DoA Estimation in Fully-Connected Hybrid Receivers: Full Coverage and Refined Accuracy

In this paper, we introduce a novel approach for estimating the direction of arrival (DoA) in fully-connected hybrid analog/digital receivers. The key insight is that the analog combiner projects received signals onto the spatial sector it spans, causing signals from DoAs outside this sector to be significantly attenuated or nullified. Based on this observation, we develop two algorithms to ensure full spatial coverage and enhance DoA estimation accuracy. The first algorithm performs coarse estimates using an exhaustive set of analog combiners, each covering distinct subspaces that collectively span the entire space. To improve the precision of these estimates, we propose a second, iterative algorithm that progressively narrows the search window until convergence is achieved. 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.