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Fm Stepped Radar Signal And Inverse Synthetic Aperture Radar Imaging Method

Posted on:2006-06-30Degree:MasterType:Thesis
Country:ChinaCandidate:H B LiFull Text:PDF
GTID:2208360152988955Subject:Aircraft design
Abstract/Summary:PDF Full Text Request
High-resolution imaging radar is widely used in military applications. Usually, high range resoluton is realized by using wideband signal. In order to obtain high range reslution, we studied the modulated frequency stepped signal (FJB, frequency jump burst) in depth. At the same time, we applied this signal on ISAR system, and studied the imaging method. The research on FJB signal includes the following aspects: (1) We proposed a frequency domain subaperture processing method for compression. After analyzing the ambiguity function, the characteristics are shown. (2) In view of the big sidelobes and grating lobes after compression, we studied several methods to overcome the drawbacks, i.e. linear windowing techniques, and nonlinear windowing techniques, such as SVA (spatial variant apodization) and DA (dual apodization). (3) We proposed a tangent-function-shape nonlinear stepped-frequency chirp model to achieve much lower sidelobes. (4) We analyzed the influence of the radial velocity on FJB and showed the importance of motion compensation. Besides these, we also studied the method for parameter design and the existing problems for FJB signal. The targets imaged by ISAR are usually non-cooperative. So motion compensation is a key technique in ISAR imaging processing. Motion compensition is usually divided into two steps: range alignment and phase compensation. The thesis reviewed methods for ISAR imaging and motion compensition. In order to speed up the processing and improve the precision, we proposed a new algorithm based on the modification of conventional algorithm. We firstly intercept a part of the whole image, with dominant scattering from target included, and then perform envelope correlation operation. We also apply interpolation and SVA technique to further improve the alignment accuracy. Computer simulations validated the proposed method with satisfatory results. In the end, the thesis studied the ISAR imaging method based on FJB, i.e. Range-Doppler method. Main work focused on the motion compensation method in view of FJB used for ISAR imaging.
Keywords/Search Tags:Frequency Jumped Burst (FJB), Inverse synthetic aperture radar (ISAR), Matched filter, Ambiguity function, Motion compensiton
PDF Full Text Request
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