Research On Cognitive ISAR Algorithm Of Ship Imaging With Multipath And Sea Clutter Interference

As a new type of radar,cognitive radar is currently being used in many aspects of cognitive radar tracking tasks.It uses information from environmental feedback to change transmitter waveforms to improve tracking performance.This article will study the issue of cognitive radar in ISAR imaging of ships and design two major environments: a.sea clutter environment;2.multipath environment;cognitive radar ISAR imaging algorithms are mainly developed in the above two environments.Using the receiver's combined environmental information processing,the impact of the above two factors on ISAR ship imaging is reduced.In addition,aiming at the multi-degreeof-freedom of ship motion and the nonlinearity of the movement,the flexible change of the transmitter waveform enables the receiver to better acquire the attitude information of the ship in order to obtain a better non-defocused ISAR ship image.The content of this article is as follows:First,basic research is conducted to introduce basic ISAR imaging principles,imaging planes,and turntable imaging models.At the same time,we study the 6-DOF motion of the ship in the undulating environment of the waves,and the 3 degrees of freedom that contribute to the imaging,pitching,yaw,and rollover.The scattering point model is used to perform three-dimensional modeling of the above-mentioned movement model and imaging of the rotation model.Use the pendulum model to describe the rotation of the ship.A top view of the ISAR image,as well as a side view,and a hybrid image are obtained,resulting in the conclusion that the best imaging time node is near its zero crossing of motion.At the same time,contrast imaging was performed on the other time points in the wobble cycle to verify the above conclusions.Secondly,study the effect of ship's target clutter on the imaging under the circumstance of wave environment.At the same time,we also studied the cognitive radar using the sea clutter modeling parameters to perform the corresponding receiver CFAR detection processing,reflecting the cognitive radar ISAR.The adaptability of the imaging to the environment at the receiver.The k-distributed sea clutter model with space-time correlation was used for modeling and simulation(SIRP algorithm).The CFAR detection algorithm is used to detect the ship and the ISAR image with less clutter interference is obtained.At the same time,the treatment of the cognitive ISAR imaging and the method of inhibition are studied under the conditions of the ocean multipath environment.The particle swarm algorithm is used to construct the antidegenerate model to recover the echo data.Finally,the core part of the cognitive ISAR imaging radar is studied: dynamic waveform selector,dynamic waveform selector based on KF algorithm is studied,the noise measurement matrix is introduced into the algorithm,and the minimum mean square error criterion is used to select the waveform and reduce it.Tracking errors improve tracking accuracy.The dynamic waveform selector can apply tracking problems that are widely studied by cognitive radars to track ship attitudes,and acquire the linear echo data segments by acquiring the time nodes of ship rotation.