non-uniform subarray division method based on genetic algorithm(GA)is proposed in the subarray structure of MIMO radar seeker.The criterion,crossover and variation operations are carried out on the population individuals to find a reasonable subarray division based on the proper fitness function.An auxiliary channel construction method based on environment perception is proposed for reduceddimension STAP processing in non-uniform subarrays.According to the energy distribution of the clutter spectrum,the strong clutter frequency points that affect the target detection are found,and the auxiliary channel is constructed to eliminate the clutter of the main channel.This method can obtain better clutter suppression effect with fewer auxiliary channels.