Four-Port Multiband MIMO Filtenna with an Isolation Filter for Sub-6 GHz 5G Applications

In this paper, a four-port multiple-input-multiple-output (MIMO) filtenna (antenna with filter) system with isolation enhancing band-reject filter (BRF) is presented. The filtenna system is designed by integrating a multi-functional filter (MFF) in the antenna’s feed line. The MFF has two modes of operation. In its 1^st mode, the filtenna system acts as a dualband antenna in the frequency range of 2.3-4.5 GHz and 5.3-5.5 GHz. While, in the 2^nd mode, it acts as a single band antenna in the frequency range 3.3-4.1 GHz. To improve the isolation between the antenna elements, an open stub line (OSL) based BRF has been incorporated in the ground plane of the filtenna system. The overall design is integrated into a Rogers RO 4003C substrate (εr=3.55, tanδ=0.0031) of dimension 100×65×1.52 mm³. The designed antenna system is suitable for sub-6 GHz fifth-generation (5G) systems.

I. Introduction

Increasing demand for high-speed data transmission along with better spectrum efficiency and reliability have made the multiple-input-multiple-output (MIMO) system one of the best choices of the fifth-generation (5G) communication system [1]. Implementing the 5G technology in the mm-wave frequency spectrum can give us enormous opportunities. However, 5G systems still suffer from propagation impairments, which mainly restrict the communication range. Hence, the sub-6 GHz band can be an excellent complement of the mm-wave spectrum [2].