Study On Method Of Angle Estimation Of Low-Altitude And Multipath Target

Modern war is a competition for electronic information technology,and the initiative of information and intelligence determines the direction of victory and defeat.Radar is an important facility for obtaining enemy information in war,and low-altitude penetration is one of the important factors threatening the survival of radar.In contemporary warfare,in order not to be discovered by the enemy,to improve the survival rate and the success rate of the attack,the flight altitude of the warplanes and missiles are very low when approaching the target.Low-altitude targets have low flying heights and high speeds,and can be concealed in the terrain environment.These make it difficult for radar to detect such targets.Multipath effects are the main factors affecting the radar's detection and tracking performance for low-altitude targets.This paper focuses on the angle estimation problem of low elevation,and studies it from multipath reflection model,common angle measurement method and high-precision angle measurement method.Firstly,the multipath effects affecting the accuracy of angle estimation of low-altitude targets are analyzed.The echo forms under the two models of classical multipath reflection and multi-reflection distribution source are introduced.Then three traditional methods of angle measurement are introduced: off-axis method,C2 method and complex angle method,and each method is simulated and analyzed.Then,the research and analysis of the angle measurement technology of low-altitude target under the digital array radar system is done.The theory of maximum likelihood estimation is expounded in detail,and the application of this theory in the field of angle measurement of low-altitude target is introduced.An improved weighted multi-frequency maximum likelihood elevation estimation method based on frequency diversity is proposed.On the basis of fully studying the multi-reflection distribution source model,a low elevation angle estimation method suitable for the model is proposed,which is suitable for flat and rough landforms,and the stability and robustness of the algorithm are good.Finally,the application of compressed sensing in the field of angle measurement of low-altitude target is studied.Based on the theory of compressed sensing,combined with the characteristics of low-altitude targets,a signal model conforming to the theory of compressed sensing is established.Then,angle measurement algorithm and sparse reconstruction algorithm based on the compressed sensing are introduced.An angle measurement algorithm of low-attitude target which is based on optimized array and compressed sensing is proposed.This method only selects part of the echo data for processing,which can effectively reduce the data dimension,the difficulty and computational complexity of signal recovery,and the accuracy of angle measurement is high.The proposed algorithm is compared with the traditional method through simulation experiments.