Maximum likelihood sub-arrayed MIMO radar receiver

There has been recent interest in MIMO radars which employ sub-arrays at the transmitter. This architecture allows a trade-off between the coherent beamforming gain of a phased array antenna and the transmit beampattern diversity offered by a MIMO radar with full transmit diversity, while maintaining a relatively simple implementation in the transmit hardware. In this work we study the maximum likelihood (ML) receiver for a transmit sub-arrayed MIMO radar, for estimating the direction of arrival of multiple targets. We develop the likelihood function for an orthogonal sub-arrayed MIMO radar for receiver architectures with and without a matched-filter bank. The maximisation of these likelihood functions form multi- dimensional optimisation problems which can be solved using a variety of sub-optimal numerical algorithms.