Design of Polarisation Reconfigurable Millimeter-Wave MIMO Antenna

Abstract

A 2×2 multiple-input multiple-output (MIMO) of four reconfigurable loops antenna for millimeter-wave (mmWave) communication systems is proposed. The antenna system supports three polarisation modes and is designed to operate at 28 GHz. Polarisation reconfigurability is achieved by electrically switching two PIN diodes. For both circular polarisation senses, a total efficiency of approximately 76% and a maximum gain of around 7 dBic are obtained at the operated frequency. Additionally, the antenna provides linear polarisation (LP) with a total efficiency of 65% and a maximum gain of 6.1 dBic when the two PIN diodes are unbiased. The envelope correlation coefficient (ECC) is found to be less than 0.002 with a diversity gain (DG) greater than 9.9 at 28 GHz. With an overall size of 30 mm × 30 mm, the proposed MIMO antenna features a small footprint and simple planar configuration.