Application Of Time-frequency Analysis On The Radar Imaging

Inverse synthetic aperture radar (ISAR) can extract informations of image formation from the long-range and non-cooperation movement targets (such as aircraft、rockets)in any time,and play an indispensable role on target recognition、anti-satellite、radar astronomy and so on, it earns widespread respect and rapid development, because the object of study is no longer a smoothly moving target but all kinds of complex moving target, the echo signal of these complex moving target is non-cooperation, it is difficult to determine the target information and movement route, it is hard for us to carry on the accurate motion compensation, so the traditional RD algorithm is not suitable for non-cooperation movement targets. To consider the character of echo signal, an accurate time-frequency analysis method must be used to obtain the time-frequency data accurately from each scattering points and to process the imaging.This paper make a further study on motion compensation and ISAR imaging, by introducing the time-frequency analysis technology can get more clear image. The main research contents of this paper includes the following:(1) Using variety of motion compensation methods to compare the imaging results, it make a variety of compensation for distance correction and phase reference, it proposes Adaptive Joint Time Frequency (AJFT) which bases on self-adaption, this method can make a good focus for the non-cooperative targes and obtain good imaging effect.(2) This paper mainly studies the time-frequency ISAR imaging. aiming at the shortcomings and the insufficiency of the traditional Range-Doppler algorithm, applying joint time-frequency analysis technique can get good effect as the goal like. It analyzed and compared several time-frequency resolutions which is common used and cross study of its impact. Through the simulation results, we can know that the time-frequency analysis method is superior to the traditional Range-Doppler method.(3) According to the presence of cross terms for the multicomponent LFM signals, this paper researches the idea of combining the Radon-WVD transform CLEAN which can successive estimate the parameters of each component. According to the parameters we can understand the change about instantaneous frequency of each component, thus can improve the image quality.(4) To research variety of the Linear distribution and secondary distribution, and to compare the performance of many kinds of time and frequency change such as STFT、WVD、 CWT and so on. In this paper, we introduce the imaging theory and the traditional Fourier transform has been unable to solve non-stationary moving target Doppler change, which will result in the target image blur. In order to solve this problem, we introduced time-frequency analysis method for motion compensation and made in-depth study for the imaging process and cross-term suppression. The advantages of time-frequency analysis can be fully reflected thought the theory and formula, and the simulation of time-frequency analysis can get good imaging results, the following is the detailed content.