Random Repetition Rate SAR Imaging

Typically, SAR radar uses periodic coherent waveforms: this periodicity results in a certain unambiguous Range-Doppler domain or, equivalently, a certain Range-Azimuth domain. To obtain usable SAR images, the antenna beam must be directional enough to illuminate only a part of this Range-Azimuth domain. In some cases, such as a space too small to place a sufficiently large antenna, a high platform speed or a large distance from the mapped area, etc., there is no solution to this ambiguity problem. This results in a poor signal-to-ambiguity ratio. A possible solution is to “break” these periodicity ambiguities by using aperiodic waveforms. In this paper, we are in a restricted framework where the objective is to image a sparse scene of a few objects (ships) within a homogeneous environment, typically sea clutter.