Research On Moving Target Imaging And Cross-Range Scaling Based On ISAR

Synthetic Aperture Radar(SAR)and Inverse Synthetic Aperture Radar(ISAR)can work under any conditions.They have superior remote sensing and high-resolution imaging capabilities.ISAR refers to when the target is in motion,while the radar carrier is in a stationary state.The radar can actively transmit and receive electromagnetic waves.Compared to conventional optical imaging methods,its advantage is that it can image the target day and night without changing the climate.However,to meet the needs of practical applications,not only do we need to perform high-resolution images of the target,but also need to extract the size information of the target correctly.That is,perform cross-range scaling on the image.In other words,it is to convert the original range-Doppler plane image to the range-azimuth plane.Therefore,this paper not only discusses the algorithm of target imaging,but also deeply studies the method of crossrange scaling of the image.This paper firstly summarizes the research background and significance of radar imaging technology and ISAR imaging.Then the progress of ISAR imaging is analyzed,and three representative radar systems of ground-based,ship-borne and air-borne are analyzed.Then,starting from the basic principles of ISAR imaging,this paper systematically expounds the relevant theory of the turntable model,and deduces the formulas of the transmitted and echo signals.It also introduces the concept of motion compensation,and gives examples of commonly used algorithms.The simulation results confirm the importance of motion compensation.At the same time,the methods of traditional ISAR imaging and cross-range scaling are summarized,and the advantages and disadvantages of each scheme are simply compared.This paper also uses Range Doppler(RD)algorithm to image the target,and by adjusting the parameter of rotation speed,the law of target imaging under this algorithm is obtained.Then,this paper adopts Gaussian signals and the first to eighth-order Gaussian signals as the transmitted signals that comply with the Federal Communication Commission(FCC)standards,and uses the RD algorithm to image moving targets.By comparing the-3 d B bandwidth of the range slice,it is concluded that when a first-order Gaussian signal is used as the transmit signal,the resolution of the image is the best.At the same time,this paper improves it on the basis of the Back Projection(BP)algorithm.The improved algorithm is verified by simulation.It is found that in the case of different pixel sizes,the imaging time is different,so pay attention to balancing the relationship between them when imaging.Finally,this paper proposes a new scheme for moving target imaging and crossrange scaling.This scheme uses the instantaneous range instantaneous Doppler(IRID)method to perform ISAR imaging on moving targets.The scheme uses time-frequency analysis in both range and azimuth to replace the traditional Fourier Transform.The IRID algorithm and the RD algorithm are used to image the target respectively,and the image entropy and average gradient of the two images under the two algorithms are obtained,which proves the practicability of the IRID algorithm.Moreover,for the ISAR image generated by the IRID algorithm,when the target rotates at a constant speed and a constant acceleration,the rotation parameters are estimated by the method of image rotation correlation transformation,and the cross-range scaling of the target is completed.And put forward a comparative experiment,combining the RD algorithm with the image rotation correlation algorithm,and verifying it through simulation.It is found that this scheme can indeed reduce the error of the rotation parameter,and can better perform the cross-range scaling of the image and extract the target size information.