Factorized Geometrical Autofocus at UHF-band

Paper in proceeding, 2019

This paper describes an autofocus experiment at UHF-band. That is within the scope of factorized geometrical autofocus (FGA). The FGA algorithm is a base-2 fast factorized back-projection (FFBP) formulation with six free geometry parameters (per sub-aperture pair). These are tuned step-by step until a sharp image is obtained. This innovative autofocus technique can compensate completely for an erroneous geometry. The FGA algorithm has been applied successfully on an UWB data set, acquired by the LORA system (i.e. at UHF band). Before processing, we add errors due to a constant quadratic bias to the measured track. This emulates a drifting inertial measurement unit (IMU) and motivates the use of autofocus. The resulting FGA image is compared to a reference image and verified to be focused (even sharper actually). Hence, the FGA algorithm is fit for use at UHF-band.