Research On Inverse Synthetic Aperture Radar And Micro-Motion

Inverse Synthetic Aperture Radar(ISAR) can obtain images of non-cooperative targets with all-weather, all-time and far-distance capabilities. ISAR has broad application prospects in military and civilian fields. This dissertation focuses on research about algorithms for range alignment and micro-doppler extraction. The main work in this dissertation can be shown as follows.This dissertation proposes an idea that it is feasible to use Chebyshev polynomials to fit the target’s trajectory and accomplish motion compensation in the frequency domain with pulse compression. Because arthogonality between terms of Chebyshev polynomials, Chebyshev polynomials perform better than Taylor polynomials. The coefficients of Chebyshev polynomials can be estimated by Matching Pursuit(MP). However, different from common MP problems with discrete parameters space, the intervals of parameters such as velocity and acceleration are continuous. Simulated Annealing is used to search the optimum atom in continuous parameters space. Measured data processing shows that the alforithm based on MP works better that the popular range alignment algorithm based on entropy. Besides, in this dissertation, long-burst data is divided into several short-burst data segments and each one is aligned in range. Then these aligned sengments are merged into long-burst data. When dealing with measured data, this method functions better that dealing with long-burst data directly.On the condition that the signals of a range cell mainly belong to one scatterer, it is feasible to compensate the rotation first and then estimate the micro-motion frequency with a cosinoidal model. Simulations have validitied the method. And in the part of measured data processing, this method is then used to analyze the range cell where the scatter of the plane wing locates and the results show that the micro-motion’s frequency is about 2-3Hz.