New metamaterial structure with reconfigurable refractive index at 5G candidate band

Abstract

A new metamaterial structure with a reconfigurable refractive index for beam tilting in future fifth-generation (5G) networks has been designed and numerically investigated. The novel structure operates at 28 GHz and consists of a stairway-shaped resonator (SSR) printed on the top view of the substrate layer. The inductance and capacitance (LC) equivalent circuit model is introduced to estimate the electromagnetic behavior of the SSR unit cell. The circuit model data agreed well with the full-wave computer simulation technology (CST) simulation. The proper configuration of the SSR unit cell offers a very low loss of -0.26 dB. To control the refractive index of the proposed structure, two active components, PIN diodes, are formed in the gaps of the structure. Consequently, the SSR can be switched between four states with different refractive index values, which are -60, -14, 0, and -12 (Nicolson Ross Weir (NRW) method) and -58, -12.5, 1, and -10.4 (Robust Retrieval Method (RRM)) at 28 GHz. The return loss, insertion loss, and real parts of the refractive index are studied and investigated at each reconfigurable state. The copper strip and the measured S-parameters of the proposed PIN diode are used in the simulation to achieve reconfigurability.