Superdirective antenna arrays-aided wireless communications: a tutorial and review of recent advances

Superdirective antenna arrays, characterized by their ability to achieve extremely high directivity in compact antenna arrays, hold significant promise for advancing wireless communications. This review provides a comprehensive overview of the theoretical foundations, practical considerations, and recent advances in superdirective antenna array-aided wireless communications. We begin with a review of classical superdirectivity theory. We then discuss the challenges that hinder the practical use of superdirective antenna arrays. Specifically, mutual coupling, high sensitivity, narrow bandwidth, poor radiation efficiency and hardware limitations are discussed, and recent efforts to address them are systematically reviewed. Emerging applications, such as multi-user communications, superdirective antenna pairs, and superdirective holographic array design and Electromagnetic Hybrid Beamforming (EHB) are also discussed. In addition, superdirective antenna array prototypes are surveyed. Finally, the potential research directions are also discussed for future development, including impedance matching, antenna design, integrated performance optimization, hardware implementation, and cross-layer system integration. This work aims to bridge the gap between theoretical developments and practical applications, serving as a valuable reference for both researchers and engineers in the field.