# A large-scale MIMO antenna system for 5G IoT applications

## TL;DR

This paper presents a compact MIMO antenna system designed for 5G IoT applications with improved performance and small element spacing.

## Contribution

The paper introduces a novel decoupling method using microstrip lines and grounded stubs for MIMO antennas.

## Key findings

- The prototype achieved an impedance bandwidth from 4.78 to 4.81 GHz.
- Isolation better than 15 dB was achieved with small element spacing of 0.032λ and 0.026λ.
- The design supports scalability to large-scale 2 × N arrays for 5G IoT applications.

## Abstract

A multiple-input-multiple-output (MIMO) antenna system with low-profile and small element spacing characteristics is presented in this paper. This antenna contains multiple elements arranged in both E-plane and H-plane configurations. The original strong coupling between the MIMO elements can be suppressed by exciting orthogonal operating modes. To achieve this, a half-wavelength microstrip line and a quarter-wavelength grounded stub are utilized to decouple the H- and E-plane MIMO arrays. A 2 × 2 antenna prototype is fabricated and measured to demonstrate the decoupling concept’s feasibility. The measured impedance bandwidth is from 4.78 to 4.81 GHz. Across this band, the isolation is better than 15 dB with extremely small edge-to-edge distances of 0.032λ and 0.026λ in the E- and H-plane, respectively. Featuring the simple decoupling structure, small element spacing, and the capability of extending to a large-scale 2 × N array, the proposed antenna can be used for 5G Internet of Things (IoT) applications operating at the N79 frequency band.