Impact of Antenna Arrays Misalignment on the Near Field Distance in Terahertz Communications

2025-11-01

AI Summary

Existing Fraunhofer near-field boundary formulations assume perfect alignment of antenna arrays, neglecting spatial misalignment—induced by mobility or mechanical imperfections—in terahertz (THz) communications. This work establishes, for the first time, a theoretical near-field boundary model for uniform linear and planar arrays (ULA/UPA) that explicitly incorporates both translational and rotational misalignments between transmitter and receiver arrays. Leveraging electromagnetic wave propagation theory and rigorous array geometric modeling, we derive exact analytical expressions and practical closed-form approximations for the near-field boundary under misalignment. Numerical simulations systematically characterize how misalignment compresses and shifts the near-field region. The proposed framework significantly improves near-field distance prediction accuracy, providing critical theoretical foundations and design guidelines for array configuration, beamforming, and channel modeling in practical THz systems.

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Abstract

The extremely short wavelength of terahertz (THz) communications leads to an extended radiative near-field region, in which some canonical far-field assumptions fail. Existing near-field boundary formulations (Fraunhofer distance) for uniform linear/planar array (ULA/UPA) configurations assume ideal alignment between transceivers, overlooking practical misalignments caused by mobility or mechanical imperfections. This paper addresses this critical gap by analyzing the impact of spatial misalignment on near-field distance calculations in THz systems. We derive exact analytical expressions and simplified approximations for the near-field boundary in both ULA--ULA and UPA--UPA configurations under arbitrary misalignment offsets. Through numerical simulations, we validate our theoretical models and quantify how misalignment reshapes the near-field region. These findings provide essential guidelines for optimizing THz system deployment in realistic scenarios.

Problem

• Analyzing misalignment impact on near-field distance in THz communications
• Deriving analytical expressions for near-field boundary under misalignment
• Quantifying how misalignment reshapes the near-field region

Innovation

• Derives analytical expressions for misaligned near-field boundaries
• Provides simplified approximations for ULA and UPA configurations
• Quantifies misalignment impact through numerical validation