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

TL;DR

This paper investigates how practical antenna misalignments affect the near-field boundary in terahertz communications, providing analytical models and simulations to guide system deployment.

Contribution

It introduces new analytical expressions for near-field boundary considering antenna misalignments in ULA and UPA configurations, filling a key gap in THz system modeling.

Findings

Misalignments significantly alter the near-field boundary.

Derived formulas match simulation results.

Guidelines for realistic THz system deployment.

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.