ISAR Autofocus Imaging Based On Phase Retrieval

Inverse Synthetic Aperture Radar(ISAR)has the characteristics of all-weather,all-day and long-distance,which can detect,image and identify airplanes,ships and so on.It occupies an important position in military strategy.In recent years,ISAR imaging of maneuvering targets has been a hot research topic.However,the traditional ISAR imaging and motion compensation methods can not achieve high-resolution imaging in high-speed maneuvering targets with the condition of random noise and aerostat borne ISAR platforms.Therefore,this paper proposes an ISAR autofocus imaging algorithm based on phase retrieval algorithm.The main contents are as follows:Firstly,the basic principle of ISAR imaging is introduced,and the Range Doppler(RD)algorithm is introduced in detail.The ISAR imaging model is analyzed.The applicable scope of RD imaging is introduced which is validated by experimental simulation.Secondly,the phenomenon that the radar platform is displaced or vibrated under the influence of the airflow is studied.The ISAR echo geometrical model is established for the two cases.On the basis of analyzing the characteristics of the ISAR echo,a phase retrieval algorithm based on priori knowledge can realize high-resolution imaging of the maneuvering target in the unstable state of the aerostat borne radar,and the uniqueness of the traditional phase retrieval algorithm is improved.The simulation results show that the proposed algorithm is effective.Finally,according to the ISAR echo characteristics,the phase retrieval algorithm is used to image the high speed maneuvering target.Then,the ISAR echo data is changed under the condition of random noise,and the high-resolution imaging can not be directly obtained by the phase retrieval algorithm.Therefore,the traditional phase retrieval algorithm needs to be improved.First,the effect of random noise on ISAR echo data should be eliminated before applying the traditional phase retrieval algorithm.The improved phase retrieval algorithm canrealize high-speed maneuvering target imaging under the condition of random noise.The simulation results show the feasibility of this method.