Compact Elliptical Slot Millimeter-Wave MIMO Antenna for 5G Applications

Abstract

This study introduces a novel, highly compact broadband millimeter-wave (mm-wave) antenna design and its Multiple-Input-Multiple-Output (MIMO) configuration proposed for 28 GHz applications targeting 5G networks. The antenna is designed over a 0.25 mm thick Rogers RT5880LZ substrate having a relative dielectric permittivity of 2 and an overall size of 16 mm × 16 mm. Its MIMO configuration utilizes polarization diversity and includes four elliptical-slot radiators integrated with microstrip-line structures, specifically optimized for 28 GHz operation. The performance of the proposed mm-wave MIMO configuration is validated through simulation of its S-parameters using CST software and measurements obtained with a vector network analyzer (VNA). The proposed antenna demonstrates excellent S-parameter performance, achieving a gain of up to 6 dBi and a radiation efficiency of 94% across the operational frequency band. Each antenna element exhibits an impressive wide operating bandwidth of 9 GHz, spanning from 22.2 to 31.4 GHz at a − 10 dB threshold. Evaluations of the MIMO system’s performance indicate promising results, including an exceptionally low envelope correlation of about \({10}^{-5}\) and a diversity gain of around 10 dB throughout the operating bandwidth. The design also ensures significant isolation between MIMO elements without requiring decoupling structures. A physical prototype of the proposed antenna is fabricated and subjected to measurements, depicting a strong corelation between the measured and simulated data, with some minor variations attributed to fabrication tolerances and cable losses. Comparative analysis further emphasizes the potential viability of the proposed MIMO antenna positioning it as a viable candidate for future compact-sized mm-wave MIMO systems.