Detection And Number Estimation Of Unresolved Targets For Array Radar

Unresolved targets are a group of targets unresolved in range,speed and angle all.Research of unresolved targets,important for academic study and military application,is a hotspot in radar detection.This paper has a hard work on the detection and number estimation of unresolved targets in array radar.1.Detection of unresolved targets.Conplex monopulse can be used to detect the unresolved target since the monopulse of unresolved target is a complex number.Single target and unresolved targets monopulse ratio of a linear array are given firstly.We apply the analysis results to the plane array radar to develop the detector of unresolved targets by likelihood ratio test after studying the statistical distribution of unresolved targets monopulse ratio.Finally,some beneficial results have been achieved by simulation experiment and measured data.A large target with a small unresolved target is hardly to be detected.Two targets with the same power and large phase offset is easier to be detected.2.Number estimation of unresolved targets.Most methods of targets number estimation cannot estimate targets number when they are unresolved.In the condistion of single snapshot of unresolved targets,spatial smoothing and target number estimation should be improved.Virtual image array is bring into the spatial smoothing firstly.We give out the efficiency of this spatial smoothing and point out this process will make the noise correlatived.Then based on the Gerschgorin disks estimation(GDE)we modify the detection rules with center and radius of Gerschgorin disks after presenting the limitation of GDE for unresolved targets.The method of unresolved targets number estiamtion is proposed combining of the improved spatial smoothing and detection rules.Finally Simulation experiment results demonstrate the performance of the proposed method.The targets number is hard to estimated when small targets are behind large targets.The more unresolved targets,the more difficult to estimation.The conclusions of this paper provide theory foundation for resolution and trick of the resolved targets.