Research And Application On Radar Polarization Statistical Characteristics Of Multipoint-Source Interferences

With the increasingly fierece competition in the battlefield electromagnetic spectrum and with the increasingly frequent spectrum utilization in human life,all sort of intentional or unconscious,active or passive radio signals could be inevitablely received by radar system.The information differences between interference and targets in time-frequent-space domain are ulteriorly compressed when the interferences are radiated from multipoint sources.Conventional single polarimetric radar systems may not achieve satisfied interference suppression effect.The polarization information of radar can be utilized to effectively improve the radar capability in anti-interference and target detection.However,they also put forward more challenges for the polarimetric radar filtering and detection technology because of the random polarization properties of the multipoint-source interference.This article is under the applying background of radar warning.The polarization statistical properties of the multipoint-source interference are mainly analyzed in this dissertation.Based on the characterization,the polarization filtering and target detecting techniques in multipoint-source interference and inhomogeneous clutter are both deeply researched.The main research achievements are given as follows:1.Polarization statistical properties of the multipoint-source interferences.Aming at random polarized multipoint-source interferences,various polarization parameter characterization models are established on the assumption of a complex Gaussian distribution with zero means.The statistical models of the polarization ratio and the degree of polarization are derived on the basis of complex Gaussian distributions with non-zero means.By simulation comparison,these models are proved more suitable to characterize the polarization signature of multipoint-source interferences with some determinating polarization component in domain.Polarimetric measurements and analysis of the typical multipoint-source interferences are developed,which include signals radiated from communication base stations to UHF-band radar,and active interferences which simultaneously exist in both main and side beam lobes.The polarization statistical models are furtherly demonstrated by the measurenment results.2.Polarimetric radar fitering technique.The interference in radar main lobe which influenced by the environment disturbance factors is considered as likely multipoint-source interference.Combining with the polarization statistical models and the real collected data,the polarization disturbance models for the main-lobe interference are generated.A noval pulse-in-pulse fast adaptive polarization filtering is supposed on the basis of polarizing cluster center.The traditional adaptive polarization canceller can be replaced by this filter to avoid the problems of low convergence speed and the iterative factor hard to choose.Aiming at the multipoint-source interference simultaneously existing both main and side lobe of radar beams,the research of the main-auxiliary array joint polarization filtering is carried on.A polarized array antenna configuration with main and auxiliary channels is designed.On the basis of the antenna,two kinds of polarization-space domain filterings are supposed,including gradient iterative and inverse matrix optimal filtering algorithms.By applying all the filters to the multipoint-source interference measurement data,the interference suppression effectiveness is demonstrated.3.Polarimetric radar detection technique.The statistical models of the degree of polarization for the inhomogeneous clutter under the assumption of compound Gaussian distribution are extended on the basis of vector product models.The statistical models of the degree of polarization are found insensitive with Gaussian or non-Guassian distributions.Focused on the issues of slow target detection in the inhomogeneous clutter environment,the radar polarization signal modulation is established.Two kinds of polarimetric detectors related to the degree of polarization are designed.The first one is the degree of polarization detector which ultizes the estimation of the degree of polarization as the statistics to make target decision.The second is a combination polarimetric detector which combines the polarization filtering and the degree of polarization detector.This detector can be used to cope with the heavy fluctuated inhomogeneous clutter.The performance of the polarimetric detectiors is evaluated theoretically,and several typical polarimetric detectors are applied to the real collected data.The comparison results for each detectors proved that the newly proposed detection algorithm has the potential to improve the target detection performance in the inhomogeneous clutter environment.