Randomized stepped frequency ISAR imaging

Linearly stepped frequency (LSF) waveforms are widely equipped in inverse synthetic aperture radar (ISAR), where the frequency is linearly altered with a fixed frequency step in each burst. ISAR employing randomized stepped frequency (RSF) modulation improves the rang-Doppler resolution, widens the unambiguous Doppler window, and enhances performance in electronic counter-countermeasures (ECCM). However in RSF radar, range profiles can severely spread when the radial velocity is unknown. In this paper, we analytically derive the return signal model of a target rectilinearly moving at invariable speed, and devise a new algorithm to estimate the velocity and reconstruct the image of target. Numerical results demonstrate the effectiveness of the algorithm.