  Due to the rapid increase in 76 GHz automotive spectrum use in recent years,
wireless interference is becoming a legitimate area of concern. However, the
recent rise in interest of automated vehicles (AVs) has also spurred new growth
and adoption of low frequency vehicle-to-everything (V2X) communications in and
around the 5.8 GHz unlicensed bands, opening the possibility for communications
spectrum reuse in the form of joint radar-communications (JRC). In this work,
we present a low frequency 5.9 GHz side-looking polarimetric synthetic aperture
radar (SAR) for automotive use, utilizing a ranging waveform in a common low
frequency V2X communications band. A synthetic aperture technique is employed
to address the angular resolution concerns commonly associated with radars at
lower frequencies. Three side-looking fully polarimetric SAR images in various
urban scenes are presented and discussed to highlight the unique opportunities
for landmark inference afforded through measurement of co- and cross-polarized
scattering.
