A flexible design strategy for three-element non-uniform linear arrays

This paper illustrates a flexible design strategy for a three-element non-uniform linear array (NULA) aimed at estimating the direction of arrival (DoA) of a source of interest. Thanks to the spatial diversity resulting from non-uniform sensor spacings, satisfactory DoA estimation accuracies can be achieved by employing a very limited number of receiving elements. This makes NULA configurations particularly attractive for low-cost passive location applications. To estimate the DoA of the source of interest, we resort to the maximum likelihood estimator, and the proposed design strategy is obtained by constraining the maximum pairwise error probability to control the errors occurring due to outliers. In fact, it is well known that the accuracy of the maximum likelihood estimator is often degraded by outliers, especially when the signal-to-noise power ratio does not belong to the so-called asymptotic region. The imposed constraint allows for the defining of an admissible region in which the array should be selected. This region can be further modified to incorporate practical design constraints concerning the antenna element size and the positioning accuracy. The best admissible array is then compared to the one obtained with a conventional NULA design approach, where only antenna spacings multiple of λ/2 are considered, showing improved performance, which is also confirmed by the experimental results

Outlier Rejection Approach for Direction of Arrival Estimation in Low SNR Conditions

This paper deals with the problem of Direction of Arrival (DoA) estimation through a Non-Uniform Linear Array (NULA) in low signal-to-noise ratio (SNR) conditions. By exploiting the spatial diversity offered by the different subarrays of a given NULA configuration, we propose a simple strategy that aims at identifying and discarding DoA estimates that are recognized to be outliers caused by the generally high level of the employed array beampattern sidelobes. The effectiveness of the proposed algorithm is shown on both simulated and experimental data for a drone surveillance application in the Wi-Fi band