  Automotive radars at the Terahertz (THz) frequency band have the potential to
be compact and lightweight while providing high (nearly-optical) angular
resolution. In this paper, we propose a bistatic THz automotive radar that
employs the recently proposed orthogonal chirp division multiplexing (OCDM)
multi-carrier waveform. As a stand-alone communications waveform, OCDM has been
investigated for robustness against interference in time-frequency selective
channels. The THz-band path loss, and, hence, radar signal bandwidth, are
range-dependent. We address this unique feature through a multi-carrier
wideband OCDM sensing transceiver that exploits the coherence bandwidth of the
THz channel. We develop an optimal scheme to combine the returns at different
range/bandwidths by assigning weights based on the Cramer-Rao lower bound on
the range and velocity estimates. Numerical experiments demonstrate improved
target estimates using our proposed combined estimation from multiple
varied-attenuation THz frequencies.
