Researchers from the University of Oulu have redefined the near-field propagation boundaries for phased array antennas, demonstrating that the Fraunhofer distance is practically four times wider and the Fresnel distance is approximately 2.8 times higher than traditional single-element models suggest. The study analytically characterizes these regions across different observation angles, revealing that the non-radiating reactive zone remains consistently under half a wavelength regardless of array size. Additionally, the work confirms the feasibility of 3D spot beam focusing in the radial domain for large planar arrays and proposes algorithms to align focal points for smaller configurations. These findings provide a critical foundation for 6G networks, where extended near-field regions and additional degrees of freedom will enable new wireless applications.
Keywords: phased array antennas, near-field propagation, Fraunhofer distance, 3D beam focusing, non-radiating region