Multivariate DoA Estimation of Electromagnetic Waves Arriving Spherical Antenna Array under Mutual Coupling Effects Using Higher-Order Pseudo Intensity Vector Technique

Spherical Antenna Array (SAA) can receive Electromagnetic (EM) waves with equal signal strength, regardless of polarization, Direction-of-Arrival (DoA), or angle of arrival. However, estimating DoA in a multi-source environment with a low Signal-to-Noise Ratio (SNR) remains a significant research challenge that requires technical attention. This paper introduces a novel feature-the Higher-Order Pseudo-Intensity Vector (HoPIV), derived from data obtained with an SAA. Utilizing the unique properties of the reactive intensity vector derived from HoPIV, a method is proposed for identifying time-frequency points dominated by the direct path. Consequently, a DoA estimation method is introduced, leveraging the high spatial resolution of HoPIV to enhance DoA estimation performance with a high degree of accuracy. Numerical simulations, which account for mutual coupling effects, demonstrate how the developed technique outperforms state-of-the-art methods, even at low SNR. In addition, the practical deplorability of the HoPIV-based method against baseline methods is investigated using experimental data (incorporating factors such as mutual coupling, multipath fading effects, and hardware imperfections) in electromagnetics vis-à-vis an SAA, which, in the end, the ground truth to test and evaluate any method. The results show that the proposed HoPIV-based method is preferred over the state-of-the-art method.