Multiband MIMO Microwave and Millimeter Antenna System Employing Dual-Function Tapered Slot Structure

Abstract

A single-layered multiple-input multiple-output (MIMO) antenna system is presented for future wireless devices operating at WLAN (2.45 GHz, 5.2 GHz), 4G LTE (2.6 GHz) and 5G (24 GHz, 28 GHz) bands. The design consists of a dual-band four-element monopole MIMO antenna system that covers the 2.45 GHz and 5.2 GHz bands. A decoupling mechanism is designed in the ground plane based on a tapered slot. This tapered slot has a dual function, working both as a decoupling structure (<inline-formula> <tex-math notation= LaTeX >$\\lambda _{0}/4$ </tex-math></inline-formula> long) at 2.45 GHz and as a tapered slot antenna (<inline-formula> <tex-math notation= LaTeX >$3\\lambda _{0}$ </tex-math></inline-formula> long) at 28 GHz when excited by a proper feeder. The proposed MIMO antenna system is designed on an RO-5880 substrate with overall dimensions of <inline-formula> <tex-math notation= LaTeX >$104$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation= LaTeX >$\\times 104$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation= LaTeX >$\\times 0.51$ </tex-math></inline-formula> mm. The measured results show that the presented design covers two low-frequency bands (from 2.40 GHz to 5.1 GHz, from 5.1 GHz to 5.6 GHz) with a peak gain of 5 dBi and one high-frequency band (from 23 GHz to 30 GHz) with a peak gain of 11 dBi. The minimum measured isolation between the two antennas is more than 16 dB, while the maximum envelope correlation coefficient value is less than 0.16 showing good MIMO characteristics.