Height Measurement Data Analysis And Improvement Of Algorithms For VHF Array Radar

With the development of stealth technology,anti-stealth target and anti-radiation missile attract extensive people's eyes,and a growing number of countries pay much attention to VHF radar.However,VHF radar has wide beam,which usually causes bad angular resolution.Furthermore,because of the beam wideness,the beam often reflects to the ground in the low elevation angle area,leading to the lobe cocking-up and deformation.The received signal in the main lobe not only includes the direct path signal from target directly,but also the complex reflection multi-path signal that is reflected the ground(sea)surface,which seriously affects the VHF radar angle measurement performance.Therefore,the key problem that needs to be solved urgently is improving the low-elevation angle accuracy.Based on a certain VHF digital phased array radar and the real data,this thesis starts from low angle estimation in VHF radar.The main contents of this thesis are summarized as follows.1.The foundation knowledge of DOA estimation for VHF radar is introduced.Firstly,the mirror reflection signal model and the precision spherical multipath signal model of altitude measurement for low angle target are studied.Then,several conventional altitude measurement algorithms of VHF radar are introduced,including DBF,MUSIC and SVML.These algorithms are deduced and analyzed,and preliminary simulations are carried out.Finally,combined with the measured data from the field experiments to analyze the performance of these algorithms,then a performance comparison of all these algorithms is presented.Also,their advantages and disadvantages are also discussed.2.The improvement of altitude measurement algorithms for VHF radar is studied.Firstly,a novel height finding method based on spatial filtering for VHF radar is introduced,and its advantages and disadvantages are discussed.Then an improved method is proposed for the deficiencies.Simulations and real data processing results are presented to verify the effectiveness of the improved method.Secondly,an in-depth discussion and analysis are made for the problem that the synthetic steering vector maximum likelihood algorithm being sensitive to terrain.Then,a terrain matched algorithm of synthetic steering vector maximum likelihood algorithm is studied,and a specific terrain correction scheme is given.Real data processing results show that the proposed method can improve the angle measurement performance significantly.3.The angle measurement performance comparison between distributed arrays and uniform array based on real data processing is studied.Firstly,the signal model of the distributed array is introduced.Then,algorithms including SVML,SSMUSIC and DBF are used to process the distributed array and the uniform array's real data,and their processing results are compared.The results show that the SVML is the best in these algorithms.In the SVML results of uniform array,there are jump-points that have great error compared to real value.It is concluded that the multi-peak phenomenon in the spectrum is the cause of wrong angle results.Finally,the error value of the distributed array and the uniform array of SVML angle measurement results are presented.The statistical results show that the results of the distributed array are better than those of the uniform array.