Research On Imaging Of Ship Target Based On Bistatic ISAR

Inverse synthetic aperture radar (ISAR) can prove target imaging by usingrelative rotation between the radar and target. We can achieve distance resolution bymeans of time delay of the target echo between the different distance to radarscattering points; At the same time, because of the rotation of the target, the pointson the same distance can produce different doppler, we can also achieve azimuthresolution.After years of development and evolution, the single base of ISAR imagingtechnology has obtained the huge development. But the single base ISAR still existstwo disadvantages: it exists the contradiction between PRF and radar range.Measuring distant goal needs a long pulse firing interval; In the modern high-techelectronic war, single base ISAR can be easily spotted by the enemy and destroyed.So this paper studies a kind of new imaging technology-bistatic ISAR imagingtechnology. The bistatic ISAR imaging technology is a good way to solve the singlebase of ISAR imaging’s disadvantages in the practical application.First, we explain the basic principle of ISAR imaging, including themathematical model of ISAR imaging, ISAR imaging resolution, basic algorithmsof ISAR imaging and two-dimensional turntable imaging simulation.Establish the turntable model of bistatic ISAR imaging moving targets imaginggeometric model; Then, establish the model of moving target; Discusses theresolution of bistatic ISAR2-d and double-base seed’s influence on the imagingresolution; Echo processing, detailed introduces the characteristics of linearfrequency modulation signal and pulse compression technology (including thematched filtering technique and line frequency modulation technology); For movingtargets for motion compensation, envelope alignment we using cross-correlationaccumulation method, phase correction using the doppler center tracking method.Target motion of ships at sea is studied in detail characteristics, the constructed3d ship targets scattering point model. Respectively studies the3d ship targetswiggle-side swing, pitch and yaw of each component of the impact of the changeof target doppler frequency, brings to the imaging results were analyzed respectively,and do the simulation.In the high sea condition, rotation or speed change of the ship targets will leadto time-varying doppler frequency when the ship target are under the condition of3D rotation and variable speed rotation. The traditional R-D imaging (range doppleralgorithm) will be fuzzy when imaging. In this case,we can only obtain the shiptarget clear imaging by analyzing ship target doppler frequency of each scattering point on instantaneous frequency estimation. This requires special time-frequencyanalysis method which have stronger ability to suppress the cross terms and hightime-frequency agglomeration. For instantaneous imaging algorithm, this chapterselect several typical linear and bilinear distribution (STFT, SPEC, WVD andSPWD). Through theoretical analysis and3d motion of bistatic ISAR ships targetimaging simulation shows that in the distribution, the spectra (SPEC) without theinfluence of cross terms, and a small amount of calculation and has a certainpractical value.