A Unified Formulation of SAR Raw Signals From Extended Scenes for All Acquisition Modes With Application to Simulation

Synthetic aperture radar (SAR) systems can generate microwave images by using different acquisition modes: stripmap, spotlight, scanSAR, and the more recently developed sliding spotlight and Terrain Observation by Progressive Scans (TOPSAR). The proper mode to be used is chosen according to the desired spatial resolution and coverage. In this paper, we present a unified formulation able to express raw signals of all acquisition modes. This formulation is then employed to show that both sliding spotlight and TOPSAR raw signal simulation of extended scenes can be achieved by using an improved version of the approach previously proposed by some of the authors for the sliding spotlight case. This approach implies a 1-D range Fourier-domain processing, followed by 1-D azimuth time-domain integration, and it can also precisely account for sensor trajectory deviations for any acquisition mode. Effectiveness of the proposed simulation scheme is assessed by using numerical examples. Results show that its computational load is much lower than the one of the time-domain approaches, and the obtained raw signals are in very good agreement with the exact ones. Finally, examples of simulations of SAR signals relative to extended, both canonical and realistic, scenes are also reported.