Abstract:
Target optimal polarization is the fundamental theory of radar polarization. Null-Pol(null-polarization), also called Co-Pol Null, is the important component of target optimal polarization, through which other optimal polarization states can be derived. The Null-Pol theory is widely applied in polarization reception match, contrast enhancement and so on. From the aspect of scattering structure recognition, this paper reveals the advantage of Null-Pol theory for the first time. Based on the Null-Pol theory, the Null-Pol vectors of canonical structures are derived theoretically. A visualization tool called Null-Pol 3D response patterns are constructed by combining the complex polarization ratio plane and polarization response characteristics, which can reveal the differences of canonical scattering structures. Then, the Null-Pol response characteristic vectors are derived. On this basis, the Null-Pol scattering structure recognition method of manmade targets is proposed. Firstly, the scattering centers are extracted from radar images. Then, the scattering types of scattering centers can be identified by matching the Null-Pol response characteristic vectors with canonical structures. Finally, the scattering structure of manmade targets can be recognized. Comparison experiments are performed on electromagnetic computation data of manmade targets such as vehicles and UAVs. Experimental results show that proposed Null-Pol scattering structure recognition method can accurately identify the scattering structure types of manmade targets. Especially, the results of symmetric targets have better performance than Cameron decomposition results, which are more consistent with the actual scattering structure types of targets.