Study On FDA MIMO Radar Waveform Design And Mainlobe Interference Suppression

MIMO radar transmits orthogonal signals between each element,giving it the advantage of waveform diversity.Compared with traditional phased array radars,it has range/angle/speed resolution,system freedom,anti-intercept probability,and weak targets.The detection capabilities have been greatly improved.Orthogonal waveform design is an important research direction of MIMO radar.Good orthogonal performance can make MIMO radar have higher main-sidelobe ratio and lower autocorrelation peak sidelobe level and cross-correlation peak level.High main-sidelobe ratio can greatly reduce the submergence probability of large targets to nearby small targets.Low cross-correlation reflects the good orthogonality between the transmitted signals of each array element,which is beneficial to the separation of signals at the receiving end and directly affects the radar system to the target.The detection performance.In addition,with the vigorous development of information technology,the game between radar jamming and anti-jamming has become increasingly fierce,especially the main lobe range deceptive jamming,which seriously affects the radar's detection performance on targets and greatly affects the survivability of the radar on the battlefield.Challenge.Therefore,this thesis mainly focuses on the orthogonal waveform design and anti-jamming capability of MIMO radar.The main work of this thesis is presented as follows:In the first part,it first introduces the advantages of MIMO radar compared with traditional radars,constructs a MIMO radar signal model,analyzes the general flow of MIMO radar signal processing,and expounds the principles of matched filtering technology and beamforming technology in signal processing.Finally,the optimization performance that is often considered when the MIMO radar adopts the optimization criteria in the waveform design is given,and the concept and main properties of the ambiguity function are proved.The second part mainly studies the design method of MIMO radar quadrature phase encoding waveform.First,a signal model of quadrature phase encoding is constructed,the commonly used waveform optimization algorithms are described,and the commonly used optimization criteria and performance indicators are introduced.Improve the original GSQP orthogonal waveform design algorithm,optimize its inter-individual crossover operation and chromosome variant operation,improve the algorithm optimization performance,and enable it to achieve local efficient search under the premise of ensuring good global optimization capabilities.It also simulates and analyzes the effect of different weights and signal numbers on the performance of the algorithm.Finally,a mismatch filter is introduced,and a method of joint waveform and mismatch filter optimization is given,which further reduces the APSL and PCCL of the signal,and enhances the main and sidelobe ratio of the signal,and the effectiveness of the algorithm is verified through simulation experiments.In the third part,the main lobe distance spoofing suppression method of the FDA-MIMO system is mainly studied.First,introduce the concept of main lobe range deceptive jamming,construct an FDA-MIMO radar signal model,and explain the principle that the FDA-MIMO system can distinguish between real targets and main lobe range deceptive false targets.Next,the interference and target may exist.If the distance is close,it is not obvious to distinguish the problem,and a solution of frequency compensation is given.Then,for non-ideal conditions,when there is an error between the target and the interference,the interference suppression performance is reduced,and the signal steering vector mismatch and the impact of the expected signal in the interference and noise covariance matrix are analyzed.A robust adaptive beamforming interference suppression algorithm under the FDA-MIMO system: first propose an improved diagonal loading technology to enhance the robustness of the system,improve the original algorithm,and then determine the target spatial frequency range,and further determine the corresponding derivative The limit value of the vector fluctuation interval is introduced with parameters to shrink the constraint conditions to further obtain a better solution;and then through the method of nulling and widening,a wider null is automatically formed at the interference position to effectively suppress the interference and improve the robustness of the system.Finally,simulation experiments verify that the method in this paper still has a robust interference suppression capability when there are errors in the target and interference at the same time.