DoA Estimation for Hybrid Receivers: Full Spatial Coverage and Successive Refinement

We develop two novel algorithms for estimating the direction of arrival (DoA) of multiple sources in fully-connected and partially-connected hybrid analog/digital (HAD) receivers. The first algorithm is based on the observation that the analog combiner projects received signals on a particular subspace, causing the signals corresponding to particular DoAs to be heavily attenuated. Thus, an analog combiner defines spatial sectors, beyond which the DoAs are practically undetectable. To address this difficulty, we perform DoA estimation over an exhaustive set of analog combiners spanning distinct subspaces. To refine the estimates generated by this algorithm, we develop an exponentially-converging algorithm wherein the search window is successively narrowed until convergence. Cramér-Rao lower bounds on the root-mean-square error of the proposed algorithms are derived and the superiority of these algorithms over their existing counterparts is established through numerical simulations.