Direction of Arrival estimation of two moving targets using a time division multiplexed colocated MIMO radar

A Multiple-Input-Multiple-Output (MIMO) radar with colocated transmit and receive antennas has a larger virtual aperture compared to the corresponding Single-Input-Single-Output (SIMO) radar. Therefore, it can achieve a more accurate Direction of Arrival (DOA) estimation. Due to the Doppler effect, a target moving relative to the radar system results in an additional phase shift of the baseband signal. In general, this leads to a decrease in the DOA estimation accuracy. We consider time division multiplexed (TDM) MIMO radars and derive the Cramer-Rao Bound (CRB) for the DOA and Doppler frequency estimation of two moving targets. This is done for general TDM schemes. This enables to compare the achievable accuracy for different TDM MIMO radars. We derive conditions for TDM schemes which lead to a decoupling of the Doppler frequencies and DOAs in the CRB. Hence a CRB of DOAs can be achieved which is as small as if the Doppler frequencies are known a priori. We define a statistical resolution limit to separate both targets with the help of the CRB and compare the resolution of a TDM MIMO radar to that of a SIMO radar.