Study On Altitude Measurement In VHF Array Radar

Since VHF(Very High Frequency)radar has some advantages in anti-stealth and antiARM,it has attracted the wideattentions,even it has been used in modern warfare.In the model of multiple paths of signals,when using VHF radar to estimate the low-altitude target's angle,since VHF radar has wide beam,which makes it more easily to receive two types of coherent echos,the direct path echo and the reflection multipath echo,because the two types of echos are received inthe same beam(the antenna main beam),this willreduce the accuracy of the angle estimation.In the same model of multiple paths of signals,When using VHF radar to estimate the high-altitude target's angle,especially when the multipath fading co-efficient is close to one,this means that the reflective surface is smooth and the most part of the reflection multipath echo is received by VHF radar,because the reflection multipath echo's appearance in the antenna side beam,this will also reduce the accuracy of the angle estimation.In this paper,algorithms of DOA estimation in VHF array radar is focused.In this paper,it has four parts.In the first part,some super-resolution algorithms that can de-correlate multiple coherent signals such as spatial smoothing algorithm,Toeplitz algorithm and maximum likelihood estimation algorithm are analyzed.In the second part,some algorithms that can de-correlate the direct path echo and the reflection multipath echo from the model of multiple paths of low-altitude signals are analyzed,such as generalized MUSIC and the modified generalized MUSIC.Through some simulations,the accuracy of the angle estimation of these de-correlation methods is shown and some application conditions of these methods are pointed out.In the third part,a new method for de-correlating the direct path echo and the reflection multipath echo from the model of multiple paths of high-altitude signals is presented,some simulations also show its accuracy of the angle estimation and its application conditions.In the last part,the compressed sensing algorithm for de-correlating the direct path echo and the reflection multipath echo from the model of multiple paths of low-altitude signals is analyzed,including the construction of sparsity model of source signals,some conditions of the construction,different ways of space-partition and the coherence of manifold matrix.Some simulations show the accuracy of the angle estimation of the modified generalized MUSIC and the CS algorithm.