Kilian Rambach

Colocated MIMO radar: Cramer-Rao bound and optimal time division multiplexing for DOA estimation of moving targets

Multiple-Input-Multiple-Output (MIMO) radars with colocated transmit and receive antennas offer the advantage of a larger (virtual) aperture compared to a conventional Single-Input-Multiple-Output (SIMO) radar. Hence a higher accuracy of the estimated direction of arrival (DOA) of a target can be achieved. In general, the accuracy of DOA estimators decreases in a MIMO radar if the target moves relative to the radar, because the motion causes an unknown phase change of the baseband signal due to the Doppler effect. We compute the Cramer-Rao bound (CRB) of DOA estimation of a non-stationary target for a MIMO radar with colocated antennas for a general time division multiplexing (TDM) scheme. This allows a quantitative comparison of different MIMO and SIMO radars. Moreover, we derive an optimal TDM scheme such that the CRB is as small as in the stationary case. The results are confirmed by simulations.

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.

Optimal time division multiplexing schemes for DOA estimation of a moving target using a colocated MIMO radar

A Multiple-Input-Multiple-Output (MIMO) radar can achieve a higher accuracy in direction of arrival (DOA) estimation compared to a corresponding Single-Input-Multiple-Output (SIMO) radar due to its larger virtual aperture. If the target is moving relative to the radar, an additional phase shift is introduced into the baseband signal because of the Doppler effect. Hence the Doppler frequency has to be estimated in addition to the DOA. In general, this decreases the DOA estimation accuracy. We investigate MIMO radars using time division multiplexing (TDM). We derive the Cramer-Rao bound (CRB) for a moving target and a general TDM scheme and compare it to other radar systems. Moreover we derive optimal TDM schemes which minimize the CRB under different constraints.

Direction-of-arrival estimation and Cramer-Rao bound for multi-carrier MIMO radar

Multi-carrier (MC) multiple-input multiple-output (MIMO) radar was recently applied to build sparse virtual arrays with a large aperture for a high-accuracy direction-of-arrival (DOA) estimation. The resulting grating lobes (DOA ambiguities) were resolved using multiple carriers. One problem of MC-MIMO is the coupling of the unknown parameters range and DOA. In this contribution, we study this range-DOA coupling for MC-MIMO systems. We consider both Cramer-Rao bound (CRB) of these parameters and their estimation. We show that a suitable choice of the coordinate system decouples range and DOA parameters in both CRB and estimation. This enables a sequential range and DOA estimation instead of a more complex joint estimation. Explanations of this phenomenon are given and simulation results confirm the theoretical findings.