Study of Virtual Spherical Modes for Multi-Target Angle of Arrival Estimation

Antennas capable of selectively synthesizing desired spherical modes offer a compact alternative to classical phased arrays, offering beamforming from a limited volume. This property makes them a good candidate for size- and weight-constrained platforms. In this paper we study the application of sparse sensing to such antennas, which allows the generation of additional virtual spherical modes for the receiver antenna. This expanding the system's degrees of freedom (DoF) and improving the accuracy of angle of arrival (AoA) estimation. By selecting optimized subsets of the original spherical modes, one can produce the same virtual mode set while reducing redundancy, leading to more efficient and accurate multi-target detection. The proposed approach demonstrates that compact multiport antennas can maintain high-resolution performance, offering an effective solution for AoA estimation in size-constrained applications.