Super-Beamforming in Holographic MIMO

2026-05-19

AI Summary

This work addresses the fundamental limitation of conventional holographic MIMO systems, where half-wavelength antenna spacing restricts beamforming gain to linear scaling with the number of antennas. By deliberately reducing inter-element spacing to introduce controlled mutual coupling, the authors propose a novel approach that synthesizes an endfire super-beam. Theoretical analysis reveals, for the first time, that when the spacing is slightly below half a wavelength and losses are low, mutual coupling enables endfire gain to scale quadratically with the number of antennas. Building upon mutually coupled antenna arrays, this study establishes a new holographic MIMO beamforming framework that significantly enhances directivity and overcomes the classical linear gain bottleneck inherent in conventional array architectures.

Abstract

The conventional linear scaling of beamforming gain with the number of antennas is not a fundamental physical limitation, but rather a consequence of the half-wavelength spacings that minimize mutual coupling. Relaxing this constraint facilitates beamforming gains exceeding those of uncoupled arrays along specific directions. This paper shows that, when antenna losses remain sufficiently small, mutual coupling enables the synthesis of super-beams whose endfire gain scales quadratically with the number of antennas. Notably, this quadratic scaling does not necessarily require vanishing spacings, but emerges for spacings slightly below half wavelength as the array aperture increases.

Problem

• Super-Beamforming
• Holographic MIMO
• Mutual Coupling
• Beamforming Gain
• Antenna Arrays

Innovation

• Super-Beamforming
• Holographic MIMO
• Mutual Coupling
• Quadratic Gain Scaling
• Sub-half-wavelength Spacing