Printed Closely Spaced Antennas Loaded by Linear Stubs in a MIMO Style for Portable Wireless Electronic Devices

Aqeel Ahmed Khan,Muhammad Asif,Muhammad Saeed Khan,Syed Aftab Naqvi,Ernesto Limiti,Mohammad Alibakhshikenari,Ali Lalbakhsh,Salahuddin Khan,Bilal Ijaz,Esraa Mousa Ali

doi:10.3390/electronics10222848

Abstract

An easy-to-manufacture and efficient four-port-printed Multiple Input Multiple Output (MIMO) antenna operating across an ultra-wideband (UWB) region (2.9–13.6 GHz) is proposed and investigated here. The phenomenon of the polarization diversity is used to improve the isolation between MIMO antenna elements by deploying four orthogonal antenna elements. The proposed printed antenna (40 × 40 × 1.524 mm3) is made compact by optimizing the circular-shaped radiating components via vertical stubs on top of the initial design to maximally reduce unwanted interaction while placing them together in proximity. The measurements of the prototype MIMO antennas corroborate the simulation performance. The findings are compared to the recent relevant works presented in the literature to show that the proposed antenna is suitable for UWB MIMO applications. The proposed printed UWB MIMO antenna could be a good fit for compact portable wireless electronic devices.

Highlights

The Federal Communication Commission (FCC) permitted the use of the ultrawideband (UWB) spectrum ranging from 3.1 GHz to 10.6 GHz for commercial applications [1,2,3]
A printed Multiple Input Multiple Output (MIMO) antenna is presented here that operates at a broad band of 10.7 GHz ranging from 2.9 to 13.6 GHz, including the FCC-designated UWB (3.1–10.6 GHz)
For the entire operating band, i.e., 2.9–13.6 GHz, mutual coupling between different antenna elements is less than −16 dB, and the reflection coefficient is less than −10 dB

Summary

Introduction

The Federal Communication Commission (FCC) permitted the use of the ultrawideband (UWB) spectrum ranging from 3.1 GHz to 10.6 GHz for commercial applications [1,2,3]. In [12], I-shaped grounded stubs are placed to achieve high isolation for a semi-circular shape MIMO antenna operating from 1.9 to 10.2 GHz, whereas the size of the reported antenna is 1750 mm, which is, in comparison, on the larger side Another large diversity antenna with a mushroom and electronic band gap (EBG) structure is proposed in [13]. The larger size of the radiating patch of a unit cell in [26] causes greater current flow and unwanted interaction between the adjacent elements of the proposed MIMO antenna This increases the mutual coupling and efficiency of the MIMO antenna.

Design of the Unit Cell for The MIMO Antenna

S-Parameters

Surface Current Density

Diversity Analysis

Findings

Conclusions