Design of Wideband Intelligent Reflecting Surface for 5G Coverage Extension With Stable Beam Steering

This paper presents a novel wideband single-layer passive intelligent reflecting surface (IRS) designed to enhance 5G network coverage and ensure stable beam steering. The proposed IRS operates across the full spectrum of 5G mmWave bands, specifically targeting the n258 and n257 bands. The design features an upper layer composed of sub-wavelength unit cells, each with a periodicity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.43\lambda$</tex> at 26 GHz and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.46\lambda$</tex> at 28 GHz. The phase compensation on the IRS aperture, consisting of 40 × 40 unit cells and measuring 200 mm × 200 mm × 1.5 mm, is engineered to improve 5G signal quality in areas prone to signal degradation, with a 5G base station positioned 10 meters away. The IRS reflects incident 5G signals from the base station at an angle of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\theta_{i}=-15^{\circ}$</tex>, directing the enhanced signal to receivers and users at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\theta_{r}=30^{\circ}$</tex>. Both simulation and empirical results confirm that the proposed IRS effectively covers the entire 24 to 30 GHz millimeter-wave band, can enhance 5G signal strength and extend 5G coverage in areas where direct line-of-sight to the base station is obstructed or weak, ensures consistent beam steering performance across the frequency range.