The Methods Of Detection And Discrimination Of Unresolved Targets Of The VHF Radar

The VHF radar is an important part of modern warning radar because it has the advantage of resisting the stealth and the anti-radiation missile.However,in modern warfare,fighter aircraft often use formation flying mode,which cannot be effectively distinguished by using the VHF radar that has a low operating frequency and poor detection accuracy.Therefore,in In order to improve the multi-target detection and resolution of the VHF radar,this paper studies from two aspects: the multi-targets detection is performed by using the complex monopulse ratio from angle dimension.And the bandwidth is improved by using the multiband fusion method from range dimension,thereby achieving the goal of multi-targets resolution.The main research contents of the thesis include:Firstly,the basic resolution theory of radar is introduced.The antenna pattern function of the linear array is given.And the relationship between the angular resolution that is defined by the half power beam width and the antenna beam is analyzed.Then,the meaning of the fuzzy function is analyzed and its concrete expression is derived.According to the expression can get the relationship between the range resolution and the bandwidth.Secondly,the multi-targets detection method based on the target angle information is analyzed.In this thesis,the multi-targets detection is performed by using the monopulse ratio.The phase sum-difference angle measuring method and the amplitude sum-difference angle measuring method are analyzed.Then,based on the linear array model,half-array sumdifference angle measuring method and full-array double-point sum-difference angle measuring method are introduced.And contrast simulating the sum-difference beam and the corresponding angle curve by using the above two methods.The statistical characteristics of the monopulse ratio in single-objective and multi-targets cases are analyzed.According to the different characteristics can obtain the multi-targets judgment conditions.The relationship between detection probability and SNR or target angle interval are simulated.Finally,the multi-targets resolution method based on the target distance information is analyzed.In this thesis,multi-band splicing technology and multi-band fusion algorithm are used to improve the range resolution of radar,which can improve the ability of radar to resolve multi-targets.The Stepped-Frequency Waveform is used to establish the radar echo.From the perspective of the One-dimensional Range Profile,the relationship between the sub-band spacing and splicing effect is researched.Then,based on the existing fusion algorithm,the algorithm is improved for coherent registration and model parameter estimation.Which improve the fusion accuracy for the VHF radar.Simulation results show that the proposed method can reduce the fusion error and get the better results for the VHF radar.