Investigation of Superdirectivity in Planar Holographic Arrays

This paper studies the superdirectivity characteristics of uniform rectangular arrays (URAs) for holographic multiple-input multiple-output systems. By establishing a mathematical directivity model for the URA, an analytical expression for the maximum directivity is derived. Accordingly, systematic analysis is performed in conjunction with numerical simulations. Results show that the directivity can be significantly enhanced via rational utilization of coupling effects. However, this enhancement yields diminishing returns when antenna spacings transition to deep sub-wavelength scales. This study provides a theoretical basis for the design of superdirective URAs and offers valuable insights for holographic array optimization in 5G/6G communication systems.