Electromagnetic Modeling of Holographic Intelligent Reflecting Surfaces at Terahertz Bands

TL;DR

This paper develops an electromagnetic model for holographic intelligent reflecting surfaces operating at terahertz frequencies, addressing near-field effects and wavefront curvature to improve understanding of their propagation and beamfocusing capabilities.

Contribution

It introduces a novel electromagnetic model for THz IRSs that accounts for near-field effects and spherical wavefronts, advancing beyond traditional far-field assumptions.

Findings

Derived a new expression for path loss and beampattern of holographic IRSs.

Analyzed the near-field response of IRSs in the Fresnel zone.

Provided insights into beamfocusing capabilities of THz IRSs.

Abstract

Intelligent reflecting surface (IRS)-assisted wireless communication is widely deemed a key technology for 6G systems. The main challenge in deploying an IRS-aided terahertz (THz) link, though, is the severe propagation losses at high frequency bands. Hence, a THz IRS is expected to consist of a massive number of reflecting elements to compensate for those losses. However, as the IRS size grows, the conventional far-field assumption starts becoming invalid and the spherical wavefront of the radiated waves must be taken into account. In this work, we focus on the near-field and analytically determine the IRS response in the Fresnel zone by leveraging electromagnetic theory. Specifically, we derive a novel expression for the path loss and beampattern of a holographic IRS, which is then used to model its discrete counterpart. Our analysis sheds light on the modeling aspects and beamfocusing capabilities of THz IRSs.