Analysis of Autofocus Algorithms in Near-Range Wide-Angle UAV-SAR Imaging

Rapid developments in Unmanned Aerial Vehicles and highly integrated radar systems allow for innovative synthetic aperture radar concepts in close-range high-resolution applications. However, the stringent position accuracy requirements of radar imaging pose a challenge for state-of-the-art position sensors. While data-driven correction approaches have been used successfully in airborne systems, they are rarely in use in close-range scenarios. This paper presents a theoretical analysis of the effects of antenna position inaccuracies on close-range radar imagery. Based on a theoretical approach, an upper bound for the performance of phase-only autofocus algorithms is derived. The applicability of two recently published algorithms in near-range SAR is shown using a Monte Carlo simulation framework and demonstrated on experimental data-sets.