Enhancing Unambiguous Velocity in Doppler-Division Multiplexing MIMO Radar

In the conventional Doppler-division multiplexing (DDM) multiple-input multiple-output (MIMO) radar, the unambiguous velocity is restricted by the number of transmit antennas. In this paper, we propose a novel approach called Doppler offset DDM (DO-DDM) MIMO to resolve the ambiguous velocity for automotive radar applications. In addition to the Doppler offsets applied to every transmit antenna as in DDM MIMO, small extra Doppler offsets are introduced to some transmit antennas, which makes the resulting range-Doppler (RD) spectrums become asymmetric. Unlike the DDM MIMO, the peak positions in every RD spectrum are no longer the same, and the ambiguous velocity can be resolved by finding the order of the peak position differences in the Doppler domain. Simulation results show the effectiveness of the proposed approach.