  Citation: Ikram, M. 5G/B5G Internet of Things MIMO Antenna Design. Signals 2022, 3, 29–37. https:// doi.org/10.3390/signals3010003 Academic Editors: Yiming Huo and Minh Tu Hoang Received: 2 December 2021 Accepted: 4 January 2022 Published: 6 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). signals Article 5G/B5G Internet of Things MIMO Antenna Design Muhammad Ikram School of Information Technology and Electrical Engineering, University of Queensland (UQ), Brisbane 4072, Australia; Ikram439@gmail.com Abstract: The current and future wireless communication systems, WiFi, fourth generation (4G), fifth generation (5G), Beyond5G, and sixth generation (6G), are mixtures of many frequency spectrums. Thus, multi-functional common or shared aperture antenna modules, which operate at multiband frequency spectrums, are very desirable. This paper presents a multiple-input and multiple-output (MIMO) antenna design for the 5G/B5G Internet of Things (IoT). The proposed MIMO antenna is designed to operate at multiple bands, i.e., at 3.5 GHz, 3.6 GHz, and 3.7 GHz microwave Sub-6 GHz and 28 GHz mm-wave bands, by employing a single radiating aperture, which is based on a tapered slot antenna. As a proof of concept, multiple tapered slots are placed on the corner of the proposed prototype. With this configuration, multiple directive beams pointing in different directions have been achieved at both bands, which in turn provide uncorrelated channels in MIMO communication. A 3.5 dBi realized gain at 3.6 GHz and an 8 dBi realized gain at 28 GHz are achieved, showing that the proposed design is a suitable candidate for multiple wireless communication standards at Sub-6 GHz and mm-wave bands. The final MIMO structure is printed using PCB technology with an overall size of 120 × 60 × 10 mm 3 , which matches the dimensions of a modern mobile phone. Keywords: IoT; mm-wave; Sub-6 GHz; tapered slot; 5G 1. Introduction The exponential growth in data rates is an important aspect of modern research in mobile Internet of Things (IoT) communication. Substantial work has been done to improve the data rates and to fulfill ever-increasing requirements, such as 4G, 4G Long Term Evolution (LTE), and 5G [1–3]. However, data-hungry devices in IoT still need more and more data rates. Currently, 5G bands at Sub-6 GHz and mm-wave bands have been officially assigned by the Federal Communication Commission (FCC) to be used for 5G mobile communication to improve data rates [4]. Moreover, multiple-input multiple-out (MIMO) can further enhance data rates (channel capacity) by increasing the number of antennas [5–9]. One possible IoT-based communication scenario is shown in Figure 1, which demon- strates that in IoT communication, microwave Sub-6 GHz and mm-wave bands will be combined to access high data rates in large geographical coverage areas [10,11]. Therefore, in this work, the implementation of a Sub-6 and mm-wave MIMO antenna design is re- alized by utilizing the concept of a shared aperture antenna, as shown in Figure 1. The proposed design operates at the Sub-6 GHz band with wider antenna beamwidth and at the mm-wave band with a sharp directive antenna beam. The sharp directive beam with high gain is important in sending and receiving high-frequency signals at mm-wave bands. Additionally, high gain is required to mitigate high path loss at mm-wave bands [12,13]. Shared aperture or common aperture antennas have attracted considerable attention and interest recently. They have been proposed to operate at microwave Sub-6 GHz and mm-wave bands to satisfy the requirements of compact size, operating band, and directive radiation patterns at both bands [14–17]. To date, few designs have been presented that can simultaneously satisfy those requirements. In this article, a simple method for designing Signals 2022, 3, 29–37. https://doi.org/10.3390/signals3010003 https://www.mdpi.com/journal/signals