MIMO microstrip antenna design and production for 5G applications

Abstract

Context—In recent years, the increasing need for communication due to technological advancements, along with the rise in the number of manufacturers and users, has made the transition to 5th generation (5G) communication systems necessary. This transition to 5G communication has placed new requirements on antenna designs, necessitating the development of antennas with high bandwidth, a low profile, and the ability to support multiple users simultaneously. This paper focused on increasing the bandwidth of multiple input multiple output (MIMO) microstrip antennas and improving the isolation between ports.Objective—This article describes the design and fabrication of a low-profile, high-bandwidth, dual-polarization, four-port, 1×2 array microstrip MIMO antenna for systems operating at 5G frequencies. The designed antenna is manufactured, and its measurement results are compared with simulation results. To enable the proposed design to operate in dual polarization, two ports were placed perpendicular to the edges of the patch antenna. The patches are designed in a square shape to ensure the antenna has linear polarization and exhibits equal characteristics in both horizontal and vertical polarizations. It is aimed at the MIMO antenna to operate at a minimum of 25 GHz - 26 GHz range, linearly in dual polarization, and to have better than -20 dB isolation between ports despite the placement of patch structures with a distance 0.25λ. To increase the antenna bandwidth and improve isolation between ports, the defected ground structure (DGS) method and neutralization line method are employed in the design. The antenna is 2.4 cm × 2.96 cm in size and has 4 ports, achieves a bandwidth of 2.33 GHz with 7 dBi gain at two ports for horizontal polarization, and a bandwidth of 3.5 GHz with 9.18 dBi gain at two ports for vertical polarization. Additionally, the targeted isolation values between ports in the 25 GHz - 26 GHz range are achieved to be better than -20 dB. The designed MIMO antenna is also evaluated in terms of important MIMO parameters such as diversity gain (DG), envelope correlation coefficient (ECC), total active reflection coefficient (TARC), and channel capacity loss (CCL).Method—In the designed antenna, an RT/duroid 5880 substrate with a dielectric constant (εr) of 2.2, a loss tangent (tan δ) of 0.0009, and a thickness of 0.787 mm has been used. A 1 oz (0.035 mm) thick layer of copper was used on both the bottom (grounding plane) and top (radiation area) surfaces of the dielectric material.Results—To minimize the antenna's footprint, the patch structures were placed at a distance 0.25λ apart, while ensuring that the isolation between the ports remains below -20 dB. The bandwidths of the 4-port antenna were measured as 3.89 GHz, 4.72 GHz, 4.35 GHz, and 3.8 GHz respectively. Consistency was observed between the data obtained from measurements and simulation results.Conclusion—CST Microwave Studio simulation software was used for design and simulations.