Design of Intelligent Reflective Surface Unit Cell for 5G mmWave Applications

This paper presents a single bit millimeter wave (mmWave) intelligent reflective surface (IRS) unit cell for use in 5G communication enhancement. A PIN diode switch is used to introduce a 180° phase shift in reflection mode between ON and OFF state. The geometry of the top layer of the unit cell allows for transverse electric (TE) polarized reflection with an angular stability of 30°, both in azimuth and elevation plane. The design is intended for use in the n257 FR-2 band for 5G applications with the center frequency at 28 GHz. The proposed unit cell design covers a bandwidth of 3 GHz while achieving the required phase difference of $\mathbf{180}^{\circ}\pm \mathbf{20}^{\circ}$ . The magnitude of reflection is greater than 78.5% throughout the band. These performance characteristics allow the proposed unit cell to be useful in digitally programmable metasurface applications with features such as beam focusing, beam steering and beam scattering.