Design and measurement of a thirty-two-port MIMO/diversity antenna based on radiator-ground isomorphic inverse approach for intelligent vehicular internet of things communications

Abstract

The increased demand for automobile applications and connected-vehicles in the market has prompted much research into intelligent automotive antennas. Connected-vehicles are being used to change automotive technology and serve as a framework for a smart society. This paper presents a thirty-two-port hex‑polarized massive multiple-input-multiple-output (MIMO) antenna that operates at GPS, Wi-Fi, and ultra-wideband (UWB) frequencies. In the proposed MIMO antenna, thirty-two-unit cells are populated in 3D configuration, where eight-unit cells are arranged in the horizontal plane and twenty-four-unit cells are arranged in four different vertical planes. The unit cell, based on an isomorphic inverse approach, consists of a semi-circular radiator with integrated meandered slots and achieves a tri-band operation at 1.5 GHz, 2.4 GHz, and 3.1 to 11 GHz. The unit cell has a size of 20 mm × 20 mm and the developed MIMO architecture has dimensions of 85 mm × 85 mm. The peak gain of the proposed antenna is 3.85 dBi, and the efficiency is 89.5%. The MIMO antenna assembly exhibits a calculated Envelope Correlation Coefficient (ECC) using far-field, less than 0.1. The Total Active Reflection Coefficient (TARC) is found to be less than -10 dB and the difference of Mean Effective gain (MEG) is less than 1 dB. Also, Apparent Diversity Gain (ADG) and Effective Diversity Gain (EDG) by far-field method are found to be above 9 dB. Antenna assemblies like the one proposed, are filled in various layouts on 3D vehicular space to combat the diversity reception issues, catering to spatial and polarization needs. In order to substantially validate the designed MIMO antenna for vehicular applications, housing effects and on-car analysis have been studied.