Improving ISAR imaging quality based on minimum entropy method

Using the classical ISAR imaging method based on the Fourier transform it is difficult to form an image of good quality in the case of a large rotating angle or a nonuniformly rotating target. We first establish the signal models for the two cases above. Then an imaging method for compensating the linearly varying Doppler frequency of the scatterers is proposed. The frequency modulating rate of the Doppler frequency of the scatterers is estimated by means of the minimum Shannon entropy. It is demonstrated by experimental results that the proposed method can alleviate the cross-range cell migration of the scatterers and the imaging quality can be greatly improved.