Research On Anti-interference Algorithm And Performance Of Array Radar

Interference suppression is one of the foremost tasks in many fields of applications like radar,wireless communications,etc.In order to deal with different scenarios,it calls for targeted strategies and schemes to suppress the interference.In the study of the interference suppression in array radar,we present novel and significant research on mainlobe interference suppression,null broadening algorithm design,robust design for array radar,mutual interference suppression approach for spectrum sharing between the radar and the communication systems.The contributions of this thesis are:(1)Mainlobe interference suppressionThis work proposes a novel mainlobe interference suppression method based on eigen-projection preprocessing and beam pattern reshaping.We can easily determine the existence of the multiple mainlobe interferences via the eigen-beam theory,and then construct the eigen-projection matrix to preprocess the echo data.Meanwhile,a convex programming model is used to reshape the mainlobe beam pattern,which yields the adaptive weight vector.This novel mainlobe interference suppression method can enjoy low sidelobe level and well-maintained mainbeam of the beampattern.(2)Null broadening algorithm design with respect to the perturbation of the interference locationIn this work,a procedure for the null broadening algorithm design is proposed.We first reconstruct of the interference-plus-noise covariance matrix.Additionally,in order to restrict the shape of the beampattern,the adaptive weight vector can be computed via maximizing a new signal-to-interference-plus-noise-ratio(SINR)criterion subject to similarity constraint.The nonconvex design problem can be solved by semidefinite programming(SDP)techniques.Finally,an optimal solution can be found by using the Charnes-Cooper transformation and the rank-one matrix decomposition theorem.(3)Robust adaptive beamforming algorithmThis work first addresses a robust adaptive beamforming algorithm against direction mismatch.The essence of the method is to maximize the SINR subject to quadratic constraints in the specific signal directions.The original robust design is recast as a convex problem which is derived based on the semidefinite relaxation(SDR),and then a rank reduction procedure is presented to approximate the optimal solution.Then,a novel robust design algorithm based on estimation of signal steering vector and covariance matrix is developed.The nonconvex desired signal steering vector estimation problem,whose relaxation is tight through analyzing the hidden convexity properties,can be solved by the relaxed SDP method.Moreover,the interference-plus-noise covariance matrix is estimated with the corrected steering vector and the sub space theorem,whose efficiency is analytically proven.(4)Robust design for MIMO radarIn this work,we consider robust adaptive beamformer design for multiple-input multiple-output(MIMO)radar systems.The desired transmit-receive steering vector is estimated through maximizing the output power subject to constraints upon correlation coefficient and steering vector norm.The original nonconvex problem is reformulated as two reduced dimension SDP problems.An iterative procedure is devised to tackle the two SDP problems.Based on the estimated desired signal,we are then able to obtain the interference covariance matrix via the matrix rank-constrained minimization method.(5)Models and algorithms for spectrum coexistenceThis work first considers the transmit designs in spectral coexistence of MIMO communication and co-located MIMO radar systems.A joint optimization of the communication transmit covariance matrix and the radar transmit waveform is designed to maximize the communication rate.The original design is constructed by solving two convex optimization problems.Then an algorithm of alternating iterative procedure is developed,whose solutions are provided in closed form.Then,we consider a novel joint design of a MIMO radar with co-located antennas and a MIMO communication system.The degrees of freedom under the designer's control are the waveforms transmitted by the radar transmit array,the filter at the radar array and the code-book employed by the communication system to form its space-time code matrix.Two formulations of the spectrum sharing problem are proposed.Firstly,the design problem is stated as the constrained maximization of the SINR at the radar receiver,where interference is due to both clutter and the co-existence structure.The resulting problem is nonconvex,based on iterative alternating maximization of three suitably designed sub-problems,is proposed and analyzed.In addition,the constrained maximization of the communication rate is also investigated.