  Automotive synthetic aperture radar (SAR) systems are rapidly emerging as a
candidate technological solution to enable a high-resolution environment
mapping for autonomous driving. Compared to lidars and cameras,
automotive-legacy radars can work in any weather condition and without an
external source of illumination, but are limited in either range or angular
resolution. SARs offer a relevant increase in angular resolution, provided that
the ego-motion of the radar platform is known along the synthetic aperture. In
this paper, we present the results of an experimental campaign aimed at
assessing the potential of a multi-beam SAR imaging in an urban scenario,
composed of various targets (buildings, cars, pedestrian, etc.), employing a 77
GHz multiple-input multiple-output (MIMO) radar platform based on a mass-market
available automotive-grade technology. The results highlight a centimeter-level
accuracy of the SAR images in realistic driving conditions, showing the
possibility to use a multi-angle focusing approach to detect and discriminate
between different targets based on their angular scattering response.
