Robust DoA estimation in case of multipath environment for a sense and avoid airborne radar

This study deals with the sense and avoid problem for an helicopter. The objective of such a system is to early detect collision targets (typically high‐voltage wires). The direction of arrival (DoA) of the target is then a crucial information. In severe multipath environments (flight over a river, for instance), classical DoA estimation schemes dramatically degrade. The authors make use of a method based on the maximum likelihood (ML) principle that can resolve two highly correlated and close targets. The major drawback of ML algorithms, namely the computational burden, is removed using an approximation for closely space targets. The contribution of this study is twofold. The authors first extend the approximated ML DoA estimation to the case of non‐uniform linear antennas and complete the procedure by a detection scheme. Second, they attest the validity of this new processing on real radar data. Hence, they show that the proposed procedure is able to detect a high‐voltage wire, over a river, at ranges up to 1 km, where a capon beamformer cannot.