60 GHz synthetic aperture radar for short-range imaging: Theory and experiments

We report on experimental results, and associated theory, for a 60 GHz synthetic aperture radar (SAR) testbed for short-range (sub-meter) imaging. Our testbed consists of a monostatic radar with synchronized transmitter and receiver, with lateral motion (over 10-30 cm) providing the SAR geometry, and range resolution provided by stepped frequency continuous wave (SFCW) signals covering a band exceeding 6 GHz. Sub-centimeter (cm) level resolution is achieved in both cross-range and slant-range. For stationary targets, platform movement provides a means of emulating a system with multiple monostatic transceivers, and exploring the impact of the spatial distribution of such transceivers. In particular, sparse spatial sampling causes significant deterioration in cross-range resolution under classical SAR image reconstruction, which is based on a point scatterer signal model. We show that performance can be greatly improved by modeling objects using “patches,” where a patch is defined as a continuum of point scatterers with (approximately) the same reflectivity. Estimation-theoretic quantities such as the Cramer-Rao Lower Bound (CRLB) and normalized cross-correlation between responses for nearby targets, are derived for both point-and patch-based signal models.