Integration of MIMO and Cognitive Radio for Sub-6 GHz 5G Applications

Abstract

A multiple-input–multiple-output (MIMO) antenna system has been designed on a single substrate representing both types of cognitive radio (CR), i.e., interweave and underlay. The design consists of a four-port MIMO antenna for three selectable modes of the operation (modes). These modes are wideband antenna, frequency-tunable narrowband antenna, and wideband antenna with frequency-tunable band notch. The first, second, and third modes correspond to the sensing antenna, interweave CR communicating antenna, and underlay CR communicating antenna, respectively. These modes are achieved by incorporating multipurpose filters into the microstrip feedline part of the four antenna ports. The MIMO antenna system is designed for 5G applications in sub-6 GHz band (2.50–4.20 GHz). In wideband mode, the four-port MIMO antenna has a sensing frequency range of 2.00–5.70 GHz. While in the second mode of operation, it exhibits narrowband frequency tunability from 3.21 to 4.00 GHz. Finally, in the third mode of operation, the band-notch frequency of the antenna is tunable from 3.37 to 4.00 GHz. The complete structure was fabricated on Rogers RO4350 substrate, and the simulation results were verified by measurement.