Isolation Enhancement of Wide-Band MIMO Array Antennas Utilizing Resistive Loading

Jung-Dong Park,Muhibur Rahman,Hsiang Nerng Chen

doi:10.1109/access.2019.2923330

Jung-Dong Park, Muhibur Rahman + Show 1 more

Open Access

https://doi.org/10.1109/access.2019.2923330

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Abstract

In this paper, we propose the use of resistor-loaded paired parallel-coupled resonators (PCRs) for mutual coupling reduction and isolation enhancement in wideband MIMO array antennas. It was shown that the isolation enhancement using a conventional PCR structure was drastically degraded in the middle of the frequency band. By placing an optimally designed resistor between the PCRs, we can improve the isolation considerably, compared with the simple PCR structure. Moreover, it could also improve the diversity parameters, such as envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL). The validity of the proposed resistor-loaded PCR technique was verified with ultrawideband array antennas with 1 × 2 and 1 × 4 patch array configurations, achieving a 0.125λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> center-to-center spacing between narrowly spaced patches and isolation better than 25 dB within the range 3-9-GHz without any degradation in its frequency response, radiation patterns, or diversity parameters. The presented results confirm that the proposed technique is suitable in various MIMO systems applicable for wireless local area networks (WLANs), long-term evolution (LTE), and possibly fifth-generation (5G) communication due to the compact size and improved isolation performance.

Highlights

Multiple-input multiple-output (MIMO) is regarded as an efficient approach for modern telecommunication systems, including wireless local area networks (WLANs), long-term evolution (LTE), and possibly fifth-generation (5G) communication
It is understood that the coupling between two array patches or two wires in a MIMO system depends on their position relative to each other [2]
We investigated three essential figures of merit – the envelope correlation coefficient, diversity gain, and channel capacity loss [15]–[22] – to evaluate the antenna diversity performance of the reference antenna without any decoupling technique (Ant. 1), the antenna with conventional parallel-coupled resonators (PCRs) (Ant. 2), and the proposed antenna with resistor-loaded PCRs (Ant. 3)

Summary

INTRODUCTION

Multiple-input multiple-output (MIMO) is regarded as an efficient approach for modern telecommunication systems, including wireless local area networks (WLANs), long-term evolution (LTE), and possibly fifth-generation (5G) communication. The size issue related to the λ/2 structures was somehow resolved in [13] with the implementation of a novel miniaturized double-layer slit-patch EBG structure for closely spaced patch array elements It offers a simple fabrication process with a compact size, this technique is functional only with the frequency range of 3-6 GHz. Most recently in [21], a wide-band MIMO antenna was designed to reduce mutual coupling between array elements by inserting an inverted F-shaped stub between the array elements, leading to a low envelope correlation coefficient (ECC) and high diversity gain, leading to improved isolation.

ANTENNA CONFIGURATIONS

EVALUATION OF THE PROPOSED METHOD FOR ANTENNA DIVERSITY

ENVELOPE CORRELATION COEFFICIENT

MEASUREMENT OF THE FABRICATED ANTENNAS

COMPARISON WITH OTHER ISOLATION ENHANCEMENT METHODS

CONCLUSION