Research On Motion Compensation ISAR Imaging Algorithm For Maneuvering Target

The principle of the inverse synthetic aperture radar(ISAR)imaging system is to map the moving target scattering component onto a two-dimensional plane according to the electromagnetic scattering characteristics of the target,thereby obtaining the general outline of the target,and presenting its moving state.ISAR imagery plays an important role especially in military applications such as target identifcation,recognition,and classifcation.In these application scenarios,how to achieve sharp resolution in both range and cross-range domains is a key requirement of the ISAR imaging algorithm.However,when the motion state of the target becomes complex,that is,that is,the translational motion and the rotational motion of the target are non-uniform,the traditional ISAR imaging algorithm will no longer be applicable,and the image resolution will be seriously degraded or even distorted.Based on this,two motion-compensated ISAR autofocus imaging algorithms are proposed in this paper,and a good compensation effect is achieved.The main contents of the paper are as follows:Firstly,ISAR maneuvering target imaging geometry model is established,and the basic concepts of ISAR imaging,such as one-dimensional range image and azimuth image,and Doppler effect,are emphasized,and the range-Doppler imaging algorithm is introduced.These concepts and principles serve as the basis for the following chapters and support the theoretical system of the proposed method.Secondly,for the high-speed translational maneuvering targets with uniform and large angle,the range cell migration compensation(RCMC)caused by the target rotational motion is obtained by keystone transform,but the translational compensation effect of the algorithm is poor when the target radial velocity is large and the target has radial acceleration.The phase retrieval algorithm can achieve high-speed maneuvering targets autofocusing imaging on the basis of compensating the above-mentioned translational components.Therefore,this paper proposes an ISAR imaging algorithm combining keystone transform and phase retrieval.In the experimental simulation,compared with the results obtained by the classical motion compensation algorithm,the effectiveness of theproposed algorithm is verified.Finally,the imaging model of large-angle high-speed maneuvering target with non-uniform rotation is introduced.According to its echo characteristics,it is deduced that the cross-range and range of the ISAR image will be severely defocused under this condition.In order to correct the phase errors in the echo signal,an imaging method based on phase retrieval algorithm and Gabor wavelet transform(GWT)is proposed.The approach uses the GWT as the time-frequency analysis tool to perform rotational motion compensation,that is,to eliminate time-varying terms caused by rotational motion in the Doppler frequency shift,and then use the phase retrieval to compensate for the remaining translational components,and finally obtain the focused imaging effect.