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

Abstract

This paper 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. In this paper, we 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 paper is twofold. We first extend the approximated ML DoA estimation to the case of Non Uniform Linear Antennas (NULA) and we complete the procedure by a detection scheme. Second, we attest the validity of this new processing on real radar data. Hence, we 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.