Autofocus algorithms for millimeter-wave 3-D FLoSAR

Three-dimensional (3-D) millimeter-wave (mm-Wave) Forward-Looking Synthetic Aperture Radar (FLoSAR) is an emerging technology that images targets in the forward direction of the flight path and holds the promise of high-resolution imaging by exploiting the unlicensed, wide bandwidth available at mm-Wave. This may be beneficial for applications such as self-landing, navigation, and collision-avoidance in a deteriorated vision environment. High angular resolution is difficult to achieve in FLoSAR because terrain points located symmetrically along the flight path have the same range and Doppler history. Additionally, the challenge at mm-Wave FLoSAR is to provide motion compensation because, at mmWave, GPS accuracy is insufficient to obtain platform position at subwavelength level, thereby leading to loss of resolution in reconstructed images. In this work, we investigate the phase gradient autofocus method for 3-D mm-Wave FLoSAR.