Reconstruction of ISAR image by time-frequency distribution series

Inverse synthetic aperture radar (ISAR) uses the target´s motion to generate images on the range-Doppler plane. In the conventional ISAR system, the Doppler spectra are computed by the Fourier transform. Due to the target irregular translational and rotational motion, the Doppler frequencies change over the time. Consequently, the Fourier transform based ISAR image may become blurred. To overcome this problem, the joint time-frequency transform is introduced to estimate the Doppler spectra. Because the joint time-frequency transform is able to resolve the instantaneous Doppler frequencies, the resolution of the resulting ISAR images are significantly improved. Moreover, the proposed ISAR system is not only effective, but also amenable to hardware implementation